Soil health improvements from using a novel perennial grain during the transition to organic production

Abstract

Organic crop production is a growing part of the agricultural economy. The transition from a conventional to an organic cropping system, while complying with certification guidelines, is financially and logistically challenging for growers. Therefore, it is important to develop strategies, perhaps using novel cropping systems, that can both mitigate economic challenges and quickly improve soil health. We evaluated the impact of perennial and annual cropping systems on soil health during the first two years of a three-year organic transition period at three research stations in Minnesota distinct in climate and soil conditions: Rosemount, St. Paul, and Lamberton. The sites were established in fall of 2017 by planting each of six cropping systems including 1) the novel perennial grain crop intermediate wheatgrass (IWG), 2) alfalfa, 3) an intermediate wheatgrass - alfalfa intercrop (IWGAlfalfa), 4) a winter wheat - red clover (WheatRC) rotation, 5) a corn – soybean (SoyCorn) rotation and 6) a corn - soybean rotation with a cereal rye cover crop (SoyCCorn). We measured root biomass and soil physical, chemical, and microbial parameters to evaluate soil health under the different cropping systems over time. IWG and IWGAlfalfa were consistently among the systems with greater root biomass and larger water stable soil aggregates, while SoyCorn systems had the least. Other soil health variables had site specific responses, with Lamberton and St. Paul the most influenced by cropping systems. At St. Paul and Lamberton soil pH increased in IWG and SoyCorn, and soil K decreased under WheatRC and alfalfa. Labile C and total C and N were not influenced by the different cropping systems. At Lamberton, increases in the biomass of microbial groups including bacteria, fungi, and actinomycetes were observed in IWGAlfalfa. The improvement in some health parameters at one or more sites by IWG and IWGAlfalfa after 2 years of the organic transition period could translate into building longer-term soil health for subsequent organically certified crops, but this is dependent on local soil and other characteristics. It will likely require more time for cropping systems to affect other important soil health parameters such as soil C in the C-enriched loamy soils of Southern Minnesota.