This study investigated the interactive effects of phosphorus (P) and zinc (Zn) application on P and Zn availability, and growth of rice (Oryza sativa) in an Alfisol. In a laboratory incubation experiment, soil samples were supersaturated with treatment solutions with all possible combinations of four P levels (0, 6, 12, and 24 mg kg-1 equivalent to 0, 10, 20, and 40 kg ha-1, respectively) and three Zn levels (0, 1.2, and 2.4 mg kg-1 equivalent to 0, 2, and 4 kg ha-1, respectively), and then allowed to air-dry. Available P and Zn contents in soil increased as the application rates were increased but P×Zn rate interaction effect was not significant. In a pot experiment, rice (var Bg 358) was grown for 10 weeks with all possible combinations of three P levels (0, 5.5, and 16.5 mg kg-1) and three Zn levels (0, 1, and 2 mg kg-1). Initial soil P was higher than the critical level (12 mg kg-1), but available Zn was below the critical level (1.5 mg kg-1). The main effect of P rate did not significantly affect the number of tillers and shoot dry matter content while Zn application decreased them. Root dry matter, and root and shoot P concentrations were significantly (P<0.05) influenced by P×Zn rate interaction effect. While, plant P uptake was significantly decreased due to P and Zn application, plant Zn uptake was not affected. Therefore, for a better growth of rice plant, the soils with high available P and low Zn contents should be carefully fertilized with P and Zn fertilizers.
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