The experiment was conducted at Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar, Gujarat (24°19'N latitude and 72°19'E longitude with an elevation of 154.5 m above the mean sea level) during two consecutive rabi
seasons of 2016-17 and 2017-18. The climate of the region is semi-arid with hot summers and cold winters. The annual rainfall received during first and second crop season was 585 and 2083 mm, respectively.
Experimental design and crop management
The experiment was laid out in a factorial randomized block design consisting of four wheat varieties (GW 273, GW 322, GW 451 and GW 496) and six integrated nutrient management (INM) practices (control, 100% RDF, 100% RDF + Azotobacter
+ PSB, 75% RDF + Azotobacter
+ PSB, 75% RDF + Azotobacter
+ PSB + ZnSO4 and 50% RDF + 25% N through FYM + Azotobacter
+ PSB + ZnSO4
) with three replications. Crop was grown as per recommended practices except the treatments under study. Field was prepared for sowing of crop and furrows were opened at 22.5 cm spacing with tractor. Fertilizer application was done as per the treatments. 100 percent recommended dose of fertilizer (RDF) i.e.
120 kg N: + 60 kg P2O5 per hectare was applied through urea and diammonium (DAP). Full dose of phosphorus and one third dose of nitrogen were applied at sowing and remaining nitrogen was top dressed in two equal splits at first and second irrigations after sowing. Wheat seeds were treated with both Azotobacter
and PSB@ 6g kg–1
of seed or separately either with Azotobacter
or PSB in the concerned treatments. Farm Yard Manure (FYM) (0.5, 0.2 and 0.5 per cent N, P and K, respectively) was broadcasted thoroughly in the respective plots one month before sowing. Zinc sulphate @ 25 kg ha–1
was applied as per treatments. Sowing was done using the seed rate of 120 kg ha–1
November and harvested on 3rd March and 1st
March during 2016-17 and 2017-18, respectively. Total six irrigations in each season were given in crop during both the years of study.
Plant analysis and nutrient uptake
Nitrogen, phosphorus and potassium content in grain and straw were determined by drying the samples in hot-air oven at 60°C±2°C till a constant dry weight obtained. The oven-dried samples were ground to pass through 40 mesh sieve in a Macro-Wiley Mill. Nitrogen was estimated by modified Kjeldhal method, P concentration by Vanado-molybdo-phosphoric yellow colour method and K concentration by flame photometer method as per the procedure described by Jackson (1973)
. Thereafter, the uptake of nutrient was calculated by multiplying concentration with their respective yield.
Soil sampling and analysis
For initial soil parameters, in the year 2016 composite soil sample was collected from 0-15 cm soil depth before preparation of the field and were air dried, ground and passed through 0.2 mm mesh sieve. The textural composition consists of 840 g sand, 75 g silt and 71 g clay kg–1
of soil and soil of the experimental site is classified as loamy sand, typic Ustipsamments. The initial soil had pH 7.4, soil organic carbon 0.24 %, KMnO4
oxidizable N 159 kg ha–1
, 0.5 N NaHCO3
extractable P 38.9 kg ha–1
and 1.0 N NH4
OAc exchangeable K 287 kg ha–1
and DTPA extractable Zn 0.41 mg kg–1
in the top 15 cm soil layer. After field experimentation soil samples were again collected from 0-15 cm depth in each plot and were air dried, ground and passed through 0.2 mm mesh sieve. Organic carbon content in soil samples were determined by Walkley and Black (1934)
method, available N by alkaline potassium permanganate method (Subbiah and Asija, 1956)
, P by Bray and Kurtz No. 1 method (Olsen et al., 1954),
K by ammonium acetate method (Hanway and Heidal, 1952)
. DTPA-extractable Zn was determined using the diethylene triaminepenta acetic acid (DTPA) extraction method (Lindsay and Norvell, 1978)
using atomic absorption spectrometer.
The statistical analysis was performed by using the analysis of variance (ANOVA). Least significant differences (LSD 0.05) provided detailed information about the differences among treatment means.