Biochemistry of nitrification in soil

Abstract

The kinetics of conversion of NH4+ to NO3- in soil were detd. by a perfusion technique and found to follow a sigmoid curve given bythe equation log [image] K(t [long dash]t 1) where y = nitrate [long dash]N pro-A [long dash]y duced/g soil, A = asymptotic value reached by y, t = time (days) from start of perfusion, t1 = time when y = 1/2 A, K = constant. This expression may be deduced from the hypothesis that soil nitrification is entirely due to the activity of proliferating cells. The oxidation of NO2 - to NO3 - proceeds faster than the oxidation of NH4 + to NO2 - under similar conditions. Poisons with inhibitory effects on cell metabolism greatly suppress soil nitrification. Chloretone (0.4%) produces 100% and ethylurethane (0.1%) over 90% inhibition; the effect being reversible. Inhibitory effects of NaCN, quin-hydrone, and CH20 are not quickly reversed by washing the soils.