EFFECT OF LIMING ON AVAILABLE PHOSPHORUS CHANGES IN SOILS OF DIFFERENT PHYSICO-CHEMICAL PROPERTIES

摘要

In a laboratory experiment, the changes of extracted phosphorus (ΔEP) in 33 limed and non-limed soils were determined 7 and 30 days after fertilisation with P, as well as ΔEP and ΔEP_(Ca), indices were evaluated as related to P sorption and to certain soil properties. The concentration of available phosphorus in the soils was measured in 0.03 M CH_3COOH extract by the Nowosiclski method. The changes of the available P in the soil (ΔEP) calculated per unit of applied P were expressed as the incline of the curve, presenting the linear dependence between P added and P extracted. The increase of concentration of P by 1 mg per 1 dm~(-3) of the soil (the invers of AEP value) measured after 7 days' incubation was obtained after the addition of 3-4 mg Pper dm~(-3) and 7-14 rng of P dm~(-3) of the soil in soils of poor and high sorptivity, respectively. In the present investigations the simple indices of P sorption estimated for one P rate (e.g., PSI_(200) andPSI_(500)) were significantly correlated with ΔEP and ΔEP_(Ca), being therefore good indices of the prognosis of available phosphorus changes in fertilised soil, and useful in commercial soil tests.