CEREAL and canola growers and graziers can maximise returns on their fertiliser investment by using a urease inhibitor to reduce nitrogen losses from volatilisation in favourable growing seasons like this one, according to Incitec Pivot Fertilisers (IPF) senior technical agronomist Jim Laycock.
Volatilisation is the process of nitrogen (N) being lost from the soil surface as ammonia (NH3) gas.
In dryland winter crop environments, volatilisation losses from urea can be anywhere from 3 per cent 23pc and losses in pastures can be as high as 30pc.
Mr Laycock said how much N is lost to NH3 depended on a range of factors.
“N is essential for dry matter production, shoot density and potential yield in cereals,” Mr Laycock said.
“Factors which favour NH3 losses from top-dressed urea include light rain post application where there is enough to dissolve the urea granule, but not enough to wash the dissolved granule into the soil.
“Other key factors include crop residue on the soil surface, temperatures above 18 degrees Celsius, alkaline soils, wind, lighter sandy loams, and application to a moist soil that dries after application.”
Mr Laycock said N loss effects can be widespread, and can cost the grower with lost production and/or lower return on investment for applied fertiliser.
“Research has shown volatilisation losses from urea vary greatly between production systems and environments and can be significant.
In areas where volatilisation may occur, growers and producers can use Green Urea NV, a granular urea treated with a urease inhibitor to reduce volatilisation for up to 14 days after application to ensure nitrogen is still present for the next rainfall event.
“This process ensures nitrogen is available for the plants and reduces ammonia emissions.
The active ingredient in Green Urea NV is N (n-butyl) thiophosphoric triamide (NBPT), which slows the conversion of urea to ammonium.
IPF has developed a patented NBPT formulation known as Lockdown, which improves the active ingredient’s stability when applied to urea, and a range of field studies have demonstrated the benefits of NBPT.
Wheat productivity and nitrogen use efficiency was measured at three sites in the Wimmera region of Victoria between 2012 and 2014, and NBPT increased yield by 7-11 per cent in two of three years when compared to unamended urea.
In other field studies, the N management strategy significantly affected losses of fertiliser N depending on seasonal conditions, with NBPT producing significant benefits in reducing losses of top-dressed urea under dry seasonal conditions.
IPF’s trial work in the Mallee in 2014 also demonstrated the effectiveness of Green Urea NV over urea with an early September topdress and 17 days before a welcome rainfall event of 35 millimetres.
The Green Urea NV treatment returned a significant grain-yield response over urea of 41o kilograms per hectare, a protein response of 0.7pc and improved nitrogen use efficiency from 33.7pc for urea to 60.5pc for Green Urea NV.
By reducing N loss from volatilisation, applying Green Urea NV may allow growers to reduce urea rates.
“When topdressing large acreages, topdressing can commence four to six days before a significant rainfall event with confidence that all the nitrogen is still available for incorporation into the soil profile when that rain front comes through.
“All farming systems should aim to maximise nutrient-use efficiency.
“When choosing the most appropriate product to apply, consideration should be given to the rate of application, the frequency of application, the timing of the application, the economic objectives, and any environmental consequences.”