Availability of Phosphorus in Granulated Fertilizers

Abstract

A greenhouse test to measure the effect of placement, granule size, and the relative phosphate fixing capacity of the soil upon the efficiency of superphosphate and dicalcium phosphate was performed. The materials, labeled with P32, granulated, and sized to 4–6, 8–10, 14–20, 28–35, and −35 mesh were used in band and mixed placements on Evesboro and Davidson soils. A major difficulty encountered in greenhouse experimentation with granulated fertilizers stems from the problem of securing small samples for pot application that truly represent the test materials. Even with close‐sized materials the minimum representative sample of coarse granules is several‐fold larger than the quantity required for pot application. The test crop was wheat. Using increased yields, total phosphorus uptake, and percentage of the plant phosphorus derived from the fertilizer as criteria of agronomic value, the 14–20 mesh granules of superphosphate were the best size tested with this material while the 28–35 and −35 were the best sizes tested with dicalcium phosphate.

Effects of radioactive phosphate fertilizers on yield and phosphorus uptake by ryegrass in pot experiments on calcareous soils from Rothamsted

“…In most of the work reviewed earlier in this paper labelled fertilizers were applied on the surface of the soil or near the seed. This results in an uneven distribution of phosphate in the soil have been reported in pot experiments by Starostka et al (1954). In the first experiment, effects due to the way the phosphate was added to the soil were at least as great as those due to the amount of M P tested; this suggests, as other workers have done (Bould et al 1953;Russell et al 1954), the need to describe very fully the experimental designs and methods used in work with tracers so that all factors that might affect results can be examined critically.…”

“…McAuliffe et al (1949) considered that chemical 'fixation' and microbial conversion of fertilizer phosphorus during growth would result in the percentage of phosphorus derived from the fertilizer decreasing during an experiment. Fried & Dean (1952) have shown that the amount of phosphorus taken up from a fertilizer depends very greatly on its distribution in soil, and Starostka, Caro & Hill (1954) have recently observed in pot experiments, differences in plant growth, total phosphorus uptake and fertilizer uptake that were due solely to the particle size of the superphosphate and dicalcium phosphate they tested.…”

Effect of Water Solubility and Granule Size of Phosphorus Fertilizers on Alfalfa Grown in a Calcareous Soil1

“…Starostka et al ( 9) and Schmehl et al ( 7) found that dicalcium phosphate gave yield responses comparable to 1 concentrated superphosphate when the fertilizer was finely divided and mixed with the soil. Schmehl et al 7did not recommend band application of materials low in watersoluble P. Starostka et al (9) suggested that the optimum granule size of concentrated superphosphate was 14-to 20• mesh for band placement and 8-to 10-mesh for mixed placement; minus 35-mesh dicalcium phosphate was considered satisfactory for mixed application on the soils used in their experiment. Webb and Pesek ( 11) found that 60% or more of the P in a fertilizer should be in watersoluble form for Iowa soils.…”

Particle-size effects of water-soluble phosphate fertilizer

“…Most experiments designed to evaluate particle-size effects of phosphate fertilizers have been field or greenhouse experiments or a combination of these two. In experiments with dicalcium phosphate, phosphate rock, and other essentially water-insoluble sources, small fertilizer particles usually have been better than large particles as a source of phosphorus for plants (Bouldin and Sample, 1959 On the other hand, "in experiments conducted with water-soluble phosphate sources, the granulated or large fertilizer particles usually have been better than the nongranulated or small fertilizer particles (Bouldin, 1956;Lawton and Cook, 1955;Starostka et al, 195b;and Wilding, 1950) except on calcareous, soils, where the opposite effects have been observed (Bouldin, 1956;Terman, 1958;and Wilding, 191*9). Larsen (1955), after conducting field experiments for 5 years in Denmark with granulated and powdered superphosphate, concluded that large par ticles of superphosphate had little, if any, agronomic advantage over small particles, but that they should be preferred because of the improved physical condition of the granulated fertilizer.…”