| Sumario: | The external phosphorus requirement for Vigna unguiculata L. var. Tuy (Frijol bayo) was determined in pot and field experiments The chosen soils were corrected for macro and micro-nutrients deficiences using the corresponding elements and lime Although this correction was made, the pot yield obtained differed livin soil to soil, therefore it could be concluded that other factor(s), apart from P. is controlling the production.
A maximum production was obtained, in all the cases (except Uracoa series), at P equilibrium in the soil solution corresponding nearly to 1.0 ppm. This last value could be adscribed as the P requirement in the green-house experiment. As expected, this value decreased significantly (0.6 ppm) when the experiments were conducted in field conditions. The phosphorus requirements for each soil studied are presented.
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