The ‘best’ legume rotation for southern cane growers

Abstract

Grain legume rotations on sugarcane farms have become well established in the Bundaberg/Isis/Maryborough cane supply districts, as a result of RDE efforts of the Sugar Yield Decline Joint Venture. However, sugarcane growers wanted information on what was the ’‘best’’ legume to grow in rotation with sugarcane. Two separate projects with funding support from both the Grains and Sugar industry with a grower/advisor steering committee implemented a field trial to evaluate the performance of different varieties of peanut, soybean and mungbean along with pigeon pea, traditional cowpea and bare fallow options. These rotation options were then assessed to determine the effect on the productivity of the subsequent sugarcane crop. A cane monoculture treatment was also maintained to provide a reference. The data from this experiment demonstrated that soybean and peanuts were valuable rotation options that boosted grower profitability and productivity of the subsequent sugarcane crop. The trial also highlighted the potential of pigeon pea as a rotation option. Red Caloona cowpea was the ‘best’ legume in terms of nitrogen contribution, but this did not translate into the best productivity of the subsequent sugarcane crop. Whilst the peanut rotation provided the ‘best’ profitability, by the end of the first ratoon, A6785 soybean rotation provided the ‘best’ cumulative cane yield. All legume rotations significantly reduced root lesion nematode populations when measured 6 months after cane establishment. The poor performance of sugarcane grown after Onyx mungbean was probably reflective of the high numbers of root knot nematodes that proliferated on that crop. A sugarcane monoculture had the lowest productivity and the lowest gross margin in the plant-cane phase. Data collected from this experiment suggests that growers would benefit from a legume decision support tool to better assist growers in making profitable farming system decisions.