Crop residue mass needed to maintain soil organic carbon levels: Can it be determined?

Authors: Johnson, Jane; Novak, Jeffrey; Varvel, Gary; Stott, Diane; Osborne, Shannon; Karlen, Douglas; LAMB, JOHN - University Of Minnesota; Baker, John; Adler, Paul

Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2013
Publication Date: 1/17/2014
Publication URL: http://handle.nal.usda.gov/10113/58297
Citation: Johnson, J.M., Novak, J.M., Varvel, G.E., Stott, D.E., Osborne, S.L., Karlen, D.L., Lamb, J.A., Baker, J.M., Adler, P.R. 2014. Crop residue mass needed to maintain soil organic carbon levels: Can it be determined? BioEnergy Research. DOI: 10.1007/s12155-013-9402-8.

Interpretive Summary: The leaves, stalk and cobs that remain after corn grain is harvested is called stover. Corn stover is expected to be used as major non-food bioenergy feedstock. Corn stover can be used to produce ethanol, or as a substitute for coal or other fossil-fuels. However, enough stover still needs to be returned for soil cover and to build new soil organic matter. Soil organic matter gives soil a dark, rich color and possesses many desirable soil properties. This study used new and previously published data to understand how harvesting stover may alter soil organic matter. The results estimated 3.6 dry tons of stover per acre was needed on average to maintain soil organic matter. However, this amount was highly variable. The results strongly refute the idea that a single value can be used as a recommendation for the amount of residue that needs to stay on the soil. Rather, producers need to work with conservation planners to determine the best strategy for their fields. Over-harvesting the stover could damage the soil, compromising the ability of those soils to provide food, feed, fiber and fuel for the world. Thus, it is critical to have robust and accurate planning tools. The data collected by this team provides information needed to make conservation planning tools and models more robust and accurate; thereby improving residue management guidelines and protecting the soil resource. The bioenergy industry, producers and the general public including policy-makers will benefit from the guidance on the benefits and risks associated with plant-based energy. This research contributes to the USDA-ARS-REAP project.

Technical Abstract: High yield potential and extensive acreage of corn (Zea mays L.) led to identifying stover as a non-food, herbaceous bioenergy feedstock. A vital aspect of utilizing stover for energy is to establish harvest criteria that avoids exacerbating soil erosion or degrading soil organic carbon (SOC). Our goal is to improve and verify the amount of retained stover needed to sustain SOC content. Data were gathered from a range of locations with divergent climatic conditions and soil properties in anticipation of the results providing key determinates of SOC responses to stover harvest. This current work using data from the Corn Stover Regional Partnership team (Team), which covered seven states and 19 fields, as well as published data to refine minimum residue requirements. Based on Team and published corn-based data (n=43) a minimum residue had an average of 8.2 ± 8.4 Mg stover ha-1 yr-1. No significant regression models were identified to predict minimum residue requirements. However, based on this dataset regression analysis for slope (change in SOC per unit residue) identified two-component model (r2 = 0.21, P=0.007) based on mean annual precipitation and silt+clay content and the overall maximum r2 model included 12 variable (r2 = 0.45, P=0.04). The concept of minimum residue return is conceptually important, but these analyses strongly refute that a universal minimum residue requirement exists. Empirical data are needed to calibrate, validate, and refine process-based modes so that valid sustainable harvest rates guideline are provided to producers, industry, and action agencies.