Effect of tillage and cover crop management practices on nitrogen budget and edamame yield in upland soybean field in Hokkaido, Japan

Abstract

Edamame (Glycine max) growth, yield, and nutrient uptake are influenced by tillage and cover crop management. Unlike the well-studied grain soybean systems, little is known about how tillage and cover crop practices affect nitrogen (N) dynamics and yield in edamame cultivation, particularly under upland and organic farming systems. Therefore, this study was aimed to evaluate the effects of reduced tillage and cover crops on the N budget and edamame yield in upland field in Hokkaido, Japan, from 2021 to 2023. A split-plot design with six treatments was used: conventional tillage with no cover crop, hairy vetch, or rye; and reduced tillage with no cover crop, hairy vetch, or rye. No chemical fertilizers were applied, and cover crops served as the sole N source. Results showed that reduced tillage successfully maintained edamame yields by enhancing surviving plant density, proving it to be a meritorious alternative to conventional tillage. Among cover crops, cereal rye significantly suppressed germination and N accumulation due to high C:N driven immobilization and allelopathic effects. In contrast, while hairy vetch did not provide a significant yield spike over the no cover crop management, it improved the N budget, effectively offsetting N removal from pod harvest. Additionally, returning weed biomass to the field could further support nitrogen cycling in such low-input systems. These findings suggest that while reduced tillage is a viable standalone management choice for maintaining yield, the strategic integration of hairy vetch is essential for stabilizing the N balance in low input systems. These findings are specific to Hokkaido’s cool temperate climate, short growing seasons and caution is required when extrapolating the results to other regions.

The authors' abstract, as published at the source. Soil Science & Plant Nutrition, 2026 · DOI ↗