Effect of zinc fertilization on zinc transformation in upland rice under rice wheat cropping system in calcareous soil

1.  Pankaj Kumar Keshari
 M. Sc. Student (Soil
Science)
 (Reg. No. M/SS/151/14-15)
Rajendra Agricultural University, Bihar, Pusa, Samastipur
Major Advisor
Dr. Ranjan Laik
Sr. Scientist (Soil Science)

2.  Calcareous soil and extent of Zn deficiency
◦ Area of calcareous soil in India and Bihar
 Reasons for low Zn availability – high CaCO3
content, high pH, low organic matter content,
high application of phosphatic fertilizer, light
texture
 Upland calcareous soil - potentially zinc deficient
 Low Zn use efficiency in calcareous soil
 Applied Zn is converted into different reaction
products
 Need for determining dose and frequency of Zn
fertilization

3. After completion of three years of zinc
applications in different doses and different
modes under rice – wheat cropping system,
the objectives of the present investigation are
to study:
 Rice yield, growth attributes and zinc uptake
 Soil available zinc status and
 Dynamics of different forms of zinc

4.  Solubility of soil Zn is highly pH dependent-
each unit increase in pH decreases 100 fold
Zn availability (Tisdale et al., 1985)
 Available Zn status and critical limit of Zn in
different soil associations of Bihar (Sakal et
al., 1974-84) and also in crops
 Amelioration of Zn deficiencies (Sakal et al.,
1983)
 Forms of Zn (Sakal et al.1983, Wei et al.,
2005) – soluble and exchangeable, bound to
organic matter, carbonate and Mn

5.  Year of inception: 2012-13
 Cropping system: Rice-Wheat
 No. of treatments: 13
◦ 4 doses (2.5, 5.0, 7.5, 10 kg ha-1)
◦ 3 modes (every year, alternate year, first year only)
◦ Control
 Replication: 3
 Design: RBD
 Plot size: 5 x 2 m = 10m2
 No. of plot: 39

6.  Grain & straw yield
 Root weight
 Shoot weight
 No. of tillers/m2
 No. of productive tillers/m2
 No. of grain/panicle
 Test weight
 Agronomic efficiency: (Grain yield of Zn-fertilized
pots − Grain yield of Zn-unfertilized plots
(Quantity of Zn applied)
Agronomical Observations
X
100

7.  N, P, K concentration in root, shoot and grain
 Zn, Mn, Fe and Cu concentration in root, shoot
and grain
 Zn uptake by crop: Zn concentration x dry
matter yield (grain and straw)
 Apparent Zn recovery efficiency
 = (Zn uptake fertilized – Zn uptake control) / Zn applied

8.  pH & EC
 Organic carbon (OC)
 Inorganic carbon (CaCO3)
 Available phosphorus, potassium, and
sulphur
 Available zinc, iron, manganese and copper
 Zinc fractions (Exchangeable Zn, Weakly
bound zinc to organic matter, Carbonate
bound Zn, Manganese oxide bond zinc and
Strongly bound to organic matter )
Soil Chemical Properties
Initial and Final Soil Samples will analyzed for following
chemical properties

9. Analysis of initial soil samples
 pH of soil:1:2 soil : water suspension, measured
with digital pH meter (Jackson, 1973)
 EC of soil:1:2 soil : water suspension, measured
with digital EC meter
 Organic carbon(OC):Walkley and Black wet
digestion method (Walkley and Black, 1934)
 Inorganic CaCO3: The calcium carbonate (CaCO3)
equivalent will be determined by neutralizing it
with hydrochloric acid (HCl) and back titration
with sodium hydroxide (NaOH) (Black et al.,1965)

10. Available nutrient
 Phosphorous : Olsen's method (Olsen et al., 1954)
 Potassium : Ammonium acetate method (Chapman and
Pratt1961.,)
 Sulphur : Available S was measured using 0.15%calcium
chloride (CaCl2) as an extractant (Tabatabai., 1996)
 Available Zn,Fe,Mn,Cu : Chelate-exctractable Zn,Fe,Mn and Cu
will exrtract by using dietylenetriaminepentaaceticacid (DTPA
Lindsay et al., 1978) and determined by using atomic
absorption spectrophotometry(AAS)
 Zinc fractions : (Exchangeable Zn, Weakly bound zinc to
organic matter, Carbonate bound Zn Manganese oxide bound
zinc and strongly bound zinc to organic matter( Wei et al.,
2005)

11. Zinc fractions
(A)Exchangeable Zn: 25 ml 1 mol L–1 Mg(NO3)2 (Mg
nitrate)(pH at 7.0) + 2.5 g of air-dry soil
Shaken for 2 h at 25°C
Centrifuged and supernatant decanted
Residual soil washed with 20 ml of DI water and WS
Exchangeable Zn determined
Water discarded and residual soil kept for next step

12. (B) Weakly bound zinc to organic matter(Wbo-Zn): 25ml
0.l mol L–1 Na4P2O7 (Sodium Pyrophosphate) ( pH 9.5)
added to the residual soil
Shaken after 2 h at 25°C
Centrifuged and supernatant decanted
Residual soil washed with 20 ml of DI water
Bounded Zn to OM determined
Water discarded and residual soil kept for next step

13. (C) Carbonate bound Zn (Carb-Zn): 25 ml 1 mol L–1
(Sodium acetate-acetic acid)NaoAc–HOAc ( pH 5.0) added
to the residual soil
Shaken for 2 h at 25 0c
Centrifuged and the supernatant decanted
Residual soil was washed with DI water
Determined carbonate bound-Zn
Water discarded and residual soil kept for next step

14. (D) Manganese oxide bound Zn (MnO-Zn): 25 ml 0.l
mol L–1 NH2OH-HCl (Hydroxyl Amine-Hydrochloric Acid)
(pH 7.0) added to the residual soil
Shaken for 30 min at 25°C.
Centrifuged and the supernatant decanted
Residual soil was washed with DI water
Determined Mno bound-Zn
Water discarded and residual soil kept for next
step

15. (E) Zinc strongly bound to organic matter (Sbo-Zn):
5ml 30% H2O2 (pH 2) added to the residual,
Mixtures digested in an 80°C water bath for 2 h until
near dryness
Add 25 ml of 1 mol L–1 Mg(NO3)2 at pH 7.0
Shaken for 2 h at 25°C
Sentrifuged and the supernatant decanted
Determine Zn srongly bounded to organic matter