Publisher: Bachudo Science Co. Ltd

Determination of Phosphorus Requirements of Cowpea (VIGNA UNGUICULATA) In The Acid Soils of Southeastern Nigeria Using Sorption isotherms

V. E. Osodeke
KEYWORDS: Phosphorus, Sorption Isotherms, Cowpea


This study was conducted to determine the phosphorus requirement of cowpea in two locations in southeastern Nigeria (Bende and Umudike) using sorption isotherm. The method used involved equilibrating 3g of soil in 30mls of 0.01 m CaCb containing various levels of phosphorus at room temperature for 5 'days. From the P sorption curves constructed, the standard P requirement for the two soils were calibrated. The values were very low at 21.5 and 45pgg·1 for Bende and Umudike soils respectively. Different phosphorus levels were calibrated from the sorption isotherm ourves and used in fertilizing cowpea in potted experiment. The experiment was laid out in split-plot experimental design. The soil type occupied the main plots while the P levels were assigned to the subplots. The results obtained indicated that solution P concentration level of 0.2pgg·1 equivalent to21.5kgha- in Bende and 45kgha·1 in Umudike gave the best nodulation while grain yield was produced when solution P concentration of 0.4μgg-1 equivalent to 65kgha·1 in Bende and 125 kgha-1 in Umudike was applied. The grain yield at this level was not significantly different from those at 0.2μgg·1 solution concentration of P in both locations. Higher yield were recorded in the soils of Urhudike compared to that of Bende.

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