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Fluid Journal : Spring 2014
12 The Fluid Journal Spring 2014 1). In the Andisols, there were no significant differences in the percentage of fertilizer labile P between MAP and FlMAP (applied at the volume of 200 μL, Figure 1a,b), whereas in the Oxisols, significantly more P remained labile with MAP than with FlMAP (Figure 1c,d). In contrast to the acidic soils, in the calcareous Pt Kenny soil significantly more P (62%) remained isotopically exchangeable (labile) with FlMAP than with the granular counterpart (38%, Figure 1 e). As expected in the Monarto soil, there were no differences in terms of lability between the fertilizer treatments (Figure 1f). The lack of increase of labile P in the acidic soils fertilized with fluid P indicates that the effect of dilution of the P in a larger volume of soil may have prompted strong sorption reactions onto the Al and Fe oxyhydroxides removing P from the labile pool. However, in the calcareous soil, this dilution effect was advantageous, likely by reducing opportunities to form Ca-P precipitates. Concentration. The concentration of soluble P was significantly greater in the inner soil section compared to the outer soil section in all the soils (data not shown). In the Andisols and Oxisols the increase in soluble P at >7.5 mm from the point of fertilizer application was minimal with either granular or fluid fertilizer, reflecting the strong P sorption capacity of these soils. In the Pt Kenny soil, a greater concentration of soluble P in the outer soil section (>7.5 mm) was measured with the fluid than with the granular MAP (0.97 vs. 0 .09 mg PL-1), which is also consistent with the greater lability measured in this soil with fluid MAP. Summing up The results from this study indicate that the application of fluid P fertilizers, in soils where adsorption reaction predominates, is of little or no benefit. For these soils, the recommended P management strategy is banding the fertilizer to limit its contact with the soil, thereby reducing opportunities for strong adsorption reactions to occur. Unfortunately, in these strongly P-sorbing soils the recommended P fertilization demands the use of large amounts of P, thus becoming a strategy that is economically restrictive for many farmers. There is still much scope to improve the efficiency of P fertilizers in acidic high P-fixing soils. Daniela Montalvo is a PhD student at the University of Adelaide; Dr. Fien Degryse is a Senior Research Fellow in Soil Science at the University of Adelalide; and Prof. Mike J. McLaughlin is a Research Fellow at CSIRO Land and Water, and Professor in Soil Science at the University of Adelaide. ACT NOW! JOIN IN THE SUPPORT OF THIS ORGANIZATION THAT DIRECTLY BENEFITS YOUR BUSINESS! The Fluid Fer tilizer Foundation • 2805 Claflin Road, Suite 200, Manhattan, KS 66502 Write, call or e-mail the Fluid Fertilizer Foundation Phone: 785-776-0273 • E-mail: email@example.com Research and education for efficient use of fluids. The Fluid Fertilizer Foundation We need you to join hundreds of other growers, dealers, fertilizer manufacturers and other supporting industries