THE MEASUREMENT OF SOIL WATER TENSION IN THE FIELD

Abstract

The water in soil under growing plants is not in equilibrium and knowledge of the soil water tension must be based on direct measurements from several tensiometers. A cheap, reliable and easily maintained tensiometer for field use is described. The instruments are constructed mainly from nylon, with mercury manometers, and have been assembled in sets of six with a single support and mercury reservoir for the manometers. The nature and extent of the variation of the water tension from point to point in the soil have been measured at a number of sites in the Oxford district. On arithmetic scales frequency distributions are very skew but may be normalized by logarithmic transformation (to pF). The degree of variation is in general moderate: coefficients of variation range from 4 % to 25 % depending on kind of soil and time of year. Since the cost of the tensiometers described is low there is no reason why comparative studies on soil water tension should not be carried out with adequate replication. Copyright © 1966, Wiley Blackwell. All rights reserved