Effects of tillage practices and crop sequence on spring grain production in the northern Great Plains

Summer fallowing for weed control and water conservation is the most important cultural practice in the northern Great Plains. In an attempt to make more efficient use of plant available water and to better protect the soil surface from erosion, the objective was to evaluate the effects of optional tillage practices and crop sequence in lieu of conventional crop-fallow on the production of spring grains in the northern Great Plains. The study was conducted on a Dooley sandy loam (fine-loamy, mixed Typic Argiboroll) 11 km (7 mi) north of Culbertson, MT. The study was designed as a randomized complete block with four replications. Several tillage practices were tested: Sweep tillage in the fall with spring disking, sweep tillage in the spring, no-till, and conventional fallow-spring wheat rotation. The study included one near-average, two above-average, and two drought years. Spring wheat yields ranged from 725 kg/ha (11 bu/A) on the first treatment in 1984 to about 3500 kg/ha on all wheat treatments in 1986. Conventional fallow-spring wheat rotation, when yields were adjusted for fallowed land, yielded less than annual cropping treatments. There were no statistically significant differences in yield over the five years of the study among annual cropping treatments. Head count was highest on fallowed plots followed by no-till and spring-till plots. Other yield components were similar among treatments as were soil water-use patterns. Including two consecutive drought years out of five years in the study, it appears that annual cropping is practical and profitable in the long-term. If the probabilities of a drought year are high, to maximize profits, summer fallow may be considered. Conservation tillage practices should be followed to adequately protect the soil from erosion.