Agricultural residues from annual crops such as wheat (Triticum aestivum) straw, soybean (Glycine max) straw and corn (Zea mays) are being considered as potential feedstock’s for a range of uses including bioenergy, biochemicals, and bioproducts (Duguid, 2010; Kludze et al., 2010). Interest in using biomass for these purposes has dramatically increased in recent years.
A recent study has determined that wheat (Triticum aestivum) straw, soybean (Glycine max) straw and corn (Zea mays) residue removal from existing corn-soybean and corn-soybean-wheat rotations in Ontario could sustainably provide 1,919,802 tons of dry matter per year (Kludze et al., 2010), without negatively impacting soil organic matter levels. This is a much smaller volume than previously estimated or actually available across Ontario under present acreages and yields.
Two issues need to be considered with respect to nutrient removal in crop residues. The first issue relates to the economic implications of nutrient removal (i.e. nutrient removed per unit area) . High nutrient removal rates increases input costs, as synthetic fertilizers must be purchased to replace nutrients removed in the plant material. Nutrient costs are increasing over time. Fertilizer costs increased 23 percent between May of 2010 and 2011 (McEwan, 2011b), and increased another 4 percent between June 8 and October 5, 2011 (McEwan, 2011a). Thus, nutrient removal rate should be kept as low as possible. The second issue relates to biomass quality. Nutrient concentration (i.e. nutrient content per unit of biomass), depending on the end-use of the biomass, may negatively or positively impact feedstock quality considerations. For example, high potassium content is undesirable if the biomass is to be used for combustion, since potassium can contribute to corrosion and slagging during burning.
Nutrient removal and concentration in crop residue may be influenced by management, weather and soil type. The nature and causes of crop residue nutrient removal and concentration have not been documented for Ontario. Understanding and quantifying this variability and its causes, as well as understanding the proposed methods of altering residue nutrient removal and concentrations is required to better meet the demands of an emerging biomass industry. Such data would assist the emerging industry in minimizing both economic costs of removal for producers and also potential costs to end-users.
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