Department of Soil Science and Water Management, Dr. YS Parmar University of Horticulture and Forestry, Nauni, Solan, Himachal Pradesh, 173 230.
Zinc transformation in apple orchards at-four different crop growth stages was studied. Also, critical levels at zinc deficiency in plants were established. The native WS + exchangeable, organically bound, acid soluble, CBD-extractable and DTPA-extractable Zn fractions registered a continuous decrease during all the four crop growth stages studied. However, complexed Zn fraction showed an increase till fruit development and exhibited decline thereafter. The amount of applied Zn transformed into various fractions between fruit set to fruit development stage followed the order: WS + exch. (4.0%) < CBD-extractable (7.7%) < complexed (9.2%) < organically bound (11.4%) < acid soluble (13.4%). The DTPA extractable Zn, however, retained 9.4% of the applied Zn. After leaf fall, the Zn accumulated in different fractions decreased to the extent of 3.6, 7.3, 8.6, 9.4, 13.2 and 9.2 per cent in WS + exch., CBD extractable, complexed, organically bound, acid soluble and DTPA extractable Zn forms, respectively. Critical range of 16.0–20.0 ppm Zn was established for plants in these apple orchards.
Zn transformation, Zn fractions, critical range, apple orchards, Himachal Pradesh
