Winter-hardy legumes deliver significant amounts of N to corn on a sandy loam soil in southern Ontario

Soybean-winter_wheat-corn rotation is common for in humid s-Ontario. The objectives of this study were to determine: (1) how much nitrogen can be scavenged in legume cover crop; (2) what is the contribution of cover crop nitrogen to the yield of following corn. The cover crops were planted into the soil after winter wheat harvest, including Crimson clover (CC), hairy vetch (HV), red clover (RC), a non-cover crop conventional control (CKC) and a non-cover crop organic control (CKO). This study (2013-2016) was arranged in a randomized complete block design with 4 replicates on a sandy loam. No synthetic nitrogen fertilizer was added to the cover crop and CKO plots. One set of cover crop biomass samples were collected at the first killing-frost and another set was collected in following year before corn planting. At freeze-up, the amounts of total nitrogen in aboveground biomass were 126, 123, and 76 kg/ha, respectively, in CC, HV and RC treatments. The nitrogen contents in plant aboveground biomass changed to 104, 283 and 180 kg/ha in CC, HV, and RC plots before corn planting. The corn grain yields (3 year average) were 14525 kg/ha for the CKC and only 6181 kg/ha for the CKO. In comparison, the corn grain yields were 11762, 12765, and 12282 kg/ha for the CC, HV RC treatments, respectively. Without the use of synthetic N fertilizer, growing CC in the fallow seasons after winter wheat attained 81% of the corn grain yield of the CKC and growing HV and RC gained 88% and 86%, respectively, of the corn grain yield in the CKC achieved which received 160 kg N/ha. The CC, HV and RC can deliver significant amount of N to corn and the HV and RC performed better than the CC in term of N benefits to corn yield.