Environmental Fate of Nutrients From Ethanol Production Byproducts for Use in Sugarcane Nutrition.

Determination of plant nutrient fluxes from land application of ethanol stillag (vinasse) as a nutrient source for sugarcane production is critical because of its potential impact on soil water quality. Two field studies were conducted in 2010 and 2011 in FL with two soil series (Spodosol and Histosol) using soil lysimeters. Treatments were: 1) dry soluble fertilizer; 2) vinasse at 100% of the soluble K rate and dry soluble N, P, and (3) vinasse at 150% of the soluble K rate and dry soluble N, P. Treatments contained similar N and P amounts and were replicated four times in a randomized complete block design. Leachate water samples were collected from all treatments after rain events and analyzed for different elements to calculate nutrient loads. Objectives of the studies were 1) chemical characterization of stillage for use as a nutrient source and 2) determination of nutrient leaching potential. Data showed that nitrogen load was greater for the Histosol compared with the Spodosol. Nitrogen load did not differ significantly among treatments at Histosol indicating the source of the leached N was from mineralized organic matter. Leachate P, K, Fe and Mn loads at harvest were approximately ten, three, five and five times greater, respectively, for the Spodosol site compared with the Histosol site. Whereas, Ca and Mg loads are about two times greater from the Histosol site compared with the Spodosol site. Preliminary conclusions would be that K, P, Fe and Mn are leached much faster from the sandy soils with low cation exchange capacity. The greater leaching of Ca and Mg at the Histosols site may indicate that these soils do not retain these elements or, and more likely, these soil release Mg and Ca through mineralization of the organic matter that makes up a large proportion of those soils.