Agrochemicals and soil micro-biota

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Chemicals that are used in agricultural industries, in particular for crop protection, are known as agrochemicals or the synonym agrichemicals. Many agrichemicals are toxic, and agrichemicals in bulk storage may pose significant environmental and/or health risks, particularly in the event of accidental spills. In many countries, use of agrichemicals is highly regulated. Government-issued permits for purchase and use of approved agrichemicals may be required. Significant penalties can promote misuse, including improper storage resulting in spillage. On farms, proper storage facilities and labeling, emergency clean-up equipment and procedures, and safety equipment and procedures for handling, application and disposal are often subject to mandatory standards and regulations.

Pesticides hamper the activities of soil nitrifying and denitrifying bacteria, michorhizal fungai, mites, earthworms, collembola, microflora and microearthpods. Pesticides can affect the soil biodata directly or indirectly. The direct effects may be short term but the indirect effects may be long term due to changes in nutrient management and soil pH. These short term and long term affects can adversely affect the soil nutrient status and crop productivity depends on changes in these effects.

One big issue for growers is of potential damage to the soil by application of high amounts of ammonia or anhydrous ammonia. But this damage is direct and short term which can be compensated. It is concluded that there are no adverse effects on soil microorganisms by the application of banded ammonia and urea within a year but the long term damages are still under discussion. Micorrhizal fungai has been consistently reported that it is decreased by the application of P fertilizer, but the amount of decrease is dependent on the amount of P available to plant and the fungus species that is involved. The effects of agricultural chemical compounds on soil microrganisms differ with the chemical used. Inorganic fertilizers applied to fields promote an explosion of higher plant production than occurs in fields that are not fertilized. This quickly throws the soil ecosystem out of balance leading to an amphetamine-like spike and crash of earthworm and other microorganism populations. Nitrogen fixing bacteria are also often negatively affected. This again leads to a cycle requiring repeated and more intense use of nitrogen based chemical fertilizer. It has also been demonstrated that almost all herbicides are only somewhat toxic to worms-a surprising outcome. When other pesticides have been examined, they normally fell into two classes: Harmless to moderately poisonous, and highly toxic.

Some of the major harmful effects of agro-chemicals are: (1) Land turns infertile due to adverse side effects of the chemical fertilizers. (2) Plants lose their capacity to resist pest and insects and become susceptible to many sorts of diseases. (3) Users need to spray insecticides quite frequently, which increases their expenditure and causes many health hazards to the human beings and environment. (4) Chemical fertilizer increases the pH of the soil. (5) Reduces quality and quantity of produce. (6) Decreases life of fruits, flowers, leaves, vegetables and grains. (7) Fruits and vegetables have high toxic residues if chemical fertilizers , insecticides are spread on them to save them from pest attack and when human being eat such fruits and vegetables they have serious health problems. Same is the case with flowers and plants leaves. (8) Plants can absorb only 5% of food elements from the chemical fertilizers. The acidic and alkaline elements of the remaining chemical fertilizers react with soil and forms thick layers of rocks in the soil and leaves. This rocky layer makes the land infertile. (9) Accelerate the process of soil erosion. (10) It has no energy, so it can only help the plant when there is enough organic matter around from where it can get the energy, otherwise it burns the roots and destroys the plant. (11) It degrades ecosystem. (12) It releases a greenhouse gas called nitrous oxide. (13) It has no energy, so it can only help the plant when there is enough organic matter around from where it can get the energy otherwise it burns the roots and destroys the plant.

There is a clear evidence that biodata is influenced by the fertilizers pesticides herbicides and insecticides. But these effects are wide ranged and some effects are stimulatory some are inhibitory. Effects may be direct or indirect and are dependent upon mode of application and, soil environment and the food sources that are available at that time. The dynamic nature of soil biology and the effect of soil environment on the fate of chemical that is added and the population of the functional groups of biodata, makes it very difficult to draw the conclusion about the various inputs of our agriculture system.

The authors are associated with Agro-Biology Lab, Department of Agronomy, University of Agriculture, Faisalabad.


Published in: Volume 05 Issue 43

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