Tillage, cover crop, and kill-planting date effects on corn yield and soilnitrogen

Tillage and spring kill date may affect cover crop N accumulation and subse quent N release to the soil, thereby influencing corn (Zea mays L,) N uptak e and yield. We examined the influence of three tillage practices [no till (NT). chisel plowing (CP), and moldboard plowing (MP)I, two cover crop mana gement systems [hairy vetch (Vicia villosa Roth) vs. winter weeds], and two cover crop kill-corn planting dates [early (early April cover crop kill an d mid to late April corn planting) vs, late (mid to late April cover crop k ill and late April to early May corn planting)] on cover crop N accumulatio n, 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)), Co rn yield was higher with late planting in NT than in CP or MP (19.5 vs. 15. 1-16.6 Ms ha(-1)) and higher in CP or MP with early planting than in MP wit h 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 planti ng (217 vs. 133-171 kg ha(-1)), Soil inorganic N (0- to 30-cm depth) at cor n 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 c an be increased by delaying fever crop kill by 2 wk, but corn yield in CP a nd MP can be maintained by killing cover crop early in the spring.