Ammonia volatilisation and N recovery of nitrogen fertiliser on former alpine grassland based on a nitrogen isotope labelling technique

摘要

Nitrogen fertiliser application can effectively increase the net primary productivity (NPP) of agriculture and grassland ecosystems. There is some long-term retention of nitrogen applied to soils, but much is lost to runoff, to in situ denitrification and to gaseous forms of nitrogen (such as NH3 and NOX). So it is particularly important to improve nitrogen-use efficiency through various ways. Therefore, the effects of the urea with urease inhibitor N-(n-butyl)thiophosphoric triamide (NBPT) or/and nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on the NPP, NH3 and N-15 recovery were researched on the alpine grassland ecosystem. The results showed that the addition NBPT to urea can significantly reduce the cumulative NH3 emission of urea-N compared with urea alone. The NBPT or DMPP addition to urea significantly increased the above-ground NPP and the economic efficiency. Urea added to NBPT or NBPT+DMPP could increase the N-15 recovery rate of plant and soil (0-40 cm) by nearly 20. The results indicated that urea combined with DMPP may be a good way to nitrogen fertiliser retention and reduction of NH3 emission for the alpine grassland of the northeast of the Qinghai-Tibet Plateau.