Cropping system effects on sorghum grain yield, soil organic carbon, and global warming potential in central and south Texas

M. N. Meki, A. R. Kemanian, S. R. Potter, J. M. Blumenthal, J. R. Williams, and T. J. Gerik

Agricultural Systems (May 2013)

DOI: 10.1016/j.agsy.2013.01.004

There is an increased demand on agricultural systems in the United States and the world to provide food, fiber, and feedstock for the emerging bioenergy industry. The agricultural intensification that this requires could have positive and negative feedbacks in productivity and the environment. In this paper we used the simulation model EPIC to evaluate the impact of alternative tillage and management systems on grain sorghum (Sorghum bicolor L. Moench) production in central and south Texas and to provide long-term insights into the sustainability of the proposed systems as avenues to increase agricultural output. Three tillage systems were tested: conventional (CT), reduced (RT), and no-tillage (NT). These tillage systems were tested on irrigated and rainfed conditions, and in soils with varying levels of structural erosion control practices (no practice, contour tillage, and contours + terraces). Grain yield differed only slightly across the three tillage systems with an average grain yield of 5.7 Mg ha−1. Over the course of 100-year simulations, NT and RT systems had higher soil organic carbon (SOC) storage (100 and 91 Mg ha−1, respectively) than CT (85 Mg ha−1), with most of the difference originating in the first 25 years of the simulations. As a result, NT and RT systems showed lower net global warming potentials (GWPs) (0.20 and 0.50 Mg C ha−1 year−1) than CT (0.60 Mg C ha−1 year−1). Irrigated systems had 26

keywords: Grain sorghum; Sustainability; Soil organic carbon; Global warming potential

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