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3. Soil-phosphate Studies. The reactions between soil and phosphate are of great interest not only from a scientific, but also from the economic, point of view. Fundamental work on the extraction of phosphate from and fixation of added phosphate by soiJs has shown that the reactions are greatly dependent on the pH value of the suspension of soil and solution. The extraction of phosphate is least in the region pH 3-4, and the fixation of added phosphate is greatest in the region pH 3-5. On either side of these minima great increases in the quantities of phosphate in solution are found. Soil type, also, is important in governing the amounts of phosphoric acid in solution at any given pH value, whether the phosphate is derived from the soil itself or from added phosphate. . . . In the literature of this subject it is proved indirectly that oxides of iron and aluminium are probably the chief agents in fixing added phosphate. Soils freed from these oxides were therefore prepared with their clay fractions converted into sodium and calcium forms. Similar soils with these compounds present, either with or without organic matter, and soils freed from both organic matter and these oxides were also prepared. It was shown that when the iron and aluminium oxides (R 2 0 3 compounds for convenience) were removed the fixation of added phosphate was very small, fixation due to organic matter was therefore negligible as compared with the fixation due to R 2 0 3 compounds. By varying the concentration of phosphate in the solutions presented to the soils, at approximately constant pH values, it was shown that the percentage fixation decreases with increase of concentration of phosphate, the degree of reduction being dependent on the soil type. Under certain conditions the calcium clays fixed slightly more phosphate than the sodium clays, but the amount of phosphate fixed by the R 2 0 3 compounds did not vary with the type of clay present, The extraction of phosphate from soils after fixation depends on the pH value of thei extracting solution and also on the type of solution ; for example, 1-per-cent. citric acid and 0-02 M NaHb0 4 solutions both have a pH. value of approximately 2-0, but the citric acid extracts much more phosphate than the hydrogen sulphate and does not suffer such great changes in pH value from reaction with the soil. The case of extraction varies from soil type to soil type. In general, the lower the fixing-power of the soil for added phosphate the more easily is the combined phosphate subsequently Gxtrāct6(l From the results obtained it would appear that many New Zealand soils are capable of fixing large quantities of phosphate in a form which would probably be relatively unavailable to plants. In raising the pH value of the soil by liming fixation of added phosphate would be decreased. On acid soils of high fixing-power the use of basic superphosphate or basic slag would therefore probably be more satisfactory than the use of straight superphosphate. 4. General. During the year the following Pasture Research publications have been published No. 26. Soil Phosphate Studies. Part I : " Solubility of Soil Phosphate and Fixation of Added Phosphate at varying pH Values," by H. 0. Askew. No. 27. Soil Phosphate Studies. Part II: "Fixation of Phosphate by R 2 0 3 Oxid.es m Sodium and Calcium Clays," by H. 0. Askew. H. 0. Askew, Officer m Charge. PAKIHI SOILS RESEARCH. SEVENTH ANNUAL REPORT OF THE PAKIHI INVESTIGATIONS CONDUCTED BY THE CAWTHRON INSTITUTE. Introduction. With the very limited finance available work in connection with the pakihi reclamation has been restricted mainly to the maintenance of the small farm of 24 acres laid down in previous years and the oversight and top-dressing of the small experimental plots dealing with the use of lime, phosphatide manure, and the growth of different grasses and clovers. In addition, the plantations of shrubs and trees likely to prove serviceable for shelter purposes have been extended. Pampas-grass has also been planted to ascertain its value for fodder and shelter-purposes under pakihi conditions. Small Farm. Twenty-four acres of pasture were sown in two blocks of 11 acres and 13 acres respectively in March 1932 and 1933 In both cases a good strike of grasses and clovers was obtained, and satisfactory sward-development has taken place. During the first year after establishment grazing was permitted only during the summer, autumn, and early winter months. In the second year grazing was conducted throughout the whole of the year. , Under such conditions of stocking and top-dressing at the rate of 2 cwt. of superphosphate per acre the pastures have improved, and more valuable grasses, such as perennial rye and cocksfoot are now more prominent than was the case in the first season. Consolidation of the land has also taken place, and no difficulty has been experienced in holding stock on the pastures throughout the winter. During the summer and autumn it would have been possible to have-taken a motor-car over practically the whole area which has been grassed. In order to maintain the lime-status of the pastures an additional \ ton of ground limestone per acre was applied in March, 1935, on the block originally

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