Management of crop residues following green harvesting of sugarcane in north Queensland

Abstract

The recent rapid transition from burnt to green harvesting of sugarcane in north Queensland has been accompanied by a reduction in tillage, the retention of crop residues as a surface trash blanket, and a change to surface applications of fertilizer. Unreplicated field trials established to monitor the long-term effects of these new practices have indicated increased ratoon crop yields particularly on well-drained soils, a suppression of weed growth, increased soil moisture and organic matter and a reduction in soil loss from sloping areas. The main problems have been encountered in wetter areas with poorly drained clay soils where a trash blanket can accentuate problems of waterlogging by keeping soils moist for longer. In these areas it is vital that attention be paid to surface and subsurface drainage and the choice of suitable cane varieties. Trials are in progress to evaluate different methods of nitrogen fertilizer application. Preliminary results suggest large losses of applied nitrogen from surface applications of urea. It appears likely that losses can be reduced by placement of urea beneath the soil surface or by using alternative forms of nitrogen fertilizer. Green cane trash retention associated with reduced or zero tillage offers considerable cost savings for growers. It is likely to be adopted by an increasing proportion of canegrowers in north and central Queensland where winter soil temperatures are sufficiently high for ratoon growth beneath a trash blanket.