Evaluating the Potential Use of Winter Cover Crops in Corn-soybean Systems for Sustainable Co-production of Food and Fuel

Authors: Baker, John; GRIFFIS, T - UNIVERSITY OF MINNESOTA

Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2009
Publication Date: 12/15/2009
Citation: Baker, J.M., Griffis, T.J. 2009. Evaluating the Potential Use of Winter Cover Crops in Corn-soybean Systems for Sustainable Co-production of Food and Fuel. Agricultural and Forest Meteorology. 149(12):2120-2132.

Interpretive Summary: There has been tremendous interest in recent years in the displacement of fossil fuels with fuels derived from plants, and the biofuel industry is growing rapidly. However, this has become controversial, due to concerns that the attendant diversion of agricultural production is reducing world food supplies, increasing food prices, and accelerating the conversion of native ecosystems to agricultural production. Consequently, there is motivation to develop systems that can provide feedstocks for biofuels without reducing food production capacity. One possible option is the use of winter cover crops in current crop production areas. To examine the viability of this approach in corn-soybean systems, we constructed a simulation model to predict the biomass accumulation of winter rye, and to estimate its impact on the water available for the subsequent grain crop. The model is designed to use readily available weather data and basic management information about corn and soybean planting and harvest dates. It has been tested against field data collected at Rosemount, MN, then used to estimate production at a number of sites across the midwestern United States. Results suggest that rye biomass production would range from 1 to 10 Mg ha-1, with the greatest variability at the more northerly locations, where lower yields occur in years with cool, cloudy springs. Impacts on subsequent water availability were also quite variable; in general, soil water depletion was greastest in years with the greatest rye biomass production, but this was often counteracted by late spring rains. There appears to be considerable potential for additional biomass production in corn/soybean systems, but with significant risk of subsequent water stress for the following crop, so that the system will work best for soils with high water-holding capacity or producers with irrigation.

Technical Abstract: Climate change and economic concerns have motivated intense interest in the development of renewable energy sources, including fuels derived from plant biomass. However, the specter of massive biofuel production has raised other worries, specifically that by displacing food production it will lead to higher food prices, increased incidence of famine, and acceleration of undesirable land use change. One proposed solution is to increase the annual net primary productivity of the existing agricultural land base, so that it can sustainably produce both food and biofuel feedstocks. This might be possible in corn and soybean production regions through the use of winter cover crops, but the biophysical feasibility of this has not been systematically explored. We developed a model for this purpose that simulates the potential biomass production and water use of winter rye in continuous corn and corn-soybean rotations. The input data requirements represent an attempt to balance the demands of a physically and physiologically defensible simulation with the need for broad applicability in space and time. The necessary meteorological data are obtainable from standard agricultural weather stations, and the required management data are simply planting dates and harvest dates for corn and soybeans. Physiological parameters for rye were taken from the literature, supplemented by experimental data specifically collected for this project. The model was run for a number of growing seasons for 7 locations across the Midwestern USA. Results indicate potential rye biomass production of 1-10 Mg ha-1, but with considerable variability from year to year, particularly for the more northern sites, where either cool, cloudy spring weather or early corn planting can limit rye production. Not surprisingly, soil moisture depletion for the subsequent crop is most likely in years and sites where rye biomass production is greatest. Consistent food and biomass production from corn/winter rye/soybean systems will probably require irrigation in many areas, and the use of shorter season corn varieties in the northern portion of corn production regions.