Development of Sustainable Corn Stover Feedstock Supply Strategies

The rising global energy demand has increased the importance of developing sustainable land management strategies. In response, the Renewable Energy Assessment Project (REAP) was begun to quantify the sustainability of harvesting corn (Zea mays L.) stover and other materials for bio-energy. REAP objectives are to: (1) determine the amount of crop residue needed to protect soil resources, (2) compare tradeoffs for biomass as a bio-energy feedstock versus a soil carbon source, and (3) provide recommendations and guidelines for sustainable biomass harvest. Effects of crop residue harvest on ecosystem services are being quantified using soil quality assessments. Field studies are being conducted to quantify interactions between crop residue harvest and practices including row spacing, plant population, fertilization rate, application of bio-char, and cover crops. Among the metrics used for assessing impacts on ecosystem services, the Soil Management Assessment Framework (SMAF) is one tool that is being used to help interpret data from the various sites. Near Ames, IA, a one-pass harvesting system was used to collect grain and (1) the top 50% of the plant, (2) bottom 50% of the plant, (3) all harvestable stover, or (4) no stover in 2005, 2006 and 2007 from continuous and rotated corn production sites. Soil samples collected when the project was initiated showed low soil-test P and K that may have limited crop yield after the first year of residue removal. Harvesting the cobs and upper portion of the plant provided 4.5 to 5.6 Mg ha-1 of lignocellulosic feedstock, leaving approximately 3.3 to 4.5 Mg ha-1 for soil protection and C input. Soil cores collected following the 2007 harvest are being analyzed and interpreted using the SMAF. Through this work we aim to develop an integrated, landscape-scale approach for bioenergy production and co-product use that incorporates several plant species, conversion technologies, and conservation practices.