Enhancing Sustainability in Cotton Production through Reduced Chemical Inputs, Cover Crops, and Conservation Tillage

Enhancing Sustainability in Cotton Production through Reduced Chemical Inputs, Cover Crops, and Conservation Tillage

Summary

We are evaluating the impact of cover crops integrated with conservation tillage to improve economic returns and reduce environmental impact in cotton production systems. Improvement in nutrient availability, increased crop production, enhanced above and belowground biological diversity, and reduction of chemical inputs and plant parasitic nematodes are being used to evaluate positive economic and environmental impact of conservation management. Companion studies were initiated to identify cover crops with the most potential to produce biomass, enhance biological diversity and reduce threat of plant parasitic nematodes. Results to date indicate there is a positive impact of Rye + Legume cover crop on above and below ground biological populations. Research has and will continue to be presented at on-farm field days, conservation tillage meetings and other professional meetings.

Objectives/Performance Targets

1. Investigate how management to enhance insect habitat affects key interactions among aboveground insects (predator/prey relationships) and changes in soil biological activity, and in soil chemical and physical characteristics.

   Educate producers about environmental and economic benefits of soil quality in sustainable agriculture systems and expand the network of area producers who provide leadership for further adoption and dissemination of information on sustainable production practices.

Accomplishments/Milestones

Cover crops were established successfully for the second year during fall 2001 on three farms near Tifton, GA and three farms near Bartow, GA. The fourth farm in the Tifton area was not planted to the specified cover crops (Clover and Rye) and was placed into a peanut rotation for the 2002 growing year. Cover crop biomass was determined from all fields prior to killing the cover crops for cotton planting in April 2001 and March 2002. In Tifton, biomass of Rye + Legume Blend and Blend were greatest in April 2001, however in March 2002 Rye biomass exceeded all other treatment biomass by more than 35%. In Bartow, Rye + Legume Blend biomass exceeded biomass in all other treatments in both years.

Cover crop companion studies to evaluate additional varieties of rye, clover and vetch and several mixtures of legumes were conducted at Tifton, Fort Valley and Watkinsville locations. Evaluations were made on biomass production as well as function as beneficial insect habitat. Twenty-two treatment combinations were tested. Three sets of harvest data were collected at Fort Valley. The rye variety, Wrens Abruzzi, provided highest biomass yield during each harvest date. Balansa clover failed to produced. Among legume cover crop mixtures, two clover only treatments provided highest biomass yield in harvest 1, while two different mix treatments of clover and vetch were highest during harvest 2 and 3. Among single legume treatments, highest biomass yield in harvest 1 and 3 was produced by Crimson clover and in harvest 2 Hairy vetch was highest. Lowest biomass yield among rye plots were produced by AC RT 178 in harvest 1 and AC-Rifle in harvest 2 and 3. Also, these two rye cover crops produced lowest plant height. Among single cover crop treatments, percent flowering was best for Crimson clover, Early Crimson, and Wrens Abruzzi, while Cahaba vetch and AC RT 178 produced the worst. Wrens Abruzzi produced highest stand percentage, while Ball clover produced lowest. Data on insect populations is currently being analyzed.

Cotton planting was successful on all fields located near Bartow, GA. Three producers in the Tifton area remained with the study and planted cotton for the 2002 growing season; planting was delayed on only one of the producers’ fields. Cotton biomass was evaluated twice during the growing seasons, in July and September 2001, and in June and August 2002. Cotton biomass production in the Tifton area was greatest in the fields planted with Rye and Rye + Legume Blend in September 2001 and June 2002. Biomass data is currently being analyzed for the August 2002 sampling. Biomass production in the Bartow area early in the season for both years was initially greater in the no-cover and Rye cover crop fields. By September 2001, cotton biomass production in the Clover and Rye + Legume Blend cover crop fields was greater by 10% to 30% over the no-cover and Rye cover crop fields, however, in August of 2002 the no-cover field produced 20% or more cotton biomass than all other cover crop fields. Nutrient content (carbon, nitrogen and sulfur) of cover crop and cotton biomass is currently under analysis.

Deep soil samples were collected from all fields at the end of cover crop season April 2002, and at the end of the cotton season October 2002. Evaluation of soil C and microbial biomass will be continued on all the samples collected.

During the 2001 and 2002 cotton growing season soil samples were collect three times to evaluate changes in soil biota in the Blend and Rye+Legume Blend sites of the Ponder, Thompson, and Branch fields. The sample dates represent 1) end cover crop/pre-cotton crop season (May 2001, March 2002), 2) middle of cotton season in August, and 3) end cotton season in November. Results from the first year indicated seasonal changes in abundance and diversity of mites relating to soil moisture. In this first year Prostigmata were the most abundant across all fields and seasons, on average making up greater then 40% of the community. Astigmata and insects, exclusive of Collembola, were rare, generally less than 5% of total abundance. Abundance and diversity of microarthropods were highest in mid-season samples. Abundances of all microarthropod groups were greatest in the Blend in the pre-season, greatest in the Rye+Legume Blend fields mid-season, and apparently not different between cover crop fields in end-season samples. Preliminary results from the first year were presented at the Southern Conservation Tillage Conference for Sustainable Agriculture to be held in Auburn, summer 2002. Samples collected in 2002 are currently being analyzed.

Beneficial and pest insect numbers were determined once or twice weekly on the fields in sweep net and whole plant samples. Identification of insects is ongoing and population dynamics continue to be evaluated. Insect diversity and population density of pests and predators collected in the fall 2000 were presented at the Southern Conservation Tillage Conference for Sustainable Agriculture to be held in Auburn, summer 2002. High numbers of natural enemies were observed in cover crops and in cotton fields in which cover crops were grown. In the Bartow area samples for 2002, all beneficial species except Orius were more prevalent in the Blend and Rye + Legume Blend treatments and this trend carried over to the cotton plants in these treatments as the year progressed. These species may be remaining in the plots that they first colonized, or they may find some other properties of the cotton plant or microenvironment more suitable in these plots. Although there were higher numbers of thrips in the Blend and Rye + Legume Blend covers, the number of thrips in the cotton was only higher in the Rye + Legume Blend treatment, suggesting that leguminous covers do not affect the distribution of thrips on the cotton plant. Although ants and aphids were also higher in the Blend and Rye + Legume Bend covers, there was no relationship to this distribution on cotton plants as the year progresses. The trend observed in beneficial species where numbers were higher in fields with clover was similar to the findings reported last year for the Tifton area fields.

Large populations of Meloidogyne incognita were found in several of the fields in the Tifton area. As reported last year, there was no effect of cover crop on densities of M. incognita, based on analysis of variance (P = 0.158). In a recent greenhouse experiment, we found that most of the legumes (clovers and vetches) tested were good hosts for the southern root-knot nematode. Rye, Cahaba vetch, and Cherokee red clover were relatively poor hosts for nematode reproduction. Rye and Cahaba vetch produced less than 10% of the eggs on Hairy vetch whereas Cherokee red clover produced 14 to 25% of the eggs on Hairy vetch. If growers are concerned about the southern root-knot nematode, then winter cover crops of either Rye, Cahaba vetch, or Cherokee red clover should have a lower risk of building up damaging nematode populations than nematode-susceptible legume crops.

Our first Field Day event was held April 4th 2001 at the Jefferson County Extension Office in Louisville, GA. The following talks were presented: “SARE Research Overview”; “Cover Crop Effects on Recruitment and Retention of Beneficial Insects in Cotton Fields”; “Cover crops and nematodes in cotton cropping systems”; “Is your system of production building soil quality?”; “Cover crops and soil fertility: what changes do you need to make?”; “Farm Suite – A whole farm planning system to reduce risk”. A field trip to one of the producer sites was also made. Participants included county extension agents, researchers, students, and producers and land managers representing close to 10,000 acres of land in production. A preliminary survey was conducted to assess producer knowledge and interests. Results of the survey indicated 1) top issues of concern for producers were crop yields and pest and weed control, 2) producers desire to learn more about soil quality, and 3) many attendees associate soil organic matter as a major component of conservation tillage management.

We are planning on presenting posters at the Soil Ecology Society Meeting in Palm Springs, CA in spring 2003, and at the Southern Conservation Tillage Conference for Sustainable Agriculture to be held in College Station, TX, summer 2003.

The project will continue through the cotton-growing season of 2003 at new field sites near Perry and Moultrie, GA. The companion studies in Fort Valley, Watkinsville, and Tifton, on rye, vetch and clover varieties will also be continued. Field studies of soil and insect components will continue through that time. Alternative cover crop mixtures will be suggested in the final year of the study. We will continue to present information at field days and grower meetings.

Impacts and Contributions/Outcomes

Although this is the second year of the project impacts are still limited, as much of the data needs to be processed. Positive outcomes that we have observed so far are that pesticide use may be decreased in fields containing clover varieties where natural predator populations are high. In cases where root knot nematode is a concern, however, we would recommend the use of a rye, vetch or Cherokee red clover variety/mixture as a cover crop. We continue to hope that cover crop use will increase as a management practice that can improve soil productivity and reduce erosion. On the positive, side our first Field day indicated a great interest in conservation management issues.

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