Oxalate and EDTA extractable soil phosphorus and iron in relation to P availability in lowland rice soils of West Africa uri icon


  • There is a complex relationship between iron (Fe) and phosphorus (P) in lowland soils grown to rice. There is, therefore, the need for quick and reliable extraction methods to assess their availability. The ability of ethylenediamine tetra acetic acid (EDTA) and ammonium oxalate (NH')2C20,┬ĚH20) to simultaneously extract Fe and P in soils was assessed with 15 soils from five important rice- growing cuntries in West Africa. The relationships between Olsen and Bray II P, inorganic P fractions and rice dry matter production and P uptake were also evaluated. The results showed that inorganic P fractions were in the order: Fe-PCa-PAI-P for 12 of the test soils, whereas AI-PFe-PCa-P was the order followed for two soils, and Ca-PFe-PAI-P for one soil. The mean Fe-P recorded was 77 mg P kg-I, although residual P recorded a higher mean of 153 mg P kg". Results of correlation analysis showed that correlation between EDT A-Fe and Oxalate-P was positive and highly significant (r= 0.92; PO.OOI). Similarly, highly significant relationship was established between EDTA-Fe and Fe-P, indicating that the two extractants were similar in selectivity of dissolution of inorganic phosphates and extractable Fe. Results from greenhouse pot experiments showed that there was higher and significant relationship (r

publication date

  • 1999