The potential nutrient cycling benefits from legumes (e.g. N2-fixation) and the high biomass potential of cereal rye are well known. Further studies are warranted to evaluate bi-culture mixtures and their effects on soil nutrient stratification and microbial enzyme activity because these two properties may be differently expressed (enhanced) by legume/grass mixes. The objectives of this study were: (1) show different cover crops and cover crop mixes containing grasses and legumes differentially stratify carbon and N; (2) show the change in microbial enzyme activity in soils planted with individual cover crops relative to cover crop mixes; 3) determine the persistence of any changes after a summer annual crop. Baseline samples were collected in fall 2016 at 0-15 and 15-30 cm depths after a seasonal fallow and a summer maize crop. Cover crop mixes were planted in fall 2016, terminated in spring 2017, and a summer hemp crop (Cannabis sativa) planted. After cover crop termination and hemp harvest, soils were sampled at 0-7.5, 7.5-15, and 15-30 cm depths. Total C, total N, total P, mineralizable N, POXc (labile C), and four soil enzymes (phosphatase, sulfatase, glucosidase, and urease) were evaluated. Stratification ratios decreased following cover crops. Cover crop mixes stratified mineralizable N deeper than legumes alone in five of six instances. Enzyme activity increased following cover crops, but there was little significance due to cover crop type. Cover crop mixtures did not significantly increase measured variables more than single species did. This study did not demonstrate an advantage to using either an individual grass or legume or mixture in terms of enhancing soil quality parameters.

Copyright © Landon M. Gibbs 2020