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TECHNICAL REPORTS

Effect of N-(n-butyl) Thiophosphoric Triamide and 3,4 Dimethylpyrazole Phosphate on Gaseous Emissions from Grasslands under Different Soil Water Contents

^a Dep. of Plant Biology and Ecology, Univ. of the Basque Country, Apdo. 644. E-48080 Bilbao, Spain
^b Inst. of Agricultural Research and Development, NEIKER. B° Berreaga, 1. E-48160 Derio, Bizkaia, Spain

^* Corresponding author (sergio.menendez{at}ehu.es).

Received for publication January 21, 2008. The intensification of grassland systems is leading to serious environmental risks due to the large input of nitrogen (N) in fertilizers and the subsequent gaseous losses. Addition of nitrification inhibitors (NI) or urease activity inhibitors to fertilizers could reduce these losses to the atmosphere. In the present study, the effects of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) and the urease activity inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) were evaluated on NH₃, N₂O, NO, and CO₂ emissions. Ammonium sulphate nitrate (ASN), urea and cattle slurry were applied at a rate of 70 kg N ha^–1 to a mixed clover-ryegrass sward in the Basque Country (northern Spain) under different soil water contents. NH₃ and NO emissions were determined by photoacoustic and chemiluminescence respectively using an open chamber technique while N₂O and CO₂ emissions were measured by photoacoustic using a closed chamber technique. When the water filled pore space (WFPS) was under 60%, the application of NBPT reduced NO emissions a 34% on urea and an 18% on slurry, and the application of DMPP reduced them a 2% on ASN and a 4% on slurry. No significant effect was observed on NH₃ losses. When WFPS was over 60%, no effect could be observed on NO and N₂O emissions after the application of both inhibitors, but NH₃ losses were reduced a 31% by NBPT when applied with the slurry. Carbon dioxide emissions were unaffected by the use of DMPP or NBPT at any soil water content. Neither grassland yield nor herbage N concentration were influenced by the application of both inhibitors.

Abbreviations: ASN, ammonium sulfate nitrate • DM, dry matter • DMPP, 3,4-dimethylpyrazole phosphate • NBPT, N-(n-butyl) thiophosphoric triamide • NI, nitrification inhibitors • WFPS, water-filled pore space