The paper deals with effects of ammonium sulphate (N), potassium sulphate (K) and double superphosphate (P), singly and in combinations (total 8 treatments) on the water retentive force of the soil at different moisture contents.
As the moisture content of the soil decreases the water retentive force of the soil increases. The changes in this force are less at higher moisture percentages while large changes are noted at lower moisture contents.
K has the least effect in reducing the water retentive force as soil is being depleted of its moisture, and P both singly and in combinations has the best effect in as far as it tends to keep the forces steady.
The fertilisers influence both the wilting coefficient and water retentive force of soils (Table III). In general the fertilisers bringing about increase, in wilting coefficient also bring about a corresponding decrease in water retentive force.
The gradient of increase in water retentive force of soils from high to low moisture content is higher in K treated soils and low in P treated soils (P, PN and KPN). This necessarily calls for drastic changes in the osmotic relations of the root cells of plants in K treated soils if the plants have to maintain a proper water balance.
It is concluded that a combination of P and N is the best treatment as far as water relations of plants are concerned for the proper growth and yield of crops under Indian conditions.