Extending Cover Crop Growing Window to Improve the Health of Environmentally Sensitive Soils

Sloping and sandy soils are highly susceptible to degradation. The health of these soils could be improved with cover crops (CCs). However, CC effectiveness in improving soil health mainly depends on CC biomass production, which is often low in temperate regions. The question is: how can we increase CC biomass production? Lengthening the CC growing window can be a potential strategy. This study assessed how 1) interseeded and terminated early (2-3 weeks before crop planting) CC, 2) interseeded and terminated late (at crop planting) CC, 3) drilled (after harvest) and terminated early CC, 4) drilled and terminated late CC, and 5) no CC affected CC biomass production, soil properties, and crop yields. The study was conducted in no-till corn-soybean systems in sandy and sloping sites in Nebraska for 4 yr. At the sloping site, drilled CC produced more biomass when terminated late (0.55 vs 0.18 Mg ha-1) than other CC treatments. At the sandy site, both interseeded and drilled CCs produced more biomass when terminated late (1.35 vs 0.27 Mg ha-1) than interseeded when terminated early across the 4 yr. Late-terminated (drilled and interseeded) CCs accumulated more N than the early-terminated CCs. Cover crop impact on soil properties (e.g., particulate organic matter, total C, wet aggregate stability) was small and inconsistent. Additionally, CCs had no effect on crop yields but generally reduced net income. Extending the CC growing window increased CC biomass production, but its soil, crop, and economic benefits were limited after 4 yr. Advisor: Humberto Blanco