Evaluation of Zinc Supplying Power of Soils for Rice

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.