Different Types Of Fertiliser
Soil amendments are made by adding fertiliser to the soil but there are different types of fertilisers. There is bulky organic fertiliser, such as cow manure, bat guano, bone meal, organic compost and green manure crops. And then there is also chemical fertiliser which is also referred to as inorganic fertiliser and is made up with different formulations to suit a variety of specified uses. Though many governments and agricultural departments go to great lengths to increase the supply of organic fertilisers, such as bulky organic manures and composting materials, there is just not enough of these fertilisers available to meet the existing and future fertiliser needs. Compared to organic compost, chemical or inorganic fertilisers also have the added advantage of being less bulky. Being less bulky makes chemical fertiliser easier to transport, both overland and from the soil into the plants itself, because they get to be available to the plant relatively quickly when incorporated as part of the plant-food constituents. Chemical fertiliser usually comes in either granular or powder form in bags and boxes, or in liquid formulations in bottles. The different types of chemical fertilisers are usually classified according to the three principal elements, namely Nitrogen (N), Phosphorous (P) and Potassium (K), and may, therefore, be included in more than one group.
Organic and Inorganic Chemical Nitrogenous Fertiliser types
This type of fertiliser is divided into different groups according to the manner in which the Nitrogen combines with other elements. These groups are:
- Sodium Nitrates,
- Ammonium Sulphate and ammonium salts,
- Chemical compounds that contains Nitrogen in amide form, and
- Animal and plant by products.
Sodium Nitrates are also known as Chilates or Chilean nitrate. The Nitrogen contained in Sodium Nitrate is refined and amounts to 16%. This means that the Nitrogen is immediately available to plants and as such is a valuable source of Nitrogen in a type of fertiliser. When one makes a soil amendment using Sodium Nitrates as a type of fertiliser in the garden, it is usually as a top- and side-dressing. Particularly when nursing young plants and garden vegetables. In soil that is acidic Sodium Nitrate is quite useful as a type of fertiliser. However, the excess use of Sodium Nitrate may cause deflocculation.
This fertiliser type comes in a white crystalline salt form, containing 20 to 21% ammonia cal nitrogen. It is easy to handle and it stores well under dry conditions. However, during the rainy season, it sometimes, forms lumps. (TIP: When these lumps do occur you should grind them down to a powered form before use.) Though this fertiliser type is soluble in water, its nitrogen is not readily lost in drainage, because the ammonium ion is retained by the soil particles. A note of caution: Ammonium sulphate may have an acid effect on garden soil. Over time, the long-continued use of this type of fertiliser will increase soil acidity and thus lower the yield. (TIP: It is advisable to use this fertiliser type together with bulky organic manures to safeguard against the ill effects of continued application of ammonium sulphate.)
The application of Ammonium sulphate fertiliser can be done before sowing, at sowing time, or even as a top-dressing to the growing crop. Do however take care NOT to apply it along with, or too close to, the seed, because in concentrated form, it affects seed germination very adversely.
This fertiliser type also comes in white crystalline salts. Ammonium Nitrate salts contains 33 to 35% nitrogen, of which half is nitrate nitrogen and the other half in the ammonium form. As part of the ammonium form, this type of fertiliser cannot be easily leached from the soil. This fertiliser is quick-acting, but highly hygroscopic thus making it unfit for storage. (TIP: Coagulation and Granulation of this fertiliser can be combated with a light coating of the granules with oil.) On a note of caution: Ammonium Nitrate also has an acid effect on the soil, in addition this type of fertiliser can be explosive under certain conditions, and, should thus be handled with care.
‘Nitro Chalk‘ is the trade name of a product formed by mixing ammonium nitrate with about 40% lime-stone or dolomite. This fertiliser is granulated, non-hazardous and less hygroscopic. The lime content of this fertiliser type makes it useful for application to acidic garden soils.
Ammonium Sulphate Nitrate
This fertiliser type is available as a mixture of ammonium nitrate and ammonium sulphate and is recognizable as a white crystal or as dirty-white granules. This fertiliser contains 26% nitrogen, three-fourths of it in the ammoniac form and the remainder (i.e. 6.5%) as nitrate nitrogen. Ammonium Sulphate Nitrate is non-explosive, readily soluble in water and is very quick-acting. Because this type of fertiliser keeps well, it is very useful for all crops. Though it can also render garden soil acidic, the acidifying effects is only one-half of that of ammonium sulphate on garden soil. Application of this fertiliser type can be done before sowing, at sowing time or as a top-dressing, but it should not be applied along the seed.
This fertiliser type comes in a white crystalline compound, which contains a good physical condition and 26% ammoniac nitrogen. In general, Ammonium Chloride is similar to ammonium sulphate in action. (TIP: Do not use this type of fertiliser on crops such as tomatoes because the chorine may harm your crop.)
This type of fertiliser usually is available to the public in a white, crystalline, organic form. It is a highly concentrated nitrogenous fertiliser and fairly hygroscopic. This also means that this fertiliser can be quite difficult to apply. Urea is also produced in granular or pellet forms and is coated with a non-hygroscopic inert material. It is highly soluble in water and therefore, subject to rapid leaching. It is, however, quick-acting and produces quick results. When applied to the soil, its nitrogen is rapidly changed into ammonia. Similar to ammonium nitrate, urea supplies nothing but nitrogen and the application of Urea as fertiliser can be done at sowing time or as a top-dressing, but should not be allowed to come into contact with the seed.
This fertiliser type is a gas that is made up of about 80% of nitrogen and comes in a liquid form as well because under the right conditions regarding temperature and pressure, Ammonia becomes liquid (anhydrous ammonia). Another form, ‘aqueous ammonia‘, results from the absorption of Ammonia gas into water, in which it is soluble. Ammonia is used as a fertiliser in both these forms. The anhydrous liquid form of Ammonia can be applied by introducing it into irrigation water, or directly into the soil from special containers. Not really suitable for the home gardener as this renders the use of ammonia as a fertiliser very expensive.
Organic Nitrogenous Fertilisers
Organic Nitrogenous fertiliser is the type of fertiliser that includes plant and animal by-products. These by-products can be anything from oil cakes, to fish manure and even to dried blood. The Nitrogen available in organic nitrogenous fertiliser types first has to be converted before the plants can use it. This conversion occurs through bacterial action and is thus a slow process. The upside of this situation is that the supply of available nitrogen lasts so much longer AND the amounts of this type of fertiliser may contain small amounts of organic stimulants that contain other minor elements that might also be needed by the plants that are being fertilized. Furthermore, they may also small amounts of organic stimulants that they may contain, or of some of the minor elements needed by plant. Oil-cakes contain not only nitrogen but also some phosphoric and potash, besides a large quantity of organic matter. This type of fertiliser is used in conjunction with quicker-acting chemical fertilisers.
Then there is also blood meal which contains 10 to 12% highly available Nitrogen as well as 1 to 2% Phosphoric acid. Blood meal, used in much the same way as oilcakes, makes for a quick remedy and can effectively be used on all types of soil as a type of fertiliser.
Fish meal which can be dried fish, fish-meal or even powder is extracted in areas where fish oil is extracted. The resulting residue is used as a fertiliser type. Obviously depending on the type of fish used, the available Nitrogen can be between 5 and 8% and the Phosphoric content can be from 4 to 6%. Fish meal also constitutes a fast-acting fertiliser type which is suitable for most soil types and crops. (TIP: In powder form it is at its best.)
Organic and Inorganic Chemical Phosphate Fertiliser Types
The Phosphate fertilisers are categorized as natural phosphates, either treated or processed, and also by products of phosphates and chemical phosphates.
As a type of fertiliser, rock phosphate occurs as natural deposits in some countries. This fertiliser type has its advantages and disadvantages. The advantage is that with adequate rainfall this fertiliser results in a long growing period which can enhance crops. Powdered phosphate fertiliser is an excellent remedy for soils that are acidic and has a phosphorous deficiency and requires soil amendments.
However, the disadvantage is that although phosphate fertiliser such as rock phosphate contains 25 to 35% phosphoric acid, the phosphorous is insoluble in water. It has to be pulverized to be used as a type of fertiliser before rendering satisfactory results in garden soil. Thus it is not surprising that Rock Phosphate is used to manufacture superphosphate which makes the Phosphoric acid water soluble.
Superphosphate is a fertiliser type that most gardeners are familiar with. As a fertiliser type one can get superphosphate in three different grades, depending on the manufacturing process. The following is a short description of the different superphosphate fertiliser grades:
- Single superphosphate containing 16 to 20% phosphoric acid;
- Dicalcium phosphate containing 35 to 38% phosphoric acid; and
- Triple superphosphate containing 44 to 49% phosphoric acid.
Triple superphosphate is used mostly in the manufacture of concentrated mixed fertiliser types.
The greatest advantage to be had of using Superphosphate as a fertiliser is that the phosphoric acid is fully water soluble, but when Superphosphate is applied to the soil, it is converted into soluble phosphate. This is due to precipitation as calcium, iron or aluminium phosphate, which is dependent on the soil type to which the fertiliser is added, be it alkaline or acidic garden soil. All garden soil types can benefit from the application of Superphosphate as a fertiliser. Used in conjunction with an organic fertiliser, it should be applied at sowing or transplant time.
Basic slag is a by-product of steel mills and is used as a fertiliser to a lesser extent than Superphosphate. Slag is an excellent fertiliser that can be used to amend soils that are acidic because of its alkaline reaction. For slag application to be an effective fertiliser it has to be pulverized first.
Bonemeal as a fertiliser type needs no introduction. Bone-meal is used as a phosphate fertiliser type and is available in two types: raw and steamed. The raw bone-meal contains 4% organic Nitrogen that is slow acting, and 20 to 25% phosphoric acid that is not soluble in water. The steamed bone-meal on the other hand has all the fats, greases, nitrogen and glue-making substances removed as a result of high pressure steaming. But it is more brittle and can be ground into a powder form. In powder form this fertiliser is of great advantage to the gardener in that the rate of availability of the phosphoric acid depends on its pulverization. This fertiliser is particularly suitable as a soil amendment for acid soil and should be applied either at sowing time or even a few days prior to sowing. (TIP: As a fertiliser type, bone-meal is slow acting and should be incorporated into the soil and not as a top-dressing.)
Organic and Inorganic Chemical Potassium Fertiliser types
Chemical Potassium fertiliser should only be added when there is absolute certainty that there is a Potassium deficiency in your garden soil. Potassium fertilisers also work well in sandy garden soil that responds to their application. Crops such as chilies, potato and fruit trees all benefit from this type of fertiliser since it improves the quality and appearance of the produce. There are basically two different types of potassium fertilisers:
- Muriate of potash (Potassium chloride) and
- Sulphate of potash (Potassium sulphate).
Both muriate of potash and sulphate of potash are salts that make up part of the waters of the oceans and inland seas as well as inland saline deposits.
Muriate Of Potash
Muriate of potash is a gray crystal type of fertiliser that consists of 50 to 60% potash. All the potash in this fertiliser type is readily available to plants because it is highly soluble in water. Even so, it does not leach away deep into the soil since the potash is absorbed on the colloidal surfaces. (TIP: Apply muriate of potash at sowing time or prior to sowing.)
Sulphate Of Potash
Sulphate of potash is a fertiliser type manufactured when potassium chloride is treated with magnesium sulphate. It dissolves readily in water and can be applied to the garden soil at any time up to sowing. Some gardeners prefer using sulphate of potash over muriate of potash.
Different Types of Fertilisers
The different types of fertilisers with all its specifications and cautions that should be kept in mind should not detract us from the joys of gardening. Thus to make it easier on most gardeners and since this website is dedicated to the home gardener and growing our own gardens the following section is geared towards the home gardener.
The different types of chemical and organic fertilisers that are usually commercially available in most countries can be categorized further into:
- Complete inorganic fertilisers: – these types of inorganic fertilisers contain all three major macronutrients, Nitrogen (N), Phosphorous (P) and Potassium (K). On the containers you will find that these macronutrients are depicted as a ratio, e.g. 2:3:2 (22). Complete inorganic fertilisers are usually applied at a rate of 60g/m2 or roughly 4 tablespoons per square meter.
- Special purpose fertiliser: – these types of fertiliser are formulated especially to target certain plants’ requirements or certain soil deficiencies. Of the examples that come to mind here are the Blue Hydrangea Food, and straight fertiliser that is made up of one particular plant nutrient for example lawn fertiliser.
- Liquid fertilisers: – these types of fertiliser come in a variety of formulations and even include organic fertiliser, complete fertiliser as well as special purpose fertiliser. Some examples of liquid fertiliser are Nitrosol and African Violet Food.
- Slow-release fertiliser: – these types of fertiliser are formulated to release their nitrogen at a steady pace. On the packs of this fertiliser that are available commercially it will usually be depicted as 3:1:5 (SR) where the SR indicates slow-release.
- Fertiliser with insecticide: – these types of fertiliser that are prepared and combined with an insecticide. One such example is Wonder 4:1:1 (21) + Karbaspray.
The reason why there are so many different types of chemical fertilisers in different formulations is because different plants require different nutrients and different pH levels in the soil. However, organic fertilisers have more diversity, and these types of fertilisers do not burn plant roots, get into ground water, or affect surrounding growth as is the case when using the different types of chemical fertiliser and NPK amendments.