USE OF BIOCIDES TO DETERMINE THE IMPACT OF DETRIMENTAL FUNGI AND NEMATODES ON ESTABLISHMENT AND EARLY GROWTH OF SUGARCANE FOLLOWING ROTATION BREAKS

Three different biocide treatments: fumigation, fungicide and nematicide were used to determine what proportion of the early growth response following three different rotation breaks (pasture, crop and bare fallow) was associated with a reduction in populations of detrimental fungi and nematodes in the soil. Cane plants were examined 54 days after planting into soil that had been under the different breaks for 54 months. Each of the breaks had a positive effect on % bud germination and sett root growth, parameters associated with plant establishment. The biocide treatments suggested that detrimental fungi in continual sugarcane (plough-out/re-plant or PO/RP), and following the pasture break, but not following the crop or bare fallow breaks, affected bud germination. Fumigation, fungicide and fungicide + nematicide, increased plant growth parameters associated with early growth (shoot root growth, primary shoot growth, number of secondary shoots) across all three breaks and PO/RP. These responses were attributed to the control of detrimental fungi and nematodes and to possible biocide effects on the nutrient status of the soil. Sett root growth was positively correlated with plant parameters associated with early plant growth and negatively correlated with populations of rhizosphere fungi. The results confirm that a major effect of the rotation breaks is to reduce the impact of detrimental fungi and nematodes, which affect the establishment of the cane crop.