Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 26, 2002
Publication Date: September 1, 2002
Citation: NIELSEN, D.C., VIGIL, M.F., ANDERSON, R.L., BOWMAN, R.A., BENJAMIN, J.G., HALVORSON, A.D. INFLUENCE OF ROTATION ON PLANTING SOIL WATER CONTENT AND YIELD OF WINTER WHEAT. AGRONOMY JOURNAL. 2002. v. 94 p. 962-967. Interpretive Summary: Central Great Plains producers exhibit some reluctance to change from the traditional wheat-fallow (W-F) cropping system to systems of more frequent cropping and use of corn (C) and proso millet (M) in rotation with winter wheat. This study was done to quantify the impact that reducing tillage and intensifying cropping system has on wheat yield. Results confirm the greater soil water content at wheat planting and higher wheat yields associated with no-till W-F compared with conventional till W-F. Data are also presented that show no significant difference in water content at wheat planting or yield with either W-C-F or W-C-M compared with W-F no-till. Wheat yields are strongly influenced by amount of available soil water at planting, but in extremely dry years the yield response is only about 30% of the yield response seen in average and wet yields. These results suggest that producers need to monitor soil water at planting and adjust management plans to avoid uneconomical crop yields. The probability of having sufficient soil water to produce a wheat yield of 2500 kg ha-1 is high with W-F no till, W-C-F, and W-M-F systems, but low with the W-C-M system. Producers should have little concern regarding potentially lower wheat yields when moving from W-F to W-C-F or W-M-F.
Technical Abstract: Reduced and no-till dryland cropping systems in the central Great Plains have led to increased precipitation storage efficiency and more frequent cropping than the traditional wheat-fallow system. Many producers express concern regarding the effect that more frequent cropping has on soil water content at wheat planting and subsequent yields. The objectives of this study were to quantify the effects of cropping system on soil water at winter wheat planting and subsequent grain yield, and to determine the frequency of environmental conditions which would cause wheat yield to drop below 2500 kg ha-1 for various cropping systems. The study was conducted over the 1993 through 2001 growing seasons at Akron, CO. Crop rotations evaluated were no-till systems of W-F, W-C-F, W-M-F, and W-C-M, and a W-F conventional till system. Use of conventional tillage resulted in 7.2 cm less soil water at planting in the W-F systems. Lowest water content at planting (10.9 cm) was found in the W-C-M system. Grain yields were correlated with soil water at planting according to the following relationships: kg ha-1 = 373.3+141.2*cm (average and wet years); kg ha-1 = 897.9+39.7*cm (dry years). Increasing cropping intensity to two crops in three years had little effect on water content at wheat planting and subsequent grain yield, while continuous cropping and elimination of the fallow period reduced soil water at planting by 11.3 cm and yields by 450 to 1650 kg ha-1, depending on growing season precipitation. No-till cropping systems which included a 12 to 15 month fallow period prior to wheat planting nearly always produced at least 2500 kg ha-1 of yield when growing season conditions were normal to wet, but no cropping system produced 2500 kg ha-1 when conditions were extremely dry.