A point of limited availability of water in soil and its determination

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Abstract

The point of limited availability of water (PLAW) characterizes the lower boundary of the area of the most productive moisture for plants. The analysis of experimental methods for determining PLAW indicates their labor intensity and low productivity. The aim of the study was to develop a high-performance and accurate method for determining PLAW. 18 samples from various soils were used in the work. To determine the PLAW, a method was proposed in which soil samples were placed in a Schott funnel, moistened with excess water, and then the water was pumped out using a water jet pump. As the water was removed from the sample, the interval between drops falling from the funnel increased. A jump in the intervals between drops was considered an indicator of the end of the experiment. Experiments have shown that the soil moisture content obtained by vacuuming correlates with the values calculated for the lowest soil moisture capacity (according to Dolgov) by 87%. The values of the PLAW obtained by the secant method (according to Voronin) for some of the soil samples do not fall out of the obtained dependence. Using the method, it was shown that soil drying leads to a decrease in the value of the measured PLAW. An explanation of the results from the position of the presence of organomineral gels in soils is proposed.

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About the authors

G. N. Fedotov

Lomonosov Moscow State University

Author for correspondence.
Email: gennadiy.fedotov@gmail.com
Russian Federation, Moscow

S. A. Shoba

Lomonosov Moscow State University

Email: gennadiy.fedotov@gmail.com

Corresponding Member of the RAS

Russian Federation, Moscow

I. V. Gorepekin

Lomonosov Moscow State University

Email: gennadiy.fedotov@gmail.com
Russian Federation, Moscow

A. I. Sukharev

Lomonosov Moscow State University

Email: gennadiy.fedotov@gmail.com
Russian Federation, Moscow

D. A. Tarasenko

Lomonosov Moscow State University

Email: gennadiy.fedotov@gmail.com
Russian Federation, Moscow

A. P. Shvarov

Lomonosov Moscow State University

Email: gennadiy.fedotov@gmail.com
Russian Federation, Moscow

Z. Tyugai

Lomonosov Moscow State University

Email: gennadiy.fedotov@gmail.com
Russian Federation, Moscow

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Supplementary files

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2. Fig. 1. Dependence of the time interval between drops falling from a Schott funnel on the ordinal number of the drop

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3. Fig. 2. Change in soil moisture content (SMC) from the time interval between drops falling from a Schott funnel when wet (2) and dry (1) air passes through a sod-podzolic soil sample

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4. Fig. 3. The relationship between the experimental values ​​of capillary rupture humidity by the vacuum method and the calculated values. The points obtained by the intercept method are highlighted in red.

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5. Fig. 4. Effect of moisture content of gray forest soil samples on the determined values ​​of capillary rupture moisture (CRM)

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