A review of the economic impact of high levels of variance in fertiliser spreading systems


  • M.C.E. Grafton
  • I.J. Yule
  • M.J. Manning




Recent technological improvements in Geographical Information Systems (GIS) have made it possible to measure the accuracy of fertiliser spreading in the field. This demonstrates that the field coefficient of variation, "field CV", of actual spread patterns on farms is significantly higher than appreciated by most end users and service providers. Levels of field CV greater than 40% for spreading N fertiliser produces a 20% yield reduction, which in terms of urea on dairy pasture is potentially around $170 million nationally, and is economically significant. Manufacturers of fertiliser spreading equipment and ground-spread applicators have introduced improved delivery technologies which reduce field CV. Mostly these improvements relate to GPS use to assist drivers, automated maintenance of bout width, control of product flow and provision of automatic start-stop control. These improvements have the potential to reduce CV to 20% and reduce economic loss to 3%. Similarly, combinations of GIS methods and differential global positioning systems (DGPS) will assist pilots to reduce field CV from 70% to 40%. Keywords: Geographic Information Systems, coefficient of variation, fertiliser spreading accuracy, real time kinematic, spread pattern.