Variation in moisture contents between bulk soil and the rhizosheath of wheat (Triticum aestivum L. cv. Wembley)

There is conflicting evidence as to whether rhizosheath soil can be wetter or drier than bulk soil. The gravimetric moisture contents of bulk soil and the rhizosheath of wheat were determined for plants grown in a glasshouse over a range of dry bulk densities (1.0, 1.1 and 1.3 Mg m−3). Plants were also grown in soil at 1.1 Mg m−3 at 15 °C in a controlled environment. No significant differences in soil moistures over the initial dry bulk density range examined were found. Overall, rhizosheath soil was significantly (P < 0.05) wetter than bulk soil. In the second experiment, under controlled environment conditions, significant differences (P < 0.05) were found only at the lowest depth range examined. The mechanism behind preferential wetting of the rhizosheath is examined with reference to other work on transfer of water to soil from roots, physical changes in the rhizosheath, and root exudates. The most likely explanation of these results is that the presence of mucigel within the rhizosheath increases the water‐holding capacity of that soil. Copyright © 1995, Wiley Blackwell. All rights reserved