Cereal rye and oilseed radish cover crop effects on soil properties and nitrogen cycling in Indiana
Recently there has been great interest amongst producers to plant cover crops into corn-soybean (Zea mays L. – Glycine max L. Merr.) rotations. Oilseed radish (Raphanus sativus L.) (OSR) and cereal rye (Secale cereale L.) are two cover crops receiving attention due to nitrogen (N) scavenging abilities. This thesis is comprised of two projects, one focusing on OSR and the other on cereal rye. The objectives of the one-year OSR study were to repeat a study conducted in 2011-2012 to determine effects of OSR and OSR bicultures on inorganic soil-N concentrations with time, depth and distance from the OSR drilled row and on corn productivity. Cover crop treatments included a no cover crop control, OSR alone, OSR/oat (Avena sativa L.), and OSR/rye and were established in fall of 2013 at the Purdue Diagnostic Training Center (DTC) in West Lafayette, Indiana (IN). Bulk soil samples were taken in the fall, and detailed samples with depth and distance from the OSR drilled row were taken in spring on four sampling dates. Cover crop aboveground biomass samples were taken in fall and spring. Corn was established after rye termination and the following measures were taken during corn growth: V6 tissue samples, stalk nitrate, grain N content, plant populations and yields. Cover crop treatment affected soil NO3-N more than soil NH4-N. Soil NO3-N was highest near the soil surface, closest to the OSR drilled row and generally decreased with depth. Soil NO3-N increased with time, whereas soil NH4-N peaked by the third sampling. Corn measurements were not affected by cover crop treatment. The Corn-based Cropping Systems Coordinated Agricultural Project (CSCAP) was begun in 2011 with the goal of increasing resiliency of corn-based cropping systems to the stresses of climate variation. The site at the Southeast Purdue Agricultural Center (SEPAC) in Butlerville, IN consists of four treatments: corn no cover, corn with rye, soybean no cover, and soybean with rye. Data from the first four years of this study are presented. Parameters include: rye dry matter and N accumulation, soil NH4-N and NO3-N concentrations, soil organic carbon and total nitrogen, soil fertility measures, soil aggregate stability, corn grain and stover N and carbon content, corn populations, and cash crop yields. Weather variability impacted cash crop and rye productivity, with decreased yields in 2011-2012 due to drought conditions and greater growth and yields in 2013-2014. Little rye growth was achieved in fall seasons, but spring growth ranged from 681-3102 kg ha-1 with 22-81 kg N ha-1 in aboveground biomass. Soil NH4-N decreased with depth whereas soil NO3-N decreased with depth in fall and increased with depth in spring. Soil fertility measures decreased with time at SEPAC regardless of treatment. In 2013, soil aggregate stability in the 0-5 cm depth was greater under cereal rye compared to no cover crop. Cash crop yields were unaffected by cover crop treatment.
Kladivko, Purdue University.
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