Rice is a moisture hungry crop and is the single biggest user of fresh water.
Rice is a prolific user of water which required 3000-5000 liters of water to
produce one kg of grain which is almost 2 to 3 times higher than any other cereal
crops such as wheat and maize (IRRI, 2009). Rice is cultivated
under four major ecosystems viz., irrigated (57%), rainfed lowland (31%),
rainfed upland (9%) and deepwater (3%). In India, out of the total available
water for irrigation, 60 per cent is diverted for rice cultivation. The water
supply-demand gap in India is projected to be 25 per cent by the year 2020 (Sunder
et al., 1996). Thus lack of water rather than land may become the
principal constraint to increase food output and to keep the world in peace
With emerging water scarcity in many part of the world, the traditional way
of lowland rice cultivation can no longer be sustained. Along with high water
requirement, traditional system of rice production in long run leads to destruction
of soil aggregates and reduction in macropore volumes (Shashidhar,
2007). Crop growth and yield are the results of metabolic process and as
such variation in yield is to be viewed as the product of variation in the metabolic
processes. Cultural and nutritional management alter the rate of metabolic processes
through modifying the soil plant environment. As root is the absorbing organ,
development of root is evidently an index of the vigour of the above ground
portion also. It has been suggested that upland and aerobic rice are more sensitive
to water stress than other upland crops due to its shallow root system (Angus
et al., 1983).
Therefore, a deep root system is needed for acquiring water and nutrition from
the relatively wet deep soil layer to obtain a stable yield under aerobic conditions.
In this contrast a pot experiment was conducted under poly house condition to
study the impact of integrated package of agrotechniques on rooting behaviour
of aerobic rice.
MATERIALS AND METHODS
Study area: A pot experiment was conducted during July to December, 2011-12
to 2012-13 at Zonal Agricultural Research Station, GKVK, Bengaluru, Karnataka.
The farm is located in the Eastern Dry Zone of Karnataka and is geographically
situated between 12°58 North latitude, 77°35 East longitude
with an altitude of 930 m above the mean sea level. The soil of the experimental
site was red sandy loamy in texture and pH was neutral. The soil was medium
in available nitrogen, phosphorus and potassium. The organic carbon content
was low in range (Table 1).
Weather and crop growth: Rainfall received during the crop growth period
was 487.7 and 406.9 mm in 2011 and 2012, respectively. The rainfall during both
the years of study was less than the normal rainfall. During the year 2011,
the total rainy days during cropping period were 35 and the highest in the month
of August (14). The actual mean sunshine hours were considerably lower during
the entire crop growth period. The open pan evaporation was less than normal
during entire crop growth period (Fig. 1). During kharif 2012,
the rainfall during cropping period was deficit but did not interfere with the
normal crop growth and yield of aerobic rice as it was grown under irrigation.
The total rainy days during growing season were 23 and the highest was in the
month of August (8). The actual mean sunshine hours were considerably lower
during the entire crop growth period. The open pan evaporation was less than
normal during entire crop growth period (Fig. 2).
||Physical and chemical properties of the soil in the experimental
area during Kharif, 2011 and 2012
||Mean monthly weather data during the crop growth period at
ZARS, GKVK and Bengaluru 2011
||Mean monthly weather data during the crop growth period at
ZARS, GKVK and Bengaluru 2012
Treatments details: The experiment was setup in a completely randomized
design repeated thrice. There were ten treatments as follows T1:
Recommended dose of Fertilizers (RDF-100: 50: 50: 20 kg NPK and ZnSO4
ha-1)+Farmyard manure (FYM) at 10 t ha-1+Pyrazosulfuron
ethyl at 25 g a.i. ha-1; T2: RDF+FYM+FeSO4
at 12.5 kg ha-1+Pyrazosulfuron ethyl at 25 g a.i. ha-1;
T3: RDF+FYM+Biofertilizers (Soil application of Azospirillum and
PSB (Bacillus megaterium) at 4 kg ha-1 each mixed with 80
kg of farm yard manure)+Pyrazosulfuron ethyl at 25 g a.i. ha-1; T4:
RDF+FYM+Biofertilizers+FeSO4+Pyrazosulfuron ethyl at 25 g a.i. ha-1;
T5: RDF+FYM+Integrated weed management practices (Pre emergence application
of pyrazosulfuron ethyl at 25 g a.i. ha-1+One hand weeding at 20
days after sowing+First intercultivation at 25 days after sowing and subsequent
intercultivations at 15 days interval upto panicle initiation); T6:
RDF+FYM+FeSO4+Integrated weed management practices; T7:
RDF+FYM+Biofertilizers +Integrated weed management practices; T8:
RDF+FYM+Biofertilizers+FeSO4+Integrated weed management practices;
T9: Site Specific Nutrient Management (SSNM) for targeted yield of
6.5 t ha-1+Integrated weed management practices; T10:
Site Specific Nutrient Management (SSNM) for targeted yield of 7.5 t ha-1+Integrated
Weed Management Practices (IWMP).
Materials used: MAS-26 a popular Semi dwarf, medium duration and deep
rooted aerobic rice variety developed by using Marker Assisted Selection at
University of Agricultural Sciences, Bengaluru was sown in July with a spacing
of 30x30 cm. All the plots were irrigated with a depth of 5 cm immediately after
sowing and subsequent irrigations were given with a depth of 4 cm at 5 days
interval during vegetative growth stage followed by 3 days interval during reproductive
growth stage of the crop farm yard manure was applied at the rate of 10 t ha-1
to each plot three weeks prior to sowing. A common dose of fertilizer was applied
at the rate of 50 kg of N, 50 kg of P, 50 kg of K and 20 kg of ZnSO4
ha-1 as basal dose at the time of sowing in the form of urea, single
super phosphate, muriate of potash and zinc sulphate, respectively. The remaining
50 kg nitrogen was applied in two equal splits each at 30 and 60 days after
sowing in the form of urea to the treatments. Iron as FeSO4 at 12.5
kg ha-1, Azospirillum and PSB (Bacillus megaterium) at 4 kg
each ha-1 mixed with 80 kg of farm yard manure were applied as per
the treatments. In site specific nutrient management for targeted yield of 6.5
t ha-1 130: 32: 162 kg N, P and K ha-1 and for targeted
yield of 7.5 t ha-1 150: 37: 187 kg N, P and K ha-1 was
applied. Pre-emergence application of herbicides was done at three day after
sowing. Irrigation was stopped a week prior to harvest of the crop.
Methods followed to record the observations:
||Plant was uprooted by giving a deep dig near the base after
watering and the maximum root length of the longest root was recorded in
||Total no. of roots:
||Total number of roots per plant at crown region were counted and recorded
||Root dry weight:
||Roots of the plant was cut from the stem, dried moisture free in a hot
air oven at 80°C for 48 h (till attaining constant weight), weighed
and recorded in gram
||Root volume was determined in cc using water displacement
||Root: Shoot ratio:
||The root weight of plant was recorded as mentioned above. The shoot weight
was recorded separately after drying the shoot portion in hot air oven at
80°C for 48 h till reaching constant weight. Then, root: Shoot ratio
was worked out
||Weight of filled grains per hill was recorded in grams after drying
||Weight of straw per hill was recorded in grams after drying
Statistical analysis: The data obtained from pot experiment was analysed
statistically by analysis of variance method for completely randomized design
(Gomez and Gomez, 1984). Critical difference was worked
out at 1% probability level. Correlation studies were made between grain yield
of aerobic rice and root traits. The values of correlation coefficient (r) were
calculated and tested for their significance at 1% (indicated by **) as per
the procedure outlined by Gomez and Gomez (1984). The
response of aerobic rice to integrated package of agrotechniques was similar
in both the years of study. Therefore, only pooled data of two years is discussed.
RESULTS AND DISCUSSION
Root characters: The root characters recorded at panicle initiation
stage and at maturity differed significantly due to integrated package of agrotechniques
(Fig. 3a, b and Table 2,
3). At both the stages the root characters followed the similar
Root length: Application of RDF+FYM+Biofertilizers+FeSO4+Integrated
weed management practices (T8) recorded significantly higher root
length at panicle initiation stage and at maturity as compared to all other
Total No. of roots: At panicle initiation stage application of RDF+FYM+Biofertilizers
+FeSO4+IWMP (T8) significantly recorded more number of
roots per hill as compared to all other treatments. Similar trend was also observed
with total number of roots at maturity stage.
Root volume: Application of RDF+FYM+Pyrazosulfuron ethyl at 25 g a.i.
ha-1 (T5) recorded significantly lower root volume but
RDF+FYM+Biofertilizers+FeSO4+IWMP (T8) recorded significantly
higher root volume followed by RDF+FYM+Biofertilizers+IWMP (T7).
At maturity also, similar trend was noticed.
Root dry weight: At panicle initiation stage, significantly higher root
dry weight was observed with RDF+FYM+Biofertilizers+FeSO4+IWMP (T8)
as compared to that with RDF+FYM+Biofertilizers+IWMP (T7) which inturn
was significantly superior to other treatments.
||Root length, total No. of roots and root volume as influenced
by integrated package of agrotechniques
||Root dry weight, shoot dry weight and root: Shoot ratio as
influenced by integrated package of agrotechniques
|NS: Not significant
It is very interesting to note that root dry weight was very low in the treatments
without IWMP. The root dry weight at maturity also followed the similar trend.
Shoot dry weight: The maximum shoot dry weight was observed with RDF+FYM+Biofertilizers+FeSO4+IWMP
(T8) than with treatments not receiving IWMP and SSNM+IWMP (T9
and T10) and was on par with RDF+Biofertilizers+IWMP (T5).
Similar trend was observed in respect of shoot dry weight at maturity.
Root to shoot ratio: The root to shoot ratio did not differ significantly
at panicle initiation stage and at maturity due to integrated package of agrotechniques.
Yield: Application of RDF+FYM+Biofertilizers+FeSO4+IWM practices
resulted in significantly higher grain yield than SSNM+IWM practices and RDF+FYM+IWM
practices. The lowest grain yield was obtained in RDF+FYM+pyrazosulfuron ethyl
at 25 g a.i. ha-1. Similar trend was also observed with straw yield
Harvest index: The harvest index did not differ significantly due to
integrated package of agrotechniques (Table 4).
||Grain yield, straw yield and harvest index of aerobic rice
as influenced by integrated package of agrotechniques
|NS: Not significant
||Effect of integrated agrotechniques on root growth of aerobic
rice at (a) Panicle initiation stage and (b) Maturity
Application of RDF+FYM+Biofertilizers+FeSO4+IWMP recorded better
root growth traits (Fig. 3a and b) was mainly
due to loosening of soil through repeated intercultivations and hand weeding
encouraged better root aeration by reducing bulk density of the soil and enhancing
the infiltration rate (Shashidhar, 2010; Sunil
et al., 2010). The combined application of Zinc and Fe and biofertilizers
(Azospirillum and Bacillus megaterium) enhanced the N fixation, phytohormone
production, synthesis of phytosedirosphores, increased Zn absorption in plants
and also enhanced the phosphate and iron solubilization by the production of
organic acids by encouraging the growth of microbial population in soil resulted
in better development and proliferation of roots (Ardakani
et al., 2011). Chinnusamy et al. (2006),
Davis and Bayer (1971) helped in better uptake of water,
nutrients by rice inturn recorded higher grain and straw yield per plant. Correlation
studies also revealed significant and positive correlation between grain yield
per plant and root length (0.990**), total number of roots (0.974**), root volume
(0.968**) and root dry weight (0.994).There was a significant and negative correlation
between grain yield and root shoot ratio (-0.948**).
In aerobic rice cultivation well developed root system plays a vital role in
uptake of nutrients and water. Thus, application of RDF, FYM, Biofertilizers
and FeSO4 along with integrated weed management practices is helpful
in getting better development of roots consequently helpful in getting higher
grain and straw yield.
My sincere thanks to Department of Science and Technology, New Delhi, Government
of India for providing me financial support for conducting the research in the
form of Innovation in Science Pursuit for Inspired Research (INSPIRE) Fellowship.