1a. Objectives (from AD-416):
Evaluate the long-term effect of soil organic carbon (SOC) on soil quality: 1)To determine the amount and types of carbon accrued in long-term field plots; 2)To evaluate the effects of tillage practice, winter cover cropping, compost application, soil depth and soil aggregate size fraction on total SOC and SOC constituent contents; 3)To relate total SOC and SOC constituent contents with soil structural stability and erodibility; 4)To determine total SOC content level and constituents most effective at increasing soil stability and reducing soil erodibility; and 5)To identify agronomic practices that effectively increase soil stability and decrease erodibility.
1b. Approach (from AD-416):
Soil quality will be evaluated in university controlled long-term piedmont and coastal field plots that have treatments of no-tillage, no-tillage with winter cover and compost, disk tillage, and disk tillage with winter cover and compost. In each treatment, SOC will be analyzed for particulate carbon, labile carbon, microbial biomass, total soil carbohydrates, and glomalin. SOC components will be related to mineralization, respiration, and aggregate stability. Testing for aggregate stability include wet sieving, dry sieving, and rainfall simulation of selected aggregate sizes analyzing runoff and splash.
3. Progress Report:
This research is directly related to inhouse objective 2 - a multi-year switchgrass field study revealed that switchgrass significantly improved soil organic carbon contents in profiles down to three feet deep. Annual soil coring in the field over four years revealed that soil organic carbon contents doubled in concentration within one year of production and were maintained throughout the four year study. Switchgrass production can improve soil carbon sequestration while also providing above ground biomass for bioenergy production. Long-term impacts of tillage and row crop management on soil organic carbon levels: After decades of conventional tillage practices using typical row crops in sandy coastal plain soils, their organic carbon contents have declined. A side-by-side comparison study after 34 years showed continual increase in soil organic carbon levels under conservation tillage; conservation tillage promotes slow carbon accumulation (< 0.1% per year at 0-4 cm depth). Maintaining these long-term tillage plots is of immense scientific value for climate modelers because it provides field data on rates of carbon lost and accumulated and shifts in soil health.