The Effects of Input Management, Cropping Diversity, Environmental and Terrain Covariates on Crop Yield in a 19-Year Study in the Semi-Arid Canadian Prairie.

A long-term field experiment was conducted from 1994 to 2013 to assess the role of input and diversity in sustaining crop production and soil quality in the Canadian Prairies at the Agriculture and Agri-Food Canada Research Farm in Scott, SK. In addition to the effects of input and diversity, this research investigated effects of growing season precipitation (GSP), growing degree days (GDD), and terrain attributes (planar and profile curvature, wetness index, and slope) on the yield of wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and canola (Brassica napus L.). The experiment was a four replicate split-plot with main plot treatments consisting of three levels of inputs [organic (ORG), reduced (RED), and high (HI)] and sub-plots comprised of three levels of cropping diversity [low (LOW), diversified annual grains (DAG), and diversified annual perennial (DAP)]. Data were analyzed with the MIXED model procedure, partial least squares analysis, partition analysis, analysis of variance and covariance. Results indicated that input, diversity, environmental covariates and terrain attributes were significantly correlated with crop yield. Yield was highest in the HI and RED systems, while ORG system had lowest yield due to nitrogen deficiency and in part due to weed competition. Crops grown in the HI-DAG, HI-LOW and RED-DAG, RED-LOW rotations produced higher yields compared to all other combinations of input and diversity. April, June, July GSP and July GDD were highly correlated with crop yield followed by the effects of input and diversity, depending on the crop. The effect of terrain attributes was clearly evident in years with deficient or excess precipitation, which accounted for 8 to 45 percent of the variation in wheat yield. Terrain attributes, GSP, and GDD should be assessed when analyzing impacts of fixed effects such as input and diversity on crop yield, to account for variability due to weather, micro-topography or landforms.