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North Carolina State University (2004)

Production and Use of Compost and Vermicompost in Sustainable Farming Systems in North Carolina and in a smallholder subsistence farming system in semi-arid West Africa

McClintock, Nathan C.

Titre : Production and Use of Compost and Vermicompost in Sustainable Farming Systems in North Carolina and in a smallholder subsistence farming system in semi-arid West Africa

Auteur : McClintock, Nathan C.

Université de soutenance : North Carolina State University

Grade : Master of Science (MS) 2004

Résumé
Compost use in agriculture has gained popularity in recent decades as public concern over the environmental impact of synthetic inputs in agriculture has increased. Compost application has been associated with improvements to soil physical and chemical properties. Thesis research focused on compost production and utilization in an organic farming system in North Carolina and in a smallholder subsistence farming system in semi-arid West Africa. Part 1 : An experiment was conducted at the Center for Environmental Farming Systems (CEFS) in Goldsboro, NC, to compare methods of composting separated solid swine waste and various rates of wheat straw. Straw was chopped (<10 cm) or unchopped and mixed with manure at five different rates and placed in piles (1m³) for composting. Sub-samples of each mixture were stocked with earthworms (Eisenia fetida) for vermicomposting. After 3 weeks, additional sub-samples were removed from piles and stocked with worms. At Weeks 3, 6, and 10, chop significantly affected C and N concentrations and C:N ratios in both vermicomposting treatments, generally in high-straw mixtures. By Week 13, chop was no longer significant. Overall, worms were not able to degrade straw fractions of mixtures that were not pre-composted. Part 2 : An experiment was conducted at a site in the North Carolina Piedmont (Pittsboro) and another in the Coastal Plain (Goldsboro) to evaluate the integration of compost with cover crops, both common sources of fertility in organic farming systems. Treatments were : poultry litter compost (COMP), crimson clover (CLOV), clover + compost (MIX), and a control fertilized with soymeal (SOY). COMP and CLOV plots were also amended with soymeal to equalize N rates across treatments. Treatment differences did not affect sweet corn height at 5 or 7 weeks after planting (WAP) or biomass (DM) accumulation at 5 WAP at either site. At Goldsboro, CLOV yielded 22% more DM at harvest than COMP and 31% more marketable ears. Total yield of COMP plots was 22% less than CLOV while marketable yield was 20 to 31% less than CLOV, MIX, or SOY treatments. Release of plant available nitrogen (PAN) from decomposing clover (C:N 11.1) may have been slower than from compost (C:N 8.1) or soymeal (C:N 6.2), coinciding with the period of maximum uptake by corn plants. Soil inorganic N (SIN) concentration was greater at Pittsboro, likely due to method of incorporation (roto-tilled vs. disked) and soil type. In a lab incubation of both soils (and which did not include soymeal), SIN in Goldsboro MIX treatments was greater than the sum of CLOV and COMP SIN, suggesting a priming effect, likely masked by soymeal in the field experiment. Part 3 : The Jóór (Dior) soils of Senegal’s Peanut Basin are inherently low in OM, limiting yields of millet and other crops and threatening the food security of smallholders. A series of focus groups and interviews were conducted in eight villages to characterize the site-specific fertility management practiced by farmers in the Peanut Basin. On-site measurements revealed little significant difference between the effects of compost and manure on peanut and millet growth, but significant increases over unamended areas. Similarly, chemical analysis revealed increased cation exchange capacity and nutrient concentrations in soils amended with compost or manure. Similarities in the chemical characteristics of compost and traditional pile manure (sëntaare) suggest that development workers could emphasize improved pile management rather than promoting more labor-intensive composting.

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