Green Manures

Introduction

In recent few years, the production of the food grain has been increased. This is due to the different fertilizers and pesticides which help to increase the fertility the soil as well as destroy the harmful insects.

Simply, fertilizer is defined as any chemical substances which contain the required elements for the proper growth and development of plants. There are two types of fertilizer which are described below:

1. Chemical fertilizer- It is defined as the type of fertilizer which contain required minerals nutrients that can be utilized by plant directly for their growth. The elements contains in these fertilizer are nitrogen, phosphorous and potassium. These types of fertilizer are artificially prepared by the different fertilizer factories. It shows the quick result to the plants, but as a disadvantage on the frequent use of chemical fertilizer it harms the soil and affects the composition of soil.
2. Organic fertilizer- Those fertilizers which are prepared by using the organic substances are known as the organic fertilizer. They are also called manure or biofertilizer.

Some of the drawbacks of the chemical fertilizers

Though the chemical fertilizer increases the production rate as well as help in the quick growth and development of the plants, it has got several disadvantages. Some of them are mentioned below:

1. These types of fertilizers are very expensive and cannot be afford by the poor farmers.
2. They are not environment friendly and cause different pollution on the environment such as water pollution, air pollution and land pollution.
3. The frequent or over use of the chemical fertilizers may decrease the fertility rate of the soil and destroy the composition of the soil too.
4. They are not good for the human health and cause different diseases.
5. They not only destroy the harmful insects or microorganisms but also the useful one present in the soil.

So, to overcome these problems caused by the chemical fertilizer, biofertilizer should be used.

Fertilizer of biological origin

Soil has the great composition; it contains all the required nutrients which are important for the proper growth and development of the plants. But the continuous use of the land for the agriculture may affect the fertility of the soil and may lead less production. In the absent of any one of the nutrient, it may affects in the proper growth and development of the plants.

The fertility rate of the soil can be increased by different method. Most of the farmers sue the chemical fertilizers to enhance the fertility rate of the soil. But the frequent or over use of the chemical fertilizers destroys the fertility of the soil and effect the composition of the soil. So, to decrease the affects of the chemical fertilizer, recently a new train of using fertilizer which is environmental friendly and can be prepare from the biological components. Biofertilizer can be defined as the materials which are originated biologically and can be use commonly for to maintain and improve the soil fertility. They are categorized into two groups. They are:

1. Manures
2. Bio-fertilizers

Manure

Manure is defined as the organic matters which are biodegradable and mixed with the soil. It is consists of all the essential nutrients which are required for the growth of plants. With the use of manure the productivity of the crops can be enhance. There are three types of manure. They are described below:

1. Farmyard manure- It the manure made from the organic matter used in the farm yard. It consists of different organic matters such as cattle dung and crop residue (like; remnants of the straw and plant stalks fed to cattle. For the preparation of the farmyard manure the pit of one meter should made and all the organic matter need to kept in the pit. The mouth of pit should be plastered for 2-3 months.
2. Composite manure- It is the manure made by using the organic matter like rotten vegetables and animals-shed waste, refuse, farm weed, etc. These all organic matters are properly mixed and decomposed.
3. Green manures- It is the type of manure which is made by using the green plants having high nutrients. They are the plants grown in the field and ploughed back under the soil. In other word, it is the practice of growing the plants in the field and plugging them back under the soil and let them decompose inside the soil due to which fertility rate of soil increase.

Importance of green manure in agriculture

1. They are the cheapest manure since they can be made with the help of organic matter around.
2. They increase the fertility if soil by providing additional nitrogen.
3. They have all the essential nutrients required for the plant and also supply practically to the plants.
4. They help in the growth of the plants from 30%-50%.
5. The aeration and drainage condition can be improved by them.

Bio-fertilizers

Bio-fertilizer is the fertilizer prepared by the biologically active products which are capable to improve the fertility of soil. Some bio-fertilizer are bacteria, cynobacteria and fungi. They are able to incerase the fertility of soil by adding more nutirents to the soil with their different biological activities.

1. Bacteria as biofertilizer: Some are very useful since they fix the free nitrogen of atmosphere to the soil which increases the fertility of soil. Some them and their roles are mention below:
2. Rhizobium- Bacterium like Rhizobium is symbiotic and found in soil which form nodules in the roots of legume plants .It helps the plants by fixing the free nitrogen of atmosphere to the soil in the form of nitrates. The free nitrogen of the atmosphere cannot be utilized by the plants; it is the great help for them.
3. Azotobacter- It is a kind of bacteria which is free living and non-symbiotic in nature. It also fixes the nitrogen which is utilized by the plants like rice, millet, maize, etc.
4. Cynobacteria as biofertilizer: Cyanobacteria are also known as blue green algae which are most important nitrogen fixer. They are able to fix the nitrogen present in the water. Some Cyanobacteria are as follows:
5. Anabeana azolla- They have capacity of fixing the free atmospheric nitrogen as well as exudates nitrogenous compound into the leave cavities. Those leaves can be the best bio-fertilizer.
6. Anabeana, Nostoc, Spirulina- Through the help of photosynthesis these free living bacteria can fix the nitrogen. In Indian it is mostly use as bio-fertilizer.
7. Fungi as bio-fertilizer- some fungi are symbiotic in nature and association in the root of seeds bearing plants. This association is known as The marginal land can be converted into a fertile land with the mycorrhyza association. Two types of Mycorrhyza are as follows:

• Ectomycorrhyza- It is type of association in which fungus lives out of root of the plants like pine, oak, peach, etc. Different minerals like nitrogen, phosphorus, calcium and potassium are absorbed and stored by these fungi.
• Endomycorrhyza- It is the type of association in which fungi lives between and within the cells of cortex of plants like orchids and other. It helps in phosphate and nitration in plants.

Use of VAM

The major use of VAM is to supply the inorganic nutrients and absorption of water. With the help of VAM phosphate can be easily available to the plant. It plays vital role in the phosphate nutrition.

Nitrogen fixation

Nitrogen fixation is the process which deals with the conversion of the free nitrogen of the atmosphere into the nitrogenous salt. Different bacteria like Rhizobium and Bacillus radiciola helps in the nitrogen fixation. These bacteria enter on the root through the root hair from the soil of plants like beans, soybeans, gram and groundnuts. Due to the presence of pigment called leghaemoglobin root nodule is pinkish. Leghaemoglobin also absorbed the oxygen.

Some free living microorganism such as cynobacteria and photosynthetic bacteria help in nitrogen fixation.

Refrence:

Arvind K. Keshari,Kamak K. adhikari. A Text Book of Higher Secondary Biology. Kathmandu: Vidyarthi Pustak Bhandar, 2014.

Agrawal, sarita. principle of biology. 2nd edition . kathmandu: Asmita book Publication, 2068 ,2069

Mehta, Krishna Ram. Principle of biology. 2nd edition. kathmandu: Asmita, 2068,2069.

Jorden, S.L. principle of biology. 2nd edition . Kathmandu: Asmita book Publication, 2068.2069.