Nutrient management, Manures and Fertilisers

Question 1 What are macro and micro nutrients in plants? Give examples?

Question 2 Name the three most important nutrients needed for the growth of plant?

Question 3 From do the plants get carbon, oxygen and hydrogen?

Question 4 How do plants get nutrients?

Question 5 Differentiate between manures and fertilizers?

Question 6 What are the advantages and disadvantages of manures?

Question 7 Explain why a legume crop does not require nitrogenous fertilizer?

Question 8 Name two biofertilizers?

Question 9  What are the characteristics of an essential plant nutrient?

Question 10 What are Farmyard manures. Give example?

Question 11 What is Vermicomposting ?

Question 12 Name different types of fertilizers with example?

Improvement in Yields

Following three scientific approaches are adopted in India to obtain high yields:

1) Crop production management

2) Crop improvement for higher yield through genetic manipulation

3) Crop protection management

Crop Production Management

India has an endless growing season which means that crops can be grown throughout the year. This is because of the subtropical climate and lack of frost in most part of country. Besides providing food, agriculture is a source of raw materials for industries.

Farming practices are performed by three types of Indian farmers: small farmers, marignal farmers and progressive farmers. Such a categorisation of Indian farmers is done on the basis of following three criteria:

1) Land holdings of the farmers;

2) Financial conditions of the farmers; and

3) Use of modern technologies (such as tractor, combines, high-yielding seeds, fertilizers, insecticides and better means of irrigation) by the farmers.

Nutrient Management

The food required by plant is composed of certain chemical elements, which are known as nutrients. Though plants absorb a large number of elements from its environment. Only following sixteen (16) of these are found to be essential for the plant nutrition:

Carbon, Oxygen, Hydrogen, Nitrogen, Phosphorus, Potassium, Calcium, Magnesium, Sulphur, Iron, Manganese, Boron, Zinc, Molybdenum, Chlorine, Copper

Deficiency of these nutrients affect physiological processes in plants including reproduction, growth and susceptibility to disease.

Characteristics of an Essential Plant Nutrient

An element must fulfil the following requirements to be an essential plant nutrient:

1) In the absence of the element the plant is not able to complete its life cycle.

2) The deficiency of a particular element can be prevented or corrected only by supplying that nutrient.

3) The element must have a direct influence on the plant nutrition and metabolism.

Sources of Essential Plant Nutrients

There are three different sources from where a plant gets the 16 essential nutrient. These sources are air, water and soil.

Air :Carbon, Oxygen

Water : Hydrogen

Soil : Nitrogen, Phosphorus, Potassium, Calcium ,Magnesium, Sulphur, Iron, Manganese, Boron, Zinc, Copper, Molybdenum, Chlorine.

Thus, nutrients taken by plants from the soil are many more in number than those obtained from air and water (2 + 1 =3). 

Classification of Nutrients

The 13 nutrients needed for plant growth have been grouped into following two classes: macronutrients and micronutrients

Macronutrients: The essential elements which are utilised by plants relatively in large quantities, are called major nutrients or macronutrients.

For example: Nitrogen, Phosphorus, Potassium, Calcium, Magnesium, Sulphur

Of these six macronutrients only three namely nitrogen, phosphorus and potassium (i.e., N, P, K) are required by plants in greater amounts, they are called primary elements or primary nutrients

Micronutrients

The essential elements which are used by plants in small quantities (or traces) are called minor nutrients or micronutrients.

For Example: Iron, Manganese,  Boron, Zinc, Copper, Molybdenum, Chlorine.

Micronutrients may be required in small quantities but they are essential for plant growth as are the macronutrients.

Mode of Intake of Thirteen Essential Nutrients by the Plants

The 13 soil nutrients remain dissolved in water. They are absorbed by roots from the soil by the plants. The most important nutrients (elements) required for plant growth are nitrogen, phosphorus and potassium (NPK). NPK are primary plant nutrients, so if crop plants are grown in the same soil, year after year, then the primary nutrients present in the soil would go on decreasing more rapidly than other nutrients. Such a specific deficiency of nitrogen, phosphorus and potassium in the soil is recouped by adding chemical fertilisers and manures in the soil.

Manures and Fertilizers

The deficiency of plant nutrients and organic matter in the soil is made up by adding manures and fertilizers to the soil of crop-fields. Both manures and fertilizers are major sources of nutrients of plants, so they are used in crop production.

Manures

1) Manures are natural fertilizers.

2) They are bulky sources of organic matter which supply nutrients in small quantities. 

3) Manures are prepared by the decomposition of animal excreta and plant waste.

4) Manures include farmyard manure (FYM), compost, green manures, vermicompost.

Advantages of Manures

1) The manures enrich the soil with nutrients. They replenish the general deficiency of nutrients in the soil.

2) The manures add organic matter (called humus) to the soil which restores the soil texture for better retention of water and for aeration of soil.

3) The organic matter of manures provide food for the soil organisms (decomposers such as bacteria, fungi, etc.) which help in making nutrients available to plants.

4) Organic manures help to improve the physical properties of soil, reduce soil erosion, increase the moisture holding capacity of soil.

5) They are low cost nutrient carriers.

Disadvantages of Manures

1) Manures are bulky with low nutrient content. The nutrients of manures are released slowly.

2) Being bulky and voluminous, they are inconvenient to handle, store and transport. Moreover,

3) A manure is not nutrient specific and, hence, it is not much useful when a particular nutrient is required.

Types of Manures

1) Farmyard manure (FYM)

FYM is the decomposed mixture of cattle excreta (dung) and urine along with litter and left over organic matter such as roughage or fodder. These waste are collected and stored in a pit for decomposition by the micro-organism.FYM contains nitrogen, phosphorus and potassium. 0.5 per cent nitrogen, 0.2 per cent phosphorus pentaoxide (P₂O₅) and 0.5 per cent potassium monoxide (K₂O)

2) Compost

Compost is prepared from farm and town refuge such as vegetable and animal refuse, faecal matter of human beings, sewage waste, weeds, crop stubble, straw, rice hulls, forest litter, etc.

Composting is a biological process in which both aerobic (organisms requiring the presence of oxygen for the respiration) and anaerobic (organisms, in which respiration takes place in the absence of oxygen) microorganisms decompose the organic matter. It takes about 3 to 6 months for decomposition of organic refuse. The nutrient contents of town compost are about 1.4 per cent nitrogen (N), 1.0 per cent phosphorus pentaoxide (P₂0₅) and 1.4 per cent potassium monoxide (K₂O)

Vermicomposting : The degradation of organic waste through the consumption by the earthworms is called vermicomposting. An earthworm is physically an aerator, crusher and mixer, chemically it is a degrader and biologically a stimulator of decomposition.

3) Green Manuring

The practice of green manuring includes growing, mulching by ploughing and mixing of green crops with soil to improve physical structure and soil fertility. Green manures may include both leguminous and non-leguminous plants. These plants are used by Indian farmers to add nitrogen, phosphorus and other organic matter to the soil for the improvement of crop yield.

The green manure crops are grown in the field for about 6 to 8 weeks and turned into field in the tender stage, i.e., at flowering stage. The crops which require high nutrient input, are raised in the green manured field. Such crops are rice, maize, sugarcane, cotton, wheat, etc.

Fertilizers

Fertilizers are manufactured commercially from chemicals. Fertilizers supply Nitrogen, Phosphorus and Potassium (NPK). They are used for good vegetative growth (i.e., growth of leaves, branches and flowers), giving rise to healthy plants.

Chemically they may be inorganic compounds (e.g., ammonium sulphate) or organic compounds (e.g., urea).

On the basis of the availability of nutrients from them, fertilizers are divided into following four groups:

1) Nitrogenous Fertilizers

These fertilizers supply the macronutrient nitrogen.

Examples:  Urea CO(NH₂)₂ , Ammonium sulphate (NH₄)₂SO₄ , Calcium ammonium nitrate,  Sodium nitrate (NaNO₃) , Ammonium nitrate NH₄NO₃

2) Phosphatic Fertilizers

They are the source of the macronutrient phosphorus.

Examples : Single superphosphate, Triple superphosphate, Dicalcium phosphate.

3) Potassic Fertilizers

These fertilizers supply potassium which is one of the essential macronutrient of the plants.

Examples : Muriate of potash or potassium chloride KCl , Potassium sulphate, K₂SO₄ Potassium nitrate, KNO₃.

4) Complex Fertilizers

When a fertilizer contains at least two or more nutrients (N, P₂O₅ and K₂O, it is called complex fertilizer.

Examples : Nitrophosphate, Ammonium phosphate , Urea ammonium phosphate.

Fertilizers should be applied scientifically in terms of proper dose, time, pre-and post-application precautions for their complete utilisation.  

Manures	Fertilizers
A manure is a natural substance. It is obtained by the decomposition of animal wastes such as dung (gobar) of cattle and buffaloes and plant residues.	A fertilizer is a human-made substance. It is an inorganic salt or an organic compound.
A manure contains small amounts of essential plant nutrients such as nitrogen, phosphorus and potassium.	Fertilizers are very rich in plant nutrients such as nitrogen, phosphorus and potassium.
A manure adds a great amount of organic matter in the form of humus in the soil.	A fertilizer does not add any humus to the soil.
Nutrients present in the manure are absorbed slowly by the crop plants since manure is not soluble in water.	Being soluble in water, a fertilizer is readily absorbed by the crop plants.
A manure is not nutrient specific and it tends to remove the general deficiency of the soil.	A fertilizer is nutrient specific. It can provide specifically nitrogen, phosphorus and potassium to the soil according to the need.
A manure is voluminous and bulky so it is inconvenient to store, transport, handle and apply to the crop.	A fertilizer is compact and concentrated so it is easy to store, transport and apply to the crop.
A manure is cheap and is prepared in rural homes or fields.	A fertilizer is costly and is prepared in factories.

5) Biofertilizers

Organisms which enrich the soil with nutrients are called biofertilizers.

1) Biofertilizers are used for the specific crop plants such as pulses, legumes, oil seeds and rice.

2) Biofertilizers are renewable and non-pollutant sources of plant nutrients such as nitrogen.

Nitrogen fixing microorganisms, i.e. non-symbiotic and symbiotic cyanobacteria and phosphate-solubilising microorganism, are the main type of biofertilizers.

Two biofertilizers, namely Rhizobium cultures and blue green algaehave gained popularity amongst farmers cultivating pulses, legumes, oil seeds and wet-land rice.