Soil phosphate values in relation to phosphate supply to plants from some Nigerian soils

Abstract

SUMMARY: Phosphate uptake and dry-matter yield from unfertilized pots and relative yield (ratio of unfertilized to fertilized yield) of Rhodes grass were used as plant indices of P supply from twenty-four soil samples from long-term manurial trials in Nigeria. Although measurements of the soil P quantity factor were generally the more important, intensity measurements also made a highly significant independent contribution to the P supply. Inorganic P (a quantity measure) combined with the log of P concentration in a saturation water extract (an intensity measure) gave a multiple correlation coefficient of R = 0·954^*** with relative yield, accounting for 91% of its variation. The best single measure was resin-extractable P, which gave r =0·930^*** for correlation with relative yield. Organic P did not appear to contribute to plant growth.