Priorities for narrowing the yield gap and increasing farming systems resilience in the Fiji sugar industry

Abstract

Sugarcane (Saccharum officinarum L.) is the single most important agricultural industry in Fiji and occupies half of the nation's cropped area while supporting 25% of the labour force. However, the industry is facing comprehensive challenges across the supply chain, underlain by declining productivity and changing climate. The purposes of this study were to: (1) use model simulation to determine the potential of conservation agriculture (CA) practices to narrow yield gaps in sugarcane production systems under historical and projected climates in a case study; (2) identify and rank candidate practices that would contribute to narrowing such yield gaps; and (3) identify the limitations of the modelling approach and make recommendations for improving it. We simulated nine scenarios of CA practices with potential to reduce the estimated yield gap (55 ​Mg ​ha^-1) by increasing nitrogen (N) fertiliser rates (30 ​Mg ​ha⁻¹), liming (25 ​Mg ​ha⁻¹), improved weed control (5–9 ​Mg ​ha⁻¹), replacing uncropped fallow with legume crops (2–3 ​Mg ​ha⁻¹), crop cycle duration (0 ​Mg ​ha⁻¹), and retaining crop residues (−2 ​Mg ​ha⁻¹). The yield benefit of CA practices was similar under projected climates that were warmer and wetter or drier, or hotter and wetter. For a projected climate that was hotter and drier, the greatest yield benefit was obtained from liming, weed control, and retaining crop residues. The study was limited by the availability of daily weather data, and it would be complemented by additional studies incorporating more local crops, evaluation of barriers to mechanisation needed to implement new practices, and economic assessment of scenarios.