Long-Term (24 year) Impact of Cropping Practice on Soil Health and Crop Productivity at a Study in Northern Great Plains.

The Bow Island long-term crop rotation study has been on-going for 24 years in the driest agro-ecoregion of Alberta. Cropping practices evaluated include six crop rotations (wheat-fallow, continuous wheat, wheat-pulse, winter wheat-mustard-fallow, wheat-pulse-fallow and continuous grass), with two to six fertilizer treatments in each rotation.  Management factors that contributed to long-term crop productivity and soil health were determined based on historical yields, soil properties and wheat productivity over all plots in 2016.

Prior crop rotation was the dominant factor affecting soil properties and the 2016 yield of wheat.  Grass substantially increased soil organic matter, but reduced 2016 wheat yield.  Over the whole study period, yields in the wheat-pulse rotation were 10% higher than fertilized continuous wheat if unfertilized and 25% higher if compost was applied.  Annual legumes in the wheat-pulse rotation increased N supply by at least 37 kg N/ha/yr (averaged over whole rotation), while compost substantially increased soil supply rates of P and K.  However, wheat growth following lentil in 2016 was reduced, likely due to carryover of herbicide in a dry spring.  The impact of prior crop rotation on 2016 wheat yields was substantial, but not closely associated with long-term changes in soil properties.