Effect of levels and sources of zinc on growth, yield and economics of rice (Oryza sativa) under temperate conditions

A field experiment was conducted during the rainy (kharif) seasons of 2011 and 2012 on silty clay loam soil of Khudwani, Anantnag, Jammu and Kashmir medium in Zn with neutral pH, to assess the response of rice (Oryza sativa L.) to levels and sources of Zn. Factorial combinations of 3 levels of Zn (3, 6 and 9 kg/ha), supplied through 5 sources (ZnSO₄, ZnO, zinc-enriched urea, Zn-FYM incubated and Zn-EDTA) and 1 absolute control was laid out in randomized complete block design with 3 replications. A significant response was observed to Zn application up to 6 kg/ha in respect of growth parameters like plant height, leaf-area index (LAI), dry-matter accumulation, and number of tillers/hill. The Zn sources had a significant effect on LAI and number of tillers only. Yield attributes, namely panicles/m², panicle length, and grains/panicle, also got significantly increased up to 6 kg Zn/ha and the same were at par with 9 kg Zn/ha. Application of 3 and 6 kg Zn/ha increased the grain yield by 5.7% and 10.9% over the control, respectively, during 2011. The corresponding figures for the year 2012 were 7.1% and 14.3%. The data averaged over 2 years showed that Zn-EDTA though at par with Zn-enriched urea and Zn-FYM incubated, realized 6.4% and 7.6% higher grain yield compared to ZnO and ZnSO₄ respectively. Zinc concentration in brown rice averaged over 2 years increased from 38 to 49 mg/kg with the increase in Zn application rates from 3 to 9 kg/ha respectively. The Zn-EDTA resulted higher Zn concentration of 46.4 mg/kg respectively in brown rice, but was statistically at par with zinc-enriched urea and Zn-FYM incubated. Although the highest mean benefit: cost ratio of 1.78 was realized at 3 kg Zn/ha, the highest mean net returns of 82.85 × 10³ were realized at 6 kg Zn/ha. Among the sources, the highest and comparable net returns and benefit: cost ratio were realized for Zn-FYM incubated and Zn enriched urea.