The impact of combinations of trash management and tillage on grain legume and subsequent sugarcane productivity in the Bundaberg/Childers district

Abstract

Producers in the Bundaberg/Childers and Maryborough districts are implementing various combinations of legume rotations, trash retention, reduced tillage and controlled traffic in new and evolving farming systems. There are challenges in successfully integrating these components. Two trial sites were established to measure the impact of different trash management (maintaining full GCTB, removing some trash via baling and full removal through burning) and tillage (conventional, strip-till and direct drill) techniques on grain legume production, with one site focussed on grain soybean productivity and the other on peanuts. The different tillage systems were reinstituted after harvest of the legume crop during the establishment of the plant cane crop. Impacts of tillage and additional nitrogen application on plant cane productivity were measured. The soybean trial site was established on a farm growing cane in 1.57 m row configuration, and neither trash management nor tillage affected soybean productivity. However there was a trend for lower plant cane productivity with reduced tillage and there was a 13% yield improvement through the application of fertiliser N in a very wet season. In contrast, the peanut trial site was established on a farm growing cane in 1.8 m row spacings. Sugarcane trash management didn’t impact on peanut productivity, although yields were lower in reduced tillage treatments. In the following plant cane crop there was no impact of tillage on sugarcane productivity, and there was only a 5% response to N fertiliser application on cane productivity, but not sugar productivity. Data demonstrate that even though soybean productivity was unaffected, unamended soil compaction from the previous cane cycle can limit productivity of both fallow peanut crops and the next cane crop cycle. Further research may be able to improve productivity and harvest efficiency of peanuts in reduced tillage systems. However, it seems clear that appropriate row configurations to control traffic and minimise compaction are imperative to allow successful sugarcane production in reduced tillage farming systems.