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Fluid Journal : Winter 2016
absorbance near edge of structure, or XANES spectroscopy. The Idaho soil analysis was performed at sector 9 BM- B, Advanced Photon Source Facility, Argonne National labs, Chicago, IL. For the Kansas and Australian soils, it was performed at the Canadian Light Source Inc., Soft X-ray Micro- characterization Beamline (SXRMB) 06B 1-1, Saskatoon, Saskatchewan, Canada. Spectra for the P standards and the center section of the treatment samples (0-7.5 mm) were edge energy calibrated, background corrected and normalized. All spectra collected were analyzed by linear combination fitting (LCF) using IFEFFIT software (Newville, 2001). Results pH. For the Kansas soil (Figure 1), generally, the P treatments had significantly lower pH as compared to the control except in the third section that had been treated with MAP. Mono- ammonium P and DAP treatments were not significantly different from each other in the 7.5-13.75 mm section. The pH was lowest at the point of application for all P treatments and increased back to the pH of the control soil by the fourth dish section. This most likely was the result of the effect of acidification due to the nitrification of ammonium (NH 4 ) contained in the P fertilizer or added as urea. Overall, APP had the lowest pH for the 4 dish sections, suggesting greater diffusion or movement of NH 4 compared to the 2 granular fertilizers. The effects of the P treatments on soil pH results were very similar for the Idaho and Australian soils (data not shown). Percent P added. Because each granule could potentially have slightly different amounts of P, we look at added P as a percent of the total added P in each section to understand fertilizer P diffusion. The greater the diffusion or P movement away from the point of application, the less the chance for the formation of P precipitates. For the Kansas soil (Figure 2), most of the added P fertilizer remained close to the point of application with DAP having significantly less movement than APP from the 0-7.5 mm dish section. Phosphorus diffused into the 7.5-13.75 mm section for all 3 treatments and there was significantly more fertilizer P movement into this section for the fluid P 7 Table 2. P XANES - Idaho Soil Soil P species (oÆ>) Section 1: 0-7.5 mm Treatment pH Calcium Ferri hyd rite- Vivianite Reduced Phosphate Adsorbed P Chi-Square Control 8.52 68.6 31.4 -- 0.06 MAP 7.58 59.2 31.0 9.8 0.02 DAP 8.07 64.1 35.9 -- 0.04 APP 7.38 27.8 48.2 24.0 0.04 10..00 a K Percent Resin P 60..00 ... 50..00 :c .. 40..00 . Ð:: ..... :c ]0..00 . v - . 20..00 ... 10..00 0.00 eu..-.uI . lAP DAP APP . 8-15 . 15-11.15 . ".15-25 . 25-43..5 Figure 5. Kansas percent Resin P: The APP treatment had significant greater resin extractable P as a percentage of total P for the first two sections as compared to the MAP, DAP or Control treatments. 90.00 80.00 70.00 60.00 . c.. c: .Vi CJJ c:::: 50.00 +' c: CJJ u 40.00 CJJ c.. 30.00 20.00 10.00 0.00 20 30 P T.. ___.. . . . . . y = -1.43x + 119.27 R 2 = 0.65 . . 40 50 60 Percent Ca-P (XANES) . .. 70 80 90 Figure 6. The relationship between Percent Resin P and the occurrence of Ca-P for all three soils. The Fluid Journal Winter 2016