Multistate, multiseeding rate evaluations of three cool season cover crop mixes: Effects on cover crop performance, soil health indicators, and an analysis of costs

Abstract

Cover crops (CCs) may provide many benefits to cropping systems such as increased soil health, improved soil water infiltration and storage, decreased nitrogen (N) leaching, reduced erosion, and increased weed suppression. Increasing CC biomass is often associated with an increase in these ecosystem services. This research was conducted at five USDA Natural Resources Conservation Service Plant Materials Centers from 2013 to 2016 to investigate the effects of CC mixes and seeding rates on CC performance and measurable soil parameters. In each site-year, experiments were laid out in a randomized complete block design with two-, four-, and six-way species CC mixtures seeded at 215, 430, and 645 seeds m–2. There was no treatment effect detected of CC mixture composition and seeding rate on total soil organic carbon (C), permanganate oxidizable C, Mehlich-III/Olsen phosphorus (P), total soil N, or cash crop yields in any of the site-years. Increasing the number of species in the mix increased CC biomass in 6 of 19 site-years. Increasing the CC seeding rates had a variable effect on CC biomass and biomass N dependent on site-year. An economic analysis revealed an average 260% increase in cost to plant four or six species mixes compared to a two species grass/ legume mix. Increasing the seeding rate from 215 to 645 seeds m–2 resulted in seed costs ranging from US$72ha−1 to US$277ha−1. We conclude that CC mixture composition and seeding rate did not consistently improve CC performance, measured soil parameters, or cash crop yields. Growers should weigh expected benefits versus costs when designing their CC mixtures and determining seeding rates.