Increased winter-killed cover crop seeding rate may not increase soil health outcomes

Implementing soil conservation practices can begin to restore degraded soils, improve soil health, and increase overall ecosystem services. Cover cropping is an effective strategy to rebuild soil quality through decreased erosion and increased residue inputs, which can help build soil organic matter. Cover crop seeding rate may have a positive relationship with ecosystem services; however, it is unknown whether this is realized at or below the recommended cover crop seeding rate. The goal of this study was to identify the relationship between cover crop seeding rate and soil health biogeochemical measures across the growing season using five oat (Avena sativa L.)–pea (Pisum sativum L.) cover crop treatments of 0%, 25%, 50%, 75%, and 100% the industry standard seeding rate at the University of Massachusetts Amherst Research Farm. Soils were tested for soil carbon (C), nitrogen (N), and microbial measures at winter kill, spring thaw, post-planting, and succeeding cash crop harvest. Soil measures did not vary among seeding rates, but total ground cover was consistent among treatments due to weed growth. Soil health measures vary seasonally reflecting soil microbial activity. Our study provides initial evidence that soil biogeochemical responses do not respond to increased seeding rate within one growing season when the resulting groundcover—cover crop biomass plus weeds—is consistent across seeding rates, but sampling date can influence the magnitude of soil biological and chemical soil health metrics.