One environmental protection trend that is helping the agriculture sector move toward sustainability by conserving resources and meeting food demand is the adoption of green manure. Today’s farmers confront a complex set of challenges as they seek solutions to transition to more sustainable methods of production. One of them is to reduce chemical use without sacrificing soil fertility. Green manure crops might be a viable option for dealing with this issue.
This article will cover all there is to know about green manure crops, including the advantages and disadvantages associated with using them.
See also: Green manure: Types, planting, benefits and drawbacks
What is green manure?
Green manure is an agricultural practice wherein plants are grown specifically to be tilled into the soil while they are still vegetative as a kind of fertiliser. These crops are often sown in the intervening spaces between the major crops. They function as a ground cover while they’re growing, protecting the soil from erosion and nutrient runoff with their extensive root systems, stifling weed development, and adding nitrogen to the earth in the process.
Green manure crops: Significance
Sustainable agriculture relies on practices like crop rotation and the use of green manures to preserve soil fertility. The risk of land degradation may be eliminated by using green manure crops, which protect the soil, fertilise it, and increase its organic content. Improved healthy soils also indicate more long-term food security because of the reduced demand for chemical fertilisers and intensive soil cultivation.
The potential for using less artificial fertilisers and less heavy equipment throughout the process of crop cultivation suggests a large drop in the levels of pollutants released into the air and water. Growers can construct an organic farm due to the cultivation of green manure crops.
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What are the two types of green manure?
Legumes and Non-legumes are the two types of green manure. Legumes are plants whose roots work with the soil’s bacteria and trap nitrogen from the atmosphere. Non-legumes are mainly the cover crops that prevent soil from erosion.
Green manure is also distributed in the below mentioned categories.
- Cover crops, which cover the soil and prevent it from erosion. For eg, lentils, oats, clovers.
- Smother crops give competition to weeds and ensure that the nutrition is not lost. For eg. winter rye and buckwheat.
- Break crops are crops that interferes with the lifecycle of insects, diseases and pests. For eg. mustard, brassica, rye.
- Nitrogen-enriching crops enrich the soil with nitrogen. For eg. Clovers, beans, peas.
- Nutrient conserving crops, conserve nitrogen from wastage and ensure soil gets the maximum of it to be enriched. These include ryegrass, oil radish etc.
What are some green manure crops?
Green manures may be broken down into the following categories according to when the seeds are planted.
Long-term green manures
They are grown for at least two or three years to function as an essential component of organic farm vegetable and arable crop rotations. The following types of green manure crops are included on the list of those suitable for long-term planting:
- Sainfoin
- Red clover
- White clover
- Alfalfa
- Perennial ryegrass
- Lucerne
Winter green manures
Planted in the autumn to incorporate them the following season and acting as a nitrogen-building crop while making use of land that would normally be left fallow, the seeds are planted in the fall. The following are examples of the types of green manure that are ideal for winter use:
- Common vetch or tares
- Trefoil
- Buckwheat
- Ryegrass
- Tares
- Grazing rye
- Mustard
- Phacelia
- Feld beans
Summer green manures
It’s a method for keeping nitrogen levels high while also rotating crops. Grown either year-round (April–September) or seasonally (in the interval between the two major harvests). In the summer, you may plant the following green manure crops:
- Fenugreek
- Mustard
- Lupins
- Vetch
- Buckwheat
- Crimson clover
- Sweet clover
- Persian clover
Undersown green manures
The word refers to the practice of combining a green manure crop with an existing grain crop during the spring growing season to facilitate improved weed control. These types of crops include:
- Subterranean clover
- Red clover
- White clover
- Lucerne
- Yellow trefoil
- Oats
Green manure mixtures
The term refers to planting multiple different crops simultaneously to maximise the advantages. The following are some examples of crop combinations that work particularly well as green manure in mixed planting:
- Oats/peas/vetch
- Rye/vetch
- Red clover/ryegrass
When to sow green manure crops?
There are benefits associated with sowing green manure crops at any time throughout the growing season; these benefits are generally consistent across the board. Although manure is often used to cover the ground during the autumn and winter months to avoid erosion, it also provides comparable advantages during the summer months by shielding the land from the drying impacts of sun and wind.
When to dig in green manure crops?
Ideally, you should dig in the plants two to three weeks before you expect to use the soil once more or when they are nearing maturity. This is because the young plants’ bulk will degrade quickly enough to feed the soil. For this reason, it is essential that you do not wait until they bloom. In addition, consider digging now before the stems get woody and become more difficult to decompose in the soil.
How does green manure impact the soil?
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Soil conservation and improvement
Manuring is often done to protect the major crops from wind and rain and provide nutrients to the soil. Plant matter that has decomposed provides organic materials and nitrogen to the soil. As they develop, plants also enrich the soil with potassium, phosphate, iron, and calcium.
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Preventing soil erosion and runoff
Green manure plants have a root structure that breaks up compacted soil, allowing more air and water to reach the plant roots. Green manure may be grown without tilling the soil since the roots naturally aerate and turn the soil. For agriculture to be sustainable, practices like using less or no-till are essential.
The plant remains, after decomposing, will ultimately release the nutrients they have gathered into the soil. This will stop the nutrients and other beneficial chemicals from seeping into the environment.
Green manure crops: Advantages and disadvantages
Many people who favour organic farming also advocate using natural fertilisers like green manure. The nitrogen these plants collect on average may completely replace mineral nitrogen fertiliser at standard application rates. However, there are several advantages and disadvantages to consider before settling on this strategy.
The following list are the primary advantages of growing green manure crops instead of leaving the land uncultivated.
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Elimination of weeds
Green manures work as a kind of natural weed control because they prevent the growth of weeds by making it hard for them to penetrate the thick biomass and reach the sunlight.
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Pest and disease mitigation
The populations of the principal pests that endanger the cash crop may be reduced due to the ability of some crops to ward off pests and thwart the spread of diseases. Some plant species can even ensnare pests inside their own root systems.
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Support from beneficial organisms
Flowering plants draw in pollinating insects, increasing the number of species that are useful to the ecosystem. For example, bees and bumblebees are drawn to the blossoms of phacelia plants.
As an added bonus, manure feeds the bacteria and other creatures in the soil. Soil aggregates, which increase the soil’s porosity and organic matter, are mostly the product of these organisms’ activity. Soil bacteria get their nourishment from the plant’s roots. Plants that are buried help promote more microbial life in the soil as they decay.
Disadvantages
Before deciding to use green manure, there are a few cons to consider, despite the clear advantages.
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Time needed
Before seeding the main crop, it is necessary first to prune cover crops and rotate them. This is a time-consuming operation. If a harvest is allelopathic, which means that it necessarily leaves some harmful compounds in the soil, it might take as long as a month for the next crop to germinate.
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Moisture usage
Like every other plant, green manure crops need moisture to survive. Therefore, if they were to be planted in a region with low amounts of moisture, they may take up every drop of water available. This necessitates using more irrigation to sustain the development of the cash crop.
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Rotation limits
Incorporating manure into your farming operations necessitates adjusting your crop rotation schedule to accommodate the addition of a new crop. If green manure crops are planted immediately after the main plant is harvested, they won’t provide the soil enough time to recover and prepare for the next growing season.
FAQs:
How much time is needed to get green manure ready for use?
Green manure typically needs at least 8 weeks to develop and another 6 weeks to degrade. Depending on the size of your plot and how soon you have to plant into it, there are a few different methods to slice and integrate your green manure.
What kind of green manure has the most quantity of nitrogen?
The ideal green manure crop is dhaincha, also known as Sesbania aculeata, since it has a nitrogen content of 3.50%, which is more than any other green manure crop.
Why is green manure not used more frequently?
Farmers do not often utilise green manure since most crops they grow are for human consumption. Green manure crops may suck up most of the moisture in the soil. Microorganisms may take the majority of the nutrients.
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