CROP PRODUCTION AND SOIL-WATER STORAGE IN LONG-TERM WINTER WHEAT-FALLOW TILLAGE EXPERIMENTS

Soil water is the major limiting factor in dryland crop production in the Central Great Plains. No-till fallow management increases soil wat er storage and reduces soil erosion potential. Two experiments were in itiated in 1969 and 1970 near Sidney, NE to compare effects of moldboa rd plow (Plow), sub-tillage (Sub-till) and no-tillage (No-till) fallow systems on winter wheat (Triticum aestivum L.) grain yield, grain pro tein, residue production, and soil water accumulation during fallow. T he first experiment was established in 1969 on an Alliance silt loam t hat had been previously cultivated prior to study initiation. This exp eriment contained a nitrogen (N) fertilizer split of 0 and 45 (kg N) h a(-1) within each tillage treatment. The second experiment was establi shed in 1970 on a Duroc loam that was in native mixed prairie sod. No fertilizer was applied at this site. At both sites, soil water storage was greatest with the no-till and least with the plow system. Winter wheat grain yields failed to consistently respond to increased soil wa ter storage in the no-till system during the 24-26 years of the experi ments. Grain yields with the plow system were 8% greater than with sub - and no-till systems at the Previously Cultivated site when N was not applied. The addition of N at this site eliminated yield differences due to fallow tillage systems. Grain protein averaged 13.8, 13.3 and 1 2.8% for all plow, sub- and;lo-till treatments, respectively. The addi tion of N at the Previously Cultivated site increased residue dry weig hts by an average of 5% in all tillage systems. Neither grain protein nor residue dry weights were affected by tillage system at the Native Sod site. Winter wheat-fallow is probably not a sustainable production system for the Central Great Plains, regardless of the fallow managem ent system used. (C) 1998 Elsevier Science B.V. All rights reserved.