Stubble Height Effects on Canola Microclimate on the Canadian Prairies.

English Abstract:

Previous research in the most arid region of the Canadian Prairies indicated that alteration of the early season microclimate using tall stubble from the previous year can create more favorable conditions which improve the performance of the following crop. Research on large-scale plots with canola seeded into either tall stubble (50 cm) or short stubble (20 cm) showed the canola yield was significantly higher in the tall stubble across 6 site-years where the stubble remained intact (i.e. not damaged or flattened). The yield advantage was not a result of additional snowcatch or higher spring soil moisture in the tall stubble because the sites all experienced higher than normal spring precipitation and wet spring moisture conditions across both tall and short stubble. However, the mid-season was warm and relatively dry for all the site-years. It is hypothesized the intact tall stubble slowed down evapotranspiration (ET) sufficiently compared to the short stubble to confer both reduced soil moisture stress to the canola as well as a yield advantage At each site, air temperature was measured 50, 20 and 5 cm above the soil surface and soil temperature 5 cm below the surface in all plots. Meteorological data was recorded by weather stations adjacent to the plots or obtained from the nearest provincial or Environment Canada stations. Following early season rainfall events, surface soil moisture at a site should be similar between treatments. If the hypothesis is correct (tall stubble reduced the rate of ET), the surface soil moisture in the days following rainfall at a site should remain higher in the tall stubble than the short stubble. If this is the case, then the soil temperature near the surface should warm more rapidly in the short stubble over the days following the rainfall. Initial analysis suggests this was occurring. Further analysis will attempt to quantify the effect across the range of site-years and for various days following rain in the early season.