Fertilisers

Fertilisers are compounds of different nutrients given to plants with the intention of promoting growth; they are usually applied via the soil, for uptake by plant roots. Their primary purpose is to increase the rate at which photosynthesis occurs in different types of crops. To do this they add three major plant nutrients, potassium, nitrogen and phosphorus, as well as several secondary plant nutrients like calcium, magnesium and sulphur. 1 There are two different types of fertilisers. The first and the one in longest use is organic fertiliser.

The most popular organic fertiliser is manure, which is made by compacting different layers of faeces, urine, hay, dirt and several other nutritious ingredients. The drawbacks with using organic fertilisers are that there is no means of telling how much of what nutrient is present. They also compete with heavy machinery which produces their Chemical counterpart. Inorganic fertilisers, however, are created by a factorial process and each selection of fertiliser contains the same amount of nutrients as another sample.

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They are measured using a three element scale, NPK. NPK fertilisers can be manufactured with different percentages of each nutrient; 5-10-5 for example would have ten percent phosphate in its ingredients. Nitrogen is a primary compound in fertilisers and is also counted as a hazard to the environment. Nitrogen accelerates eutrophication, which is the excessive surface runoff of easily soluble nutrients often pollutes lakes and streams. Eutrophication, in simple, speeds up the growth of plant-life.

The way eutrophication is caused is when crops which are relatively close to streams and lakes, are flooded. Inorganic fertiliser is more susceptible to being dispersed, and the water in rainfall is capable of transporting it to the nearest river source. The river would then run it into a lake or pond. These are often found in the form of nitrates. Calcium, sodium and potassium and ammonium nitrates are used in fertilisers to provide the nitrogen a plant needs. When the fertiliser is in the water, the water is virtually undrinkable, and labelled as poisonous.

The fertiliser then speeds up the growth of pond plant-life, and in particular, algae, which floats on top of the water and blocks out the sunlight to other plants underneath the water level. The algae then die and remain on the surface. Bacteria begin to decompose the dead plants and use up the remaining oxygen. This causes the underwater plant-life as well as the other wildlife like fish, to die for lack of oxygen. 4 Phosphates are used in fertilisers also. They are products formed by the replacement of some, or in some case all, of the hydrogen of a phosphoric acid by metals.

Depending on the quantity of hydrogen atoms that are replaces, the resulting compound is referred to as a primary, secondary or tertiary phosphate. Phosphates are important to metabolism in both animals and plants. Primary calcium phosphate (Ca(H2PO4)2) is the ingredient of numerous plant fertilisers. When it is used as part of a fertiliser, if can be washed into waterways by the rain and pollute rivers and streams in the way mentioned above. Potassium (K) has several general functions.

These mainly consist of the carbohydrate and protein synthesis that are necessary for the activation of numerous enzyme functions. Potassium, for this reason, is important during most stages of growth. When it comes to dispersion, organic fertilisers have a harder time because they’re compressed into large clumps. Breaking up these lumps may be done to spread out the fertiliser further. However, one piece may have an unbalanced amount of nutrients. Inorganic fertilisers excel at this because they are easily distributed, since they are smaller and granular.

They also contain the same proportion of nutrients per granule. 3 The drawback with being dispersible is the capability to still be able to be moved around after it has been scattered across the fields. As mentioned above, rainfall is easily able to whisk away the inorganic fertiliser and take it to a nearby water source. Scientists are working on a means to get plants to create their own source of nitrogen, which would mean farmers could dispense with using inorganic nitrogen fertilisers, which also in turn would mean less eutrophication in nearby water sources.

This operation to genetically engineer plants to make their own source of nitrogen is also a cause for concern because it plans to use the herbicide (plant killer) 2,4-D – 2,4-Dichlorophenoxyacetic acid (C8H6Cl2O3) is usually used in the control of weeds such as the broadleaf. 2,4-D is a herbicide which has acute gaps in the research fields concerning human responses. It has been classed as ‘moderately hazardous’ due to experiments proving it to have a LD50 title. (LD50 standing for Lethal Dose, 50%) 5 / 7 Research shows that the nitrogen input into the soil by fertilisers has become increasing irregular.

Farmers nowadays tend to add fertiliser for the sake of producing a larger yield. Scientific studies have proven that nitrogen-containing fertilisers are being over-used at times where they are no longer needed. This usually leads to eutrophication of water ways. The application of nitrogen when crops do not need it gets absorbed by the pests in the soil. Pests include plants, bacteria and other organisms. The increase in nitrogen allows them to reproduce/replicate at a faster rate near the plant, thus becoming a parasite. Organic fertilisers are intrinsically different in many ways, a lot of them mentioned above.

But one of the most crucial ways it is different to inorganic is that is requires the presence of soil micro life, such as different bacteria and fungi, to break the fertiliser down and convert them into the chemical form that is usable by the plants. 6Inorganic fertilisers do not just feed the plant. It can also feed the soil microbes in addition to the crop/plant in question. The ammonium in the fertilisers created chemically can be a hazard to some of the soil’s micro life, for instance earthworms. Chemists and researchers are inventing something called ‘biobeads’ which can be placed in moist soil.

Bacteria convert the ore into bio-available phosphates which then slowly gets absorbed by the soil. This reduces the chances of excess phosphates leeching into rivers, lakes and other forms of groundwater. The final and more financial impacting effect of all is that chemical fertilisers can be produced on demand; where as organic fertilisers have to be produced naturally over the course of a few months. 2 Should an argument be raised as to which are the more beneficial with the least negative effects on the environment, Organic Fertilisers would be my choice.

As stated clearly before, Fertiliser run-off can cause water to become eutrophic (nutrient rich body of water). While this is a common and lethal blow to the environment, it is far more popular with fertilisers whom have had nutrients artificially implanted within the actual fertiliser. Since organic fertiliser contains a low amount of this (some having been ingested through animals), they would cause the soil to be less eutrophic. In addition, the weight of organic fertiliser will reduce the run-off due to the bulk of it. 8

However, in terms of product output of the cereal crops, Inorganic fertilisers are more efficient due to the fact that organic fertiliser cannot be created in the quantities needed to fertilise the crops needed to feed our ever-growing population, and although inorganic has several major hazards to its use, scientists are always coming up with different ways to counteract the leeching and poisoning which is a result of natural events such as rainfall. This combined with individual scientific research is increasing the popularity of inorganic fertiliser.

Sources

http://en.wikipedia.org/wiki/Fertilisers

http://www.westsidegardener.com/guides/whyorganicfertilizer.html

http://www.newscientist.com/article/mg16321972.200.html

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