PANI - an App for Dynamic Irrigation Scheduling.

High yields of up to 8 t/ha for maize and 2-3 t/ha for wheat can be obtained in the delta region of Bangladesh, if the crops are irrigated during the dry winter months. In an effort to boost crop production, CSISA-MI has been promoting energy efficient axial flow pumps to bring surface water from the many meandering rivers to the crop fields. Farmers traditionally do not irrigate, which leads to erratic yields. CIMMYT conducted on-farm experiments during the last two winters in order to establish the irrigation requirements and to establish the scientific basis for a decision support tool for irrigation scheduling:  At the heart of the app is a soil water balance, adapted from CERES Maize. Our research showed that capillary upflow can be as high as 2-3 mm per day. We therefore adapted an upflow routine that had been developed by W. Meyer for BASINMAN (Wu et al., 2000). It calculates upflow as a function of soil type, rooting depth and distance to the water table. Crop water use is calculated based on satellite derived ground cover (fCover) estimates.

The simulation model has been integrated into a smart phone app called PANI (Program for Advanced Numerical Irrigation). PANI runs on a daily time step and uses forecasted weather data to predict irrigation needs one week in advance. We calibrated the Blainy-Criddle Equation (Chang, 1968) so that only forecasted daily maximum and minimum temperatures are required. PANI addresses the needs of the irrigation service provider as well as of the farmer. Both receive a SMS on a weekly basis, informing them as to whether a field needs to be irrigated or not. Since the water balance of PANI is based on the widely used CERES model, it can be used under most conditions, as long as weather and ground cover data are available.