REGULAR ARTICLE Hydraulic conductivity of the root-soil interface of lupin in sandy soil after drying and rewetting Mohsen Zarebanadkouki & Mutez A. Ahmed & Andrea Carminati Received: 26 February 2015 /Accepted: 8 September 2015 /Published online: 12 September 2015 # Springer International Publishing Switzerland 2015 Abstract Aims The putative role of the rhizosphere in controlling root water uptake is receiving increasing attention. Recent experiments showed that the rhizosphere turned temporarily hydrophobic after drying and subsequent rewetting. Our objective was to investigate whether the rhizosphere hydrophobicity influences the hydraulic conductivity of the rhizosphere-root continuum. Methods Lupins were grown in aluminium containers filled with a sandy soil. When the plants were 30 days- old, the soil was let dry to a water content of 2–4 % and then it was irrigated. The soil water content during irrigation was imaged using a time-series neutron radi- ography. By image processing, we quantified the in- crease in the volume of water in the roots upon irriga- tion. Using this information and additional measure- ments of the root pressure after irrigation, we calculated the water flow into the roots and the total hydraulic conductance of the rhizosphere-root continuum, K tot . Results The radiographs showed that: 1) the rhizosphere stayed temporarily dry after irrigation; 2) as the rhizo- sphere slowly rewetted, the roots rehydrated of 63 %. During 2 to 3 h subsequent to irrigation, K tot increased from 1.36±1.09×10 -11 m 2 s -1 MPa -1 to 5.02±2.13× 10 -10 m 2 s -1 MPa -1 , approaching the conductance of lupin roots in wet soils measured in previous experi- ments. Based on our calculations, these values of K tot correspond to a rhizosphere conductivity of 3.87± 1.91×10 -14 ms -1 (shortly after irrigation) and 1.09± 1.64×10 -12 ms -1 (2–3 h after irrigation). Conclusions We conclude that during a drying/wetting cycle, the conductivity of the root-soil interface is a temporary limit to root water uptake. We postulate that the temporary reduced hydraulic conductivity is primar- ily caused by the rhizosphere water repellency. Keywords Hydraulic conductivity . Hydrophobicity . Neutron radiography . Rhizosphere . Root pressure probe . Root-soil interface . Root water uptake Introduction Rate and location of root water uptake are influenced by the hydraulic conductivity of the roots and as the soil dries by the hydraulic conductivity of the soil in the vicinity of the roots, the so-called rhizosphere (Passioura 1988; Hallett et al. 2003). Both conductivi- ties vary over time and in space and are influenced by complex processes and root-soil interactions as briefly introduced in the next paragraphs. Plant Soil (2016) 398:267–280 DOI 10.1007/s11104-015-2668-1 Responsible Editor: Peter J. Gregory. Electronic supplementary material The online version of this article (doi:10.1007/s11104-015-2668-1) contains supplementary material, which is available to authorized users. M. Zarebanadkouki (*) : M. A. Ahmed : A. Carminati Division of Soil Hydrology, Georg-August University of Goettingen, Buesgenweg 2, 37077 Goettingen, Germany e-mail: mzareba@gwdg.de M. A. Ahmed Department of Agricultural Engineering, Faculty of Agriculture, University of Khartoum, Khartoum North, 13314 Shambat, Sudan