Suitability of legume cover crop-winter wheat intercrops on the semi-arid Canadian Prairies

Abstract

Farmers on the Canadian prairies are interested in including legume cover crops in their cropping systems to reduce fertilizer inputs and improve farm sustainability. A field study was conducted to determine the merits of establishing alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.) or Austrian winter pea (Pisum sativum L.) cover crops in fall or in spring with winter wheat (Triticum aestivum L.). Spring-planted legumes emerged well within the winter wheat crop, but their growth was limited under these semi-arid conditions. Fall-planted red clover had low plant densities following winter in two of three experiments and fall-planted winter pea reduced winter wheat yield by 23 to 37% compared with the no cover crop control. In contrast, fall-planted alfalfa exhibited good winterhardiness, provided some weed suppression without reducing winter wheat yield, caused only a slight reduction in soil water content, and contributed an extra 18 to 20 kg ha-1 of available soil N at the time of seeding the following spring crop. Additionally, fall-planted alfalfa increased the yield of succeeding canola (Brassica napus L.) in unfertilized plots in two of three experiments. Further research is warranted to better understand the agronomic and economic benefits of alfalfa-winter wheat intercrops under a wider range of environmental conditions.Key words: Cover crops, intercropping, relay crops, soil nitrogen, soil conservation