A comparative study of conventional and controlled traffic in irrigated cotton: II. Economic and physiological analysis

•Irrigated 1.5 m outperformed 1.0 m row spacing in terms of water use efficiency and gross margin for cotton.•1.5 m system cotton produced superior fibre quality as compared to 1.0 m system.•Controlled traffic conversion cost was completely offset in one season of increased yield potential.

Expanding the row spacing of cotton can improve water efficiency by enlarging the micro-catchment for water and reducing the number of plants per hectare, as well as facilitating controlled traffic conversion of heavy harvesting machinery. This work assesses the effects of 1.5 m row spacing on cotton yield, fibre quality and water use efficiency (WUE) in comparison to the traditional 1.0 m row spacing cotton system. A replicated, side-by-side, commercial scale experiment was instigated with a 1.5 m row spacing controlled traffic system compared against a 1.0 m row spacing standard cotton system. Cotton fibre characteristics, fruiting position and yield were measured along with system water use, in the context of machine traffic. A detailed analysis of soil resource impact is provided in the companion paper. The 1.5 m row spacing system was shown to perform better than the 1.0 m row spacing system in terms of WUE and machine traffic impact over the two cotton seasons and single wheat season. In the 1.5 m system cotton WUE was greater with higher gross margin, even though less cotton yield was harvested. The 1.5 m row spacing cotton matured more slowly, led to stronger and longer cotton fibres with overall better fibre quality. Increased gross margin potential of the 1.5 m system was shown to entirely offset the cost of controlled traffic conversion within 1 season for a field where heavy machinery had not been used extensively.