A pot experiment was conducted during 2017 at Department of Soil Science and Agricultural Chemistry, Tamil Nadu Agricultural University, Coimbatore to study the effect of Zinc Solubilizing Bacteria (ZSB) and different Zn sources on zinc nutrient and enzyme activity of rice crop in a Completely Randomized Block design. The treatments consisted of four zinc sources (No zinc, ZnSO4, ZnO and Zn-EDTA) and with and without ZSB inoculation. Beneficial effects of ZSB and Zn sources on Zn content and uptake in above ground and root at critical growth stages and enzyme activity at panicle initiation stage were observed, with significant increases in all the determined parameters, in comparison with the control. Among the Zn sources, ZnSO4 @ 25 kg ha-1 significantly increased the Zn content in rice grain (32.6 and 42.2 mg kg-1), straw (25.9 and 30.2 mg kg-1), above ground (29.0 and 36.3; 33.5 and 38.4 mg kg-1 at active tillering and panicle initiation stage respectively) for without and with ZSB respectively. The root Zn content decreased with rice growth stages and ZSB with ZnSO4 recorded the highest Zn content of 44.0, 39.5 and 34.8 mg kg-1 at active tillering and panicle initiation and harvest stage respectively compared with other Zn sources. The application of ZnSO4 with ZSB markedly increased the above ground shoot Zn uptake (0.41 and 1.73 at active tillering and panicle initiation stage respectively), root Zn uptake (0.48, 0.54 and 0.74 g plant-1 at active tillering, panicle initiation and harvest stage respectively), grain and straw Zn uptake (1.96 and 1.32 g plant-1) compared to ZnO and Zn-EDTA. The activity of Zn requiring enzymes viz., superoxide dismutase (SOD) and carbonic anhydrase (CA) also significantly increased by the application of ZnSO4 with ZSB (232 and 12.15 EU mg-1 FW) followed by ZnO with ZSB (124 and 10.94 EU mg-1 FW) and Zn-EDTA with ZSB (120 and 10.56 EU mg-1 FW).
Key words : Rice, Zn sources, ZSB, Zn content, enzyme activity, SOD, CA.