Soil water availability for plants as quantified by conventional available water, least limiting water range and integral water capacity

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• 作者：Hossein Asgarzadeh ; Mohammad Reza Mosaddeghi ; Ali Akbar Mahboubi ; Akram Nosrati and Anthony Roger Dexter
• 关键词：Soil available water content ; Soil water retention ; Soil mechanical resistance ; Least limiting water range ; Integral water capacity ; Soil physical quality
• 刊名：Plant and Soil
• 出版年：2010
• 出版时间：October 2010
• 年：2010
• 卷：335
• 期：1-2
• 页码：229-244
• 全文大小：273.8 KB

文摘

There are different approaches to define the soil available water (SAW) for plants. The objectives of this study are to evaluate the SAW values of 12 arable soils from Hamadan province (western Iran) calculated by plant available water (PAW), least limiting water range (LLWR) and integral water capacity (IWC) approaches and to explore their relations with Dexter’s index of soil physical quality (i.e., S-value). Soil water retention and mechanical resistance were determined on the intact samples which were taken from the 5–10 cm layer. For calculation of LLWR and IWC, the van Genuchten-Mualem model was fitted to the observed soil water retention data. Two matric suctions (h) of 100 and 330 cm were used for the field capacity (FC). There were significant differences (P < 0.01) between the SAW values calculated by PAW₁₀₀, PAW₃₃₀, LLWR₁₀₀, LLWR₃₃₀ and IWC. The highest (i.e., 0.210 cm3 cm−3) and the lowest (i.e., 0.129 cm3 cm−3) means of SAW were calculated for the IWC and LLWR₃₃₀, respectively. The upper limit of LLWR₃₃₀ for all of the soils was h of 330 cm, and that of LLWR₁₀₀ (except for one soil that was air-filled porosity of 0.1 cm3 cm−3) was h of 100 cm. The lower limit of LLWR₃₃₀ and LLWR₁₀₀ for five soils was h of 15,000 cm and for seven soils was mechanical resistance of 2 MPa. The IWC values were smaller than those of LLWR₁₀₀ for two soils, equal to those of LLWR₁₀₀ for three soils and greater than those of LLWR₁₀₀ for the rest. There is, therefore, a tendency to predict more SAW using the IWC approach than with the LLWR approach. This is due to the chosen critical soil limits and gradual changes of soil limitations vs. water content in the IWC calculation procedure. Significant relationships of SAW with bulk density or relative bulk density were found but not with the clay and organic matter contents. Linear relations between IWC and LLWR₁₀₀ or LLWR₃₃₀ were found as: IWC = −0.0514 + 1.4438LLWR₁₀₀, R 2 = 0.83; and IWC = −0.0405 + 2.0465LLWR₃₃₀, R 2 = 0.84, respectively (both significant at P < 0.01). Significant relationships were obtained between the SAW values and S indicating the suitability of the index S to explain the availability of soil water for plants even when complicated approaches like IWC are considered. Overall, the results demonstrate the importance of the choice of the approach to be used and its critical limits in the estimation of the soil available water to plants.