Fallow Systems for Winter Wheat in Western Nebraska

The need for conservation of soil and water and the energy situation makes it imperative to develop more efficient fallow systems for controlling weeds, to utilize moisture efficiently, and maximize wheat production under limited rainfall. Research was conducted at North Platte and Sidney, Nebr. from 1972 through 1977 to develop a weed control program in a limited and no-tillage winter wheat (Triticum aestivum L.)-fallow rotation. The experimental areas in fallow were sprayed with glyphosate [N-(phosphonomethyl)glycine] at 0.8 kg/ha after harvest to eliminate soil water loss from existing weeds in wheat stubble. Six tillage and/or herbicide treatments were applied to separate replicated plots the first few days of August, October, and April. Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] + glyphosate at 0.8 + 0.8 kg/ha at Sidney and 1.3 + 0.8 kg/ha at North Platte was the most effective fallow weed control treatment but allowed too much weed growth 65 and 77 Mg/ha, respectively. Downy brome (Bromus tectorum L.) control at North Platte was unsatisfactory with August application of atrazine which left 40 plants/m². Russian thistle (Salsola kali L. var. tenuifolia Tausch) and volunteer winter wheat were not always controlled in April by herbicides that were applied in August or October. The earlier the herbicides were applied during the fallow period the sooner subsequently emerging weeds appeared the following spring. Tillage reduced wheat residues 42% at Sidney and 78% at North Platte when compared to the no-tillage plots. April tillage at North Platte had less weed growth because August and October tillage planted volunteer wheat and downy brome. Plots treated with residual herbicides stored 24 and 21% more soil water at Sidney and North Platte than tillage treatments. Wheat yields were increased 11% on no-till plots only at North Platte when compared to tillage. Grain yields were not significantly different when comparing time of initial fallow treatments.