Nitrogen placement and tillage effects on dry matter and nitrogen accumulation and redistribution in winter wheat

Nitrogen losses observed with no-till practices when N fertilizer is surface broadcast prompted the need to reassess N fertilizer management practices for winter wheat (Triticum aestivum L.). Field studies were conducted on Renfrow silt loam (fine-silty, mixed, thermic Udertic Paleustolls) from 1990 through 1993 near El Reno, OK, to determine the effects of N placement and tillage on dry matter accumulation, N uptake, and N redistribution in winter wheat. Tillage methods were moldboard plowing and no-till with standing stubble. Fertilizer (60 kg N ha(-1)) treatments were surface broadcast (BR) the same day as seeding, banded (8 to 10 cm below the soil surface) below the seed row (BL), banded between the rows (BT), and no N (control). Fall and spring aboveground dry matter and N were greater in plow ed than in no-till treatments when precipitation was similar to or above the 24-yr average. Leaf N content was 8, 12, and 3% greater in BR, BL, and BT treatments, respectively, than in the control. Nitrogen accumulation rates (g m(-2) d(-1)) in heads from anthesis to final harvest were 0.16 for BR, 0.17 for BL, 0.19 for BT, and 0.13 for the control. Final grain yield and grain N content were not affected by N placement in plowed plots. Under no-till, grain yield was improved by 32% for BL and 15% for BT, and grain N content was increased by 33% for BL and 25% for BT as compared with the BR treatment.