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If producers want to reduce their rates of fertiliser, high levels of soil fertility are essential, i.e. a high bank account. You are relying on soil P reserves to make up the difference from your reduced input. If soil P levels are below the critical value (in the central west around 25-35 mg/kg Colwell P in the top 10cm of soil) dropping our fertiliser rates below our historic input levels carries a very high risk of reduction in yield as we are simply limited by low P.
It makes sense if some producers want to trade this resource like any other. We can draw on soil P when fertiliser prices are high and then deposit more than is needed when those prices drop again. However, like all trading there is the increased risk that comes from speculating on markets. Some may consider it cheap insurance to simply use maintenance rates of P fertiliser and not be dependent on market fluctuations.
It is critical to soil test our paddocks so that we have a thorough understanding of our fertility and to help plan and budget how much fertiliser is needed.
Read the full article by Tim Bartimote and Rohan Leach
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