A comparison of mobility and availability of granular and fluid phosphate fertilizers in calcareous soils under laboratory conditions

Phosphorus fixation in a calcareous soil is a major factor limiting mobility and availability of P fertilizer. This work employed Petridish to investigate the differences between granular and fluid forms of P fertilizers placed in three calcareous soils. The results indicate that Olsen-P is decreased with increasing distance from the central section where the fertilizer is applied. The contents of soil Olsen-P under the fluid fertilization in all sections are higher than those of the granular fertilization except the 0-7.5 mm section. Almost 55%-70% of the fertilizer P remains within 7.5 mm section from the granule fertilizer, but in other three sections, this value is lower than that of the fluid fertilizers, especially in 7.5-13.5 mm section (fluid 35%> granular 20%). The three fertilizer amounts show the same diversification in three soil types. Changes in pH caused by the fertilization are small and limit to the soil section where the fertilizer is applied. Soil pH is significantly low in the 0-13.5 mm section across all soil types (P<0.05). When apply different forms of P fertilizers to the calcareous soils, the fluid fertilization can provide a greater diffusion, availability compared with the granular fertilizers.