نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی ارشد فیزیک و حفاظت خاک گروه خاکشناسی دانشکده کشاورزی دانشگاه زنجان.

2 دانشیار فیزیک و حفاظت خاک گروه خاکشناسی دانشکده کشاورزی دانشگاه زنجان.

چکیده

 
محتوای آب خاک نقشی مهم در رشد گیاه به­ویژه در کشتزارهای دیم مناطق خشک و نیمه‌خشکایفاء می­کند. آگاهی از عوامل مؤثر بر میزان نگهداشت آب در خاک برای مدیریت آب حاصل از بارش­آسمانی و هم­چنین درک طیف وسیعی از فرآیندهای هیدرولوژیکی شامل نفوذ، رواناب، و تبخیر و تعرق ضروری است.این متغیر تحت تأثیر هم‌زمان آب‌وهوا، ویژگی­های خاک، پوشش زمین و توپوگرافی قرار دارد. در این بررسی، تغییرات محتوای آب خاک در هفت کشتزار گندم دیم با شیب چهار، هشت، 11، 15، 18، 20 و 24 درصد تحت شرایط آیش در غرب استان زنجان مورد بررسی قرار گرفت. محتوای آب خاک در عمق 20 سانتی‌متر در سه کرت (5/1 متر ×5/2 متر) با فاصله پنج روز در طول دوره رشد گندم زمستانه از سال 1394 تا 1395 اندازه‌گیری شد. محتوای آب خاک تغییرات زیادی را طی دوره پژوهش نشان داد که با تغییر ماهانه بارش همگام بود. تفاوتی معنی­دار بین کشتزار­ها از نظر محتوای آب خاک وجود داشت (01/ 0P<). محتوای آب خاک از شیب چهار تا 11 درصد به شدت کاهش یافت اما کاهش آن در شیب­های بالاتر (15-24 درصد) ناچیز بود. کاهش در محتوای آب خاک در کشتزار­ها به افزایش رواناب سطحی در آن­ها مربوط بود. ماتریس همبستگی (r) برای تعیین اثرات ویژگی­های کشتزار­ها (درجه شیب و خصوصیات خاک) نشان داد که محتوای آب خاک با درجه شیب، شن، رس، ماده آلی و نفوذپذیری خاک همبستگی معنی­داری در سطح یک درصد دارد. تجزیه‌وتحلیل رگرسیون چندگانه نشان داد که محتوای آب خاک رابطه­ای معنی­دار با شیب و مقدار شن دارد (01/0>P و 78/0=2R).بر این اساس محتوای آب خاک در کشتزارهای دیم مناطق نیمه­خشک را می­توان با استفاده از درجه شیب و مقدار شن خاک برآورد نمود.

کلیدواژه‌ها

عنوان مقاله [English]

Investigating the Role of Slope Gradient and Soil Properties in the Variations of Soil Water Content in Rainfed Lands of Semi-Arid Regions, Northwest of Iran

نویسندگان [English]

  • F H 1
  • A V 2

1 MSc. student, Soil Physics and Conservation Engineering, Department of Soil Science Faculty of Agriculture, University of Zanjan.

2 Associate Professor of Soil Physics and Conservation Engineering, Department of Soil Science Faculty of Agriculture, University of Zanjan.

چکیده [English]

Soil water content (SWC) plays an important role in plant growth, particularly in rainfed lands in arid and semi-arid regions. Knowledge of the variability of SWC is critical for understanding a range of hydrological processes including infiltration, runoff, and evapotranspiration. It is an integrative state variable affected by climate, soil properties, land cover, and topography. In this study, the variability of SWC was investigated in seven wheat rainfed lands with 4%, 8%, 11%, 15%, 18%, 20%, and 24% slope under fallow conditions in west of Zanjan province. The SWC was measured at a depth of 20 cm in three plots (1.5 m×2.5 m) with 5-day interval during the growing period of winter wheat from 2014 to 2015. The SWC showed a large variation during the study period which was associated with the monthly variation of precipitation. Significant (P< 0.01) difference in the SWC was found among the lands. The SWC steadily decreased from 4% to 11% slope and showed a negligible decline in higher slopes (15-24%). Decrease in the SWC in the lands was attributed to increases in the surface runoff. Correlation matrix (r) for determining the effects of land characteristics (slope gradient and soil properties) showed that the SWC was significantly correlated with slope gradient, sand, clay, organic matter contents, and soil infiltrability. Multiple regression analysis indicated the SWC was significantly (R2= 0.78, P< 0.01) related to slope gradient and sand content. The SWC in the semi-arid rainfed lands can be reliably estimated using the slope gradient and sand content in the soil.
 

کلیدواژه‌ها [English]

  • precipitation
  • Particle size distribution
  • surface runoff
  • winter wheat
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