Ammonification and Nitrification of N as Influenced by Soil pH and Previous N Treatments

Abstract

The effect of soil pH on rates of ammonification and nitrification was studied. Soil samples which ranged in pH from 4.7 to 6.6 from an established lime and N fertility experiment were used. Soil pH values in the lime plots have been relatively constant for several years. Soil pH did not affect rates of ammonification appreciably; however it had a significant effect on nitrification rates. Length of the delay period (t′) was increased and rate of NO₃^‐ accumulation (Km) decreased with a decrease in soil pH. Previous field N treatments increased the length of t′ at low pH and decreased t′ and Km at high pH. Nitrification rates and production of NO₃^‐ were similar for soil pH values of 5.3, 6.0, 6.3, and 6.6 with a different pattern at pH 4.7.