The Profitability of Cover Crops: Investigating the Effect of Additional Soil Organic Carbon

Marieke C Fenton, Purdue University

Abstract

This thesis analyzes one element of the question of cover crop profitability in Indiana. It investigates in isolation the crop yield benefit of additional soil organic carbon (SOC) from cover crop use and the economic implications thereof. The analysis is divided into three parts. First, the relationship between SOC and yield is analyzed using publicly available agronomic data. Next, an integrated modeling system is used to analyze the contribution of SOC by a 100% cereal rye cover crop. The third part combines the results of the first two and assesses the economic benefit of the increased SOC derived from the cover crop use within the context of corn and soybean cropping systems in the state of Indiana. The first part revealed that higher levels of SOC contribute to higher crop yields in both corn and soybeans for the majority of cropland soils in Indiana. The effect of SOC on yield was positive up to a tipping point after which the modeled effect of additional SOC on yield was negative. Soils with lower initial levels of SOC were estimated to have larger gains in yield per additional unit of SOC. These results were robust to varying the climate controls, as well as to varying input parameters to broaden and narrow the range of soil types tested. The second step showed that cover crops increase SOC, with larger gains at lower initial levels of SOC, and most of the gain in SOC occurring during the first four years of cover crop use. While cover crops contributed more SOC under a corn-soybean rotation, the total gain in SOC was higher in a continuous corn rotation with cover crops, which can be attributed to the higher total amount of organic matter produced in this rotation. Combining these two steps, we found an estimated increase in yield for corn of 1.41 bushels/acre after the 16-year cereal rye cover crop simulation, and of 0.79 bushels/acre for soybeans in a soil with an initial SOC of 3000 g C/m2 to a depth of 50cm. Most of this gain is accrued during the first four-year cycle of cover crop use, and the gain in the last four-year cycle is negligible. This converts to a monetary value of approximately $6.34 per acre for corn, and $8.40 per acre for soybeans. This estimated yield increase, though significant does not cover the annual cost of implementing a 100% cereal rye cover crop. However, increases in yield through SOC are only one of the agronomic benefits of cover crop use discussed in the literature. Further research is needed to evaluate the full economic benefit of cover crop use.

Degree

M.S.

Advisors

Tyner, Purdue University.

Subject Area

Agronomy|Agricultural economics

COinS