|CONWAY, LANCE - University Of Missouri|
|Sudduth, Kenneth - Ken|
|THOMPSON, ALLEN - University Of Missouri|
|MASSEY, RAYMOND - University Of Missouri|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2016
Publication Date: 5/5/2017
Citation: Conway, L.S., Yost, M.A., Kitchen, N.R., Sudduth, K.A., Thompson, A.L., Massey, R.E. 2017. Topsoil thickness effects on corn, soybean, and switchgrass production on claypan soils. Agronomy Journal. 109(3):782-794. doi: 10.2134/agronj2016.06.0365.
Interpretive Summary: Substantial soil erosion during decades of row crop production on claypan soils has led to varying topsoil thickness across fields in Missouri, Kansas, and Illinois. This had led to frequent marginal profitability for producers, especially for corn on areas where the worst erosion has occurred. Thus, alternative perennial cropping systems, such as switchgrass, that could improve or maintain yield stability, and possibly improve soil health, on eroded soils is desirable. However, for producers to convert from row crop to switchgrass production, it must be profitable. Therefore, research was conducted from 2009 to 2015 near Columbia, Missouri to compare the production and profitability of annual row crops (corn and soybean) and perennial bioenergy switchgrass on soils with variable topsoil thickness. Results indicated that switchgrass yield and profit generally were more stable than corn or soybean on shallow soils. However, due to the low market value of bioenergy switchgrass, it was far less profitable than soybean, but was able to produce greater profits than corn on very shallow soils. These results illustrate that switchgrass can produce relatively high, consistent yields across topsoil depths, and that it has the potential to compete economically with corn if higher market values develop. This information will aid stakeholders in deciding where to place corn, soybean, and switchgrass on landscapes with claypan soils.
Technical Abstract: Diminished topsoil thickness or depth to claypan (DTC) is a major cause of yield and profit depression in corn (Zea mays L.) and to a lesser extent in soybean (Glycine max [L.]) production on claypan soils. Perennial grasses such as switchgrass (Panicum virgatum L.) may be more resilient to reduced DTC than grain crops. Therefore, a study was conducted on a Missouri claypan soil to compare production and profit of switchgrass grown for bioenergy with corn and soybean grain over varying DTC. Corn, soybean, and switchgrass yield were measured from 2009 to 2015 on plots constructed with DTC representative of those typically found on Midwest claypan landscapes. Yields were evaluated by year, within wet and dry year categories, and across all years using harvested yield, relative yield (RY), yield coefficient of variation (CV) and profit. Across all years, RY increased 23 and 13% points as DTC increased from 0 to 15 cm for corn and soybean, respectively, while switchgrass RY averaged 72%. Corn, soybean, and switchgrass yield CV averaged 46, 35, and 17% (30, 35, 11% with 2012 excluded for corn and switchgrass), respectively. Corn and switchgrass profit increased with DTC to a maximum of US$379 and US$182 at DTC of 31 and 32 cm, respectively, while soybean profit was the highest across DTC, averaging US$634. Results from this study show switchgrass has the capacity to reduce yield variability caused by DTC, especially at areas of low DTC, but currently is unable to compete with current corn and soybean market values.