امكان سنجي كشت چاودم (Tritico secale wittmack. X) در اراضي كشاورزي شهرستان گرگان با استفاده از تحليل هاي مكاني سامانه اطلاعات جغرافيايي (GIS)

Feasibility of Triticale (Tritico secale wittmack. X) Cropping in Agricultural Lands of Gorgan County by Spatial Analysis Tools

شناسايي استعداد و توان سرزمين براي كاربري هاي مختلف كشاورزي به منظور حفظ منابع محيطي و توليد پايدار محصولات در راستاي توسعه پايدار و همه جانبه در مناطق مختلف، ضروري به نظر مي رسد. به منظور امكان سنجي كشت گياه تريتيكاله (چاودم) (Tritico secale wittmack. X) در اراضي كشاورزي شهرستان گرگان، از تحليل هاي مكاني سامانه اطلاعات جغرافيايي (GIS) و فرآيند تحليل سلسله مراتبي (AHP) استفاده شد. متغيرهاي مختلف محيطي از جمله بارش (سالانه، بهاره، پاييزه و دوره رشد) و دما (كمينه، بيشينه و متوسط در دوره هاي سالانه و طول فصل رشد)، توپوگرافي (جهت شيب، شيب و ارتفاع از سطح دريا) و عوامل خاكي (ماده آلي، حاصل خيزي، اسيديته، شوري و بافت) با استفاده از روش هاي زمين آماري و كلاسيك مورد ارزيابي قرار گرفته و مقادير و پراكنش آن ها در سطح اراضي شهرستان گرگان تخمين و برآورد شد. سپس اين لايه هاي رقومي بر حسب جدول نيازهاي بوم شناختي تريتيكاله طبقه بندي شد. پس از اختصاص وزن به هر لايه، تلفيق و هم پوشاني وزني آن ها در محيط ArcGIS انجام گرفت و لايه نهايي در چهار پهنه بسيار مستعد، مستعد، نيمه مستعد و غيرمستعد جهت كشت تريتيكاله طبقه بندي شد. نتايج نشان داد كه 28758/959 هكتار (44/92 درصد) از اراضي كشاورزي شهرستان در طبقه بسيار مستعد (S1) قرار مي گيرند. از خصوصيات اين پهنه مي توان به حاصل خيزي خوب، ماده آلي بالاتر از دو درصد، ارتفاع كم تر از 1500 متر از سطح دريا، جهت هاي شيب مطلوب، شيب هاي 4-0 درصد، مقدار و توزيع بهينه بارش و دما در اين منطقه نام برد. پهنه هاي مستعد (S2)، نيمه مستعد (S3) و غير مستعد (NS) به ترتيب 17219/405، 11833/255 و 6217/401 هكتار برابر26/89، 18/48 و 9/71 درصد از اراضي كشاورزي شهرستان را به خود اختصاص دادند. جهت هاي شيب نامطلوب، ارتفاع بالاتر از 1000 سطح دريا، كاهش كيفيت حاصل خيزي خاك، افزايش درصد شيب به سمت مناطق مرتفع جنوبي و بارش اندك به خصوص بارش بهاره در بخش هاي شمالي، عوامل محدود كننده كشت در اين پهنه ها بودند.

Introduction It is essential to allocate crop to the most suitable land areas precisely for the best production since arable land has been decreased. Selecting the most appropriate algorithm for land suitability assessment is important for current and future land use planning. Several approaches have been attempted to conduct land suitability assessment. Geographic Information System (GIS) technology is a useful tool for integration of bio-climate, terrain and soil-resource-inventory information. The integration of Multi-Criteria Analysis (MCA) methods such as Analytical Hierarchy Process (AHP) by GIS is a trend in land suitability analysis. This combination could be useful in solving conflictive situations for individual or groups interested in spatial context and it is a powerful approach for land suitability assessments (Elsheikh et al., 2013). The present study was therefore carried out with the objective land suitability analysis for feasibility of triticale cropping in agricultural lands of Gorgan county by spatial analysis of GIS and evaluation of environmental variables. Material and Methods One of the most important areas for crop production in Golestan province located in north of Iran, is the Gorgan region. This area is located between latitude 54° 12.9' N and 54° 44.9' N and longitude 36° 30.6' E and 36° 58.8' E.Almost every farm in Gorgan region are rainfed. In order to spatial feasibility of triticale cropping in Gorgan county, agroecological requirements of triticale was identified and classified from scientific resources. Some environmental factors including, climatic variables such as precipitation and temperature in scale of annual, monthly and seasonal, topographic variables such as elevation, slope aspects and slops percent, and some soil characteristics as texture, EC, pH, fertility, K, P and organic matter were evaluated using geostatistics and classic methods and then thematic layers were produced in ArcGIS media. In multi-criteria assessment process, one of the most important steps is to determine each criteria weight. Generally, AHP is suitable to determine the weights of assessment factors. In this respect, the first step is to construct an AHP model consisting objectives, criteria, sub-criteria, and alternatives. Then these digital layers were classified based on ecological requirements table of triticale and they were overlaid and interpolated in GIS media and final layer were classified to four classes of high suitable, suitable, less suitable and non-suitable. The suitability analysis was based on matching between land qualities/characteristics and crop requirements. It was accomplished by weighted overlay technique (WOT) in GIS. Results and Discussion The results showed that 28.8 thousand ha (44.92%) of agricultural lands were located in the high suitable class (S1). This zone was observed occasionally in north and northwest parts of studied region. This zone had the high fertility, high organic matter percent (2<), favorable slope aspects, elevation lower than1500 meters above sea level, suitable slops (0-4%), enough amount and distribution of precipitation and temperature variables. Also, about 17.2 thousand ha (26.89%), 11.8 thousand ha (18.48%) and 6.2 thousand ha (9.71%) of areas were classified in the suitable (S2), less suitable (S3) and non-suitable (NS) zones respectively. It seems that omitting the restrictions such as soil fertility, suitability level can enhance in NS class. Proper land management practices, crop rotation performance, specific irrigation methods and using resistant genotypes would help to increase crop yield in this area. Conclusion In this study, the limiting factors were identified as unfavorable aspects, high elevation, poor soil fertility, high slope percent in the direction of south and low spring precipitation in northern region of Gorgan. In general, this research was a biophysical evaluation of resources that provided information at a regional level. Therefore, its result is useful for decision markers to determine the quality of cropland for triticale cropping and it is proposed as a decision and planning support.