An experiment for determining the depth of penetration of various phosphates with the aid of P³².

Abstract

In addition to investigations into the depth of penetration of radio-active phosphates in the soil, studies were also made of the assimilation by plants of P₂O₅ derived from radio-active phosphates. Oats, peas, maize and potatoes were grown in Mitscherlich pots containing soil to which suitable quantities of fertilizers other than phosphate were added at the date of sowing or planting. One month after sowing or planting, 3 different types of phosphatic fertilizers, superphosphates, di-calciumphosphate and tri-calciumphosphate, were applied separately to all four types of crop. Equal quantities of P₂O₅ were applied, in the form of phosphate, to each pot and the radio-activity of the quantity of phosphate applied to each pot was 300 p. c. Measurements of radio-activity in the plants, made 11 days after application of the phosphates, showed that rapidity of absorption of P₂0₅ is conditional upon the water-solubility of the phosphate. In all cases the most P₂O₅ was present in the plants where superphosphate had been applied and the least where tri-calcium phosphate had been applied. The degree of radio-acitivity (indicating the quantity of P₂O₅ present) of maize, pea and potato leaves of different ages is shown graphically for each phosphatic treatment. In all cases the greatest quantities of P₂O₅ were assimilated by the youngest leaves and the least by the oldest leaves. Measurements of the radio-activity of leaves of equal age on different stems of a single potato plant indicated that there were differences in assimilatory capacity between different stems of the same plant. It was also observed that important differences in capacity to assimilate P₂O₅ existed between individual plants in the same crop.-W.J.B. (Abstract retrieved from CAB Abstracts by CABI’s permission)