Abstract: In a field experiment, comparative effect of three different methods of zinc application was studied, aimed at alleviating Zn deficiency in transplanted flood rice (cv.IRRI.6) grown in alkaline calcareous soil. Three methods were tried i.e. nursery root dipping in 1.0% ZnSO4, 0.20% ZnSO4 solution spray after transplanting and 10 kg Zn ha-1 by field broad cast method. Zinc content of soil before flowering and after harvest was increased significantly for all the methods. The yield and yield parameters increased significantly by the application of Zn by any method. Among the methods the effect of Zn was non-significant on yield components like tillers m-2, spikelets panicle-1, % filled grains, 1000-grain weight and straw yield. However, soil application of Zn @ 10 kg ha-1 was rated superior because it produced significantly higher paddy yield.
Introduction
Micronutrient deficiencies are known in Pakistan since more than two decades (Yoshida and Tanaka, 1969; Rashid and Qayyum, 1990). Rice being grown under submergence is strongly affected with micronutrient deficiency particularly with that of Zn (Tahir, 1978; Yoshida and Tanaka, 1969). Due to clayey, alkaline and calcareous nature of soils in Pakistan, fertilizer zinc is mainly adsorbed by soil and very little is available and recovered by plants (Tahir et al., 1991). Zinc being an expensive fertilizer, must, therefore be applied in such a way that may enhance its availability as well as efficiency in soils. Broadcast and top dressing of Zn along with ZnO coating of seedling root and foliar spray in rice have been found effective methods in earlier investigation (Yoshida et al., 1970). Dipping the seedlings in 2% ZnSO4 or 25 kg Zn ha-1 as basal dressing or spraying 0.5% ZnSO4 solution once or twice to the transplanted crop proved equally effective (Kumar et al., 1996). The application of ZnSO4 and ZnO have been reported better than fritz for rice and barley production while in light soil, ZnSO4 was better than ZnO for wheat production (Ketyal, 1981). The use of seed bed application of Zn @ 20 kg Zn ha-1 in field and green house experiment was proved equally effective or superior to the conventional ZnSO4 broad cast method (Rashid et al., 2000).
This study was carried out to evaluate the comparative value of three different technologies for managing zinc deficiency in transplanted flooded rice grown in alkaline calcareous soil.
Materials and Methods
A field experiment was conducted at the research area of Faculty of Agriculture, Gomal University D.I.Khan. Thirty days old nursery of a rice variety IRRI-6 was transplanted in standing water. The Randomized Complete Block Design (RCBD) was used with three replication and a plot size of 2 x 5m. Row to row and plant to plant distance was maintained at 20 cm. Following experimental treatments were applied.
| Table 1: | Physico-chemical characteristics of soil |
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Half of the nitrogen as urea and whole of phosphorous as TSP and potassium as K2SO4 was incorporated before transplanting while remaining N was used at panicle emergence. Physical and chemical characteristics of composite soil samples taken from experimental field were determined according to the methods as described in Methods of Soil Analysis by Page et al. (1982). DTPA was used to extract available Zn in soil, which was subsequently determined by atomic absorption spectrophotometer. Crop was harvested at maturity and yield parameter was recorded. Paddy yield was calculated at the 14% moisture content. Statistical analysis of all the data was done using Fisher Analysis of Variance Technique and least significant difference test was applied at 5% probability level to determine the difference among treatment means (Steel and Torrie, 1984).
Results and Discussion
Plant height
The data for the plant height of rice as affected by different methods of
Zn applications are reported in Table 2. The results showed
that application of zinc fertilizer by different methods, increased significantly
the height of plants over control. The maximum plant height of 101.0 cm was
recorded from the treatment receiving 10 kg Zn ha-1 by soil Zn application
which did not differ significantly from that of foliar spray receiving 0.20%
ZnSO4 but differed significantly from that of root dipping receiving
1.0% ZnSO4 solution. Minimum plant height was recorded in control.
Among the methods of zinc application, significantly the maximum plant height
of 101.0 cm was obtained with soil dressing which clearly indicated the beneficial
effect of soil application of Zn as compared to other methods. Maqsood et
al. (1999) also reported similar results.
Number of tiller m-2
The data regarding the number of tillers m-2 presented
in Table 2 indicated that the zinc applied by different methods
significantly increased the number of tillers m-2 over control but
were statistically at par with one another. Maximum number of 415.67 tillers
m-2 was recorded where zinc was applied @ 10 kg ha-1 by
soil dressing followed by that of 1.0% ZnSO4 by root dipping and
0.2% ZnSO4 by foliar spray. Minimum number of 380.33 tiller m-2
was recorded in control. As regards the methods of zinc application, all were
statistically similar. The increase in tillering capacity by soil dressing might
be due to increase in availability of essential nutrients as compared to other
methods. Savithri et al. (1999) and Yaseen et al. (1999) reported
similar results.
Number of panicle m-2
The data given in Table 2 manifested that the variation
in the number of panicle as affected by various methods of Zn application was
significant. The results showed that all the methods of zinc application increased
the number of panicle m-2 as compared to control. Maximum number
of 355.67 panicles m-2 was recorded in plots receiving 10 kg Zn ha-1
by soil dressing which was statistically different from the plots receiving
1.0% ZnSO4 by root dipping and that receiving 0.20% ZnSO4
by foliar spray. The lowest number of 330 panicles m-2 was recorded
in control which differed significantly from all other treated plots. The maximum
number of panicle m-2 obtained soil dressing showed the superiority
of this method under D.I.Khan conditions. These results are in agreement with
those of Savithri et al. (1999) and Yaseen et al. (1999).
| Table 2: | Effect of Zn on the yield components of rice |
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| Mean values with the same letters are non-significant at p≤0.05 | |
| Table 3: | Effect of Zn on 1000-paddy weight, paddy and straw yield and extractable Zn of soil |
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| Mean values with the same letters are non-significant at p≤0.05 | |
Number of spikelet panicle-1
The results regarding number of spikelets panicle-1 (Table
2) manifested that the variation among the various methods was non-significant
while zinc fertilization by all the three methods increased the number of spikelets
panicle-1 significantly over control. The maximum number of 131.33
spikelets panicle-1 was recorded where zinc was applied @ 10 kg Zn
ha-1 by soil dressing followed by that of 1.0% ZnSO4 by
root dipping and 0.2% ZnSO4 by foliar spray. The lowest number of
115.33 spikelet panicle-1 was recorded in control. Somewhat similar
trend has been found in the findings of Hernadez et al. (1988).
Percent filled grains
The data for percent filled grains as affected by zinc levels applied by
different methods presented in Table 2 indicated that zinc
fertilization by all the three methods increased the number of percent filled
grains significantly over control. The maximum value of 84.5% filled grains
was recorded where zinc was applied @ 10 kg Zn ha-1 by soil dressing
followed by that of 1.0% ZnSO4 by root dipping and 0.2% ZnSO4
by foliar spray. The lowest value of 80.2% filled grains was recorded in control.
As regards methods of zinc application, all were statistically at par with one
another. Somewhat similar trend has been found in the findings of Hernadez et
al. (1988) and Jalil et al. (1990).
1000-paddy weight
The data shown in the Table 3 indicated that the effect
of Zn applied by different methods on 1000-paddy weight was significant as compared
to control. Maximum 1000-paddy weight of 24.8 g was recorded where zinc was
applied @ 10 kg Zn ha-1 by soil dressing followed by that of 1.0%
ZnSO4 by root dipping and 0.2% ZnSO4 by foliar spray.
Minimum 1000-paddy weight of 20.19 g was recorded in control. However, there
was no significant difference among the methods of Zn application. These results
are in agreement with those of Yaseen et al. (1999).
Straw yield (tones ha-1)
The data on the straw yield reported in Table 3 showed
that the Zn application by different methods significantly increased the straw
yield over control. However, all the methods were statistically at par to one
another. The highest straw yield of 12.480 tones ha-1 was recorded
in the treatment receiving 10 kg Zn ha-1 by soil dressing followed
by that of 0.2% ZnSO4 by foliar spray and 1.0% ZnSO4 by
root dipping. The lowest straw yield of 12.335 tone ha-1 was recorded
in control. Similar results were reported by Yaseen et al. (1999).
Paddy yield (tones ha-1)
The data on the paddy yield as presented in Table 3 indicated
that the maximum paddy yield of 9.762 t ha-1 was recorded in plots
receiving 10 kg Zn ha-1 by soil dressing which was significantly
higher than the plots treated with 1.0% ZnSO4 by root dipping and
0.2% ZnSO4 through foliar spray. The increase in paddy yield by soil
dressing method was probably attributed to its more effectiveness under conditions
of D.I.Khan. Minimum yield of 6.116 tone ha-1 was recorded in control,
which was due to the non-availability of zinc. Similar results were reported
by Shamim et al. (1991) who reported greater grain yield with soil application
of Zn than foliar application. Kumar et al. (1997) and Savithri et
al. (1999) also reported somewhat similar results.
Zinc content of soil before flowering
Data on zinc content of soil before flowering as influenced by different
methods of Zn application (Table 3) revealed that the response
to different methods was significant. The highest soil zinc content of 0.84
ppm was recorded in plots treated with 10 kg Zn ha-1 to soil which
was statistically at par with the plots treated with 1.0% ZnSO4 by
root dipping but significantly higher than that of 0.20% ZnSO4 by
foliar spray. It showed that soil Zn application increased the soil Zn availability
than other methods. The lowest zinc content of 0.42 ppm was recorded in plots
where no zinc fertilization was done. All the zinc fertilization applied by
different methods increased the soil zinc content over control significantly.
Similar results were reported by Ram et al. (1995).
Zinc content of soil after harvest
The data in Table 3 indicated that response to different
method was significant. Maximum soil Zn content of 0.74 ppm was recorded in
plots treated with 10 kg Zn ha-1 to soil which was statistically
at par with the plots treated with 1.0% ZnSO4 by root dipping but
significantly higher than that of 0,20% ZnSO4 by foliar spray. It
showed that soil Zn application increased the soil Zn availability more than
other methods. The lowest Zn content of 0.30 ppm was noted in control. However,
the Zn content in the soil was reduced at harvest. Similar result was reported
by Ram et al. (1995) and Asad and Rafique (2000).