Cover crops may exacerbate moisture limitations on South Texas dryland farms

Abstract

Cover crops are a sustainable management tool for mediating weed pressure, reducing soil erosion, and enhancing soil organic carbon (C) and nitrogen (N) levels. Yet, adoption rates across water-limited farms in Texas remain low, especially among producers without irrigation access, due to concerns that cover crop use of soil moisture will negatively impact subsequent cash crop yields. This three-year cover crop trial in a rain-fed sorghum (<i>Sorghum bicolor</i> L.) farm in Lyford, Texas, trialed different cover crop mixes and seeding rates and confirmed that cover cropping leads to significant soil moisture deficits and cash crop failure when rainfall is low between cover crop termination and cash crop planting (&lt;30 mm). In seasons one and three, moisture deficits contributed to significantly lower germination of post–cover crop sorghum compared to fallow control plots. In season two, increased precipitation during a longer moisture recharge period between cover crop termination and cash crop planting helped avoid sorghum yield drops. Length of recharge period, amount of rainfall, species selection, planting density, and termination method are major determinants of subsequent cash crop outcomes. Careful management can minimize some of the risks cover cropping poses to soil moisture, but without reliable rainfall at key points in the cropping cycle, cover cropping remains risky for farmers without irrigation access.