Tillage and Nitrogen Fertilization Influences on Grain and Soil Nitrogen in a Spring Wheat–Fallow System

Authors

Ardell Halvorson, USDAFollow
Brian J. Wienhold, University of Nebraska-LincolnFollow
USDA, USDA

Date of this Version

2001

Citation

AGRONOMY JOURNAL, VOL. 93, SEPTEMBER–OCTOBER 2001.

Abstract

Spring wheat (Triticum aestivum L.) is generally produced in the northern Great Plains using tillage and a crop–fallow system. This study evaluated the influence of tillage system [conventional-till (CT), minimum-till (MT), and no-till (NT)] and N fertilizer rate (0, 22, and 45 kg N ha^-1) on grain N, grain N removal from cropping system, and changes in residual postharvest soil NO₃–N during six rotation cycles of a dryland spring wheat–fallow (SW–F) cropping system. GrainNconcentration increased with increasing N rate and was higher with CT (33.3 g kg^-1) than with NT (32.3 g kg^-1) at 45 kg ha^-1 N rate. Grain N removal per crop was greater with CT (70 kg N ha^-1) and MT (68 kg N ha^-1) than with NT (66 kg N ha^-1) and tended to increase with increasing N rate, but varied with rotation cycle. Total grain N removal in six rotation cycles was in the order: CT >MT > NT. Total grain N removal by six SW crops was increased by N fertilization, with only 21 and 17% of the applied N removed in the grain for the 22 and 45 kg ha^-1 N rates, respectively. Postharvest soil NO₃–N levels in the 150-cm profile varied with N rate and rotation cycle, with residual NO₃–N increasing during consecutive dry crop cycles. In contrast, some leaching of NO₃–N below the SW root zone may have occurred during wetter crop cycles. Soil profile NO₃–N levels tended toin precipitation during rotation cycles and N fertilization impacted be greater with CT and MT than with NT. Variation in precipitation during rotation cycles and N fertilization impacted grain N removal and residual soil NO₃–N levels more than tillage system within this SW–F cropping system.