Resistance to water flow in soil and plant. 1. Soil resistance in relation to amounts of root: theoretical estimates.
Data are presented for a range of species including perennial grasses, white clover, lucerne, cereals and soyabeans on the length of roots per unit area of soil surface. Evidence is presented which indicates on theoretical grounds that appreciable rhizosphere resistances to water flow are much less common than generally supposed and will remain smaller than the plant resistance until near or beyond the permanent wilting point. Some of the experimental evidence is not in accord with this conclusion.-R.B.