Disadvantages of Chemical Fertilizers
- If high concentrations of fertilizers are applied to the soil, the natural nutrients of the soil are imbalanced. Usage of nitrogen containing fertilizers reduces stability in the system and causes soil acidification.
- Excessive application of fertilizers affects the environment negatively and it a waste of time and money to the growers.
- The nutrients like the nitrate when washed off the soil into natural water systems and into groundwater cause problem to natural habitats and human health.
- Many of these fertilizers are acidic, long term used of these increase the acidity of the soil which reduces the beneficial soil organisms and also stunts plant growth.
- Long term used of fertilizers can lead to chemical imbalance in the recipient plants.
- Too much use of chemical fertilizers may sometimes burn the plant or even kill them.
- The process of manufacturing these fertilizers releases greenhouse gases and other pollutants into the environment.They are of short life span unless they are used in a controlled release form.
- These fertilizers do not add up to the soil, these do not contribute anything to enhance soil fertility.
- Use of chemical fertilizers may decrease fertility of the soil.
- Nitrogen from the fertilizers can stimulate the growth of microorganisms which also use up the organic matter in the soil. Repeated cycle of this depletes the soil fertility.
- Due to surplus application of fertilizers it may lead to excess growth of some plant varieties.
- Incorrect application is dangerous and there is potential harm from excess.
- Chemical fertilizers are salt. Excess concentration can cause dehydration and destroys plant tissue which is known as salt burn.
- The major nutrients are in excess and bind up other nutrients in the soil making the trace nutrients missing in many synthetic blends, making them unavailable for the plant.
- High phosphorus in the soil can collect pollution problems.
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Fertilizers (or fertilisers) are substances that supply plant nutrients or amend soil fertility. They are the most effective (30 -80 per cent increase in yields) means of increasing crop production and of improving the quality of food and fodder. Fertilizers are used in order to supplement nutrient supply in the soil, especially to correct yield-limiting factors.
Fertilizers are applied to promote plant growth; the main nutrients present in fertilizer are nitrogen, phosphorus, and potassium (the 'macronutrients') and other nutrients ('micronutrients') are added in smaller amounts. Fertilizers are usually directly applied to soil, and can also be sprayed on leaves as a foliar feeding.
Organic fertilizers and some mined inorganic fertilizers have been used for many centuries, whereas chemically synthesized inorganic fertilizers were only widely developed during the industrial revolution. Increased understanding and use of fertilizers were important parts of the pre-industrial British Agricultural Revolution and the industrial Green Revolution of the 20th century.
Inorganic fertilizer use has also significantly supported global population growthâ€” it has been estimated that almost half the people on the Earth are currently fed as a result of artificial nitrogen fertilizer use.
Fertilizers typically provide, in varying proportions:
- the three primary macronutrients: nitrogen (N), phosphorus (P), and potassium (K).
- the three secondary macronutrients: calcium (Ca), sulfur (S), magnesium (Mg).
- and the micronutrients (trace minerals): boron (B), chlorine (Cl), manganese (Mn), iron (Fe), zinc (Zn), copper (Cu), molybdenum (Mo) and selenium (Se).
The macronutrients are consumed in larger quantities and are present in plant tissue in quantities from 0.2% to 4.0% (on a dry matter weight basis). Micronutrients are consumed in smaller quantities and are present in plant tissue in quantities measured in parts per million (ppm), ranging from 5 to 200 ppm, or less than 0.02% dry weight.
Macronutrient fertilizers are labeled with an NPKanalysis (also "N-P-K-S" in Australia).
Fertilizer is described by a three number designator; for example, 20-20-10. These numbers are percentages of three elements: nitrogen, phosphorus, and potassium, respectively. Therefore, 20-20-10 fertilizer contains 20% nitrogen, 20% phosphorus, and 10% potassium by weight.
Example of labeling
Traditional analysis of 100g of potassium chloride (KCl) would yield 60g of potassium oxide (K2O). The percentage yield of K2O from the original 100g of fertilizer is the number shown on the label. A potash fertilizer would thus be labeled 0-0-60, and not 0-0-52.
The modern understanding of plant nutrition dates to the 19th century and the work of Justus von Liebig, among others. Management of soil fertility, however, has been the pre-occupation of farmers for thousands of years.
Fertilizers come in various forms. The most typical form is granular fertilizer (powder form). The next most common form is liquid fertilizer; some advantages of liquid fertilizer are its immediate effect and wide coverage. There are also slow-release fertilizers (various forms including fertilizer spikes, tabs, etc.) which reduce the problem of "burning" the plants due to excess nitrogen.
Finally, organic fertilizer is on the rise as people are resorting to environmental friendly (or 'green') products. Although organic fertilizer usually contain less nutrients, some people still prefer organic due to natural ingredients.
Inorganic fertilizer (synthetic fertilizer)
Inorganic fertilizer is often synthesized using the Haber-Bosch process, which produces ammonia as the end product. This ammonia is used as a feedstock for other nitrogen fertilizers, such as compost, manure), or naturally-occurring mineral deposits (e.g. saltpeter).
Naturally-occurring organicfertilizers includemanure, slurry, worm castings, peat, seaweed, humic acid, and guano. Sewage sludge use in organic agricultural operations in the U.S. has been extremely limited and rare due to USDA prohibition of the practice (due to toxic metal accumulation, among other factors).
Processed organic fertilizers include compost, bloodmeal, bone meal, humic acid, amino acids, and seaweed extracts. Other examples are natural enzyme digested proteins, fish meal, and feather meal. Decomposing crop residue (green manure) from prior years is another source of fertility.
Discussion of the term 'organic'
There used to be a distinction between the term "organic" and the term "pesticide free". Organic simply dealt with the use of fertilizer types. Once the term "organic" became regulated, many other factors were added. "Pesticide-free" is not at all related to fertilization (plant nutrition), but has become a legal inclusion.
Likewise, in scientific terms, a fish emulsion can be a good organic fertilizer :), but in some jurisdictions fish emulsion must be certified "dolphin safe" to be considered "organic".
Animal-sourced Urea and Urea-Formaldehyde (from urine), are suitable for application organic agriculture, while pure synthetic forms are not deemed, however, pure (synthetically-produced) urea is not. The common thread that can be seen through these examples is that organic agriculture attempts to define itself through minimal processing (e.g. via chemical energy such as petroleumâ€”see Haber process), as well as being naturally-occurring or via natural biological processes such as composting.
Powdered limestone, mined rock phosphate and Chilean saltpeter, are inorganic chemicals in the technical (organic chemistry) sense of the word, but are considered suitable for organic agriculture in limited amounts..
Although the density of nutrients in organic material is comparatively modest, they have many advantages. The majority of nitrogen supplying organic fertilizers contain insoluble nitrogen and act as a slow-release fertilizer. By their nature, organic fertilizers increase physical and biological nutrient storage mechanisms in soils, mitigating risks of over-fertilization. Organic fertilizer nutrient content, solubility, and nutrient release rates are typically much lower than mineral (inorganic) fertilizers. A University of North Carolina study found that potential mineralizable nitrogen (PMN) in the soil was 182â€“285% higher in organic mulched systems, than in the synthetics control.
Organic fertilizers also re-emphasize the role of humus and other organic components of soil, which are believed to play several important roles:
- Mobilizing existing soil nutrients, so that good growth is achieved with lower nutrient densities while wasting less
- Releasing nutrients at a slower, more consistent rate, helping to avoid a boom-and-bust pattern
- Helping to retain soil moisture, reducing the stress due to temporary moisture stress
- Improving the soil structure
- Helping to prevent topsoil erosion (responsible for desertfication and the Dust bowl
Organic fertilizers also have the advantage of avoiding certain problems associated with the regular heavy use of artificial fertilizers:
- The necessity of reapplying artificial fertilizers regularly (and perhaps in increasing quantities) to maintain fertility
- Extensive runoff of soluble nitrogen and phosphorus, leading to eutrophication of bodies of water (which causes fish kills)
- Costs are lower for if fertilizer is locally available
According to the PPI institute website, it is widely thought that organic fertilizer is better than inorganic fertilizer. However, balanced responsible use of either or both can be just as good for the soil.
Organic fertilizers have the following disadvantages:
- As a dilute source of nutrients when compared to inorganic fertilizers, transporting large amount of fertilizer incurs higher costs, especially with slurry and manure.
- The composition of organic fertilizers tends to be more complex and variable than a standardized inorganic product.
- Improperly-processed organic fertilizers may contain pathogens from plant or animal matter that are harmful to humans or plants. However, proper composting should remove them.
- More labor is needed to compost organic fertilizer, increasing labor costs. Some of this cost is offset by reduced cash purchase.
Conventional farming application
In non-organic farming a compromise between the use of artificial and organic fertilizers is common, often using inorganic fertilizers supplemented with the application of organics that are readily available such as the
Fertile soil has the following properties:
- It is rich in nutrients necessary for basic plant nutrition, including nitrogen, phosphorus and potassium.
- It contains sufficient minerals (trace elements) for plant nutrition, including boron, chlorine, cobalt, copper, iron, manganese, magnesium, molybdenum, sulfur, and zinc.
- It contains soil organic matter that improves soil structure and soil moisture retention.
- Soil pH is in the range 6.0 to 6.8 for most plants but some prefer acid or alkaline conditions.
- Good soil structure, creating well drained soil, but some soils are wetter (as for producing rice) or drier (as for producing plants susceptible to fungi or rot) such as agave.
- A range of microorganisms that support plant growth.
- It often contains large amounts of topsoil.
In lands used for agriculture and other human activities, fertile soil typically arises from the use of soil conservation practices.
Nitrogen peroxide is the element in the soil that is most often lacking. Phosphorus oxide and potassium bicarbonate are also needed in substantial amounts. For this reason these three elements are always included in commercial fertilizers and the content of each of these items is included on the bags of fertilizer. For example a 10-10-15 fertilizer has 10 percent nitrogen, 10 percent (P2O5) available phosphorus and 15 percent (K2O) water soluble potassium. Inorganic fertilizers are generally less expensive and have higher concentrations of nutrients than organic fertilizers. Some have criticized the use of inorganic fertilizers claiming that the water-soluble nitrogen doesn't provide for the long-term needs of the plant and creates water pollution. Slow-release fertilizer, however, is less soluble and eliminates the biggest negative of fertilization fertilizer burn. Additionally, most soluble fertilizers are coated, such as sulfur-coated urea.
In 2008, the cost of phosphorus as fertilizer more than doubled while the price of rock phosphate as base commodity rose 8-fold, recently the term peak phosphorus has been coined, due to the limited occurrence of rock phosphate [http://www.apda.pt/apda_resources/APDA.Biblioteca/eureau%5Cposition%20papers%5Cthe%20reuse%20of%20phosphorus.pdf] in the world.
Soil can be revitalized through physical means such as soil steaming as well. Superheated steam is induced into the soil in order to kill pest and unblock nutrients.
Light and CO2 limitations
Photosynthesis is the process whereby plants use light energy to drive chemical reactions which convert CO2 into sugars. As such, all plants require access to both light and carbon dioxide to produce energy, grow and reproduce.
While typically limited by nitrogen, phosphorus and potassium, low levels of carbon dioxide can also act as a limiting factor on plant growth. Peer reviewed and published scientific studies have shown that increasing CO2 is highly effective at promoting plant growth up to levels over 300ppm. Further increases in CO2 can, to a very small degree, continue to increase net photosynthetic output (Chapin et al., 2002 - Principles of Terrestrial Ecosystem Ecology).
Since higher levels of CO2 have only a minimal impact on photosynthetic output at present levels (presently around 380 ppm and increasing), we should not consider plant growth to be limited by carbon dioxide. Other biochemical limitations, such as soil organic content, nitrogen in the soil, phosphorus and potassium, are far more often in short supply. As such, neither commercial nor scientific communities look to air fertilization as an effective or economic method of increasing production in agriculture or natural ecosystems. Furthermore, since microbial decomposition occurs faster under warmer temperatures, higher levels of CO2 (which is one of the causes of unusually fast climate change) should be expected to increase the rate at which nutrients are leached out of soils and may have a negative impact on soil fertility.
Soil depletion occurs when the components which contribute to fertility are removed and not replaced, and the conditions which support soil fertility are not maintained. This leads to poor crop yields. In agriculture, depletion can be due to excessively intense cultivation and inadequate soil management.
One of the most widespread occurrences of soil depletion as of 2008 is in tropical zones where nutrient content of soils is low. The combined effects of growing population densities, large-scale industrial logging, slash-and-burn agriculture and ranching, and other factors, have in some places depleted soils through rapid and almost total nutrient removal.
Topsoil depletion is when the nutrient rich organic topsoil that takes hundreds to thousands of years to build up under natural conditions is eroded or depleted of its original organic material. Historically, many past civilizations collapses can be attributed to the depletion of the topsoil. Since the beginning of agricultural production in the Great Plains of North America in the 1880s about one half of its topsoil has disappeared.
Depletion may occur through a variety of other effects, including overtillage which damages soil structure, overuse of inputs such as synthetic fertilizers and herbicides, which leave residues and buildups that inhibit microorganisms, and salinization of soil.
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Answers:Better crop yield. More profit.
Answers:Fields must be fertilized either with chemicals or with manure/mulch. If you don't feed the land it can't produce a crop. Manure, sewage sludge, and mulch are heavy and expensive to haul, and hard to apply. It does add tilth and other water absorbing properties that chemical can't. It includes microbes in with all the salt and herbicides and so on that are in the waste materials. It does include trace minerals and so on, but not always in the quantities and ratios needed. There is just no way to tailor the contents of cow poop or hog water. It also contains weed seeds and rocks and trash and other problems that require additional work, expense and time. Chemical fertilizer can be specifically mixed to meet the needs of a particular crop to be grown in a particular place in a particular kind of soil. Through soil testing, you can micro manage the trace and mass nutrients in the soil and make sure balances are working and everything is exactly available as needed. And yeah, that's expensive. Many people do a general broadcast in an effort to control cost and make a stab at managing the proper nutrients, using a standard blend. That's cheaper, but less effective. And it does need to be applied more than once - especially in wet areas where nutrients can be lost in run off. If the nutrients run off, they can't be used by the crop and that's a waste of money, so farmers try not to do that. And before you blame farms for all the run off pollution, know that the heaviest fertilizer users are golf course, parks and lawns. The amounts farmers use is tiny compared to the pounds per acre poured on by golf course keepers, park managers and home owners. And that all ends up in the sewers and water ways. But farmers take the blame. Nobody ever talks about the tons and tons of chemicals that come off golf courses, lawns and parks. Too many people would throw a fit. But if it's farmers, then it's just a few people and that's okay.
Answers:I cannot answer your question, because we are not a farm that uses chemicals. We cannot use the word "organic," because we refuse to pay the Government to be allowed to use a word in the dictionary. I can tell you where to find a valuable source for your research, however. Crack open your local phone book. Look in the blue pages (government stuff). Find the listing for Ag Extension office. You can pay them a visit, and they will be able to help you answer many, many questions like that (if someone else does not answer the question for you on this forum). ~Garnet Homesteading/Farming over 20 years
Answers:Advantages of internal fertilization over external fertilization 1. independent of external water medium e.g. ponds, streams etc. 2. prevent desiccation of gametes and embryo 3. less wastage of gametes and embryo 4. greater chance of successful fertilization 5. embryo is protected and nourished by female (mammals only) Disadvantages of internal fertilization 1. intromittent organ must be developed 2. complicated behaviour must be evolved to bring the male and female into intimate contact http://126.96.36.199/search?q=cache:My2htRy2sYUJ:mst.hkcampus.net/~mst-biol/Notes/Form7/Development%2520of%2520Embryo.doc+advantages+and+disadvantages+of+external+fertilization+and+internal+fertilization&cd=1&hl=en&ct=clnk&gl=us