Popular Legume Plants: What Are The Different Types Of Legumes

Popular Legume Plants: What Are The Different Types Of Legumes

By: Bonnie L. Grant, Certified Urban Agriculturist

Beans and peas are two of our most common vegetables and provide an important source of vitamins and protein. What is a legume? There are many types of legumes, most of which produce a pod that splits evenly in half. Legume cover crops are important nitrogen-fixing plants for soil health. This important legume info is crucial to gardeners and farmers where over planting depletes soil nutrients.

What is a Legume?

The family of legumes is Leguminosae. Legumes are found in most areas of the world and are fast growing and inexpensive food crops. Domesticated legume crops have been in human cultivation for more than 5,000 years.

Legumes encompass a wide range of edible nuts and vegetables. There are also legume plants that are not edible but have many of the same benefits for soil health. Legume pods easily break into two equal hemispheres, but not all legumes produce pods. Some, such as clover and alfalfa, are edible forage for cattle and other herbivores.

Legume Info

Legume pods are high in protein and have a low glycemic index. They substitute for animal fats in vegetarian diets and have low fat properties. Legumes are also a rich source of fiber. As a result, both pod and forage legumes have been in human cultivation for centuries. Farmers have long known that legume plants improve soil conditions.

The range of legume plant forms includes vine types to creeping ground covers. All legumes are flowering and most have a flower that produces a thickened petal or keel that is formed by two petals that fuse together.

Legume Cover Crops

Beans and peas are not the only legumes. Legume cover crops may be alfalfa, red clover, fava, vetch or cowpeas. They store nitrogen in nodules on the roots. The plant harvests nitrogen gas from the air and combines it with hydrogen. The process creates ammonia, which is converted by bacteria into nitrates, a usable form of nitrogen.

Once the plants are tilled into the soil, they release the nitrogen into the earth as they compost. This improves the soil and provides supplemental nitrogen that was removed by other plant’s growth.

Legume cover crops are valuable for the home gardener as well as the farmer. They also help prevent soil erosion and provide food for wildlife.

Types of Legumes

The most popular legume plants are peas and beans. Pole or bush beans provide long slender pods, while peas may be shell or edible pods. Stringless varieties of beans are easier to eat and snow or sugar peas have such soft shells that the entire pea is delicious eaten whole.

Some beans are meant to be shelled and the small ovaries inside dried. These are kidney, cranberry and black beans, among others.

Outside of these popular legume plants, there are also other types of legumes. There are 18,000 species of plants in the family. The tipu tree, Moreton Bay chestnut, Acacia and Albizia are all forms of legumes from around the globe. Even the common peanut is a member of the legume family.

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A legume ( / ˈ l ɛ ɡ j uː m , l ə ˈ ɡ j uː m / ) is a plant in the family Fabaceae (or Leguminosae), or the fruit or seed of such a plant. When used as a dry grain, the seed is also called a pulse. Legumes are grown agriculturally, primarily for human consumption, for livestock forage and silage, and as soil-enhancing green manure. Well-known legumes include alfalfa, clover, beans, peas, chickpeas, lentils, lupins, mesquite, carob, soybeans, peanuts, and tamarind. Legumes produce a botanically unique type of fruit – a simple dry fruit that develops from a simple carpel and usually dehisces (opens along a seam) on two sides.

Legumes are notable in that most of them have symbiotic nitrogen-fixing bacteria in structures called root nodules. For that reason, they play a key role in crop rotation.

Legume Cover Crops


Geographical relevance



Commonly used legume cover crops include:

  • Winter annuals, such as crimson clover, hairy vetch, field peas, subterranean clover and many others
  • Perennials like red clover, white clover and some medics
  • Biennials such as sweetclover
  • Summer annuals (in colder climates, the winter annuals are often grown in the summer)

Legume cover crops are used to:

  • Fix atmospheric nitrogen (N) for use by subsequent crops
  • Reduce or prevent erosion
  • Produce biomass and add organic matter to the soil
  • Attract beneficial insects

Legumes vary widely in their ability to prevent erosion, suppress weeds and add organic matter to the soil. In general, legume cover crops do not scavenge N as well as grasses. If you need a cover crop to take up excess nutrients after manure or fertilizer applications, a grass, a brassica or a mixture is usually a better choice.

Winter-annual legumes, while established in the fall, usually produce most of their biomass and N in spring. Winter-annual legumes must be planted earlier than cereal crops in order to survive the winter in many regions. Depending on your climate, spring management of legumes will often involve balancing early planting of the cash crop with waiting to allow more biomass and N production by the legume.

Perennial or biennial legumes can fit many different niches, as described in greater detail in the individual sections for those cover crops. Sometimes grown for a short period between cash crops, these forage crops also can be used for more than one year and often are harvested for feed during this time. They can be established along with—or overseeded into—other crops such as wheat or oats, then be left to grow after cash crop harvest and used as a forage. Here they are functioning more as a rotation crop than a cover crop, but as such provide many benefits including erosion and weed control, organic matter and N production. They also can break weed, disease and insect cycles.

Summer-annual use of legume crops includes, in colder climates, the use of the winter-annual crops listed above, as well as warm-season legumes such as cowpeas. Grown as summer annuals, these crops produce N and provide ground cover for weed and erosion control, as well as other benefits of growing cover crops. Establishment and management varies widely depending on climate, cropping system and the legume itself. These topics will be covered in the individual sections for each legume.

Legumes are generally lower in carbon and higher in nitrogen than grasses. This lower C:N ratio results in faster breakdown of legume residues. Therefore, the N and other nutrients contained in legume residues are usually released faster than from grasses. Weed control by legume residues may not last as long as for an equivalent amount of grass residue. Legumes do not increase soil organic matter as much as grasses.

Mixtures of legume and grass cover crops combine the benefits of both, including biomass production, N scavenging and additions to the system, as well as weed and erosion control. Some cover crop mixtures are described in the individual cover crop sections.

Find the Ideal Cover Crop for Your Garden

Because not all cover crops provide the same benefits, you’ll want to look for a mix that addresses the issues you’re having or the goals you want to accomplish in your garden. However, it’s a delicate balance — your aim is to choose a mix that contains complementary, rather than competing, cover crops.

Nitrogen uptake + compaction busting: The radish, crimson clover, and triticale combo works well here. While the last two cover crops help to cycle nitrogen (making it available for the next crop), the radish’s taproot busts up soil compaction. Legume cover crops are the masters at adding valuable nitrogen back into the soil.

Weed suppression + nitrogen uptake: Try oats and hairy vetch, a powerful cocktail that not only holds weeds down but allows the next crop you plant to utilize soil nitrogen (nitrogen uptake). A side benefit? The hairy vetch is pretty good at erosion control, too. Grasses are cold, hardy crops that suppress weeds and add tons of organic matter back into the soil. Their root systems are also great at breaking up compacted soil or clay soil, the death knoll for a healthy garden.

Nitrogen fix + organic matter + weed suppression: A pea and oat mixture might work for you. Peas provide a nitrogen “fix” to the soil (and add valuable organic matter) while the oats suppress weeds and act as a “nurse crop” for what you plant next. Nurse crops help aid other crops in getting established, but the oats also provide a kind of living trellis for the pea vines to grow upon.

Nitrogen fix + Pollinator magnet: A mix of clovers can do the trick! Red, ladino, and sweet clover work their magic together by adding valuable nitrogen to the soil while providing valuable food for pollinators like bees.

Can I Create My Own Cover Crop Mix?

While many mixes are readily available and take the guesswork out of successful combos, it is possible to create your own custom mix. Take the following into consideration, and call your county extension office if you need assistance.

  • Make a list of the top 2-3 garden/plant/soil issues you’d like to handle with your cover crops
  • Research various crops that address your top concerns
  • Narrow your cover crop mix down to 2-5 different crops
  • Ensure that your cover crop combo is compatible in terms of planting times and complementary growth habits. For example, you want to avoid planting a mix of two cover crops that are both slow to grow, as that can allow weeds to take hold in the meantime. Similarly, a cover crop that puts nitrogen into the soil should not be planted with a cover crop that takes nitrogen up for later use — they will work against each other and you’ll be disappointed with the result.

How to Plant Cover Crops:

Planting a cover crop is easy. Here are the steps:

  1. Remove weeds and crop debris from the planting beds break up clumps of soil and rake the seedbed even.
  2. Determine the square feet you intend to plant you will need about 1 cup of cover crop seed for every 50 square feet you want to plant.
  3. Broadcast the very small cover crop seed (such as annual rye or clover) across the planting bed. Large cover crop seed such as beans and peas can be sown in furrows ½ inch to 1 inch deep 6 inches apart. After broadcasting or seed sowing rake the bed lightly to ensure the seed is covered. If you are sowing legumes such as soybeans, clovers, and vetch as a cover crop, add an inoculant that contains the bacteria needed to work with the cover crop’s roots to fix nitrogen.
  4. Keep the seedbed just moist until the cover crop germinates and becomes established. If the weather is very hot keep the seedbed from drying out by sprinkling straw over the seedbed. If birds start digging up the seed, lay a loose spun poly row cover over the planting bed.

Cover Crops

Pisum sativum: Producers should plant winter pea in September. Winter pea grows on a vine, similar to vetch. This cold-hardy, annual legume can provide lots of residue, but may decompose quickly because of the high nitrogen content. Winter pea can provide up to 150 pounds of nitrogen per acre. This legume provides very good erosion control and forage quality. It is also a great cover crop to help attract beneficial insects.

Vigna unguiculata L. cv. ‘Iron Clay’: Cowpeas originated in Africa and have been bred by farmers for thousands of years for different uses and situations. Producers should plant cowpea when soil temperatures reach 65 degrees Fahrenheit, 9 weeks before the first frost. The ‘Iron Clay’ cowpea, a summer annual, is a common southeastern cover crop. The Iron Clay Cowpea is heat-tolerant and handles drought well. It can grow in poor soils or moderate shade. Iron Clay Cowpea provides excellent weed and erosion control. It is also a very good attractor of beneficial insects.

Trifolium incarnatum: Crimson clover is a winter annual legume in the Southeast and can accumulate up to 5,500 pounds of residue if planted early. Producers should plant crimson clover in August and September. Crimson clover provides excellent forage quality. It is also very good at providing weed and erosion control.

Vicia villosa: Hairy vetch is a winter legume that provides heavy residue to protect the soil and choke out weeds. Plant hairy vetch 15 to 45 days before the killing frost. This legume produces about 100 pounds of nitrogen per acre. Hairy vetch is an excellent cover crop for attracting beneficial insects. It is also a good cover crop for weed and erosion control.

Crotalaria juncea: Sunn hemp is a summer legume that is native to India and Pakistan. Plant sunn hemp at least 9 weeks before the average frost. This summer legume can produce 120 pounds of nitrogen per acre in two to three months. It is an excellent cover crop for compaction reduction and weed and nematode control. Sunn hemp is a very good cover crop for erosion control.

Legume cover crops


A LEGUME THAT has had a bad reputation as a weed for decades may make the best cover crop, according to research conducted at Agriculture and Agri-Food Canada’s Harrow Research and Development Centre.

“Hairy vetch had the best performance by far,” says Dr. Xueming Yang, the soil scientist who is working on the project with colleagues Dr. Dan Reynolds and Dr. Craig Drury.

The aim of the research project — which runs from summer 2017 to spring 2021 — is to make more effective use of legume cover crops (seeded in the summer after winter wheat harvest) in soybean-winter wheat-corn rotations on a Brookston clay loam — the most prevalent agricultural soil in southwestern Ontario.

The study compares hairy vetch, red clover, and a crimson and white clover mix in terms of how well they contribute nutrients — especially nitrogen (N) – to the subsequent main crop (corn) and what they do for soil health. The anticipated outcome is a ranking of cover crop efficacy, and recommendations on how to best terminate cover crops for the best agronomic and soil performance.

One objective was to find out how much nitrogen cover crops can store at the time when the cover crop was terminated by plow-down in late fall or by herbicide spray-down in spring before corn planting. “Hairy vetch is a dependable legume with large amounts of biomass N,” says Yang.

They found more nitrogen in hairy vetch aboveground biomass (186 kg N/ha) than in the crimson/white clover (144 kg N/ha) and the red clover (89 kg N/ha) by late November when the cover crops were plowed down.

“The legumes in the trial are winter hardy, and all get lush regrowth the following spring before spraying them with herbicides,” says Yang.

They found 160, 170, and 172 kg N/ha stored in aboveground biomass of crimson/white clover mix, hairy vetch, and red clover, respectively, before corn planting.


The trial also evaluates the nitrogen credit of cover crops, in other words, the amount of nitrogen fertilizer that is replaced by legume cover crops in corn production. A control corn crop (i.e. corn with no prior cover crop) was fertilized with 200 kilograms (kg) of N per hectare, and corn following cover crops was fertilized with 100 kg N per hectare.

“Corn responds differently to legumes and cover crop termination methods,” says Yang. “When corn is planted into a field where legumes were terminated by fall plow-down, we got a nitrogen credit of 70 to 80 kg N/ha, which was similar among the three legumes”.

When corn is seeded into a no-till or a strip-tilled field where legumes were killed by spring spray-down, the nitrogen credit varied a lot, from as low as 30 kg N/ha for clovers to as high as 95 kg N/ha for hairy vetch.

“The low nitrogen credit from the clovers was not due to low legume nitrogen in soil — the nitrogen is there,” says Yang. “The reason was that there was poor corn emergence in the clover fields in the spring which resulted in a low plant population at harvest for this clay soil.”

On average, the corn yield following a cover crop of hairy vetch was nine to 15 per cent greater than corn yields following red clover and crimson/white clovers. “In 2020, corn following hairy vetch had a similar yield as the yield of the control corn,” Yang says.

For hairy vetch, reducing N fertilizer to one-half the control amount (100 kilograms N/hectare) provided similar yields as the control field (13 tonne/ha), and a substantial savings in N fertilizer costs.

“All legumes in the trial are winter hardy, but an advantage of hairy vetch is that when you plant it in late summer, it’ll not only accumulate more biomass and nitrogen than red clover by winter, but you can also get a more lavish regrowth than the crimson/white clover the following spring,” says Yang.

“Hairy vetch is also very easy to terminate,” he says, adding that the plant’s reputation as a weed that can’t be controlled seems undeserved, as it was found in this study to be easy to establish and kill.

Strip tillage was used for the first time over the last two years, and it seemed to work very well in terms of improving the quality of the seed bed for hairy vetch and enhancing corn response to legume nitrogen.

Overall, Yang highly recommends hairy vetch as a cover crop after winter wheat in southwestern Ontario.

“If you want a stable and reliable legume nitrogen credit for your corn, use hairy vetch and plow it down as late in the fall as you can,” he says. “If you want a maximum nitrogen credit, use hairy vetch as a cover crop and then terminate it in spring before corn planting.”


Dr. Reynolds is evaluating soil physical health properties — including organic carbon content (OC), bulk density (hardness of the soil), plant available air capacity (PAAC), plant available water capacity (PAWC), and permeability (how easy water moves through soil).

“Near-surface OC was always greater under no-till than under moldboard plow,” he says. In the cover crop phase, OC increases to about two per cent, but in the corn phase, it declines back down to about 1.5 to 1.8 per cent. Both are on the low side — optimal OC on these clay loam soils for crop growth is three to five per cent, and tillage of heavy soils may cause loss of structure when OC is less than about 2.3 per cent.

“Cover crops haven’t yet delivered on OC levels,” Reynolds says, adding that more years of data are required to get a good overall picture. He notes that there is virgin Brookston clay loam soil in a woodlot adjacent to the experiment that has about six per cent organic carbon.

“When you dig into the woodlot soil, it’s black as coal with a nice crumb structure, and it falls apart in your hand,” he says. “So, there’s clearly lots of room for improvement — we know this soil can have high organic carbon levels, we just have to figure out how to do that and grow crops too.”

In terms of bulk density or hardness, the soil was consistently lower under cover crops than under corn – for all tillage systems. The optimal range for soil bulk density is about 0.9 to 1.2 megagrams per cubic metre, and the near-surface soil under cover crops is regularly at the top of that range. In the corn, soil density increases to about 1.4 — a hardness level that starts to restrict root growth in most clay loams, Reynolds says.

“Roots need air to function,” he says, noting that the soil’s near-surface plant available air capacity (PAAC) was at about 15 per cent under cover crops, but down to 10 to 12 per cent during the corn phase.

He says that crops in fine-textured soils become susceptible to aeration deficits once soil air capacity gets below about 14 per cent. The ideal PAAC for crops is about 20 per cent — which is frequently the case in sandier soils.


Plant available water capacity (PAWC) indicates the ability of a soil to store water that can be used by crops.

“What’s interesting is that even though Brookston clay loam can hold a lot of water, typically less than half of that water is available to crops,” he says.

PAWC was consistently greater under cover crops (10 to 15 per cent) than corn (below 10) however, ideal PAWC is about 20 per cent, while less than 10 per cent can make the soil droughty. Water availability is a tug of war between the soil and the crop, and the soil always gets the upper hand in the end, he says.

In terms of permeability, Reynolds says he didn’t see any clear differences between cover crops and corn. This was likely caused by the many cracks, worm holes, and root channels that are typically present in the near-surface of Brookston clay loam soil.

Reynolds is surprised that the soil improvements accrued under cover crops largely disappear during the following corn year. “The benefits just don’t hang around,” he says, noting again that it might be a function of the short timeline of the experiment.

He feels that perhaps timed sampling of the soil — at different periods during the growing season — might clarify what is going on.

This article features research funded by Grain Farmers of Ontario.


  • 1 Terminology
  • 2 History
  • 3 Uses
    • 3.1 Human consumption
      • 3.1.1 Nutritional value
    • 3.2 Forage
    • 3.3 Other uses
    • 3.4 Classification
  • 4 Pollination
  • 5 Nitrogen fixation
  • 6 Distribution and production
    • 6.1 Storage
  • 7 Pests and diseases
  • 8 International Year of Pulses
  • 9 See also
  • 10 References
  • 11 Further reading
  • 12 External links

The term pulse, as used by the United Nations' Food and Agriculture Organization (FAO), is reserved for legume crops harvested solely for the dry seed. [1] This excludes green beans and green peas, which are considered vegetable crops. Also excluded are seeds that are mainly grown for oil extraction (oilseeds like soybeans and peanuts), and seeds which are used exclusively for sowing forage (clovers, alfalfa). However, in common usage, these distinctions are not always clearly made, and many of the varieties used for dried pulses are also used for green vegetables, with their beans in pods while young.

Some Fabaceae, such as Scotch broom and other Genisteae, are leguminous but are usually not called legumes by farmers, who tend to restrict that term to food crops.

Archaeologists have discovered traces of pulse production around Ravi River (Punjab), the seat of the Indus Valley Civilisation, dating to c. 3300 BCE. Meanwhile, evidence of lentil cultivation has also been found in Egyptian pyramids and cuneiform recipes. [2] Dry pea seeds have been discovered in a Swiss village that are believed to date back to the Stone Age. Archaeological evidence suggests that these peas must have been grown in the eastern Mediterranean and Mesopotamian regions at least 5,000 years ago and in Britain as early as the 11th century. [3] The soybean was first domesticated around 5,000 years ago in China from a descendant of the wild vine Glycine soja. [4]

In the United States, the domesticated soybean was introduced in 1770 by Benjamin Franklin after he sent seeds to Philadelphia from France. Henry Ford, a vegetarian, was the first person to use soybeans for large-scale industrial purposes. Concentrating on his company, from 1932 to 1933 he invested over 1 million dollars in research on soybeans. Prior to World War II, 40% of cooking oil was imported into the US. When the war came, supply routes were disrupted, which encouraged the soybean culture in the US. Due to the years of research done by Henry Ford, the domestic soybean oil industry was born. [5] Between 1970 and 1976, soybean production increased approximately 30%. Oil yield from bulk soybeans averages about 18%. Its modern-day usage ranges from margarine, salad oils, shortening and the previously mentioned cooking oil. [6]

Farmed legumes can belong to many agricultural classes, including forage, grain, blooms, pharmaceutical/industrial, fallow/green manure, and timber species. Most commercially farmed species fill two or more roles simultaneously, depending upon their degree of maturity when harvested.

Human consumption Edit

Grain legumes [7] are cultivated for their seeds, which are used for human and animal consumption or for the production of oils for industrial uses. Grain legumes include beans, lentils, lupins, peas, and peanuts. [8]

Legumes are used as a key ingredient in vegan meat and dairy substitutes. They are growing in use as a plant-based protein source in the world marketplace. [9] [10] Products containing legumes grew by 39% in Europe between 2013 and 2017. [11]

Nutritional value Edit

Legumes are a significant source of protein, dietary fiber, carbohydrates and dietary minerals for example, a 100 gram serving of cooked chickpeas contains 18 percent of the Daily Value (DV) for protein, 30 percent DV for dietary fiber, 43 percent DV for folate and 52 percent DV for manganese. [12]

Legumes are also an excellent source of resistant starch which is broken down by bacteria in the large intestine to produce short-chain fatty acids (such as butyrate) used by intestinal cells for food energy. [13]

Preliminary studies in humans include the potential for regular consumption of legumes in a plant-based diet to reduce the prevalence or risk of developing metabolic syndrome. [14] There is evidence that a portion of pulses (roughly one cup daily) in a diet may help lower blood pressure and reduce LDL cholesterol levels, though there is a concern about the quality of the supporting data. [15] [16] Further studies have suggested that high legume consumption is associated with a lower risk of all-cause mortality. [17]

Forage Edit

Forage legumes are of two broad types. Some, like alfalfa, clover, vetch (Vicia), stylo (Stylosanthes), or Arachis, are sown in pasture and grazed by livestock. Other forage legumes such as Leucaena or Albizia are woody shrub or tree species that are either broken down by livestock or regularly cut by humans to provide livestock feed. Legume-based feeds improve animal performance compared to a diet of perennial grasses. Factors to which this is attributed are larger consumption, faster digestion and higher feed conversion rate. [18]

The type of crop(s) grown or animal rearing will be dependent on the farming system, either vegetables, tubers, grains, cattle etc. In cattle rearing, legume trees such as Gliricidia sepium can be planted along edges of field to provide shade for cattle, the leaves and bark are often eaten by cattle. Green manure can also be grown between periods when crops of economic importance are harvested prior to the next crops to be planted. [19]

Other uses Edit

Legume species grown for their flowers include lupins, which are farmed commercially for their blooms as well as being popular in gardens worldwide. Industrially farmed legumes include Indigofera and Acacia species, which are cultivated for dye and natural gum production, respectively. Fallow/green manure legume species are cultivated to be tilled back into the soil in order to exploit the high levels of captured atmospheric nitrogen found in the roots of most legumes. Numerous legumes farmed for this purpose include Leucaena, Cyamopsis, and Sesbania species. Various legume species are farmed for timber production worldwide, including numerous Acacia species and Castanospermum australe.

Legume trees like the locust trees (Gleditsia, Robinia) or the Kentucky coffeetree (Gymnocladus dioicus) can be used in permaculture food forests. Other legume trees like laburnum and the woody climbing vine wisteria are poisonous.

Classification Edit

FAO recognizes 11 primary pulses. The FAO notes that the term "pulses" is limited to legumes harvested solely for dry grain, thereby excluding legumes that are harvested green for food (green peas, green beans, etc.) which are classified as vegetable crops. Also excluded are those legumes used mainly for oil extraction (e.g., soybeans and groundnuts) or used exclusively for sowing purposes (e.g., seeds of clover and alfalfa). [20]

  1. Dry beans (FAOSTAT code 0176, Phaseolus spp. including several species now in Vigna)
    • Kidney bean, navy bean, pinto bean, black turtle bean, haricot bean (Phaseolus vulgaris)
    • Lima bean, butter bean (Phaseolus lunatus)
    • Adzuki bean, azuki bean (Vigna angularis)
    • Mung bean, golden gram, green gram (Vigna radiata)
    • Black gram, urad (Vigna mungo)
    • Scarlet runner bean (Phaseolus coccineus)
    • Ricebean (Vigna umbellata)
    • Moth bean (Vigna aconitifolia)
    • Tepary bean (Phaseolus acutifolius)
  2. Dry broad beans (code 0181, Vicia faba)
    • Horse bean (Vicia faba equina)
    • Broad bean (Vicia faba)
    • Field bean (Vicia faba)
  3. Dry peas (code 0187, Pisum spp.)
    • Garden pea (Pisum sativum var. sativum)
    • Protein pea (Pisum sativum var. arvense)
  4. Chickpea, garbanzo, Bengal gram (code 0191, Cicer arietinum)
  5. Dry cowpea, black-eyed pea, blackeye bean (code 0195, Vigna unguiculata)
  6. Pigeon pea, Arhar/Toor, cajan pea, Congo bean, gandules (code 0197, Cajanus cajan)
  7. Lentil (code 0201, Lens culinaris)
  8. Bambara groundnut, earth pea (code 0203, Vigna subterranea)
  9. Vetch, common vetch (code 0205, Vicia sativa)
  10. Lupins (code 0210, Lupinus spp.)
  11. Pulses NES (code 0211), Minor pulses, including:
    • Lablab, hyacinth bean (Lablab purpureus)
    • Jack bean (Canavalia ensiformis), sword bean (Canavalia gladiata)
    • Winged bean (Psophocarpus tetragonolobus)
    • Velvet bean, cowitch (Mucuna pruriens var. utilis)
    • Yam bean (Pachyrhizus erosus)

Legumes can either be self-pollinated or cross-pollinated.

Some tropical legumes that are closely self-pollinated are: Macroptilium atropurpureum 'Siratro', Macroptilum lathyroides, Centrosema pubescens, Neonotonia wightii, and Lotononis bainesii. However, the autogamous annual Stylosanthes humilis proved otherwise by adapting in response to changing conditions during an experiment, and was found to be composed of several genotypes showing heterogeneity.

Two legumes used for pasture with cross-pollination are: Desmodium intortum and Desmodium uncinatum. When the flower is opened, this is the only time fertilization will take place. These two species' characteristics vary in morphology and ruggedness. [21]

Many legumes contain symbiotic bacteria called Rhizobia within root nodules of their root systems (plants belonging to the genus Styphnolobium are one exception to this rule). These bacteria have the special ability of fixing nitrogen from atmospheric, molecular nitrogen (N2) into ammonia (NH3). [22] The chemical reaction is:

Ammonia is then converted to another form, ammonium (NH +
4 ), usable by (some) plants by the following reaction:

This arrangement means that the root nodules are sources of nitrogen for legumes, making them relatively rich in plant proteins. All proteins contain nitrogenous amino acids. Nitrogen is therefore a necessary ingredient in the production of proteins. Hence, legumes are among the best sources of plant protein.

When a legume plant dies in the field, for example following the harvest, all of its remaining nitrogen, incorporated into amino acids inside the remaining plant parts, is released back into the soil. In the soil, the amino acids are converted to nitrate (NO −
3 ), making the nitrogen available to other plants, thereby serving as fertilizer for future crops. [23] [24]

In many traditional and organic farming practices, crop rotation involving legumes is common. By alternating between legumes and non-legumes, sometimes planting non-legumes two times in a row and then a legume, the field usually receives a sufficient amount of nitrogenous compounds to produce a good result, even when the crop is non-leguminous. Legumes are sometimes referred to as "green manure".

Sri Lanka developed the farming practice known as coconut-soybean intercropping. Grain legumes are grown in coconut (Cocos nuficera) groves in two ways: intercropping or as a cash crop. These are grown mainly for their protein, vegetable oil and ability to uphold soil fertility. [25] However, continuous cropping after 3–4 years decrease grain yields significantly. [26]

Legumes are widely distributed as the third-largest land plant family in terms of number of species, behind only the Orchidaceae and Asteraceae, with about 751 genera and some 19,000 known species, [27] [28] constituting about seven percent of flowering plant species. [29] [30]

Storage Edit

Seed viability decreases with longer storage time. Studies done on vetch, broad beans, and peas show that they last about 5 years in storage. Environmental factors that are important in influencing germination are relative humidity and temperature. Two rules apply to moisture content between 5 and 14 percent: the life of the seed will last longer if the storage temperature is reduced by 5 degree Celsius. Secondly, the storage moisture content will decrease if temperature is reduced by 1 degree Celsius. [31]

A common pest of grain legumes that is noticed in the tropical and subtropical Asia, Africa, Australia and Oceania are minuscule flies that belong to the family Agromyzidae, dubbed "bean flies". They are considered to be the most destructive. The host range of these flies is very wide amongst cultivated legumes. Infestation of plants starts from germination through to harvest, and they can destroy an entire crop in early stage. [32] Black bean aphids are a serious pest to broad beans and other beans. Common hosts for this pest are fathen, thistle and dock. Pea weevil and bean weevil damage leaf margins leaving characteristics semi-circular notches. Stem nematodes are very widespread but will be found more frequently in areas where host plants are grown. [33]

Common legume diseases include anthracnose, caused by Colletotrichum trifolii common leaf spot caused by Pseudomonas syringae pv. syringae crown wart caused by Physoderma alfalfae downy mildew caused by Peronospora trifoliorum fusarium root rot caused by Fusarium spp. rust caused by Uromyces striatus sclerotina crown and stem rot caused by Sclerotinia trifoliorum Southern blight caused by Sclerotium rolfsii pythium (browning) root rot caused by Pythium spp. fusarium wilt caused by Fusarium oxysporum root knot caused by Meloidogyne hapla. These are all classified as biotic problems. [34]

Abiotic problems include nutrient deficiencies, (nitrogen, phosphorus, potassium, copper, magnesium, manganese, boron, zinc), pollutants (air, water, soil, pesticide injury, fertilizer burn), toxic concentration of minerals, and unfavorable growth conditions. [35]

The International Year of Pulses 2016 (IYP 2016) was declared by the Sixty-eighth session of the United Nations General Assembly. [36] The Food and Agriculture Organization of the United Nations was nominated to facilitate the implementation of IYP 2016 in collaboration with governments, relevant organizations, non-governmental organizations and other relevant stakeholders. Its aim was to heighten public awareness of the nutritional benefits of pulses as part of sustainable food production aimed towards food security and nutrition. IYP 2016 created an opportunity to encourage connections throughout the food chain that would better use pulse-based proteins, further global production of pulses, better use crop rotations and address challenges in the global trade of pulses. [36] [37]