Soil responses to bioenergy crop production in the North Carolina Piedmont

Authors: WANG, ZAN - North Carolina State University; HEITMAN, JOSHUA - North Carolina State University; SMYTH, T - North Carolina State University; CROZIER, CARL - North Carolina State University; Franzluebbers, Alan; LEE, SAGE - University Of Redlands, California; GEHL, RONALD - Dupont Pioneer Hi-Bred

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/2017
Publication Date: 7/12/2017
Citation: Wang, Z., Heitman, J.L., Smyth, T.J., Crozier, C.R., Franzluebbers, A.J., Lee, S., Gehl, R.J. 2017. Soil responses to bioenergy crop production in the North Carolina Piedmont. Agronomy Journal. 109:1368-1378.

Interpretive Summary: Land conversion from perennial tall fescue hay to annual sorghum or perennial miscanthus and switchgrass for biomass production has potential feasibility in the North Carolina Piedmont area. A scientist in the Plant Science Research Unit in Raleigh NC collaborated with scientists from North Carolina State University, University of Redlands, and Dupont Pioneer to investigate the role bioenergy crops have on soil properties in a Piedmont soil in North Carolina. As an annual crop, sorghum is easy to establish and can reach high yields with proper annual N input. However as perennial grasses, miscanthus and switchgrass have stable high yield output with very low nutrient input once matured. In addition, they had the least annual N, P, and K removals due to efficient nutrient translocation systems. Soil acidification is significantly slower under perennial bioenergy crops compared with fescue and annual crop rotations. After 3 years of land conversion, perennial bioenergy crops did not significantly alter soil physical properties. Land conversion to miscanthus production maintained soil organic C and N fractions at similar levels as original tall fescue hay production, and appeared to enhance soil organic C and N retention compared with conversion to annual row crops. These results will be useful to scientists and land practitioners to develop bioenergy systems that can sustain soil health in the Piedmont region of North Carolina.

Technical Abstract: Bioenergy crops are potential alternatives to traditional row crop and pasture/hay systems. A trial comparing effects of bioenergy to traditional production on soil properties was established in 2012 under no-till in the North Carolina Piedmont. Five cropping systems included: giant miscanthus (Miscanthus × giganteus), switchgrass (Panicum virgatum L.), biomass sorghum (Sorghum bicolor spp.), tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.], and corn (Zea mays L.)/wheat (Triticum aestivum L.)/soybean (Glycine max L.) rotation. Soil samples were collected before and 3 yr after trial establishment. Sorghum produced average yield of 21.5 Mg ha–1 in 2012 to 2015. Miscanthus and switchgrass reached yield plateaus of 21 and 15 Mg ha–1, respectively, and removed significantly less N, P, and K than other crops, due to their rhizome systems and lower fertilizer requirements. Th ey did not, however, demonstrate advantages over annual crops in soil physical properties. Soils under miscanthus and switchgrass had the least macropores and lowest saturated hydraulic conductivity. Summed to 30-cm soil depth, miscanthus maintained similar soil organic C as with tall fescue (58.6 vs. 55.0 Mg C ha–1), whereas soil organic C under sorghum and switchgrass were lowest (average of 49.5 Mg ha–1). Microbial biomass soil C under miscanthus (0–12-cm depth) was signifi cantly greater than under annual crops. Negative eff ects of switchgrass on soil physical properties and organic C and N might have been due to tillage required for establishment. Typical bioenergy crops do not appear to have major negative or positive eff ects on soil properties in the North Carolina Piedmont.