Yield, nitrogen, and phosphorus uptake, and biological nitrogen fixation in chickpea–flax intercropping systems in southern Saskatchewan

The interest in growing pulse crops and oilseeds together as intercrop combinations is increasing. However, little is known about nutrient dynamics in pulse–oilseed intercropping systems in western Canada, particularly the contributions from biological nitrogen fixation (BNF). Kabuli chickpea and brown flax were grown without added fertilizer as monocrops and as intercrops in mixed and alternate seed row configurations at sites located in the Brown (Central Butte, SK) and Black (Redvers, SK) soil zones in 2019 and 2020. Comparison was made of grain and straw yields, nitrogen (N) and phosphorus (P) uptake of grain and straw, and proportion and amount of biologically fixed N contributed from the chickpea and transferred to the flax. The intercrop grain yield land equivalent ratio (LER) and N and P uptake LER values were at or above 1 for the four site-years, indicating benefit from intercropping in increasing total yield and crop N and P uptake from the land area. The proportion of N derived from BNF was not enhanced in this intercrop combination, but considerable biologically fixed N (8%–22%) was transferred from the chickpea to the flax during the growing season. This was associated with reduced depletion of soil N compared to monocrop flax in part due to the contribution of biologically fixed N in the chickpea–flax intercrop system.