Fumigation of land that had been under the rotation breaks gave plant growth responses that were in addition to that achieved by the breaks alone. Rotation breaks (alternate crops, sown pasture, bare fallow) that were in place for 54 months, increased sugarcane establishment and increased sugarcane yields to levels similar to that obtained following fumigation of land under sugarcane monoculture. In field experiments, fungicide and nematicide (mancozeb + aldicarb), when applied together to land under sugarcane monoculture, was as effective as fumigation in improving early sugarcane growth and increasing sugarcane yields.
Exposure of the developing sett root system for 14 days to mono-cultured sugarcane soil was sufficient to significantly retard subsequent plant growth. It also reduced populations of culturable fungi in the rhizosphere of the sett roots and reduced colonization of the sett and shoot roots by lesion nematode (Pratylenchus zeae). Fumigation of a soil that had been under sugarcane monoculture with minimal breaks for more than 30 years markedly improved the health and growth of the sugarcane sett and shoot root systems, increased the growth of the primary shoot and stimulated more and larger secondary shoots. Glasshouse and field experiments were conducted to determine the effects of biocides and rotation breaks on deleterious soil organisms associated with the poor early growth and subsequent yield decline of sugarcane grown in continuous monoculture.