|BIRRELL, STUART - Iowa State University|
Submitted to: Sustainability
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/29/2015
Publication Date: 7/2/2015
Publication URL: https://handle.nal.usda.gov/10113/6557426
Citation: Karlen, D.L., Kovar, J.L., Birrell, S.J. 2015. Corn stover nutrient removal estimates for Central Iowa, U.S.A.. Sustainability. 7:8621-8634.
Interpretive Summary: Corn stover was identified as the primary initial feedstock for bioenergy and bio-product conversion facilities because of the vast area upon which the crop is grown, but before assumptions are made that corn stover is abundantly available and simply waiting to be harvested, it is important to recognize that stover already has economic value and provides many important ecosystem services. This manuscript reports the amount and current replacement value associated with plant nutrients removed when harvesting various above-ground portions of corn plants in central Iowa, USA. Compared to harvesting only the corn grain, harvesting stover from a field will increase nitrogen (N), phosphorus (P), and potassium (K) removal by an average of 14, 1.3. and 17 pounds per ton. The current (2015) fertilizer replacement cost for those nutrients is $6.04, $1.80, and $7.58 per ton, respectively. These additional nutrient replacement costs should be considered before deciding to harvest stover and accounted for in each nutrient management plan. Furthermore, no stover should be harvested if crop yields are below 175 bu/acre, since at those yield levels all available stover will be needed to protect the soil from wind and water erosion and to sustain soil organic matter. This information will be useful to farmers, conservationists, and those seeking to identify sustainable biomass feedstock supplies for emerging bioenergy and bio-product industries.
Technical Abstract: One of the most frequently asked questions to those striving to secure sustainable corn (Zea mays L.) stover feedstock supplies for Iowa’s new bioenergy conversion facilities is “what quantity of nutrients will be removed if I harvest my stover?”. Our objective is to summarize six years of field research in Boone and Palo Alto Counties in Iowa, U.S.A. where more than 600, 1.5 m2 samples were collected by hand and divided into four plant fractions: vegetative material from the ear shank upward (top), vegetative material from approximately 10 cm above the soil surface to just below the ear (bottom), cobs, and grain. Another 400 stover samples, representing the vegetative material collected directly from a single-pass combine harvesting system or from stover bales were also collected and analyzed. All samples were dried, ground, and analyzed to determine C, N, P, K, Ca, Mg, S, Al, B, Cu, Fe, Mn, and Zn concentrations. Mean concentration and dry matter estimates for each sample were used to calculate nutrient removal and estimate fertilizer replacement costs which averaged $25.06, $20.04, $16.62, $19.40, and $27.41 Mg-1 for top, bottom, cob, stover, and grain fractions, respectively. We conclude using these data to compare potential nutrient replacement costs for various stover harvest scenarios, thus providing an answer the question posed above.