Using DMPP with cattle manure can mitigate yield-scaled global warming potential under low rainfall conditions

Abstract

Organic fertilisers can reduce the carbon (C) footprint from croplands, but adequate management strategies such as the use of nitrification inhibitors are required to minimise side-effects on nitrogen (N) losses to the atmosphere or waterbodies. This could be particularly important in a context on changing rainfall patterns due to climate change. A lysimeter experiment with maize (Zea mays L.) was set up on a coarse sandy soil to evaluate the efficacy of 3,4-dimethylpyrazole phosphate (DMPP) to mitigate nitrous oxide (N2O) emissions, nitrate (NO3−) leaching losses and net global warming potential from manure, with (R+) and without (R-) simulated rainfall events. Soil water availability was a limiting factor for plant growth and microbial processes due to low rainfall during the growing season. Nitrification was effectively inhibited by DMPP, decreasing topsoil NO3− concentrations by 28% on average and cumulative N2O losses by 82%. Most of the N2O was emitted during the growing season, with annual emission factors of 0.07% and 0.95% for manure with and without DMPP, respectively. Cumulative N2O emissions were 40% higher in R-compared to R+, possibly because of the higher topsoil NO3− concentrations. There was no effect of DMPP or rainfall amount on annual NO3− leaching losses, which corresponded to 12% of manure-N and were mainly driven by the post-harvest period. DMPP did not affect yield or N use efficiency (NUE) while R-caused severe reductions on biomass and NUE. We conclude that dry growing seasons can jeopardize crop production while concurrently increasing greenhouse gas emissions from a sandy soil. The use of nitrification inhibitors is strongly recommended under these conditions to address the climate change impacts.