Organic mulches and high residue no-till for collard production in Alabama
A field decomposition experiment was initiated to study the nutrient release rates of organic mulches and forage soybean under tillage versus no-till conditions. Data collection continued on an experiment involving the use of high biomass cover crops in conjunction with organic mulches for the production of no-till fall collards at the Plant Breeding Unit at the E.V. Smith Research Station in S. Tallassee, AL. Data were collected on soil moisture status, weed populations, percent ground cover, mulch nutrient contents and crop yields. Drought conditions prevented stand establishment of the sesame summer cover crop; this treatment will now be considered a no summer cover crop control since the sesame crop has failed for the last two years. Collard seedlings were mulched three weeks after transplanting using locally grown organic mulches. The majority of the collard harvest was donated to the East Alabama Food Bank.
The objectives of the experiment are:
1. To evaluate mimosa prunings, S. lespedeza cuttings and wheat straw as organic mulches in a high residue no-till system; and
2. To compare a high-residue summer cover crop for no-till production of collards and the interaction of cover crop and organic mulch type on assessment parameters.
Mulches and cover crops were evaluated in terms of weed control, percent ground cover, nutrient content, soil moisture status and crop yields.
Winter rye biomass averaged 4.68 tons per acre. Termination of the rye cover crop was attempted without herbicides using crimp and roll operations on April 17, 2007. A poor kill rate necessitated the use of chemical termination before drilling Ethiopian sesame and Derry forage soybean as summer cover crops on May 22, 2007. Establishment of the sesame crop proved problematic due to drought and poor seed viability, despite the use of row cleaners and re-planting on June 1. Since the sesame crop failed two years in a row, that treatment will now be considered as a no summer cover crop control. No attempt will be made to plant sesame during the third and final year of the experiment. Soybean was chemically terminated on August 13 and the residue was crimped and rolled on August 24. Collard transplants were set into this residue on Sept. 11 using a no-till transplanter. Dead collard seedlings were replaced by hand transplanting on Sept. 19. Organic mulches were placed on individual plots on Oct. 1 and 2 at the rate of 3 tons per acre. Collards were fertilized at the rate of 120 lbs N per acre in 3 applications. Harvest was on November 15 with an average yield of 12,121 lbs per acre. Collards that were not used as samples were donated to the East Alabama Food Bank with due credit to SARE. Rye was planted as a winter cover crop on November 28.
Mulches were evaluated in terms of weed control, percent ground cover and soil moisture status periodically from Sept. until November. We will continue to collect data during 2008.
Cover crop treatments will be established around May 7, 2008, after collecting soil moisture, weed population and ground cover data. The summer cover crops will be terminated around July 21, after which weed population, percent ground cover and soil moisture observations will continue. Measurements on these parameters will continue for the duration of 2008. Collard seedlings will be no-till transplanted around August 7 and mulch treatments will be applied around August 21. Collards will be harvested around October 21, followed by a winter cover crop of rye.
More information about this project can be found at
In addition, we also began field decomposition studies using nylon mesh litterbags containing organic mulches and summer cover crops at a rate of 3 tons per acre. The residue is periodically retrieved from the field and analyzed for total C and N, P, K, Ca and Mg to determine mineralization rates of these nutrients under no-till and conventional till conditions.
Impacts and Contributions/Outcomes
A combination of high residue cover crops with in situ organic mulches should provide vegetable growers with multiple benefits, including weed control, improved soil quality and reduced input costs. The selection of collards, mulches and summer cover crops makes this research particularly relevant to growers concerned with reduced-input agricultural systems in the Southeastern region. Research on the decomposition of organic residues under tillage and no-till conditions will supply producers with information on nutrient release rates under various tillage systems.
Auburn University National Soil Dynamics Lab
411 S. Donahue Drive
Auburn, AL 36849
Office Phone: 3348444666
Auburn University Dept. of Horticulture
101 Funchess Hall
Auburn, AL 36849-5412
Office Phone: 3348443050
Auburn University Dept. of Agronomy and Soils
202 Funchess Hall
Auburn, AL 36849-5412
Office Phone: 3348443963