Identifying Cropping Sequences for Sustainable Intensification of Dryland Agroecosystem in the Northern Great Plains.

Northern Great Plains of the US has been characterized by cold semiarid climate with less than 250 mm seasonal rainfall. Durum and spring wheat are the main dryland crops of the Western North Dakota and Eastern Montana region, and Wheat – fallow or continuous wheat are the main cropping sequences. In this region, the dryland wheat yield has stagnant at 2 t ha^-1, which may be due to decreased soil health, higher incidence of pests and diseases, and limited improvement in input use efficiency. A study has been initiated at North Dakota State University, Williston Research Extension Center in 2013 to identify best cropping sequences that improve soil health, nutrient and water use efficiency, and assure sustainable yield increment with high economic return. The study consists of five fixed crop rotations comprising of (i) continuous durum; (ii) durum – fallow; (iii) durum – biological primer 1 (a mixed cover crop seeded in late spring) – pea – corn – safflower; (iv) durum – winter wheat/biological primer 2 (a mixed catch crop seeded after winter wheat harvest) – pea/biological primer 3 ( a mixed catch crop seeded after pea harvest) – corn – safflower; and (v) continuous perennial mix. Every year, each phase of every rotation will be included. In addition, there are six durum-based dynamic rotations, where every year cool and warm-season grasses and broad leaves will be chosen on the basis of weather and market conditions. Preliminary results from this year showed that there were significant differences among the treatments for leaf chlorophyll, rooting depth, soil water content, and grain yield of durum wheat.