An assessment of the persistence and bioactivity of nitrification inhibitors on contrasting urine-treated pasture soils and the effect on soil microbial biomass

Grace Chibuike1, Surinder Saggar1,2, Thilak Palmada2, Jiafa Luo3

1School of Agriculture and Environment, Massey University, Palmerston North, 4442, New Zealand
2Manaaki Whenua – Landcare Research, Palmerston North, 4442, New Zealand
3Ruakura Agricultural Centre, AgResearch Ltd, Hamilton, 3240, New Zealand

Abstract
Nitrification inhibitors (NIs) play a key role in mitigating nitrogen (N) losses from pastoral agricultural systems. The effect of dicyandiamide (DCD) on reducing nitrous oxide (N2O) emissions from urine patches on pasture soils is well-documented. But there is no sufficient information on the effect of other most used NIs [3,4-dimethylpyrazole phosphate (DMPP), 2-chloro-6-(trichloromethyl) pyridine (nitrapyrin) and A (a confidential NI)] on reducing N2O emissions from urine-treated pasture soils, especially as influenced by NI persistence (changes in NI concentration with time) in the soil. Therefore, a laboratory incubation experiment was designed to test the persistence and bioactivity (the potential to inhibit nitrification at specific NI concentrations) of DMPP, nitrapyrin and A (using DCD as a reference NI) on urine-treated pasture soils varying in texture and organic matter. These soils are currently being incubated at 15°C and periodically measured for the soil NI concentrations; soil mineral-N concentrations;  N2O emissions; soil microbial biomass carbon and nitrogen (MBC and MBN)  to assess the persistence and half-life of the NIs on the contrasting soils,  determine their bioactivity and  to assess any unintended consequences of the NIs on soil microbes. The preliminary results of these measurements will be presented and discussed during this conference.
Keywords: DMPP, nitrapyrin, half-life, N2O emissions, unintended consequences
 
Acknowledgements: Grace Chibuike LEARN Post-Doc was funded by the New Zealand Government to support the objectives of the Global Research Alliance on Agricultural Greenhouse Gases, and this research was supported by Massey University and Manaaki Whenua – Landcare Research.  
