Peas are a valuable legume crop which is grown on farms and in market gardens. Being legumes, they produce root nodules and are able to convert nitrogen from the air into nitrates which can be utilised by the plant. This process is carried out by the bacteria which live in the root nodules. Due to this, they improve the soil and make it more fertile.
There are many different kinds and varieties of peas and this lecture will deal with three kinds in order to give provide you with examples. These are the edible peas which are grown for human consumption, and harvested in pods. They are sold as fresh green peas to the public or canning factories where they are canned and sold as tinned peas, or frozen and sold packaged, or harvested, dried and sold as dried peas. The stalks or haulms as they are called can be fed to cattle either green or dried as hay.
The second example is the chickpea which is used either for human consumption or fed to cattle and the haulms used as stockfeed fed either as fresh or dried hay. Pigeon peas or dhal can be used for human consumption but are mainly grown as cattle feed. All types of peas can be grown as a green manure as the crop is a legume which provides a very valuable type of green manure and not only supplies nutrients to the soil, particularly nitrogen, but also improves the soil structure greatly.
2. EDIBLE PEAS
This crop does not thrive in hot conditions preferring a cool season, but has a moderate tolerance to frost. The flowers of peas are very sensitive to frost. They should be grown on the same land once every 3 years to prevent a build‐up of disease.
There are a number of varieties which vary in pod length, number of peas in the pods and the height reached by the mature plant. The tall varieties need to be held up by means of stay wire or sticks and these are best suited to market gardens. The small and medium varieties grow to a height of 0.5 metres and the tall varieties will reach 1.5 metres. In general the tall varieties produce more pods and so provide a heavier yield than the small varieties. Examples are given below of some varieties available:
Green‐feast: Medium‐sized peas high in sugar. They are a small variety that grows to aheight of 0.6 m.
Onward: Produces larger pods and grown to a height, approximately 0.75 m.
Cape Freezer: Grown for deep freezing.
Peas do not like soil which is too acid and do best with a soil pH between 5.5 ‐ 6.0. If the soil is too acid, fertiliser lime should be applied 3 months before the crop is planted. As edible peas are grown for sale, (e.g. as a cash crop), it pays to apply fertiliser although being a legume not much nitrogen is required.
An initial dressing of 250 kg/ha to 500 kg/ha of 2:3:4(30), (depending on soil fertility) can be put onto the seedbed at planting. A topdressing application of LAN can be applied at 4 weeks and this should be between 25 kg/ha and 75 kg/ha.
Fertiliser should not come into direct contact with the seeds as it causes major damage.
The seed should be dressed with Thiram seed dressing at the rate of 2 grams per kilogramme of seed. As peas are legumes, the seed should also be dressed with an inoculant (Rhizobium) of the correct strain of bacteria for the crop. This can be obtained from any seed merchant such as the Farmers Co‐op. The seed should be planted into a fairly fine seedbed at the rate of 50 – 100 kg of seed per hectare and a depth of 20 mm on heavy soils and 40 mm on light soils. Seeds should be approximately 50 mm apart in rows and the rows should be 600 mm – 750 mm apart. Planting can be done by hand, maize planter or using a wheat drill.
Figure 1: Plant spacing
Since edible peas prefer a cool climate they are usually grown in winter under irrigation. The time of planting in most areas is from May to June. Areas where late frost or cool summers are experienced can be planted in July. Cool frost free areas can be planted in March. Plants should not be over‐ watered during growth and should not suffer from a lack of water during the flowering and pod filling period. Weeds should be killed either by herbicide or by inter‐row cultivation which should be shallow to avoid damaging the roots of the growing plant.
PEST AND DISEASES
Peas are affected by the common fungal diseases which are why they are best suited to growing during the winter ‐ avoid overwatering. Some of the diseases are Ascochyta leaf and stem and pod rot which occur in moist conditions. Downey mildew occurs on young growing plants and Powdery mildew on plants bearing pods. A number of pests, notably cutworms, mites and nematodes also attack the crop. Nematodes can be avoided by not growing peas too often on the same piece of land and other pests can be dealt with using normal pest control methods. (See Agronomy and Plant Nutrition Course).
Usually done by hand‐picking the pods as they ripen. The first picking can be made 8 – 10 weeks after planting and a further 3 to 4 can be done at 3 day intervals. The harvesting period should last 2
– 2 and a half weeks. The peas should be sent to market, the canning or freezing factory as soon as possible after picking. They should certainly be sent within 24 hours as they quickly lose their freshness. Yield of peas should be 5 – 6 tonnes per ha for a well‐grown, properly fertilised crop.
Chick pea is an erect or spreading annual legume, 30 to 70 cm tall and includes primary, secondary and tertiary branches and eventually resembles a bush. Chick pea is one of the oldest and most widely grown grain legume crops in the Middle and Far East. The crop was known in Turkey since 5450 years B.C., and its cultivation in the Nile Valley of Egypt was started by the Pharaonic New Kingdom (1 580 – 1 100 B.C). It appears to have originated in South‐west Asia, although Ethiopia may be considered as a possible area of origin. It may have spread at a very early date to India and Europe. The crop is now grown in America and Australia but is of little importance in these areas.
The total cultivated area of chick pea was estimated to be 10 000 000 hectares in 1973, producing 6 000 000 tonnes mainly in India and Pakistan.
Varieties vary greatly in maturity and characteristics. Generally the larger seeds fetch a higher price size being an inherited factor and only slightly affected by the growing conditions.
Chickpeas are reported to be a drought‐resistant crop requiring a cool dry climate. Under hot wet conditions it often fails to flower. It grows well on a wide range of soils with pH values varying from 6 to 7.0 (CaCL2). The presence of high amounts of free calcium carbonate in the soil usually has an adverse effect on its cooking quality. It requires a mean annual rainfall of between 400 – 600 mm.
The crop is generally grown in summer conditions but does well under irrigation. Sowing depth is 2.5
– 5 cm, with a row spacing of 100 cm and an in‐row spacing of 15 cm. Emergence is after 10 – 12 days but shallower planting will give a more rapid emergence provided moisture is not lacking. An initial nitrogen application at sowing (a so‐called starter of about 25 kg/ha N) is beneficial and good results have been achieved from applications of fertiliser phosphorus.
Yields vary considerably among varieties and with different conditions. It seems that brown seed types (1700 kg/ha) yield on average more highly that green seeded types (1200 kg/ha). Under optimum conditions, higher yields have been obtained. In Queensland, Australia, winter sown (May) chickpeas have yielded 4000 kg/ha, and yields between 2000 and 3000 kg/ha were recently obtained in Zimbabwe in preliminary observation trials.
PESTS AND DISEASES
This crop is not greatly troubled by diseases although the blight and wilt fungal diseases cause problems. Blight diseases are more serious particularly where rainfall and relative humidity are high during the growing season. Blight affects all foliar parts and is seed‐borne. The crop can also be infected by wilt, stem‐rot and rust. Chick pea is susceptible to a number of pests both in the field and in storage. Other insects causing problems are cutworms, semi‐looper, and leaf minor flies.
USE AND IMPORTANCE
Whole dried seeds contains on average 9.9% moisture, 17.1% protein, 5.3% fat, 61.2% carbohydrate, 3.9% fibre and 2.7% ash. Protein content varies between varieties but can reach values of 20 %. Chick pea protein is a good source of all amino acids except tryptophan and methionine and it compares favourably with soya bean protein. The seeds are rich in lysine and are a good source of vitamins such as A and B (riboflavin), B1 (thiamine), C (ascorbic acid), nicotinamide and the minerals calcium, phosphorus and iron.
Chick peas are mainly used for human consumption. In India they are eaten as whole roasted peas and as split peas. They are also eaten in soup, as leavened flat bread or in flour form as the basic ingredient in the preparation of a variety of sweets and savoury preparations. The green pods and
tender shoots are also utilised as a vegetable. In Chile a cooked chick pea milk beverage preparation proved to be very good for the feeding of infants and for effective control of diarrhoea.
The stover remaining after harvest is useful as a livestock feed and should be chopped up and mixed with other cereal crops.
4. PIGEON PEA or DHAL
This crop is also known as Congo pea, Angola pea, Gungo pea, no‐eye pea, red grain and dhal. Pigeon pea is an erect perennial or annual bushy shrub reaching up to 4 m high. It is woody at the base with ribbed downy stems. The plant has a deep tap root. Pods are 5 to 8 cm long and certain 4 to 8 seeds.
The origin is not exactly known but probably originated in Africa. Seeds have been found in Egyptian tombs of the Twelfth Dynasty indicating that the crop was known in Egypt between 2 400 and 2 200 B.C. It is also believed to have been cultivated in Asia for more than 3000 years. The crop was established in Madagascar in very ancient times and introduced to India in pre‐historic days. As a result India is now considered as the centre of diversity. Pigeon pea is widely grown in tropical and subtropical countries, the main ones being India, Burma, Uganda, Malawi, Venezuela and Puerto Rico.
In 1974, the estimated area cultivated to pigeon pea was 2 883 000 000 hectares with a total production of 1 504 000 000 tonnes and an average yield of 541 kg/ha. Of this total 2 560 000 000 ha were cultivated in India alone, 147 000 ha in Africa and 36 000 ha in Latin America.
Varieties vary greatly in maturity characteristics, yield potential and photoperiodicity. There are also indeterminate types and determinate types. The former flower over extensive periods and at any one time may well have all stages from buds to mature pods. The determinate characters crop is usually harvested by repeated pickings of mature seed, this growth habit being ideally suited to peasant conditions. Recent work in Australia and India has resulted in the selection of early flowering dwarf lines which are suited to intensive mechanical cultivation.
The pigeon pea is a deep‐rooted plant capable of growing over a wide range of climatic and soil conditions. Soil pH should be between 5 and 7 with a soil moisture content of 40 – 50% for optimum germination. Pigeon peas also require rainfall of 600 – 1000 mm for optimum growth and temperatures of between 18 and 30°C. It is drought‐resistant and grows well under semi‐arid conditions. It is intolerant of water‐logging and very sensitive to frost. Pigeon pea can be grown as a pure stand for seed, cover or fodder, and is often inter‐cropped with sorghum, millet, maize, and cotton. Generally pigeon pea is planted in rows with 1 row of pigeon peato 4‐5 rows of the main crop the latter being harvested first. Growth is very slow in the initial stages but requires little care. It can be grown as a perennial plant for 3 to 4 years. The planting date of pigeon peas should be from October through to December.
Information on fertiliser response is rather poor although responses have been achieved to applied phosphorus and potassium.
Under primitive farming conditions yields are low (500 kg/ha) but under improved management yields of 2500 kg/ha have been achieved. Intensive management with dwarf varieties have produced yields of 5000 kg/ha. Once harvested, the plants can be used as fodder for animals.
PESTS AND DISEASES
Pigeon pea can be infected by fungal, bacterial and viral diseases. The important fungal diseases are rust, wilt, and collar and stem canker.
Leaf‐hoppers and pod‐hoppers are among the serious insect pest of the crop.
The seeds have high protein content and are rich in vitamins particularly in riboflavin and niacin. They are a good source of phosphorus, calcium, magnesium, sodium, iron, copper, zinc and magnesium.
The average protein content is 22%, although some lines have a protein content exceeding 30%. The protein value of the plant is equal to that of Lucerne.
Pigeon pea is useful in a variety of ways being used for human consumption, as an animal feed, green manure and cover crop for treating different ailments. The late‐maturing woody types can be used for fuel and as temporary shade plants for coffee, tea or cocoa.
Pigeon pea is used extensively in folk medicine. It is also claimed that seeds have slightly narcotic properties. Excessive consumption of the raw seeds seems to induce sleepiness without any serious consequences. Green but fully developed pods may be canned, freeze‐dried or frozen, but the pigeon pea is mainly used as dry seed, processed as dhal.