The effect of five levels of fluorine (0, 25, 50, 100, and 200 ppm F as sodium fluoride) and four levels of phosphorus (0, 25, 50, and 100 ppm P as KH2PO4) on the yield and chemical composition of rice (Oryza sativa) grown on soils of two sodicities, ESP 30 and 70, was studied in a thrice replicated pot experiment. Increasing levels of fluorine, above 50 ppm F, decreased the dry matter yield in the early growth stages and grain yield at maturity, especially at ESP 70. Application of phosphorus increased the plant growth and grain yield. Both phosphorus and fluorine interacted significantly in affecting the dry matter yield and plant composition. The adverse effect of added fluorine was nullified by greater application of phosphorus.
Fluorine uptake by plants was greater in high than in low ESP soil, mainly because of the higher solubility of added F at high ESP. Addition of P decreased the F content of the plant and thereby helped in reducing the toxic effect of F on growth.
Fluorine increased the Na and decreased the Ca, Mg, K, and P contents of the plants. Application of P decreased Na and F and increased the Ca, Mg, K, and P contents of the plants. Increased ESP decreased the plant growth, grain yield, Ca, Mg, K, and P, but increased the Na and F content of the plants.