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Fluid Journal : Winter 2011
Winter 2011 The Fluid Journal 14 • 50 lbs/A P2O5 from Actagro Organic Acid phosphate -- "Structure" (7-21-0) • Water-only control. Trial results. Two days after application, by the NaHCO3 test, the organically-bound P had moved about twice as far as the next best source, which was 0-52-0. All treatments contained similar concentrations of total P (acid digestion) and P in soil organic matter (hot NaOH extract). The application of organically- complexed (reacted) ammonium phosphate (Actagro-P) or ammonium polyphosphate resulted in higher P fraction in the NaOH extract relative to the untreated control. The P fraction in the phosphoric acid treatment was not significantly different from the untreated control, possibly due to dissolution of Fe oxides and Ca compounds in soil after application of phosphoric acid and consequent precipitation when the pH was raised during the extraction with NaOH. The organically-complexed (reacted) ammonium phosphate did not react readily with soil constituents. After 42 days, however, all treatments contained similar amounts of the NaOH fraction. Application of ammonium polyphosphate did not change the plant-available phosphate content at 2 days under the drip tape (depth 0 to 3 inches) as indicated by the Olsen P concentration (Figures 1 and 2). Application of phosphoric acid increased plant-available P shortly after the application and only at depth and distance up to 3 to 6 inches from the drip tape. Application of organically complexed P (Actagro-P) resulted in a higher Olsen-P concentration at a depth greater than 6 inches. After 42 days following fertilizer application and multiple irrigations, significantly higher concentrations of plant- available P were detected in the Actagro-P treatment compared to other treatments (Figures 3 and 4). The P applied in Actagro-P fertilizer seemed to move twice the distance as compared to the other two fertilizers. There were numerical increases from organically complexed phosphate and ammonium polyphosphate, but not significant differences in P contents among treatments in the 6- to 9-inch depth and 6- to 9-inch distance (Figures 5 and 6). Fresno, California This was the site of a study conducted by Dr. Charles Krauter on a campus farm at California State University Fresno. The site selected was a Hanford Sandy Loam soil with a pH of 7.2 and 0.5 percent limestone. Olsen's PO4-P was 48 ppm. Methodology. Prior to the trial initiation, two tons of very fine lime (<200 mesh) was spread on the soil and incorporated by cross disking to a depth of about 6 to 8 inches with two passes of an offset double disk. Soil was sprinkler irrigated two days later with half-inch water to speed up chemical reactions. Flat soil was pulled into beds on 5-foot centers. Fifteen days later, pretreatment soil samples were taken. A special 12-inch x 12-inch x 1.5-inch box soil sampler was used to determine P movement down and away from the surface drip line. The sampler was driven into the soil with a mallet at right angles to the drip line. The full sampler was dug out with a shovel, opened, and soil segmented into sixteen Figure 5. Phosphorus fractions in soil at 3-6 inches depth under tape and 3-6 inches from the tape after 2 days (top) and 42 days (bottom) following applica- tion of three liquid fertilizers. Figure 6. Phosphorus fractions in soil at 6-9 inches depth under tape and 6-9 inches from the tape after 2 days (top) and 42 days (bottom) following drip application of three liquid fertilizers.
Early Spring 2011