CSBP Urea Sustain Trial Review

May 01,2024 Industry Article, 2024, Industry Update, Technical Article,

By Pete Rees, CSBP Senior Agronomist

Urea Sustain has been introduced to the market this season with the aim of improving growers Nitrogen use efficiency by minimizing nitrogen N losses to volatilization and leaching. The product is urea coated with urease and nitrification inhibitors. The urease inhibitor (NBPT) has been shown to boost yields in wheat by an average of 10.2% over urea in a 2018 review (Cantarella et al., 2018).

CSBP has conducted seven replicated trials comparing the effectiveness of Urea Sustain and urea as N sources for wheat in the 2022 and 2023 season. These were aimed at understanding N losses and any production benefits Urea Sustain may deliver in Western Australian conditions. While 2023 was a very dry season with limited nitrogen response, Urea Sustain boosted yields by an average of 5.6% over urea when compared across all seven trials. Urea Sustain also tended to increase proteins, lifting protein by 0.3% over urea treatments. Protein gains were highest at higher N rates, with 84 and 126 kg N/ha lifting protein by 0.7-1.0%.

**Figure 1**. Relative yield benefits from Urea Sustain compared to urea when top dressed at Z11-13. Coloured dots are means of three field replicates comparing equal N rates. Boxplots show the interquartile range and medians (vertical lines).

The responses to Urea Sustain were highest in higher yielding, more N responsive environments. In 2022 our Three Springs trial showed a 700 kg/ha yield and 0.95% protein response at the highest N rate (84 kg/ha).

**Figure 2.** Wheat yield (t/ha) and grain protein (%) responses to N rates supplied as Urea Sustain or urea topdressed at Z11-13 at Three Springs in 2022.

While in Cascades in 2023 we saw an 800 kg/ha yield response, as well as a 2.3% increase in protein at the highest N rate of 126 kg/ha.

**Figure 3.** Wheat yield (t/ha) and grain protein (%) responses to N rates supplied as Urea Sustain or urea topdressed at Z11-13 in Cascades in 2023.

CSBP plans to continue field trials to understand how Urea Sustain performs in a variety of seasons, as well as supplementary laboratory work to quantify the reduction in volatilization losses over standard urea and soil testing to quantify any differences in carry over N that could be attributed to Urea Sustain usage.

Heitor Cantarella, Rafael Otto, Johnny Rodrigues Soares, Aijânio Gomes de Brito Silva, Agronomic efficiency of NBPT as a urease inhibitor: A review, Journal of Advanced Research, Volume 13, 2018.