Ph.D. Research Scholar, Department of Genetics and Plant Breeding, CCS Haryana Agricultural University, Hisar, Haryana-125 001
Increasing use of chemical fertilizers in agriculture make country self dependent in food production but it deteriorate environment and cause harmful impacts on living beings. Due to insufficient uptake of these fertilizers by plants, these reaches into water bodies through rain water, causes eutrophication and affect living beings including growth promoting micro organism. The excess uses of chemical fertilizers in agriculture are costly and also have various adverse effects on soils i.e. it depletes water holding capacity, soil fertility and cause disparity in soil nutrients. It was felt from a long time to develop some low cost effective and eco-friendly fertilizers which work without disturbing nature. Now, certain species of micro-organism are widely used as bio-fertilizers which have unique properties to provide natural products free from chemicals and serve as an ecofriendly substitute to chemical fertilizers.
A bio-fertilizer is a substance which contains living microorganisms which, when applied to seed, plant surfaces, or soil, colonizes the rhizosphere or the interior of the plant and promotes growth by increasing the supply or availability of primary nutrients to the host plant (Vessey, 2003).They add nutrients through the natural processes of nitrogen fixation, phosphorus solubilization and stimulating plant growth through the synthesis of growth-promoting substances. These are eco-friendly, organic in nature and cheaper than chemical fertilizers. Microorganisms like Rhizobium, Azotobacter, Azospirillum and blue green algae (BGA) are most commonly used as bio-fertilizers.
Need of bio-fertilizers
Bio-fertilizers are supposed to be a safe alternative to chemical fertilizers to minimize the ecological disturbance. Bio-fertilizers are cost effective, eco-friendly and when they are required in bulk can be generated at the farm itself. They increase crop yield upto 15-25% and fix nitrogen upto 40-50 Kg. The other plus point is that after using 3-4 years continuously there is no need of application of bio-fertilizers because parental inoculums are sufficient for growth and multiplication. They improve soil texture, pH, and other properties of soil. They produce plant growth promoting substances IAA, amino acids, vitamins etc. They have 75% moisture and it could be applied to the field directly. Bio-fertilizers contained 3.5-4% nitrogen, 2-2.5% phosphorus and 1.5% potassium. In terms of N:P:K, it was found to be superior to farmyard manure and other type of manure (Mukhopadhyay, 2006).
Classification of bio-fertilizers: The bio-fertilizers are classified into four groups on the basis of type of microorganisms used as:
- Algal bio-fertilizers: Example: Azolla, Blue green algae (BGA) etc.
- Fungal bio-fertilizers: Example: Mycorrhiza etc.
- Bacterial bio-fertilizers: Example: Azospirillum, Azotobacter, Phosphobacteria, Rhizobium, etc.
- Actinomycetes bio-fertilizers: Example: Frankia etc.
- Nitrogen bio-fertilizers: This type of bio-fertilizer helps the agriculturists to determine the nitrogen level in the soil. Nitrogen is an essential component for plant growth. Plants needed a limited amount of nitrogen for their growth. Nitrogen requirement depends on both the nature of the soil as well as type of the crop. For example, Azotobacter is used for non-legume crops whereas; Rhizobium is needed for legume crops.
- Phosphorus bio-fertilizers: Phosphorus bio-fertilizer helps to determine the phosphorus level in the soil. The need of phosphorus for the plant growth is also limited. Unlike nitrogen bio-fertilizers, phosphorus bio-fertilizers do not depend on the crop type. They can be used for any type of crop. For example, Acetobacter, Rhizobium and other bio-fertilizers can be used as phosphotika for any crop type.
- Compost bio-fertilizers: Compost bio-fertilizers are those which make use of the animal dung to enrich the soil with useful microorganisms and nutrients. To convert the animals waste into a bio-fertilizer, the microorganisms undergo biological processes and help in breaking down the waste. Cellulytic fungal culture and Acetobacter cultures can be used for the compost bio-fertilizers. They not only protect the plants from diseases but also help them to grow in a healthy environment.
How to apply bio-fertilizers
There are four major ways of applying bio-fertilizers:
- Seed treatment
- Set treatment
- Seedling treatment
- Soil treatment
- Seed treatment: For inculcation of cereals like rice, wheat, sorghum, maize etc. and oilseeds like groundnut, sunflower, mustard, safflower, pulses like cowpea, green gram, black gram, and soybean etc., seed treatment of bio-fertilizer is recommended. One packet (200g) is sufficient to treat 10- 12 kg seed. On this basis the dose of bio-fertilizer per acre can be worked out, based on the seed rate.
- Keep the seeds required for sowing one acre in a heap on a clean cemented floor or gunny bag.
- Prepare culture suspension by mixing 1 packet (200g) bio-fertilizer in approx. 400 ml water (1:2)
- Sprinkle the culture suspension on the heap of the seeds and mix by hand so that thin coating is uniformly applied to the seeds.
- Spread the seeds under shade for some time for drying and then sown.
- In place of water, rice glue can also be used for better results.
- Set treatment: This method is recommended generally for treating the sets of sugarcane, cut pieces of potato and the base of banana suckers.
- Prepare culture suspension by mixing 1 kg (5 packets) of bio-fertilizer in 40-50 litres of water.
- The cut pieces of planting material required for sowing one acre are kept immersed in the suspension for 30 minutes
- Bring out the cut pieces and dry them in shade for some time before planting.
- After planting, the field is irrigated within 24 hours.
- For set treatment, the ratio of bio-fertilizer to water is approximately 1:50.
- Seedling treatment: This method is recommended for crops like paddy, tobacco, tomato, chilly, onion, cabbage, cauliflower etc.
- Prepare the suspension by mixing l kg (5 packets) bio-fertilizer culture in 10-15 litres of water.
- Get the seedlings required for one acre and make small bundles of seedlings.
- Dip the root portion of these seedlings in this suspension for 15-30 minutes and transplant immediately.
- Generally, the ratio of inoculants and water is 1:10 (Approx) i.e. 1 kg bio-fertilizer in 10 litres of water.
- For vegetables like chilly, tomato, cabbage, cauliflower, 1 packet of bio-fertilizer is sufficient for 0.1 ha land.
- Soil application: This method varies from crop to crop depending on its duration. Generally, for a short duration (less than 6 months) crops, 10-15 packets (each of 200g) are mixed with 40-60 kg of well decomposed cattle manure or with 40-60 kg soil for one acre of land. The mixture of bio-fertilizer and cattle manure/soil sprinkled with water is then broadcasted into soil at the time of sowing or at the time of irrigation in standing crop. For long duration crops (perennial crops) 20-30 packets of bio-fertilizer (each containing 200g) are mixed with 80-120 kg cattle manure or soil per acre.
- The term 'Bio-fertilizer' itself denotes that, it is a 'Live Fertilizer'. The quality of bio-fertilizers demands in-depth the study of microbial characteristics, effectiveness, consistency, precautions and limitations not only at laboratory and production level but at field level too.
- Store the packets of bio-fertilizers in cold place, away from direct sun or hot wind.
- The bio-fertilizer should not be used with any other fertilizers of insecticides
- Bio-fertilizers are very specific to be effective to the particular crop(s), so apply them as recommended.
- Tear open the packets of bio-fertilizers only just before use, apply entire packet of bio-fertilizer in one application.
- Treat the seeds (seed coating) or seedling (dipping) under shade only.
- Avoid direct contact of chemical fertilizers and pesticides.
- Bacterial inoculants should not be mixed with insecticide, fungicide, herbicide and fertilizers.
- Seed treatment with bacterial inoculants is to be done at last when seeds are treated with fungicides.
- The bio-fertilizer should be used before expiry date (Das, 2009).
- They supplement chemical fertilizers for meeting the integrated nutrient demand of the crops by adding 20-200 kg N/ha/year(eg. Rhizobium spp. (50-100 kg N/ha/year); Azospirillum, Azotobacter spp. (20-40 kg N/ha/year); Azolla (40-80 kg N/ha); BGA (20-30 kg N/ha) under optimum soil conditions and thereby increases 15-25 per cent of total crop yield.
- Mycorrhiza can provide adequate amount of P, other micro nutrients and helps in increasing water absorption
- BGA plays a vital role in the nitrogen economy of rice fields in tropical regions.
- Azotobacter inoculants when applied to many non leguminous crop plants, promote seed germination and initial vigour of plants by producing growth promoting substances.
- Azolla-Anabaena grows profusely as a floating plant in the flooded rice fields and can fix 100-150 kg N/ ha /year in approximately 40-60 tones of biomass produced,
- Plays important role in the recycling of plant nutrients.
- Bio-fertilizers are cost effective relative to chemical fertilizers. They have lower manufacturing costs especially regarding nitrogen and phosphorus use.
- They can also provide protection against drought and some soil-borne diseases.
- The microorganisms used in bio-fertilizers restore the soil's natural nutrient cycle and build soil organic matter thereby, increasing the soil productivity.
- Through the use of bio-fertilizers, healthy plants can be grown, while enhancing the sustainability and the health of the soil
- Moreover, they do not contain any chemicals which are harmful to the living soil. Hence, they are environment friendly.
- Das, P.C. (2009). Manures and fertilizers. Kalyani publishers, pp. 85.
- Mukhopadhyay, S.N. (2006). Eco-friendly products through process biotechnology in the provision of biotechnology economy: Recent advances. Technorama, A. Supplement to IEI News, March.
- Vessey, J.K. (2003). Plant growth promoting rhizobacteria as bio-fertilizers. Plant Soil, 255: 571-586
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