Does Preceding Crop Affect the Growth and Grain Yield of Corn in Manitoba?.

Recent corn (Zea mays) acreage expansion in Manitoba provides an opportunity to improve crop diversity in existing rotations currently dominated by canola (Brassica napus) and wheat (Triticum aestivum). Corn grain yield is influenced by crop rotation due to its association with arbuscular mycorrhizal fungi (AMF) for nutrient and water uptake. Abundance of AMF in soil is influenced by inclusion of host mycorrhizal (soybean (Glycine max), wheat, corn) or non- host mycorrhizal crops (canola) in a rotation. To understand the effects of preceding crop on corn grain yield and growth, two-year rotation studies were initiated at University of Manitoba Ian N. Morrison Research Farm, near Carman, Manitoba in 2014-15 and 2015-16. Corn, canola, soybean and wheat were grown in sequence year1 in a randomised complete block design as preceding treatment crops. Corn was grown as a test crop in sequence year 2. In spite of similar spring soil Olsen P levels in all treatments, early vegetative growth (V6) of the corn test crop was affected in both years. The canola- corn sequence had the shortest V6 corn plants with lower dry matter yield and P uptake in both years. The AMF colonization in both years was lower at V6 stage in canola-corn sequence compared to all other crop sequences. In contrast, V6 corn plants were tallest with highest dry matter yield and P uptake in the soybean-corn sequence in 2015 and in the corn-corn sequence in 2016. However, there was no significant effect of preceding crop on corn grain yield in 2015 though grain yield in 2016 was lower in wheat-corn sequence compared to other crop sequences. Results reported here are from two corn test crop years with the 2016 crop year being influenced by wet growing conditions. This study will be repeated to validate these findings in 2016-17.