Tillage, Cover Crop, and Kill‐Planting Date Effects on Corn Yield and Soil Nitrogen

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Abstract
Tillage and spring kill date may affect cover crop N accumulation and subsequent N release to the soil, thereby influencing corn (Zea mays L.) N uptake and yield. We examined the influence of three tillage practices [no till (NT), chisel plowing (CP), and moldboard plowing (MP)], two cover crop management systems [hairy vetch (Vicia villosa Roth) vs. winter weeds], and two cover crop kill–corn planting dates [early (early April cover crop kill and mid to late April corn planting) vs. late (mid to late April cover crop kill and late April to early May corn planting)] on cover crop N accumulation, soil inorganic N, and silage corn N uptake and yield. An experiment was conducted on a Dothan sandy loam (fine‐loamy, siliceous, thermic, Plinthic Paleudults) from 1997 to 1999 in central Georgia. Cover crop N accumulation was higher with late kill than with early kill (113 vs. 104 kg ha−1). Corn yield was higher with late planting in NT than in CP or MP (19.5 vs. 15.1–16.6 Mg ha−1) and higher in CP or MP with early planting than in MP with late planting (18.1–18.4 vs. 15.1 Mg ha−1). Similarly, corn N uptake was higher in NT with late planting than in CP or MP with early or late planting (217 vs. 133–171 kg ha−1). Soil inorganic N (0− to 30‐cm depth) at corn planting was higher in CP than in NT (18.4–30.2 vs. 9.9–20.5 mg kg−1). Corn yield and N uptake in NT and N concentration and uptake in CP and MP can be increased by delaying cover crop kill by 2 wk, but corn yield in CP and MP can be maintained by killing cover crop early in the spring.