SHORT COMMUNICATION: Volatile losses of NH₃ from surface-applied urea and urea ammonium nitrate with and without the urease inhibitors NBPT or ammonium thiosulphate

Abstract

Field microplot studies were conducted under zero-till conditions on a fine sandy loam (Orthic Black Chernozem) to determine the effect of the urease inhibitors N-(n-butyl) thiophosphoric triamide (NBPT) and ammonium thiosulphate (ATS) on volatile losses of NH3 from urea and urea ammonium nitrate (UAN). Two studies were conducted, one in late May and one in early August. Losses of NH3 were measured on days 1, 2, 4 and 7 after fertilizer application, using ammonia traps. Ammonia losses were higher in the second study due to the higher soil temperatures and lower soil moisture later in the growing season. Total NH3 losses increased in the order Control < UAN + NBPT = Urea + NBPT < UAN + ATS = UAN < Urea. Total loss of NH3 during the 7 d after fertilizer application was higher from urea than from UAN, particularly in the first study. Use of NBPT was effective in reducing NH3 volatilization from both UAN and urea during 7 d after fertilizer application while use of ATS had little influence on NH3 loss from UAN. The NBPT may delay losses by slowing the hydrolysis of urea, but volatilization may persist for a longer duration. The delay in urea hydrolysis could allow time for rainfall to carry the urea into the soil, thus reducing total volatilization losses from surface fertilizer application. Key words: N-(n-butyl) thiophosphoric triamide, zero tillage

Fallow replacement and alternative nitrogen management for reducing nitrate leaching in a semiarid region

“…Broadcast urea volatilization amounts were estimated at 14% of applied N based on measured average ammonia volatilization losses from early spring (Mar 24-Apr 20) applications for eight central and north central Montana trials, including three within the JRW (Engel et al 2011;Engel and Jones 2014). For both years, it was assumed that seed placed starter and CRU fertilizer did not volatilize, and that 7% of liquid UAN volatilized based on a Manitoba, Canada study conducted in late May (Grant et al 1996). The change in soil nitrate storage (soil nitrate final -soil nitrate initial ) was defined as the difference in total soil core sample nitrate-N pools between each post-harvest sampling period.…”

“…40-200 days during 2012-2013. Because these were fallow periods, fertilizer input and N-uptake were known to be zero, and there were likely negligible amounts of volatilization (Grant et al 1996) and deposition. Based on water budgets, nitrate leaching out of the depth interval sampled was also assumed to be zero; specifically, evapotranspiration estimated from flux tower measurements on and near Field C (Vick et al 2016) was greater (within uncertainty) than the precipitation amount minus the change in soil water storage (final-initial) during the seven subfield-periods.…”

Ammonia volatilization from soils fertilized with urea and varying rates of urease inhibitor NBPT

“…The treatments consisted of 100 kg urea N ha -1 at rates of 0, 0.05, 0.10 and 0.15% NBPT wt/wt supplied as Agrotain (IMC-Agrico) and a control treatment (no fertilizer or NBPT). Study design and NH 3 capture and analysis procedures followed Grant et al (1996). White polyvinyl chloride (PVC) cylinders, 200 mm in length by 150 mm diameter, were inserted 50 mm into the soil with minimal soil disturbance.…”

Increasing NBPT rates to reduce ammonia volatilization losses from urea applied over sugarcane straw

“…Urease inhibitor is a compound that, when added to fertilizer, retard urea hydrolysis. This increases the time available to a rainfall occur and incorporate urea, reducing the NH3 + formation near soil surface and hence reducing the NH3 loss potential (GRANT et al, 1996;WATSON et al, 2008). The NBPT is not a direct urease inhibitor.…”

“…The lower rate of hydrolysis avoids sharp pH rises around the fertilizer granule as well as the formation of high concentrations of NH3 in topsoil. In addition, it ensures a longer time for urea interaction with the soil and occurrence of rainfall to move the urea downwards, thus, reducing the NH3 loss potential (BOUWMEESTER; VLEK; STUMPE, 1985;STEVENS;LAUGHLIN, 1990;GRANT et al, 1996).…”