Short-term effects of nitrapyrin, rice straw and its biochar application on N transformation in soils of humid subtropical China

Abstract

ABSTRACTThe features of N transformations in humid subtropical soils vary greatly due to the wide variations of soil properties, particularly soil pH. Purpose: To understand whether the effects of countermeasures regulating N transformation varied with the prevailing soil N transformation characteristics. Materials and methods: The effects of nitrapyrin, rice straw and its biochar applications on N dynamics at the beginning stage (first 24 h) of a zonal acid soil (JX soil, pH 5.26) and a non-zonal alkaline soil (SC soil, pH 7.62) from the humid subtropics in China were investigated via a 15N tracing laboratory incubation. Results and conclusions: Rice straw incorporation affected almost all processes involved in and production and consumption, and decreased the net mineralisation and nitrification rates in both soils significantly. Nitrapyrin decreased the net nitrification rates in both studied soils by affecting different N transformation processes. In the SC soil, nitrapyrin reduced the net nitrification rate by inhibiting the gross autotrophic nitrification rate while the gross autotrophic nitrification in the JX soil was negligible and nitrapyrin decreased its net nitrification via a stimulation of the gross rate of dissimilatory nitrate reduction to ammonium (DNRA). Biochar stimulated the gross rates of mineralisation, immobilisation, autotrophic nitrification and DNRA significantly, but did not affect the net mineralisation and nitrification rates in both soils. Countermeasures to regulate N transformations are tightly linked to the prevailing soil N transformation characteristics and should be taken into account for the recommendation of suitable management options.