On-farm sugarcane yield and yield components as influenced by number of harvests

Sugarcane is the most important sugar crop worldwide, with Brazil accounting for 38% of global production. Recent slowdown in sugarcane annual yield gains in Brazil has been attributed to longer replanting time and associated higher number of ratoon harvests. However, little is known about changes in on-farm sugarcane yield and its components as influenced by number of harvests. In this study, we used a large database collected from commercial sugarcane fields (‘blocks’) to assess the influence of number of harvests on variation in sugar yield and its components: stalk fresh yield (SFY) and sucrose concentration (POL%). Blocks were first clustered based on similarity of climate and soil (hereafter referred as ‘environments’). Influence of number of harvests on sugar yield, SFY, and POL% was evaluated across environments using analysis of variance and quantile and least square regressions. On-farm SFY versus number of harvests trends were compared against existing data collected from well-managed experiments. Variation in sucrose yield across block-years was mostly explained by changes in SFY and, in much lesser degree, by POL%. There was a decline in SFY with number of harvests in all cases; however, rate and magnitude of decline was different across climate-soil domains, with faster yield decline in poor soils and larger yield penalty in the region with relatively short sugarcane cropping history. Still, there was large variation in on-farm yield at any environment x harvest number combination, highlighting the importance of management at explaining current yield gap. Conversely, POL% was not affected by number of harvests and varied little across environments. Analysis of data from well-managed experiments showed no detectable yield decline with increasing number of harvests, suggesting that observed on-farm yield decline is attributable to sub-optimal management in commercial blocks. Findings from this study can help inform policy and management associated with replanting decisions.