Modern agricultural practices largely rely on high inputs of mineral fertilizers to achieve high yields and involve applications of chemical pesticides to protect crops against pathogens and pests.
These practices are now being re-evaluated and are coming under increased scrutiny as our awareness about the consequences of excessive use of fertilizers and chemical pesticide usage improves.
It is widely recognized that applications of mineral fertilizers, (especially nitrogen), can result in groundwater contamination by nitrates leaching through the soil profile. Under certain soil conditions, denitrification of applied nitrogen fertilizer can give rise to gaseous nitrogenous compounds that volatilize from the soil into the atmosphere. Some of them, e.g. nitrous oxide, are thought to contribute to the greenhouse effect and/or the alteration of the ozone layer. Similarly, use of chemical pesticides has raised concern about their possible presence of their residues in the food chain and in the environment.
Concerns about the possible consequences of using increasing amounts of chemical pesticides have led to an strong interest in alternative strategies to ensure competitive yields and protection of crops. This new approach to farming, often referred to as sustainable agriculture, seeks to introduce agricultural practices that are friendlier to the environment and that maintain the long-term ecological balance of the soil ecosystem.
In this context, the use of microbial inoculants (biofertilizers, phytostimulators and biopesticides) is considered as the alternate source to meet the nutrient requirement of crops. Knowing the deleterious effects of using only the chemical fertilizers, use of soil microorganisms which can either fix atmospheric nitrogen or solubilize phosphate or stimulate plant growth through synthesis of growth promoting substances will be environmentally benign approach for nutrient management and ecosystem function.
The concept of biofertilizers is to domesticate some of these microorganisms in our agricultural production systems, so that the vast natural reservoir of nitrogen in the atmosphere can be tapped as an additional source to meet our requirements. It will augment additional yields and monetary returns to the farmers, particularly to the small and marginal ones, for which the incremental input cost is low. During the last decades, important scientific investments have been made into the use of microbial inoculants with considerable economic or social return. New strategies, focusing on the inoculant to its acceptability by users, are being fostered to develop new inoculants for agriculture and environment and to increase their practical use in tune with existing agricultural practices.
Biofertilizers: The term bacterial (microbial) fertilizers or biofertilizers/bioinoculants refers to preparations containing active or latent strains of microorganisms mainly bacteria in sufficient numbers either alone or in combination with algae or fungi. These products enhance crop productivity in the following ways:
* by converting atmospheric nitrogen to plant usable form (biological nitrogen fixation);
* by solubilizing insoluble or fixed soil nutrients and make them available to plants (phosphate solubilization)
* By elaboration of plant growth promoting substances (hormones);
* by enhancing the decomposition of plant residues/green manuring to release vital nutrients and increase humic content of soils.
Most commonly biofertilizers are used for providing nitrogen to legume crops. The availability of bacteria which can provide nitrogen and can also be beneficial for the growth of other crops such as rice and wheat has made such biofertilizers very cost effective.
Biopower: Scientists of Pakistan Atomic Energy Commission at NIBGE have developed a state-of-the-art technology for large scale and cost effective production of biofertilizers along with their efficient delivery system to the end-user. This product is being marketed under the trade name of BioPower. Different biofertilizers are suitable for different crops e.g., Rhizobium for legumes comprising pulses like chickpea, lentil, pea, soybean, mungbean, cowpea, blackgram and fodder legumes viz, lucerne, berseem, clover, etc, while associative nitrogen fixing and plant growth promoting bacteria (PGPR) for cereals like wheat, rice, sugar-cane, grasses, etc. the nitrogen fixing bacteria provide nitrogen to plants, while the PGPR produce growth hormones which stimulate root proliferation: resulting in faster water and nutrient uptake leading to luxuriant plant growth.
The extensive research has confirmed that in agricultural soils, nitrogen fixing bacteria play an important role to restore nitrogen status of the soil. Results of the laboratory and the field trials using N dilution technique have indicated that in our agricultural soils 40-70 per cent of the requirements of the plants can be met through BNF.
Biofertilizers for legumes: Legume biofertilizers are the fruition of research focused on exploiting the specific nodule formation property of legume plants in association with soil bacteria called Rhizobium. Such rhizobial inoculants have proved to be immensely beneficial in improving crop yields and soil fertility. The first step in this technology is the collection of nodules from field. These nodules are surface sterilized, crushed and rhizobial cells from nodules are cultured on selective medium agar plates under sterilized conditions.
These isolates are then characterized through different techniques like plant infectivity, ARA, phosphate solubilization, phytohormone production, molecular techniques like RAPD and 16SrRNA, sequence analysis, tolerance to various environmental conditions like temperature, salinity, stress and agro-chemical tolerance. Authenticated cultures are then lyophilized and conserved for future use.
These microorganisms are then axenically cultivated on a large scale under controlled conditions. The first steps in biofertilizer production is the preparation of carrier materials which is ground into a fine amorphous form. This is then packaged in plastic bags, which are then gamma sterilized. After sterilization, the microbial inoculants are added to the product in appropriate quantities. Strict quality control measures are adhered to with the production of microbial inoculants.
Various inoculant quality tests like total cell count, plate count, plant infection count are used to assess the quality of the product. These legume biofertilizers are specific for different legumes and completely substitute the synthetic nitrogen.
For rice: Biofertilizer for rice was provided in more than 20,000 acres of rice growing areas of Punjab. With the use of this biofertilizer a net benefit due to saving in nitrogen fertilizer and additional rice yield is about Rs 2000 per acre. The bacterial inoculum of Biopower not only provides nitrogen and growth hormones, but make the plants healthy and less susceptible to pathogen.
It is a low cost approach and can be used to enhance rice production as well as soil fertility with relatively less input of chemical fertilizers for inoculation. The roots of rice seedlings are dipped for at least half an hour in Biopower suspension in water. One pack is sufficient for bacterial inoculation of rice seedling of one acre. Using the optimal dosage of biofertilizer saves approximately half of the recommended use of doze of chemical nitrogen fertilizer for one acre.
The NIBGE scientists have done substantial work on the survey of BGR: biofertilizers namely Azolla, its cultivation and effect on rice yield. The cultivation of Azolla its effect on salinity, pest control and mineralization under controlled conditions have already been extensively studied, Algalization of rice crop along with N-15 labelled fertilizer has been found to supplement nitrogenous fertilizers to a considerable extent and can significantly reduce the fertilizer N losses due to decrease in flood water pH in rice-azolla culture. BGA fertilizers not only increase the rice yield but also increase the yield of the following wheat crop due to its better residual effect when compared to chemical fertilizer.
For wheat: The use of biofertilizers helps in saving chemical nitrogen fertilizer in the wheat crop, Its use promotes soil fertility and better crop production is obtained with relatively less expenditure on chemical fertilizers.
By using Biopower at the time of wheat sowing farmers save 30-50 per cent chemical N fertilizer associative N fertilizer with 15 per cent average rise in yield. Different microorganisms used in biofertilizer associative N fixer and plant growth promoting rhizobacteria.
By use of Biopower a saving of half dose of nitrogen fertilizer is possible. The plants show better growth and enhanced yield. The soil texture is also improved by using biofertilizer. Wheat Biopower can be applied on the seeds just before sowing by wetting the seed with water and mix the carrier based Biopower with seeds.
For maize/cotton: Experimental trails have been carried out to observe the effect of Biopower on maize and cotton crops and the results have been quite promising. This product is scheduled to be launched soon.
Cost benefit: The use of biofertilizer can significantly increase the crop yield in the country. For example, rice is grown in about two million hectares in Pakistan and most of the farmers reported 500 kg (or more) increase in paddy yield per hectare. Thus even if we consider the minimum increase of 500 kg per hectare due to bicfertilizer application, an additional one thousand million. kg of paddy, worth US dollar 100 million can be produced with the use of biofertilizers. Similarly, the increase in the yield of other crops such as wheat and legumes will also have a great impact on the economy of the country.
The use of biopower will minimize dependence on the chemical fertilizers and save renewable energy resources. Pakistan for example, stands to gain a net saving of Rs 1.7 billion (US dollar: 0.2 million) annually if we meet only 10 percent fertilizer requirements through biofertilizers. Therefore, returns on the investment in this technology are quite well proven.
Foreign perspective: Biofertilizers were launched with the commercial name of ‘Biopower’ in 1996 and with time have developed all necessary expertise and the infrastructure to undertake the biofertilizer production. The technology developed by NIBGE is notable because of the large and high quality fermentation, totally integrated production process, automatic mixing, filling and packaging system, experienced personnel in all phases of production. The pilot project has been designed to upscale the fertilizers production in the near future.