Weeds, Nitrogen, and Yield: Measuring the Effectiveness of an Organic No-Till System

Final Report for GS13-126

Project Type: Graduate Student
Funds awarded in 2013: $10,927.00
Projected End Date: 12/31/2015
Grant Recipient: Clemson University
Region: Southern
State: South Carolina
Graduate Student:
Major Professor:
Dr. Geoff Zehnder
Clemson University
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Project Information

Summary:

Mulches of mechanically terminated winter annual cover crops such as cereal rye (Secale cereale L.) and crimson clover (Trifolium incarnatum L.) can be used as an effective early-season weed management tool in reduced tillage organic vegetable cropping. Previous research in the mid-Atlantic and midwestern USA has identified advantages and drawbacks of “organic no-till” vegetable production, but few studies have been conducted in the warmer southeastern region. The purpose of this study was to examine the effects of tillage [no-till (NT) vs. conventional tillage (CT) of a cereal rye/crimson clover cover crop] and three N fertilization levels on organic tomato (Solanum lycopersicum L.) and summer squash (Cucurbita pepo L.) yield and soil N in two years at the Clemson University Student Organic Farm in Clemson, SC. Squash yields were comparable among tillage treatments in both years. NT tomato yields were 43% greater than CT yields in 2014, whereas CT tomatoes yields were 46% greater than NT yields in 2015. Squash and tomato yields per unit of management labor (time) were significantly greater in NT compared to CT treatments for both years. There were no statistical differences in squash and tomato yields among N fertilization treatments in either year, nor were there significant tillage x N fertilization interactions. 

Introduction

Weed management and the associated labor inputs are consistently some of the biggest challenges to organic crop production (Riemens et al., 2007; Sooby et al., 2007). Organic farmers, out of necessity, rely heavily on soil tillage and other forms of labor-intensive soil cultivation for weed management despite the well-known disadvantages to soil health associated with intensive soil disturbance (Schonbeck and Morse, 2007; Morse and Creamer, 2006).

A small but growing number of organic farmers have begun adopting reduce tillage techniques, which blend the soil-conserving and labor-saving methods of conventional no-till systems with traditional soil building practices (i.e. cover cropping) used in organic production (Leavitt et al., 2011; Mirsky et al., 2013). In organic no-till, an in situ mulch is created by mechanically terminating mature cover crops. Subsequent cash crops are direct seeded or transplanted into the mulch-covered soil. The cover crop mulch manages weeds in place of mechanical cultivation through physical impedance, light interception, and allelopathy (Mohler and Teasdale, 1993; Teasdale and Mohler, 1993; Teasdale and Mohler, 2000).

Despite the demonstrated weed suppression of no-till mulches, organic no-till vegetable production systems have produced mixed results (Delate et al., 2012). Yield reductions associated with no-till mulches were documented in squash (Leavitt et al., 2011), bell pepper (Diaz-Perez et al., 2008; Leavitt et al., 2011), and tomato production (Leavitt et al., 2011). On the contrary, comparable or positive yield responses in organic no-till systems compared to conventionally tilled systems were reported in tomatoes (Abdul-Baki et al., 1996; Madden et al., 2004; Delate et al., 2012).

Common problems researchers have identified regarding organic no-till production include: sub-optimal soil temperatures early in the season and shortened degree growing days caused by the cooling effect of cover crop mulches; loss of earliness due to a lack of synchrony between cover crop maturity and optimal cash crop planting dates; N immobilization when using high C/N cover crops (i.e. rye); increased weed pressure particularly when cover crop stands are inadequate; and reduced N mineralization and poor N synchrony due to a lack of cover crop incorporation (Leavitt et al., 2011; Schonbeck and Morse, 2007; Schonbeck, 2015; Moyer, 2011; Creamer et al., 1997; Morse, 1999; Mirsky et al., 2011; Parr, et al., 2014).

Given the pitfalls and mixed results associated with organic no-till systems, we sought to evaluate an organic no-till system for vegetable production compared to a conventionally tilled system along the following parameters: vegetable yield, soil N, and weed management inputs.

Literature Cited

Abdul-Baki, A., Stommel, J., Watada, A., Teasdale, J., and Morse, R. (1996). Hairy vetch mulch favorably impacts yield of processing tomato. HortScience, 31(338), 340.

Creamer, N. G., Bennett, M. A., and Stinner, B. R. (1997). Evaluation of cover crop mixtures for use in vegetable production systems. HortScience, 32(5), 866-870.

Delate, K., Cwach, D., and Chase, C. (2012). Organic no-tillage system effects on soybean, corn and irrigated tomato production and economic performance in Iowa, USA. Renewable Agriculture and Food Systems, 27, 49-59.

Diaz-Perez, J., Silvoy, J., Phatak, S., Ruberson, J., and Morse, R. (2008). Effect of winter cover crops and no-till on the yield of organically grown bell pepper (Capsicum annuum L.). In R. Prange and S. Bishop (eds.). (Ed.), Proc. XXVII IHC-S11 Sustainability through integrated and organic horticulture. pp. 767.

Leavitt, M. J., Sheaffer, C. C., Wyse, D. L., and Allan, D. L. (2011). Rolled winter rye and hairy vetch cover crops lower weed density but reduce vegetable yields in no-tillage organic production. HortScience, 46(3), 387-395.

Madden, N. M. et al. (2004). Evaluation of conservation tillage and cover crop systems for organic processing tomato production. Horttechnology, 14(2), 243-250.

Mirsky, S. B. et al. (2013). Overcoming weed management challenges in cover crop-based organic rotational no-till soybean production in the eastern United States. Weed Technology, 27(1), 193-203.

Mirsky, S. B., Curran, W. S., Mortensen, D. M., Ryan, M. R., and Shumway, D. L. (2011). Timing of cover-crop management effects on weed suppression in no-till planted soybean using a roller-crimper. Weed Science, 59(3), 380-389.

Mohler, C. L. and Teasdale, J. R. (1993). Response of weed emergence to rate of Vicia villosa Roth and Secale cereale L. residue. Weed Research, 33(6), 487-499.

Morse, R. D. (1999). No-till vegetable production – its time is now. Horttechnology, 9(3), 373-379.

Moyer, J. (2011). Organic no-till farming. Austin, TX: Acres U.S.A.

Parr, M., Grossman, J. M., Reberg-Horton, S. C., Brinton, C., and Crozier, C. (2014). Roller-crimper termination for legume cover crops in North Carolina: impacts on nutrient availability to a succeeding corn crop. Communications in Soil Science and Plant Analysis, 45(8), 1106-1119.

Riemens, M., Groeneveld, R., Lotz, L., and Kropff, M. (2007). Effects of three management strategies on the seedbank, emergence and the need for hand weeding in an organic system. Weed Research, 47, 442-451. 

Schonbeck, M. W. (2015). What is “organic no-till,” and is it pratical? Extension Foundation, eOrganic Community of Practice. Retrieved from https://www.extension.org/pages/18526/what-is-organic-no-till-and-is-it-practical#.VAuqLhar_No

Schonbeck, M. W. and Morse, R. D. (2007). Reduced tillage and cover cropping systems for organic vegetable production. Virginia Association of Biological Farming Info Sheet, 9-07. Retrieved from: http://www.sare.org/Learning-Center/SARE-Project-Products/Southern-SARE-Project-Products/Reduced-Tillage-and-Cover-Cropping-Systems-for-Organic-Vegetable-Production

Sooby, J., Landeck, J., and Lipson, M. (2007). 2007 National Organic Research Agenda. Santa Cruz, CA.: Organic Farming Research Foundation. Retrieved from: http://ofrf.org/sites/ofrf.org/files/docs/pdf/nora2007.pdf

Teasdale, J.R. and Mohler, C. L. (1993). Light transmittance, soil temperature, and soil moisture under residue of hairy vetch and rye. Agronomy Journal, 85(3), 673-680.

Teasdale, J.R. and Mohler, C. L. (2000). The quantitative relationship between weed emergence and the physical properties of mulches. Weed Science, 48(3), 385-392.

 

Project Objectives:

The objectives of our experiment are: 

1. To assess two tillage treatments (no-till and tilled) of a rye and crimson clover cover crop for organic tomato and summer squash production; 

2. To determine the interactions between two tillage treatments and three fertilization treatments (no nitrogen fertilizer, half the recommended rate of nitrogen fertilizer, and full recommended rate of nitrogen fertilizer) as they correspond to tomato and squash yields; and 

3. To evaluate the management costs of a no-till system compared to that of a tilled system.

 

Cooperators

Click linked name(s) to expand
  • Shawn Jadrnicek
  • Dr. Robin Kloot
  • Dr. Dara Park

Research

Materials and methods:

The experiment was initiated in October 2013 at the Clemson University Student Organic Farm, a 5-acre USDA certified organic farm on the Calhoun Field Research Area on Clemson University campus. The soil at the study site is is a moderately well drained Toccoa sandy loam (Coarse-loamy, mixed, active, nonacid, thermic Typic Udifluvents) with an average organic matter content of 4.6%. Although the experiment began in 2013, observations were taken only from 2014 to 2015. The experimental design for both years was a 2 by 3 factorial randomized complete block design replicated three times. The treatments consisted of two levels of tillage [no-till (NT) and conventional tillage (CT)] of a cereal rye/crimson clover cover crop biculture and three levels of N fertilization (0, 58, and 116 kg ha-1 N) for tomato and summer squash production. Conventional tillage was accomplished with a disk harrow to a depth of 15 cm. The recommended N fertilizer rate (116 kg ha-1) was based on Clemson Agricultural Service Lab soil fertility recommendations from a standard soil analysis of composited 0-15 cm soil samples taken in March 2014 from the year one experiment site. In 2014, soil at the experiment plot was amended with P (from 0-10-0 bone meal) at a rate of 448 kg ha-1 and K (from 0-0-50 potash) at a rate of 60 kg ha-1 according to soil test recommendations. No P and K amendments were needed in 2015. The treatments were arranged in a split-split plot design. Tillage treatment split plots (6 m x 7.5 m) were established for each vegetable crop with 2 m alleys between each plot. Alleys were flail mowed, tilled, and planted to a buckwheat (Fagopyrum esculentum) cover crop in both years. Split-plots were divided into three split-split plots (vegetable rows) spaced 1.5m apart for the N fertilization treatment. The treatments were replicated three times for each vegetable crop.

On 4 October, 2013 and 13 September, 2014 experiment plots were seeded with a mixture of cereal rye (VNS) and crimson clover (VNS in 2013 and ‘Dixie’ in 2014) using a tractor-mounted overseeder attachment with 10 cm row spacing. Two-year cropping history for the 2014 experiment plot included maize (Zea mays) and summer squash cash crops and Japanese millet (Echinochloa esculenta), sunn hemp (Crotalaria juncea), cereal rye, crimson clover, and cowpea (Vigna unguiculata) cover crops. The 2015 plot cropping history included garlic (Allium sativum), carrot (Daucus carota), cole crops (Brassica oleracea) and beet (Beta vulgaris) cash crops and cereal rye, crimson clover, cowpea, and sudex (Sorghum bicolor × S. bicolor var. sudanese) cover crops. Prior to cover crop seeding, the plots had been disked to remove weeds and level the field. In 2013, a seeding rate of 112 kg ha-1 rye and 39 kg ha-1 clover was used. The high rate of clover was due to calibration problems with the overseeder’s seed shoot. In 2014, the same rate of rye was used, but the clover rate was reduced to a more appropriate rate of 12 kg ha-1. Cover crops in CT plots were flail mowed on 5 May, 2014 and 6 May, 2015 and the plots were disked repeatedly the following day in both years to incorporate cover crop residue. NT termination was accomplished on 6 May, 2014 and 11 May, 2015 with a rear-mounted 2.4 m I & J (Gap, PA) roller-crimper that had been filled with 225 kg of water for a total weight of 860 kg. The drum could have accommodated more water, but the tractor’s lifting capacity was a limiting factor. In both years crimping was done in one direction with roughly 0.3 m of roller-crimper overlap with each pass. In 2014, the initial round of crimping did not fully terminate the rye crop, which by 7 May, had begun to rebound. The NT plots were re-crimped on 8 May with a small-plot 0.7 m roller-crimper mounted to a two-wheel walk-behind tractor. (The farm’s larger category 1 tractor was not operational at the time.) An additional 113 kg of weight was added to the small-plot crimper for a total weight of 230 kg. In 2015, two back-to-back passes with the 2.4 m roller-crimper were made over the cover crop (same direction) on 11 May to ensure adequate rye termination. At time of crimping, the rye had reached Zadoks stage 69 (anthesis complete) in 2014 and stage 75 (medium milk) in 2015. Crimson clover maturity was not noted in either year. 

Five-week old ‘Celebrity’ tomato and two-week old ‘Success’ squash seedlings were transplanted by hand in the corresponding CT and NT tomato and squash plots on 09 May, 2014 (both crops) and on 14 May (tomatoes) and 18 May (squash) in 2015. Vegetable plots consisted of three rows 4.5 m in length with 0.3 m spacing between plants and 1.5 m spacing between row centers (Figure 1). Drip irrigation was installed on top of mulch in NT and on bare soil in CT prior to transplanting; plants were watered immediately after transplantation. In the NT plots, the cover crop mulch was spread 12-15 cm apart by hand creating a narrow planting slit in the row prior to transplanting. The mulch was then pushed back against the plants after transplantation to cover the soil surface. All plants had been started in the farm’s greenhouse using on-farm generated potting soil [50% compost (2, 0.02, and 0.02 kg t-1 N, P, and K, respectively): 25% perlite: 25% peat moss] with 120 ml lime and 710 ml powderized 8-5-5 feather meal fertilizer added per 0.3 m3 of potting soil mix. Tomatoes were seeded in 128-count seed trays and then transplanted after 3 weeks into grow out pots measuring 10 cm in diameter. Squash were seeded in 72-count seed trays. Squash seedlings had reached the second true-leaf stage prior to transplantation. All vegetable transplants were fertilized with a powderized 8-5-5 feather meal fertilizer while in the greenhouse and were hardened off prior to transplantation. Immediately after transplantation, plants were fertilized according to N fertilization treatment with a side-dressed split application of a slower release, pelletized 13-0-0 feather meal fertilizer. A second split application of 13-0-0 was made at flowering stage for each crop. Tomatoes were trellised using the “Florida weave” technique. 

Cover Crop Data 

Aboveground cover crop biomass was sampled in three 0.5m2 quadrants in 2014 and five 0.5 m2 quadrants in 2015 from the alleys between vegetable plots immediately prior to CT plot flail mowing. The biomass samples were oven dried for 72 hrs at 55°C and then weighed. Additionally, subsamples from each biomass sample were sent to the Clemson University Agricultural Service Lab where they were dried at 70-80°C for 12-24 hrs, ground to pass through a 2 mm sieve, and analyzed for total N by combustion using a LECO® FP528 Nitrogen Combustion Analyzer. Cover crop N contribution to the following vegetable crops was estimated as 0.40 × total cover crop biomass × cover crop %N (Baldwin and Creamer, 2006). Four weeks after termination, NT plots were assessed visually for percentage cover crop regrowth (Leavitt et al., 2011). 

Weeding and Labor Inputs 

CT plots were weeded approximately every 1-2 weeks in 2014 and approximately every 2-3 weeks in 2015. Weeding in tilled plots consisted of rototilling, flame weeding, and hand hoeing. NT plots were weeded every 2-3 weeks in both years. Weeding in NT plots consisted of rotary and string mowing weeds that had emerged through the cover crop residue and hand-pulling of perennial weeds. Weed management labor (hours) was recorded for each vegetable crop by tillage treatment for both years. Additionally, a visual assessment of all NT plots was made 6 weeks after crimping to estimate average percent ground coverage by weeds (Creamer et al., 1997). Labor (hours) spent preparing no-till (crimping) and tilled (mowing + disking) cover crop plots prior to transplanting was also recorded both years.

Soil Analysis 

On 9 May, 2014 and 13 May, 2015, prior to transplantation of vegetable crops and N fertilization, six 0-15 cm soil samples were taken from each of the CT and NT vegetable split-split plots and composited by row. Another round of sampling, same protocol, was done at the end of the each growing season on 30 July, 2014 and 31 July, 2015, respectively. Subsamples from all soil samples were sent to the USDA-ARS Grassland Soil and Water Research Laboratory, Temple, TX for soil health analysis using the Soil Health Tool (SHT) ver. 4.4. (Haney, n.d.) The samples were dried at 50°C, ground to pass through a 2 mm sieve, extracted with DI water and H3A, and analyzed on a Seal Analytical rapid flow analyzer for NO3-N and NH4-N according to the methods of Haney et al. (2008). The water extract was analyzed on a Teledyne-Tekmar Apollo 9000 C:N analyzer for water-extractable organic C and total N and 40 g of each dried soil sample was re-wetted with DI water and incubated with a Solvita® paddle in a 237 ml glass jar for 24 hours (Haney et al., 2008). At the end of 24-hour incubation, the paddle was removed and placed in the Solvita® digital reader for CO2-C analysis. The SHT couples inorganic N (NO3-N and NH4-N), water-extractable organic C and N, and CO2-C measurements to estimate plant available N in the soil. 

Vegetable Yield 

Yield data (weight) were recorded for marketable tomatoes (USDA grades 1-3) and marketable squash (USDA grades 1 and 2) in each row for every harvest (USDA 1997a, 1997b). Squash were harvested 3-4 times per week and tomatoes 2-3 times per week in both years. In 2015, leaf tissue samples (excluding petioles) were taken from the most recently mature leaf of each plant in every row for both crops at early the early flowering stage. Samples were composited by row and sent to the Clemson Agricultural Service Lab where they were dried at 70-80°C for 12-24 hrs, ground to pass through a 2 mm sieve, and analyzed for total N by combustion using a LECO® FP528 Nitrogen Combustion Analyzer. 

Statistical Analysis

Statistical analyses were performed with analysis of variance (ANOVA) using the Fit Model procedure of JMP® (version 11.0) to determine the effects of tillage and N fertilization on vegetable yield and soil N. Fisher’s least significant difference tests (Ρ≤0.05) were used to separate means. To compare inputs between the two tillage treatments, an analysis of labor was compiled by recording the total labor hours required to prepare the seedbed for planting and manage weeds during the vegetable growing season for each crop (Leavitt et al, 2011). Additionally, an ANOVA was performed to determine the effects of tillage on vegetable yield per unit of labor.

Literature Cited

Baldwin, K. and Creamer, N. (2006). Cover crops for organic farms. North Carolina Cooperative Extension Service # E06-45788. Retrieved from: http://content.ces.ncsu.edu/cover-crops-for-organic-farms.pdf

Creamer, N. G., Bennett, M. A., and Stinner, B. R. (1997). Evaluation of cover crop mixtures for use in vegetable production systems. HortScience, 32(5), 866-870.

Haney, R. L., n.d. Soil health tool (SHT) ver 4.4: an integrated approach to soil testing. Retrived from: http://www.nrcs.usda.gov/wps/PA_NRCSConsumption/download/?cid=nrcseprd333873&ext=pdf

Haney, R. L., Brinton, W. H., and Evans, E. (2008). Estimating soil carbon, nitrogen, and phosphorus mineralization from short-term carbon dioxide respiration. Communications in Soil Science and Plant Analysis, 39(17-18), 2706-2720.

Leavitt, M. J., Sheaffer, C. C., Wyse, D. L., and Allan, D. L. (2011). Rolled winter rye and hairy vetch cover crops lower weed density but reduce vegetable yields in no-tillage organic production. HortScience, 46(3), 387-395.

USDA. 1997a. United States standards for grades of tomatoes. Effective 1 Oct. 1991. USDA-AMS, Washington, D.C.

USDA. 1997b. United States standards for grades of summer squash. Effective 6 Jan. 1984. USDA-AMS, Washington, D.C.

Research results and discussion:

Results

Cover crops 

Cover crop biomass averaged 8,400 kg ha-1 in 2014 and 8,960 kg ha-1 in 2015. Based on the average total N content of the cover crop samples, 1.74% (2014) and 1.72% (2015), total cover crop N content was approximately 146 kg ha-1 in 2014 and 154 kg ha-1 in 2015. Total N contribution to the vegetable crops (0.40 × total cover crop biomass × cover crop %N) we estimate was 58 kg ha-1 (2014) and 61 kg ha-1 (2015). Cover crop regrowth at 4 weeks after termination was minimal (<1%) in both years. Roller-crimping provided adequate control of cover crops (Figure 2). 

Weeding and Labor Inputs 

Seedbed preparation labor was higher both years in CT plots. Mowing + disking required 191% and 300% more labor in 2014 and 2015, respectively, compared to NT roller-crimping. Managing weeds was also more labor-intensive in CT plots. Weed labor was 400% and 338% greater in CT tomato and squash plots, respectively, compared to NT plots in 2014. In 2015, weed labor was 45% greater in CT tomato plots compared to NT; squash plot weed management was comparable between tillage treatments. NT cover crop plots did become weedy later in the season particularly in 2014 when regrowth of the previous summer’s cover crop (Japanese millet) required routine mowing to keep the millet from overwhelming the NT plots (Figure 3). Average percent ground cover by weeds at 6 weeks after termination in NT plots was 35% (tomatoes) and 25% (squash) in 2014 and 10% (tomatoes) and 10% (squash) in 2015. 

Soil Analysis 

Pre-season analysis

Average plant available N and total N were significantly greater (≤ 0.05) in NT tomato plots compared with CT in 2014. There were no significant differences in available and total N between tillage treatments in 2015. There were no significant differences in tomato plot CO2-C in either year. Average plant available N and total N in squash plots were not statistically different between tillage treatments for either year studied. Average squash plot CO2-C was significantly higher (≤ 0.05) with NT in 2014 but similar between tillage treatments in 2015. 

Post-season analysis

Tomato plant available N and total N were statistically comparable both years regardless of tillage treatment. Average CO2-C was significantly higher (≤ 0.05) in 2014 with NT but comparable between CT and NT in 2015. Average plant available N and total N were significantly greater (≤ 0.05) in NT squash plots in 2014 and in CT plots in 2015. Average CO2-C was significantly higher in CT squash plots in 2015. Based on post-season analysis, fertilization treatments did appear to significantly affect plant available N, total N, or CO2-C in either year for either crop studied nor were there significant tillage x fertilization interactions. 

Leaf Tissue N

Average leaf tissue total N values were statistically comparable between tillage and fertilization treatments for both crops in 2015. Average %N for both CT and NT were within the 3.5-5.0% sufficiency range for trellised tomatoes (Campbell, 2000). Based on mid-season analysis, there appeared to be no effect of either tillage or fertilization on leaf tissue N. 

Vegetable Yield 

Average NT tomato yields were significantly greater (≤ 0.05) than CT yields in 2014; in 2015 CT yields were significantly greater (≤ 0.05) than NT. Squash yields were comparable between tillage treatments for both years studied. Fertilization treatments did not significantly affect vegetable yield in either year for either crop studied nor were there significant tillage x fertilization interactions. Vegetable yields per unit of labor (seedbed preparation + weeding) were significantly greater in both NT crops in both years studied.

Discussion 

The significant reduction in CT tomato yield in 2014 was likely due to disease. CT tomatoes were severely damaged by a combination of Southern blight (Sclerotium rolfsii) and Pythium root rot (Pythium spp.). Plant pathogen diagnosis was confirmed by the Clemson University Plant Problem Clinic. Both pathogens thrive in moist conditions found in poorly drained sites (Kluepfel et al., 2014). Because of the no-till component of the study, we did not create raised beds in either tillage treatment. The roller-crimper, we found, provides optimal cover crop termination on level terrain, although there are roller-crimping devices designed for use in raised-bed systems (Reberg-Horton et al., 2012; Moyer, 2011). Normal farm CT practices include post-tillage raised-bed making to improve field drainage for cultural management of soil-borne diseases. In all, roughly 14% of the CT tomato plants in 2014 were lost to disease, which impacted average row yields. However, when row yield data were transformed from yield per row to yield per plant (by dividing row yields by number of plants per row) and analyzed using the same statistical model, there were no significant differences between tillage treatments (data not shown). NT tomatoes, oddly enough, remained disease free in 2014, which was notable because: 1) CT and NT crops were grown in spatially similar parts of the field; 2) soil conditions with high levels of available carbon (e.g. poorly decomposed mulch and plant tissue) such as those found in reduced tillage systems are conducive to Southern blight (diagnostician’s notes). A field with slightly better natural drainage was used in the second year of the study and both CT and NT crops remained disease free in 2015.

N levels were high across all treatments each year. N fertility treatments had no significant effect on vegetable yield. Thus, soil N was likely not a limiting factor in either year probably as a result of high soil organic matter content and residual N from previous cover crops. Plant available N, total N, and CO2-C were generally higher in soil from the 2015 site.

Seedbed prep and weed management labor were much higher in CT plots in 2014 compared to 2015. Mowing and incorporating the cover crop residue took longer in 2014. More in-field tractor turns and repositioning were required in 2014 during mowing and subsequent tillage because of plot proximity to adjacent crop fields. Regarding 2015, roughly 75% of the cover crop at the study site (visual estimation) was lodged by severe rain and wind events three weeks prior to cover crop termination. At termination, approximately 20% of the cover crop stand in CT plots remained lodged – only 20% of the crop was left standing at its original height. The lack of a fully erect cover crop made mowing less time intensive in 2015. Regarding in-season weeding, field conditions in 2014 were generally wetter in the first several weeks of the vegetable-growing season compared to 2015. In 2015, there were no rain events for the first 2.5 weeks after transplanting, which decreased the amount of early-season weeding that had to be done in CT plots after transplantation. 

Literature Cited

Campbell, R. C. (2000). Sufficiency ranges for plant analysis in the southern region of the United States. Southern Cooperative Series Bulletin #394. Retrieved from: http://www.ncagr.gov/agronomi/saaesd/scsb394.pdf

Kluepfel, M., Blake, J. H., Keinath, A. P., and Williamson, J. (2014). Tomato diseases and disorders. HGIC #2217. Retrieved from: http://www.clemson.edu/extension/hgic/pests/plant_pests/veg_fruit/hgic2217.html

Moyer, J. (2011). Organic no-till farming. Austin, TX: Acres U.S.A.

Reberg-Horton, S. C. et al. (2012). Utilizing cover crop mulches to reduce tillage in organic systems in the southeastern USA. Renewable Agriculture and Food Systems, 27(1), 41-48.

 

Participation Summary

Educational & Outreach Activities

Participation Summary

Education/outreach description:

An overview of the study, tour of the no-till research plots, and a roller-crimper demonstration were provided as part of a cover cropping and organic no-till strategies for weed management workshop for farmer and extension agents held at Clemson University in May 2015.

Project Outcomes

Project outcomes:

We demonstrated that roller-crimped no-till mulches provided adequate early-season weed suppression in both years and saved considerable weed management and seedbed preparation labor. Further, the higher yields per unit of labor input we found in both years with no-till compared to conventional tillage highlight the potential for production cost savings using organic no-till methods. Overall, the results demonstrated that organic no-till is a viable method for reduced tillage summer vegetable production in the South Carolina Piedmont region. 

Farmer Adoption

Our research demonstrated that organic no-till is a viable method for summer vegetable production in the southeastern U.S. Some important factors that should be considered when attempting organic no-till (based on our lessons learned over two growing seasons during this study and other on-farm no-till experimentation): 1) Establishing dense cover crop stands in the fall and timely mechanical termination in the spring are fundamental to the success of system; 2) Earliness to market is impacted by later maturing over-wintered cover crops (i.e. VNS rye) which delay vegetable transplantation until late spring in this region; and, 3) High biomass no-till mulches do provide, as we demonstrated, adequate early-season weed control, but weed management will likely become more difficult as mulches begin to breakdown later in the growing season.

Recommendations:

Areas needing additional study

One drawback to organic no-till is weediness later in the growing season, which we experienced particularly in year one of the study. Repeated hand weeding of no-till plots can be especially labor intensive and could negate the early-season weed management cost savings realized with no-till mulches. We found adequate weed management later in the growing using string and rotary mowing to keep emerged weeds managed but not necessarily controlled. Other on-farm no-till weed managment research at the Student Farm (not associated with this study) has explored adding off-farm mulches (e.g. leaf litter) to in-situ mulches for longer season summer vegetable production (eggplant and peppers) in an attempt to compensate for inadequate no-till mulch biomass caused by the decomposition of no-till mulches over the course of the growing season. How to effectively/economically manage weeds in organic no-till vegetable production remains a vexxing problem that is worthy of further research. 

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.