RICE CULTIVAR (Oryza sativa L.)

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Rifnas, L. M. and Mahendran, S.

Department of Agricultural Biology,

Faculty of Agriculture, Eastern University, Sri  Lanka.



Excessive and improper usage of chemical fertilizers on rice leads to adverse effects on human and environment. It has become necessary for a suitable alternative source of fertilizer as bio-fertilizer, containing beneficial microorganisms to replace or reduce the chemical fertilizer usage. An experiment was conducted in the Rice Research Station, Sammanthurai, Sri Lanka during the ‘Yala’ 2017 to evaluate the possibility of replacing chemical fertilizers with bio-fertilizer.  This experiment was laid out in the Randomized Complete Block Design and consisted of five replications and four replications. The treatments were T1-No fertilizer (Control), T2- 100% recommended dose of chemical fertilizer, T3-50% chemical fertilizer + 50% bio-fertilizer, T4-50% bio-fertilizer, T5-100% bio-fertilizer. ‘Gro Bio-fertilizer’ consisted of Azotobacter chrococcum, Azospirillum brasiliensis, Bacillus polimixia, Bacillus megaterium and other Bacillus spp. in s liquid base medium used as the bio-fertilizer source.

Rice cultivar ‘Bg 250’ was evaluated for selected parameters such as plant dry weight, chlorophylls a and b, flag leaf length and yield. Combined application of chemical and bio-fertilizer showed the highest performance in plant dry weight (3.3g), chlorophylls a (1.7mgg-1), b (1.4mgg-1), flag leaf length (80.1cm) and yield (2.5tonnesha-1). Hence it could be stated that 50% biofertilizer combined with 50% chemical fertilizer could be used as an alternative source in the production of rice with reduced hazardous effects on the environment.


As per the Food and Agricultural
Organization (2014), world`s total agricultural land area of 4.9 billion hectares is nearly 38% of the world’s total land area. Asia contributes to almost 90% of the world’s rice production. China, India, Vietnam, Burma, Indonesia, Bangladesh and Sri Lanka are the major rice producing countries in Asia.

In terms of food, area and production rice is grown in wide range of climatic zones of the world to nourish mankind (Chaturvedi, 2005). It is an important staple food that provide 60-70% body calorie intake of the consumers (Barah and Pandey, 2005). Improved rice varieties and judicious application of fertilizers are the two most effective means to maximize rice production (Islam et al., 2009). With
the increase in rice production, application and need of the chemical fertilizers is also
increasing simultaneously as it can give more reliable supportive boosts  to increment of crop yield (Saikia et al., 2012).

National fertilizer secretariat (2013) has indicated that around 600,000 tonnes of solid fertilizers and 250,000 tonnes of liquid fertilizers are imported to Sri Lanka annually. Relatively large amounts of Urea, TSP and MOP compared to other fertilizers are imported annually. More amount of fertilizer was used to obtain more products and most of the farmers prefer to get quick return and they use chemical fertilizers and pesticides. Excessive use of these chemical compounds in agriculture result in a large number of environmental problems (Janagrad et al., 2009).

Bio-fertilizers play a very significant role in improving soil fertility by fixing atmospheric nitrogen both in association with plant roots and without it, solubilize
insoluble soil phosphates and produces plant growth substances in the soil. They
improve soil properties and agricultural production (Yosefi et al., 2011). It also includes organic fertilizers like manure etc. which are rendered in an available form due to the interaction of microorganisms or due to their association with plants (Sujanya and Chandra, 2011).

Bio-fertilizers by overall produced higher growth rates and yield development of rice production compared with chemical fertilizers (Alam and Seth, 2014). Therefore, bio-fertilizers can solve the problem of feeding an increasing global population at a time when agriculture is facing various environmental stresses and changes.


30cm height and 40cm diameter plastic pots were filled soil taken from rice lands of the Rice Research station, Sammanthurai. Rice seeds were soaked in water for 24 hours  and were incubated for 48 hours by a  wrapping cloth. Nicely sprouted seeds were transferred to seedling trays. Healthy and uniform seedlings (12 days old) were transplanted in already prepared plastics pots. Chemical fertilizers (Urea-225 kgha-1), TSP-55 kgha-1 and MOP-60 kgha-1)  were applied in three split doses and bio-fertilizer (500mlha-1) was applied in two split doses.

Preparation of bio-fertilizer

‘GRO BIO-FERTILIZER’ was mixed at the rate of 500mlha-1 with 10kg of cow dung, 5 litres cow urine and 10 litres of water. It was kept under shade for three days for incubation.

Application of bio-fertilizer

Bio-fertilizer was applied during the late evening. First application was done two days after transplanting and second one was at the booting stage.

Treatments were as follows,

T1-No fertilizers (Control)

T2-100% chemical fertilizer (Urea-225kgha-1,TSP-55kgha-1,MOP-60kgha-1)

T3- 50% chemical fertilizer + 50% bio-fertilizer (Urea-113kgha-1, TSP-28kgha-1, MOP-30kgha-1 + 50% of bio-fertilizer 250mlha-1)

T4- 50% of bio-fertilizer only (250mlha-1)

T5- 100% bio-fertilizer (500mlha-1)

Plant dry weight – A number of five plants plants were cut into small pieces.These cut pieces were then oven dried at 800 C for 48 hours and the oven dry weights (g) were determined.
Flag leaf length – A number of five plants were randomly selected from each replicate of the treatments and the length of their flag leaves was measured in cm from the soil surface to the apex of the flag leaf

Chlorophylls a and b determination

The amount of chlorophyll present in rice leaves was estimated according to smith and Benitez (1955). The chlorophyll contents (chlorophylls a and b) of rice leaves were determined at the late vegetative stage. Five plants were randomly selected from each replicate of the treatments. A quantity of 500 mg of
fresh leaf sample from the third leaf of each replication and leaf samples were ground to fine pulp with a motar and pestle using a quantity of 10 ml of 80% acetone. The ground fine pulp was centrifuged at 5000 rpm for 10 minutes using Heraeus Pico 17 microcentrifuge. The supernatant was collected and the remaining portion of the leaf pulp was again ground by using 10ml of 80% acetone and centrifuged until the supernatant became colourless. The final volume of the supernatant was measured. The absorbance was read at 663and 645nm against the solvent blank (80% acetone) using 10 mm cuvettes by using BK-V1600 VIS Spectrophotometer. The amount of chlorophyll present in the extract was
calculated on the basis of milligrams of chlorophyll present in a gram of leaf tissue
sample using the following equations:

mg ‘chlorophyll a’ present / g sample=

mg ‘chlorophyll b’ present / g sample =
                         1000 x W


OD: Optical density reading

V: Final supernatant volume (ml)

W: Fresh weight of the plant sample (g)


Yield – A number of five plants were randomly selected from each replicate of the treatments. The seeds were collected from these plants and were sun dried and the yield was determined.

Statistical Analysis

The data were statistically analyzed using analysis of variance t determine the significance if any at the treatment level. The difference between treatment means were compared using DMRT.


It was found that there were significant (p0.05) differences in the dry weights of plants treated with 50% chemical and 50% bio-fertilizer combination and 100% chemical fertilizer (Table 01). The application of 50% chemical and 50% bio-fertilizer will be a better way to increase the dry weights of rice plants.

According to Dar and Bali (2007) the biomass increased progressively irrespective of treatments over control. However, the total fresh biomass production of rice has given the highest value with combined application of bio-fertilizer and chemical fertilizer than single application of biofertilizer. Mathews et al. (2005) showed that combined application of nutrients- NPK and bio-fertilizers has caused significant variation in the total dry matter production over control

Chlorophylls a and b

The highest amount of chlorophylls a and b were recorded in the combined application of 50% chemical and 50% bio-fertilizer treatment followed by 100% chemical fertilizer treatment. The lowest amount of chlorophyll contents was recorded in the treatment where no fertilizers were added.

Rajasekaran and Sundaramoorthy (2015) have indicated that the highest contents of
chlorophyll a and b, total chlorophyll and carotenoids were recorded in rice grown in soil treated with Azospirillum and Bacillus. The lowest contents of chlorophylls a and b, total chlorophyll and carotenoids were recorded in rice grown without any fertilizers Studies by El-Sobky and Desoky (2016) were on par with this study of inoculation with bio-fertilizer Anabaena through soil in addition to spraying has increased the chlorophylls a and b, total chlorophyll and carotenoid contents in rice leaves compared to no bio-fertilizer addition.

Table 01 : Effects of chemical and bio-fertilizer application on plant dry weight and chlorophylls a and b.


Plant dry weight (g)

Chlorophyll a (mgg-1)

Chlorophyll b (mgg-1)





















Values with the same letter within the same column are not significant (p0.05) difference in the flag-leaf length of rice plants treated with 50% bio-fertilizer and 50% chemical fertilizer and 100% chemical fertilizer. The lowest flag-leaf length was observed in plants where no fertilizers were added (Control treatment).

Firouzi (2015) has indicated that there were significant (p0.05) difference in the yields of rice plants treated with 100% chemical fertilizer and 100% bio-fertilizer. Hence, it could be stated that chemical and bio-fertilizers has increased the yield of rice plants.

Studies of Singh et al. (2015) were on par with this study. They have showed that grain yield of rice was significantly (p

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