Corn stover has been used for many years as bedding and food for livestock, as well as to nourish and protect soils. In recent years, the ubiquitous stalk, leaf and cob residue of corn plants left in fields after harvest has found a new market: as a potential source for cellulosic ethanol production.
But harvesting the stover – which, when left in place, halts erosion and supplies vital nutrients back to the soil – could have unintended consequences, from lowering the fertility of fields to affecting productivity, soil and water quality and even climate. A comprehensive new study by Iowa State University agronomy researchers may soon shed light on these questions.
Last fall, Mahdi Al-Kaisi, ISU Extension soil management specialist, and ISU Extension colleagues, started a three-year study looking at how removing residue at different rates affects soil productivity, nutrient cycling and greenhouse gas emissions in no-till and chisel-plow fields. They also want to find the optimal nitrogen, phosphorus and potassium fertilization rates needed to supplement nutrients lost from residue removal.
A diverse research-based effort integrating these questions could provide information needed to successfully use biomass production for energy and livestock in Iowa. The study was set in motion after harvest last fall. Residue was removed at three rates-- 0, 50 percent or 100 percent-- on both the no-till and chisel-plowed plots.
Productivity is highly linked to available nutrients – which in turn can affect soil structure, another key factor in yields. “Corn stover residue is a good source of carbon into the soil organic matter. If you continue to harvest residue, you are removing a significant portion of the carbon input to the soil,” Al-Kaisi said. How stover removal alters nutrient cycling – the second major component of the research – is integral to the yield question.
Throughout the spring and summer, ISU agronomy graduate student Jose Guzman has been testing a range of soil indicators, from levels of organic carbon, nitrogen and other nutrients to water infiltration, microbial biomass and emissions of carbon dioxide (CO2) and nitrous oxide (N2O), two key greenhouse gases.
“Soil temperature and moisture are huge factors in the decomposition of stover,” Guzman said. “Every hour, in-field sensors capture soil temperature data, and every day someone tests soil moisture. We’ll capture these all year and might try to use this data to make a model to predict decomposition rates.”