پیشنهاد و ارزیابی یک روش آزمایشگاهی برای تعیین سریع کمیّت‌های مختلف آب قابل استفاده خاک برای گیاه

نوع مقاله: مقاله پژوهشی

نویسندگان

1 استادیار گروه علوم خاک دانشکده کشاورزی دانشگاه ارومیه

2 دانشیار گروه علوم خاک دانشکده کشاورزی دانشگاه صنعتی اصفهان

چکیده

یک روش آزمایشگاهی برای تعیین سریع و قابل اطمینان آب قابل استفاده خاک برای گیاه (SAW) بر اساس مفاهیم آب قابل دسترس (PAW)، دامنه رطوبتی با حداقل محدودیت (LLWR) و گنجایش آب انتگرالی (IWC) پیشنهاد و کارایی آن ارزیابی شد. نگهداشت آب (θ) برای 20 خاک کشاورزی در 13 مکش ماتریک (h) توسط دستگاه­های جعبه شن و صفحه فشاری تعیین شده و برای برازش مدل ون­گنوختن منحنی مشخصه رطوبتی خاک در روش مبنا (مرجع) به کار رفت. برای منحنی مشخصه رطوبتی خاک در روش پیشنهادی تنها از h­های صفر، 330 و hPa 15000 استفاده شد. مقاومت فروروی (Q) 10 نمونه دست­نخورده در رطوبت­های مختلف برای هر خاک با استفاده از ریزفروسنج در آزمایشگاه اندازه­گیری شد. به غیر از PAW با فرض h برابر hPa 100 برای گنجایش زراعی، تفاوت معنی­داری بین میانگین مقادیر مختلف SAW محاسبه­شده با روش پیشنهادی و روش مبنا وجود نداشت. روابط رگرسیونی خطی قوی بین مقادیر نظیر SAW محاسبه­شده با روش پیشنهادی و روش مبنا به دست آمد. بنابراین بدون نیاز به اندازه­گیری­های زمان­بر منحنی­های مشخصه رطوبتی و مقاومت فروروی خاک در h­های مختلف، تنها با اندازه­گیری مقدار نگهداشت آب خاک در h­های صفر، 330 و hPa 15000 و اندازه­گیری سریع مقاومت فروروی در رطوبت­های مختلف می­توان کمیّت­های مختلف آب قابل استفاده خاک برای گیاه را تعیین نمود. روابط خطی منفی و معنی­دار بین مقادیر PAW، LLWR و IWC با چگالی ظاهری نسبی (RBD) در خاک­های مورد بررسی، نشان داد که مقادیر SAW محاسبه­شده با روش پیشنهادی حساس به شرایط ساختمانی خاک بوده و می­توانند به عنوان شاخص­های کیفیت فیزیکی خاک استفاده شوند. نتایج بدست­آمده مؤید مفید­بودن این روش برای بدست­آوردن سریع و قابل اطمینان شاخص­های آب قابل استفاده خاک برای اهداف کاربردی و برنامه­ریزی آبیاری است. 

کلیدواژه‌ها


عنوان مقاله [English]

Proposing and Evaluating a Laboratory Method for Quick Determination of Different Quantities of Soil Available Water to Plant

نویسندگان [English]

  • Hossein Asgarzadeh 1
  • Mohammad Reza Mosaddeghi 2
1 Department of Soil Science, College of Agriculture, Urmia University, Urmia
2 Department of Soil Science, College of Agriculture, Isfahan University of Technology, Isfahan
چکیده [English]

A laboratory method was proposed and its capability was evaluated for quick and reliable determination of soil available water (SAW) for plant using concepts of plant available water (PAW), least limiting water range (LLWR) and integral water capacity (IWC). Water retention (θ) of 20 agricultural soils was detemined at 13 matric suctions (h) using sand box and pressure plate apparatuses. These data were fitted by the van Genuchten model and considered as the reference method. We used the soil water retention at h values of 0, 330 and 15000 hPa for the model fitting in the proposed method. Penetration resistance (Q) was measured on 10 undisturbed cores at different water contents for each soil using a lab micropenetrometer. Except for PAW (with h of 100 hPa considered as field capacity), there were not significant differences between the mean values of SAW determined by the reference and proposed methods. Strong regression lines were obtained between corresponding SAW values calculated by the two methods. Therefore, it is not needed to measure soil water retention and penetration resistance curves at several h values; instead water retention measurement at h values of 0, 330 and 15000 cm and quick measurement of penetration resistance at different water contents could be used for determination of different quantities for SAW. The PAW, LLWR and IWC were negatively and significantly regressed with relative bulk density (RBD) in the studied soils. These findings show that the SAW values calculated by the proposed method are susceptible to soil structure and might be considered as soil physical quality indices. The results showed suitability of the proposed method for quick and reliable determination of soil available water quantities which are useful for applied purposes and irrigation scheduling.

کلیدواژه‌ها [English]

  • plant available water
  • least limiting water range
  • integral water capacity
  • water characteristic curve
  • penetration resistance
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