مکان‌یابی مناسب‌ترین مناطق کشت گندم دیم(مطالعه موردی: استان خراسان شمالی)

با توجه به اهمیت عوامل اقلیمی در تولید محصولات کشاورزی دیم و نیز توانایی‌های بالقوه استان خراسان شمالی، پهنه بندی اقلیمی کشت گندم دیم در این استان هدف اصلی این تحقیق قرار گرفت. برای این منظور از آمار بلندمدت 17 ایستگاه باران سنجی،اقلیم‌شناسی، سینوپتیک، 5 ایستگاه تبخیرسنجی داخل استان و 6 ایستگاه سینوپتیک در خارج از این استان جهت هم پوشانی بهتر استفاده شد. در این تحقیق با توجه به تاریخ آغاز بارش‌های پاییزی برای هر منطقه از استان تاریخ کاشتی پیشنهاد شد. سپس مراحل مختلف رشد گندم دیم بر اساس محاسبه درجه روزهای رشد (gdd) مراحل مختلف بدست آمد. در مرحله بعد، احتمال وقوع بارش سالانه 300 میلی متر و بیشتر، مقادیر بارش پاییزه، بهاره و خرداد با احتمال وقوع 75% بررسی شد. همچنین احتمال وقوع دمای مناسب جوانه زنی گندم دیم، دمای حداکثر 25 و 30 درجه سانتی گراد در مرحله گل دهی و مرحله پرشدن دانه محاسبه گردید. سپس با بهره گیری از نیازهای رویشی (شرایط اقلیمی مطلوب) گندم دیم، لایه های اطلاعاتی تهیه و کلاسه بندی شده و ارزش وزنی هر کدام از پهنه ها مشخص شد. در نهایت با تلفیق نقشه ها در محیط gis نقشه پهنه بندی اقلیمی کشت گندم دیم در استان خراسان شمالی استخراج گردید. این نقشه نشان داد که مناسبترین مناطق کشت گندم دیم در قسمتهای شمال استان می‌باشد و مناطق ضعیف در جنوب غربی و جنوب شرقی استان واقعند. همچنین این تحقیق نشان داد که با انطباق لایه های موثر در فرآیند کشت گندم دیم در محیط gis، امکان شناخت مناطق مستعد کشت برای این گیاه زراعی وجود دارد.

Locating the Most Suitable Dry Land Wheat Areas (Case Study: North Khorasan Province)

IntroductionSince, wheat is one of the most important and strategic crops in Iran, determining appropriate areas for planting dry land wheat, according to the heat, humidity and climate capabilities in different regions of Iran, can increase the yield of this crop. In this research, the climatic potential and their adaptation with the requirements of dry land wheat (autumn wheat) are determined in North Khorasan province.Materials and MethodsThe region in question is North Khorasan Province that located in North East of Iran. In this study, longterm data of 17 rain gage, climatology and synoptic stations, 5 evaporation stations inside the province and 6 synoptic stations outside of the province during 19862005 were used in order to overlap better. The exact date of various growth stages of wheat in the different parts of this province is calculated by growing degree days (GDD) according to the following equation (Behnia, 1376): Where GDD is growing degree days, Tmax and Tmin are maximum and minimum daily temperatures (Celsius degree) respectively, Tb is the base temperature (Celsius degree), a and b are the beginning and the end of date of phenological stage, respectively. The base temperature is the lowest temperature that is assumed to be no lower than the growth. The thermal units required for this crop are as follows:The total thermal units from sowing to sprout                                              180 GDDThe total thermal units from sowing to flowering period                 1300 GDDThe total thermal units from sowing to grain filling period              2100 GDDDiscussionIn this research, GIS is used for data analysis and processes. Then, by using growth requirements dry land wheat (optimum conditions), the data layers were classified and the weight of each zone was determined. Finally, by overlapping the maps in GIS, the dry land wheat climatic zoning map is prepared in North Khorasan.According to scientific references and climate conditions of study region, after determining the parameters for each of the stations and transferring them to GIS, four classes for each of the layers are defined (Table 1).In addition, for overlapping the layers according to climate conditions for planting dry land wheat and expert idea, the layers should have the same time scales, so the weight of each zone is assigned by a number from 0 to 100 (Table 2). By overlapping method (weight classes), all of the layers in table 2 are combined in GIS and finally land zoning map for dry land wheat is prepared in this province.  Table 1: Defined classes for each layerQualitative Value'Climate ParametersUnsuitableweakModerateSuitableRainfall probability 3000 mm and more (%)< 3030505070> 70Autumn rainfall amounts (mm)< 8085120120155> 155Spring rainfall amounts (mm)< 125125150150190> 190June rainfall amounts (mm)< 2020353550> 50Suitable temperatures probability for germination (%)< 5050606070> 70Temperatures probability 25 ºC and more during flowering stage> 5037502537< 25Temperatures probability 30 ºC and more during grain filling stage> 5037502537< 25Temperatures probability 9 ºC and lower during flowering stage> 3525351520< 15Temperatures probability 9 ºC and lower during grain filling stage> 3525351525< 15 Table 2: Weight of each class Annual RainfallAutumn RainfallSpring RainfallJune RainfallSprouting Stage TemperatureFlowering Stage TemperatureGrain Filling Stage TemperatureUnsuitable203025159090weak50555550657070Moderate75807065755050Suitable951009085902525ResultsAppropriate Lands: because of suitable climate conditions during the growing period of wheat, they have high yield. This area is 6263 Km2 (22% of the area province) and it is allocated in the northeast and northwest until the west of this province.SemiAppropriate Lands: they are poorer than appropriate lands. Planting dry land wheat in this area is suggested and it can increase the yield of this crop. This area is 17534 Km2 (62% of the area province).3. Weak Lands: these lands have low climate potential for planting dry land wheat. These regions are in the southeast and southwest of the province and they have lower annual rainfall and limited temperature in flowering and grain filling stages. This area is 4884 Km2 (16% of the area province) that are included Jajarm and Mangoli stations.