Comparison of Soil Organic Carbon Under a Perennial Energy Crop and Bermuda Grass.

Planting dedicated energy crops in agricultural lands as renewable feedstock has aroused much attention recently, due to imminent fossil fuel depletion and energy crisis. Energy crops have been suggested to stimulate soil carbon storage in the form of soil organic carbon (SOC), which would improve soil quality and provide an interim solution to climate mitigation. Increased levels of soil carbon may enable farmers to receive carbon credits, which would make dedicated energy crops economically favorable. The objective of this study is to compare the difference of SOC concentrations under a potential energy crop (giant reed, Arundo Donax L.) and Bermuda grass.

The experiment is conducted in an 85-ac. field located in the Rio Grande river floodplain near Quemado, Texas. The field has mixed acreages of both giant reed and Bermuda grass, resulting from a long-term management practice of giant reed eradication. The topography features of the field were obtained with a survey-grade GPS; and the soil bulk electrical conductivity was obtained with an EM-38 sensor. Based on these spatial data, a stratified sampling scheme was designed to capture the in-field variability of landscape and soil textures. A total of 150 sampling locations were established, with 90 in the giant reed area and the rest in the Bermuda grass area. At each sampling location, a soil core was collected to a depth of 50 cm. These soil cores were cut in three depth layers (0-10, 10-30 and 30-50 cm). For each layer, SOC concentration is determined by subtracting inorganic carbon (modified Pressure Calcimeter method) from total carbon (dry combustion). ANOVA was used to compare the SOC concentration under two crops at each layer and cumulative depths. Preliminary results show for both crops, the surface layer has much high soil organic carbon than the deep layers. Further results will be reported.