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A REVIEW OF TRACER STUDIES IN SASKATCHEWAN ON THE UTILIZATION OF PHOSPHATES BY GRAIN CROPS *
Author(s) -
MITCHELL J.
Publication year - 1957
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1957.tb01869.x
Subject(s) - phosphorus , fertilizer , lime , agronomy , phosphate fertilizer , soil water , phosphate , environmental science , ammonium , phosphorite , chemistry , biology , soil science , paleontology , organic chemistry
Summary The use of P 32 as a tracer has been particularly valuable in studying the uptake of phosphorus from fertilizer and soil. It is a technique which may be used to differentiate between the availability of phosphorus in both soils and fertilizers. The work was done on soils well supplied with lime. The fertilizer was drilled with the seed unless otherwise stated. Results show that the wheat plant obtains most of its phosphorus from the fertilizer in the early stages of growth. The proportion obtained from the soil increases rapidly after the fourth week. Most of the phosphorus in the above‐ground part of the plant migrates to the head of the plant as it matures. Increasing the rate of application of the fertilizer results in a decreased utilization of soil phosphorus with a proportional increase in uptake of fertilizer phosphorus. The availability of phosphorus varies greatly in different carriers. Under the soil and climatic conditions to which the data apply mono‐ammonium phosphate had superior availability to calcium phosphates. Di‐calcium phosphates are relatively lower in availability than mono‐calcium phosphates. The availability of fertilizer phosphorus can be increased through the incorporation of small quantities of sulphur in the material. In drier areas at least the phosphatic fertilizers appear to be most effective when placed close to the seed. Under drought conditions a larger proportion of the phosphorus utilized by the plant comes from the fertilizer. Increased yields may result from the application of phosphates even under extreme drought conditions. Certain varieties of barley respond better to phosphatic fertilizer than do others. This differentiation did not appear in the wheat and oat varieties tested. The effect of different levels of radiation on plant growth and uptake of phosphorus has been studied in considerable detail. Deviations in results caused by radiation are considered unlikely to affect the type of experiments reported in this paper.