Stubble management and microclimate, yield and water use efficiency of canola grown in the semiarid Canadian prairie

Standing stubble traps snow and creates a favorable microclimate, which increases yields in wheat (Triticum aestivum L.) and pulses [chickpea (Cicer arietinum L.), field pea (Pisum sativum L.) and lentil (Lens culinaris L.)]. Generally, the taller the stubble the greater is the effect on microclimate and yield. A field study using farm-scale seeding and harvesting equipment was conducted over four seasons (1999 to 2002) to assess the effect of stubble management on the microclimate, water use and seed yield of argentine canola (Brassica napus L. 'Arrow') in the semiarid prairie surrounding Swift Current. Tall (30 cm), short (15 cm) and cultivated stubble treatments were deployed in fall and in spring. An additional tall stubble treatment with extra fertilizer N (application rate recommended for the Black soil zone in the subhumid prairie) was included to assess the role of fertilizer in canola response to stubble management practices. The differences in wind velocity, soil temperature and solar radiation reaching the soil surface indicated significant modification of the microclimate by tall compared with cultivated stubble. Yields were highest from the tall stubble receiving extra fertilizer. Further research is needed to determine optimum fertilizer rates to maximize canola yields in the semiarid prairie. For treatments receiving equivalent rates of fertilizer, tall stubble increased seed yield of canola by about 24% and water use efficiency (WUE) by about 19% compared with stubble cultivated in the fall. Comparing between stubble treatments deployed on fields that overwintered as tall stubble and which received equivalent rates of fertilizer, tall stubble increased canola yield by about 16% and WUE by about 11% compared with cultivated stubble. Crop water use was not affected by stubble management so the increased grain production was due to increased WUE.