NITROGEN FERTILIZATION AND ROTATION EFFECTS ON NO-TILL DRYLAND WHEAT PRODUCTION.

Authors: Halvorson, Ardell; Nielsen, David; Reule, Curtis

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2004
Publication Date: 7/23/2004
Citation: Halvorson, A.D., Nielsen, D.C., Reule, C.A. 2004. Nitrogen fertilization and rotation effects on no-till dryland wheat production. Agronomy Journal. 96:1196-1201.

Interpretive Summary: No-till (NT) production systems, especially winter wheat-summer crop-fallow, have increased considerably in the Central Great Plains region during the past decade, but few N fertility studies have been conducted with these systems. Therefore we studied the response of winter wheat (W) to N fertilization rate in two NT dryland crop rotations, wheat-corn-fallow (WCF) and wheat-sorghum-fallow (WSF), on a Platner loam soil for 9 years. Five N rates, 0, 28, 56, 84, and 112 kg N ha-1, were applied to the same plots for each crop in the rotation. Wheat total biomass and grain yield response to N fertilization varied with year but not with crop rotation. Yields increased with N application each year, with maximum yields being obtained with 84 kg N ha-1 over all years. Based on grain N removal, nitrogen fertilizer use efficiency varied with N rate and year, averaging 86, 69, 56, and 46 % for the 28, 56, 84, and 112 kg ha-1 N rates, respectively. Grain quality as indicated by protein content increased with increasing N rate. Residual soil NO3-N generally increased with increasing N rate after the initial N fertilizer application. Precipitation use efficiency increased with N addition. A soil plus fertilizer N level of 124 to 156 kg N ha-1 was sufficient to optimize winter wheat yields in most years in both rotations. Application of more than 84 kg N ha-1 on this Platner loam soil, with a gravel layer below 120 cm soil depth, would more than likely increase the amount of NO3-N available for leaching and potential for groundwater contamination. Wheat growers in the central Great Plains need to apply N to optimize NT dryland wheat yields and improve grain quality in wheat-summer crop-fallow systems, but need to avoid over fertilization with N.

Technical Abstract: No-till (NT) production systems, especially winter wheat (Triticum aestivum L.)-summer crop-fallow, have increased in the Central Great Plains, but few N fertility studies have been conducted with these systems. Therefore, winter wheat (W) response to N fertilization in two NT dryland crop rotations, wheat-corn (Zea Mays L.)-fallow (WCF) and wheat-sorghum (Sorghum bicolor L. )-fallow (WSF), on a Platner loam (fine, smectitic, mesic Aridic Paleustolls) was evaluated for 9 years. Five N rates, 0, 28, 56, 84, and 112 kg N ha-1, were applied to each rotation crop. Wheat total biomass and grain yield response to N fertilization varied with year but not with crop rotation, increasing with N application each year, with maximum yields being obtained with 84 kg N ha-1 over all years. Based on grain N removal, nitrogen fertilizer use efficiency (NFUE) varied with N rate and year, averaging 86, 69, 56, and 46 % for the 28, 56, 84, and 112 kg ha-1 N rates, respectively. Grain protein increased with increasing N rate. Residual soil NO3-N generally increased with increasing N rate after the initial N fertilizer application. Precipitation use efficiency (PUE) increased with N addition, leveling off above 56 kg N ha-1 application rate. A soil plus fertilizer N level of 124 to 156 kg N ha-1 was sufficient to optimize winter wheat yields in most years in both rotations. Application of more than 84 kg N ha-1 on this Platner loam soil, with a gravel layer below 120 cm soil depth, would more than likely increase the amount of NO3-N available for leaching and groundwater contamination. Wheat growers in the central Great Plains need to apply N to optimize dryland wheat yields and improve grain quality, but need to avoid over fertilization with N to minimize NO3-N leaching potential.