Soil carbon and aggregate stability are positively related and increased under combined soil amendment, tillage, and cover cropping practices

Abstract

Agricultural practices alter the organic carbon dynamics in soil. An experiment was conducted to study the effect of carbon amendments, tillage, and cover cropping on permanganate oxidizable carbon (POXC), total organic carbon (TOC), and wet aggregate stability (WAS) in a 2-year crop sequence (corn–cover crop–cotton–cover crop) at the Texas A&M Research Farm. Two carbon amendments (biochar and composted biosolid) were applied at the rate of 500 kg C ha⁻¹, along with a control. Two tillage practices were evaluated: conventional tillage (CT) and no-tillage (No-Till). A cover crop (CC) mixture of oat, mustard, and pea and no cover crop (No-CC) were also evaluated. Treatments were arranged in a split-split plot design with four replications. Amending the soil with carbon as composted biosolid or biochar affected POXC at both the 0- to 5- and 5- to 15-cm depths. The POXC was significantly higher for the biochar treated plots for corn and CC after corn but significantly lower POXC was observed after cotton with biochar-treated plots. The POXC increased under No-Till compared with CT and CC plots relative to No-CC plots. The TOC was not sensitive to soil management practices. The POXC and TOC both decreased with depth. The WAS greater under No-Till and CC plots. The POXC and WAS were influenced by soil management practices and can be useful indicators to assess short-term soil health improvements. The POXC and WAS were positively related, suggesting that one may be used to predict the other.