مطالعه بلندمدت تغييرات فشرده سازي و تأثير آن بر ثبات توليد محصولات كشاورزي در ايران (دوره 50 ساله 1341 تا 1390)

Long Term Evaluation of Intensification in Iran Agriculture and Its Impact on Production Stability (50 years from 1962 to 2011)

به‌منظور بررسي وضعيت فشرده‌سازي و روند تغييرات آن در كشاورزي ايران 63 متغير در قالب شش گروه كاربري اراضي، توليد، كارآيي مصرف، ورودي ها (نهاده، ماشين‌آلات)، انرژي و جمعيت براي دوره 50 ساله 1341 تا 1390 مورد بررسي قرار گرفت. تغييرات كاربري اراضي، افزايش مصرف نهادهها و افزايش جمعيت به‌عنوان عوامل مؤثر در افزايش فشرده‌سازي تعيين شدند. براي تعيين ثبات سطح زير كشت، توليد و عملكرد، ضريب تغييرات اين متغيرها در پنج دهه براي محصولات مهم زراعي و باغي به‌طور مجزا محاسبه شد و روند تغييرات اين ضرايب به‌عنوان شاخصي براي ثبات تعيين شد. براي تعيين ميزان حساسيت به تغييرات محيطي نسبت عملكرد هر محصول در هر سال به ميانگين عملكرد محصول در بازه هاي 10 ساله به‌طور مجزا براي هر گياه و براي همه محصولات به‌عنوان ظرفيت عملكرد محاسبه شد، شيب خط رگرسيون بين ظرفيت عملكرد هر محصول با ميانگين ظرفيت عملكرد همه محصولات بيانگر ميزان حساسيت آن محصول به تغييرات محيطي است. نتايج نشان داد كه در طي مدت 50 سال سطح زير كشت از حدود 6/6 به 13/3 ميليون هكتار و توليد محصولات كشاورزي از 11 به 94 ميليون تن افزايش يافته و در همين حال ضريب تغييرات سطح زير كشت و توليد كاسته شد همبستگي منفي و معني‌دار 0/47- و 0/89- به‌ترتيب بين ضرايب تغييرات سطح زير كشت و توليد در دهه‌هاي مختلف نشان‌دهنده افزايش ثبات توليد بود. شاخص حساسيت به تغييرات محيطي مربوط به ذرت (Zea mays L.)، گندم (.Triticum aestivum L) و جو (.Hordeum vulgare L) به‌ترتيب برابر با 1/59، 0/99 و 0/93 بود كه نشان‌دهنده پايين‌تر بودن ثبات عملكرد در محصولات اصلي است. تجزيه به مؤلفه هاي اصلي 63 متغير، دو الگوي اصلي در تغييرات گروهها را نشان داد. دسته اول با توصيف 51 درصد نشاندهنده افزايش فشرده سازي در قالب تغيير كاربري اراضي زراعي، تغييرات توليد و عملكرد و افزايش مصرف نهاده ها در طي 50 سال گذشته بود و مؤلفه دوم با توصيف 20 درصد از تغييرات بيانگر تغييرات مهمي در كشاورزي ايران شامل تغيير كارآيي مصرف نهاده و رشد جمعيت بود. در طي 50 سال گذشته شاخص‌هاي مرتبط با فشرده‌سازي نظير سطح زير كشت با دو برابر شدن از 6/6 به 13 ميليون هكتار، مصرف كود‌هاي شيميايي با 35 برابر شدن از هفت به 250 كيلوگرم در هكتار، و تعداد تراكتور با 700 برابر شدن از 800 به 565 هزار عدد افزايش يافته است و كارآيي مصرف نهاده‌ها 300 درصد كاهش يافته و در مجموع نشان مي‌دهد كه كشاورزي ايران در طي دهه‌هاي گذشته فشرده‌تر شده و در عين حال ثبات عملكرد كاهش يافته است.

Introduction In the next 20 years, food production for the growing population is one of the most important issues. As increasing planting area is limited, improving productivity and yield is the only solution which could be reached through crop breeding and improving pest, disease and weeds control methods and increasing use efficeincy of fertilizers and water. Most of the time, increasing production in agricltulre is alongside with more intensification in agriculture. There is now specific definition for this term but in a general definition it means increasing the number of crops planted in unit of area (one hectare) through a year, as well as increasing using of inputs including fertilizers, chemicals and machinery in unit of area. Macleod and Moller (2006) evaluated the trend of intensification in Newzland agriculture by examining changes in 35 agricultural variables (e.g planting area, yield, inputs in unit of area and population related to agricultural production). Their results showed that intesnification is increased through 40 years (1961-200) which can threat sustainability of Newzeland farming in future. Agriculture intensification in Iran started since 1921 by using agricultural machinery and chemical fertilizers and increased rapidly after approval of land reform law in 1961s. Increasing the application of inputs in Iran agriculture has resulted to decrease sustainability of agricltural production and aslo destruction of forest and rangelands. Therefore, in this research time trend of intensification of cropping systems of Iran is studied using different indicators. Materials and Methods In order to evaluate the status and the trend of agriculture intensification in Iran, 63 variables in 5 groups including land use (cultivated area of each crop), production of each crop, yield, inputs (fertilizers, machinery and energy) and urban and ural population are examained for a 50-year period (1962 to 2011). Poduction stability was evaluated by calculating coeficeint of variance (CV) of planting area, production and yield in main agriculltural crops and fruits seperatly in each decades. For evaluating the sensivity of crops and fruit production to environmental changes the ratio of yield in a individual year to overal mean of yield for each ten years calculated for each crop seperately and for all crops as a yield capacity. The slope of the regression between yield capacity of each crop to yield capacity of all crops is an index for sensivity to environmental changes. All analysis and drwaing graphs were conducted using Xlstat 2014 and Excel 2103. Results Results showed that land use changes, increasing use of inputs and population growth are the main factors affecting intensification in Iran agriculture. From 1961 to 2011 the planting area has extended 2 times related to 6.6 million hectare at the beginning of this period and the agricultural productions increased to 94 million tons which was 7 times higher related to 13.3 million tons in 1961. During this period the main driving factor before 1980 is approving land reform law and increasing use of inputs which resulted to increase cultivated area and productions. In the following years increasing the application of fertilizers, agricultural machinery and new varieties were the main factors affecting agricultural productions and intensifciation. Our research showed that through the evaluation period, variance of cultivated area and production decreased but the variance of yield increased and hence yield stability decreased. Principal component analysis (PCA) classified 63 variables in two main compontents which first one described 51 percent of total variation including land use, production, yield trend and also uses of inputs. The second component described 20 percent of variation including input use efficiency and use of maschinery. Based on the changes in agicultural variables, PCA divided years into to 6 periods including 1962-1965, 1966-1980, 1981-1990, 1991-1998, 1999-2007and 2008-2011. During the first 3 periods agricultural area, production and yield were increased but during the next 3 periods the rate of increasing decreased. However, our research showed that Iran agriculture has been going through intensification in the last 50 years and approaching to food security is most likely possible through increasing efficient use of inputs by improving varieties and managmement of agricultural systems.