SOIL MANAGEMENT FOR ENHANCED AGRICULTURAL PRODUCTIVITY AND SUSTAINABLE BIOFUEL FEEDSTOCK PRODUCTION
Location: Soil, Water, and Air Resources Research Unit
Title: Corn stover harvest strategy effects on grain yield and soil quality indicators
Submitted to: Agrociencia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 7, 2012
Publication Date: N/A
Interpretive Summary: The United States Environmental Protection Agency (USEPA) identified corn stover, the aboveground material left in fields after grain harvest, as “the most economical agricultural feedstock...to meet the 16 billion gallon cellulosic biofuel requirement.” To sustainably harvest a portion of this material without having adverse effects on soil and water resources, field studies are needed to quantify effects of various harvest strataegies. This study showed no significant differences among stover harvest treatments, but there were significant seasonal and replicate effects. The replicate effects indicate high variability across the 125 acre field and suggest that producers should be using good management programs including routine soil-testing and plant analysis before deciding to harvest stover. The seasonal changes suggest that less intensive tillage practices, cover crops, or a more diversified crop rotation should be used to help sustain the soil resources. Overall, producers should generally not harvest corn stover if their yields are not consistently above 175 bu/acre in central Iowa. This study will be useful to industry, conservation, crop consulting, and research personnel striving to develop susstainable biofuel and bio-product industries.
The development of technologies to use cellulosic biomass as a feedstock for biofuel production was recognized as an important research focus because cellulose is a more widely-available feedstock than corn starch. Our objective was to compare various corn (Zea mays L.) stover harvest strategies to determine which would be most sustainable. A complete block design with 2 ha plots, each replicated three times, was imposed on a 50 ha (125 acre) Clarion-Nicollet-Webster soil Association site near Emmetsburg, Iowa, U.S.A. before harvesting the 2008 corn crop. Hand samples were collected from a 1.5 m2 area in each plot to establish the potential amount of above-ground biomass that could be potentially harvested using one of seven stover harvest strategies. Surface soil samples (0 to 15 cm) were analyzed following each harvest to monitor fertility changes and to make subsequent fertilizer recommendations. Grain yields averaged 11.4, 10.1, 9.7, and 9.5 Mg ha-1 in 2008, 2009, 2010, and 2011, respectively, but were not significantly affected by stover harvest treatments. Relative yield for the various treatments ranged from 97 to 107% of the conventional treatment for which none of the residue was harvested. Four-year average stover yields ranged 1.0 to 5.2 Mg ha-1 which was 12 to 60% of the above-ground biomass. Three years of plant tissue data at anthesis indicated N management needed to be improved as the values were below the critical concentration of 27 g kg-1. Sulfur concentrations were just barely above the critical value of 15 g kg-1. Soil test analyses showed substantial field variability but no significant stover harvest treatment effects. There was a slight decrease in soil organic carbon, unrelated to the stover harvest treatments, that is attributed to the intensity of tillage and crop yields that were lower than expected. Overall, this study is consistent with other studies in the U.S. Corn/Soybean Belt that indicate to sustain soil resources within this region, corn stover should generally not be harvested if average grain yields are less than 11 Mg ha-1 (175 bu ac-1). Strategies for achieving those levels include implementing more rigorous soil-testing and plant analysis programs, installing tile drainage where needed, improving overall nutrient management programs, reducing tillage intensity, incorporating cover crops and rotating corn with other crop such as soybean [Glycine max (L.) Merr.], small grain, or forage.