الفهرس 
The interaction between phosphorus and Zinc, iron, manganese and seleniumOnly 14 pages are availabe for public view
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Abstract
This study was carried out at laboratory and green house of Faculty of Agriculture at Moshtohor, Benha University, Qalyubia Governorate, Egypt, throwing light on the interactions that may occur between P and either Zn ,Fe , Mn and Se upon fertilizing soils with these elements. It includes two experiments, one of these experiment was the lab incubation experiment (the first experiment) and the other experiment was a pot experiment (the second experiment) under greenhouse conditions.
First experiment:
The interactions among nutrients in soil, particularly among P and micronutrients may greatly influence plant growth and productivity, though P-applications diminish considerably micronutrients availability in soil. These interactions are not well investigated. Likewise, selenium (Se) availability is affected with P- application. The current studies investigate the consequences of amending soils (a clayey non-calcareous soil and a sandy calcareous one) with elevated P -doses (15, 30, 60 and120 mg P kg-1) on AB-DTPA-extractable Fe, Mn, Zn and Se within the first 72 h of application. A pot experiment was therefore conducted following a complete randomized design to attain this aim. Briefly, soils were enriched with 5 mg Fe, 1 mg Mn, 1.5 mg Zn and 10 mg Se kg-1 then received the abovementioned P-doses and incubated for 72 h while keeping soil moisture gravimetrically at field capacity throughout this study. Key results revealed that AB-DTPA extractable-P increased significantly with increasing the rate of applied-P and these increases were noticeable with ageing. In contrast, AB-DTPA-Fe content was not affected significantly by such application. Regarding AB-DTPA extractable Mn and Zn, their contents increased progressively in the non-calcareous soil with P60 or higher up to 48h of application while remained statistically unchangeable in the non-calcareous soil. In both soils, the dose of applied-P did not significantly affect AB-DTPA-Se yet this available fraction was affected by soil ageing following cycles of increases and decreases.
Second experiment
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, 1.5 mg Zn kg-1 and 10 mg Se kg-1 soil received P in the form of calcium superphosphate at three different rates i.e. 6.7, 13.4 (recommended dose) and 20.1 mg P kg-1 referred to them by the symbols P1, P2 and P3, respectively. The soil under study was planted with maize seeds (Zea mays L var f16) for 60 days. Our results showed that application of P3 raised significantly extractable AB-DTPA- P in soil compared to the addition of P1 while, the corresponding increases owing to application of P2 did not affect extractable P significantly. Likewise, AB-DTPA extractable Fe and Mn increased significantly in soil with increasing the rate of applied P, whereas AB-DTPA extractable-Zn decreased. The P-Fe interaction experiment revealed that increasing the dose of applied P enhanced significantly maize dry weight, although did not affect significantly the plant height. This is because such increasing applied P-rates led to concurrent significant increases in Fe and K content 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 Mn content. In spite of that, maize dry weights seemed comparable between P3and P2 and both of them exhibited higher dry weight than those received 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. Likewise, AB-DTPA-Se increased significantly in soil; yet such increases were significant only with the application of the highest rate of P. In plants, Se uptake decreased significantly with increasing the rate of applied P. Generally, maize fresh and dry weights increased significantly owing to application of P at a rate of 13.4mg Pkg-1(P2), while decreased with increasing the rate of applied-P. In this concern, there were negative correlations between AB-DTPA extractable Se and maize fresh and dry weights.
In conclusion, More experiments are needed using more time sequences within the first 48 h of application, plants that received the recommended doses of P or even less need to absorb more micronutrient (Fe, Mn, Zn and Se) from soil for metabolism and growth; yet, high P inputs increased the uptake of Fe and Zn by plants while diminished Mn uptake. So, interactions between P and soil micronutrients at high doses need further investigations to be clarified, while P inputs at a rate of 13.4mg P kg-1(P2) raised significantly P uptake while diminished the uptake of Se. This probably indicates that P inputs suppress the influx of Se to plant roots. At higher P rates, both Se and P uptake decreased considerably. This might indicate that selenium (Se) underwent co-precipitated with P in soil.