Lime and Zn application effects on soil and plant Zn status at different growth stages of rice in tropical acid sulphate paddy soil

The acid sulphate soils in tropics are characterized with low pH (<4), high Al3+ and Fe2+ content, low basic cations and low phyto-available Zn concentration that can adversely affect the rice growth. A two year field experiment was conducted to explore the Zn and lime application and their interaction effects on soil and rice tissues Zn status in Zn deficit tropical acid sulphate paddy soils. The maximum increase in available Zn at no limed plots was obtained at 10 kg ha-1 Zn level about an average of 12 folds and lime application decreased it about 20% compared to control. The average increase in leaves, stems and grains Zn concentration due to Zn application at maximum tillering was 60%, 35.5% and 200% respectively at 10 kg ha-1 Zn level. The highest correlation coefficient between grain Zn concentration and available Zn, root Zn, panicle Zn and stem Zn was 0.96**, 0.92**, 0.92**, and 0.97**, respectively. The Zn concentration of grain had positive significant correlation with bran Zn (0.93**) and white rice Zn (0.91**). The highest increased percentage of Zn uptake in limed plots was 2.11% and 1.59%, 1.465 and 1.23% with 10 and 5 kg ha-1 Zn application, respectively. The highest Zn concentration in rice tissues at maximum tillering was recorded in roots; followed by stems, and leaves. Whereas, the order at flowering stage was as follows: root> stem> panicle>leave. Finally, at harvesting stage this order of Zn concentration in roots, stems, grains, panicles and leaves was observed.