A TRIAL by Summit Fertilizers is determining how to optimise nitrogen and phosphorus use when budget is the determinant factor in a wheat cropping budget, as opposed to maximising production using agronomy.
Held in collaboration with the Liebe Group on the Reynolds family's North Miling property, the trial included an investigation into the possibility of delaying nitrogen application to reduce upfront risk and catch up when the season improves.
Summit Fertilizers area manager Saritha Marais said there was an emerging thought that traditional approaches to nitrogen management were leaving crops short, as evidenced by disappointing grain protein levels in recent seasons.
"Growers may be forgoing profit by playing the season late and not addressing crop demand early when yield potential is critically set," Ms Marais said.
"There has also been a recent survey showing that soil phosphorus is accumulating across the region with 70 per cent of soils having sufficient soil phosphorus levels.
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"Despite this, trials done by Summit Fertilizers are still showing response to increasing phosphorus rates."
Summit has conducted two trials, side-by-side, which will add value to the Liebe Group region by interrogating the traditional ideas of sufficient nutrition through pushing nitrogen and phosphorus rates to determine the profitability at the end of the season.
Both trial protocols have been completed by the company's field research previously, which enables them to compare the 2022 results with those of previous years in similar rainfall and soil types.
The idea is to also repeat similar trials in future years and continue to compare the data.
From the results so far, readings have demonstrated increases in plant biomass, by increasing phosphorus fertiliser up to eight kilograms per hectare.
Biomass then remained consistent up to 20kg/ha, before increasing again at 24kg/ha.
Ms Marais said as the season progressed, these trends were not as obvious due to the change in growth stages.
"Plant biomass was also increased with increasing nitrogen applications up to the highest rate of 120kg/ha," she said.
"At mid-late tillering, about July 12, treatments which had received nitrogen at the two to four leaf growth stage were almost identical to the biomass of crops which received nitrogen at seeding, and even greater where 120kg N/ha was applied.
"Further readings collected at the start of flowering, about August 19, encompassed the whole range of treatments and indicated similar findings, with split applications increasing biomass especially at lower rates of nitrogen."
Applying high rates of nitrogen after seeding presented some biomass advantage over receiving high rates at seeding.
