Facts and local knowledge must steer fertiliser use
Recently prominent fertiliser researcher Prof. Mike McLaughlin who heads the Fertiliser Technology Research Centre at the University of Adelaide had a clear message about the efficiency of following facts when addressing members of the AFSA in Adelaide
Armed with facts about the make-up and likely outcomes associated with different fertilisers, producers will be in the best position to make decisions.
Also important is knowledge of soil types in each locality and potential effects of nutrient applications. For example it has been long known that micro nutrients are less available where there is high pH, but much more is now understood about soil reactions with fertilisers and their various formulations thanks to research.
Prof. McLaughlin referred to relying on someone else’s testimonial about a product, or being persuaded to switch to a new untested product when the prices of conventional fertilisers increase, as unsound.
‘It is best to seek as much information as we can find and base decisions on scientific evidence,’ he said.
[Sources of information include the Fertiliser Technology Research Centre website www.adelaide.edu.au/fertiliser, the Grains R&D website www.grdc.com.au, and your local agronomist]
Advances have been made on many fronts including the evaluation of P use efficiency, our understanding of reactions to P fertilisers in soils, soil factors that affect nutrient availability and management of fertiliser applications. There have also been advances in technology that range from: products that improve the controlled release of nutrients and others that disrupt the soil reactions that enhance mobility of nitrogen; to imaging software that looks at release of nutrients from granules and rapid methods to measure fertiliser effectiveness and runoff risks.
Under the heading of P evaluation we have a more accurate method of measurement in the form of isotope labelling of a fertiliser and measurement of recovery of the isotope by the crop.
Work on soil factors has presented more information about the effects of soil pH. Extremes of pH can markedly limit plant growth (e.g. in low pH soils aluminium and manganese toxicity can restrict root growth and in high pH soils micronutrient deficiencies can limit crop growth). In addition soil pH affects P chemistry in soils through its effect on P adsorption and through interactions that affect precipitation of P into solid forms in soil.
Research and field work, especially alongside graingrowers, is providing a better understanding of the influences of soil type. For example both the amount and type of clay in soil strongly influence P adsorption. Soil water status is important too, as most P taken up by plants arrives at the root surface by diffusion, meaning diffusion is limited in dry soils as there are fewer water-filled pores. Hence, a great deal of importance can be placed on management practices to maximise sub soil moisture.
Management can also be guided by research that confirms the value of slow-release fertilisers on certain soils and accurate placement of fertilisers (such as band placement of soluble P but broadcasting of sparingly soluble fertilisers like rock phosphates as this promotes dissolution in the soil).
Professor McLaughlin says these are just a few illustrations from a field where research in constantly expanding knowledge and developing new ways to test fertiliser behavior and effectiveness.
Getting advice on research data that is considered alongside knowledge of such factors as soil type and the local environment, can therefore be extremely helpful in improving performance.
Article written by Anthony Clancy
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