Cover crop composition in long‐term no‐till soils in Semi‐Arid environments do not influence soil health measurements after one year

Abstract

Evaluating the influence of grass or broadleaf cover crops on soil health measurements is common in the U.S Midwest. However, the comparison among different cover crop mixtures, including blends of both grass and broadleaf species is limited. Eleven cover crop experiments were conducted in South Dakota from 2018-2020. Cover crops were planted in the fall after small grains harvest as mixtures of dominantly grasses or broadleaves, a 50/50 grass/broadleaf mixture, and a no cover crop control. Soil and plant surface residue samples were collected in the fall before winter kill and in the spring before cover crop termination and corn planting. Soil samples were analyzed for permanganate oxidizable carbon (POXC), potentially mineralizable nitrogen (PMN), and soil respiration. Cover crops regardless of composition compared to the no cover crop control did not affect fall or spring cover crop/previous crop residue biomass in 7 of the 11 site-years, suggesting growing cover crops may accelerate decomposition of previous crop residue. Cover crops did not improve soil health measurements compared to the no cover crop control or were there differences among cover crop mixtures. Weather and soil properties (precipitation, soil organic matter, and pH) were related to differences in soil heath measurements among site-years. In the first year of planting a multi-species mixture of grasses and/or broadleaves after small grain harvest, growers should not expect to find differences in soil health measurements. Long-term trials are needed to determine whether these different cover crop mixtures over time result in changes in soil health.