Abstract:
Use of saline water for irrigation has shown considerable promise. However, its effect
on the solubility and bioavailability of native soil nutrients is not well understood. This
study was conducted to evaluate the effects of salinity on the behavior of zinc(Zn) in
calcareous soils. The soil samples with different physiochemical properties were collected
from four locations in Khorasan province (Iran). The factorial experiment was carried
out as a completely randomized design on soils with four levels of water salinity (0, 37.5,
75 and 150 mole m-3 prepared with the same equivalents of NaCl and CaCl2) and four
reaction times (0, 10, 20, and 30 days) with three replications. DTPA-extractable Zn was
measured in the incubated soil samples after the given reaction times. Different chemical
forms of Zn were characterized after 30 days using the sequential extraction procedure.
DTPA-extractable Zn increased by 1 to 6.3% with the increasing levels of salinity, and
decreased from 8.7 to 3.9% by increasing the reaction time significantly (P<0.05). The
determination of Zn compounds by the sequential extraction procedure revealed
significantly different forms of Zn with the average amounts in the following order:
(KNO3+H2O)-Zn(soluble+exchangeable forms) < NaOH-Zn(organic form) < EDTA-Zn
(carbonate form) << HNO3 -Zn (residual). Salinity affected various forms of Zn i.e.
soluble + exchangeable, organic and residual. Increasing soil salinity level increased the
KNO3+H2O extractable Zn by 20 to 80% and the NaOH extractable form by 8.6 to 43%.
DTPA-Zn was significantly correlated with the NaOH extractable form (r=0.98 P<0.05)
and with the (KNO3+H2O)-Zn, (r=0.94 P<0.05). It was concluded that increasing salinity
redistributed HNO3-extracted Zn (residual) to the KNO3+H2O extractable (soluble +
exchangeable) and NaOH extractable (organic) forms of Zn.
