See more from this Session: Resource Management and Monitoring: Impact On Soils, Air and Water Quality and General Environmental Quality (Graduate Student Poster Competition)
Monday, October 17, 2011
Henry Gonzalez Convention Center, Hall C, Street Level
Urea is the cheapest and most commonly used form of inorganic N fertilizer worldwide, accounting for c. 50% of inorganic N use. Nevertheless, the low efficiency of N-urea use by crops represents a threat to environmental quality and public health. It has been estimated that up to 60% of N-urea applied could be lost to the atmosphere via ammonia (NH3), nitric oxide (NO) and nitrous oxide (N2O), and to water streams through nitrate (NO3-) leaching. Among the proposed mitigation strategies to prevent N losses from urea fertilizing, urease inhibitors have been shown to effectively reduce NH3 volatilization. Additionally, these compounds have been noticed to decrease the NO and N2O production rate under certain soil conditions. To evaluate the effectiveness of the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT, trade name Agrotain®) on mitigating N losses from arable crops under Mediterranean conditions, a set of field experiments were carried out between 2006 and 2011. Ammonia volatilization was measured with a micrometeorological technique in both sunflower and barley crops; losses of NO and N2O were determined by static chambers in corn and barley; leached NO3- was measured in the same crops. Urea and NBPT coated urea (0.14-0.20% w/w) were applied in granular form. The reduction in the hydrolysis rate promoted by the inhibition of urease activity leaded to 42-58% abatement of ammonia volatilization. Additionally, presence of NBPT decreased NO-N and N2O-N emissions from urea in 74% (i.e. 1.89 kg NO-N ha-1) and 55% (0.86 kg N2O-N ha-1) when nitrification was expected to be the main pathway in the production of these reactive N compounds. Finally, NBPT reduced N losses through NO3- leaching in 59% (i.e. 40 kg N ha-1) in a corn crop.