Effects of Urease an D N Itrification in Hibitors on Yield S an D Emission S in Grasslan D an D Sprin G Barley (original) (raw)
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Science of The Total Environment, 2016
The accelerating use of synthetic nitrogen (N) fertilisers, to meet the world's growing food demand, is the primary driver for increased atmospheric concentrations of nitrous oxide (N 2 O). The IPCC default emission factor (EF) for N 2 O from soils is 1% of the N applied, irrespective of its form. However, N 2 O emissions tend to be higher from nitrate-containing fertilisers e.g. calcium ammonium nitrate (CAN) compared to urea, particularly in regions, which have mild, wet climates and high organic matter soils. Urea can be an inefficient N source due to NH 3 volatilisation, but nitrogen stabilisers (urease and nitrification inhibitors) can improve its efficacy. This study evaluated the impact of switching fertiliser formulation from calcium ammonium nitrate (CAN) to urea-based products, as a potential mitigation strategy to reduce N 2 O emissions at six temperate grassland sites on the island of Ireland. The surface applied formulations included CAN, urea and urea with the urease inhibitor N-(nbutyl) thiophosphoric triamide (NBPT) and/or the nitrification inhibitor dicyandiamide (DCD). Results showed that N 2 O emissions were significantly affected by fertiliser formulation, soil type and climatic conditions. The direct N 2 O emission factor (EF) from CAN averaged 1.49% overall sites, but was highly variable, ranging from 0.58% to 3.81. Amending urea with NBPT, to reduce ammonia volatilisation, resulted in an average EF of 0.40% (ranging from 0.21 to 0.69%)-compared to an average EF of 0.25% for urea (ranging from 0.1 to 0.49%), with both fertilisers significantly lower and less variable than CAN. Cumulative N 2 O emissions from urea amended with both NBPT and DCD were not significantly different from background levels. Switching from CAN to stabilised urea formulations was found to be an effective strategy to reduce N 2 O emissions, particularly in wet, temperate grassland.
Soil Use and Management, 2015
Fertiliser nitrogen (N) contributes to ammonia (NH 3) emissions, which European Union member states have committed to reduce. This study evaluated NH 3-N loss from a suite of N fertilisers over multiple applications, and on gaining insights into the temporal and seasonal patterns of NH 3-N loss from urea in Irish temperate grassland using wind tunnels. The fertilisers evaluated were: calcium ammonium nitrate (CAN), urea, and urea with the N stabilisers N-(n-butyl) thiophosphoric triamide (NBPT), dicyandiamide (DCD), DCD+NBPT, and a maleic and itaconic acid polymer (MIP). 200 (and 400 for urea only) kg N/ha/yr was applied in five equal applications over the growing season at two grassland sites (one for MIP). Mean NH 3-N losses from CAN were 85% lower than urea which had highly variable loss (range 45% points). The effect of DCD on NH 3 emissions was variable. MIP did not decrease loss but NBPT caused a 78.5% reduction, and when combined with DCD, a 74% reduction compared with urea alone. Mean spring and summer losses from urea were similar, although spring losses were more variable with both the lowest and highest loss levels. Maximum NH 3-N loss usually occurred on the second day after application. These data highlight the potential of stabilised urea to alter urea NH 3-N loss outcomes in temperate grassland, the need for caution when using season as a loss risk guide and that urea hydrolysis and NH 3-N loss in temperate grassland is rapid. Micrometeorological measurements focused specifically on urea are needed to determine absolute NH 3-N loss levels in Irish temperate grassland.
Agriculture Ecosystems & Environment, 2008
Urea is an important source of ammonia (NH 3 ) emissions to the atmosphere from agricultural soils. Abatement strategies are necessary in order to achieve NH 3 emission targets by reducing those emissions. In this context, a field experiment was carried out on a sunflower crop in spring 2006 with the aim of evaluating the effect of the N-(n-butyl) thiophosphoric triamide (NBPT) in the mitigation of volatilized NH 3 from a urea-fertilised soil. Ammonia emission was quantified, using the integrated horizontal flux (IHF) method, following application of urea with and without the urease inhibitor NBPT. Urea and a mixture of urea and NBPT (0.14%, w/w) were surface-applied at a rate of 170 kg N ha À1 to circular plots (diameter 40 m). The soil was irrigated with 10 mm of water just after the application of urea to dissolve and incorporate it into the upper layer of soil. Over the duration of the measurement period (36 days) three peaks of NH 3 were observed. The first peak was associated with hydrolysis of urea after irrigation and the others with the increase of ammonia in soil solution after changes in atmospheric variables such as wind speed and rainfall. The total NH 3 emission during the whole experiment was 17.3 AE 0.5 kg NH 3 -N ha À1 in the case of urea treated soils and 10.0 AE 2.2 kg NH 3 -N ha À1 where NBPT was included with the urea (10.1 and 5.9%, respectively, of the applied urea-N). The lower NH 3 emissions from plots fertilised with urea + NBPT, compared with urea alone, were associated with a reduction in urease activity during the first 9 days after inhibitor application. This reduction in enzymatic activity promoted a decrease in the exchangeable NH 4 + pool. #
Ammonia emissions from urea application to permanent pasture on a volcanic soil
Atmospheric Environment, 2012
Agriculture is the largest source of ammonia (NH 3) emission to the atmosphere, deriving mainly from livestock urine and manures, but fertilizer applications to pastures and crops also represent an important source. In Chile, where agriculture and cattle production are important activities (accounting for 4.5% of GDP along with the forestry sector), there are very few published data regarding NH 3 emissions from pasture and crop fertilization. This study aimed to provide the first empirical field data for Chile on N losses due to NH 3 volatilization following urea application to permanent pasture on a volcanic soil and to assess the influence of environmental conditions on emissions. Four field experiments were carried out on a volcanic acid soil using the micrometeorological integrated horizontal flux (IHF) mass balance method. Measurements were made in winter 2005 and 2007, and spring 2007 and 2008 following urea N fertilization to a permanent pasture at a rate equivalent to 100 kg N ha À1. Cumulative NH 3 emissions over the measurement period were 1.4 and 7.7 kg N ha À1 for winter applications, and 12.2 and 26.7 kg N ha À1 for spring dressings. These N losses due to NH 3 volatilization are within the range of emissions reported elsewhere. Consideration of urea application timing in Chile, with regards to weather and soil conditions, could have important consequences on minimising potential N losses via volatilization with associated financial benefits to farmers.
A new inventory of ammonia emissions from Irish agriculture
Atmospheric Environment, 2003
Agriculture plays a vital role in the Irish economy, accounting for 3.5% of the gross domestic product (GDP) in 2000. Grassland farming and, in particular, cattle rearing and dairying accounts for more than 90% of farming activity. In addition, there have been significant increases in the number of sheep, pigs and poultry over the last twenty years. As a consequence, gaseous nitrogen (N) emissions have shown a clear upward trend. Following the adoption of the United Nations Economic Commission for Europe (UNECE) Gothenburg protocol (Protocol to the 1979 convention on longrange transboundary air pollution to abate acidification, eutrophication and ground-level ozone. United Nations Economic Commissions for Europe (UNECE), Geneva.), Ireland has to achieve a 9% reduction in national ammonia (NH 3 ) emissions between 1990 and 2010. The agricultural sector accounts for virtually all NH 3 emissions in Ireland. It is on this basis that a new inventory of NH 3 emissions from agriculture has been produced. This paper describes the adoption of the UK national inventory model to Irish agricultural systems, the results of model calculations and the measures available to enable compliance with national targets and areas within the inventory, which require further investigation. Estimated total emissions from Irish agriculture were 89.9 and 91.8 kt NH 3 -N for 1991 and 2010, respectively. Cattle farming accounts for more than 75% of total emissions. The largest emission factors found included 46.9 g NH 3 -N lu À1 d À1 for cattle housing, 29.5 g NH 3 -N lu À1 d À1 for pig housing and 150 g NH 3 -N lu À1 d À1 for housed broilers (lu being equivalent to 500 kg live weight). In addition, model predictions for the year 2010 showed that without any abatement strategies being implemented, NH 3 emissions would exceed the agreed national emission reduction target by 12%. It was also found that strategies for reducing emissions from the land spreading of manure offer the greatest potential to achieve target levels. r