Potassium and Sulfur Availability and Lime Potential of Ash Co-Product of Corn Cellulosic Ethanol Processing.

Research needs to be done on the potential as a soil amendment for lignin-derived ash, co-product of corn cellulosic materials for ethanol production and additional energy through combustion. Calcium carbonate and sodium bicarbonate were added during the combustion process as abatement materials to reduce NOx and SOx emissions. Laboratory analyses of the ash indicated a potential liming value and higher K and S concentrations compared with other nutrients. The value of the ash to supply K and S and to increase soil pH was evaluated at two field experiments in Iowa each lasting two-years compared with commonly applied sources of K (KCl) and S (gypsum) and pure calcium carbonate as references. Each experiment consisted of trials for K, S, and lime value. In spring 2014, each trial received five nutrient or calcium carbonate equivalent (CCE) application rates with ash and each reference material. Plots were evaluated in the second year for residual effects of the first-year applications. Corn was planted in 2014 and soybeans in 2015. Soil samples (15-cm depth) were taken before treatment application, at the V6 stage of corn, after corn harvest, and at the V5 stage of soybean. Soil was analyzed for K, S, and pH based on their respective trials. Corn ear-leaf samples were taken at the R1 stage and the uppermost mature soybean leaves were taken at the R3 stage. There were large K effects on grain yield, soil K, and leaf K; small or no S effects on yield but large effects on extractable soil sulfate S at V6 the first year and on leaf S concentrations; and large soil pH increases with both sources. There were inconsistent and small differences between sources except for soil and leaf S, when responses were greater for gypsum than for ash. The results showed the ash co-product is able to supply K and raise soil pH, which will increase the value of cellulosic energy production, but further research is warranted for S supply.