Australian researchers recently studied the reaction of both liquid and granular phosphorus (P) fertilizers in soil that was either dry or wet (at field capacity). They measured the movement of P from the application site as well as the amount of P that was in available and non-available forms.
They found that when soils were dry, very little diffusion occurred away from the site of application, and the P interactions with soil were negligible. This resulted in phosphorus remaining relatively unchanged and still in a plant-available form.
Another key finding was that granular sources resulted in higher amounts of available P compared with liquid P sources. However, when soils were wet, both granular and liquid P fertilizer experienced significantly more diffusion away from the application site and much more interaction with the soil. Consequently, when applied in wet soils, neither source differed in labile P.
These results show that there can be a distinct difference in how much P is soil available, based on which form is applied into dry and wet conditions. Keeping this research in mind can go a long way toward helping growers maximize their investment in P fertilizer.