Intensified Dryland Cropping Systems for Southern Montana.

This study evaluated the impact of various crop sequences on the overall agronomic and economic viability of various crop sequences as compared to a traditional winter wheat/fallow. The design is a randomized complete block, with four replications. There are eight different crop sequences including winter wheat/fallow as the standard dryland rotation for the region. Other crops included spring wheat, lentil, spring pea, and camelina. All phases of each crop sequence were present each year. The year 2012 was the fourth full year of this study.

Growing conditions for the years 2009-2011 all had above average precipitation compared to the long-term norm for southern Montana.   Comparing yields following different previous crops, winter wheat yields were greatest following a lentil cover crop, but these yields were not significantly different when following fallow. When winter wheat was in a continuous crop system, grain yields were significantly reduced by about 20%.

Soil water use of spring crops such as lentil and spring pea was less than winter or spring wheat. Soil water use by camelina was similar to that of spring wheat. Adequate weed control can be achieved in all rotations except camelina where no broadleaf herbicides are registered. Economic analysis showed an advantage to continuous crop production for specific rotations. For example a winter wheat/spring wheat/lentil rotation improved net return by approximately 13% over wheat/fallow, when averaged over three years. As a general rule rotations that had winter wheat equal to or greater than 50% of the time were generally economically feasible. When the occurrence of winter wheat in the rotation dropped below 50%, the economics of the alternate crop rotation were less favorable.