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Field measurements of the water content in the top soil using a new capacitance sensor with a flat sensitive volume
Author(s) -
Ruth Bernhard,
Munch Jean Charles
Publication year - 2005
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/jpln.200421624
Subject(s) - soil water , water content , soil science , field capacity , evaporation , capacitance probe , environmental science , soil horizon , water retention curve , precipitation , capacitance , chemistry , geology , meteorology , geotechnical engineering , physics , electrode
Abstract Water content directly near the soil surface plays an essential role for degradation of natural organic material and agrochemicals by soil microbes. Furthermore, the water losses by evaporation depend sensitively on the top‐soil water content. Rain, irrigation, evaporation, and the water flow between the soil horizons together with the natural inhomogeneity of soils cause a high spatial gradient and a pronounced time dependence of the water content in the top soil. To understand processes in top soil such as redox gradients, the knowledge on ecological conditions in the top soil, which is subject to rapid changes, is essential. In order to meet the requirements for such field measurements, a capacitance sensor with a depth resolution of 1 cm and an active area of 7.5 cm × 14 cm was constructed and operated by a special electronic circuit. Field measurements using these sensors at 1 cm depth showed the high dynamics when measurements were carried out every 10 min. As simultaneous measurements of the soil temperature at 1 cm depth exhibit large temperature variations during the day, its influence on the measurements must be compensated for. As the data, measured during drying periods, allow the assessment of the temperature coefficient, the water content at a reference temperature can be calculated. The course of the water content reflects precipitation events and quantifies the drying of the soil, providing these parameters for process evaluation. Furthermore, the diurnal variation exhibits the drying during the day and the possible rewetting from deeper horizons during the night.