Final Report for SW01-056
Project Information
Tillage used to grow a barley-cotton double crop was reduced by eliminating tillage prior to planting cotton, eliminating cultivations for weed control in cotton, and especially by eliminating tillage following cotton. Small grain residues increased water infiltration into coarse-textured soils (but not on clay soils) and reduced irrigation advance times sometimes increasing the amount of water used to produce cotton. Weed-sensing automatic spot-spray technology reduced the amount of spray volume and herbicide used for cotton weed control. Conservation tillage and cotton-small grain double crop rotations were economically competitive with winter-fallow, conventional cotton production using extensive tillage.
The goal of this project is to provide cotton growers in the Southwestern United States with the necessary economic, agronomic, and physical information required to adopt conservation tillage practices, to utilize cover crops or double crop small grains with cotton, and to utilize weed-sensing sprayer technology. To achieve this goal, five objectives/performance targets have been established:
1. Evaluate the planting of cotton into cover-crop residues or into small grain crop stubble without preseason tillage.
2. Evaluate a weed-sensing sprayer and a post-emergence herbicide weed control program in minimum-till cotton.
3. Evaluate changes in soil properties such as organic matter content, crusting, water infiltration, and associated changes in fertility and irrigation practices.
4. Collect and compare operational, agronomic (i.e., plant growth), and cost data for minimum-till and conventional production systems.
5. Disseminate information on alternative production practices.
Conservation tillage is defined as a production system that eliminates or reduces tillage operations to the minimum required to produce a crop and in which 30% of the previous crop residue remains on the surface after planting (Bryson and Keeley, 1992). The presence of crop residue over time may increase soil organic matter content, improve soil tilth, and increase the moisture-holding capacity, cation exchange capacity and overall productivity of the soil (Boquet et al., 1997; Daniel et al., 1999; Smart and Bradford, 1999). Cotton farmers use disking and many other forms of mechanical soil disturbance each year (Bryson and Keeley, 1992) in conjunction with pre-emergence herbicides to prepare fields for cotton planting. After planting, mechanical cultivation is used for in-season weed control and maintenance of irrigation furrows.
Pre-emergence herbicides are applied in anticipation of weed populations, the densities of which cannot be easily determined beforehand. This practice wastes chemical and increases the pesticide load on the environment. Postemergence herbicides are generally applied either broadcast or in bands to entire fields regardless of the density or patchiness of the weed population, and they may not control weeds effectively in all situations. Froud-Williams (1988) reported increased occurrence and density of hard-to-control herbaceous perennial weeds and some highly specialized annuals and biennials after postemergence herbicide use in many no-till systems. Postemergence herbicides can be efficiently applied using chlorophyll/plant-sensing herbicide sprayers (Hanks and Beck, 1998). Hanks and Beck (1998) found that the amount of Roundup spray applied was reduced 63-85% by using the weed-sensing spray technology in conventional cotton. Since herbicide is sprayed only where weeds exist, higher rates of herbicides and more potent herbicide tank mixtures can be used without tremendously increasing cost.
Farmers consider cultivation or tillage to be necessary for aerating the soil and promoting plant growth, breaking the surface crust, breaking or penetrating hardpans, controlling weeds between rows, and maintaining furrows for efficient irrigation. Kaddah (1977) found that reduced-tillage cotton had higher yield and greater profits than conventional cotton, indicating that not all of the many tillage practices conducted in conventional systems are necessary for cotton production. Clay et al. (2000) and Husman et al. (2000) found that reduced-tillage practices could save money in ultra-narrow-row cotton production. Information is needed on sustainable conservation tillage cotton production practices that can reduce production costs, improve yields, and conserve the environment in Arizona and the southwest.
Cooperators
Research
At Fast Track Farms (cooperator: Greg Wuertz), the tillage/cover crop treatments in 2002 were: (1) conventional tillage/winter fallow followed by conventional cotton; (2) minimum tillage/oat cover crop, followed by no-till cotton planting; and (3) minimum tillage/Solum barley cover crop followed by no-till cotton planting. In 2003, the experiment was reconfigured and simplified to reduce the area of the experiment and the amount of water required in the fall of 2002. The tillage/cover crop treatments were: (1) winter fallow; conventional tillage cotton; (2) winter fallow; conventional tillage cotton with Telone nematicide soil injection; and (3) Solum barley cover crop; minimum tillage cotton planting. In 2004, the experiment was moved to a new site on the farm. It consisted of a paired comparison of (1) conventional tillage/winter fallow followed by conventional cotton; and (2) minimum tillage/Solum barley cover crop followed by no-till cotton planting. Prior to initiating the experiment in 2001, beds were listed with a hip-lister and mulched with a modified Sundance implement; a rotary hoe was used twice to prepare the final seedbed.
Coolidge Barley/Oat Cover Crops:
Solum barley and oat cover crops were planted at 111 and 71 lb/A seeding rate, respectively, on 19 November 2001. A Case IH 5400 grain drill was used for planting the cover crops. It was irrigated once with 12 acre-in/A of water during the winter. The cover crops were sprayed with glyphosate at a rate of 1.12 lb ae/A (40 oz/A of Roundup Ultramax) on 5 March 2002 with a John Deere 6000 Hi-Cycle to kill the plants prior to planting cotton. In the second season of the experiment, Solum barley cover crop was planted into existing beds in the reduced tillage plots at a seeding rate of 111 lb/A on 6 December 2002 using a John Deere 1560 no-till grain drill. It was irrigated twice, at 5 and 4.5 ac-in/A, respectively. The cover crop was terminated with glyphosate at 1.85 lb ae/A (Roundup UltraMax at 64 oz/A) on 8 March, 2003. In fall 2003, Solum barley cover crop was planted on 80-in beds at 111 lb/A seeding rate using a John Deere 1560 grain drill on 15 December 2003 and irrigated (12 acre-in/A). Conventional tillage was used to prepare the 80-in beds following cotton harvest and shredding. The barley cover crop was terminated in March 2004 using glyphosate at 1.13 lb ae/A. Cover crop biomass was always assessed from four randomly placed 0.5-m2 qaudrats per plot.
Coolidge 2002 Cotton Crop:
Cotton cultivar DeltaPine 422 BR was dry-planted at a 50,000 seed/A seeding rate in the winter fallow, conventional tillage plots using a John Deere MaxEmerge II planter on 19 April 2002 and irrigated to germinate the seed on 25 April 2002. Yetter Farm Equipment 2976 residue manager/coulter assemblies were bolted onto the planter units in order to plant the cotton in the barley and oat cover crop residues. It was irrigated eight times at a total of 76.5 acre-in (conservation tillage cotton) and 55.5 acre-in (conventional tillage cotton). Aerial applications of Kelthane (1.3 pt/A), Warrior + Orthene (3.7 oz/A + 1 lb/A) and Warrior + Lorsban (3.9 oz/A + 1.4 pt/A) were made for insect control on 14 June 2002, 2 August 2002 and 15 August 2002, respectively. The crop received three fertilizer applications: 10-43-0 at 20 gal/A on 3 June 2002, UN-32 at 15 gal/A on 21 June 2002 and UN-32 at 20 gal/A on 19 July 2002. Cotton establishment and growth was assessed in the various treatments by counting the number of emerged plants and measuring plant height and counting the number of nodes per plant at various times during the cotton season in both conventional tillage treatments and reduced tillage treatments. Ginstar at 7 oz/A and CottonQuick at 17 oz/A were applied on 19 September to defoliate the cotton. The cotton was harvested on 28 October 2002. Twelve rows of cotton were picked using a John Deere 9976 6-row picker, and the seedcotton was weighed in Caldwell Boll Buggy (EL Caldwell and Sons, Inc.) equipped with a Weigh-Tronix scale (Model WI-152). The seedcotton was ginned with a 25-saw cotton gin.
Coolidge 2002 Cotton Weed Control:
A proposed pre-emergence Prowl (pendimethalin) application was not made at this and the other sites because the large amount of cereal cover crop residues and grain crop stubble present in the conservation tillage plots was perceived to be sufficient to bind and inactivate the herbicide before it could reach the soil surface, be incorporated, and provide weed control. Thus, weed control in all conservation tillage treatments at all sites was obtained using only postemergence herbicides, while cultivation and pre-emergence herbicides were used in the conventional tillage treatments.
A topical, broadcast application of glyphosate at 1 lb ae/A (Roundup UltraMax at 34.7 oz/A) was made on all plots on 14 May 2002, when the cotton crop was at the 4 true leaf stage. The winter fallow, conventional tillage cotton treatment was cultivated on 27 May 2002, 18 June 2002 and 2 July 2002, using a rolling cultivator, and on 15 July 2002 using a rod weeder. On 20 June 2002, the furrows in the conservation tillage plots were sprayed using a 6-row sprayer equipped with five 28-in and two 20-in Redball conservation tillage spray hoods equipped with three or two 95-degree even flat fan nozzles, respectively. Two of the 28-in spray hoods were modified by installing three WeedSeeker weed-sensing, intermittent spray units (NTech Industries, Inc.) each with a single 6503 flat fan nozzle in each hood to selectively detect and automatically spot-treat weeds in the furrows. This allowed comparison of the WeedSeeker spray units with the conventional continuous spray nozzles in other hoods in terms of spray volume applied and control of predominant weeds. The spray hoods had two (28-in hoods) or one (20-in hoods) 80-degree flat fan nozzles on single swivels mounted at the rear of the hoods to post-direct spray at the base of the cotton plants in the seed line. Glyphosate at 1.5 lb ae/A (Roundup UltraMax at 52 oz/A) + ammonium sulfate (AMS) at 2% w/w was applied with the WeedSeeker and conventional spray hoods in the minimum tillage plots, and glyphosate at 0.75 lb ae/A (Roundup UltraMax at 26 oz/A) + AMS at 2% was simultaneously applied post-direct to the base of the cotton plants.
On 16 July 2002, three different herbicide regimes were applied each under conventional and WeedSeeker spray unit hoods in subplots of the minimum tillage plots. All three treatments contained glyphosate at 1.5 lb ae/A (Roundup UltraMax at 52 oz/A) + AMS at 2% w/w, with either prometryn at 0.8 lb ai/A (Prometryne at 5.9 oz/A), carfentrazone-ethyl at 0.016 lb ai/A (Aim at 1 oz/A), or carfentrazone-ethyl at 0.025 lb ai/A (Aim at 1.6 oz/A). In all subplot treatments, glyphosate at 0.75 lb ae/A (Roundup UltraMax at 26 oz/A) + AMS at 1% w/w was applied post-direct to the base of the cotton plants. A layby application of glyphosate at 0.7 lb ae/A (Roundup UltraMax at 24 oz/A) + prometryn at 0.75 lb ai/A (Cotton-Pro at 24 oz/A) was made in all plots on 29 July 2002 using a Redball 420 layby sprayer.
Coolidge 2003 Cotton Crop:
Telone EC was applied by injection at 5 gal/A in one of the two conventional tillage plots. Cotton cultivar DeltaPine 449 BG/RR was planted directly into barley cover crop residues at a 11 lb/A seeding rate using a standard John Deere MaxEmerge II 6-row planter equipped with Yetter Farm Equipment 2976 residue manager/coulter assemblies. The Yetter 2976 residue managers did a good job of moving residue and cutting a seed line with a fluted coulter resulting in good seed placement in the dry beds. The Yetter 2967 residue manager/coulters easily shattered and moved the old shredded cotton stalks remaining from the 2002 cotton season in addition to the barley residues. As in the 2002 cotton crop, cotton establishment and growth was assessed in the various treatments by counting the number of emerged plants and measuring plant height and counting the number of nodes per plant at various times during the cotton season in both conventional tillage treatments and reduced tillage treatments. The cotton was harvested on 3 October 2003 and the seedcotton was ginned as in the 2002 cotton.
Coolidge 2003 Cotton Weed Control: A pre-plant application of pendimethalin (Prowl 3.3 EC at 48 oz/A) was made in the conventional tillage plots on 3 March 2003, and in the minimum tillage plots on 31 March 2003. The minimum tillage plots were mini-tilled on 31 March and 8 April 2003 using a Sundance disk/bedder. The conventional plots were cultivated twice in April and once in May. A topical, broadcast application of glyphosate (Roundup UltraMax at 40 oz/A) + AMS at 1% w/w was made in the minimum tillage plots, and at 32 oz/A + AMS at 1% w/w in the conventional tillage plots on 30 April 2003. On 30 May 2003, glyphosate (Roundup UltraMax at 26 oz/A) + AMS at 2% w/w was post-directed to the base of cotton plants, and glyphosate (Roundup UltraMax at 52 oz/A) + AMS at 2% w/w was applied under Redball 410 conservation tillage hoods in the minimum tillage plots. In the conventional tillage plots, an application of glyphosate (Roundup UltraMax at 24 oz/A) + pyrithiobac sodium (Staple at 1.9 oz/A) was made using a Redball 420 hooded sprayer. A layby herbicide application was made in the minimum tillage plots on 16 June 2003 using the Redball 410 hooded sprayer. Glyphosate (Roundup UltraMax at 26 oz/A) + AMS at 1% w/w was post-directed to the base of cotton plants; glyphosate (Roundup UltraMax at 52 oz/A) + AMS at 1% w/w was applied under hoods. Prometryn (Prometryne 4F at 25 oz/A) + pendimethalin (Prowl 3.3 EC at 32 oz/A) was applied under hoods in the conventional tillage plots on 26 June 2003.
Coolidge 2004 Cotton Crop:
Telone II at 5 gal/A and Temik at 4.7 lb/A were applied in both treatments prior to cotton planting. Cotton cultivar DP 449 BR was dry planted in the conventional tillage treatment on 19 April 2004, and into barley cover crop residues in the no-till treatment on 20 April 2004 at a 10-lb/A seeding rate. The MaxEmerge II planter described above without the Yetter attachments was used. The cotton was harvested on 17 November 2003. Twelve rows of cotton were picked using a John Deere 9976 6-row picker, and the seedcotton was weighed and ginned as described above.
Coolidge 2004 Cotton Weed Control:
A preplant incorporated application of pendimethalin (Prowl at 48 oz/A) was made in then conventional tillage treatment on 1 April 2004. Glyphosate (Roundup UltraMax at 32 oz/A) was applied topically in the conventional tillage treatment on 13 May 2003, and at 40 oz/A + AMS at 1% w/w in the conservation tillage on 20 May 2004. Pyrithiobac sodium (Staple at 1.8 oz/A) was applied in the conventional tillage treatment on 21 June 2004. In the conservation tillage treatment, glyphosate (Roundup WeatherMax at 32 oz/A) + AMS at 1% w/w was applied under hoods of the Redball conservation tillage sprayer, while glyphosate (Roundup WeatherMax at 22 oz/A) + AMS at 1% w/w was applied post-directed to the base of cotton plants on 22 June 2004. On July 16 2004, a layby application of prometryn (Cotton Pro at 32 oz/A) was made in the conventional tillage treatment; prometryn (Prometryne at 32 oz/A) + carfentrazone-ethyl (Aim at 1 oz/A) was applied in the conservation tillage treatment.
Treatments at the Marana Agricultural Center in 2002 were: (1) winter fallow, conventional tillage cotton planting in April (early planting); (2) winter fallow, conventional tillage cotton planting in late May (late planting); (3) Solum barley cover crop, no-till cotton planting in April (early planting) (there were three subplots: one brittle stem barley subplot and two Solum barley subplots); (4) Solum barley grain crop, no-till cotton planting in May (late planting). Field preparation consisted of ripping (twice), disking (twice), disking (twice) after spreading fertilizer, listing beds, and cultipacking. Beds in the conventional tillage treatments were re-disked and re-listed before cotton was planted on them. In 2003, the conventional tillage plots were deep-ripped, disked, and listed; in 2004, they were disked, deep-ripped, re-disked, and listed. In both 2003 and 2004, only one barley (Solum) cover crop was planted in place of the three barley subplots in the Solum barley cover crop, no-till cotton planting in April (early planting) treatment.
Marana Barley Cover and Grain Crops: The barley cover and grain crops were planted at a 72 lb/A seeding rate, and were irrigated once and twice and during the winter and spring, respectively. The cover crops were sprayed with glyphosate at 1.12 lb ae/A (40 oz/A Roundup UltraMax) plus 2% w/w AMS (ammonium sulfate) using a 6-row boom sprayer on 1 March 2002. The Solum barley grain crop was harvested with a 10-ft header conventional grain combine (Gleaners Baldwin Allis Chalmers) on 3 May 2002. Following the 2002 cotton harvest, the Solum barley cover and grain crops were planted into shredded cotton stalks at a 51 lb/A seeding rate using a John Deere 1560 grain drill on 11 December 2002. The cover crop was terminated with glyphosate at 1.12 lb ae/A (40 oz/A Roundup UltraMax) plus 2% w/w AMS using a 4-row boom sprayer on 14 March 2003. The Solum barley grain crop was harvested with the grain harvester described above on 16 May 2003. After the previous season's cotton had been shredded about 6 in above the ground, Solum barley was planted on the existing beds using a 10-ft wide John Deere 1560 no-till grain drill at a seeding rate of 51 lb/A on 9 December 2003. The barley cover crop was killed using 1.17 lb ae glyphosate/A (40 oz/A) of Roundup UltraMax (glyphosate) plus 2% w/w AMS applied on 26 March 2004 with a 6-row boom sprayer. The grain crop grown at Marana was harvested with a conventional grain combine (Gleaners Baldwin Allis Chalmers) on 14 May 2004.
Marana 2002 Cotton Crop:
Cotton cultivar DeltaPine 422 BR was planted in the early planted treatments at a 12.6 lb/A seeding rate in the fallow treatment and at a 14 lb/A seeding rate in the conservation tillage treatment on 17 April 2002, and on 3 May 2002 in the late planted treatments at a 12.6 lb/A seeding rate in the fallow treatment and at a 14 lb/A seeding rate in the conservation tillage treatment. A standard 4-row John Deere MaxEmerge planter was used in the conventional tillage plots for both early and late planting. Four Yetter Farm Equipment 2976 residue manager/coulter assemblies were bolted to the planter units and the same planter was used to plant the no-till cotton treatments. In the fine-textured soil at Marana which was hard when dry, the MaxEmerge planter was not heavy enough to force the residue manager-coulter-planter assembly units into the dry stale beds. Thus, it was necessary to add about 200 lb to each planter unit to accomplish satisfactory penetration of the soil and placement of the cotton seed. The early and late no-till cotton was planted into dry soil to a depth of about 0.5 in and irrigated after planting ("dry planted"); the winter fallow-conventional tillage treatments were pre-irrigated and the cotton was planted to moisture with a dry soil mulch placed of the seed line that was removed about 5 days after planting ("wet-planted"). The early-planted cotton was harvested on 16 October 2002, and the late-planted cotton was harvested on 30 October, 2002. The eight center cotton rows of each plot were picked with a John Deere 9910 2-row picker. The seed-cotton was weighed in a Caldwell Boll Buggy (E.L. Caldwell and Sons, Inc.) equipped with a Weigh-Tronix scale (model WI-152) and ginned with a 25-saw gin.
Marana 2002 Cotton Weed Control:
As noted above for the Coolidge site, a proposed pre-emergence Prowl (pendimethalin) application was not made because of the large amount of barley residues and stubble present in the conservation tillage plots. Thus, weed control in all conservation tillage treatments was obtained using postemergence herbicides, while pre-emergence herbicides [pendimethalin 0.72 lb ai/A (Prowl 28 oz/A) and prometryn 0.88 lb ai/A (Prometryne 28 oz/A)], four cultivation operations (4 June 2002, 12 June 2002, 3 July, 2002, and 15 July, 2002), and hand weeding were used in the conventional tillage treatments. A topical, broadcast application of glyphosate at 0.75 lb ae/A (Roundup UltraMax at 26 oz/A) + AMS at 2% w/w was made in the minimum tillage/barley cover crop-early cotton treatment on 8 May, 2002; the application was repeated on 29 May, 2002 in the two no-till treatments. On 27 June 2002, glyphosate 0.75 lb ae/A + AMS at 2% w/w was applied post-directed to the cotton seed line and glyphosate 1.5 lb ae/A + AMS at 2% w/w was applied under RedBall Conservation Spray-Hoods using the sprayer described above in Coolidge. Two of the spray hoods were removed and the others moved to accommodate the 4-row planter configuration at Marana. As noted above, two of the spray hoods contained WeedSeeker intermittent spray units (NTech Industries, Inc.). On 15 July 2002, a layby application of glyphosate (0.75 lb ae/A) + Prometryne at 1.6 lb ai/A + AMS at 1% w/w was made in all treatments.
Marana 2003 Cotton Crop:
Cotton var. DeltaPine 449 BR at a 10.8 lb/A seeding rate was dry-planted in the winter fallow, conventional tillage early plant cotton, and the Solum barley cover crop, no-till early plant cotton treatments on 23 April 2003. DeltaPine 458 BR was planted at a 10.8 lb/A seeding rate in the winter fallow, conventional tillage late plant cotton and the Solum barley grain crop, no-till late plant cotton treatments on 16 May 2003. Both conventional tillage early and late plant cotton was planted with a standard John Deere 7100 MaxEmerge 4-row planter. A Yetter Farm Equipment 2976 residue manager/coulter assembly was bolted to each planter unit and an additional 200 lb weight was added to each unit to plant in the no-till plots. The experiment was harvested on 30 October 2003 using John Deere 9910 and 9930 2-row pickers. The seed-cotton was weighed in a Caldwell Boll Buggy (E.L. Caldwell and Sons, Inc.) equipped with a Weigh-Tronix scale (model WI-152) and ginned with a 25-saw gin.
Marana 2003 Cotton Weed Control: A pre-plant incorporated application of prometryn (CottonPro at 56 oz/A) + pendimethalin (Prowl at 28 oz/A) was made in the conventional tillage plots on 24 March 2003. A post-direct application was made in the early planted cotton on 2 June 2003. Glyphosate (Roundup UltraMax at 26 oz/A) + AMS at 1% w/w was directed to the base of cotton plants; glyphosate (Roundup UltraMax at 52 oz/A) + carfentrazone-ethyl (Aim at 0.008 lb a.i./A) AMS at 2% w/w was applied under hoods using the Redball conservation tillage sprayer described above. On 10 June 2003, a topical application of glyphosate (Roundup UltraMax at 40 oz/A) + AMS at 2% w/w was made in the late planted cotton at the 3-4 leaf stage. Morning glory plants that obviously escaped the topical herbicide application were hand-hoed in the late planted no-till cotton on 20 June 2003. Another post-directed application was made in the early planted cotton on 3 July 2003: glyphosate (Touchdown at 0.75 lb a.i./A) + prometryn (Prometryne at 0.5 lb a.i./A) + AMS at 2% w/w was post directed to the base of cotton plants, and glyphosate (Touchdown at 0.75 lb a.i./A) + carfentrazone-ethyl (Aim at 0.016 lb a.i./A) + AMS at 2% w/w was applied under Redball conservation tillage hoods. A layby application of glyphosate (Touchdown at 0.75 lb a.i./A) + carfentrazone-ethyl (Aim at 0.016 lb a.i./A0 + prometryn (Prometryne at 1.2 lb a.i./A) + AMS at 1% w/w + Herbimax at 1% v/v was made in all treatments on 5 August 2003.
Marana 2004 Cotton Crop:
The conventional tillage treatments were disked, deep-ripped twice, re-disked, re-listed to re-form beds, and mechanically mulched before cotton was planted in the spring of 2004. The conventionally tilled early plant treatment was pre-irrigated before cotton planting. Cotton cultivar DeltaPine 449 BR was planted at a seeding rate of 14 lb/A in the early planted treatments on 16 April 2004; on 14 May 2004, cotton cultivar DeltaPine 451 BR was planted at a seeding rate of 11 lb/A in the late planted treatments. A 4-row, John Deere 7100 MaxEmerge planter was used in the conventional tillage plots for both early and late plantings. Four Yetter Farm Equipment 2976 residue manager/coulter assemblies were bolted to the planter units for planting in the no-till cotton treatments. In the fine-textured soil at Marana, which was hard when dry, the MaxEmerge planter was not heavy enough to force the residue manager-coulter-planter units into the dry stale beds. Thus, it was necessary to add 200 lb to each planter unit to accomplish satisfactory soil penetration and placement of the cotton seed. The treatments were harvested on 30 October 2004 using John Deere 9910 and 9930 2-row pickers. The seed-cotton was weighed in a Caldwell Boll Buggy (E.L. Caldwell and Sons, Inc.) equipped with a Weigh-Tronix scale (model WI-152) and ginned with a 25-saw gin.
Marana 2004 Cotton Weed Control:
Weed control in 2004 in all conservation tillage treatments was obtained using a pre-plant application of pendimethalin (Prowl 3.3 EC @ 1.75 qt/A) + prometryn (CottonPro 4F @ 1.75 pt/A) and post-emergence glyphosate-based applications; in the no-till treatments, only post-emergence glyphosate-based applications were used. A topical, broadcast application of glyphosate (Roundup WeatherMax @ 32 oz/A) + AMS @ 1% w/w was made on 10 May 2004 in the early planted treatments. On 6 July 2004, a post-directed application of glyphosate (Roundup WeatherMax @ 22 oz/A) + AMS @ 1% w/w was directed to the base of cotton plants in all four treatments. Glyphosate (Roundup WeatherMax @ 22 oz/A) + AMS @ 1% w/w was applied in the late-planted no-till cotton treatment and glyphosate (Roundup WeatherMax @ 22 oz/A) + carfentrazone-ethyl (Aim @ 1 oz/A) + AMS @ 1% w/w was applied in the early planted no-till cotton treatment, using the RedBall 410 Conservation Tillage spray hoods described above. A layby application of carfentrazone-ethyl (Aim @ 2 oz/A) + prometryn (CottonPro 4F @ 1.75 pts/A) was made in all four treatments on 27 July 2004 using a Redball 420 layby sprayer.
The barley cover and grain crop, cotton double crop experiment at the Maricopa Agricultural Center was conducted in large plots 12 rows wide (40 feet) by 600 feet long. The treatments were were: (1) winter fallow, conventional tillage cotton planting in April (early planting); (2) winter fallow, conventional tillage cotton planting in late May (late planting); (3) Solum barley cover crop, no-till cotton planting in April (early planting); (4) Solum barley grain crop, no-till cotton planting in May (late planting). Initial field preparation consisted of disking, landplaning, listing after spreading fertilizer, and roto-mulching before barley was planted. Beds in the conventional tillage treatments were re-disked and re-listed (twice) and bed-shaped (twice) before cotton was planted on them. A straw management study was also initiated at the Maricopa Ag. Center in fall 2002 in small plots (4 rows [13.33 feet] by 40 feet) and included the following treatments: (1) winter fallow, conventional tillage cotton; (2) a green-chopped Beardless barley cover crop, no-till cotton; (3) green-chopped Cayuse oat cover crop, no-till cotton; (4) Solum barley grain crop with straw baled, no-till cotton; (5) Solum barley grain crop, cut low (stem stubble 5 inches tall from bed top), no-till cotton; (6) Solum barley grain crop, cut at medium height (stems 9 to 10 inches tall), no-till cotton; (7) Solum barley grain crop, cut high (stems 17 to 18 inches tall), no-till cotton.
Maricopa Barley Cover and Grain Crops:
Solum barley cover and grain crops were planted on 12 December 2002 at a seeding rate of 100 and 25 lb/A, respectively using a John Deere 8200 4-row grain drill. Two irrigations were applied at 4.5 and 2.19 ac-in/A in February and March, respectively. The cover crop was terminated with glyphosate at 1.52 lb ae/A (Roundup UltraMax at 52 oz/A) plus 2% AMS applied on 15 March 2003. The grain crop was harvested using Case International Harvester 1440 axial-flow combine with a 20-ft header and the grain was weighed in a Parker 1555 weigh cart equipped with a Weigh-Tronix model 715 scale on 21 May 2003. Following the 2003 cotton harvest, Solum barley was planted on 8 December 2004 into shredded cotton stalks at a seeding rate of 51 lb/A using the John Deere 1560 no-till grain drill as described for the Marana experiment. The barley cover crops were killed using 1.17 lb ae glyphosate/A (40 oz/A of Roundup UltraMax) plus 2% AMS applied on 15 March 2004 as described above. The grain crop at Maricopa was harvested with a Case International Harvester 1440 on 3 May 2004.
Maricopa 2003 Cotton Crop:
Cotton var. DeltaPine 449 BR was planted in the early planted cotton treatments at 11.8 lb/A seeding rate on 21 April 2003. Cotton var. DP 458 BR was planted in the late planted cotton treatments at a 10.8 lb/A seeding rate on 21 May 2003. The conventional tillage treatments were planted with a standard John Deere 7100 4-row planter. Yetter Farm Equipment 2976 residue manager/coulter assemblies were attached to the planter units to plant cotton in the no-till treatments. The experiment was harvested on 24 October 2003. The eight center rows of each plot were picked with a Case IH 2155 4-row cotton picker. The seed-cotton was weighed and ginned as described for the Marana experiment.
Maricopa 2003 Cotton Weed Control:
Only postemergence, glyphosate-based herbicide applications were made in the no-till plots. However, a pre-plant application of Prowl 3.3 EC at 2 pt/A, postemergence, glyphosate-based postermergence herbicide applications and three cultivations were made for weed control in the conventional tillage plots. A topical, broadcast application of glyphosate (Roundup UltraMax at 26 oz/A) + 1% w/w AMS was made in the early planted cotton treatments on 23 May 2003. A post-directed application of glyphosate (Touchdown at 0.75 lb ae/A) + prometryn (Caparol at 0.5 lb ai/A) + 1% w/w AMS was directed to the base of the cotton plants simultaneously with glyphosate (Touchdown at 0.75 lb ae/A) + carfentrazone-ethyl (Aim at 0.016 lb ai/A) + 1% w/w AMS sprayed under RedBall Conservation Tillage spray hoods in the Solum barley cover crop followed by early planted no-till cotton treatment on 11 June 2003, as described for the Marana experiment. Glyphosate (Touchdown at 0.75 lb ae/A) + prometryn (Caparol at 0.5 lb ai/A) + 1% w/w AMS was directed to the base of the cotton plants in the winter fallow conventionally tilled cotton treatments on 11 June 2003. Also on 11 June 2003, a topical, broadcast application of glyphosate (Roundup UltraMax at 40 oz/A) + 1% w/w AMS w/w was made in the late planted cotton treatments. The post-directed herbicide applications made in the early planted cotton treatments on 11 June 2003 were repeated in the late planted cotton treatments on 8 July 2003. On 25 July 2003, a layby application of glyphosate (Touchdown at 0.75 lb ae/A) + prometryn (Caparol at 1.2 lb ai/A) + 1% w/w AMS was applied to base of the cotton plants and glyphosate (Touchdown at 0.75 lb ae/A) + carfentrazone-ethyl (Aim at 0.016 lb ai/A) + prometryn (Caparol at 1.2 lb ai/A) + 2% w/w AMS was applied under RedBall Conservation Tillage spray hoods in the Solum barley cover crop followed by early planted no-till cotton treatment. Glyphosate (Touchdown at 0.75 lb ae/A) + prometryn (Caparol at 1.2 lb ai/A) + AMS at 2% w/w was applied to base of the cotton plants in the winter fallow conventionally tilled cotton treatment. The layby herbicide applications were repeated in the late planted cotton treatments on 7 August 2003.
Maricopa 2004 Cotton Crop:
Shredded cotton stalks on conventionally tilled plots were root-pulled and plots were disked twice; beds were listed, mulched, shaped, and ring-rolled before cotton planting. Cotton var. DeltaPine 449 BR was planted in the early planted conventional tillage and the early planted no-till cotton treatments at 14 lb/A seeding rate on 9 April 2004. Cotton var. DP 449 BR was planted in the late planted conventional tillage and the late planted no-till cotton treatments at a 14 lb/A seeding rate on 4 May 2004. The conventional tillage treatments were planted with a standard John Deere 7100 4-row planter. Yetter Farm Equipment 2976 residue manager/coulter assemblies and additional 100-lb weights were attached to the planter units to plant cotton in the no-till treatments. The experiment was harvested on 20 October 2004. The eight center rows of each plot were picked with a Case IH 2155 4-row cotton picker. The seed-cotton was weighed and ginned as described for the Marana experiment.
Maricopa 2004 Cotton Weed Control:
A pre-plant application of pendimethalin (Prowl 3.3 EC at 2 pt/A), one post-emergence glyphosate herbicide application and one cultivation were used for weed control in the conventional tillage treatments. In contrast, only post-emergence, glyphosate applications were made in the no-till cotton plots. Glyphosate (Roundup WeatherMax at 22 oz/A) + 1% w/w AMS were applied topically in the early planted cotton treatments on 4 May 2004. A post-directed application of glyphosate (Roundup WeatherMax at 22 oz/A) + 1% w/w AMS was directed to the base of cotton plants, and glyphosate (Roundup WeatherMax at 32 oz/A) + 1% w/w AMS was sprayed under Redball Conservation Tillage spray hoods in the early planted no-till cotton treatment on 24 June 2004. On the same date, glyphosate (Roundup WeatherMax at 22 oz/A) + 1% w/w AMS was directed to the base of cotton plants in the early planted conventional tillage cotton treatment. On 25 May 2004, a topical, broadcast application of glyphosate (Roundup WeatherMax at 32 oz/A) + 1% w/w AMS was made in the late planted cotton treatments. The post-directed application made in the early planted cotton treatments was repeated in the late planted cotton treatments on 24 June 2004. There was no layby herbicide application in this experiment.
Maricopa Straw Management Experiment – 2003:
The Solum barley grain crops and the Beardless barley and Cayuse oat cover crops were planted and irrigated similarly on 12 December 2002 as described above for the Maricopa 2003 barley cover and grain crops. The cover crops were green-chopped and dry weight samples were collected on 14 April 2003. The cover crop samples were collected from four 0.25 m2 sample areas in each plot and were later oven-dried at 150 F for dry weight assessments. Solum barley grain crop biomass was sampled from four 1.24 m2 sample areas immediately prior to grain harvest; the biomass was dry at the time of sampling. The Solum barley grain crop treatments were harvested at the desired straw heights with the Case International Harvester 1440 axial-flow combine described above and weighed in the Parker 1555 weigh cart on 21 May 2003. Cotton var. DP 458 BR was planted at a 10.8 lb/A seeding rate on 21 May 2003 into Solum barley grain crop stalks or on beds from which beardless barley and Cayuse oat cover crops had been green-chopped. There was very little cover crop residue in the green-chopped plots. A standard John Deere 7100 4-row planter with Yetter Farm Equipment 2976 residue manager/coulter assemblies was used to plant the cotton in all the treatments. Glyphosate (Roundup UltraMax at 40 oz/A) + 1% w/w AMS was applied topically 13 June 2003. A post-directed application of glyphosate (Touchdown at 0.75 lb a.i./A) + prometryn (Caparol at 0.5 lb a.i./A) + AMS at 1% w/w was directed to the base of cotton plants, and glyphosate (Touchdown at 0.75 lb a.i./A) + carfentrazone-ethyl (Aim at 0.016 lb a.i./A) +1% w/w AMS was sprayed under Redball Conservation Tillage spray hoods on 8 July 2003. The same treatments with a higher rate of prometryn (Caparol at 1.2 lb a.i./A) were applied as layby application on 7 August 2003. The experiment was harvested on 27 October 2003. The four center rows of each plot were picked with a Case IH 2155 4-row cotton picker. The seed-cotton was weighed and ginned as described for the other Maricopa experiment.
Maricopa Straw Management Experiment – 2004:
After the previous season’s cotton had been shredded as in the above experiments, Solum barley grain crop was planted at 51 lb/A seeding rate on 8 December 2003 using the John Deere 1560 no-till grain drill as described above; Beardless barley and Cayuse oat cover crops were planted at 108 lb/A using the same method as for Solum barley. Cover crop samples were collected as in the 2003 experiment on 15 March 2004. The cover crops were green-chopped on 19 March 2004. Solum barley grain crop biomass was sampled as in the 2003 experiment above immediately prior to grain harvest. The Solum barley grain crop treatments were harvested at the desired straw heights on 3 May 2004. Cotton in the conventional tillage treatment was root-pulled and plots were disked twice; beds were listed, mulched, shaped, and ring-rolled before cotton planting, as in the other Maricopa experiment above. Cotton var. DP 449 BR was planted in all treatments at a 14 lb/A seeding rate on 4 May 2004. The conventional tillage treatment was planted with a standard John Deere 7100 4-row planter. Yetter Farm Equipment 2976 residue manager/coulter assemblies and additional 200-lb weights, as used in the Marana experiment, were attached to the planter units to plant cotton in the no-till treatments. Cotton stand counts, plant heights and height-to-node ratios were assessed as in the other experiments above; the position of the first fruiting branch and of the first sustained boll were also assessed. Glyphosate (Roundup WeatherMax @ 22 oz/A) + 1% w/w AMS were applied topically in the two cover crop treatments to kill beardless barley and Cayuse oat ratoons on 4 May 2004 immediately following cotton planting. A topical, broadcast application of glyphosate (Roundup WeatherMax at 22 oz/A) + 1% AMS was made in all treatments on 25 May 2004. On 24 June 2004, glyphosate (Roundup WeatherMax at 22 oz/A) + 1% w/w AMS was directed to the base of cotton plants in all treatments, while glyphosate (Roundup WeatherMax at 32 oz/A) + 1% w/w AMS was applied under Redball Conservation tillage spray hoods in the conservation tillage treatments. The four center rows of each plot were picked with a Case IH 2155 4-row cotton picker. The seed-cotton was weighed and ginned as described for the other Maricopa experiment.
Treatments at A Tumbling T Ranch (cooperator: Ron Rayner) were: (1) fall no-till planting of a Poco barley grain crop followed by a spring no-till planting of cotton; (2) fall minimum tillage prior to planting a Poco barley grain crop followed by a spring no-till planting of cotton; and (3) fall minimum tillage prior to planting a Poco barley grain crop followed by minimum tillage prior to planting cotton in the spring. The Poco barley grain crop was planted on 26 December 2001. Minimum tillage at Goodyear consisted of disking the plots twice. There were no operational differences between treatments following the 2002 cotton season because the entire field was disked prior to planting grain in fall 2002 and was ripped, disked, and laser-leveled prior to planting cotton in 2003.
Goodyear Grain Crops:
The Poco barley grain crop was planted on 26 December, 2001. Grain yield assessments were not made in the spring of 2002 due to miscommunication with the grower. Wheat variety Orita was planted at a seeding rate of 180 lb/A on 16 December 2002.
Goodyear 2002 Cotton Crop:
Cotton was planted on 20 May, 2002 with the grower’s existing 6-row John Deere 7300 MaxEmerge II planter, which was already adapted for no-till cotton planting into grain stubble. Cotton cultivar DeltaPine 451 BR was planted at a seeding rate of 18 lb/A. Several herbicide treatments were applied topically to subplots in each main plot on 6 June, 2002: glyphosate at 0.75 or 1.12 lb ae/A (Roundup UltraMax at 26 or 40 oz/A) + AMS at 1% w/w, clethodim at 0.125 lb ai/A (8 oz/A of Select) + crop oil concentrate (COC) (Herbimax) at 1% v/v or fluazifop-butyl at 0.125 lb ai/A (8 oz/A of Fusilade DX) + COC (Herbimax) at 1% v/v. Glyphosate (Roundup UltraMax) at 0.75 or 1.12 lb ae/A + AMS at 1% w/w was applied topically to all plots on 21 June 2002 at the 4-6 leaf cotton growth stage. On 24-26 July, 2002, when the cotton was at the peak bloom growth stage, subplots of each plot were sprayed at layby with either glyphosate (Roundup WeatherMax) at 1.125 lb ae/A (32 oz/A) + Prometryne at 0.8 lb ai/A + AMS at 1% w/w under WeedSeeker spray units or conventional hoods and glyphosate at 0.91 lb ae/A (Roundup WeatherMax at 26 oz/A) + AMS at 1% w/w post-direct, or glyphosate at 1.12 lb ae/A (Roundup UltraMax at 40 oz/A) + AMS at 1% w/w with the farmer-cooperator’s defoliation boom, which had been modified for layby application. The experiment was harvested on 8 November, 2002. Seed-cotton in the eight center cotton rows of each plot were picked with a John Deere 9965 4-row picker and weighed in a Crust Buster Weigh Buggy (Speed King, Inc.) with a Weigh-Tronix scale (Model 915). A 25-saw gin was used for ginning the seed-cotton.
Goodyear 2003 Cotton Crop:
Cotton variety DP 451 BR was planted late on 13 June 2003 at a seeding rate of 18 lb/A with the grower’s MaxEmerge II planter. Cotton growth and yield data were collected as in the 2002 experiment. Glyphosate (Roundup UltraMax at 48 oz/A) + AMS (Bronc at 1.25 gal/100 gal water v/v) was applied topically on to the cotton on 3 July and 11 July 2003. On 18 August 2003, glyphosate Roundup UltraMax at 48 oz/A) + AMS (Bronc at 1.25 gal/100 gal water) was applied post-direct using the grower’s modified defoliation boom. The experiment harvested on 27 January 2004.
The impact of conservation tillage on irrigation performance was assessed by analyzing infiltration rates and irrigation water advance times. At Coolidge, Marana, and Maricopa, where crops were planted on beds and furrow-irrigated, blocked furrow infiltrometers similar to those of Walker and Skogerboe (1987) were used to measure infiltration. These infiltrometers consisted of two pieces of stainless steel metal cut to the geometry of a furrow. The metal was pounded into the soil, 3 ft apart. The furrows on either side of the furrow being measured were also blocked off (using soil dams) and irrigated at the same time, as was the measured furrow outside of the metal sheets. This was done to minimize horizontal water movement and simulate, as much as possible, measurements being taken during an actual irrigation event. Water was then poured into the dam created by the two pieces of metal and the water depth measured. As the water infiltrated into the soil, more was added. Water depth measurements were made every 30 seconds for the first two minutes, then every minute for the next three minutes, and then every five minutes for the remainder of the first hour. Additional measurements were made every 10 minutes for the second hour, every 20 minutes for the third hour, and every 30 minutes for the fourth and final hour. When water was added into the dam, the time and amount was noted. After all the water had infiltrated into the soil, measurements of the furrow geometry were made and used to calculate the infiltration rate. Throughout the entire measurement period, the water depth within the infiltrometer as well as the area surrounding the measurement zone was kept at a constant depth 3 cm. This was done to assure that the water level did not exceed the height of the bed and to simulate a normal irrigation event. All infiltration measurements were made in non-wheel rows.
At Goodyear, where crops were planted in level basins and flood-irrigated, a modified ring infiltrometer was used similar to that described by Haise et al. (1956). The inner ring, within which the measurements were made, was a piece of well casing 12 in in diameter. The outer ring was constructed from the soil nearby. The outer ring formed a mote and was filled with water maintained at a depth that simulated an irrigation event. The inner ring was filled with water and, water additions and measurement were recorded and the water level maintained as described above for the furrow infiltrometers.
Irrigation water advance times in the various treatments at various sites were recorded a few days after infiltration data were collected. Flags were placed every 100 ft down the row and the time the water reached each flag was recorded as the water advanced down the field. For the Marana and Coolidge sites, six plots (three conventional plots and three conservation plots) were observed in 2002. At the Goodyear site, only one treatment of each was observed. This was due to the irrigation timing (occurring at night) and the change in the irrigation set times during the irrigation event. In 2003, six plots (three conventional plots and three conservation plots) were measured at all sites.
Field slope was also determined for the plots where the infiltration and advance time data were collected. The slope data were taken by setting up a survey transit in the center of the plot and then measuring 300 ft up and 300 ft down the field. These measurements gave a rough estimate of the overall field slope.
To characterize the texture of the soil at each site, soil samples were taken every 6 in down to a depth of 30 in and the percent sand, silt, and clay was determined using a hydrometer and the Bouyoucos method (Bouyoucos, 1936). Additional soil samples were collected at the beginning and the end of the studies at each site to determine conservation tillage induced changes in soil properties. However, due to a lack of consistent plot location at Coolidge and Goodyear, only samples from Marana and Maricopa were analyzed. Twenty-four to 40 soil cores per plot from 0-6 in deep were taken using a 2-in diam soil probe; cores were taken from the top and shoulders of beds and from furrow bottoms. They were combined to form a composite sample per plot. Samples were sent to Brookside Laboratories, Inc., New Knoxville, OH for analyses. They were analyzed for total nitrogen (using a C/N analyzer), total carbon (using a C/N analyzer after they had been pre-treated with acid to remove carbonates), pH (1:1 extract), nitrate/ammonium (using a 1 N KCL extraction), and salts (1:2 extract).
2002 Small Grain Cover and Grain Crops:
At Coolidge, oat and barley cover crops were of similar height and produced similar amounts of biomass. On an individual plant basis, oat plants were much shorter in stature and appeared to produce far less biomass than the Solum barley. However, there were so many barley volunteers in the oat cover crop that most of the biomass in the oat cover crop was barley, accounting for the lack of differences between treatments. The Solum barley appeared to be a superior cover crop compared to oats when produced on limited resources at Coolidge. At Marana, Solum barley plants were significantly taller than brittle stem barley plants; however, there was no statistical difference in their biomass. The barley grain yield at Marana was 7,613 lb/acre. At Goodyear, cover crop assessments were not made and grain yields were not measured in the spring of 2002.
2002 Cotton Crop:
The Yetter 2976 residue managers moved residue and cut a seed line with a fluted coulter resulting in good seed placement in the dry beds. At Marana where the soil is a clay loam, substantial weight had to be added to the 4-row planter (about 200 lb/row) to achieve operation of the residue managers and soil penetration of the coulter and planter units. At Coolidge, the combination of a 6-row planter and a sandy loam soil resulted in good soil penetration and it was not necessary to add extra weight to the planter. Overall the results from the three sites indicated that the no-till cotton planting methods did not negatively affect cotton seedling emergence compared to conventional tillage/planting methods. However, at Marana, emergence was significantly less in the conventional tillage, winter fallow treatment compared to the other treatments. This was caused by the high air and soil temperatures which dried out the seed bed before germination and emergence were completed, despite planting the seed in moisture. The traditional practice in these types of Marana soils in the normal early April to early May planting window is to plant to moisture; however, it would appear that, to obtain a stand, late cotton plantings following grain harvest have to be dry planted and irrigated.
2002 Cotton Weed Control:
WeedSeeker spray units under the Redball 410 hoods were compared to conventional continuous spray nozzles in other 410 spray hoods in terms of the spray volume applied and annual morning glory (Ipomoea spp) control, which was the predominant weed at Marana. Spray volumes of either application system did not vary significantly between similar treatments but the WeedSeeker hoods applied 74-91% less spray volume and herbicide (Roundup UltraMax) than the conventional nozzle hoods. Hanks and Beck observed a 63-85% reduction in the amount of Roundup spray applied using the weed-sensing technology. Although weed control was similar in all treatments, initially, annual morning glory control in the Solum barley cover system (61.25%) was significantly lower than in the other treatments. At the final evaluation, the late planted cotton/Solum barley grain crop system achieved 99% control, and was statistically better than the other treatments. This latter result may have been due to the later planting date and thus smaller weeds being present at the time of application.
At Coolidge, there was an insignificant saving of 3-4 gallons per acre (GPA) of herbicide spray using the WeedSeeker system compared to the conventional nozzle hoods at the first post-directed spray date in the oat and barley cover crop systems for the control of horse and common purslane. However, on July 16, 2002, the WeedSeeker system provided significant 15-20% spray volume savings among the oat and barley cover crop systems. The reduction in spray volume savings at Coolidge relative to Marana was probably due to the poor control of common purslane by the first application of Roundup Ultramax. This poor control resulted in a high density of large-sized plants and near continuous spraying by the WeedSeeker spray units during the next herbicide application. The conventional tillage system gave the best control of common and horse purslane by combining mechanical and chemical weed control methods. There were no differences in weed control between the WeedSeeker-equipped hoods and the conventional nozzle equipped hoods.
At Goodyear, initial control of volunteer barley and horse purslane using Roundup UltraMax at 26 or 40 oz/A was significantly better than using Select or Fusilade at 8 oz/A, and Roundup UltraMax tended to give better control of volunteer barley and horse purslane at 40 oz/A than at 26 oz/A. The weed density at the Goodyear site was relatively low, and Roundup UltraMax applied in July resulted in 84 to 100% control of volunteer barley, junglerice, horse purslane, and volunteer alfalfa.
Cotton plant heights at Marana in July were significantly greater in the early planted cotton/minimum tillage plots compared to the other treatments, but plant heights later in the season did not significantly differ among the treatments. Height-to-node ratios (HNR) were statistically similar among the treatments. At Coolidge, conventional tillage cotton plants were significantly shorter than the conservation tillage cotton plants. While HNR were similar among the treatments initially, the conventional tillage plants later had lower HNR than the conservation tillage plants. At Goodyear, the treatments in which cotton was planted without tillage in the spring (i.e., spring no-till) were characterized by taller plants and greater HNR. Thus, at all sites, treatments with the least amount of tillage were characterized by taller plants with increased HNR.
Seed cotton yields at Marana showed that early planted cotton in either a conventional or reduced tillage system significantly out-yielded late planted cotton. Early planted cotton lint yield in the conventional tillage system (1140 lb/A) was similar to that of the early planted cotton in the reduced tillage system (1089 lb/A). The late planted cotton in the conventional tillage system produced the least amount of lint (827 lb/A); the late planted cotton in the reduced tillage system produced 927 lb/A. Clark and Carpenter (1998) and Silvertooth et al. (1998) observed cotton yield reductions when cotton was planted late at Marana and Maricopa in Arizona. At Coolidge, the conservation tillage systems with either an oat (1007 lb/A) or barley (1089 lb/A) cover crop substantially out-yielded the conventional tillage system (880 lb/A) in terms of lint production by 14.4 % and 23.8 %, respectively, the results being similar to Kaddah (1977). The higher yields were probably due to the greater amount of irrigation water applied in the conservation tillage treatments. There were no differences in cotton yields among the tillage systems at Goodyear. Although percent lint was significantly lower in the fall no-till, spring no-till treatment than the other treatments, lint yield did not significantly vary among the treatments.
2003 Barley Cover and Grain Crops:
The amount of biomass produced by the cover crops ranged between 3,527 and 16,646 lb/A, varying considerably depending on location, rainfall, and when the cover crop was killed with a herbicide. For example, the greatest Solum barley biomass was produced with two irrigations plus rainfall and early termination at Marana (5,642 lb/A), or with late termination at Maricopa (16,646 lb/A). Solum barley was bred to maximize root development and tillering and is a low-input barley variety that can respond favorably to additional water in the form of rain or an additional irrigation (after the germinating irrigation following planting). The amount of Solum biomass at Maricopa in 2003 was prodigious resulting in a residue layer up to 4 inches thick on the soil surface and presented a supreme challenge with respect to no-till cotton planting. The grain crops were harvested with conventional grain harvesters with the Solum barley yielding between 1,071 lb/A (Maricopa) to 2,773 lb/A (Marana). The Orita wheat in Goodyear yielded 6,400 lb/A in 2003.
The John Deere 1560 no-till grain drill was used to plant the fall 2003 barley cover crops and grain crops into existing beds at Coolidge, Maricopa and Marana. Our observations in 2003 confirmed our experience at Marana in the fall of 2002 and indicate that this type of grain drill can successfully plant on existing beds without tillage following cotton despite the presence of 6 to 10 inch tall cotton stalks. Arizona has a "plow down" requirement following cotton harvest to facilitate pink bollworm control that has the effect of promoting tillage. The regulations require growers to disrupt cotton root-soil connections to kill the cotton plants, which most growers accomplish by shredding stalks, pulling the roots loose from the soil with a root puller, and disking at least twice. Alternatively, the regulations allow growers to plant a small grain crop provided it is irrigated in December. This option is based on data showing that the combination of cold winter temperatures and irrigation resulted in a lack of pink bollworm emergence from the cotton stalks in the spring.
With our successful planting demonstrations, several growers have expressed interest in no-till planting of grain crops following cotton in order to avoid significant tillage costs following cotton. Avoiding fall tillage after cotton also has the benefit reducing the production of PM10 dust, which is a significant problem in the Phoenix, Arizona, area. Our experience in the fall of 2003 irrigating the field at Marana suggests that the number of crop cycles that can be grown will depend on maintaining irrigation efficiency. At Marana after two annual barley-cotton cycles, the head end of the field (i.e., next to the irrigation ditch) eroded away and was lower than the rest of the field making irrigation difficult. Conversations with growers suggest that at this point they would finish the third barley planting as a grain crop (or plant wheat) and then till and laser-level the field. The amount of slope in furrow-irrigated fields as a function of soil type required to maximize the number of grain-cotton double crop cycles needs to be further investigated. In addition, more research is needed to verify that planting grain crops, particularly wheat, on beds with a no-till grain designed to operate on flat ground (i.e., no beds) does not compromise grain yields.
2003 Cotton Crops:
Cotton was successfully planted directly into barley cover crop residues and grain crop stubble using standard John Deere MaxEmerge planters equipped with Yetter Farm Equipment 2976 residue manager/coulter assemblies at Coolidge, Maricopa and Marana. The Yetter 2976 residue managers did a good job of moving residue and cutting a seed line with a fluted coulter resulting in good seed placement in the dry beds at all locations despite the wide range in the amount of residues on the soil surface. At Marana and Maricopa, 200 lb or 100 lb per row unit, respectively, had to be added to the 4-row planters to achieve good operation of the residue managers and soil penetration of the coulter and planter units. At Coolidge, where there is a coarse-textured soil, good soil penetration of the planter units was obtained without adding extra weight to the grower’s 6-row planter. The Goodyear site was planted with the grower’s existing MaxEmerge cotton planter, which was already adapted for no-till cotton planting into grain stubble. Overall, the results from the Marana, Coolidge, and Goodyear sites indicated that the no-till cotton planting methods did not negatively affect cotton seedling emergence compared to conventional tillage/planting methods and plant populations in the range of 25,000 to 60,000 plants/A (6 to 15 plants/meter of row on 1 m row spacing) were obtained. At Marana the conventional tillage, late plant cotton plots were dry planted similar to the minimum tillage plots and irrigated to germinate the cotton seed. Plant populations were relatively low at 25,000 to 28,000 plants/A (6.23 to 7.17 plants/m of row) at Coolidge, and there were significant canopy gaps in the minimum tillage plots that contributed to reduced yield. The small plant population was due to the grower’s use of the Sundance ripper/bedder, which produced poor, rough beds, and to planting without the Yetter attachments on the MaxEmerge planter in 2003. A significant finding at Marana in 2003 was that the Yetter 2967 residue manager/coulters easily shattered and moved the old shredded cotton stalks remaining from the 2002 cotton season in addition to the barley residues.
Cotton growth was assessed in the various treatments by measuring plant height and counting the number of nodes per plant at various times during the cotton season in both conventional tillage treatments and reduced tillage treatments. In Coolidge, the cotton plants in the minimum tillage treatments were taller than the plants in the conventionally tilled treatment in 2002 possibly because the minimum tillage treatments received more irrigation water. However, in 2003 when similar amounts of irrigation water were applied to the various treatments, there were no differences in plant heights or height-to-node ratios. In Goodyear, there were no differences in plant heights or HNR because the tillage operations were the same for both treatments.
In Marana, there were differences in plant height related to both planting date (later planted cotton was shorter) and tillage with taller plants in the no-tilled cotton treatment in 2003. At Maricopa in 2003, there were differences in plant heights related to planting date (later planted cotton was shorter) but there was no height difference between the conventional tillage treatments and the no-till cotton treatments. Although there were inconsistencies between experiment sites with respect to plant heights, where significant differences occurred, the minimum or no-till cotton treatments had taller plants compared to the conventionally tilled cotton treatments.
Cotton growth was also assessed by harvesting the experiments and comparing cotton lint yields between treatments. At Coolidge the minimum tillage treatment yielded 24% less than the conventional tillage treatment yield of 1539 lb/A. There were no differences in cotton yields among the tillage systems at Goodyear in 2003. In Marana and Maricopa, there were yield differences between treatments related to planting date with the late planted cotton yielding less than the early planted cotton. At Marana, the no-till and conventionally tilled cotton yields were not statistically different although there was a numerical trend of lower yield in the no-till cotton treatments. At Maricopa, the early planted no-till cotton yielded less than the early planted conventionally tilled cotton (956 versus 1141 lb/A) and there was a similar but not statistically significant trend in the late planted cotton treatments.
Although the yield comparisons are not yet definitive, it appears that in some situations no-till cotton may yield less than conventionally tilled cotton. More research is needed to determine if this trend is consistent but we think that there may be non-tillage-related reasons for this apparent trend. Cotton petiole samples and the color of the cotton plants in the no-till cotton treatments suggest that plants in these treatments did not receive sufficient nitrogen possibly due the decomposition of organic matter in these treatments. In addition, at Coolidge and Marana, substantial injury symptoms from the Caparol (prometryn) layby herbicide applications (leaf burn and boll death) may have reduced yields. The herbicide injury may have occurred because the plants had shallower root systems in the no-till plots or may have been due to the volatility of prometryn at high temperatures (>100 F).
2003 Cotton Weed Control:
WeedSeeker spray units under the Redball 410 hoods were compared to conventional continuous spray nozzles in other 410 spray hoods in terms of the spray volume applied and weed control. The data collected in Coolidge and in Marana suggest that the weed-sensing automatic spot-spray system can reduce the amount of spray volume and herbicide used by about 50 to 60%, but the data from Maricopa in 2003 indicate the savings can be much greater (e.g., in the treatment with thick Solum cover crop residues) or much less if volunteer grain germinates after grain harvest. In general the weed control data comparing spray systems collected in 2003 in Marana and Maricopa indicate that the weed control obtained with the weed-sensing, automated spot-spray system provides commercially acceptable weed control comparable to that obtained with conventional continuous spray systems for most weed species. However, the data also indicate that for some weed species such as annual sowthistle at Marana and sprangletop at Maricopa, the automated system did not perform quite as well as conventional continuous spray technology with the postemergence herbicides that we applied. The Coolidge weed control data comparing conventional continuous spray technology with the weed-sensing, automatic spot-spray systems indicate that under some conditions, the weed-sensing sprayer did not perform adequately.
Factors affecting the performance of the WeedSeeker units include setting of the sensitivity level of the computer controller, the size of the weeds sprayed (and therefore the timeliness of herbicide applications), and the presence of sparse barley cover crop residues. A larger calibration spray volume (GPA) and higher pressure may solve some of these problems by improving weed foliage spray coverage. Cumulative weed control evaluations made later in the season at Coolidge, Marana, and Maricopa after multiple herbicide applications suggest that it is possible to obtain commercially acceptable weed control in conservation or minimum tillage cotton production systems. However, the weed control data also indicate that controlling weeds in conservation tillage systems remains a challenge and that additional research is needed to develop improved weed control strategies.
2003 Straw Management Study:
A study was conducted at the Maricopa Agricultural Center in 2003 to assess various straw management strategies during grain harvest prior to no-till cotton planting. The treatment list included a conventional tillage treatment (winter fallow), two cover crop treatments (beardless barley and Cayuse oats), and several Solum barley treatments all harvested for grain but cut at different heights (5 inches, 9 to 10 inches, and 17 to 18 inches) leaving different amounts of stubble in the field. The cereal biomass prior to harvest was determined in each cover crop or grain crop treatment along with grain yields; there were no significant differences between treatments in any of the measured parameters. Because of the way the grain harvesters spread the straw following harvest, it was not possible to accurately measure the amounts of barley residue following grain harvest. Cotton plant establishment after no-till planting, cotton plant height and HNR were similar in all of the treatments. Cotton yields also did not differ between the straw management treatments. These results indicate that the methods we are using for planting no-till cotton are not very sensitive to differences in straw biomass or the height of the standing stubble following grain harvest. Although a second year study will provide more data, it appears the no-till planting method on beds is very robust and growers do not have to pay particular attention to straw management.
2004 Barley Cover and Grain Crops:
The amount of biomass produced by the cover crops were 4,960lb/A at Coolidge, 3,567 lb/A at Marana and 3,716 lb/A at Maricopa. The grain crops were harvested with conventional grain harvesters. Solum barley grain yield was 2,231lb/A at Marana, and 3,260 lb/A at Maricopa.
2004 Cotton Crop:
The no-till cotton planting methods did not negatively affect cotton seedling emergence compared to conventional tillage/planting methods and plant populations in the range of 40,000 to 50,000 plants/A (10 to 13 plants/meter of row on 1 m row spacing) were generally obtained. However, emergence of the late planted cotton at Marana was hampered by poor irrigation, which resulted in the water running over the top of the beds and sealing them before the seedlings could emerge.
Cotton growth was assessed in the various treatments by measuring plant height and counting the number of nodes per plant at various times during the cotton season in both conventional tillage treatments and reduced tillage treatments. At Coolidge, the no-till cotton grew rank and was significantly taller than the conventional tillage during and at the end of the season; however, there were no differences in the HNR. At Marana, there were no differences in plant heights and the HNR at the end of the season. At Maricopa, there was no particular trend in plant heights and HNR, though the early planted no-till and the late planted conventionally tilled cotton tended to be taller and have greater HNR than cotton in the other treatments.
Cotton growth was also assessed by harvesting the experiments and comparing cotton lint yields between treatments. At Coolidge, there were no yield differences between the conventional tillage and no-till cotton. At both Marana and Maricopa, there were yield differences between treatments related to planting date with the late planted cotton yielding less than the early planted cotton. At Marana, lint yield differences were also related to tillage. The early planted conventionally tilled cotton (1,693 lb/A) produced a significant 23% more lint than the early planted no-till cotton (1,378 lb/A); both of them significantly out-yielded the late planted cotton. The poor performance of the late planted conventionally tilled cotton was partly due to the low plant population (19,318 plants/A) that resulted from the poor irrigation. At Maricopa, there was no yield difference between the two early planted cotton systems, but both of them significantly yielded higher than the late planted cotton systems. The late planted conventionally tilled cotton produced significantly more lint (28%) than the late planted no-till cotton.
2004 Cotton Weed Control:
Data from Marana and Maricopa suggest that the weed-sensing automatic spot-spray system could reduce the amount of spray volume and herbicide used by about 36 to 63%. Data from Maricopa in 2003 indicated that the savings could be much greater (e.g., in the treatment with thick Solum cover crop residues) or much less if volunteer grain germinated after grain harvest (Adu-Tutu et al., 2003). At Maricopa in 2004, the presence of large volunteer cotton in the treatment with Solum barley cover crop residue during herbicide application reduced the savings in spray volume and herbicide used relative to the savings in 2003. In general the weed control data comparing spray systems in Marana and Maricopa indicate that the weed control obtained with the weed-sensing automated spot-spray system provided commercially acceptable weed control comparable to that obtained with conventional continuous spray systems for most weed species. However, the data also indicate that for some weed species such as sprangletop and volunteer barley at Marana and skeletonweed at Maricopa, the automated system did not perform quite as well as conventional continuous spray technology with the postemergence herbicides that we applied. Factors affecting the performance of the WeedSeeker units include setting of the sensitivity level of the computer controller, the size of the weeds sprayed (and therefore the timeliness of herbicide applications), and the presence of sparse barley cover crop residues. A larger calibration spray volume (GPA) and higher pressure may solve some of these problems by improving weed foliage spray coverage. Cumulative weed control evaluations made later in the season at Marana and Maricopa after multiple herbicide applications suggest that it is possible to obtain commercially acceptable weed control in conservation or minimum tillage cotton production systems. However, the weed control data also indicate that controlling weeds in conservation tillage systems remains a challenge and that additional research is needed to develop improved weed control strategies.
2004 Straw Management Study:
A study was conducted at the Maricopa Agricultural Center to assess various straw management strategies during grain harvest prior to no-till cotton planting. The treatment list included a conventional tillage treatment (winter fallow), two cover crop treatments (beardless barley and Cayuse oats), and several Solum barley treatments harvested for grain but cut at different heights (5 inches, 9 to 10 inches, and 17 to 18 inches) leaving different amounts of stubble in the field. The amount of cereal biomass was determined in each cover crop or grain crop treatment prior to harvest because the way grain harvesters spread the straw chaff makes it impossible to accurately measure the amounts of barley residue following grain harvest. Grain yields were significantly lower when the grain crop was cut above the normal height of about 5 inches because the harvester did not collect heads of plants that had lodged lower than the pre-determined cutting heights. There were no significant differences between treatments in any of the measured parameters. Cotton plant populations after no-till planting, cotton plant height, and HNR were generally similar in all of the treatments, though the conventional tillage cotton was significantly taller than most of the no-till cotton that followed a grain crop. The cotton mainstem nodes at which the first fruiting branch and the position of the first sustained boll occurred were also assessed. The height of the cereal stubble did not affect the position of the first fruiting branch or the first retained boll of cotton that was planted after the cereal crops. Cotton yields also did not differ between the straw management treatments. These results indicate that the methods we used for planting cotton without tillage are not very sensitive to differences in straw biomass or the height of the standing stubble following grain harvest. It appears the no-till planting method on beds is very robust in Arizona’s environment and growers do not have to pay particular attention to straw management.
Changes in Soil Properties:
Percent nitrogen, percent organic carbon, and pH increased between 2001 and 2004 in all the treatments at Marana. However over the same period, the amount of soluble salts, NO3-N, and NH4-N decreased. At the end of the 2004 cotton season, there were no differences among the treatments in all the parameters assessed at Marana, except nitrate-nitrogen: the winter fallow, conventional tillage, early cotton planting and the Solum barley grain crop, no-till, late cotton planting treatments had significantly more nitrate-nitrogen than the other two treatments. At Maricopa, the winter fallow, conventional tillage, early cotton planting treatment had the least amount of organic carbon (0.457%), being significantly different from the Solum barley grain crop, no-till, late cotton planting treatment (0.541%), but similar to the other treatments. The small changes in percent organic carbon suggest that in the hot, irrigated agriculture characteristic of Arizona, conservation tillage practices have little effect on soil properties.
EFFECTS OF TILLAGE PRACTICES ON IRRIGATION
Soil Texture
The Coolidge site (2002-03) contained the greatest amount of sand of the four sites. Although there was some variation between depths at Coolidge, overall, the percentages of the particle size categories stayed fairly constant with clay slightly increasing with depth while sand slightly decreased. Overall, the soil would be classified as a sandy clay loam. In 2004 the soil at the new site was still dominated by sand, although the percent was less than the plots in 2002 and 2003. Also, the new field had almost equal amounts of silt and clay.
With clay content above 40% in the top 2 feet of the soil profile, the soil at the Marana site contained the greatest percentage of clay among the experimental sites. The sand and silt contents varied slightly with depth and there was a relatively large change at the 2-ft depth. Soil classifications for each layer ranged from clay to sandy clay but overall the soil at Marana is classified as clay soil.
The Goodyear site had greater than 50% silt content throughout the upper 30 inches of the soil profile. The clay content was greater in the top 2 feet and then decreased to almost equal the percentage of sand at the 30-inch depth. The soil types ranged from silty clay loam to silty clay to silt loam, but overall, the Goodyear soil would be classified as a silty clay loam.
Clay dominated the top 18 inches of the soil at the Maricopa site. At 24 inches, the sand content increased almost 20% and was at 60% at the 30-inch depth. Soil types ranged from clay loam in the top 18 inches to sandy clay loam in the 18-30 inch depths. Overall, the soil type would be classified as a clay loam.
Infiltration
Conservation tillage practices would be expected to increase infiltration by leaving old root channels intact, allowing the water to flow deeper through the soil vadose. Also, surface organic residues usually slow the advance of the water front resulting in increased opportunity time for infiltration. However, in many situations in surface irrigation, increased infiltration may actually hinder the movement of water down the field, resulting in excessive water application and reducing irrigation efficiency. At all of the sites, soil samples were taken prior to infiltration measurements to determine if any difference existed in soil moisture in the top 30 inches. None of the sites showed any differences at the time of the infiltration/advance time measurements (data not shown).
2002 Season
Infiltration measurements were performed at the Coolidge site on May 22, 2002. Due to the high sand content in the soil at that site, the infiltration was relatively high with 10 and 7 inches of water infiltrating the soil in a four-hour period in the conservation and conventional treatments, respectively. The soil at the Marana site contained a much higher concentration of clay than the Coolidge site. Infiltration measurements were done on June 4 – 5, 2002. Although the water in the conservation plots had a higher initial infiltration rate, at the end of the four-hour measurement period, an average of 4 inches of water had infiltrated into both the conventional and conservation plots. The soil at the Goodyear site was silty, and the soil was relatively moist at the time of assessment. Infiltration data were recorded on June 20 – 21, 2002. Within the four-hour infiltration period, an average of 1.5 inches of water infiltrated the conservation treatment while 1 inch of water infiltrated the conventional treatment. These results indicate that on coarse-textured soils, conservation tillage practices did appear to increase infiltration as expected. In the finer textured soil at Marana, there was initially a faster infiltration rate but the total amount of water infiltrated was equal at the end of the four-hour measurement period.
2003 Season
Infiltration measurements were conducted at the Coolidge site on May 15, 2003. The results were similar to 2002 with the conservation plots having a much greater infiltration rate. Similar to the 2002 data, the conservation plots averaged just over 10 inches of water infiltrated in a four-hour period. The conventional plots infiltrated just over 4 inches in the same time period. This was actually 3 inches less than in 2002. The Marana data from 2003 showed that the conventional plots actually infiltrated more water than the conservation plots. The difference was less than 1 inch over the four-hour measurement period. At the Goodyear site, infiltration data were taken but the treatments for all plots were considered the same since deep ripping and land leveling took place during the spring of 2003. As in 2002, the amount of water infiltrated was well below the other sites. The MAC site was added in the fall of 2002. The conservation plots infiltrated more water than the conventional plots. For the MAC site, the difference was 2.4 inches during the four-hour measurement period.
2004 Season
Infiltration measurements were conducted at the Coolidge site on May 13-14, 2004. The results were similar to 2002 and 2003 with the conservation plots having a much greater infiltration rate. The Marana data were almost the direct opposite of the 2003 season in that the conservation plots infiltrated 5.8 inches in four hours and the conventional plots averaged only 4.2 inches. At the Maricopa site, the results were similar to the 2003 data with the conservation plots averaging just over 4 inches of water infiltrated after four hours while the conventional plots only infiltrated 2.6 inches. The Goodyear site was not evaluated in 2004.
Advance Times and Field Slope
2002 Season
The Coolidge site had a fairly shallow field slope measuring 0.06%. Advance time measurements (June 3-5, 2002) showed the irrigation water reached the end of the conventional plots in about one hour but had not reach the end of the conservation plots after 8.5 hr, at which point measurements were suspended due to darkness. Both wheel and non-wheel rows were to be measured but due to breaks in the beds where the water would cross over into the adjoining row, the conservation non-wheel row was stopped at 900 ft and the conventional wheel row was dropped from the data set. The grower’s set times for irrigating the conventional and conservation plots for the 2002 season were 6 and 12 hrs, respectively.
The Marana field had a slightly greater slope of 0.08%. The advance times recorded on June 6, 2002, for both wheel and non-wheel rows. Water in the wheel rows for both treatments advanced faster down the field than water in the non-wheel rows. However, water in the conservation non-wheel row advanced faster than water in the conventional non-wheel row.
The Goodyear site had the greatest measured slope of the three sites. Measurements indicated that plots had a field slope of 0.12%. Advance times measured on June 22, 2002. At the beginning of the irrigation, water in both treatments seemed to be advancing at the same rate. However, by the end of the measurement period, the advance times differed by about one hour. Measurements were suspended at 1000 ft from the ditch because water was backing up within the plot, making it impossible to determine advance times. In fact, for the conventional plots, in-field borders, running perpendicular to the water flow were constructed along both sides to slow the advancement and help to more evenly distribute the water.
2003 Season
The Coolidge plots measured in 2003 were similar but not the same plots as in 2002. Due to problems with plot size and the irrigation water supply ditch, the research plots were moved west. This meant that Rep 2 became, Rep 1, Rep 3 became Rep 2, etc. In 2002, Reps 1, 2 and 3 were measured. In 2003, Reps 2, 3 and 4 were measured. The average slope for the plots in 2003 was 0.04%, slightly lower than in 2003. Advance time measurements were difficult to obtain due to continuous break-overs into adjacent rows. Only the conventional wheel row was recorded to the end of the field. However, some data were collected for both treatments in both the wheel and non-wheel rows that allowed some comparisons. For example, at the 800 ft distance, the water in the conventional-wheel row arrived in just over one hour while water in the conservative wheel row took almost 3.5 hours to reach the same distance. Also, the advance times for the conservation and conventional non-wheel rows were virtually the same until the 400 ft mark when the water began breaking into adjacent rows.
The Marana elevation data for 2003 showed the fields to average about 0.05% slope, slightly lower than the 0.08% measured in 2002. The advance time results were similar to 2002 with the water in the conventional wheel row having the fastest advance time. However, unlike 2002, the conventional non-wheel row had the slowest advance times. These data support the theory that perhaps the soil’s natural cracking abilities may be compensating for the increased infiltration cause by the conservation tillage effects. In the conventional plots, the bare soil has a tendency to form large, deep cracks in the soil. As the advancing water reaches these cracks, the water must first fill the cracks before continuing down the row. In the conservation plots, the advancement of the water is often hindered by the surface residue. These two characteristics, the cracks and the surface trash, seem to have similar effects on water advancement.
In Goodyear, data were recorded on four plots. Although all of these plots were deep ripped and replanted, there were still some inherent spatial differences in slope. The plots measured averaged 0.06% slope, ranging from 0.04-0.08%. The advance times shown in Figure 18 reflect this with the slope of plot 3 and 4 measuring 0.04%, the slope of plot 5 measuring 0.06% and the slope of plot 6 measuring 0.08%.
At the Maricopa site, the data showed the fields actually increasing in elevation toward the end of the field. This was due to the quick rise that occurred at the 600 ft mark (the end of the field). This was done at the farm to assure the water doesn’t leave the field and spill into the adjoining road. Once the 600 ft reading was removed, the field had a slope of 0.00007%, basically level. The advance times recorded followed a somewhat expected pattern with the water in conventional wheel rows advancing the fastest, followed by the water in the conventional non-wheel row, the water in the conservation wheel row, and lastly the water in the conservation non-wheel row.
2004 Season
The Coolidge plots measured in 2004 were located at the same farm but in a different field. The geometry was also different with furrow every 80 inches and large beds between them with 2 rows of cotton planted on the bed. Thus, every furrow was a wheel row. The water in the Conventional plots had an average time (average of 4 furrows) of 2 1/3 h to reach the end of the field (900 feet). The conservation plots to approximately one additional hour to reach the end. Field slope measurements showed the field fairly level with a 0.02% slope from the head end of the field to the end of the field.
The Marana plots in 2004 seemed to be “leveling off” with a slope of 0.001% from head to tail. However, the advance time data were similar to the past years with the conventional wheel row being the fastest and the conventional non-wheel being the slowest.
At the Maricopa site, the elevation data again showed a quick rise at the end of the field. Once this data point was removed, it revealed that the slope had actually increased since 2003, and was now at 0.002% instead of 0.00007% measured last year. The advance times showed the two treatments differed by almost 1 h and that both the wheel and non-wheel furrows reacted the same within treatments.
Irrigation Water Applied
The irrigation water applied to the cotton crops in the 2002, 2003, and 2004 seasons was recorded. In 2002 and 2003, at the Coolidge and Marana sites, conservation tillage plots received more water than the conventional plots. At Goodyear, both tillage systems received the same amount of water. Thus, as expected, conservation tillage practices increased irrigation advance times and the amount of water applied to the cotton crop at Coolidge and Marana but the greater field slope at Goodyear appeared to minimize the effect of tillage practices on irrigation water advance times and the amount of water applied. At Coolidge, the low slope, low irrigation water supply flow rate, and sandy soil led to excessive water application. The long set time meant inefficient irrigation, causing an additional 21 inches of water to be applied to the conservation plots in 2002, and 12.6 inches more in 2003. At Marana, with a high clay content soil, the additional water applied was only in the beginning of the season. In both years, the additional water was applied due to the difference between pre-irrigating the conventional plots as opposed to irrigating up the conservation plots. At Goodyear, the presence of surface trash on the no-till plots helped to slow down the water front, an effect similar to the construction of in-field borders on the conventional plots.
In 2002, only the Coolidge site showed a significant difference in yield. This may be due more to the additional 21 inches of water applied to the conservation plots than the effects of the management itself. In the 2003 season, the Coolidge site again showed a significant difference in yield but in the reverse order, i.e., the conventional yielded higher than the conservation. This may have been due to herbicide damage that was observed. At the Maricopa site, yields were relatively low compared to data from other fields on the farm and the cause of the yield difference is not yet known
Specific impacts and contributions were due to the publication of two research reports in the University of Arizona, College of Agriculture and Life Sciences 2003 Cotton Report, an additional two publications in the 2004 Cotton Report, two more publications in the 2005 Cotton Report, and the interactions of project participants with Arizona farmers at experiment station field days and Cooperative Extension workshops. The outcomes to date include the continuing enthusiasm of our grower cooperators and the interest of other farmers in conservation tillage practices.
External funding was also obtained from the Arizona Grain Council, the Arizona Cotton Growers Association, and Cotton Incorporated to continue on-farm demonstrations and research with Arizona farmers in 2005. Four farmers used the John Deere 1590 drill to plant grain crops following cotton harvest in fall-winter 2004-05 and 4 additional growers planted with the drill in the fall-winter 2005-06. Additionally, the John Deere 1590 drill has been used to no-till plant winter pasture seed mixtures in dormant bermudagrass. Additional farmers seem interested but are still hesitant to adopt new practices and are waiting for us to gather additional data and experience with conservation tillage practices. Discussion of crop budgets for conservation tillage and the associated cost advantages along with the demonstration of better weed control will increase the willingness of farmers to try the system. The results of the last two fall, small-grains planting seasons suggest that tillage costs of $40 to $50/A can be saved and that grain yields on beds are comparable to yields of traditional broadcast grain plantings following tillage. No doubt, we have raised the awareness of Arizona growers regarding conservation tillage practices through our routine contacts with growers, through our grower participants talking to other growers, and the more formal activities discussed above.
Research Outcomes
Education and Outreach
Participation Summary:
Outreach has consisted of verbal presentations at Cooperative Extension meetings and experiment station field days (both in Arizona and California) and poster presentations at experiment station field days. Presentations were also made at scientific meetings such as at the Cotton Beltwide meetings in 2003 (3 presentations, 2004 (3 presentations) and 2005 (2 presentations) and the Western Society of Weed Science meetings. Peer-reviewed publications and Cooperative Extension publications are also being developed.
Education and Outreach Outcomes
Areas needing additional study
Our no-till cotton yields have been inconsistent with a declining yield evident at Maricopa. Further work is need to clarify if this is an irrigation management or soil fertility issue. Experiments are planned to address this issue.