EFFECT OF FUMIGATION, DENSITY AND ROW SPACING ON THE GROWTH AND YIELD OF SUGARCANE IN TWO DIVERSE ENVIRONMENTS

Recent research in the Australian sugar industry has indicated that substantial yield increases can be achieved through improving soil health (alleviating physical, chemical and biological constraints in the farming system) and by changing plant population (increasing plant densities and narrowing row spacing). The research reported here was conducted to investigate the potential for combining these effects to further lift potential productivity. Experiments were established at Mackay and Bundaberg. In each experiment, fumigation, planting density and row spacing were interacted. Varieties were Q117 in Mackay and Q155 and Q124 in Bundaberg. The experiments were only grown for the plant crop. Fumigation significantly increased the yield at Mackay and in Q155 at Bundaberg. Despite also promoting early growth in Q124 at Bundaberg, fumigation promoted earlier crop lodging and stalk death, which resulted in no response in final yield. There was no effect of row spacing in either experiment, but there were significant or near significant density effects. At Mackay, there was a trend for increased yields with higher density in the unfumigated treatment but not after fumigation. At Bundaberg, yields were significantly decreased with higher density due to increased lodging and stalk death. The results from the Mackay experiment, and results from pre-lodging measurements at Bundaberg, suggested a strong interaction between soil health and the response of sugarcane to increased planting density and narrower row spacing. Removal of soil constraints by fumigation allowed the expression of a significant ability to compensate for low plant populations by vigorous tillering and secondary shoot establishment. The range of plant populations and environments over which such compensation can occur requires further investigation.