Excessive present study was conducted with the objectives of

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, Department of Agriculture, Sammanthurai, Sri Lanka during the ‘Yala’ 2017 to assess the growth performance of rice cultivar ‘Bg 250’ with chemical and bio-fertilizer. This experiment was laid out in the Randomized Complete Block Design with five treatments 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. The trade name ‘Gro Bio-fertilizer’ consisted of Azotobacter chrococcum, Azospirillum brasiliensis, Bacillus polimixia, Bacillus megaterium and other Bacillus spp. in liquid base medium used as the bio-fertilizer. It was mixed at the rate of 500mlha-1 with cow dung (10kg), cow urine (5L) and water (10L) and allowed for three days under shade. Rice cultivar ‘Bg 250’ was evaluated for selected growth attributes such as plant dry weight, chlorophylls a and b contents, flag leaf length and yield. Combined application of chemical (50%) and bio-fertilizer (50%) showed the highest in plant dry weight (3.3g), chlorophylls a(1.7mgg-1) and b (1.4mgg-1), flag leaf length (80.1cm) and yield (2.5tha-1). Control treatment where no fertilizers were added showed the lowest values. Based on the results it was found that the combined application of 50% chemical and 50% bio-fertilizer showed the highest growth and yield in ‘Bg 250’ rice cultivar.  Hence, it could be stated that 50% bio-fertilizer in combination with 50% chemical fertilizer could be an alternative means in the production of rice with reduced ill effects on human and environment.

Keywords: Bio-fertilizer, Chlorophyll content, Flag leaf length, Plant dry weight, Yield

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INTRODUCTION

Chemical fertilizers are used extensively in modern agriculture to improve crop yield. However, nutrient leaching from agricultural soil into ground water and surface water causes a major environmental and public health concern. Nitrate and phosphate concentrations are found to be higher than the permissible limits of World Health Organization standards due to leaching and surface runoff of chemical fertilizers from agricultural lands (Divya and Belagali, 2012).

Bio-fertilizers keep the soil environment rich in all kinds of micro and macro nutrients via nitrogen fixation, phosphate and potassium solubilization or mineralization, release of plant growth regulating substances, production of antibiotics and biodegradation of organic matter in the soil (Sinha et al., 2010).

Rice (Oryza sativa L.) is one of the main and most important cereal crops of many countries of the world such as Asia, Africa, South America and Australia. Rice is the staple food for about 50% of world population in Asia. 90% of the world’s rice is grown and consumed in Asia. Bio-fertilizers by overall produce higher growth rates and yield of rice compared with chemical fertilizers. 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.

Hence, the present study was conducted with the objectives of determining the effects of chemical and bio-fertilizers on plant dry weight, chlorophylls a and b contents, flag leaf length and yield of rice cultivar ‘Bg 250’, to compare the growth and yield of this rice cultivar with the application of chemical and bio-fertilizers and to find out the most suitable fertilizer/s to obtain optimum growth and yield of ‘Bg 250’.

MATERIALS AND METHODS

Rice seeds were water soaked and incubated and the sprouted seeds were transferred to seedling trays. Healthy and uniform seedlings (12 days old) were transplanted in sand filled plastics pots (12 plants/pot) having the height (30cm) and diameter (40cm). The seedlings were watered regularly and the water level was maintained to the top of the pot. The experiment was laid out in the Randomized Complete Block Design with five treatments and four replications.

 

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

T4 – 50% bio-fertilizer (250mlha-1)

T5 – 100% bio-fertilizer (500mlha-1)

The fertilizers were applied based on the treatments. Chemical fertilizers and bio-fertilizers were used for this study. Chemical fertilizer (Urea-225 kgha-1, TSP-55 kgha-1 and MOP-60 kgha-1) was applied in three split doses and bio-fertilizer (500 mlha-1) was applied in two split doses (One at two days after transplanting and another at booting stage). Bio-fertilizer was prepared by mixing the culture (Gro Bio-fertilizer) with cow dung (10kg), cow urine (5 litres) and water (10 litres). This set up was incubated for three days under shade. Bio-fertilizer was applied during late in the evening.

A number of three plants were randomly selected from each replicate of the treatments for growth measurements. The plants were uprooted and were washed with tap water and their dry weights were recorded at 80OC for 2 days. The chlorophyll content of rice leaves was estimated according to Smith and Benitez (1955). The length of flag leaf was measured in cm from the base to the apex. A number of three plants were randomly selected from each replicate of the treatments at the time of harvest and the seeds were collected, sun dried and the yield was determined. The data were statistically analyzed and the difference between treatment means was compared using DMRT.

RESULTS AND DISCUSSION

There were significant (p