Regional classification for dryland agriculture in southern Iran

The average annual and the fall season ratios of rainfall (P) to reference crop evapotranspiration (ET0) were used as agroclimatological indices, to develop suitability atlas of dryland agriculture for southern Iran (Fars province). The results were plotted as ISO-(P/ET0) lines. The fall season atlas can be used to study the P/ET0status of seed germination stage. The annual atlas, information on regional yields and UNESCO recommendations are used for land selection. Areas with ISO-(P/ET0) lines of at least 0•58 and of 0•63 should have a yield 1000 kg ha−1for wheat and barley, respectively. Areas with ISO-(P/ET0) lines of 0•2–0•6 can have a yield of less than 1000 kg ha−1. Areas with ISO-(P/ET0) lines of less than 0•2 are not suitable for dryland agriculture. A probabilistic atlas (90% rainfall and 10% ET0) was developed as an extreme condition for land selection. Areas of the annual probabilistic atlas with ISO-(P/ET0) lines of at least 0•2 are the most suitable for dryland agriculture. The probabilistic fall season atlas shows the effect of fall season rainfall