SALTMED model and its application on field crops, different water and field management and under current and future climate change

Abstract

Models can be very useful tools in agriculture water management. They could help in irrigation scheduling and crop water requirement estimation and to predict yields and soil salinization. SALTMED model is a generic model that can be used for a variety of irrigation systems, soil types, crops and trees, water application strategies and different water qualities. The early version was successfully tested against field experimental data. The current version, SALTMED 2015, includes additional sub-models, crop growth according to heat units/degree days, crop rotations, nitrogen dynamics, soil temperature, dry matter and yield, subsurface irrigation, deficit irrigation including the Partial Root Drying, PRD, drainage flow to tile or open drains systems, presence of shallow groundwater, evapotranspiration (ET) using Penman-Monteith equation, with different options to obtain the canopy conductance. The current version allows up to 20 fields or treatments to run simultaneously. The model was applied on field experiments in Agadir in the Souss-Massa river basin. These experiments included several crops, such as quinoa, sweetcorn and chickpea; different water qualities, such as saline water, treated waste water and fresh water; different irrigation strategies, such as deficit irrigation (applying less water than the total crop water requirement) and applied water stress during certain growth stages. The model was successful in predicting the soil moisture, yield and dry matter for all the crops under different water qualities and all the water application strategies. The results showed that quinoa is the most drought and salt tolerant cereal crop. The results also showed the possibility of significant freshwater saving when using treated waste water and applying moderate water deficit/ stress especially during the non-sensitive growth stages. The SALTMED model, for three growing seasons, supplied "baseline data" for sweetcorn. The SALTMED model was run in forecasting mode to obtain future projections of crop ET and crop productivity under changing climate. The results suggested that, with increasing temperature, the crop ET is expected to increase by 15% while crop water requirement is expected to decrease by 13%, due to the shortening growth season of corn. The results also show that the crop harvest is expected to be 20 days earlier. Crop productivity in terms of dry matter and yield could exhibit a reduction of 2.5% towards the end of the twenty-first century. This study was applied on corn but it is likely that a similar trend could be found for other crops grown in the Souss region. These results indicate that climate change could have a negative impact on water availability in this water poor region and subsequently may pose a serious threat to the region’s food security.