Click on image to view larger version.
Fig. 3. Most of the bicarbonate-extractable P remains in the surface soil with fluid or granular fertilizer P application. The P fertilizers used were fluid ammonium polyphosphate (APP, 10–34–0) and granular monammonium phosphate (MAP, 11–52–0). The APP was applied in the irrigation water (water-run) or sprayed on the soil surface (sprayed) and MAP was topdressed. The data presented includes the unfertilized control and P fertilizer applied at 5 g P m–2. Where differences in soil P were detected, higher values were generally measured with granular MAP than fluid APP. Movement of P in the soil profile was limited and not affected by P fertilizer source, except in 1997 where an accumulation of soil P was measured between 15 and 23 cm for granular MAP perhaps due to the greater amount of irrigation water applied at the time of fertilizer application that year. Soil P was usually not affected by whether APP was water-run or sprayed. The error bars represent the least significant difference at P = 0.05 [LSD(0.05)], or if the LSD is not significant, an "ns" appears next to the data points rather than an error bar.
