COMPARATIVE STUDY OF CHEMICAL FERTILISERS AND BIO FERTILISERS
LIMITATIONS OF CHEMICAL FERTILISERS
1. Some fertilisers are more acidifying than others hence the need to use sparingly on low pH soils.
2. Some fertilisers may contain heavy metals or salts which are hazardous.
3. Some fertilizers are highly leachable.
4. With Chemical fertilizers there is always the risk of erosion.
5. Excessive Chemical fertilisers may contaminate the soil and waterways. The high solubilities of chemical fertilizers also exacerbate their tendency to degrade ecosystems, particularly through eutrophication.
6. Production of Chemical Fertilisers depletes the energy reserves drastically as shown below. The production of ammonia currently consumes about 5% of global natural gas consumption, which is somewhat under 2% of world energy production. Natural gas is overwhelmingly used for the production of ammonia, but other energy sources, together with a hydrogen source, can be used for the production of nitrogen compounds suitable for fertilizers. The cost of natural gas makes up about 90% of the cost of producing ammonia. The price increases in natural gas in the past decade, among other factors such as increasing demand, have contributed to an increase in fertilizer price.
Prevalence of pest and disease attack in crops where chemical fertilizers are used is yet another drawback in usage of Chemical Fertilisers.
7. Chemical fertilizers sometimes do not replace trace mineral elements in the soil which become gradually depleted by crops grown there. Hence the need for use of micronutrients arises.
8. There are concerns though about Arsenic, Cadmium and Uranium accumulating in fields treated with phosphate fertilizers. The phosphate minerals contain trace amounts of these elements and if no cleaning step is applied after mining the continuous use of phosphate fertilizers leads towards an accumulation of these elements in the soil.
The concentration of up to 100 mg/kg of cadmium in phosphate minerals (for example, minerals from Nauru and the Christmas islands); increases the contamination of soil with cadmium.
Eventually these Arsenic, Cadmium and Uranium can build up to unacceptable levels and get into the produce.
9. The use of fertilizers on a global scale emits significant quantities of greenhouse gas into the atmosphere and effects on anthropogenic climate change.
Emissions come about through the use of:
urea, which release methane, nitrous oxide, ammonia, and carbon dioxide in varying quantities depending on their form (solid or liquid) and management (collection, storage, spreading)
Fertilizers that use nitric acid or ammonium bicarbonate, the production and application of which results in emissions of nitrogen oxides, nitrous oxide, ammonia and carbon dioxide into the atmosphere.
10. Another problem with inorganic fertilizers is that they are presently produced in ways which cannot be continued indefinitely. Potassium and phosphorus come from mines; and these resources are limited.
11. Nitrogen is unlimited, but nitrogen fertilizers are presently made using fossil fuels such as natural gas. Theoretically fertilizers could be made from sea water or atmospheric nitrogen using renewable energy, but doing so would require huge investment and is not competitive with today's unsustainable methods. Innovative thermal depolymerization biofuel schemes are trialling the production of byproducts with 9% nitrogen fertilizer sourced from organic waste.
12. Storage and application of some nitrogen fertilizers in some weather or soil conditions can cause emissions of the greenhouse gas nitrous oxide (N2O). Ammonia gas (NH3) may be emitted following application of inorganic fertilizers, or manure or slurry. Besides supplying nitrogen, ammonia can also increase soil acidity (lower pH, or "souring"). Excessive nitrogen fertilizer applications can also lead to pest problems by increasing the birth rate, longevity and overall fitness of certain pests.]
13. Ever increasing prices of the Chemical fertilizers, scarcity of these chemical fertilizers, the burden on Government in the shape of Subsidy on these chemical fertilsers presses the need to look for alternates.
||(In Indian Rupees Per Tonne)
|| 4830 -6500
1. Activate the soil biologically.
2. Biological control of soil pest and diseases.
3. Bridge the gap between the need of Total Absorbable Nutrients of Agricultural Industry and the availability of Chemical Fertilisers from the Fertiliser Industry.
4. Consumer friendly
5. Cost effective when compared to expensive chemical fertilizers.
6. Degrades the organic residues into nutrients that can be absorbed by the plants.
7. Degrades xenobiotic toxic compounds, mainly pesticides.
8. Direct or indirect supply of nutrients to plants.
10. Enaction of mutualistic symbiotic relationships with plants.
11. End user friendly.
12. Enhance soil chemical and physical properties.
13. Increase crop yield by 20-30%.
14. Non pollutant and non carcinogenic.
15. Produce plant growth promoting substances.
16. Provide protection against drought and some soil borne diseases
17. Reduces the costs towards fertilizers use, especially regarding nitrogen and phosphorus.
18. Replace chemical nitrogen and phosphorus by 25%.
19. Restore natural soil fertility.
20. Stimulate plant growth.
21. Suppliment to fertilizers.
It is very interesting to note that most of the plants feed by releasing root exudates of precise chemical composition to activate their friendly soil fungi and bacteria which will solubilize elements required by the plant at that time. The exudate composition varies throughout the life of the plant, and any stresses imposed upon it result in further compensatory changes - in essence, the plant practises self medication. The term 'nature's smorgasbord' was coined to explain this process. 'Nature's smorgasbord' provides a possible explanation for the prevalence of pest and disease attack in crops fertilized by chemical means - applied soluble fertilizer masks the 'smorgasbord' process, eliminating correct nutrition.