Determining Appropriate Time for Rainfed Lentil Sowing and Supplementary Irrigation in Qazvin's Plain Using AquaCrop Model

In this study¡ AquaCrop model was used in order to investigate the effect of planting date and supplementary irrigation on the performance of spring lentil in the Qazvin plain. In order to achieve this goal¡ the model was first calibrated for lentil plant. To determine the optimum planting date¡ six dates in common period of time of spring lentil planting in the region with interval of 10 days as well as at eight model proposed dates based on precipitation and temperature criteria were selected. The amounts of yield were simulated for each 14 planting dates using calibrated model and four planting dates with the highest yield were determined. Then¡ for each of these planting dates¡ the yield values for the two different dates of supplementary irrigation were estimated and compared. Based on the results¡ the highest yield is related to planting at the period of mid-February to midMarch and the best time for supplementary irrigation is 55 to 65 days after planting at flowering stage. Also¡ it was concluded that with one stage of supplementary irrigation at the right time¡ an increase of about 90 percent in lentil crop yield can be achieved compared to rainfed condition with the same planting date.