STRUCTURE

• Introduction – What are manures and fertilizers (15 words)                     
• Body – Explain
  • Difference between manures and fertilizers with suitable examples (120 words)
  • Classification of nitrogenous fertilizers based on the form of nitrogen present in N-fertilizers(120 words)
• Conclusion – Mention a short conclusion  (15 words)

ANSWER

Manuring is the process of addition of natural or chemical sources of nutrients for the crop. Natural sources include dead wastes of plants, humans and animals, excreta and other wastes. These on decomposition give organic products called organic manure or simply manure.

Manure improves the water holding capacity, aeration, and texture of the soil. These lead to the development of a new method of farming called organic farming where only organic fertilizers, pesticides, etc. are used.

Fertilizers are chemical compounds which include salts or organic compounds like urea, ammonium sulfate, sodium nitrate etc. They are the sources of plant nutrients like potassium, nitrogen, and phosphorus. Fertilizers are commercial products mainly manufactured in factories. They have enhanced the yield spontaneously.

Chemical fertilizers should be used in optimum amount with great care. Their excess use may lead to soil infertility, water pollution, and even cause disease. Overall, it damages the crop. Hence it is advisable to use organic manure instead of chemical fertilizers.

Following are the important difference between fertilizer and manure:

TYPES OF NITROGENOUS FERTILIZERS

Nitrate Fertilizers:

Of the nitrate fertilizers the most common in use is sodium nitrate or calcium nitrate.

(a) Nitrate group of fertilizers are soluble in water and hygroscopic (absorbs moisture from the atmosphere to become sticky).

(b) They are alkaline in nature. Especially the constant use of sodium nitrate, creates de-flocculation of clay particles and poor drainage.

(c) Contains less percentage of nitrogen than other groups so that its use is diminishing at a fast rate.

(d) They are completely soluble in water and. readily available for the use of plants as such, without any chemical change in the soil.

(e) The nitrate is not retained (adsorbed) by the soil and is liable to fast leaching.

(f) They are applied in small doses and repeated at intervals on standing crops (top dressing).

(g) If so use is not suitable for rice crop in early stage of growth. Because rice plants take nitrogen in ammonical form.

Ammonium Fertilizers:

This group of fertilizers are in wide use particularly ammonium sulphate.

(a) Ammonium fertilizers are soluble in water but not hygroscopic.

(b) They are acidic in nature.

(c) High level of nitrogen than nitrate fertilizers.

(d) They are less readily available to plants than nitrate fertilizers. The ammonical 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 which can utilize the ammonical nitrogen and in all cases nitrification has to take place before it can be utilized.

(e) 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.

(f) This group of fertilizers may be used in basal application and top dressing.

NITRATE AND AMMONIUM FERTILIZERS:

(a) These group of fertilizers are soluble in water and slightly hygroscopic (e.g., Ammonium Nitrate highly hygroscopic; Ammonium Sulphate Nitrate slightly; Calcium Ammonium Nitrate slightly).

(b) In this group both nitrate and ammonium are available.

(c) Readily available to plants. With its nitrate-nitrogen, the plant drives it immediately. Ammonium form of nitrogen provides a steady source of N.

(d) Availability of ammonium reduces leaching loss.

(e) Acidic in nature but exception is calcium ammonium nitrate which is neutral in reaction.

(f) Used in top dressing and basal dressing.

AMIDE FERTILIZERS

(a) Amide fertilizers are soluble in water and hygroscopic in nature.

(b) These fertilizers are converted to ammonium carbonate and then to nitrates due to action of microorganism. The conversion of amides into ammonical and nitrate form takes about 6-7 days.

(c) 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.

Types :

(i) Urea:

It is slightly acidic in nature. Urea application to soil creates a small loss of calcium from the soil. Urea is highly concentrated nitrogenous fertilizer containing 46% nitrogen. Therefore, its higher concentration may injure the plant roots or germinating seeds.

It is desirable that urea be mixed with ashes or small quantity of soil to facilitate an even distribution to avoid risk of injury to plants. It is cheapest or economical fertilizer. It can be used in liquid form as foliar application.

(ii) Calcium Cynamide:

It is non-leachable, synthetic organic fertilizer. Its basicity (alkalinity) is three times as high as that of sodium nitrate, and is advisable for use on acid soils. Cynamide is applied in the soil, at least 7-10 days prior to sowing. Certain intermediary compounds formed during its decomposition injure tender and germinating seedlings.