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ARS Home » Midwest Area » Columbia, Missouri » Cropping Systems and Water Quality Research » Research » Publications at this Location » Publication #331576
Title: Topsoil thickness influences nitrogen management of switchgrass

Author
item Yost, Matt
item Kitchen, Newell
item Sudduth, Kenneth - Ken
item THOMPSON, ALLEN - University Of Missouri
item ALLPHIN, ERIC - Renew Biomass

Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2016
Publication Date: 1/3/2017
Citation: Yost, M.A., Kitchen, N.R., Sudduth, K.A., Thompson, A.L., Allphin, E. 2017. Topsoil thickness influences nitrogen management of switchgrass. BioEnergy Research. 10(2):465-477. doi: 10.1007/s12155-016-9811-6.

Interpretive Summary: Switchgrass is native to Missouri landscapes and is an attractive bioenergy crop option for reintroduction on eroded portions of claypan landscapes where grain crop production is marginally profitable. The thickness of the topsoil or the depth of the soil above the claypan horizon can vary widely within fields and little information exists on its impacts on nitrogen (N) management of switchgrass. Therefore, a study was conducted near Columbia, Missouri to determine its influence on fertilizer N requirements of switchgrass. Across years, the legume treatment did not supply N to the switchgrass because it produced the same or lower switchgrass yield as the nonfertilized treatment. Topsoil proved valuable as switchgrass yield, nutrient removal, and partial profit usually increased as DTC increased. Fertilization with 90 lb N/acre on exposed (very shallow), shallow, or moderately thick soils and 60 lb N/acre on deep soils, was required to obtain the highest biomass yield, but it also increased nutrient removal. Strikingly, partial profit across years was negative for the legume treatment and was highest with no fertilizer on all soil thicknesses. Therefore, improvements are needed before intercropped legumes are profitable, and N fertilization may be needed only periodically to maximize switchgrass profit on claypan soils. These results will aid researchers and practitioners in the development of targeted, profitable, and sustainable bioenergy cropping systems on marginal soils in the Midwestern United States.

Technical Abstract: Switchgrass (Panicum virgatum L.) is an attractive bioenergy crop option for eroded portions of claypan landscapes where grain crop production is marginally profitable. Topsoil thickness above the claypan or depth to claypan (DTC) can vary widely within fields and little information exists on its impacts on N management of switchgrass. Therefore, a study was conducted at the University of Missouri South Farm near Columbia, Missouri to determine whether topsoil thickness influenced fertilizer N requirements of switchgrass. Switchgrass was planted in 2009 on plots ranging in topsoil thickness from 0 to 124 cm, and was harvested annually at postdormancy during 2011 to 2015. Three treatments were 0, 67, or 101 kg N/ha applied annually in May and a fourth was three intercropped native legumes as the N source. Across years, the legume treatment apparently supplied no N because it produced the same switchgrass yield on shallower soils as nonfertilized plots, or lower yield on deeper soils. Topsoil proved valuable as switchgrass yield, nutrient removal, and partial profit usually increased as DTC increased. Fertilization with 101 kg N/ha on exposed, shallow, or moderate DTC and 67 kg N/ha on deep DTC, was required to obtain the highest biomass yield, but it also increased nutrient removal. Strikingly, partial profit across years was negative for the legume treatment and highest with no fertilizer on all DTC classes. Therefore, improvements are needed before intercropped legumes are profitable, and N fertilization may be only needed periodically to maximize switchgrass profit on claypan soils.