Corn and soil response to application of ash generated from gasified alfalfa stems

Electricity generation from biomass is becoming a more environmentally sound option than nonrenewable fuels. Pilot studies have demonstrated that alfalfa (Medicago sativa L.) stems are a suitable feedstock for energy generation via gasification. Developing beneficial uses for ash produced as a byproduct will enhance the economic viability of bioenergy. A greenhouse study was conducted to evaluate the potential use of alfalfa ash as a fertilizer and/or liming agent using corn (Zea mays L.). Two soils, a Hubbard sand (low pH, low K, and high P), and a Barnes clay loam (high pH, high K, and low P) were used. Treatments included a control, K and/or P fertilizers, and six ash rates ranging from 0.2 to 6.4 g kg^-1 (450 to 15,000 kg ha^-1). Ash application significantly increased K and decreased Mg concentrations in corn. However, neither plant P nor trace elements were affected by ash application. Elemental uptake by plants paralleled their respective concentrations. Soil pH increased linearly in the Hubbard soil with ash but was not affected in the Barnes soil. Ash application significantly increased salinity, Cl, extractable P, exchangeable K, Ca, Mg, and Na in both soils. Ash from gasified alfalfa stems seems to be a potential source of K and a potential liming agent for acid soils. When used at agronomically reasonable rates, alfalfa ash did not pose any risk of excessive accumulation of metals tested in soil or plants.