Location: Soil Dynamics Research2008 Annual Report
1a. Objectives (from AD-416)
Develop conservation tillage systems for vegetable production that (1) implement weed management regimes, including cover crops, compost, and mulching; (2) evaluate the biological and economic outcomes of the different systems; and (3) promulgate technology transfer through demonstrations/Field Days and publications for area farmers and agricultural professionals.
1b. Approach (from AD-416)
Specific methods include the following: conservation tillage systems and crop rotations to disrupt weed cycles and enhance competitiveness of crop plant through additions of N-fixing cover crops, such as crimson clover and hairy vetch, planting competitive crop varieties to maintain suppression of weeds, reducing weed seed set through allelopathic effects from crops, such as rye and oats, and improving the advantage of crops over weeds through compost based fertilizer applications. The experimental design includes two main plot treatments (No cover crop and cover crop) and three weed control subplot treatments that include mechanical weeding, herbicide, and mulching. Sweet potato will be tested in rotation with selected high values vegetable crops adapted to the southeastern environmental conditions. A farmer in Macon County has been selected to participate in this research and demonstration project. County extension agents, Tuskegee University researchers, and USDA/ARS scientists will collaborate and provide technical assistance to the farmers and help in disseminating research findings.
3. Progress Report
This report presents results of a five-year study in two Alabama Counties (Barbour and Macon) and evaluated sweet potato root storage yields, soil organic carbon, total nitrogen, and particulate organic matter contents in conventional tillage and no-tillage systems. The treatments evaluated were conventional tillage and no-till with or without cover crops and two fertilizer sources. The results suggested that: a) Rainfall is the most limiting factor in crop production in those two counties. For example in Clayton (Barbour County) no crop was raised in the last three years of the study period because of lack of rainfall; b) Lack of and/or uneven rainfall distribution decreased sweet potato storage root yields throughout the study period; c) With a few exceptions pH was not affected by tillage systems, cover crop, and fertilizer regardless of soil sampling depths. However, over the three-year period, under no-till and conventional tillage, soil pH decreased significantly in the upper 0-5 cm depth but increased below it. In 2003, pH across the field at measured depths (0-1, 1-3, 3-5, 5-10, and 10-15 cm) was 6.8 on an average while in 2007, it averaged 6.3 in the top 15 cm; this corresponded to a small but a statistically significant decrease (p<0.05). d) Adoption of no-till, cover crops and the use of animal manure have all improved soil quality. No-till plots had 20% and 2% more organic C and total N, respectively than conventional-tillage plots at the 0-2 cm soil depth. Soil organic C (SOC) and total N contents decreased with depths with no differences occurring below 5-10, and 10-15 cm. This increase in SOC can be explained by accumulation in the topsoil of organic residues from cover crops and broiler litter that were not mechanically mixed throughout the plow layer in the no-till plots as they were in the conventional tillage plots; e) Particulate organic matter (POM) represented a small fraction of total soil organic matter. No-till plots had higher large particulate organic matter (LPOM) and small particulate organic matter (SPOM) contents in all POM fractions in the surface layer than had the conventional tillage plots. This high LPOM and SPOM contents in all POM fractions can be attributed to a build-up of crop residues and a C retained from broiler litter with the no-till compared with the conventional tillage; f) Finally the study indicated that soil organic matter in Alabama can be increased by up to 30% over a period of five years when farmers shift from conventional tillage methods to no-till system through incorporation of cover crops into crop rotations and amendments with broiler litter. The ADODR has monitored activities via email correspondence and teleconferences.