|BOARDMAN, DARA - University Of Missouri|
|ALLPHIN, ERIC - University Of Missouri|
|THOMPSON, ALLEN - University Of Missouri|
Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/1/2012
Publication Date: 7/20/2012
Citation: Boardman, D.L., Kitchen, N.R., Allphin, E.B., Thompson, A.L. 2012. Water and nitrogen use efficiency of corn and switchgrass on claypan soil landscapes. 12th International Conference on Precision Agriculture, July 20-23, 2012, Sacramento, California. 2012 CDROM.
Interpretive Summary: As the world population continues to grow and agricultural land is expected to produce more food and fuel, using that land efficiently is becoming increasingly important. Claypan soils, found in Missouri and Illinois, have physical properties that make crop production more difficult than other soils and generally have a high propensity for erosion. The properties of these soils can negatively affect how efficiently the plant uses soil water (water use efficiency (WUE)) and nitrogen (nitrogen use efficiency (NUE)). For these and other like soils it is important to find food and fuel crops that are most efficient in terms of WUE and NUE. Many claypan soil acres are currently cropped in corn and soybeans, but switchgrass is a potential biofuel crop that may be more efficient on claypan soils. This study investigated the WUE and NUE of corn and switchgrass on claypan soils that had different erosional phases (e.g., highly eroded to no erosion). In the second year of growth (first harvest year), switchgrass was not as efficient as corn for WUE or NUE. This was probably due to the switchgrass still trying to fully establish itself. However, from years 3-5 switchgrass had a better WUE, with difference in efficiency greatest for soils with minimal or no erosion. Switchgrass was also more efficient for NUE, being 14-18% more efficient than corn on highly eroded soils and 50-55% more efficient on non-eroded soils. Runoff was also much less with switchgrass than corn after year two. This indicates that switchgrass may be more appropriate on claypan soils than corn, as it is a crop that farmers will find well suited for production and erosion prevention on these soil landscapes. In turn, the public benefits from waterways better protected from sediment loss off croplands.
Technical Abstract: The Renewable Fuel Standard (RFS) mandated that 36 billion gallons of fuel must originate from renewable sources by 2022 with only 15 billion gallons originating from corn (Zea mays L.) grain. Therefore other sources must be investigated. This research was conducted at the University of Missouri, South Farm Research Center Soil Productivity Assessment for Renewable Energy and Conservation (SPARC) research site from 2009-2013. The soil depth to the claypan horizon treatment was classified into erosion classes as severely eroded (< 5 cm), moderately eroded (5-20 cm), slightly eroded (20-30 cm), or depositional (>30 cm). This investigation included corn and switchgrass (Panicum virgatum L.) with four replications per soil erosion class. Yearly simulations, using an original water-balance model, were run for the number of days of water stress, water used, runoff and Water Use Efficiency (WUE) based on recorded weather data from the research site and previously-derived relationships of water storage on variable claypan soil landscapes. Nitrogen content was measured for corn grain and switchgrass biomass to determine Agronomic Nitrogen Use Efficiency (NUEa). The biomass and grain yield for each plot was used for WUE and NUEa calculations. Results of the simulated model indicate that switchgrass results in more days of water stress, but also less runoff and better WUE. In dry years, increased depth to claypan led to an increased WUE of 1.17-1.25 kg/m^3 for the severely eroded soils and 2.19-2.77 kg/m^3 for depositional soils for switchgrass compared to corn. Switchgrass NUEa was 14-18% more efficient than corn on severely eroded soils and 50-55% more efficient on depositional soils in dry years. This research indicates that when considering water and N use efficiency, switchgrass for biofuels is a viable option when grown on claypan soils, with better drought tolerance and low environmental impact when compared to corn.