Tillage and clover cover crop effects on grain sorghum yield and nitrogen uptake

ABSTRACT:

Winter annual legumes double-cropped with grain sorghum (Sorghum bicolor L. Moench) can potentially provide nitrogen (N) for the sorghum and enhance long-term sustainability. A 4-year experiment was conducted near College Station, Texas, to evaluate conventional disk tillage, no-till, and green manuring for their potential in grain sorghum production. Annual clovers were used in combination with both no-till and green manure methods, which were compared to conventional disk tillage without clover. Fertilizer rates of 0 and 60 kg N ha⁻¹ (54 pounds/acre) were used on all treatments. The green manure treatment with no added N produced higher grain yields than the similar conventional disk tillage treatment in 3 of 4 years and was statistically equal to conventional disk tillage receiving 60 kg N ha⁻¹ (54 pounds/acre) in 3 of 4 years. Yields from no-till treatments without N fertilizer never matched those from conventional disk tillage treatments with fertilizer. Green manuring of clover prior to sorghum planting apparently better approximated clover N mineralization to sorghum demand, resulting in greater grain production. Grain sorghum no-till planted into clover surface mulch cannot be recommended because N availability was not synchronous with plant demand.