The fate of applied phosphate in a New Zealand yellow-grey earth, as influenced by phosphate carrier and soil reaction : thesis presented as part fulfilment of the requirements for the degree of M. Ag. Sc., Massey Agricultural College, University of New Zealand, Palmerston North, January 1961

Best copy available due to the original copy.A considerable amount of evidence has been accumulated in support of the presence in soils of iron, alurninium, and calcium bound phosphorus, as products of the phosphorus fixation process, but the quantitative evaluation of these forms has been continuously hampered by the lack of suitable procedures for their separate and selective determination. Although the separate determination of calcium bound phosphorus has been successl (Fraps, 1906; Fisher and Thomas, 1935; Ghani, 1943a) a procedure for the separate determination of iron and aluminium bound phosphorus was not available until recently when Chang and Jackson (1957) included such a method in their proposed scheme for the fractionation of soil phosphorus.Theirs is a definite advance on previous procedures as it has been generally considered that, at least in acid soils, these two forms represent the dominant products of phosphorus fixation, while their relative abundance may be expected to vary considerably in different soils and under different soil conditions. Fife (1959-I, 1959-II) modified the procedure of Chang and Jackson for the separate estimation of Al-P, and (priv.comm.) developed procedures for the selective determination of iron, calcium, and organic P. The object of the present study was to investigate what information these methods could provide concerning the trends of P. fixation in a New Zealand Yellow-Grey Earth from a long term field experiment, embodying three forms of phosphate fertiliser, applied with or without lime. [From Introduction