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

Recent expansion of corn (Zea mays) acreage 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. The abundance of AMF in soil is influenced by the inclusion of crops that host mycorrhize (soybean (Glycine max), wheat, corn) or non- mycorrhizal host  crops (canola) grown in a rotation. To understand the effects of previous crop on corn grain yield, a two-year rotation study was initiated at University of Manitoba Ian N. Morrison Research Farm, near Carman, Manitoba in 2014-15. Corn, canola, soybean and wheat were grown in sequence year1 as preceding treatment crops in a randomised complete block design. Corn was grown as a test crop in sequence year 2. Corn plants sampled at the V6 and silking stage were used to measure plant biomass and phosphorus uptake. Corn root samples collected at the same stages were used for assessment of AMF colonization. Spring soil P and mineral N concentrations were similar in all the crop sequences before seeding of corn test crop. In spite of this, the early vegetative growth of corn test crop was affected by the previous crop. In the canola- corn sequence, V6 corn plants were shorter with lower dry matter yield and P uptake compared to other crop sequences. In contrast, corn plants in the soybean-corn sequence were tallest with highest dry matter yield and P uptake at both the V6 stage and silking stage. The AMF colonization was lower only at V6 stage in canola-corn sequence compared to other crop sequences. Despite these differences in corn growth at the V6 and silking stage, there was no significant effect of preceding crop on corn grain yield, moisture, and test weight. The results reported here are from one cycle of the crop sequence experiment and will be repeated to validate the findings in 2015-16 and 2016-17.