How do soil P tests,plant yield and P acquisition by <Emphasis Type="Italic">Lotus tenuis</Emphasis> plants reflect the availability of added P from different phosphate sources |
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Authors: | Rodolfo Mendoza María del Carmen Lamas Ileana García |
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Affiliation: | (1) Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” (MACN-CONICET), ángel Gallardo 470, C1405DJR, Buenos Aires, Argentina |
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Abstract: | The relative effectiveness (RE) of each one of three different sources of P—P in solution (Psol), triple superphosphate (TSP)
and phosphate rock (PR)—for reflecting the availability of P in a P-deficient soil were assessed by measuring in Lotus tenuis variables associated with growth, organ morphology, and plant tissue P-content together with the amounts of P extracts from
soil by two of the currently used soil-P tests—Bray I and Olsen. A hyperbolic equation was used to fit the response curves
of each one of those plant variables to added-P. The ratio between the shapes of paired response curves of any P-sources was
used to compute the RE and substitution rate (K) of one source relative to the other. More P was needed from TSP and PR compared to Psol-100% soluble P-source. On the average
P applications as TSP relative to Psol and PR relative to TSP were only 68 and 63% effective respectively for plant growth.
Plant roots were more sensitive than soil-P tests to detect shifts in P-availability from different P-sources. Because soil
tests are commonly used to estimate the current P status in soil in order to calculate the optimum application levels of fertilizer
P for a crop or pasture, these results would have practical agronomical consequences if reproduced in other cultivated species
because they show that the response curve of a plant species as a function of added P and soil test might differ among fertilizer
types, measured plant variables, and the test used to measure P availability in the soil. |
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Keywords: | Bray I and Olsen Effectiveness of added P Lotus tenuis P-sources P uptake Response curves fitting |
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