Dynamics of soil water content in the rhizosphere

• Published in: Plant and soil 2010-07, Vol.332 (1-2), p.163-176
• Main Authors: Carminati, Andrea, Moradi, Ahmad B, Vetterlein, Doris, Vontobel, Peter, Lehmann, Eberhard, Weller, Ulrich, Vogel, Hans-Jörg, Oswald, Sascha E
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Animal, plant and microbial ecology; Biological and medical sciences; Biomedical and Life Sciences; Biophysics; Botany; Drying; Ecology; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Hydraulic measurements; hysteresis; Life Sciences; Moisture; Moisture content; Mucilage; Neutron radiography; Physical properties; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Plant Physiology; Plant roots; Plant Sciences; Plants; Radiography; Regular Article; Retention; Rhizosphere; Root water uptake; Roots; Samples; Sand soils; Soil dynamics; Soil hydraulic properties; Soil moisture; Soil properties; Soil science; Soil Science & Conservation; Soil sciences; Soil water; Soil water content; Soil water retention; Soil-plant relationships. Soil fertility; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Water; Water and solute dynamics; Water content; Water flow; Water potential; Water retention curve; Water uptake
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-010-0283-8

Water flow from soil to plants depends on the properties of the soil next to roots, the rhizosphere. Although several studies showed that the rhizosphere has different properties than the bulk soil, effects of the rhizosphere on root water uptake are commonly neglected. To investigate the rhizosphere's properties we used neutron radiography to image water content distributions in soil samples planted with lupins during drying and subsequent rewetting. During drying, the water content in the rhizosphere was 0.05 larger than in the bulk soil. Immediately after rewetting, the picture reversed and the rhizosphere remained markedly dry. During the following days the water content of the rhizosphere increased and after 60 h it exceeded that of the bulk soil. The rhizosphere's thickness was approximately 1.5 mm. Based on the observed dynamics, we derived the distinct, hysteretic and time-dependent water retention curve of the rhizosphere. Our hypothesis is that the rhizosphere's water retention curve was determined by mucilage exuded by roots. The rhizosphere properties reduce water depletion around roots and weaken the drop of water potential towards roots, therefore favoring water uptake under dry conditions, as demonstrated by means of analytical calculation of water flow to a single root.