Conservation Tillage Benefits in a Cotton Centered Crop Rotation System
The tillage operations required to grow a barley and cotton crop rotation were reduced by eliminating tillage prior to planting cotton, eliminating cultivations for weed control in cotton, and especially by eliminating tillage following cotton. In the absence of tillage, barley residues increased water infiltration into course textured soils and reduced irrigation advance times. At some sites, this increased the amount of irrigation water used to produce cotton. Adequate cotton weed control was achieved in conservation tillage systems but remains a challenge. Weed-sensing, intermittent spray technology reduced the amount of spray volume and herbicide used for cotton weed control.
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.
First, evaluate the planting of cotton into cover-crop residues or into small grain crop stubble without preseason tillage. A barley cover crop and a barley crop harvested for grain will be planted and grown and then cotton will be planted into either the herbicide-desiccated barley cover crop or the grain crop stubble using a no-till cotton planter. The amount of biomass produced by the cover and small grain crops will be measured. In addition, a no-till, randomized complete block experiment will be established to evaluate how grain straw and stubble should be managed to obtain optimum growth of the following cotton crop. The effects of variety, height of stubble at the time of cotton planting, removal of straw, and other factors will be evaluated. The no-till treatments will be compared to a conventional cotton production system (i.e., the standard practice treatment) that involves pre-plant disking, listing and shaping of beds, planting, and cultivation for weed control after planting.
Second, evaluate a weed-sensing sprayer and a post-emergence herbicide weed control program in minimum-till cotton. Since cover crops and grain stubble can suppress weed emergence, it may be possible to eliminate the use of preemergence herbicides in no-till cotton. Roundup Ready cotton varieties will be planted in all experiments and, prior to the fifth true-leaf cotton growth stage, Roundup (glyphosate) will be sprayed over the crop row in all treatments. At later growth stages, Roundup and other herbicides will be post-directed at the base of the cotton plants. In the minimum-till treatments, the inter-row space will be sprayed using a hooded sprayer; two hoods will contain WeedSeeker spray units and other hoods will contain standard continuous spray nozzles. In the conventional cotton treatments, the inter-row space will be cultivated and sprayed as necessary with the grower’s standard post-directed herbicide sprayer. All cultivations and the volume of spray and the amount of chemical used in all herbicide applications will be recorded in order to determine the economics associated with different weed control practices and the degree to which weed-sensing sprayer technology can reduce the amount of herbicide introduced into the environment. Weed control operations will be conducted as needed by treatment in response to weed emergence. The type and density of weed species emerging in all treatments will be recorded at times corresponding to herbicide applications. Data will be used to determine the effects of preemergence herbicide, tillage, cover crop, grain stubble on weed populations, and the efficiency of the weed-sensing sprayer.
Third, evaluate changes in soil properties such as organic matter content, crusting, water infiltration, and associated changes in fertility and irrigation practices. A variety of soil and water measurements will be made over the 3-year course of this project to document beneficial changes in soil characteristics. The top 12 inches of the soil profile will be sampled prior to cotton planting and after cotton harvest to determine the amount of nitrate nitrogen in the soil for crop fertility management and to monitor changes in soil organic matter content (measured as total organic carbon), carbon/nitrogen ratios, and estimated sodium percentage (ESP). The water-holding capacity of the top foot of the soil profile will also be measured gravimetrically. During cotton seedling establishment, the effects of soil crusting and compaction will be monitored by comparing cotton plant emergence relative to the number of seed planted and by comparing cotton emergence between treatments. Early in the cotton season when barley residue levels are highest, water infiltration will be measured using ring infiltrometers and irrigation advance times will be measured. Cotton nitrogen status in-season will be monitored using petiole tissue samples.
Fourth, collect and compare operational, agronomic (i.e., plant growth), and cost data for minimum-till and conventional production systems. For each experimental site, detailed records of all crop input and field operations including the time required to perform various operations will be maintained along with information on the tractors and other equipment needed to perform operations so that detailed crop budgets can be developed for each treatment. The crop budgets will include both operational costs (cash costs) and equity and capital costs. These budgets are essential to documenting the potential to reduce long-term production costs in conservation tillage systems and the economic benefits of minimum-till cover crop or double crop systems in Arizona. The crop budgets will also document what costs increase or decrease in conservation tillage cotton production systems. An economic analysis of the weed sensing sprayer used in conjunction with other weed control practices will be done to determine if the savings in time and chemical along with eliminating tillage for weed control can justify the capital cost of the WeedSeeker sprayer technology.
Fifth, disseminate information on alternative production practices. A multifaceted approach involving field days, Extension meetings, publications, and web sites will be used to disseminate the results of the research and the crop budgets and other economic data. We will conduct field days to introduce the project and its objectives at appropriate times, possibly at each experimental site depending on grower interest. We will attempt to demonstrate the impact of cover crops on cotton stand establishment and the method of no-till planting in grain stubble. Preseason or early season meetings with cotton producers will be conducted during the spring of each year and the results obtained to date shared with producers. A survey of meeting attendees will be conducted to solicit input on the project and gauge the level of interest in adopting conservation tillage practices among growers. Research reports will be written following cotton harvest each year and photographs and other information will be posted on a University of Arizona crop production web site. Presentations will also be made at national meetings such as the Cotton Beltwide meetings, the Agronomy Society meetings, and the Western Society of Weed Science meeting.
Evaluate the planting of cotton into cover-crop residues or into small grain crop stubble without preseason tillage.
Field trails were established in October and November of 2001 by planting barley crops on three commercial farms (Fast Track Farms, Coolidge; A Tumbling T Ranch, Goodyear; and John Thude Farms Partnership’s Paradise Ranch) and at an experiment station (University of Arizona Marana Agricultural Center). The experiment at Coolidge was reconfigured and simplified to reduce the area of the experiment and the amount of water required. The experiment at Paradise Ranch encountered numerous difficulties including loss of the first cotton planting due to water management problems with the center-pivot irrigation system. A cotton seed-lot with poor cold germination was planted at this site in 2003 and the resulting crop failure precluded us from gathering data at this site. The treatments varied among the three remaining sites and were strongly influenced by what our farmer cooperators were able and willing to investigate. A Tumbling T Ranch in Goodyear was unable to support a straw management experiment despite the cooperator’s interest in the results due to the space and resource commitment. In addition, Arizona Public Service Company (APS) constructed their Southwest Valley 500 KV transmission line from the Palo Verde Nuclear Power Plant through the A Tumbling T Ranch destroying some plots and severely compacting the soil in a portion of the field. Thus, the Goodyear experiment was reduced in scope, tillage was conducted to reclaim the field, and the experiment was restarted with the 2003 cotton season. Because of the difficulties we encountered and to increase our educational outreach opportunities, we started additional experiments at the University of Arizona Maricopa Agricultural Center. The experiments conducted in fall 2002 to fall 2003 are listed below.
At Fast Track Farms (cooperator: Greg Wuertz, Coolidge), the tillage/cover crop treatments were:
–winter fallow; conventional tillage cotton
–winter fallow; conventional tillage cotton with Telone nematicide soil injection, and
–Solum barley cover crop; minimum tillage cotton planting
Treatments at A Tumbling T Ranch (cooperator: Ron Rayner, Goodyear) were:
–fall minimum tillage/wheat grain crop, spring no-till cotton planting
–fall minimum tillage/wheat grain crop, spring minimum tillage cotton planting
Treatments at the Marana and Maricopa Agricultural Centers were the same and were:
–winter fallow, conventional tillage cotton planting in April (early planting)
–winter fallow, conventional tillage cotton planting in late May (late planting)
–Solum barley cover crop, no-till cotton planting in April (early planting)
–Solum barley grain crop, no-till cotton planting in May (late planting).
In addition, a straw management study was conducted at the Maricopa Ag. Center in 2003 that included the following treatments, which were planted following grain harvest:
–winter fallow, conventional tillage cotton,
–Beardless barley cover crop, no-till cotton,
–Cayuse oat cover crop, no-till cotton,
–Solum barley grain crop with straw baled, no-till cotton,
–Solum barley grain crop, cut low (stem stubble 5 inches tall from bed top), no-till cotton,
–Solum barley grain crop, cut at medium height (stems 9 to 10 inches tall), no-till cotton,
–Solum barley grain crop, cut high (stems 17 to 18 inches tall), no-till cotton
The small grain cover crops and grain crops were planted in the fall of 2002: 1) at Coolidge using a conventional grain drill following cotton stalk shredding, and one pass with a Sundance disk bedder/ripper; 2) at Goodyear using a conventional grain drill since the cotton roots were pulled and the entire field was disked following the 2002 cotton season; 3) at Maricopa using a conventional grain drill following disking, listing, and bed shaping (new experiment); and 4) at Marana following cotton stalk shredding but no tillage using a John Deere 1560 no-till grain drill. All cover crops were killed using 40 to 64 oz of Roundup UltraMax (glyphosate) plus ammonium sulfate. The amount of biomass produced by the cover crops ranged between 2,126 and 16,646 lb/A, varying considerably depending on location, number of irrigations, rainfall, year, and when the cover crop was killed with a herbicide (Table 1). For example, the smallest amount of biomass, Coolidge in 2002, resulted from a single irrigation and an early termination whereas the greatest Solum barley biomass was produced with two irrigations plus rainfall and early termination at Marana in 2003 (5,642 lb/A), or with late termination at Maricopa in 2003 (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, 2003) to 2,599 lb/A (Marana, 2002) or 2,773 lb/A (Marana, 2003). The Orita wheat in Goodyear yielded 6,400 lb/A in 2003. A significant finding at Marana in 2003 was that the John Deere 1560 no-till grain drill was able to easily plant the fall 2003 barley crop despite the presence of shredded cotton stalks. The coulter/disk opener assemblies were able to slice through the stalks and place seed in the ground even when a grain drill seed-line coincided with an old cotton seed-line and shredded stalks.
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 preliminary observations confirm 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 stem/tap 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 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 of stopping the production of PM10 dust which is a significant problem in the Phoenix, Arizona area. As a result of our work, we were able to put together funding from outside and within the University of Arizona to purchase a 10-foot wide John Deere 1590 no-till grain drill for research and demonstration purposes. Combined with the use of the Yetter 2976 residue manager/coulter cotton planter attachments, we have demonstrated the successful use of no-till planting techniques for a barley-cotton double crop per year rotation. Our experience in the fall of 2003 irrigating the field at Marana suggests that number of crop cycles that can be grown will depend on maintaining irrigation efficiency. At Marana after two barley-cotton cycles, the head end of the field (i.e., next to the irrigation ditch) has been eroded away and is now 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 and then till and float (or 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 level ground does not compromise grain yields.
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 where the soil is a clay loam, 200 lb/row unit had to be added to the 4-row planter to achieve good operation of the residue managers and soil penetration of the coulter and planter units. At Coolidge and Maricopa where coarse textured soils occur, good soil penetration of the planter units was obtained without adding extra weight to the planters. 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 40,000 to 60,000 plants/A (10 to 15 plants/meter of row on 1 m row spacing) were obtained (Table 2). However, at Marana in 2002, there was significantly less emergence in the conventional tillage, winter fallow, late-planted cotton treatment compared to the other treatments. This was caused by the high air and soil temperatures, which dried out the pre-irrigated seed bed before the germination and emergence were completed despite planting the seed in moisture. This problem was solved in spring 2003 by dry planting the conventional tillage, late plant cotton plots similar to the minimum tillage plots and irrigating to germinate the cotton seed (Table 2). In addition, the plant populations were relatively low at 25,000 to 28,000 plants/A (6.23 to 7.17 plants/m of row) at Coolidge in 2003 (Table 2) and there were significant canopy gaps in the minimum tillage plots. A significant finding at Marana was that the Yetter 2967 residue manager/coulters shattered and moved the old shredded cotton stalks remaining from the 2002 cotton season in addition to handling 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 plot in 2002 because the minimum tillage treatments received more irrigation water (Table 3). 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 (HNR). In Goodyear, the no-till cotton plants were also taller than the plants in the treatment that was disked prior to planting cotton in 2002 but there were no differences in plant heights or HNR in 2003 because the tillage operations were the same for both treatments (Table 4). In Marana, there were differences in plant height related to both planting date (later planted cotton was shorter) and tillage with the no-tilled cotton plots having taller plants in both 2002 and 2003 (Table 5). 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 (Table 6). 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 of course also assessed by harvesting the experiments and comparing cotton lint yields between treatments at Coolidge (Table 7), Goodyear (Table 8), Marana (Table 9), and Maricopa (Table 10). At Coolidge in 2002, the minimum tillage treatments 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, due to the greater amount of irrigation water used in these treatments (Table 7). The reverse was true in 2003 when the minimum tillage treatment yielded 24% less than the conventional tillage treatment yield of 1539 lb/A (Table 7). There were no differences in cotton yields among the tillage systems at Goodyear in 2002 (Table 8) and the 2003 crop has not been harvested as of December 2003 (Table 8). In Marana (2002 and 2003) and Maricopa (2003), there were yield differences between treatments related to planting date with the late-planted cotton yielding less than the early-planted cotton (Tables 9 and 10). 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 (Table 9). 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 feel 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 layby herbicide applications (leaf burn and boll death) may have reduced yields. The injury may have occurred because the plants have more shallow roots in the no-till plots.
A study was conducted at the Maricopa Ag. 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 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 (Table 11). Similarly, cotton plant establishment after no-till planting, cotton plant height, and HNR were the same in all of the treatments (Table 12). Cotton yield was also not different in any of the straw management treatments (Table 13). These results indicate 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.
Evaluate a weed sensing sprayer and a post-emergence herbicide weed control program in minimum-till cotton.
An existing 6-row hooded sprayer equipped with Redball model 410 conservation spray hoods was modified by obtaining two modified Redball 410 hoods and purchasing and installing three WeedSeeker intermittent-spray or automatic spot sprayer units (each with one spray nozzle) from NTech Industries, Inc. in each 28 in wide hood. Thus, in a single pass through the field in no-till or minimum till plots the weed-sensing, automatic spot spray system could be compared to conventional continuous spray technology. Roundup Ready cotton varieties were planted at all experiment sites. A proposed preemergence Prowl (pendimethalin) application was not made at any of the study sites as proposed because the great amount of barley residues and stubble present in the conservation tillage plots was thought to be sufficient to bind and inactivate the herbicide before it reached the soil surface. Thus, weed control in all conservation tillage treatments was obtained using postemergence herbicides and layby herbicide applications.
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 morningglory (Ipomoea spp) control, which was the predominant weed at Marana. The data collect in 2002 and 2003 in Coolidge (Table 14) and in Marana (Table 18) 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 (Table 21). In general the weed control data comparing spray systems collected in 2003 in Marana (Table 20) and Maricopa (Table 23) 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 herbicide that we applied. The Coolidge weed control data comparing conventional continuous spray technology with the weed- sensing, automatic spot spray systems (Table 16) 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 coverage. Weed control evaluations made later in the season at Coolidge (Table 17), Marana (Table 19), and Maricopa (Table 22) 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. The registrations of two new herbicides, trifloxysulfuron and flumioxazin for the 2004 cotton season, should help in this regard.
Evaluate changes in soil properties such as organic matter content, crusting, water infiltration, and associated changes in fertility and irrigation practices.
Soil samples were collected at each site in each plot from the top 12 in of the soil profile at the start of the experiments in the fall of 2001 to evaluate changes in soil properties. Because of the potential for changes in the experiments at the end of the first year of work and because laboratory soil analysis results vary from run to run, the soil samples are being stored so samples can be analyzed simultaneously to determine changes in soil organic matter over time. Soil samples will be collected each fall after cotton harvest to monitor soil organic matter content. As the experiments have been modified or new experiments are established, additional soil samples have been collected and stored. An additional set of soil samples were collected at each site and analyzed for textural properties as part of the irrigation studies.
The Coolidge site contained the greatest amount of sand of three surface irrigated sites (Figure 1). Although there was some variation between depths at Coolidge, overall, the percentages stay fairly constant with clay slightly increasing with depth while sand slightly decreases. With clay contents remaining above 40% in the top 2 ft of the soil profile, the Marana soil contained the highest percent of clay of the experimental sites (Figure 2). The sand and silt contents did vary slightly with 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 would be classified as clay soil. The Goodyear site had a large percent of silt, greater than 50%, throughout the upper 30 inches of the soil profile (Figure 3). The clay content was higher in the top 2 ft 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 a silt loam but, overall, this soil would be classified as a silty clay loam. Clay dominated the top 18 inches of the soil at the Maricopa site (Figure 4). At 24 in., 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. Crusting of the soils did not appear to be a problem at any of the sites based on cotton emergence and stand establishment.
To assess the impacts of minimum tillage on irrigation practice, two major types of analyses were conducted. The first was to assess the impact of the tillage treatment on infiltration. Minimum tillage should enhance and increase infiltration, by leaving old root channels intact allowing the water to flow deeper through the soil vadose. Also, surface trash should help to slow the advance of the water front, giving increased opportunity time. However, in many situations in surface irrigation, increased infiltration may actually hinder the movement of water down the field, causing excessive water to be applied and reducing irrigation efficiency. At Coolidge, Marana, and Maricopa, which were furrow irrigated fields, a furrow infiltrometer was used for infiltration assessment; at Goodyear, a double-ring infiltrometer was used. Due to the similarity in results from the 2002 and 2003 cotton seasons and the previous reporting of results for the 2002 season, only the data collected in 2003 will be reported.
Infiltration measurements for the Coolidge site were taken on May 15, 2003. The results were similar to 2002 with the conservation tillage plots having a much higher infiltration rate (Figure 5). Almost mimicking the 2002 data, the conservation plots averaged just over 10 inches of water infiltrated in a 4-hr 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 tillage plots actually infiltrated greater amounts of water than the conservation tillage plots (Figure 6). The difference was less than 1 inch over the 4-hour measurement period. This data may show the soil’s inherent ability to form deep cracks at the surface that occur during the soil drying. Thus, any additional infiltration created by the no-till practice may be over shadowed by the soils own cracking characteristic. At the Goodyear site, infiltration data were taken but the treatments for all plots were considered the same because deep ripping and land leveling were conducted during the spring of 2003 (Figure 7). As in 2002, the amount of water infiltrated was well below the other experimental sites. The MAC site was added in the fall of 2002 and the infiltration data are shown in Figure 8. Similar to the other sites, the conservation tillage plots infiltrated more water then the conventional tillage plots. For the MAC site, the difference was 2.4 inches during the 4-hour measurement period.
For the field slope and irrigation advance times, 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 as previously discussed, the research plots were moved towards the 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 less than the slope measured in 2003. Advance time measurements were difficult to obtain due to continuous break-overs into adjacent furrows (Fig. 9). 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 allowing for limited comparisons. For example, at the 800 ft. distance, the conventional wheel had arrived in just over 1 hour while the conservation or minimum tillage wheel row took almost 3.5 hours to reach the same distance. Also, the advance times for the two non-wheel rows were virtually the same until the 400 ft. mark when the flows began breaking into adjacent furrows.
The Marana data for 2003 are shown in Figure 10. Elevation data 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 conventional tillage wheel row having the fastest advance time. However, unlike 2002, the conventional non-wheel row was the slowest. These data are in agreement with the infiltration data that showed that the soil’s natural cracking abilities may be compensating for increased infiltration cause by the conservation tillage effects. Deep ripping and tillage might also increase infiltration and advance times in non-wheel furrows where the soil is not compacted.
In Goodyear, data were recorded on 4 plots (Figure 11). Although all of these plots were deep ripped and replaned, there was still some inherent spatial difference. The plots measured averaged 0.06% slope, ranging from 0.04-0.08%. The advance times shown in Figure 11 reflect this with plot 3 and 4 measuring 0.04%, plot 5 measure 0.06% and 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 increase that occurred at the 600 ft mark (the end of the field). This is done at the farm to assure the water doesn’t leave the field. Once the 600 ft. reading was removed, the field had a slope of 0.00007% indicating that it was basically a level field. The advance times recorded (Fig. 12) followed a somewhat expected pattern with the conventional tillage wheel furrows having the fastest advance times, followed by the conventional tillage non-wheel furrow, conservation tillage wheel furrow, and finally the conservation tillage non-wheel furrow that had the longest advance times.
A summary of the irrigation water applied to the cotton in the 2002 and 2003 season is shown in Table 24. In 2002, 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, minimum or 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 advance times and the amount of water applied. At Coolidge, however, the low slope and low flow rate on a sandy soil led to excessive water use. The long set time meant inefficient irrigation, causing an additional 21 inches of water to be applied. At Marana, a high clay content and additional surface trash on the conservation tillage plots did not impact irrigation management. 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 reduced tillage plots. The data collected in 2003 showed similar trends at Coolidge as in 2002 but the amounts of irrigation water applied in the conservation tillage and conventional tillage treatments were similar at Marana and Mariopa. This was probably due to the short length of the fields (i.e., irrigation runs).
To satisfy this objective, additional work will focus on continuing to collect soil samples for determining organic matter content and continuing to measure the irrigation infiltration, advance times, and water use in all of the experiments. These data will provide information for educational purposes and will be used in developing the crop budgets.
Collect and compare operational, agronomic (i.e., plant growth), and cost data for minimum-till and conventional production systems.
Agronomic data were collected at all experimental sites (as shown in the previously discussed data tables) along with the relevant crop production records from both participants and growers. Complete crop production records and other relevant data for the time period from fall 2001 to spring 2003 were sent to our cooperating agricultural economist, Trent Teegerstrom, in November and December 2003, and project participants have discussed various crop production scenarios to guide Trent in the preparation of crop budgets. Partial records for the 2003 cotton season have also been given to Trent. We anticipate that we will have preliminary crop budgets prepared in time for publication in the University of Arizona College of Agricultural and Life Sciences 2004 cotton report. I also anticipate sharing conservation crop budget information with farmers at meetings during 2004.
Disseminate information on alternative production practices.
We have made substantial progress in adapting conservation tillage practices to Arizona conditions and have shared our results with growers at experiment station field days and at Cooperative Extension meetings and workshops for farmers. Specifically field tours were held at the Marana Agricultural Center (June 2003) and at the Maricopa Agricultural center (June and October 2003). One farmer in Marana, Tom Clark, was sufficiently interested such that he borrowed the John Deere 1560 no-till grain drill and planted a 32 acre field with Solum barley following his 2003 cotton crop. 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 are needed to increase the willingness of farmers to try the system. Without a 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.
Impacts and Contributions/Outcomes
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 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 farms in conservation tillage practices. The realization that no-till planting of a grain crop following cotton and irrigation in December will meet pink bollworm control regulations has prompted one grower to try conservation tillage practices and may tempt others to do so in the future. Given the fact that we have been conducting research on conservation tillage practice for only two years, we are encouraged by our progress and look forward to another year of work. In all honesty, there is a steep learning curve for the adoption of conservation tillage practices and as a group we in Arizona are still on that curve.
A Tumbling T Ranch
14929 W. Broadway Road
Goodyear, AZ 85338
Office Phone: 6239321834
Area Agent, Ag. Natural Resources
University of Arizona
Pinal County Cooperative Extension
820 E. Cottonwood Lane, Bldg. C
Casa Grande, AZ 85222-2726
Office Phone: 5208365221
University of Arizona
Dept. of Agricultural & Resource Economics
Tucson, AZ 85721-0023
Office Phone: 5206216245
University of Arizona Maricopa Agricultural Center
Dept. of Agricutural and Biosystems Engineering
37860 W. Smith-Enke Road
Maricopa, AZ 85239-3010
Office Phone: 5205682273
County Agent, Ag. Natural Resources
University of Arizona
Maricopa County Cooperative Extension
4341 E. Broadway Road
Phoenix, AZ 85040-8807
Office Phone: 6024708086
University of Arizona
Dept. of Plant Sciences
Tucson, AZ 85721-0036
Office Phone: 5206211583
Fast Track Farms
505 South Biscane Road
Casa Grande, AZ 85222
Office Phone: 5202510420
John Thude Farms Partnership
33046 W. Barnes Road
Stanfield, AZ 85272
Office Phone: 5204243303