Ammonia emissions from a soil amended with urea and inhibitor of urease activity in a Mediterranean area

Abstract

Urea and ammonium-based fertilisers are nowadays one of the most important sources of ammonia (NH3) emissions to the atmosphere in Europe. However, little is known about NH3 volatilisation in Mediterranean areas. The aim of the present study was the quantification of NH3 emissions by using the Integrated Horizontal Flux (IHF) method after application of urea with the urease inhibitor N-(n-butyl) thiophosphorie triamide (NBPT) to a semiarid agricultural soil. The field experiment was carried out at "La Poveda" field station in Madrid on a sunflower crop in spring 2006. Urea and a mixture of urea and the inhibitor (0.14%) were surfaee-applied by hand at a rate of 170 kg N ha"' to eircular plots (diam. 40 m). The soil was irrigated with 10 mm of water just after the applieation of urea to dissolve and incorporate it onto the first layer of soil. There were three peaks in the NH3 flux over the duration of the measurement period (36 d). The first peak was associated to irrigation and the others to rainfall events. The total NH3 emission during the whole experiment (36 days) was 17.3 ±5.5kgNH3-N ha"1 in the ease of urea treated soils and 10.0 ± 4.5 kg NHrN ha"' where NBPT was ineluded with the urea.