سازگاری گندم دیم پاییزه به تغییر اقلیم در مناطق نیمه خشک و سرد با استفاده از تاریخ کاشت بهینه و آبیاری تکمیلی

تغییرات اقلیمی جهانی باعث تغییرات گسترده در متغیرهای اقلیمی شده است که در نهایت بر تولیدات زراعی تاثیر می‎گذارد. در شرایط حال و تغییر اقلیم آینده، راهکارهای سازگاری مانند تاریخ کاشت بهینه و آبیاری تکمیلی می‎تواند به یک تولید پایدار در سیستم‎های کشت دیم منجر شود. در این تحقیق اثرات تاریخ‎های کاشت (9 مهر، 23 مهر و 8 آبان) و رژیم‎های آبیاری (دیم، آبیاری تکمیلی در مرحله گل دهی و آبیاری تکمیلی در مرحله پر شدن دانه) بر عملکرد دانه گندم  در پنج شهرستان استان کردستان در دوره پایه و تغییر اقلیم آینده (پنج مدل گردش عمومی تحت سناریوی rcp8.5) با استفاده از مدل apsim-wheat ارزیابی شد. میانگین عملکرد دانه گندم دیم در استان کردستان در دوره پایه برابر 4.63 تن در هکتار بود. به‎طورکلی در همه شهرستان‎های استان کردستان (بجز سنندج) بیشترین عملکرد دانه در دوره پایه در تاریخ کاشت 9 مهر بدست آمد درحالی‎که در شرایط تغییر اقلیم، گندم بهترین عملکرد را در تاریخ کاشت 23 مهر داشت. در شهرستان سنندج در دوره پایه و تغییر اقلیم بالاترین عملکرد دانه به‎ترتیب از کاشت گندم در تاریخ‎های 23 مهر و 8 آبان حاصل شد. در شرایط تغییر اقلیم، عملکرد دانه گندم در رژیم‎های آبیاری در مراحل گل دهی و پرشدن دانه در مقایسه با رژیم دیم 8.7 درصد افزایش یافت. نتایج این پژوهش نشان داد که ترکیب تاریخ کاشت حدواسط (23 مهر)×آبیاری تکمیلی در مراحل گل دهی/پرشدن دانه به‎عنوان بهترین راهکار مدیریتی تحت شرایط تغییر اقلیم آینده شناخته شد و می‎تواند در مناطق با اقلیم نیمه خشک و سرد کشور پیشنهاد گردد.

adapting autumn rainfed wheat to climate change in semi-arid and cold regions using optimal planting date and supplementary irrigation

introduction: global climate change has caused extensive changes in climatic parameters such as rainfall and temperature, ultimately affecting field crop productions. considering continuous climate change and its effects on the agricultural sector, especially in arid and semi-arid regions, it seems inevitable to provide adaptation strategies to reduce climate change's negative effects and increase agricultural production. accordingly, the present study aimed to investigate the effect of planting date and supplementary irrigation (si) at important growth stages on wheat yield and growth in rainfed agro-ecosystems under baseline and future climate change conditions using the apsim-wheat model.materials and methods: the current study focused on five locations (bijar, marivan, saqqez, qorveh, and sanandaj) in kurdistan province, iran. the study locations were chosen based on being a cultivated rainfed wheat area, their climatic diversity, and the availability of long-term climate data (rainfall, sunshine duration, and minimum and maximum temperatures). the weatherman (weather data manager) program embedded in decision support system for agro-technology transfer (dssat) package was used to restore and modify missing and outliers data in the study locations. the apsim-wheat model was applied to predict the wheat development and growth (azar-2 cultivar). the performance of the crop model was evaluated based on the comparison of field-measured and simulated values for study traits. to do this, the willmott index of agreement (d-index), normalized root mean squared error (nrmse), mean bias error (mbe), determination coefficient (r2), and 1:1 line indicators were considered. the five gcms under rcp8.5 scenario were singled out based on five possible climate characteristics, including cool wet (ipsl-cm5b-lr), hot wet (hadgem2-ao), cool dry (gfdl-esm2g), hot dry (miroc-esm), and middle (cesm1-bgc). simulation experimental treatments in five locations were three irrigation regimes of (i) rainfed, (ii) si at flowering stage, (iii) and si at grain filling stage, and three planting dates of 1, 15, and 30 october at baseline period (1980-2010) and five gcms under the rcp8.5 scenario for 2040-2070 period.results and discussion: large variability was detected in rainfed wheat grain yield depending upon planting date and irrigation regime in five studied locations. wheat plants differently responded to planting dates and irrigation regimes in the kurdistan province, iran and varied from 1.81 t ha-1 (rainfed × 30-oct in qorveh) to 5.76 t ha-1 (si at flowering stage × 15-oct and si at grain filling stage × 15-oct in qorveh). the average grain yield of the entire wheat agro-ecosystems was 4.63 t ha-1. an increase of 6.9% was simulated for wheat grain yield entire kurdistan province, iran (as a semi-arid and cold agro-climatic zone) under future climate change conditions compared with the baseline. at the baseline period, the maximum wheat grain yield produced at an early planting date (1-oct) in all locations except for sanandaj, in which a mid-planting date (15-oct) had the highest simulated grain yield. the simulated grain yields were maximized at a mid-planting date in studied locations except for sanandaj, in which a late planting date (30-oct) had the highest grain yield under future climate change conditions. the si at flowering and grain filling stages had a similar effect on the wheat grain yield. averaged by planting dates and locations, the wheat grain yield was increased by 8.7% when si regimes were used compared with the rainfed treatment under climate change conditions.conclusion: the current findings showed that a mid planting date × si at flowering/grain filling stages was identified as the best management practice under future climate conditions and can be suggested in semi-arid and cold agro-climatic zone for the autumn wheat in the kurdistan province, iran.