However the best way to find out how much phosphorous is in your soil is to do a soil test. The most important factor affecting growers' fertiliser strategies for the coming season is cash flow. If cash flow is an issue, Dr Bowden said growers should consider the dollar, yield and quality consequences of applying less fertiliser or cropping a smaller area than usual. Only where you have been skating close to the deficiency end of the fertility spectrum, do you have to be careful not to under fertiliser. Under fertilising will lose you more yield and dollars in a good season than a bad season, because water is no longer the main limiting factor and you are more likely to run into a nutrient constraint.
Profits tend to fall more markedly from under-fertilising than they do from over fertilising.
Growers can use a consultant or fertiliser company representative to assess their cropping program's dollar to yield sensitivities. Dr Bowden said it often paid to split nitrogen fertiliser inputs, between pre and post seeding, to provide greater flexibility if the yield potential looked high. However, it is important to remember that adequate nitrogen is needed within six to eight weeks of sowing, to set up the tillers, which govern the yield potential. Playing the split nitrogen game is not simple, so farmers should seek advice on the best option for their individual situation. Click on the image for a larger view Caption Electronic jpg photographs available on request.