Mineral Nitrogen Availability from Ethanol Distillers By-Products.

Periodic availability of wet distillers grain (WDG) and condensed distillers solubles (CDS) from local ethanol plants has elicited interest of growers in using them as sources of plant nutrients. A series of 56-day incubations were conducted to determine the availability of NH₄⁺-N and NO₃^--N due to mineralization of soil applied WDG and CDS. The incubations were conducted with soil alone or with the presence of corn (C) or soybean (SB) residues. Initial mineralization was slow with apparent immobilization occurring during the first 14 days of the incubations. However, net mineralization occurring after 14 days increased to a maximum at 56 days. The presence of C or SB residues had little effect on net mineralization. Intense growth of fungi of the Mucorales order occurred within the first three days of the incubations and appeared to contribute to the initial N immobilization. The implications of the delayed immobilization on use of these by-product materials and plant nutrient sources will be discussed.