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Field experiments on phosphate fertilizers: A joint investigation

  • G. W. Cooke (a1)

Extract

The results of over 400 field experiments testing different kinds of phosphate fertilizers are summarized and are discussed with special reference to the reactions of the soils used. The classifications were:‘very acid’ soils—pH below 5·5, ‘acid soils’— pH 5·6 to 6·5, neutral soils—pH over 6·5. All comparisons are made in terms of fertilizers supplying the same amounts of total phosphorus.

In war-time experiments Gafsa and Morocco rock phosphates were about two-thirds as efficient as superphosphate for swedes and turnips grown on very acid soils. In 1951–3 experiments on very acid and acid soils Gafsa phosphate was practically equivalent to superphosphate for swedes, but for potatoes it was as effective as only one-third as much phosphorus supplied as superphosphate; on neutral soils Gafsa phosphate was useless. For establishing grassland on acid soils Gafsa and Morocco phosphate were equivalent to about onethird as much phosphorus supplied as high-soluble basic slag. Rock phosphates were somewhat more effective for promoting growth of established grassland but they remained inferior to high-soluble basic slags and to superphosphate. Curacao rock phosphate was roughly equivalent to Gafsa phosphate for swedes and grass. Florida pebble phosphate was much less effective and was judged unsuitable for direct application. Mixtures of rock phosphate with superphosphate were not more efficient than equivalent amounts of the separate components used correctly.

Silicophosphate was practically as effective as superphosphate for swedes grown on very acid and acid soils; it was less efficient on neutral soils. For potatoes silicophosphate was nearly as effective as superphosphate on very acid soils; it was much less efficient on acid and neutral soils. Silicophosphate was roughly equivalent to high-soluble basic slag for grassland.

Mixtures of superphosphate with lime, serpentine, and low-grade basic slag were prepared, most of the water-soluble phosphorus being converted to insoluble forms. In experiments on swedes and potatoes these basic superphosphates were not superior to untreated superphosphate. For establishing grassland on very acid soils, the mixtures were slightly superior to ordinary superphosphate.

Dicalcium phosphate was practically equivalent to superphosphate for swedes on all groups of soils. For potatoes dicalcium phosphate was more efficient than superphosphate on very acid soils, on less acid and neutral soils it was inferior to superphosphate.

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References

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Cooke, G. W. (1954). Proc. Fert. Soc. no. 27.
Cooke, G. W. (1955). Report on field experiments carried out from 1951 to 1953 to test phosphate fertilizers. Report presented to the Agricultural Research Council, no. A.R.C. 694/54.
Crowther, E. M. (1934). J. B. Agric. Soc. 95, 34.
Crowther, E. M. & Cooke, G. W. (1951). The production and agricultural value of silicophosphate fertilizers. Part VI. Field Experiments. Ministry of Supply Permanent Records of Research and Development, Monograph 11, p. 108.
Crowther, E. M. & Warren, R. G. (1934). Agric. Progr. 11, 99.
Crowther, E. M., Warren, R. G. & Cooke, G. W. (1953). The agricultural value of alternative phosphate fertilizers (other than silicophosphate). Part II. Field experiments. Ministry of Supply Permanent Becords of Research and Development, Monograph 11, p. 109.
D'Leny, W. (1953). Proc. Fertil. Soc. no. 24.
Elliot, A. G. (1944). N.Z. J. Agric. 69, 27.
Lea, F. M., Bessey, G. E., Nurse, R. W., Riddle, A. C. (1951). The production and agricultural value of silicophosphate fertilizers. Parts I, II, III & IV. Ministry of Supply Permanent Records of Research and Development, Monograph 11, p. 108.
Robertson, G. S. (1922). J. Minist. Agric. 29, 519.
Rogers, H. T. (1951). Agron. J. 43, 468.
Thorne, D. W., Johnson, P. E. & Seatz, L. F. (1955). Agric. & Fd Chem. 3, 136.

Field experiments on phosphate fertilizers: A joint investigation

  • G. W. Cooke (a1)

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