The Reaction Between Phosphate and Phosphate‐fixing Soils

Abstract

Summary Phosphate‐fixing soils and hydrated iron and aluminium oxides have their power of sorbing phosphate reduced if they are pretreated with reagents forming insoluble or unionized compounds with iron and aluminium ions. Soils sorb many more milliequivalents of these blocking reagents than correspond to the drop in their phosphate‐sorbing power, and it does not seem to be possible for a soil to sorb so much of one of these reagents that it ceases to sorb phosphate. Blocking reagents such as potassium ferrocyanide and 8‐hydroxy‐quinoline cannot be used to distinguish hydrated iron from aluminium oxides as the agents causing this phosphate sorption. Soils which have been treated with hydrosulphite to remove some of the free hydrated iron and aluminium oxides still sorb phosphate, but this sorption is reduced to a very low value if the soil is then treated with a blocking reagent. The fulvic acid fraction of soil organic matter is a good blocking agent. Fulvic acid and blocking reagents such as aluminon and alizarin S cause the soils to deflocculate in 0.1 N sodium acetate.

Sorption of Inorganic Phosphate by Iron‐ and Aluminium‐ Containing Components

“…(1963) found the reverse. The effect of dryiqg observed in the present study is consistent with the work of Gorbunov (1959) and probably explains the low P sorption by Fe gel reported by Leaver and Russell (1957) who used only a dried sample of an Fe gel preparation. Sorption of P by haematite slightly exceeded that by goethite in the present study.…”

Characterization of two tobacco cell lines selected to grow in the presence of either ionic Al or insoluble Al-phosphate

“…The excretion of citrate in response to the presence of insoluble phosphate may be another rescue mechanism in plants which enables them to obtain phosphate from inorganic phosphates. In soils, a large proportion of the phosphate applied as fertilizer is fixed in the form of AI-phosphate (LEAVER and RUSSELL 1957). Our observations may thus be relevant to the utilization of phosphorus by plants from the fixed form of the ion in soils.…”

Re‐evaluation of characteristics of a carrot cell line previously selected as aluminum‐tolerant cells

“…The excretion of eitrate in response to the presenee of insoluble Al-phosphate may be another system to obtain phosphate from insoluble and inorganic phosphates. In soils, a large proportion of the phosphate applied as fertilizer is fixed as a form of Al-phosphate (Leaver and Russell 1957) and the availability of phosphorus is limited in the world (Ando 1983). Our findings may therefore be relevant to the utilization of phosphorus by erop plants from the fixed form of the ion in soils.…”