Comparative Study of Cropping Pattern and Land Suitability of Major Horticultural and Field Crops in the Urmia Lake Basin

IntroductionOver the last two decades, Urmia Lake, the second largest hypersaline lake by area in the world, has been largely desiccated and its water volume and surface area have declined by 80%. Generally, this process is attributed to a combination of factors including climate change, water overuse for agriculture within the lake’s watershed, and mismanagement of water resources. One of the widely suggested solutions in restoration program of Urmia lake for sustainable use of land and water resources is the modification of cropping pattern within the lake’s watershed. Land suitability analysis helps planners and policy makers in the agriculture sector in deciding on the presence or absence of a specific plant in the optimal cropping pattern. The present study analyzed the cropping pattern and evaluated land suitability for major field and horticultural crops in the Urmia lake basin.Material and MethodsAll required data were obtained from the Ministry of Agriculture - Jihad. Weighted goal programming (WGP) model was applied to optimization of cropping pattern with considering three goals including maximizing net return (NR), maximizing economic water productivity (EWP) and minimizing water consumption (WC). GAMS software were used to solve the optimization model. Land suitability evaluation was done using Parametric Method for 22 field crops including wheat, barley, grain maize, bean, soybean, sunflower, canola, safflower, alfalfa, forage sorghum, potato, carrot, cotton, sugar beet, garlic, tobacco, tomato, onion, watermelon, saffron and cucumber and 12 horticultural crops including almond, apricot, peach, nectarine, sour cherry, sweet cherry, plum, apple, pear, grape, walnut and pistachio.      Results and DiscussionThe results revealed that during the past 10 years (from 3-years average of 2004-2006 to 2014-2016), cultivated area of irrigated field crops in the study area had declined in contrast to increasing trend of cultivated area for irrigated horticultural crops. Comparison of field crops for this period shows that area of wheat (from 151000 to 110000 ha), alfalfa (from 97000 to 82000 ha), sainfoin (from 15000 to 5000 ha) and onion (from 9800 to 4800 ha) had reduced while the corn silage (from 1354 to 5000 ha) and tomato (from 7382 to 8781 ha) cultivated area had increased in that period. Comparatively, the area of apple (from 62000 to 69000 ha), apricot (from 5800 to 7300 ha), plum (from 840 to 3000 ha) and peach (from 3523 to 5667 ha) had increased between two-time interval (from 3-years average of 2004-2006 to 2014-2016) in contrast to decrement of grape (from 38000 to 34000 ha) cultivated area. Results of land suitability evaluation showed that among the studied field crops, the highest suitable order area (including S1, S2 and S3 classes) were related to wheat and barley by more than 375000 ha followed by canola and alfalfa with more than 350000 ha, sunflower with more than 340000 ha, grain maize with more than 330000 ha and potato, onion and tomato with 330000 ha. Among the horticultural crops, the highest area of suitable order was related to sweet cherry, sour cherry, apricot and apple with more than 350000 ha followed by walnut with more than 340000 ha and peach by about 330000 ha. Results of cropping pattern optimization showed that total water consumption about 378 MCM (11.7%) reduced compared to current cropping pattern however, total net return and economic water productivity increased about 27.1% and 43.9%, respectively. Crops characterized with relatively higher water requirements and lower economic benefits (viz. apricot, cotton, plum, safflower, and etc.) eliminated from cropping pattern. By contrast, area under crops such as saffron, pistachio, sorghum, sweet cherry, garlic and cucumber crops recommended to optimal cropping pattern mainly because of relatively lower water consumption and higher economic benefits. ConclusionIn the present study, geographical distribution of suitable areas and main limiting factors for cultivation of each crop was determined. Generally, in the optimal cropping patterns, total water consumption decreased against an increase in net return and economic water productivity.