There are 4 types of nitrogenous fertilizers. They are; Nitrate Fertilizers, Ammonium Fertilizers, Nitrate and Ammonium Fertilizers, and Amide Fertilizers. There are many uses and many harmful effects of nitrogenous fertilizers. Fertilizers can create a great increment in the production of crops and fruits but can also degrade the condition of the soils. Continuous use of fertilizers can make the soil infertile.
Plants need nutrients for their growth. Such nutrients are present in the soil. The fertility of soil depends in part on the presence of certain chemical elements. These elements are nitrogen, phosphorus, and potassium, together with traces of iron, Sulphur, and others. These elements which are needed in greater amounts for plants are known as primary nutrients or macronutrients. Nitrogen, phosphorous and potassium are examples of primary nutrients. Plants also utilize some elements in very small amounts which are known as secondary nutrients or micronutrients. Boron, iron, zinc, manganese, etc. are examples of secondary nutrients. Fertilizers that are synthesized in laboratories are known as chemical fertilizers. They are a class of substances that are added to the soil to remove its deficiency of essential nutrients required by the plants for their proper and healthy growth. Chemical fertilizers are synthetic fertilizers that improve the growth and productiveness of plants. Fertilizers enhance the natural fertility of the soil or replace the chemical elements taken from the soil by previous crops. Without fertilizers, the soil would be depleted and therefore plants would be particularly difficult to grow.
Fertilizers can be differentiated into the following four main types:
1. Nitrogenous fertilizers
2. Phosphorous fertilizers
3. Potash fertilizers
4. Mixed fertilizers
However, in this project, we will only be studying and presenting nitrogenous fertilizers.
Simply, the fertilizers in which there is the presence of nitrogen or the fertilizer which mainly supply nitrogen are considered as nitrogenous fertilizers. Nitrogen is considered to be the most important nutrient, and plants absorb more nitrogen than any other element. Nitrogen fertilizer imparts dark green color to the plants. It is used for the rapid growth of the plants, increase in protein content, and production of green coloring matter. Harsh fibrous leaves are the symptom of nitrogen deficiency in plants. The common types of nitrogenous fertilizers are as follows:
a. Nitrate Fertilizers
b. Ammonium Fertilizers
c. Nitrate and Ammonium Fertilizers
d. Amide Fertilizers
a. Nitrate Fertilizers Nitrate group of fertilizers are soluble in water and hygroscopic (absorbs moisture from the atmosphere to become sticky). They are alkaline in nature. Especially the constant use of sodium nitrate creates de-flocculation of clay particles and poor drainage. Contains less percentage of nitrogen than other groups so that its use is diminishing at a fast rate. They are completely soluble in water and. readily available for the use of plants as such, without any chemical change in the soil. The nitrate is not retained (adsorbed) by the soil and is liable to fast leaching. They are applied in small doses and repeated at intervals on standing crops (top dressing). If so use is not suitable for rice crops in the early stage of growth. Because rice plants take nitrogen in ammonia form. Nitrates are chiefly produced to be used as fertilizers in agriculture because they have high solubility and biodegradability. The main nitrate fertilizers are Sodium salts, Potassium salt, and Calcium salt.
b. Ammonium fertilizers This group of fertilizers is in wide use particularly Ammonium Sulphate. Ammonium fertilizers are soluble in water but not hygroscopic. They are acidic in nature. High level of nitrogen than nitrate fertilizers. They are less readily available to plants than nitrate fertilizers. The Ammoniacal Nitrogen has to nitrify in the soil and be converted into nitrate before it can be taken up by plants. The Nitrification of Ammonium is not rapid in temperate regions and it is not considered to be so quick-acting as Sodium Nitrate. Rice is the only crop that can utilize Ammonical nitrogen and in all cases, nitrification has to take place before it can be utilized. The Ammonia in Ammonium Sulphate is fixed (adsorbed) by the soil immediately after application and it is not leached away like nitrates. During fixation, Ammonia releases an equivalent quantity of calcium from the soil and the application of ammonium (e.g., Ammonium Sulphate) reduces the quantity of reserve calcium in the soil. Repeated and heavy doses of Ammonium Sulphate without adequate supplies of lime in the soil will lead to acidity in the soil. This group of fertilizers may be used in the basal application and top dressing. The common Ammonium fertilizer is ammonium salt.
c. Nitrate and Ammonium Fertilizers: These groups of fertilizers are soluble in water and slightly hygroscopic (e.g., Ammonium Nitrate highly hygroscopic; Ammonium Sulphate Nitrate slightly; Calcium Ammonium Nitrate slightly). In this group both Nitrate and Ammonium are available. Readily available to plants. With its Nitrate-Nitrogen, the plant drives it immediately. Ammonium form of nitrogen provides a steady source of N. Availability of Ammonium reduces leaching loss. Acidic in nature but the exception is calcium Ammonium Nitrate which is neutral in reaction. Used in top dressing and basal dressing. The best example of an Ammonical Nitrate Fertilizer is Calcium Ammonium Nitrate.
d. Amide Fertilizers: Amide fertilizers are soluble in water and hygroscopic in nature. These fertilizers are converted to ammonium carbonate and then to nitrates due to the action of microorganisms. The conversion of amides into Ammonical and Nitrate form takes about 6-7 days. Leaching loss is very less because once amide is converted to Ammonical form it is adsorbed by soil colloids and slowly released and Nitrified to nitrates. Amide fertilizers i.e., Urea and Calcium Cyanamide are synthetic organic fertilizers. The usefulness of fertilizers can be as:
1. Fertilizers increase the production of crops and fruits.
2. They increase the fertility of the soil for a certain period of time.
3. They reduce soil erosion in some cases.
4. Some of the nitrogenous fertilizers keep the soil hydrated. However, some nitrogen salts don’t keep it hydrated.
The harmful effects of fertilizers can be explained as follows:
Though chemical fertilizers increase crop production; their overuse has hardened the soil, decreased fertility, strengthened pesticides, polluted air and water, and released greenhouse gases, thereby bringing hazards to human health and the environment as well. It has already been proved how chemical fertilizers pose serious challenges to balanced and sustainable growth. Continuous use of these chemical fertilizers depletes essential soil nutrients and minerals that are naturally found in fertile soil. When we use chemical fertilizers; they do not help replenish soil nutrients and their fertility contrary to the popular belief; but, replenish only nitrogen, potassium, and phosphorous. Though chemical fertilizers will help plants grow faster; plants will not be healthy and strong as plants grown in that manner do not have enough time to mature to develop good root growth, strong stems, or nutritious fruits and vegetables. Even they will be less likely to survive because they will be more susceptible to pests and diseases as they lack a good immune system and enough resistance against these forces. Besides this, chemical fertilizers can cause root burn or fertilizer burn, as chemical fertilizers do not allow enough water intake for the plants. Chemical fertilizers are high in nitrogen salts, and when the nitrogen is absorbed by soil too quickly; it will dehydrate and dry up the plant. Another important issue of using nitrogen fertilizers is groundwater contamination. Nitrogen fertilizers break down into nitrates and travel easily through the soil. Because it is water-soluble and can remain in groundwater for decades, the addition of more nitrogen over the years has an accumulative effect. The addition of the various fertilizers influenced or significantly influenced (p < 0.05) the EC of the potted soils collected at the end of the experiment. Relative to the CK soil, the application of various fertilizers raised the EC of the soils to different levels, and the soil treated with CF400 had the highest EC value (1.21 dS·m−1) of all the treatments. Although the EC values were lower than the threshold of saline soil, i.e., EC (w/v = 1/1) = 2.4 dS·m−1, the applied fertilizers amounts should be controlled to avoid additional salt accumulation. The treatment with OM200 + LF and OM400 + LF increased the EC of the soil from 0.22 dS·m−1 (CK) to approximately 0.75 dS·m−1. Higher EC values could potentially decrease the water potential of the soil water and thus inhibit plant growth. The organic fertilizer and liquid fertilizer have higher EC values, which may increase soil EC and thus affect plant growth after the fertilizers are applied to the land.