Effects of biotechnology byproducts and organic acids on nitrification in soils

Summary

Recent developments in biotechnology industries produce increasing amounts of byproducts with potential uses in agriculture. The present research focused on the nitrification of NH ^sup+_inf4 -N in biotechnology byproducts added to soils, and on the effects of 29 naturally occurring organic acids (19 aliphatic and 10 aromatic) on nitrification in soils. A 10-g soil sample was incubated for 10 days at 30°C with 2.0 mg NH ^sup+_inf4 -N in a byproduct or with 10 or 50 μmol organic acid and 2.0 mg reagent-grade NH ^sup+_inf4 -N. In condensed molasses-fermentation solubles, produced during the microbial fermentation of sugar derived from corn (Zea mays L.) and molasses derived from beets (Beta sp.), in the production of lysine as a supplement in animal food, the nitrification of NH ^sup+_inf4 -N was similar to that of byproduct or reagent-grade (NH₄)₂SO₄. Nitrite accumulated when either of these materials was added to a calcareous Canisteo soil. The NH ^sup+_inf4 -N in slops (produced during microbial fermentation processes occurring in the production of citric acid) was not nitrified in soils. Some organic acids inhibited, whereas others activated, nitrification in soils. Formic, acetic, and fumaric acids enhanced the production of NO ^sup-_inf2 -N in a calcareous Canisteo soil, whereas all other aliphatic and aromatic acids studied decreased the accumulation of NO ^sup-_inf2 -N. It is concluded that the addition or production of organic acids in soils affects the microbial dynamics, leading to significant changes in rates of nitrification and possibly in other N-transformation processes in soils.