برآورد ظرفیت افزایش تولید جو آبی در ایران از طریق حذف خلا عملکرد بر اساس روش گیگا

در این پژوهش میزان خلا عملکرد در مناطق اصلی زیر کشت جو آبی کشور طی سال‌های زراعی (1380-1394) از طریق دستورالعمل اطلس جهانی خلا عملکرد (گیگا) مورد بررسی قرار گرفت. ابتدا مناطق اصلی تولید جو آبی در کشور تعیین شدند؛ مناطقی که بیش از 85 درصد جو کشور در آن ها تولید می شود. 12 منطقه اقلیمی اصلی با استفاده از نقشه‌های پهنه‌بندی اقلیمی گیگا و پراکنش سطح زیر کشت جو آبی شناسایی شدند. پس از آن، 48 ایستگاه هواشناسی مرجع درون مناطق اقلیمی اصلی بر‌اساس میزان پراکنش سطح زیر کشت آن‌ها انتخاب گردید. تخمین خلا عملکرد در این مطالعه حاصل اختلاف بین مقادیر پتانسیل عملکرد برآورد شده توسط مدل ssm-icrop2 و عملکرد واقعی گزارش‌شده جهاد کشاورزی در هر rws طی 15 سال زراعی (1394-1380) می‌باشد. با استفاده از رویکرد پایین به بالای دستورالعمل گیگا، مقادیر خلا عملکرد جو آبی در سطح ایستگاه‌های مرجع برآورد شده و سپس به مناطق اقلیمی اصلی و در نهایت، به کل کشور تعمیم داده شد. تعمیم نتایج از سطح ایستگاه‌ها به مناطق اقلیمی نشان داد که دامنه تغییرات متوسط پتانسیل عملکرد برآورد شده در اقلیم‌های اصلی تولید جو آبی بین 5283 تا 8286 با میانگین 7090 کیلوگرم در هکتار بود، در حالی‌که دامنه عملکردهای واقعی بین 1406 و 3723 با متوسط 3009 کیلوگرم در هکتار در سطح کشور بود. در حال حاضر بین 3237 تا 4697 و به طور متوسط 4081 کیلوگرم در هکتار خلا در زمین‌های زراعی جو آبی کشور مشاهده می‌شود. به‌عبارت دیگر، در مناطق اقلیمی اصلی دامنه خلا عملکرد (%) بین 50 تا 76 و به طور متوسط 58 درصد در سطح مزارع جو آبی کشور برآورد شد. طبق این مطالعه می‌توان نتیجه‌گیری کرد که با حذف میزان خلا برآورد شده از طریق بهبود شرایط مدیریتی و راهکارهای به‌نژادیزراعی در زمین‌های زراعی جو آبی می توان مقدار تولید آن در کشور را از 2.21 میلیون تن در شرایط فعلی به 4.17 میلیون تن افزایش داد. این افزایش تولید (1.96 میلیون تن) می تواند بخش قابل توجهی از نیاز کشور به جو را تامین کرده و کشور را به‌سمت خودکفایی تولید این محصول نزدیک کند.

Estimating the Potential Increase of Irrigated Barley Production over Iran via Closure of Yield Gap Based on GYGA Protocol

IntroductionBarley (Hordeum vulgare L.) is considered as the second most important grain crop after wheat, due to 1.75 million hectares harvested areas and 3.2 million tons’ production in Iran. The irrigated fields are contributed up to 45% of total barley harvested areas (equivalent to 1.7 million ha) and 70% of total barley production (equivalent to 2.2 million tons). Based on the statistics reported in recent years, about 2.5 million tons of barley imported from other countries. According to the impossibility of extending the barley cultivated areas and even the necessity of reducing fields in some parts of the country, increasing productivity per unit area of cultivated lands is recognized as the only practical way to boost the production of barley in Iran. In this regard, this study was conducted to estimate barley yield gap (Yg) and the potential of increasing barley production in irrigated condition as the first step to promote the yield and production of barley over the country.Materials and MethodsFirstly, the main production zones of barley are determined; the zones which were contributed in more than 85% of barley production. The Designated climatic zones (DCZs) were identified using GYGA climatic zones (Global Yield Gap Atlas) and the distribution of barley harvested area raster layers. Subsequently, the Reference weather Stations (RWSs) within the DCZs were selected based on the values of the harvested area, and the types of soil in each of RWSs were determined by using of HC27 soil map. SSMiCrop2 as a crop simulation model has been employed to estimate the potential yield (Yp) in the RWSs of cultivated areas, which has previously been parameterized and evaluated, and the results have indicated the robustness of the model for simulating barley yield over the country. For estimating Yg, the data of actual yield (Ya) and the agronomic management data for estimating Yp during 15 growing seasons (20002014), were collected at RWSs scale. Using A bottomup approach, the yield, and production gap values were calculated at RWSs and subsequently aggregated to DCZs and finally, extended from DCZ to countrylevel according to the spatial distribution of crop area and climate zones.Results and DiscussionBased on GYGA protocol, 48 RWSs within 12 DCZs of irrigated barley harvested areas were demonstrated. Aggregation from the RWSs results to DCZs illustrated that the average of potential yield in DCZs of irrigated barley was estimated 7090 kg.ha1 and the range varied from 5283 to 8286 kg.ha1. Nevertheless, the Ya range in these climate zones was calculated between 1406 and 3723 with an average of 3009 kg.ha1. According to the results, the DCZs which confronted to higher temperatures during the growing season have lower yields and also a significant reverse correlation between the potential yield and the growth length period (R2 = 0.88 and p ≤0.01) were shown. The correlation between total received daily solar radiation during the growing and Yp in the DCZs was significant, positively season (R2 = 0.98 and p ≤0.01). At present, the range of difference between actual and potential yield varies between 3237 to 4697 kg.ha1 with an average of 4081 kg.ha1 (equivalent to 58% yield gap). In other words, just around 24 to 50 percent (on an average of 42 percent) of estimated Yp in irrigated barley fields can be attainable. According to the irrigated barley harvested areas, the actual and potential production gap are calculated about 2.21 and 2.99 million tons in the country, respectively, and under the best management condition can lead the production to be about 4.17 million tons.ConclusionAccording to the results, it was demonstrated about 58% relative yield gap between the averages of actual yield (3008 kg.ha1) and potential yield (7090 kg.ha1), which can be reduced by improving the production management in irrigated barley cultivated areas. For this reason, the current production of barley in irrigated lands can be increased from 2.12 to 4.17 million tons. This increase in production (1.96 million tons) could provide a significant part of the country’s need to the barley and bring the country closer to achieve full selfsufficiency.