oa Agrochemophysica - A field and glasshouse evaluation of several potassium availability indices

Volume 5, Issue 1
  • ISSN : 0302-7112



In a pot study with Eragrostis curvula exchangeable ? (using neutral ? NH4OAc) and several quantity-intensity (Q/I) parameters were correlated with cumulative yield, cumulative ? uptake, and ? content of plant tissue. All the parameters used provided essentially similar indices of ? availability when soil was not dried prior to analysis. Air drying, however, markedly reduced the prognostic value of ? NH4OAc exchangeable ? and ? index A (given by - ? ? � X PBCK). In a field study with maize (Zea mays L.) the various indices of ? availability were correlated with ? content of the stover at four stages during the growing season. Although all soil analyses were conducted on air dry samples, ? NH4OAc exchangeable ? provided at least as good an index of ? availability as any of the other measures used and proved superior to equilibrium activity ratio (AR^) or indices involving PBCK measurements. Data from both the field and pot studies suggested that the form of the Q/I relationship was affected by air drying and ? fertilization.

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