Predicting the long-term productivity, economic feasibility, and sustainability of smallholder hedgerow agroforestry systems using the WaNulCAS [water nutrient and light capture in agroforestry systems] model

In this study, the long-term productivity, economic feasibility and sustainability of Eucalyptus-maize hedgerow agroforestry systems was simulated and predicted using the WaNulCAS model. The results of simulation are compared with the results of simulation of a continuous maize mono-cropping system. The model was calibrated using the experimental data and survey results in a study conducted at Claveria, Southern Philippines. Simulation showed that more than half of the total nitrogen in the two systems is tied up in the soil organic matter (SOM). Leaching and lateral flow are the main avenues of nitrogen losses in both systems. Results of modeling the water balance of the two systems showed that Eucalyptus-maize hedgerow system had higher subsurface flow and surface run-off. Maize yield was initially higher in the continuous annual cropping system (2.4 t/ha) than under the Eucalyptus-maize hedgerow system (1.8 t/ha). The benefit obtained from the maize cropping system is the grain yield while from the Eucalyptus-maize hedgerow system the benefits are maize grain yield and Eucalyptus timber. Financial analysis showed that the Eucalyptus-maize hedgerow system had higher NPV [Net Present Value] after 9 years of simulation (P304,323) compared with the continuous maize (P20,872). Results of this study show that Eucalyptus-maize hedgerow system provides significant improvements to a range of biophysical and economic measures of productivity and sustainability. WaNulCAS is a process-based model of water, nutrient and light capture in agroforestry systems (Van Noordwijk et. al., 2004). It is the most flexible model around currently available for the evaluation of different management options in agroforestry systems based on site-specific information and farmer management objectives. Simulation results that can be generated by the model included nutrient dynamics, water balances, light use, crop and tree biomass, and crop yield.