PHOSPHORUS inputs could be reduced when sowing into warm and moist soil, but adequate rates remain essential when sowing into cooler and drier soils.
These are two of the key messages from research funded by the South Australian Grain Industry Trust and conducted by Agronomy Solutions’ Dr Sean Mason, which aimed to determine the time of sowing influence on phosphorus reactivity and requirements.
Phosphorus is necessary for wheat growth and is often applied as fertiliser at seeding to increase yield.
Dr Mason said these findings could allow growers to more efficiently plan their fertiliser expenditure.
“Plants establish quickly in warm and moist soil, meaning they can more readily access residual phosphorus reserves in the soil,” he said.
“Although we haven’t had a wet start for a couple of years, this research has shown that in a year with a good season break there is the opportunity for growers to cut back on their phosphorus inputs if they are sowing into warm moist soil around Anzac Day.
“Greater root growth will boost the efficiency of phosphorous uptake and the crop will be less reliant on fertiliser.
“However, in a marginal year, drier sowing conditions or as soon as it becomes cooler, there needs to be more phosphorus fertiliser applied to boost root uptake of phosphorus.”
Phosphorus was shown to be essential in promoting maximum wheat growth in cooler and drier conditions.
“Our trial sites were selected for phosphorus responsiveness,” Dr Mason said.
“It is always good to monitor the soil characteristics and paddock conditions as there is variability in responsiveness.
“Trengove Consulting’s Sam Trengove is conducting more SAGIT-funded research into different zones in the same paddocks where responsiveness to phosphorus is highly variable.”
Dr Mason’s study also suggests the required phosphorus inputs to maximise yield are not always the inputs resulting in the best economic outcome, which varied with sowing time and the cost of phosphorus.
Gross margins were maximised when varieties were sown in their optimal window only if Phosphorus requirements were matched.
This research will assist growers in making informed decisions to maximise their profits.