Investigation of sustainability of rain-fed agriculture through soil moisture modeling in the Pandamatenga Plains of Botswana

The agricultural economic sector of Botswana is limited mainly to range resources-based livestock and pockets of arable farming based on rainfall and limited irrigated agriculture at several places. In this study agricultural sustainability of rain-fed agriculture is investigated in Botswana by considering the Pandamatenga plains as a case study. Daily soil moisture regimes with respect to crop growth cycle were modelled using a water balance model based on 42 years of daily hydroclimatic inputs and corresponding simulated components of soil moisture, evaporation, surface runoff, and deep percolation. Using a sustainability criterion on crop water requirement and soil moisture availability during the cropping periods, it was found that rain-fed agriculture of maize, sunflower, and sorghum crops is sustainable. The relative sensitivity to drought of these crops was also found to conform to the Agromisa recommendations. In the pursuit to explore more IWRM opportunities, through the simulation of the corresponding direct runoff, we have also explored that more water harvesting opportunities exist in order to manage rainfall excesses effectively.