Infiltration of Organic Phosphate Compounds in Soil

Organic phosphate compounds may be moved greater distances into soil than is possible with inorganic phosphates inasmuch as organic phosphates must be enzymatically hydrolyzed to orthophosphate before soil reactions inhibit movement. The hydrolysis in solution and movement in soil of six organic phosphates were investigated in order to evaluate possible advantages of the compounds as fertilizers. The compounds studied were glycerophosphate, methyl ester phosphate, glycol phosphate, ethyl ester phosphate, glucose 1‐phosphate, and glucose 6‐phosphate. The infiltration of organic P compounds into Panoche clay loam soil and glycerophosphate into five soils differing in texture, clay type, organic matter, and pH and into one soil at three water contents was investigated by infiltrating organic P solution into columns of dry or moist soil at a rate of 66 kg of P/ha. Inorganic P concentration in bicarbonate extracts was measured as a function of soil depth at the termination of infiltration. The movement of P from organic compounds was compared with the movement of potassium phosphate. All the organic phosphates hydrolyzed at similar rates. The P from all the organic compounds moved to approximately the 12‐cm depth in the calcareous Panoche clay loam soil with only slight differences in P concentration above that depth, whereas inorganic phosphate moved no more than 2–3 cm. The enzymatic hydrolysis rate of glycerophosphate and the resulting P distribution after infiltration was influenced by soil type. The greatest P movement (12 cm) occurred in Panoche clay loam, and the least amount of movement occurred with Aiken clay loam. Soil‐water content had only a slight effect on glycerophosphate movement for the one soil studied.