Phosphorus and Micronutrient Interactions in soil and their Impacts on Maize Growth

NTERACTIONS AMONG phosphorus (P) and micronutrients may greatly influence plant growth and soil productivity. Thus, a greenhouse investigation of a complete randomized design was conducted to highlight such interactions in which a clayey soil (enriched with either 5 mg Fe kg -1 soil , 1mg Mn kg -1 soil ,or 1.5 mg Zn kg -1 soil) received P in the form of calcium superphosphate at three rates equivalent to 6.7 (P1), 13.4 (P2, recommended dose) and 20.1 mg P kg -1 (P3). Then, the soil was planted with maize seeds ( Zea mays L var f16) for 60 days. Our results showed that application of P3, but not P2, raised significantly the fraction of P in soil which was extracted by ammonium bicarbonate-diethylene Tri amine penta acetic acid (AB-DTPA-P) versus P1. Likewise, AB-DTPA extractable Fe and Mn increased significantly in soil with increasing the rate of applied P, while AB-DTPA extractable-Zn decreased. In P-Fe interaction experiment, increasing the dose of applied P enhanced significantly maize dry weights, although did not affect significantly their heights. This is because P applications led to significant increases in Fe and K contents within plant tissues. Regarding P-Mn interactions, application of P2 significantly raised Mn content within plants while the highest application rate of P (P3) diminished this content. In spite of that, maize dry weights seemed to be comparable between P2and P3 and both exhibited higher dry weights than P1. Finally, results of P-Zn interactions revealed that both N and Zn contents significantly increased within plants due to increasing the rate of applied P fertilizer. Accordingly, plant dry weights increased significantly. In conclusion, plants that received the recommended doses of P or even less need to absorb more micronutrient (Fe, Mn and Zn) from soil for metabolism and growth; yet, high P inputs increased the uptake of Fe and Zn by plants while diminished Mn uptake.