Impacts of over-seeding bermudagrass pasture with multispecies cover crops on soil water availability, microbiology, and nutrient status in North Texas

Abstract

Cover crops over-sown into established perennial bermudagrass (Cynodon dactylon) pastures has been effective in improving forage productivity and net farm profitability in wetter grasslands in US. To assess if the use of cover crops can do so in the relatively dry regions of Southern Great Plains of Texas, we evaluated what positive and negative impacts accrue from sowing winter growing mixed species cover crops into bermudagrass pastures by measuring soil water dynamics, soil nutrient and soil microbial dynamics on three separate commercial farms over three growing seasons. There was no evidence that annual, winter growing cover crops reduced soil moisture to negatively affect the following production of the bermudagrass pasture. This result was obtained in years that had average to above average precipitation and may have been different in drier years. At one of the farm sites the key biological function changes we measured positive changes in soil biological activity and fertility to indicate that positive biological changes had taken place and could after more years add up to greater improved outcomes. However, the lack of positive soil biological responses on the other two farms may indicate that soils initially having low soil organic matter, poor permeability, water holding capacity and fertility would need to develop greater levels of soil organic matter with better management before positive responses using cover crops would yield acceptable improvements. However, they are a likely means of contributing to these desired improvements. Cover crop biomass levels were greater on the drill than Broadcast and Control but the improved biomass with broadcasting to establish the cover crops on all three farm sites has important cost lowering implications even though it was applied at a 33% higher seeding rate. It is likely that improved grazing management of perennial pasture is necessary to improve soil organic carbon and soil biological function in conjunction with the use of cover crops.