Modelling the long-term productivity and soil fertility of maize/millet cropping systems in the mid-hills of Nepal

Finding ways of maintaining or increasing crop yields without degrading soil fertility is an important goal in sustaining livelihoods in many parts of the world. In the mid-hills of Nepal, the problem is of particular importance due to the fragility of mountain ecosystems. Previously reported field experiments have investigated the influence of different combinations of inorganic fertilisers and farmyard manure (FYM) on crop yields in maize/millet cropping systems at two sites in this region, Pakhribas and Dordor Gaun, but due to the short-time period involved (three years), long-term trends in crop yields could not be determined, neither could changes in soil carbon and nitrogen levels be measured. In this paper, we describe the use of the PALM simulation model to address these questions, and its parameterisation and validation based on data from the field experiments. Using weather data generated for 100 years at each site, the model was then used to investigate the effect of different nutrient management treatments on long-term trends in crop yields and soil carbon and nitrogen dynamics.