Growth of different plant species in fumigated/sterilised and untreated sugarcane soils with varying cropping histories

Fumigation or soil sterilisation was used to study the effects of poor root syndrome or yield decline in sugarcane. Yield decline is associated with long-term monoculture and experiments were initiated to study the effect of crop rotation on the yield decline syndrome. Some initial pot experiments were conducted to measure the effect of fumigating/sterilising soil, known to produce yield decline in sugarcane, on the growth of a number of potential rotation species. Other grasses such as sorghum and maize responded to fumigation/sterilisation, and are consequently unlikely to maximise the potential benefits of crop rotation. Conversely, peanuts, soybean, sunflower and a range of dicotyledonous vegetable crops did not respond to fumigation and offer better potential as rotation crops. However, the suitability of sunflower was moderated by relatively poor growth on sterilised old sugarcane land due apparently to aluminium toxicity. It is concluded that dicotyledonous species should be selected as breaks for sugarcane and cognisance taken of their nutritional requirements and that available in the particular soil. The value of break species will be dependent on their health and growth.