Soil particulate organic matter contribution of hairy vetch ecotypes as winter annual legume cover crops

Abstract

Efficient cover crop management provides numerous benefits to the agroecosystems including soil organic matter (SOM) contribution. In the cold climates of the upper Midwest, options of cover crop species that can withstand harsh winters including freezing temperatures, variable snowfall, and limited time for establishment, are few. The particulate organic matter (POM) is a potential fertility index. The objective was to investigate hairy vetch (Vicia villosa) ecotypes as promising winter annual legume cover crops by quantifying their contribution to the particulate organic fraction of SOM, compared to winter rye (Secale cereale) cereal cover crop, and to evaluate C:N ratios of contributed POM by each cover crop treatment to demonstrate the differences in POM quality after early spring incorporation of fall-planted winter cover crops. A field trial was conducted over two locations with different soil types and land use history. Grand Rapids had sandy loam soil and previous land use was >25 years old apple orchard, and Lamberton had silty loam soil and organic row-cropping production systems prior to this study. POM was separated by light (1.6 g cm⁻³) density fractionation of soil samples collected before incorporation of cover crops and one month after incorporation, to assess the quantity and to analyze its C and N ratios. Strong weed competition led to weak emergence of cover crops and reduced biomass in both locations. Average POM quantity of combined treatments increased after incorporation of cover crops in Lamberton, but was not significant in Grand Rapids due to the high amount of litter content in soil of previous land use. Cover crop treatments in Lamberton had contributed lower C:N ratio POM quality.