|Karlen, Douglas - Doug|
Submitted to: International Soil Tillage Research Organization Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/15/2009
Publication Date: 6/15/2009
Citation: Karlen, D.L., Birrell, S.J., Wendt, L.M., Hess, J.R. 2009. Strategies for Sustainable Corn Stover Feedstock Production. In: Proceedings of the International Soil Tillage Research Organization (ISTRO), June 15-19, 2009, Izmir, Turkey. p. 1-10. Interpretive Summary:
Technical Abstract: Second-generation biofuels will be developed using cellulosic feedstocks rather than grain or oilseed crops that can also be used for food and feed. However, to be sustainable, soil and tillage management strategies used to produce those feedstocks must not irreversibly degrade soil resources. Our objective was to develop a single-pass combine harvest system for simultaneously gathering corn (Zea mays L.) grain and stover. Harvest strategies included collecting (1) all above-ground plant material possible by cutting stalks at a stubble height of approximately 10 cm (whole plant), (2) the upper-half by height, (3) lower-half by height, or (4) no removal. Six site-years of data show an average of 3.9 and 4.8 Mg ha-1 of collectable cobs plus plant material from the ear shank upward (upper half) for continuous and rotated corn, respectively. Average N-P-K removal was increased by 23, 2, and 29 kg ha-1 for continuous corn and 36, 4, and 27 kg ha-1 for rotated corn, respectively, when compared to harvesting grain only at these Iowa USA sites. Whole plant stover harvest averaged 5.2 or 6.4 Mg ha-1 and increased N-P-K removal to 32-3-32 or 45-4-36 kg ha-1 for continuous or rotated corn, respectively. Collecting only the lower half of the corn plants required a second pass across the field and had a yield of only 1.0 and 1.5 Mg ha-1, respectively. That treatment also encountered several harvest problems due to clogging of the combine. Harvesting corn cobs and upper plant parts increased total carbon removal 1.8 or 2.2 Mg ha-1 compared to harvesting grain only. Structural sugars glucan and xylan accounted for up to 60% of the chemical composition, while galactan, arabinan, and mannose constituted less than 5% of the harvest fractions. We conclude that with current agricultural management practices, a portion of the corn stover being produced in central Iowa fields, like those we studied, can be harvested in a sustainable manner, but other areas must have the crop residue returned to maintain soil organic matter, sustain soil structure, and prevent wind and water erosion.