Advantages Green Manure What It Is And Why To Use It Pros and Cons

About Green Manure

example of what dry clay soil looks like
Clay Soil Field Image by Ninifee

What is Green Manure

Green manure is a natural organic method of using specific plant and crop varieties that you grow then till into the ground to improve the quality of your soil.

Fertility building crops is another name that green manure gets called.[4]

Green manure uses cover crops to create a living mulch on the top of our garden's soil. Cover crops will grow thick and naturally help keep weeds in check and reduce soil erosion and splash.

Cover crops become green manures when we turn them over into the soil providing organic matter and nutrients back into the ground.

You can also leave the cover crops in the soil until you till your garden the following season.

Green manure is an organic farming method that is increasing in popularity. It plays a vital role in creating a sustainable cropping system.

Heterotrophic bacteria in the soil break down the cover crops by consuming the organic plant matter releasing the nutrient components into the ground. It is important to remember Heterotrophic bacteria need warmth and moisture like composting for this process to happen.

As the plant matter gets broken down, large amounts of carbon dioxide and weak acids react with insoluble soil minerals releasing the beneficial nutrients back into the soil.

What Are The Different Types of Green Manures?

Types Green Manure by Purpose

Cover Crops

Cover crops get sown into the soil to help prevent erosion.

Smother Crops

Smother crops get added when you are trying to out-compete weed growth on the soil. For example, fast-growing cover crops get selected, preventing room for weeds to move in.

Nutrient Conserving Crops

The aim is to prevent nutrient leaching of our soils while adding more nutrients back into the ground.

Nitrogen Fixing Crops

When our gardens are deficient in nitrogen, you would add legumes helping to enrich the soil since they add nitrogen back into the ground.

Break Crops

Break crops get added to help us interrupt the lifecycle of different pests and diseases that could harm our garden.

Types of Green Manuring Crops


  • Vetch
  • Sunhemp
  • Clover
  • Beans
  • Peas
  • Alfalfa
  • Velvet Bean
  • Cowpea
  • Fava Beans
  • Fenugreek
  • Groundnut
  • Lupin
  • Sunn hemp
  • Soybean
  • Sesbania Bispinosa fast-growing, perennial legume tree
  • Cluster Beans


  • Annual Ryegrass
  • Oats
  • Rapeseed
  • Winter Wheat
  • Winter Rye
  • Buckwheat
  • Millet
  • Sudangrass
  • Sorghum
  • Sweet Clover
  • Azolla
  • Phacelia Tanacetifolia

Root Vegetable

  • Tillage Radish
  • Daikon Radish
  • Mustard

The most commonly planted green manure crops are sunn hemp, dhaincha, pillipesara, cluster beans, and Sesbania rostrata.[3]

Green Manure and Green Leaf Manure Difference

While Green Manure and Green Leaf Manure sound similar, the method of creating them is pretty different. However, both are a type of organic manure that will help to increase the nutrient value and aeration of our soil.

Green manure requires actual cover crops to get grown in your garden. Then the land gets turned over to add the cover crops into the soil.

Green leaf manure, on the other hand, is when you got out and collect vegetation to add to the soil. So the foliage does not get grown on the area of land where you produce our crops.

Both methods are a helpful way for you to add essential plant nutrients and healthily increase the fertility of your soil.

Green Manure Advantages and Disadvantages


  • Adds Organic Matter to the Soil
  • Increases Soils Biological Activity
  • Improves Soil Structure
  • Reduces Soil Erosion
  • Increases the available supply of nutrients, mainly nitrogen, through the process of fixation
  • Reduces Leaching Losses
  • Suppression of Weeds
  • Reduces Pest and Disease Problems
  • Can Provide Supplementary Animal Forage
  • Drying and Warming the Soil
  • More Habitats for Pollinators
  • Help to Break up Heavy Clay Soil

Adds Organic Matter to the Soil

Organic matter added to your soil will help to increase the level of nutrients available to the ground. As a result, the earth will also have better aeration.

The soil structure can also get improved from the added aeration and water retention.

Increases Soils Biological Activity

The microorganisms are vital for you to have a good soil structure. Green manure can help to increase the number of microorganisms and helps to encourage high biodiversity in your soil.

Mycorrhiza fungi also increase in their numbers. These fungi are necessary for maximizing nutrient intake, resistance, and growth of the plants.

Improves Soil Structure

Organic matter added into the soil allows the soil particles to bind to it and creates soil aggregates.

This process increases soil aeration, nutrient distribution, and water retention of the ground.

Reduces Soil Erosion

Because the topsoil is no longer bear, it gets shielded from the elements. This shield helps to prevent soil erosion from wind and rain.

Increases the Available Supply of Nutrients

Green manure adds many different essential plant nutrients back into the ground.

If the soil needs higher levels of nitrogen, you add legumes as your cover crops. Or, if you need more phosphorous, adding buckwheat and lupin will help enrich the soil of this nutrient.

Reduces Leaching Losses

Fewer nutrients also leach away from the soil since the cover crops now draw in and hold these nutrients, preventing them from leaching out into the environment.

Suppression of Weeds

Cover crops can out-compete weeds for water nutrients and space.

Some cover crops also perform an allelopathic effect where they release chemicals that can inhibit the growth of the weeds.

These chemicals can disrupt the growing patterns and cycle of weed plants.

Reduces Pest and Disease Problems

Depending on the cover crops selected, green manure can disrupt the life cycle of many different pests and diseases.

Rye planted during the fall effectively limits the population of pests that infect potatoes and other common vegetables.

Mustard is another cover crop useful to kill pests and help prevent the plants from getting diseases.

Can Provide Supplementary Animal Forage

Cover crops like Safoin or Cockshead are both suitable for nitrogen-fixing in the medium term.

It is highly appetizing to animals and holds an excellent nutritional balance. It can be grazed or fed as hay or silage, providing additional food for livestock.

More Habitats for Pollinators

Many different cover crops provide nectar and pollen, attracting bees and butterflies helping to encourage their activity.

Cover crops like the Phacelia will attract hoverflies that will come and start eating up any aphids they may be around your garden.

Help to Break up Heavy Clay Soil

Clay soil is a heavy and thick medium. Adding green manure into clay soil can help to increase the aeration and allow other plant's roots to more easily take hold.


  • Rotation Limitations
  • Over-fixation of Nutrients
  • Expense
  • Good planning of plantation needed
  • Decomposition Process of the Green Manure Requires Water
  • Could get in the way in places that can do year-round gardening

Rotation Limitations

Adding in cover crops is another crop type we are adding into our crop rotations.

You may have to restrict the use of your land to produce other legume crops to help minimize any disease problems.

Over-fixation of Nutrients

Overuse of green manures can provide too many nutrients. Large amounts of nitrogen and phosphorus causing the soil to become toxic to plant life and increase nutrient pollution.


For some farmers, the cost of planting cover crops could not make sense from a financial standpoint.

Cover crops do take up some room and may prevent some farms from planting as many of their cultivation crops as they would otherwise.

Over seasons the reduction of cultivated crops could reduce the profit margins by amounts too large for their liking.

Good Planning of Plantation Needed

Suppose care is not taken in selecting the best cover crops for the situation. In that case, farmers could find their produce competing against them for available resources.

Or the nutrients could be at too high of levels making the soil toxic to your plants.

Decomposition Process of the Green Manure Requires Water

For the green manure decomposition to take place, the fields require both water and warmth.

If the weather is too dry, farmers will have to ensure they add enough water for the decomposition process to occur.

Harboring Slugs and Snails

If you are growing a crop susceptible to slugs or snails, extra care needs to get taken.

Green manure provides the perfect breeding grounds for them to breed and could drastically increase their numbers.

Making Green Manure

To make green manure, all you have to do is add cover crops to your garden.

The site's specific needs for the soil should get taken into account.

For example, suppose we are trying to add nitrogen to the ground. Legumes should be the focus.

On the other hand, if you are trying to prevent weeds and decrease soil erosion, grass-type cover crops would be better for you to focus on.

The season should also get considered when planting.

In the summer, heat-loving crops like beans work while. But later in the season during fall, cool-season grass like winter rye is best to get planted.

Because of the rapid growth of clover crops, you can also work as an excellent soil amendment before planting your actual crop before spring planting.


Green manure is a natural organic method of increasing the fertility of our soil and benefits it by adding more biodiversity.

Before industrial agriculture, green manure has been heavily used and is a proven method of improving our soil structure.

When adding cover crops to your garden, it is necessary to think about the qualities you are trying to add. For example, if you are trying to add nitrogen, it is best to focus on legumes.

On the other hand, if you want to reduce soil erosion, the primary focus should be adding more grass cover crops.

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