Influence of phosphorus and iron interaction on iron fractions in heavy and light textured soils

Abstract

In both light and heavy textured soils, exchangeable-Fe significantly decreased with increasing phosphorus (P) application, compared to the control and at each successive P level. The exchangeable-Fe was the lowest among the inorganic Fe fractions, constituting only about 0.02% of the total Fe extracted, regardless of soil texture. Carbonate-Fe significantly increased with higher P application levels, both over control and at each successive rate. Regarding iron (Fe) application, the carbonate-Fe fraction also increased significantly with higher soil-applied Fe, while foliar Fe application had no significant impact on carbonate-Fe. This fraction accounted for approximately 0.02% of total Fe. The FeMn oxide fraction significantly increased with increasing P application in both soil textures, averaging 2.6% of total Fe extracted. Organic matter-bound Fe (OM-Fe) decreased significantly with higher P levels, averaging 1.25% of total Fe, irrespective of soil texture. There was no significant effect of P and Fe application on residualFe, which accounted for 2.7% of total Fe extracted. Overall, the study highlights a negative interaction between phosphorus and iron. These findings are useful for developing balanced fertilization strategies, particularly in crops sensitive to iron deficiency, as they suggest that excessive P application may reduce Fe availability and efficiency.