Farming systems modelling

Simulating conservation agriculture practices for crops in the Pacific Islands helps us to understand the effect of future climates and different management on crop growth.

Harvested sugarcane being transported in Fiji. Credit: Shutterstock.

Why use farming systems modelling

Farming systems models track how different crops, soil types, crop management practices, and weather interact. The model reveals changes in crop growth and yield, as well as things that are more difficult to measure like how water and nitrogen is used, stored or lost from cropping systems. These models can complement and expand upon field experiments by simulating the experiments for longer periods of time, with soils having different properties, using variations on the field management, and in other climates including future climates.

What we found

Our sugarcane study estimated that the average difference between potential rainfed yield and actual average yield (the yield ‘gap’) in sugarcane production systems in Fiji is 55 ​t/​ha, and ranked different conservation agriculture practices for their potential to close the gap. If conservation agriculture practices could be adopted (especially using additional nitrogen fertiliser inputs, liming and weed control), then yield could be increased by up to 30 t/ha.

The effect of these practices upon yield was similar under historical weather and when compared to future climate scenarios that were wetter or had only a modest increase in temperature (0.9 to 1.1 °C). However, when climate scenarios were much warmer (by 1.6 °C) and also drier, the greatest yield benefit was from adopting the conservation agriculture practices of liming, weed control and retaining crop residues.

An employee of the Koronivia Research Station with a dalo plant in a plant nursery, Fiji. Credit: Tom Vierus.

Who can benefit

Our findings are important for local policy makers because they identify which conservation agriculture practices provide greatest yield benefit and so could be prioritised for uptake in the Fiji sugarcane industry. These results can assist policy makers to identify steps to increase the productivity of the sugar industry in current climates but also in response to likely future climate scenarios.

Farmers using conservation agriculture practices could also benefit through increased farming system resilience and increased yield, which can provide additional income.

Our approach

We use the Agricultural Production Systems sIMulator (APSIM) cropping systems model to simulate conservation agriculture practices for crops in the Pacific, under historical weather and in response to future climate scenarios. For sugarcane, we simulated how best management practice from other countries would impact sugarcane yield in Fiji. In future work, we will investigate how intercropping and planting densities affect taro yields, and how corn yield changes in response to other crops in rotation.