What Is Fertilizer?


Agriculture is one of the major professions for many people all over the world. Agriculture is the key to sustain life on earth. fertilizer, manure, and soil fertility management have become the need of the hour.

We, human beings solely depend on agriculture to satisfy all our daily food needs. Thus agriculture is one of the reasons why we have the liberty of choosing so many food types and flavors.

Are you aware of the several factors in agriculture that provide us with disease-free and nutritious food? It is a fact that plant species require eighteen essential elements for its growth.

Out of the eighteen elements, only three elements are readily available to plants. These three elements are air, sunlight, and water. For the rest of the fifteen elements, the plant depends entirely on the soil.


These 15 elements are minerals. Every soil type requires the potential and capacity to provide all these nutrients that are necessary for proper plant growth.

Continuous exploitation of the soil takes place around the year. By the cultivation of a single crop or intercultural operations, the soil becomes infertile.

These practices also lead to reduced nutrient content in the soil. Therefore is necessary that every farmer should keep the soil rich in nutrients and minerals.

This is possible by applying appropriate manures and fertilizers.

All these practices also promote sustainable agriculture. Thus manures and fertilizers have become an essential entity of modern-day agriculture. They help in maintaining soil fertility.

Now, let us see about manure, fertilizer and soil fertility management one by one in detail.

Fertilizer Definition

Fertilizers are the materials of natural or synthetic origin. They have a definite chemical composition that enhances their ability to supply the required nutrients to the soil.

Basically, fertilizer consists of inorganic components excluding urea and calcium cyanamide. Based upon the number of nutrients, fertilizers have three categories.

They are straight, complex and mixed fertilizers. Straight fertilizers consist of a single chemical compound that acts as the primary nutrient. Complex fertilizers have more than one nutrient, whereas mix fertilizers are a combination of straight and complex fertilizers.

Now let us discuss the difference between manures and fertilizers.

Objective and Uses of Fertilizers.

The objective of manuring the soil, whether, with stable manure, green manure or commercial fertilizers is simple. The objective is to increase crop-yielding capacity.

In order to justify the practice, the resulting increase in products must be more than sufficient to offset the cost of manures or fertilizers applied.

Types of Fertilizer

In discussing the subject of fertilizers the terms manures, complete and incomplete manures, fertilizers, chemical fertilizers, commercial fertilizers, natural fertilizers, artificial fertilizers, indirect fertilizers, superphosphate, etc., are familiar. But there is often a misunderstanding of the meaning of some of these terms.

Fertilizers are first divided into natural and artificial.

Natural Fertilizer

Natural fertilizer includes all the solid and liquid excrement of animals and green manuring crops when plowing under for the benefit of the soil.

Artificial Fertilizer

Artificial fertilizers include all commercial forms of fertilizers. These are sometimes known as prepared fertilizers and chemical fertilizers. But are becoming more generally known as commercial fertilizers.

A complete fertilizer contains the three essential plant-food constituent nitrogen, phosphorus, and potassium. An incomplete fertilizer contains only one or two of these. All animal manures are complete fertilizers. Green manures are likewise complete.

Direct and Indirect Fertilizers

A fertilizer is indirect when it contains none of the essential plant-food elements, but in some way sets on the soil so as to increase the availability of plant food in the soil or increase crop growth.

Lime, gypsum, salt and numerous other substances have been found to have this action and would be classed as indirect fertilizers.

High Grade and Low-Grade Fertilizers

The terms high-grade and low-grade are also applicable to fertilizers. These terms, however, have no proper definition. High-grade fertilizers generally contain large amounts of plant food per ton, while low-grade fertilizers contain relatively small amounts.

Another distinction that is sometimes made is that fertilizers manufactured out of high-grade constituents, such as nitrate of soda, acid phosphate, and muriate or potassium sulfate are considered high-grade fertilizers regardless of the percentage of the elements.

A high-grade fertilizer always costs more per ton than a low-grade one. But it is generally true that the elements in such a fertilizer come cheaper to the farmer than they do in a low-grade material.

Whether it is more economical to purchase high-grade or low-grade material is an important question, but the answer is not difficult.

All fertilizers should be bought on the basis of their content of available plant food, and it is merely a problem in arithmetic to calculate the relative cost of the elements in the different grades of fertilizers.


Manure is the material we obtain from organic wastes and crop residues. Its composition is free of chemicals.

Thus manure is of organic nature. It provides various nutrients to the plants. In addition, manure also contributes to improving the physical, chemical and biological properties of the soil.

The categorization of manure depends upon the concentration of plant nutrients that it provides. Manure is basically of two types, bulky organic manure, and concentrated organic manure.


Bulky organic manure contains minimal amounts of nutrients. It is needed in large quantities. Some of the examples are farmyard manures, green manures, vermicompost, and sludge.

Concentrated organic manure has high amounts of plant nutrients as compared to the bulky organic manures. So their requirement is very minimal. Some examples are oil meals, bone meal, feather meal, blood meal, etc.

Importance Of Organic Manure as Fertilizer

Organic manure is easily available in all climatic conditions. Organic manure easily reacts with the soil.

Animal manure is a form of organic manure. You can easily prepare it from the slurry. This slurry is easily available in agricultural lands. They can also be used as fuel. An example is cow dung.

Organic manure increases the fertility of the soil and maintains the balance of soil fertility. Moreover, traditional organic manure is challenging modern-day fertilizer.

Difference Between Fertilizer and Manure

It is necessary to know the difference in order to apply them based on cultivational requirements.

The major difference between manure and fertilizer is manure is of natural origin whereas the fertilizers are of synthetic origin. Manure is economical to use. Whereas fertilizers are very costly.

Organic manure contains all the essential nutrients, whereas fertilizers contain only the specific nutrients. Although manures have all the essential nutrients, it contains relatively small amounts of plant nutrients. Whereas fertilizers are rich in specific plant nutrients.

Since manure is of natural origin, it does not have harmful effects on living organisms present in the soil. While fertilizers, if used in excess, will create problems for living organisms due to their synthetic origin. Both manure and fertilizers are essential to maintain soil fertility.

Soil Fertility Management Via Fertilizers

The ability of the soil to accept, store and transfer energy in order to support the growth of plants is soil fertility. The study that deals with the management of the physical, chemical and biological composition of soil to know its current nutrient status is soil fertility management.

It also includes analyzing the soil to provide nutrients and essential elements. It generally deals with the methods that are concerned with soil conservation, crop rotation and application of manure and fertilizer as per the soil requirements.

Thus soil fertility management has become a vital component in the growth of various crops around the world.

Let us have a look at some generally used fertilizers.

Nitrogen Fertilizer

Nitrate of soda (NaNO,) contains 15 percent of nitrogen. It is readily soluble in water, and nitrogen in this form becomes immediately available for plants.

It should be applied in small quantities and just a few days before you start planting.

Ammonium sulfate (NH) SO, contains 20 per cent of nitrogen. Like nitrate of soda, it is quick-acting. But for most crops, the ammonia must first be converted into the nitrate form before it can be utilized. Some crops, however, can utilize ammonia as it is.

Ammonium Sulfate

Ammonium sulfate is not leached from the soil quite as rapidly as nitrate of soda, but nevertheless, it should not be applied in larger amounts.

Cottonseed meal is another source of nitrogen which is extensively 9 to 14 percent nitrogen, with an average of about 6.8 percent. It is not wholly a nitrogenous fertilizer since it also contains an average of 2.9 percent phosphorus and 1.8 percent potash.

The nitrogen in cottonseed meal being in organic form is rather slowly available. Availability is gradually brought about through decomposition.

Tankage contains nitrogen in variable quantities, ranging from 5 to 12 percent. It may also contain from 7 to 20 percent of phosphoric acid. The nitrogen in tankage is slowly available to the soil.

Phosphorus as Fertilizer

Phosphorus is available in the form of acid phosphate, which contains 14 to 16 percent of phosphoric acid and also 6 to 7 percent of phosphorus. Most of the phosphorus is available directly to the soil.

Acid phosphate manufacturing is possible by treating a given bulk of finely pulverized phosphate rock with an equal weight of etude commercial sulphuric acid. The reaction makes the phosphorus available.

This material is the main basic product to manufacture commercial fertilizers.

Phosphoric acid costs from four to five cents per pound in acid phosphate, depending on the location and size of purchases. (As this goes to press, prices have advanced 25 to 30 percent. This advance is probably temporary.)

Rock Phosphate

There is now an increased tendency to make direct use of the rock phosphate in a finely pulverized form. Such rock contains the equivalent of 28 to 35 percent of phosphoric acid.

But it is in an insoluble form and can be economically put to use only on soils that are well supplied with organic matter. Or in conjunction with barnyard or stable manure and green manure crops.

The general use of raw rock phosphate has not been advisable on the soils of the eastern and southern parts of the United States.

On the other hand, the raw rock phosphate gives good results on the prairie soils of Indiana, Illinois, Iowa, and some other states. The cost of phosphoric acid in this form is equivalent to two cents per pound or a little less.

Basic slag, sometimes known as Thomas Phosphate, is a by-product of steel mill which is finely ground and used as a source of phosphorus.

It is similar to raw rock phosphate, slightly more available and contains the equivalent of 15 to 18 percent of phosphoric acid.

Bone Meal

There are two types of bone meal on the market, raw and steamed bone meal. The raw bone is fresh bone which is finely ground.

Rawbone contains about 20 percent of phosphoric acid and 4 percent of nitrogen. Fat and gelatin are removed with the help of steam. It contains only about 1 percent of nitrogen and 22 to 28 percent of phosphoric acid.

The steam bone is a finer powder form than the raw bone. Since the fat and gelatin are removable, it decomposes rapidly. And is, therefore, more readily available as plant food.

Blood Meal

Dried blood is also an organic source of nitrogen, containing on an average 10 percent of this element. It decomposes easily and somewhat more available than nitrogen in cottonseed meal.

Potassium Fertilizer

Potassium-Muriate of potash (KCl), the chief source of potash contains the equivalent of about 50 percent of potash (K20). It is the most common purified potash salt, consisting chiefly of potassium chloride.

It is a very satisfactory source of potash for all crops except tobacco and potatoes.

The chlorine is slightly detrimental to starch formation. And, for this reason, the sulfate and carbonate of potash are best for potatoes.

Potassium sulfate also contains the equivalent of 50 percent of potash (K2O). Kainite a low-grade material. It contains about 12 percent of potash. Wood ashes are also a source of potash.

They contain about 6 percent of this constituent, together with about 2 percent of phosphorous acid and a large amount of lime. The availability of the potash in ashes is rated as medium.


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