Effect of phosphite and phosphate in different pH on yield, growth and P status in Broccoli

Phosphite (PO33; Phi; valence of +3), a reduced form of phosphate (PO43; Pi; valence of +5), that are being widely marketed either as an agricultural fungicide or as a superior source of plant phosphorus (P) nutrition. The present study was conducted to investigate the effect of phosphite and phosphate in different pH on yield, growth and P status in broccoli (Brassica oleracea L var. italica cv. Fiorentino). The experiment was conducted with three pH levels (5.5, 7, 8.5) factorially combined with three P source levels (Pi, Phi and Pi& Phi). The plants were grown in black buckets containing 8 L of aerated nutrient solution for 10 week after transplanting. Phi had statistically significant negative effect on yield and was formed immature heads and to form button-like flower heads. Likewise, Phosphite increased phosphorus and potassium concentration in the leaves, roots ,Stems and heads. Both P and K concentration were significantly reduce by the increase pH level. The highest yield was observed in Pi& Phi with pH(5.5) at 237 g plant -1 .Phosphate (pH=5.5) compare to Phosphite (pH=5.5) increased by 75% in yield. . The increase in Pi uptake in the Phi treatment plant caused increased in P concentration in leaves and growth reduction and phytotoxicity. The negative effects application of only Phosphite was strong inhibiting effect in fresh weight head. Hence, Phosphite was not available to the plants as a P source.