Loss of nitrogen from urea and ammonium sulphate applied to sugar cane crop residues

Cane farmers in north Queensland are rapidly converting to a system of green cane harvesting and retention of crop residues as their preferred method of crop management. Trash blanketing has obviated the need for cultivation of ratoons and growers have changed from subsurface to surface applications of fertilizers. Urea has proved to be the cheapest and most convenient form of nitrogen fertilizer available and is now the major form of nitrogen applied to the north Queensland sugar cane crop. Nowhere has the change in crop management practices been more rapid than in the Herbert River district around Ingham, where in 1988 over 85% of the crop was harvested green compared with only 9% in 1984. The widespread use of urea is illustrated by the fact that approximately 85% of the nitrogen fertilizer applied to the 1988 crop was in the form of urea or urea blends.