Evaluation of Zinc Supplying Power of Soils for Rice
1985
Misra, A.K. | Nayar, P.K. | Patnaik, S.
Laboratory incubation and short term pot experiments were conducted with 51 soils, to study the effect of flooding on Zn as extracted by NH₄O fi Ac-dilhizone, 0.1 N HCl, 0.05 N HCl, DTP A and EDTA and their relationship with Zn content and uptake by rice grown in these soils. The rice plant, after 35 days of transplanting in these soils, contained 18 ppm or more of Zn, which was considered adequate, since foliar symptoms of Zn deficiency were not observed. Zinc extracted from dry and flooded soils by all the reagents was significantly correlated with plant Zn content and uptake, except in three situations. The soils of higher pH had lower content of extract -able Zn. Flooding, in general resulted in decrease in extractable Zn, such reductions being more in soils with lower initial pH. It is, desirable to use dry soil for extracting Zn with dithizone, since some soils under flooded conditions gave values lower than the reported critical limits, without any reflection on plant growth. The dithizone-Zn in soil was significantly correlated with Zn extracted with the other four reagents. Since the dithizone method is cumbersome, time and labour consuming, it is suggested to determine Zn in soil by extraction with DTP A, 0.1 N HCl or 0.05 N HCl taking into consideration the soil pH, CaCO₃ content, etc., and use of regression equation to compute dithizone-Zn, in any programme of evaluation of Zn supplying power of soils.
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