A Modeling Approach to Explore Water Management Strategies for Late-Sown Maize and Double-Cropped Wheat–Maize in the Rainfed Pampas Region of Argentina

Abstract

Most of Argentine maize (Zea mays L.) production takes place under rainfed farming in the Pampas region, where water availability is the main limiting resource. Most crops are still sown early in spring to have the critical period of silking before the frequent mid-summer water deficit. Early sowing dates (September) have been also linked to the need for escaping the increased incidence of insect pests associated with late sowings, a restriction that has been drastically reduced with the introduction of Bt hybrids. Therefore, very late sowing dates (December) became an actual alternative that must be evaluated. We estimated the combined effect of late sowings, variable levels of plant available soil water (PASW) at sowing in single- and double-cropped crops, and variable levels of soil N supply on the interannual variation of maize yield in four sites of the region. For this purpose we used 41 yr of daily, measured weather data and the Crop Environment Resource Synthesis-Maize (CERES-Maize) simulation model. Rainfed yield was very stable across December sowings (³7.5 Mg ha-1 ) for latitudes £36° S, provided PASW (1.8 m) at sowing was 100% and initial N availability reached approximately 130 kg ha-1 N. This strategy had almost no yield penalty as compared with potential yield. The response rate to mentioned N availability turned negative for PASW at sowing £35%. Because of the apparent yield stability across December sowings, farmers should be recommended to survey PASW rather than tie late sowing of maize to scattered rainfall events.