Dr Brown says successful nitrogen management is the application of just enough nitrogen to ensure crop yield is not limited. "Too little nitrogen will result in lost yield and too much has the risk of nitrogen leaching which is a waste of money and an environmental hazard," he says. Key to getting it right is finding out the level of nitrogen in the soil in which the crop is to be planted. Each season the nitrogen soil levels vary from paddock-to-paddock and it is recommended growers measure levels in each paddock at the start of each season. This involves testing soil from 60cm below the surface.
Testing nitrogen levels is not new, although in potato crops, until recently it was more common to test nitrate levels in the plants themselves. However, the information gleaned is not nearly as useful as that attained from the soil. Accurate soil tests give a start point for calculations of nitrogen movement in and out of the crop during the growing season. Models have been developed for day-to-day changes in nitrogen uptake by a crop and the leaching that may take place, says Dr Brown. Factors that influence uptake and leaching are specific to the paddock and season so nitrogen calculations should be done for individual crops, he says.
Crop management tools like the web-based potato calculator are flexible to take the crop-specific information in any given season and calculate crop needs for defined yields. The demand for accurate nutrient applications coupled with the advent of tools like the potato calculator means the days of fertilising by recipe, or making decisions on inaccurate tests, are nearly over says Dr Brown. Growers already using the potato calculator are saving money on fertilisers and don't risk nitrogen leaching into waterways.
For more information contact:
Dr Hamish Brown
Tel 03 325 9394
Mob 027 226 1166