Influence of Hydrogen-Ion Concentration on the Adsorption of Plant Food by Soil Colloids

COMPOSITION OF CURRENT AND PREVIOUS SEASON'S BRANCH GROWTH IN RELATION TO VEGETATIVE AND REPRODUCTIVE RESPONSES IN PYRUS MALUS L

“…The whole question of the mechanism of the reciprocal relationship between nitrogen, phosphorus, and potassium in relation to their absorption by plants has been discussed in detail by the writer elsewhere (206,208). It may be pointed out here, however, that no generalizations are possible with respect to the K/N ratio because the absorption of these elements by the plant is a function of the level of nutrition, i.e., rate of supply of nutrients (206,208 (197), this increase in the absorption of phosphorus may be interpreted as the result of an increase in the solubility of phosphorus following a decrease in the already existing potential difference between the micellar and intermicellar soil solution by the KE and NO3-ions, in accordance with the GIBBS-DONNAN law (1,49,116,183,185,208 The position of the water balance within a plant is determined by the power of the roots to maintain the supply and the power of the leaves to resist excessive loss. The rate of water loss, if the plants do not differ internally in some manner affecting transpiration, will depend upon the nature of the leaves and the area of foliage produced.…”

The rôle of kaolinite in phosphate fixation

“…In 1921 Harrison and Das (20) concluded that in noncalcareous soils the retention of P 205 is mainly due to adsorption, whereas in calcareous soils retention by adsorption is either nonexistent or entirely masked by other causes. Shortly thereafter, the work of Gordon and his Feb., 1939] Murphy: Kaolinite in Phosphate Fixation 345 associates (19,25,45) and of Mattson (27)(28)(29)(30) began to appear in the literature in support of a colloidal mechanism. Other recent investigations (6,18,31,33,34,35,37,38) furnish confirming evidence of this kind of action.…”

“…Artificially prepared hydrogels and hydrosols of iron and aluminum have been shown (16,25,45,47) to remove P0 4 from solution. Gordon and his associates (25,51) found that while iron and aluminum hydrogels were able to hold on to the adsorbed phosphate tenaciously against distilled water and certain sulfates, O.IN solutions of NaOH and NH 40H were capable of removing some of the adsorbed phosphate, and the plants were able to utilize P0 4 from the freshly prepared material.…”