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K‐ACTIVITY RATIOS AND THE UPTAKE OF POTASSIUM BY RYEGRASS IN THE FIELD
Author(s) -
BECKETT P. H. T.,
CLEMENT C. R.
Publication year - 1973
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.1365-2389.1973.tb00743.x
Subject(s) - potassium , crop , field (mathematics) , mathematics , chemistry , agronomy , soil science , zoology , environmental science , biology , organic chemistry , pure mathematics
Summary A model (based on the short‐ and long‐term Q/I relations of K in a soil, on graphs of K‐uptake by crop against post‐uptake K‐activity ratios, and the exhaustion value of K‐activity ratios below which K can no longer be taken up) is presented by means of which to estimate the amount of labile K in a soil, and to compare the contributions of labile and fixed K to plant uptake. The application of the model was partially explored in a field experiment. Relative values for the magnitudes of the pools of labile and fixed K developed by 4 years’build‐up treatments were calculated on the basis of the model. Their relative contributions to the K taken up by a ryegrass test crop in the following year were calculated from the soil Q/I relations, and the measured uptakes of K. While the data were incomplete and so could not provide conclusive evidence for the model, the values produced were sensible and apparently consistent.