Interactive effects of zinc and nickel on growth and nutrition of rice (Oryza sativa L)

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Date
2018
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Punjab Agricultural University, Ludhiana
Abstract
A pot experiment was conducted to study the interactive effects of Zn and Ni on growth and nutrition of rice. The soils used in the study were i) loamy sand (ls) Typic Ustipssament (pH 7.9, EC 0.25 dS m-1, OC 0.15%, CaCO3 0.13%, DTPA-Zn 1.00 and DTPA-Ni 0.19 mg kg-1 soil) and ii) sandy loam (sl) Typic Haplustept (pH 8.1, EC 0.35 dS m-1, OC 0.32%, DTPA-Zn 1.20 and DTPA-Ni 0.46 mg kg-1 soil). Seven levels of Zn (0, 2.5, 5, 10, 20, 40 and 80 mg Zn kg-1 soil) as zinc sulfate heptahydrate and six levels of Ni (0, 2.5, 5, 10, 20 and 40) as nickel chloride were applied in all possible combinations to eight kg of soil per pot with three replications. Rice (cv PR-126) was grown till maturity and soil, root, grain and straw samples were collected. Soil and plant samples were processed and analysed for DTPA-Zn, DTPA-Ni, various pools of Zn and Ni (exchangeable, specifically adsorbed, manganese oxide bound, amorphous Fe and Al oxides bound, crystalline Fe and Al oxides bound, organically bound and residual mineral fraction) and Zn and Ni concentration in root, grain and straw . The activity of urease enzyme in soil was estimated at maximum tillering and harvesting stage. Mean DTPA-Zn in both the soils decreased with increasing levels of applied Ni, while mean DTPA- Ni in both the soils remained unaffected up to a level of Zn application @ 20 mg kg-1 soil, but significant decrease over control was observed with an application of 40 and 80 mg Zn kg-1 soil. The interaction effect of Zn and Ni levels on DTPA-Zn was also significant. It was observed that DTPA-Zn decreased significantly by 45 and 34 per cent when 40 mg Ni kg-1 soil was applied along with 80 mg Zn kg-1 soil as compared to when only 80 mg Zn kg-1 soil was applied in loamy sand and sandy loam soil, respectively. Nickel and Zn application decreased exchangeable and specifically adsorbed Zn in both the soils. However, applied Zn increased Ni in manganese-oxides and amorphous oxides bound pools. The quadratic response of relative root dry matter yield (RRDMY), grain and straw yield to DTPA-Zn indicated that RRDMY, grain and straw yield increased up to level of 5 mg DTPA-Zn kg-1 soil and thereafter it declined in both the soils. The quadratic response of RRDMY to DTPA-Ni in both the soils indicated that maximum RDMY was produced when soil contained 2 mg DTPA-Ni kg-1 soil. However, quadratic response of relative grain and straw yield to DTPA-Ni indicated that grain and straw yield increased up to level of 3 mg DTPA-Ni kg-1 soil and thereafter yield declined in both the soils. Irrespective of the soil used, about 12.0, 16.5 and 14.5 mg DTPA-Zn kg-1 soil and 5.37, 7.45 and 7.10 mg DTPA-Ni kg-1 soil produced 50 per cent reduction from maximum yield of root, grain and straw, respectively, which may be considered as the upper critical values for rice. Irrespective of the soils, the concentration of Ni in root, grain and straw decreased as the concentration of Zn increased. Thus indicating their antagonism with each other. Nickel uptake by each plant part decreased with increase in DTPA-Zn. With increase in level of applied Zn, activity of urease enzyme significantly decreased at both the stages (Maximum tillering and harvesting stage). Application of Ni significantly increased urease activity up to a level of 10 mg Ni kg-1 soil and thereafter it was reduced in both the soils at both the stages. The results also indicated that antagonistic effect of Zn on activity of urease was more pronounced in loamy sand as compared to sandy loam soil. The farmers should apply Zn to the soils only, if the soil test value is below the critical deficiency level to avoid Zn induced Ni deficiency due to build up of Zn in the soils.
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