Cover Crop and Composted Municipal Sludge Effects on Soil Physical Properties and C/N Sequestration In a Coastal Plain Soil Under Conservation Tillage.

Uncertainty exists concerning the impact of cover crops and application of composted municipal sludge with conservation tillage on the total agricultural environment. A study conducted by USDA-ARS and the University of Georgia assessed the effects of cover crops on soil physical properties and C/N sequestration in a sandy coastal plain soil. The randomized study involved application of composted municipal sludge (3-3-3) to cash crops (cotton or eggplant) followed by cover crops (rye or crimson clover). Saturated hydraulic conductivity, bulk density, and soil moisture retention were measured on soil samples collected twice each year from each plot. The cores for soil physical property measurements (7.6 cm diameter by 7.6 cm height) were collected from each replicated plot both between rows (interrow) and within the row using an impact type sampler which minimized disturbance. Microbial biomass C (MBC) and N (MBN), extractable C, potentially mineralizable C (PMC), total C, and total N were measured on core samples (2.5 cm diameter) of the top 2.5 cm of soil collected four times per year. Analyses of variance for soil physical properties showed that study day * sampling position (row or interrow) and study day * treatment (cover crop, row crop, and compost) were statistically significant for soil moisture retention and bulk density. For saturated hydraulic conductivity there were statistically significant effects for study day * sampling position and treatment. Measurements of MBC, MBN, Extractable C, PMC, total C and N all showed that over time there was a positive response to application of the composted municipal sludge. Overall the study showed positive effects on both soil physical properties and C/N sequestration from application of composted municipal sludge and use cover crops on a sandy coastal plain soil.