Corn Stover Nutrient Removal Estimates for Central Iowa, USA

Douglas Karlen,Stuart Birrell,John Kovar

doi:10.3390/su7078621

Abstract

One of the most frequent producer-asked questions to those persons striving to secure sustainable corn (Zea mays L.) stover feedstock supplies for Iowa’s new bioenergy conversion or other bio-product facilities is “what quantity of nutrients will be removed if I harvest my stover?” Our objective is to summarize six years of field research from central 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 then used the plant fraction estimates to compare various stover harvest scenarios and provide an answer to the producer question posed above.

Highlights

Corn stover is the above-ground, non-grain plant material that remains following grain harvest.To support emerging cellulosic bioenergy operations in the U.S.A., such as the POET-DSM ProjectLiberty near Emmetsburg, Iowa, and DuPont Cellulosic Ethanol near Nevada, Iowa, stover was identified as the primary initial feedstock [1] because of the vast area upon which the crop is grown
Harvesting all of the machine-collected stover would have removed an average of 1921 kg·ha−1 or 48% of the source carbon associated with non-grain biomass
This article summarizes primary, secondary, and micronutrient concentrations measured in more than hand-harvested, vegetative corn plant samples from above and below the ear, as well as in cob and grain fractions collected in central Iowa, U.S.A. between 2008 and 2013 as part of a bioenergy feedstock assessment project

Summary

Introduction

Corn stover is the above-ground, non-grain plant material that remains following grain harvest.To support emerging cellulosic bioenergy operations in the U.S.A., such as the POET-DSM ProjectLiberty near Emmetsburg, Iowa, and DuPont Cellulosic Ethanol near Nevada, Iowa, stover was identified as the primary initial feedstock [1] because of the vast area upon which the crop is grown. During the past 25 years, corn grain yields and the resultant quantity of stover have increased significantly [4] and in some high-yielding areas, stover management has become a concern because of increased cost [5] and its potential negative effects on subsequent crops. To ensure corn stover and other crop residues, such as wheat (Triticum aestivum) or rice (Oryza sativa), are being managed in a sustainable manner, it is important to balance both economic drivers put forth by biorefineries and environmental constraints [6] within every field or potential sub-field harvest area

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