COVER CROP COMPOSITION IN LONG-TERM NO-TILL SOILS IN SEMI-ARID
ENVIRONMENTS DO NOT INFLUENCE SOIL HEALTH MEASUREMENTS
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.