|Sudduth, Kenneth - Ken|
|Thompson, Allen - University Of Missouri|
|Allphin, Eric - Renew Biomass|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2017
Publication Date: 5/5/2017
Citation: Yost, M.A., Kitchen, N.R., Sudduth, K.A., Thompson, A.L., Allphin, E. 2017. Topsoil thickness and harvest management influence switchgrass production and profitability. Agronomy Journal. 109(3):985-994. doi: 10.2134/agronj2016.09.0561.
Interpretive Summary: Switchgrass is native to Missouri landscapes and is an attractive forage and biomass crop option for reintroduction on eroded portions of some claypan landscapes where grain crop production is marginally profitable. A study was conducted near Columbia, Missouri to determine how topsoil thickness influences the production and profitability of switchgrass grown as forage and biomass (i.e., integrated systems) or biomass only. Switchgrass was planted in 2009 on soil with a range in topsoil thickness, and was annually harvested twice (June and November-December) in the integrated system or once (November-December) in the biomass only system during 2011 to 2015. Results indicated that topsoil thickness mainly affected the performance of the second, biomass harvest of the integrated system. This harvest had greater yield, nutrient removal, and profit as topsoil thickness increased. Across topsoil thicknesses and years, the integrated system had more severe weed cover, less total yield, more nutrient removal, and less profit than the biomass only system. Therefore, improvements are needed before integrated systems are profitable, and biomass only systems may offer greater longevity, productivity, and profitability. These results will aid researchers and practitioners in the development of targeted, profitable, and sustainable switchgrass systems on marginal soils in the Midwestern United States.
Technical Abstract: Switchgrass (Panicum virgatum L.) is an attractive dual use forage and/or biomass crop option for eroded or marginal soils where corn (Zea mays L.) grain production often is not profitable. Topsoil thickness, especially above soils with a claypan, relates to crop productivity and nutrient removal and can vary widely within fields. Knowledge is lacking on how topsoil thickness, or depth to claypan (DTC), impacts switchgrass grown for forage and/or biomass. Therefore, a study was conducted near Columbia, Missouri to determine whether DTC influenced the production and profitability of integrated (forage and biomass) and biomass only switchgrass. Switchgrass was planted in 2009 on plots with a range of DTC classified as exposed (<8 cm), shallow (8-15 cm), moderate (16-30 cm), and deep (>30 cm), and was annually harvested twice (preanthesis and postdormancy) in the integrated system or once (postdormancy) in the biomass only system during 2011 to 2015. Results indicate that DTC mainly affected the biomass harvest of the integrated system; yield increased 74% and nutrient removal by 50 to 102% from exposed to deep soil across years. Across DTC and years, the integrated system had more severe weed cover (46 vs. 6%), less yield (9.8 vs. 13.5 Mg/ha), more N, P, and K removal (79 to 206% more), and less profit ($-155 vs. $137/ha or $80 vs. $220/ha without nutrient replacement costs) than the biomass only system. Therefore, improvements are needed before integrated systems are profitable, and biomass only systems may offer greater longevity, productivity, and profitability.