Comparative breakeven analysis of annual grain and perennial switchgrass cropping systems on claypan soil landscapes.

The Central Claypan region is an important agricultural production contributor in the U.S. Midwest. Because of the tendency for grain yield fluctuations caused by water stress, however, claypan soils may have potential for conversion from grain to grass production in support of biomass energy markets and conservation programs. This study examined the economic potential of transitioning from grain to perennial switchgrass (Panicum virgatum L.) production on claypan soils using comparative breakeven analysis. Partial budgets for a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation and a perennial switchgrass cropping system were developed. Yield data from research plots with varying topsoil depths defined by the underlying claypan layer were used to establish yield expectations as affected by topsoil depth. Switchgrass yield projections for the claypan region were simulated with the Agricultural Land Management Alternatives with Numerical Assessment Criteria (ALMANAC) model. Comparative breakeven prices for two switchgrass cultivars ranged from US$65 on marginal, eroded soils to US$124 Mg-1 on soils with >27 cm of topsoil. Breakeven yields with a biomass price of US$40 Mg-1 would require yield increases of up to 450% for lower yielding cultivars. The switchgrass cultivar Kanlow holds the most promise for biomass production on claypan soils; with an average projected yield of 12.56 Mg ha(-1), breakeven prices fall to around US$60-80 Mg-1 for marginal soils with <15 cm of topsoil. Based on these projections, perennial switchgrass shows potential to compete with conventional grain crops at reasonable yield levels on eroded soils in the Central Claypan region.