Sunday, January 15, 2012

Peas Cultivation


Scientific classification
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Kingdom         : Plantae
(unranked)       : Angiosperms
(unranked)       : Eudicots
(unranked)       : Rosids
Order              . Fabales
Family              : Fabaceae
Subfamily         : Faboideae
Tribe                : Vicieae
Genus               : Pisum
Species             : P. sativum
Binomial name   : Pisum sativum  L.

A pea is most commonly the small spherical seed or the seed-pod of the pod fruit Pisum sativum. Each pod contains several peas. Peapods are botanically a fruit, since they contain seeds developed from the

ovary of a (pea) flower. However, peas are considered to be a vegetable in cooking. The name is also used to describe other edible seeds from the Fabaceae such as the pigeon pea (Cajanus cajan), the cowpea (Vigna unguiculata), and the seeds from several species of Lathyrus.

P. sativum is an annual plant, with a life cycle of one year. It is a cool season crop grown in many parts of the world; planting can take place from winter to early summer depending on location. The average pea weighs between 0.1 and 0.36 grams. The species is used as a vegetable, fresh, frozen or canned, and is also grown to produce dry peas like the split pea. These varieties are typically called field peas.

The wild pea is restricted to the Mediterranean basin and the Near East. The earliest archaeological finds of peas come from Neolithic Syria, Turkey and Jordan. In Egypt, early finds date from ca. 4800–4400 BC in

the Nile delta area, and from ca. 3800–3600 BC in Upper Egypt. The pea was also present in Georgia in the 5th millennium BC. Farther east, the finds are younger. Peas were present in Afghanistan ca. 2000 BC, in Harappa, Pakistan, and in northwest India in 2250–1750 BC. In the second half of the 2nd millennium BC, this pulse crop appears in the Gangetic basin and southern India.

Origin
Pea probably originated in southwestern Asia, possibly northwestern India, Pakistan or adjacent areas of former USSR and Afghanistan and thereafter spread to the temperate zones of Europe (Kay, 1979; Makasheva, 1983). Based on genetic diversity, four centers of origins, namely, Central Asia, the Near East, Abyssinia and the Mediterranean have been recognized . Non-pigmented peas to be used as a vegetable were grown in United Kingdom in the middle Ages . Pea was introduced into the Americas soon after Columbus and a winter type pea was introduced from Austria in 1922. Pea was taken to China in the first century . Peas were reported to be originally cultivated as a winter annual crop in the Mediterranean region.

Description

The pea is a most commonly green, occasionally purple or golden yellow, pod-shaped vegetable, widely grown as a cool season vegetable crop. The seeds may be planted as soon as the soil temperature reaches 10 °C (50 °F), with the plants growing best at temperatures of 13 to 18 °C (55 to 64 °F). They do not thrive in the summer heat of warmer temperate and lowland tropical climates, but do grow well in cooler, high altitude, tropical areas. Many cultivars reach maturity about 60 days after planting.

Raw Green PeaNutritional value per 100 g (3.5 oz)
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Energy                             339 kJ (81 kcal)
Carbohydrates                14.5 g
- Sugars                           5.7 g
- Dietary fibre                  5.1 g
Fat                                  0.4 g
Protein                            5.4 g
Vitamin A equiv.              38 μg (5%)
- beta-carotene              449 μg (4%)
- lutein and zeaxanthin  2593 μg
Thiamine (vit. B1)        0.3 mg (26%)
Riboflavin (vit. B2)      0.1 mg (8%)
Niacin (vit. B3)           2.1 mg (14%)
Pantothenic acid (B5) 0.1 mg (2%)
Vitamin B6                0.2 mg (15%)
Folate (vit. B9)           65 μg (16%)
Vitamin C                 40.0 mg (48%)
Calcium                    25.0 mg (3%)
Iron                            1.5 mg (12%)
Magnesium               33.0 mg (9%)
Phosphorus                108 mg (15%)
Potassium                   244 mg (5%)
Zinc                            1.2 mg (13%)
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Peas have both low-growing and vining cultivars. The vining cultivars grow thin tendrils from leaves that coil around any available support and can climb to be 1–2 m high. A traditional approach to supporting climbing peas is to thrust branches pruned from trees or other woody plants upright into the soil, providing a lattice for the peas to climb. Branches used in this fashion are sometimes called pea brush. Metal fences, twine, or netting supported by a frame are used for the same purpose. In dense plantings, peas give each other some measure of mutual support. Pea plants can self-pollinate.

Field Cultivation

Dry peas serve as rotational crops in the Palouse area in a state of eastern Washington and Northern Idaho. It is considered as an alternative to the cereal grain production and provides the basis to break disease cycles in winter wheat, improve soil fertility status and improve weed control. "Peas reduced the fertilizer requirements

of maize by 20-32 kg/ha in India compared with wheat or fallow, respectively; in France it was estimated that about 50 kg/ha of N are returned to the soil by peas" . Pea growing seasons vary from 80-100 days in semi-arid regions and up to 150 days in humid and temperate areas .

Peas are propagated only from seed. "At higher temperatures germination is rapid, but seedlings may die from various pathogens in the soil. As temperature rises during growing season, yield drops off rapidly. In New York, yields are highest when seeds are planted during first 2 weeks of April; for each 2-week delay in planting, yield of shelled peas decreased about 400 kg/ha" . Thorough preparation of soil is very important, especially when the seed is broadcast or planted with a grain drill, as no subsequent cultivation is given

thereafter. In the Palouse region of eastern Washington and northern Idaho peas are sown between March 25th at lower elevations to May 10th at higher elevations when the soil temperature is above 4°C; for planting winter peas, September 15th to the 30th has been recommended . Recommended plant densities vary tremendously depending on soil type, cultivar, seed size, and biotic factors, particularly diseases. In the Palouse area of Washington state, USA, spring peas are sown at the rate of 140-195 kg ha-1 or 89-108 seeds m-2, while fall sown peas are planted at the rate of 85-135 kg ha-1 or 71-104 seeds m-2 .

Peas are relatively unresponsive to fertilizers, particularly nitrogen; additions are necessary when nodulation is poor or fails completely. When the seeds are treated with the Rhizobium, care must be taken in the choice of fungicide seed treatments to prevent potential toxicity . The amount of nitrogen fixed through symbiosis with Rhizobia is reported to vary from 71 kg N per hectare in Alabama to 119 kg N per hectare in Wisconsin . The N concentration in pea leaf tissue is reported to range from 1.8 to 2.3% .

Harvesting

Peas grown for home use or for fresh market are picked by hand before the seeds are fully matured and still in the pod and are used for immediate consumption. In some cases, gardeners and commercial growers make two or three pickings, depending on maturity, while other growers make only one picking, in which the vines are pulled and all pods are removed. "Peas for processing are harvested with machines of various types.

Sometimes vines are cut with a mowing machine, windrowed and loaded onto trucks with a hay loader. Pea harvesters that mow the peas and load directly onto trucks are common in major pea growing areas. Pea vines are hauled to a vining station, where pods are separated from vines, after which seeds are separated from pods" . Current methods of processing pea harvest involve the use of "viners" that harvest the pods and remove the peas from the pods in one operation in the field. The peas are then transported to the processing plant where they are quickly processed. Dry peas are harvested when the pods are completely dry and can be threshed directly in the field by a combine. For dry peas timely harvest is important for maintaining quality and is usually done when the seed moisture content is less than 13%. Both premature harvesting and harvesting too late reduce the quality of the dry pea crop. If the pea crop is overmature, harvesting early in the morning or during the evening when relative humidity is low will minimize shattering and seed breakage .

Yields and Economics

Pea is among the four important cultivated legumes next to soybean, groundnut, and beans . Total world dry pea production rose from 8.127 million metric tons in 1979-81 to 14.529 million metric tons in 1994 while acreage varied from 7.488 to 8.060 million hectares for the same years . The highest productivity for pea was reported in France at 5088 kg per hectare in 1994, about eight times more than the African average yield. In 1994, USA total acreage was 54, 000 hectares with an average yield of 2587 kg per hectare . Important

production areas of the world include France, Russia, Ukraine, Denmark and United Kingdom in Europe; China and India in Asia; Canada and USA in North America; Chile in South America; Ethiopia in Africa, and Australia . "Throughout temperate regions both green and dried peas are an important garden and field crop. In the United States, ca. 550,000 MT are produced commercially for food annually, and ca. 200,000 MT of field peas for feed".

Pea is the predominant export crop in world trade and represents about 40% of the total trade in pulses . The major exporting countries, excluding the European Economic Commission (EEC), are Australia, Canada and the USA . Most of the peas from USA were exported to India, Haiti, Peru, and the Philippines in 1995 and had a total value of US$ 24,210,499 .

Biotic Factors

Peas are adversely affected by: Ascochyla pisi, Cladosporium pisicola (leaf spot or scab), Erysiphe polygoni (powdery mildew), Fusarium oxysporum (wilt), Peronospora pisi (downy mildew), Phythium sp. (pre emergence damping-off), Botrytis cinerea (grey mold), Aphanomyces euteiches (common root rot), Thielaviopsis basicola (black root rot), and Sclerotina sclerotiorum (sclerotina white mold). Pea Early Browning Virus (PEBV), Pea Enation Mosaic virus (PEMV), Pea Mosaic Virus (PMV), Pea top yellows (PTY), Pea seed-borne Mosaic Virus (PSbMV) and Pea Streak Virus (PSV) constitute diseases caused by viruses, while the most important bacterial disease is caused by Pseudomonas pisi (bacterial blight) .

Insect pests include Aphis cracivora (Groundnut aphid), Acyrthosiphon pisum (Pea aphid), Kakothrips robustus (Pea thrips), Bruchis pisorum (Pea seed beetle), Callosobruchus chinensis (Adzuki bean seed beetle), Apion sp. (Seed weevil), Sitona lineatus (Bean weevil), Contarina pisi (Pea midge), Helicoverpa armigera (African bollworm), Diachrysia obliqua (Pod borer), Agriotis sp. (Cut worms), Cydia nigricana (Pea moth), Phytomuza horticola (Leaf minor), Heliothis Zea (American bollworm), Etiella Zinckenella (Lima bean pod borer), Ophiomyia phaseoli (Bean fly), Delia platura (Bean seed fly), Tetranychus sp. (Spider mites), Pratylenchus penetrants (Root lesion nematodes), Ditylenchus dipsaci (Stem nematode), Heterodera goettingiana (Pea cyst nematode), and Meloidogyne javanica (Root knot nematode) .

Germplasm

Crop improvement depends on the germplasm diversity existing in the crop of interest. Pea and other cool season food legume crops are produced under the vagaries of stresses, both biotic and abiotic. Evaluation of the germplasm for these stress conditions is critical to sustained pea production. Also incorporation of new

traits into existing cultivars has been reported . To this effect, selection against devastating diseases such pea root rot caused by Aphanomyces euteches, fusarium wilt, downy and powdery mildew, virus resistance and insect resistance has been successful . Incorporation of traits available in germplasm collections into adapted backgrounds has been proposed and appropriate breeding methods have been suggested . "Assigned to the Near Eastern, Mediterranean, and African Centers of Diversity, peas are reported to exhibit tolerance to aluminum, disease, frost, fungus, hydrogen fluoride, high pH, heat, laterite, low pH, mildew, slope, smog, virus, and wilt" . The Regional Plant Introduction Station located at Pullman, Washington maintains a collection of 2800 pea accessions. There are at least 16 other gene banks reported to have a considerable number of pea accessions . Most of the genetic diversity present in peas is reported to be available in the Near East, Mediterranean region Central Asia and Ethiopia . The wild prototype of garden pea has never been found, but some writers believe that it was an ancient Egyptian plant. At present, it is grown throughout the world.

Varieties


There are many varieties (cultivars) of garden peas. Some of the most common include:

Alaska,                                                              55 days (smooth seeded)
Thomas Laxton/Laxton's Progress/Progress #9, 60-65 days
Mr. Big,                                                            60 days, 2000 AAS winner
Little Marvel,                                                     63 days, 1934 AAS winner
Early Perfection,                                                65 days (This variety is the foundation of many improved                                                                                varieties and crosses, including Dark-Seeded Early                                                                                        Perfection and Bolero, the latter being one of the most                                                                                    successful commercial varieties.)
Kelvedon Wonder,                                           65 days, 1997 RHS AGM winner
Homesteader/Lincoln,                                       67 days (heirloom, known as Greenfeast in AU, NZ)
Wando,                                                            68 days
Green Arrow,                                                   70 days
Tall Telephone/Alderman,                                 75 days (heirloom, tall climber)

Other variations of P. sativum include:
Pisum sativum var. macrocarpon is commonly known as the snow pea.
Pisum sativum var. macrocarpon ser. cv. is known as the sugar or snap pea.

Both of these are eaten whole before the pod reaches maturity and are hence also known as mange-tout, French for "eat all". The snow pea pod is eaten flat, while in sugar/snap peas, the pod becomes cylindrical, but is eaten while still crisp, before the seeds inside develop.

Pests and diseases

The pea leaf weevil (Sitona lineatus) is an insect that damages peas and other pod fruits. It is native to Europe, but has spread to other places such as Alberta, Canada. They are about 3.5 millimetres (0.14 in)—5.5 millimetres (0.22 in) long and are distinguishable by three light-coloured stripes running length-wise down the thorax. The weevil larvae feed on the root nodules of pea plants, which are essential to the plants' supply of nitrogen, and thus diminish leaf and stem growth. Adult weevils feed on the leaves and create a notched, "c-shaped" appearance on the outside of the leaves.

Use


Beneficial about Green Peas

Green peas is an exotic food in terms of nutrient composition. Because of their sweet taste and starchy texture, it is  known that green peas must contain some sugar and starch (and they do). But they also contain a unique assortment of health-protective phytonutrients. One of these phytonutrients--a polyphenol called coumestrol--has recently come to the forefront of research with respect to stomach cancer protection. A Mexico City-based study has shown that daily consumption of green peas along with other legumes lowers risk of stomach cancer (gastric cancer), especially when daily coumestrol intake from these legumes is approximately 2 milligrams or higher. Since one cup of green peas contains at least 10 milligrams of coumestrol, it's not difficult for us to obtain this remarkable health benefit.

The unique phytonutrients in green peas also provide us with key antioxidant and anti-inflammatory benefits. Included in these phytonutrients are some recently-discovered green pea phytonutrients called saponins. Due to their almost exclusive appearance in peas, these phytonutrients actually contain the scientific word for peas (Pisum) in their names: pisumsaponins I and II, and pisomosides A and B. When coupled with other phytonutrients in green peas--including phenolic acids like ferulic and caffeic acid, and flavanols like catechin and epicatechin--the combined impact on our health may be far-reaching. For example, some researchers have now speculated that the association between green pea and legume intake and lowered risk of type 2 diabetes may be connected not only with the relatively low glycemic index of green peas (about 45-50) and their strong fiber and protein content, but also with this unusual combination of antioxidant and anti-inflammatory phytonutrients.

Green peas stand out as an environmentally friendly food. Agricultural research has shown that pea crops can provide the soil with important benefits. First, peas belong to a category of crops called "nitrogen fixing" crops. With the help of bacteria in the soil, peas and other pulse crops are able to take nitrogen gas from the air and convert it into more complex and usable forms. This process increases nitrogen available in the soil without the need for added fertilizer. Peas also have a relatively shallow root system which can help prevent erosion of the soil, and once the peas have been picked, the plant remainders tend to break down relatively easily for soil replenishment. Finally, rotation of peas with other crops has been shown to lower the risk of pest problems. These environmentally friendly aspects of pea production add to their desirability as a regular part of our diet.

Even though green peas are an extremely low-fat food (with approximately one-third gram of total fat per cup) the type of fat and fat-soluble nutrients they contain is impressive. Recent research has shown that green peas are a reliable source of omega-3 fats in the form of alpha-linolenic acid (ALA). In one cup of green peas, you can expect to find about 30 milligrams of ALA. About 130 milligrams of the essential omega-6 fatty acid, linoleic acid, can also be found in a cup of green peas. This very small but high-quality fat content of green peas helps provide us with important fat-soluble nutrients from this legume, including sizable amounts of beta-carotene and small but valuable amounts of vitamin E.


Culinary use

 In early times, peas were grown mostly for their dry seeds. In modern times, however, peas are usually boiled or steamed, which breaks down the cell walls and makes the taste sweeter and the nutrients more bioavailable. Along with broad beans and lentils, these formed an important part of the diet of most people in the Middle East, North Africa and Europe during the Middle Ages. By the 17th and 18th centuries, it had become popular to eat peas "green", that is, while they are immature and right after they are picked. This was especially true in France and England, where the eating of green peas was said to be "both a fashion and a madness". New cultivars of peas were developed by the English during this time, which became known as "garden" or "English" peas. The popularity of green peas spread to North America. Thomas Jefferson grew more than 30 cultivars of peas on his estate. With the invention of canning and freezing of foods, green peas became available year-round, and not just in the spring as before.


Fresh peas are often eaten boiled and flavored with butter and/or spearmint as a side dish vegetable. Salt and pepper are also commonly added to peas when served. Fresh peas are also used in pot pies, salads and casseroles. Pod peas (particularly sweet cultivars called mange tout and "sugar peas", or the flatter "snow peas," called hé lán dòu,  in Chinese) are used in stir-fried dishes, particularly those in American Chinese cuisine.Pea  pods do not keep well once picked, and if not used quickly, are best preserved by drying, canning or freezing within a few hours of harvest.

In India, fresh peas are used in various dishes such as aloo matar (curried potatoes with peas) or matar paneer (paneer cheese with peas), though they can be substituted with frozen peas as well. Peas are also eaten raw, as they are sweet when fresh off the bush. Split peas are also used to make dhal, particularly in Guyana, and Trinidad, where there is a significant population of Indians.

Dried peas are often made into a soup or simply eaten on their own. In Japan, China, Taiwan and some Southeast Asian countries, including Thailand and Malaysia, peas are roasted and salted, and eaten as snacks. In the UK, dried yellow split peas are used to make pease pudding (or "pease porridge"), a traditional dish. In North America, a similarly traditional dish is split pea soup.

Pea soup is eaten in many other parts of the world, including northern Europe, parts of middle Europe, Russia, Iran, Iraq and India. In Sweden it is called ärtsoppa, and is eaten as a traditional Swedish food which predates the Viking era. This food was made from a fast-growing pea that would mature in a short growing season. Ärtsoppa was especially popular among the many poor who traditionally only had one pot and everything was cooked together for a dinner using a tripod to hold the pot over the fire.

In Chinese cuisine, pea sprouts  are commonly used in stir-fries. Pea leaves are often considered a delicacy, as well.

In Greece, Turkey, Cyprus, and other parts of the Mediterranean, peas are made into a stew with meat and potatoes.

In Hungary and Serbia, pea soup is often served with dumplings and spiced with hot paprika.

In the United Kingdom, dried, rehydrated and mashed marrowfat peas, known by the public as mushy peas, are popular, originally in the north of England, but now ubiquitously, and especially as an accompaniment to fish and chips or meat pies, particularly in fish and chip shops. Sodium bicarbonate is sometimes added to soften the peas. In 2005, a poll of 2,000 people revealed the pea to be Britain's seventh favourite culinary vegetable.

Processed peas are mature peas which have been dried, soaked and then heat treated (processed) to prevent spoilage—in the same manner as pasteurising. Cooked peas are sometimes sold dried and coated with wasabi, salt, or other spices.

Bioplastics

Bioplastics can be made using pea starch.

Nutritional value

Peas are high in fiber, protein, vitamins, minerals, and lutein. Dry weight is about one-quarter protein and one-quarter sugar. Pea seed peptide fractions have less ability to scavenge free radicals than glutathione, but greater ability to chelate metals and inhibit linoleic acid oxidation.

Peas in science

In the mid-19th century, Austrian scientist Gregor Mendel's observations of pea pods led to the principles of Mendelian genetics, the foundation of modern genetics.

Traditional Medicinal Uses

"Seeds are thought to cause dysentery when eaten raw. In Spain, flour is considered emollient and resolvent, applied as a cataplasm. It has been reported that seeds contain trypsin and chymotrypsin which could be used for contraceptive, ecbolic. fungistatic and spermicide". There are no significant amounts of toxicity or anti-metabolites in peas.Some people are allergic to peas, as well as lentils.

Etymology

According to etymologists, the term pea was taken from the Latin pisum, which is the latinisation of the Greek πίσον (pison), neut. of πίσος (pisos), "pea". It was adopted into English as the noun pease (plural peasen), as in pease pudding. However, by analogy with other plurals ending in -s, speakers began construing pease as a plural and constructing the singular form by dropping the "s", giving the term "pea". This process is known as back-formation.

The name "marrowfat pea" for mature dried peas is recorded by the Oxford English Dictionary as early as 1733. The fact that an export cultivar popular in Japan is called Maro has led some people to assume mistakenly that the English name "marrowfat" is derived from Japanese.

How to Select and Store

Only about 5% of the peas grown are sold fresh; the rest are either frozen or canned. When trying to decide between frozen and canned green peas, the following information may be helpful:
Frozen peas are better able to retain their color, texture, and flavor than canned peas. Recent research has confirmed that these "important sensory characteristics" of green peas are not affected by freezing over periods of 1-3 months.

Both canned and frozen peas may contain relatively high levels of sodium. Unless labeled as "low sodium" or "reduced sodium" or containing "50% less sodium" or something similar, you can expect to find 650-800 milligrams of sodium in one cup of canned green peas. Some of this sodium can be removed by thorough rinsing�and we definitely encourage you to do so. Reduced sodium canned peas will often bring the sodium content down to 250-300 milligrams of sodium. Even in this case, you can lower the sodium even further by thoroughly rinsing the peas. In the case of frozen green peas, it's not uncommon to find 300 milligrams of sodium in one cup of frozen green peas�approximately the same amount as found in reduced sodium canned peas. This relatively high sodium level in frozen peas results from green pea processing methods, not from the natural sodium content of the peas. When large batches of peas are prepared for freezing, producers separate out the older and starchier peas prior to freezing. A common method used to separate out the starchier peas is to immerse them in salty water. This process, called the salt brine process, allows the younger, more tender, and less starchy peas to float on top of the salt water, while letting the older, less tender, and starchier peas to sink to the bottom. Even though the younger and less starchy peas are rinsed with water after being separated out, they can still contain relatively high levels of sodium.

Neither frozen peas nor canned peas have an unlimited shelf life. In the case of frozen peas, it's not uncommon to see "use by" dates that indicate a 24-30 month shelf life. However, based on the overall research findings on nutrient content of frozen peas during storage, we recommend that you consume your frozen peas within 6-12 months of the packing date. (If no packing date is available, just make the "use by" date 50% sooner.)

Overall, we recommend the selection of frozen peas over canned peas and recognize the convenience of frozen over fresh. However, we also encourage you to consider fresh peas whenever possible, and to choose them according to the following guidelines.

When purchasing fresh garden peas, look for ones whose pods are firm, velvety and smooth. Their color should be a lively medium green. Those whose green color is especially light or dark, or those that are yellow, whitish or are speckled with gray, should be avoided. Additionally, do not choose pods that are puffy, water soaked or have mildew residue. The pods should contain peas of sufficient number and size that there is not much empty room in the pod. You can tell this by gently shaking the pod and noticing whether there is a slight rattling sound. All varieties of fresh peas should be displayed in a refrigerated case since heat will hasten the conversion of their sugar content into starch.

Unlike the rounded pods of garden peas, the pods of snow peas are flat. You should be able to see the shape of the peas through the non-opaque shiny pod. Choose smaller ones as they tend to be sweeter.

To test the quality of snap peas, snap one open and see whether it is crisp. They should be bright green in color, firm and plump.

Garden peas are generally available from spring through the beginning of winter. Snow peas can usually be found throughout the year in Asian markets and from spring through the beginning of winter in supermarkets. Snap peas are more limited in their availability. They are generally available from late spring through early summer.

If you will not be using fresh peas on the day of purchase, which is the best way to enjoy them, you should refrigerate them as quickly as possible in order to preserve their sugar content, preventing it from turning into starch. Unwashed, unshelled peas stored in the refrigerator in a bag or unsealed container will keep for several days. Fresh peas can also be blanched for one or two minutes and then frozen. If you decide to blanch and freeze your green peas, we recommend a maximum storage period of 6-12 months.





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