What is Green Manuring? and its advantages and disadvantages

What is green manure?

Generally, manures are added to the soil to increase the soil fertility and yield of crops. To distinguish organic and inorganic substances used for the purpose, the organics are specifically called ‘Manures’ and inorganic are called as ‘Fertilizers’.

Organic Manures: The organic manures are made up of dead plants and animals remains. They are bulky in nature and poor in plant food. They supply almost all the ingredients of plant food. Bulky, organic manures are farmyard manure, compost, and green manure.

Substances like oilseed cakes, blood meal, bone meal, etc are rich in particular nutrients, and they are referred to as concentrated organic manures. Synthetic organic product like urea is also coming into use for supply of nitrogen.

Sr.No.Organic manureNitrogen (N)Phosphorus (P2O5)Potash (K2O)
(A)Bulky organic manure
1Farm Yard Manure0.500.250.60
2Compost0.890.513.05
3Manure of night soil1.000.800.40
(B)Concentrated organic manure
1Groundnut cake7.291.531.33
2Linseed cake5.561.441.28
3Castor cake4.371.851.39
4Neem cake5.221.081.48

Green Manuring

What is Green Manuring?

‘Green manuring is a practice of plowing or turning the un-decomposed green plant tissues into the soil to improve soil fertility.’

Green manuring is the practice of applying as manure large quantities of green material such as leaves and twigs of plants or crops grown for this purpose. Growing of a crop or applying of leaves and twigs of plant and incorporating it with the soil is called ‘green manuring’.

Methods of green Manuring

There are two methods: (A) Green manuring in situ and (B) Green leaf manuring.

(A) Green Manuring in Situ– Growing a crop and incorporating (plowing) it in the same field with the soil is called a situ method of green manuring.

Green manure crops:

Leguminous (pulse) crops used for Green manuring

(1) Sannhemp (Crotalaria juncea) – Adapted to well-drained soil, suitable for upland condition, quick-growing, relatively resistant to pest and diseases, have a deep root system.

(2) Dhaincha (Sesbania aculeata) – Resistant to drought, salt, and water-logging, ideal for rice soil (clay), generally grown in lowland, suitable for saline and alkaline soil, have a deep root system.

(3) Dhaincha (Sesbania rostrata) – A newly introduced green manure crop which can also grow in water-logged condition. In this crop nodules formation is on the roots and also in large numbers on the stem. So that it fixes more nitrogen than Sesbania aculeata.

(4) Mung (Phaseolus aureus mung) – It is quick growing, drought-resistant.

(5) Indigo (Indigofera tinctoria) – Suited to heavily soil (clay), slow-growing.

(6) Khesari (Lathyrus sativus) – Winter season crop.

Non-Leguminous Green manure crops

(1) Bhang (Cannabis sativa)

(2) Kodogira (Vernonia cinerea)

(B) Green Leaf Manuring – When green leafy material is collected from other places and plowed in the field it is known as green leaf manuring.

Green Leaf Manuring Crops 

  1. Glyricida (Glyricida maculata)
  2. Karanj (Pongamia glabra)
  3. Ipomoea (Ipomoea carnea)

Green manuring procedure

The green manuring practices are given below:

  1. Green manure crops can be grown in any type of soil, provided there is sufficient rainfall or irrigation available.
  2. To ensure success with a leguminous green manure crop is to inoculate the seed with the proper strain of bacteria.
  3. The green manure crop should be sown with a higher seed rate than usual so that there will be a good canopy produced very quickly.
  4. The production of green manure is limited by the plant food elements deficient in the soil.
  5. The best stage at which the crops should incorporate in the soil as a green manure is when it reaches the flowering stage.
  6. Burying of green manure crop is done in different ways. In some cases, the plants are cut close to the ground and the green material is put in the furrows opened by a moldboard plow and is later buried. In drier areas this method has been proved to be better than plowing in.
  7. Immediately after plowing the material, careful packing of the soil should be done by suitable implements to ensure proper decomposition. Packing is especially necessary if the soil moisture supply is deficient.
  8. Under certain favorable circumstances, green manure crops such as dhaincha can be sown in between the rows of cotton or Jowar. When dhaincha is sufficiently tall it can be uprooted and mixed with the soil by inter-cultivations.
  9. Under limited moisture supply conditions, it may be advisable to grow the green manure crops in one field and add the green material to another field. By doing this the moisture required for growing the green manure crop is saved.
  10. For proper decomposition, in light soils, the crop should be buried deeper than that in the heavy ones.

Selection of Green manure crops

  1. It should be quick growing, so that timely incorporation of green manure crops may be done. For example, sunn hemp and mung.
  2. It should yield large quantities of green material in a short period. For example, dhaincha.
  3. It should be preferably from the legume family so that nitrogen would be fixed in addiction to green matter production. For example, dhaincha and sunn hemp.
  4. It should be tender so that its decomposition will be rapid. For example, berseem and labia.
  5. It should have a deep root system so that it would penetrate deep layers of the soil. Thus, it utilizes nutrients, and water from deeper layers also helps in developing good soil structure. For example, sunn hemp and dhaincha.

Decomposition of Green Manure

A host of micro-organisms affects the complete disintegration of organic matter leading up to ammonification and finally nitrate production. The factors for complete decomposition are the varying moisture conditions of the soil. The desired results would follow if moisture contents are high in the beginning, leading to semi-anaerobic fermentation of resistant material and low (moisture) afterward for inducing aerobic conditions under which nitrification can take place. Decomposition also depends on other factors such as the composition of green matter (crop) and the presence of available inorganic nutrients.

Advantages of Green Manuring

  1. It increases the fertility of the soil.
  2. Being a legume, it fixes atmospheric nitrogen in the soil.
  3. Being a quick growing crop, it helps in suppressing weed growth.
  4. It improves the soil structure, water holding capacity & decreases runoff.
  5. It adds organic matter & stimulates activities of soil micro-organisms.
  6. Increases the availability of plant nutrients.
  7. Green manuring checks weed growth.

Disadvantages of green manuring

  1. It may increase the incidence of pests & diseases.
  2. There is a loss of one season especially Kharif.
  3. Due to improper decomposition, problems of insect-pests and diseases may come up.
  4. Sometimes the cost of green manuring is more than chemical fertilizers.
  5. If rainfall is scanty, the growth of green manure crops would be less vigorous which results in less production of green matter.