How changes in cover crop termination timing affect soybean yield? A systematic review and meta-analysis

Introduction: Cover crops (CCs) are widely adopted in the United States for their benefits, such as improving nutrient retention, soil stability, and weed control. However, some of the effects of CC termination timing on soybean productivity remain uncertain. Objectives: This study aimed to evaluate the influence of CC termination timing on soybean yield through a systematic review and meta-analysis of 50 studies conducted in the US over the past decade. Methods: A meta-analysis was performed to assess CC effects across regions, focusing on variables such as CC family, termination timing, method, and local environmental conditions, including precipitation and soil pH. Results: In the Midwest, Poaceae (e.g., cereal rye, Secale cereale) reduced soybean yield, while legumes increased yield by up to 22.4%. In the South, CC effects were neutral. Mid-April termination improved yield by up to 12% for maturity groups I–III, which consist of short-cycle cultivars that reach maturity faster for harvesting, allowing for efficient resource use. In contrast, late termination (April–May) reduced yield by 4.5% for maturity groups IV–V, which have longer growth cycles. Late planting accelerates flowering of soybean cultivars of groups IV–V, shortening the growth cycle and reducing yield. Furthermore, rainfall limitations in late plantings may be more intense when cultivars with longer cycles are planted due to the arrival of autumn, harming grain filling and, consequently, yield. Chemical termination in mid-April increased yield by 38%, whereas mechanical methods negated this effect. Precipitation (∼1500 mm) and soil pH above 6.11 were key factors enhancing CC benefits Conclusion: These findings highlight the importance of adjusting CC termination timing and methods based on soybean maturity group and regional environmental conditions to optimize productivity and maximize the benefits of CC practices.