BIO-FERTILIZER AND ITS USES
Apr 28 - May 11, 2008
With the increased population growth rates, there will be an increased pressure on the agricultural lands for producing more food. Even marginal lands are put to production and most demand now is directed to rain-fed agriculture for more output. All of these demands for more outputs mean simply one thing "more inputs," the most important and the most effective is the "Fertilizer Input". Food and Agriculture Organization, Rome has reported that up to 50% of the growth in agricultural production that was witnessed in developing countries during the few past decades was due to the used chemical fertilizers. The fertilizers use rate is some of the countries of the region are among the highest worldwide. In Egypt, for example the national average for fertilizer consumption was 347 kg/he, Saudi Arabia 336 kg/ha, Pakistan 73 kg/ha, while USA is 42 kg/ha and world average is 28 kg/ha. Huge quantities of fertilizers are applied annually to soils all over the world (22 billion metric tons fertilizers, in addition to 16 million metric tons of herbicides, 18 million metric tons of insecticides and 12 million metric tons of fungicides).
All these chemicals that are taken by plants absorbed in the soil, volatilize in the air or otherwise leach down with drainage water, join the groundwater and cause pollution. High levels of nitrates are very common in irrigated agriculture especially with intensive agriculture related to surface irrigation and high fertilizer rate there is a matter of concern in Pakistan as it is one of the countries consuming very large amounts of nitrogen per unit area. There are estimates that the use of nitrogen fertilizers will continuously increase till the year 2010. Optimizing the use of fertilizer and minimizing losses will help increasing the yield ensuring high quality, decreasing environmental hazards and probably will help the fertilizers industry to have a surplus production for export. The world Health Organization (WHO) estimated that around 1 million chemical compounds are used worldwide and millions of tons of these chemicals (poison) are used annually on our lands and in our environment. In US alone it was estimated that about 60,000 newborn children are with some mental/physical retardation due to pesticides used during the last 50 years.
Bio-fertilizers or Bio-organic farming offer the potential solution to the various problems facing the current agricultural practices. Bio-organic farming works in harmony with the natural system rather than to dominate, encourages and enhances biological cycles within the farming system, furnishes conditions of life that allows all possible genetic diversity of agricultural system and its surroundings including the protection of plants and wild-life habitat by furnishing conditions of life that would allow all life forms to perform freely all aspects of their innate behavior. Here, the choice is always being the choice of material, substances and/or practices, which are the least environmentally disruptive both at the micro and macro levels. The world population is increasing tremendously at a time, when food production continues to decline. Drought, salinization, unavailability of inputs and inappropriate utilization of resources are the main reasons that add to food shortage. Low-cost nitrogen is one of the requisites for the small rice farmers of the tropics and subtropics. Two events have stimulated research to provide low-income rice farmers with lower cost nitrogen for their rice fields. First, energy shortages have increased nitrogen fertilizers costs, second the efficiency of utilization of applied nitrogen by rice is markedly influenced by timing and placement of the applied nitrogen.
Bio-fertilizers are microbial preparations which supply nutrients especially nitrogen and phosphors to crops. Application of the bio-fertilizing system is much cheaper than that of the chemical fertilizers. Bio-fertilizer or microbial inoculants is a blend of live, biologically active and efficient bacteria, actinomycetes, azolla, mycorrrhizae etc. that can provide plant nutrients viz. nitrogen and phosphorus at cheaper cost when compared with chemical fertilizer. It solubilizes phosposphates, sulphates and other essential minerals from soil, making them more bio-available. It removes these minerals from soil eliminating soil pollution. It decomposes organic material and also increases water holding capacity of soil. It releases active bio-molecules which accelerate plant growth. Bio-fertilizers and organic manures are environment friendly and important basic inputs for sustainable agriculture. Their integrated uses thus can cause a reduction in application of chemical fertilizers and pesticides and overall cost of cultivation of crops. For a sustainable agriculture system, it is imperative to utilize renewable inputs which can maximize the ecological benefits and maximize the environmental hazards. One possible way of achieving this is to decrease dependence on use of chemical nitrogen fertilizers by harvesting the atmospheric nitrogen through biological processes.
As bio-fertilizers, blue-green algae and azolla are important groups of microorganisms capable of fixing atmospheric nitrogen. They grow most abundantly in tropical and subtropical regions and are common in flooded rice paddy soils. Their possible role is the nitrogen accumulation in soil. Blue-green algae represent sell-supporting system of carrying out both photosynthesis and biological nitrogen fixation.
The energy requirement for the latter process is being provided by the Sun. The amount of nitrogen fixed by Blue-green algae is dependent on the algal species as well as physiological and environmental conditions. The amount of nitrogen fixed by blue-green algae (BGA) under laboratory condition varies markedly according to the algal species, the type of medium, incubation period, and growth condition. These amounts ranged between 22-270 mg/100 ml medium whereas, the amount of nitrogen fixed by BGA under field conditions ranges between 15-80 kg/ha according to the algal species, fertilization, soil and environmental conditions. Blue-green algae liberate large quantities of ammonia extra-cellulary as well as variety of organic compound and some growth promoting substances.
Azolla is a floating aquatic fern. It grows vigorously in drainage canals, ponds, paddy fields and stagnant pools of rivers and is widely distributed in tropical and temperate zones. Azolla contains in the cavities of its leaflets hetercystous filamentous BGA called Anabaena azollae. It contains 3-4% dry mass and 4-5% nitrogen. Azolla may grow at a temperature of 14-30 C with optimum 25-30 C. The doubling time of Azolla varies depending on the species, locality and growth condition. Azolla anabaena symbiosis has proven to be effective and also as a source of N for rice. The use of Azolla as green manure, and composting of Azolla in rice fields were reported in China, Thailand, Vietnam, Cambodia, Burma, Japan, India, and Pakistan. In the past two decades field experiments have been carried out using rice crop in Research Institutes at Tandojam and Dokri in Sindh, Faisalabd and Kala Shah Kaku in Punjab successfully. It has been observed that mixing Azolla in rice field has increased the production of rice grains when compared with field with Azolla. The fern Azolla under the most favorable condition can fix 7.8-9.7 mg N/g dry weight/day. Azolla releases about 12-20% of its fixed N as ammonia into the surrounding medium. Estimates of total nitrogen inputs of Azolla in paddy soils are rather variable. Estimations of 100-160 kg N/ha/4 months and 500 kg N/ha/year were recorded in Far Eastern countries. Azolla is grown in small plots or ponds as a mono crop. It is then transferred to the rice field and incorporated into the paddy soil as a green manure before rice transplanting. Azolla is grown as an intercrop with rice by spreading Azolla on the surface of water in rice field. After growth, Azolla is either incorporated as a green manure or allowed to die naturally without incorporation. Azolla is grown as both mono crop and intercrop. Azolla has high nitrogen content and a favorable C/N ratio, which allows it to decompose rapidly. When incorporated into the soil, Azolla helps to increase soil organic and improves soil chemical and physical properties. Azolla starts to decompose in 5-10 days and begins to release its nitrogen. The rate of decomposition is significantly affected by the variety, stage of maturity and soil environment. Some rice varieties are more responsive to inoculation with Azolla. For more than 100 years, the legume symbiosis was known to be the most efficient way of transforming atmospheric nitrogen into plant nutrients. Legume crops such as green gram, dhancha, mung, pigeon pea, cow pea, chickpea, lentil, ground nut, clover, guar, soybean, berseem and fenugreek are very important in N-fixation. Thus, in view of the increasing cost of chemical fertilizer, the use of bio-fertilizers is very essential in the present day for increasing the agricultural products.
There is a strong need for integrated efforts by researcher workers and scientists to increase use of bio-fertilizer, as this environmentally safe product would not only increase rice crop yields but also would help to reduce the burden of expensive chemical fertilizers. The future of bio-fertilizers depends on the farmers or end users, who have to see the benefits of bio-fertilizers such as increased crop yield, sustainable agriculture, environment-friendly and cost-effectiveness. In Asia, sustainable agriculture is essentially important to support increasing population.