PHOSPHORUS DIFFUSION RETARDATION IN A CALCAREOUS SYSTEM BY COAPPLICATION OF POTASSIUM-CHLORIDE

The recommended methods of application of P and K fertilizers to agron omic crops are quite similar. As such, both fertilizer elements could be banded together in a single farm operation. This research was condu cted to provide information on the influence of K on the mobility and solubility of P added to a system having Ca2+ as the dominant exchange able ion. Four grams or KH2PO4 was added alone or in combination with 0.11 or 0.22 g of KCl to the surface of a Ca2+-saturated resin-sand co lumn. Extraction and analysis of each 2-mm layer of the column at 2 an d 4 wk after incubation showed that the mobility and the solubility of the added P was significantly reduced in the presence of KCl. This wa s a result of increased precipitation of P by Ca2+ displaced from the exchange sites. Thus, the availability of P to plants could be adverse ly affected in mixed P-K bands.