Soil Physical C Sequestration in Response to Tillage and Crop Rotation.

Particulate organic matter (POM) is an important source of labile C and N protected by soil aggregates. A randomized block design in 2 (tillage system) x 3 (crop rotation) factorial arrangement was laid-out to evaluate the impact of tillage and crop rotation (1990 to 2007) on POM and POM associated C and N fractions. Tillage treatments (conventional tillage, CT and no-till, NT) were factored into continuous corn, corn-soybean, and corn–soybean-wheat-cowpeas rotation. Ten soil cores were collected at 0-7.5, 7.5-15, 15-22.5 and 22.5-30 cm), 2-mm sieved, and analyzed for POM, POM associated C and N, total C, pH, and bulk density (rb). Results showed that POM and POM associated C and N varied significantly by tillage and soil depth interaction. The POM, POM-C and POM-N increased significantly by NT compared to CT. However, crop rotation only influenced the POM-C. The CC had higher POM-C than CS and CSW. The POC significantly decreased with increasing soil depth under both tillage and crop rotation. NT x crop rotation had higher POM, POM-C ad POM-N fractions than CT x crop rotation. Continuous corn under NT significantly increased the POM-C in soil.