Rate and Frequency of Fertilizer Zinc Application on Zn Fractions in Inceptisols of Gujarat, India

Abstract

A six year study (2012-18) was carried out to assess the effect of different application rate and frequencies
of zinc (Zn) fertilizer on different forms of Zn in the Inceptisols of Gujarat, India in a maize–wheat
cropping system. The efficiency of applied Zn was evaluated in combinations of four different rates (2.5,
5.0, 7.5 and 10.0 kg Zn ha-1) and at three different frequencies (first year only, alternate year and every
year). Additionally, one Zn control plot which received only the recommended dose of fertilizers (RDF)
was also included. The experiment was designed in a randomized block design with three replications. A
sequential extraction method was adopted to fractionate water-soluble Zn (WS-Zn), exchangeable Zn (EXZn),
Zn bound to carbonate (Car-Zn), Zn bound to iron (Fe) and manganese (Mn)-oxide (FeO/MnO-Zn),
Zn bound to organic matter (OM-Zn), residual Zn (Res-Zn) and total soil Zn forms. The results showed that
the continuous application of Zn for six years increased concentrations of all soil Zn fractions irrespective
of Zn application rate and frequencies. Increasing Zn input increased the percentages of Ex-Zn, Carb-Zn,
FeO/MnO-Zn and to soil total Zn, whereas reduced the OM-Zn and Res-Zn fraction. Apparent Zn recovery
efficiency varied with the application rates from 1.46% in 2.5 kg Zn ha-1 applied every year to 0.17% in 10
kg Zn ha-1 applied during first year of study in maize crop and from 1.70% in 2.5 kg Zn ha-1 applied every
year to 0.34% in 10 kg Zn ha-1 applied in the first year only for the wheat crop. Overall the use efficiency
of Zn decreased with increased the rate of Zn application and its frequencies.