Yield and water use of grain legumes intercropped with spring canola in Eastern Washington

Farmers in the Palouse watershed of Eastern Washington primarily focus on growing wheat but will often rotate with grain legumes and canola. This rotation is profitable and can reduce costs and boost wheat yields. Both legumes and canola have concerning agronomic attributes, such as poor weed competitiveness and the need for additional nitrogen inputs. Intercropping a legume with canola is an attractive option for decreasing inputs and boosting yields. This study reports a 3-year trial in which canola, peas, and chickpeas were grown solely and intercropped (chickpeas/canola and peas/canola). Each treatment was followed by winter wheat. Land equivalency ratios showed moderate overyielding for chickpea/canola (1.15, p = 0.02) and pea/canola (1.14, p = 0.06) intercrops. Canola was the dominant contributor to yield when grown with chickpeas, and peas were more predominant than canola. Analysis of yield components showed that chickpeas grew taller and had fewer branches in the intercrop, suggesting higher plant populations of this species could increase yields due to their smaller size in intercropped conditions. Soil water loss from each treatment was measured at a shallow (0–70 cm) and a deep (70–130 cm) soil depth. Measurements of soil water consumption revealed that sole-cropped peas used the least water, and water consumption ended earlier than other crop treatments. Chickpeas used the most water at a shallow soil depth. Chickpea and canola intercrops depleted more water at the deep soil depth. Intercropping canola with a grain legume increased soil water consumption deeper in the profile compared to the legume alone. Winter wheat yields were unaffected, and grain quality was relatively unchanged by the previous intercrop or sole crop.