Ammonia volatilisation from nitrogen fertilisers surface-applied to bare fallows, wheat crops and perennial-grass-based pastures on Vertosols

Abstract

Farmers on Vertosols in the northern grains region of Australia are increasingly using pre-crop broadcasting and in-crop topdressing of nitrogen (N) fertilisers. Surface application risks gaseous loss via ammonia volatilisation, but the magnitude of N loss is unknown. Because both soil properties and environmental conditions influence ammonia volatilisation, measurements need to be field-based and non-intrusive, e.g. micrometeorological. We used an integrated horizontal flux technique to measure ammonia volatilised from neutral to alkaline Vertosols for a month after the application of several fertiliser products in 10 bare-fallow paddocks, seven mid-tillering wheat crops, and two perennial-grass-based pastures. Ammonia loss from urea averaged 11% (5.4–19%) when applied to fallow paddocks, 4.8% (3.1–7.6%) when applied to wheat, and 27% when applied to pasture. Volatilisation from urea applied to pastures was high, because there was little rain after spreading. Losses from ammonium sulfate applied to pastures were >60% less than from urea. Nitrogen losses from ammonium sulfate were high (18.6–33.8%) from soils with >10 g 100 g–1 of calcium carbonate (CaCO3), but were 52% less than from urea at five of eight fallow paddocks on non-calcareous soils, and 76% less than from urea at the two pasture paddocks. Coating urea with N-(n-butyl)thiophosphoric triamide reduced ammonia loss at just two of eight fallow paddocks and one of three in-crop paddocks. Ammonia volatilisation from aqueous solutions of urea, urea ammonium nitrate, and ammonium nitrate were either less than or no different from losses from granulated urea, but not consistent. With the exception of ammonium sulfate applied to soils with >10 g 100 g–1 of CaCO3, surface application of N fertiliser during autumn–winter on cropped Vertosols in the Australian northern grains region does not lead to major N loss via ammonia volatilisation.

Ammonia emissions from urea, stabilized urea and calcium ammonium nitrate: insights into loss abatement in temperate grassland

“…Also, the average urea‐N losses of 25.1 to 30.6% are similar to the 27% loss measured using the integrated horizontal flux (IHF) method by Schwenke et al . () from urea applied on neutral to alkaline grassland with limited or no precipitation for 2 weeks after application, conditions expected to promote NH 3 ‐N loss. Our sites were acidic (pH 5.6 at JC and 5.8 at HB), and significant precipitation was a common feature of many periods following the fertilizer application.…”

Nitrogen fertilization in top dressing for wheat crop in succession to soybean under a no-till system

“…When applied at a low rate, N can limit grain yield, whereas excessive N rate can cause plant lodging, making it difficult to harvest and reduce wheat yield (Schwenke et al 2014). In addition, the use of excessive N rate results in a high risk to the environment, leading to economic and environmental unsustainability of the agricultural system.…”

“…Because of high cost of N fertilizer for production crop, the use of N sources which promote lower N-NH 3 losses by volatilization, as calcium nitrate (CN) or ammonium sulfate (AS), would be a way to increase fertilizer efficiency and maximize wheat yield (Yano et al 2005;Teixeira Filho et al 2010;Prando et al 2013;Schwenke et al 2014). Since Ca exhibits synergism with N (Franco et al 2007), using an N source containing Ca could increase the N use efficiency by wheat.…”

“…Urea (UR) is the most produced and used N source in agriculture. However, depending on soil and weather conditions, considerable NH 3 -N losses by volatilization can occur following UR application on the soil surface (Soares et al 2012;Schwenke et al 2014). Wheat in Southern Brazil has been grown in no-till systems.…”

Polymer-Coated Urea Delays Growth and Accumulation of Key Nutrients in Aerobic Rice but Does Not Affect Grain Mineral Concentrations

“…Unfortunately, the N use efficiency of crop production is generally low, with crops rarely assimilating more than 50% of the fertilizer N applied [2]. While some of the fertilizer N is retained in the soil and may be available for uptake by subsequent crops, much of the N applied to crops and pastures is lost through leaching [3,4] or emitted as the gases NH 3 or N 2 O [5,6]. An unintended consequence of these losses is environmental damage, predominantly eutrophication of waterways due to N contamination, and increasing greenhouse gas emissions from agriculture as a result of N 2 O losses [2].…”