Date of Award

12-2016

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Agronomy

First Advisor

Eileen J. Kladivko

Committee Chair

Eileen J. Kladivko

Committee Member 1

Laura C. Bowling

Committee Member 2

James J. Camberato

Abstract

Cover crops are growing in popularity in the Midwest, although questions remain about how to include them most effectively in a corn-soybean ( Zea mays L. - Glycine max L.) rotation. This study was conducted to determine the effects of cereal rye ( Secale cereale L.) on soil bulk density and water retention, soil organic carbon, soil nitrogen, and water stable aggregate mean weight diameter after four years of cover crop growth and the effects on soil moisture over a five year period. The study was conducted at the Southeast Purdue Agricultural Center (SEPAC) on silt loam soils. A 14 hectare field was laid out in a split plot design with four blocks of four treatments in each block for a total of sixteen plots. Treatments were corn with cereal rye, corn with no cover, soybean with cereal rye, and soybean with no cover, all four treatments every year, with the corn and soybeans alternating yearly. The field site was established in the spring of 2011 and baseline samples were taken in the summer of that year before the first establishment of the cover crop in fall 2011. Measurements were taken at 0-10, 10-20, 20-40, and 40-60 cm depth intervals in 2011 and 2015 for bulk density, water retention, soil organic carbon, total soil nitrogen, and aggregate stability. Soil moisture and temperature were measured at five minute intervals from 2011-2016 at 10, 20, 40, 60, and 100 cm depths.

After four years of a cereal rye cover crop, wet soil aggregate mean weight diameter increased 55% when compared to the no cover control in the 0 to 10 cm depth and 29% in the 10 to 20 cm depth. Bulk density, water retention, soil organic carbon, and total soil nitrogen showed no change between cover crop treatments. Differences in soil moisture were detected throughout the year but further analysis is needed to fully quantify the effects of the cover crop as results were mixed throughout the time periods analyzed. Overall, in the early spring before cash crop planting, cereal rye either had significantly lower soil moisture or had no effect on soil moisture compared to no cover, while during the cash crop growing season in the 40 and 60 cm depths five of eight plot pairs showed relatively higher soil moisture and three of eight plot pairs showed lower soil moisture with cereal rye than with no cover. Cereal rye can be an effective soil conservation tool, protecting the soil surface from erosive forces, taking up excess nutrients at the end of a growing season, and helping feed soil microbes during a typically fallow period, but some of the improvements it has been reported to make may require a longer time period to change than the years included in this study.

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