Is Switchgrass Acreage an Option?

January 28, 2017 02:00 AM

Studies examine erosion recovery and first-year income

When runoff and erosion scour topsoil to the bone, exposing the clay layers beneath, switchgrass can be an agronomic lifeline in improving soil quality. In addition, corn grown during switchgrass establishment could provide income opportunity.

Perennial switchgrass can be viable on ground ill-suited for other crops, says Stephen Anderson, soil scientist with the University of Missouri. This is contingent on the biofuels market, where switchgrass can be an ethanol source or fuel for power plants.

From 2009 to 2014, Anderson’s research team managed plots at varying topsoil levels. Some were in a 
no-till corn and soybean rotation, and the rest were in continuous switchgrass. After five years, switchgrass brought an 11% water saturation jump, calculated by measuring the water retention curve. He says the study demonstrates the hearty nature of switchgrass growth in claypan soil.

Typically, farmland is topped by loess with silt loam on the surface, providing good water-holding capacity. “When it rains, topsoil stores water for the plants in a vastly superior manner than clay. Our clay in Missouri is very dynamic and doesn’t allow much water infiltration. It shrinks when dry and swells when wet,” he says.

Vigorous switchgrass root systems open pores in tough clay and improve water-holding capacity. Anderson also suspects ground improved by switchgrass might enhance subsequent grain crops, but he has yet to begin studies. “When economics are good for switchgrass, you can at least improve soil and then switch back to corn and soybeans as merited by the market. This could be an answer for a grower having grain troubles on eroded land,” he says.

If erosion has already taken place, perennial switchgrass can improve soil conditions. “If a grower has weak topsoil and can catch the biofuels market at the right spot, switchgrass is something to consider,” Anderson adds. 

Corn as a first-year companion to switchgrass is not a novel idea, but D.K. Lee, University of Illinois agronomist, has added guidelines for seeding rates and nitrogen application. In 2009 and 2010, Lee began three-year trials to test the efficacy of corn and switchgrass grown in tandem. Switchgrass production aims for biomass harvest in the second year, but offers no income during the first year.

“No harvest equates with no potential income. Our switchgrass research in Champaign County was aimed at helping farmers bring in revenue during the lull of the first year,” Lee says.

Lee’s switchgrass and corn trials were relatively simple. He planted both crops in the same plot and allowed switchgrass to prosper below the corn canopy. After corn harvest, switchgrass growth continued in the second year. Neither crop was affected by the other at harvest.

Lee tested three corn seeding rates: 28,000; 24,000 and 20,000. Nitrogen application varied between zero, 100 lb. and 200 lb. per acre (no nitrogen applications beyond the first year). Corn yields averaged 190 bu. per acre.

Lee notes switchgrass takes longer to germinate and needs an extra week of growth prior to corn planting. Herbicide control is another factor because switchgrass can’t tolerate glyphosate. “If weeds are too big of an issue, corn and switchgrass won’t be an effective combination,” Lee warns.

“However, if your ground is good for corn and switchgrass, you can harvest one crop and get revenue while the other crop grows,” he adds. 

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