Estimation of soil-water extraction patterns by roots

In this paper, a simple method for estimation of soil-water extraction distribution by roots S (z) is described. S (z) is determined mainly by the distribution of the surface area of the roots. From field measurements it followed that typical distribution of the surface area of roots, as well as their mass, in a sufficiently moist soil has an exponential form. If plant canopy transpiration is potential, soil-water extraction distribution S(z) can be obtained from the root mass distribution. In case soil water potential is less than ‘critical’ and, therefore, the transpiration is lower than the potential transpiration, S(z) will be proportional to the soil water potential.Water-extraction patterns of maize roots, calculated from field data, were compared with calculated S (z) -values. There was a good agreement between that S (z) determined from field measurements and that calculated by means of the suggested method. In the case where the transpiration was potential, S (z) was exponential and was similar to the root mass distribution.