Understanding Time and System Dependent Dynamics of Soil Health.

Conservation agricultural practices like reduced tillage and cover cropping are being used to improve soil health, though there is concern that these practices may reduce crop yields, particularly on shorter time-scales and in cooler/wetter climates. Some farmers have therefore resisted adopting conservation agricultural practices, particularly since indicators of soil health (e.g., increased soil organic carbon) can take years to change in meaningful ways. The objective of this study is to identify soil health indicators that change on seasonal to annual time-scales in case of cover crop and tillage treatment; and to determine how those indicators respond in “soil health building” systems (i.e., soils starting from relatively degraded conditions) versus in “soil health maintaining” systems (i.e., already healthy soils). To understand dynamic changes in soil health parameters we utilized five sets of experimental plots in Virginia. Two locations had previously been in pasture, and thus were hypothesized to represent the highest initial soil health. Two other sites had been in a long-term corn/cover crop rotation with no-till, which we hypothesized to represent moderate initial soil health. The final site had been in potatoes with deep tillage, and was hypothesized to represent poor initial soil health. In all five locations, tillage/reduced tillage and with/without cover crop treatments were tested in a split plot and complete randomized design. Disk harrowing to 25 cm was done in the spring and fall for the “Till” plots. The “With cover crop plots” received a three-way mixture of barley+crimson clover+radish each fall. Summer corn was used as the cash crop for four of the five sites, with tobacco planted in the fifth. Preliminary results indicate that parameters like Substrate Induced Respiration (SIR), Microbial C and Aggregate Stability change on seasonal to annual time scale with cover crop and tillage treatment. These sensitive soil health parameters may respond differently depending on the historical management and initial health of a soil. SIR in particular shows signs of home field advantage based on the history of the plot.