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- Volume 5, Issue 1, 1973
Agrochemophysica - Volume 5, Issue 1, January 1973
Volume 5, Issue 1, January 1973
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A field and glasshouse evaluation of several potassium availability indices
Author E.H. Farina, M.P.W. & GravenSource: Agrochemophysica 5, pp 01 –08 (1973)More LessIn 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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A sensitive recording lysimeter
Author J.M. Mottram, R. & De JagerSource: Agrochemophysica 5, pp 09 –13 (1973)More LessAn economical and sensitive lysimeter for evaluating hourly water usage of crops has been designed, constructed and tested. A cylindrical steel lysimeter of surface area 2,5457 m2 and soil depth of 0,4 m rests on a mechanical balance system, having a resolution of 1 in 10 000. A precision strain gauge load beam of 0,1% accuracy and 20 kg capacity is incorporated in the balance lever system and its output is recorded on a galvanometric strip chart recorder. The complete system provides measurement of evapotranspiration to within 0,1 mm of water.
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The half-lives of 51Cr, 54Mn, 59Fe, 65Zn, 86Rb and 182Ta
Source: Agrochemophysica 5, pp 15 –16 (1973)More LessThe determination of half-lives for a number of nuclides in a well-type scintillation counter is descriptionbed.
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Research note : changes in the effectiveness of rainfall at the Grootfontein College of Agriculture
Author J. Tredoux, J. & PollockSource: Agrochemophysica 5, pp 17 –18 (1973)More Less
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Research note : a simple and inexpensive end-window GM-monitor
Source: Agrochemophysica 5, pp 19 –20 (1973)More Less