Improving fall vegetable crops and soils with summer cover crops

Improving fall vegetable crops and soils with summer cover crops

Summary

The influence of summer cover crop systems on fall/winter organic vegetable crops for local sales will be studied in field studies. Southern soils have high organic matter oxidation rates and are generally low in organic matter; often less than 1 percent. The NOP states that farmers must implement practices that improve or stabilize soil health (USDA, 2007). Important measures of soil health include soil bulk density, aggregation, soil organic matter, microbial biomass and activity, and soil friability, structure, nutrient concentration, and buffering capacity. Numerous reports of the benefits of cover crops have been published over the years and the use of cover crops is increasingly important in order to enhance sustainability of organic production systems. Louisiana, Mississippi and surrounding states are seeing a large increase in demand for local produce. Increasing crop productivity outside of the summer season would improve availability of produce, increase grower income, and enhance the value of farmers markets to their communities. In addition to four cooperating universities, we have agreements from two grower cooperators (one in each state) for on-farm summer cover crop and fall/winter vegetable research. Two university sites will include six cover crops planted with four replicates at each location the first year (2010). Fall vegetable crops (lettuce, cabbage) will be planted into the plots after incorporating the summer cover crops in the fall. Vegetable crop yield and quality, total crop biomass, weed and pest pressures will be documented. Experiments at two farm sites will compliment the university sites, but with some flexibility in design and layout as needed for the farming system in place. Research designs and protocols will be approved for statistical validity and relevance to the objectives by the LSU Department of Experimental Statistics. Soil and tissue data will be gathered to determine aspects of nutrient and carbon dynamics in the systems and soil health, soil biological activity and nutrient analysis will be measured. Organic cover crops and vegetable crops production budgets will be generated based on the project research. The research will be presented at workshops and field days, through extension and scientific outlets and the programs will be available to agriculture professionals participating in SARE PDP programming. A grower advisory panel will be initiated as the first step of the project to formulate specific project objectives and the on-farm and university organic research and outreach activities of the investigators. The advisory panel will meet at a minimum twice a year to discuss progress of the project activities. Invitations to join the advisory committee will be open to all organic growers, both certified and not certified as many growers have elected not to become certified at this time. Aggressive and multifaceted outreach tools, including internet-based, live, and traditional media/teaching and extension programming, will be used to bring results and information from the project to as many audiences and end users as possible.

Objectives/Performance Targets

Determine the relative productivity and soil building properties and soil health of summer cover crops in Gulf Coast organic farming systems.

Determine the influence of summer cover crops on subsequent vegetable crop productivity.

Enhance the knowledge base of area outreach and educational professionals serving the needs of organic and similarly minded farmer-marketers in the Gulf States.

Develop production budgets for the various summer cover crop treatments and the fall organic vegetable crops.

Objectives at Mississippi are the same as Louisiana

Accomplishments/Milestones

Sunn hemp (Crotalaria juncea) and sesame (Sesamum indicum), cover crops were planted at two timings during the summer in Baton Rouge, Louisiana. Sunn hemp (44 kg.ha-1) and sesame (5.5 kg.ha-1) were broadcast at recommended rates on June 10 (early planting) and July 17, 2010 (late planting) into 3.7 by 18.4 m plots using untreated seeds. After planting seeds were incorporated using a fence harrow. Plots received no irrigation, fertilizer, or pesticides prior to or during growth. On September 15, 2010 a 1 m2 area of cover crop and weed shoot mass was sampled and soil sampled. Cover crop plots were harvested by a forestry cutter, flail mower, and then incorporated by multiple passes of a disk harrow.
Stand establishment was good for all of the plots and weeds were less than 5 % of total biomass in all plots. Cover crops height was highest for the early planted Sunn hemp (3.3 m), compared to late Sunn hemp (2.4 m) and early planted sesame (2.4 m) plot while the late sesame plot was the shortest (1.9 m). Total fresh weights were highest from the early planted sesame and Sunn hemp (1.96 kg.m-2 and 1.92 kg.m-2, respectively) while the dry weight of the early planting of Sunn hemp (0.56 kg.m-2) was greater than the other cover crops treatments. There were no differences in soil organic matter or soil nutrient status at cover crops harvest.
Cover crop plots were divided into 3 sub-plots 6.0 meters long receiving two rates of composted chicken litter organic fertilizer (166 and 332 kg N per ha) and an unfertilized control. Cabbage was machine transplanted into bareground plots at a 30-cm in-row spacing in December 2010. The cabbage plots received an initial sidedress application of fish emulsion (1-4-0) after transplanting as well as overhead supplemental irrigation when needed. Pest management was accomplished by an application of B. thurigiensis and weed control through cultivation and hand weeding of plots.
A summer cover crops screen was planted into raised bed plots with four replications. Cover crops (31) were hand broadcast at recommended rates on July 22 into 2.4 by 6.0 m plots using untreated seeds. After planting seeds were incorporated using a soil cultivator (Lilliston). Plots received no irrigation, fertilizer, or pesticides prior to or during growth. When the individual cover crops reached full flowering, a 1 m2 area of cover crop and weed shoot mass was sampled and the cover crop and weed biomass calculated. There were significant differences in total biomass between cover crop treatments as well as weed control in the plots.

In Mississippi the stand establishment of the main cover crops experiment was poor and no data was available for the experiment. The failure of the main trial in 2010 led to some slight changes for the 2011 trial, including the introduction of initial irrigation to assure a stand. The summer cover crops screen was conducted in Mississippi with the trial sown on July 23, 2010 into a tilled field. Thirty-one entries, including legumes, grasses, and other crops, were tested in triplicate in a randomized complete block design. Plots were not watered from sowing until termination, and deer predation was heavy on several of the legumes. Each plot was harvested at early to mid-flowering, except those that did not flower during the trial period. These were harvested at the final harvest date or not harvested at all. Harvest dates were Aug. 27, Sept. 22, and Oct. 19. There were significant differences among the harvested entries in the screening trial, several traditional and non-traditional summer cover crops performed well. In 2010, Alcorn State University screened approximately a dozen cover crops, planting replicated plots in 25 m2 plots in August at the campus in Lorman. Very dry weather reduced stands significantly, but the trial site provided a good introduction to cover crops at a late August field day.

Impacts and Contributions/Outcomes

The PI’s met in Mississippi to discuss the project objectives, goals and formulate specific actions and activities. Growers in Louisiana and Mississippi were identified in each state to participate on the project committee. In Baton Rouge, an intern was recruited to participate in the study and trained in the conduct of scientific research. In addition, an undergraduate student was trained in the scientific method during the fall semester. A presentation with the intern as a co-PI along with a research associate is planned for presentation at the annual meeting of the American Society of Horticultural Science (ASHS) as well as the southern region ASHS. Abstracts are forthcoming for both presentations. A presentation is planned for the Mississippi Vegetable Growers meeting and on-site grower demonstrations will be conducted in 2011. Screening trial data were presented at the 2011 Southern Region – American Society of Agronomy Meeting in February 2011. Skills developed from these trials have also lead to establishment of winter cover crop trials in high tunnels in Mississippi. More than 200 direct contacts saw the trial in Mississippi, and more than 1,000 additional indirect contacts saw the trial site during the 2010 Fall Flower & Garden Fest in Crystal Springs, Mississippi. There were 300 direct contacts at the Alcorn University field day. Visitors learned about different cover crops and principles of establishment. The trial increased the knowledge base of the investigators and the staff, and served as a foundation for work in 2011. The research and outreach efforts will continue concerning the use of summer cover crops in a fall organic vegetable crops management system in both Mississippi and Louisiana.

Collaborators: