In this article we will discuss about:- 1. Introduction to Groundnut 2. Origin and History of Groundnut 3. Botanical Description 4. Geographic Distribution 5. Reasons for Low Yields 6. Important Features 7. Classification.
Contents:
- Introduction to Groundnut
- Origin and History of Groundnut
- Botanical Description of Groundnut
- Geographic Distribution of Groundnut
- Reasons for Low Groundnut Yields in India
- Important Features of Groundnut
- Classification of Groundnut
1. Introduction to Groundnut:
Groundnut, ‘the unpredictable legume’ is also known as earthnut, peanut, monkey nut and manilla nut. It is the 13th most important food crop and 4th most important oilseed crop of the world. The botanical name Arachis hypogaea L. has been derived from the Greek words, Arachis meaning a legume and hypogaea meaning below ground referring to geocarpic nature of pod formation.
Groundnut kernels have about 25% protein which is 1.3 times higher than meat, 2.5 times higher than eggs and 8 times higher than fruit. The oil content in kernels ranges from 40-50% and is extensively used for cooking (culinary oil) and for preparing vegetable oil (vanaspati). Its oil is also used for the preparation of soaps, cosmetics, cold cream and for various industrial uses.
Its oil is now used in pharmaceutical as a substitute to oleic oil. The groundnut is dug, extracted, processed, and consumed as a snack food, peanut butter, and a candy. Groundnut kernels are consumed directly as raw, roasted, boiled or fried. Groundnut haulms is a very good palatable (8-11% protein) fodder for cattle, when fed in green state. The groundnut cake have immense value as feeding material for livestock and organic manure. It contains 8% N, 1.4% P2O5 and 1.2% K2O.
The groundnut cake powder is used as laundry starch and in the manufacture of paper, gummed tapes and plastics. Groundnut shell is used as fuel and for manufacture of coarse boards, cork substitute and activated carbon. Groundnut shell is rich in potassium (1.5%) and calcium (3%), hence can be used as organic manure.
These multiple uses of groundnut plants makes it an excellent cash crop for domestic markets as well as for foreign trade in several developing and developed countries. Globally, 50% of the groundnut produced is used for oil extraction, 37% for confectionery use and 12% for seed purpose.
Groundnut being a leguminous crop, it has following advantages over other crops:
1. Being leguminous, groundnut has the ability to fix atmospheric nitrogen biologically into the soil which enriches the soil and this benefits the succeeding crop in rotation.
2. It is one crop which does not require much irrigation and can be cultivated on the residual soil moisture conditions.
3. It can provide gainful employment during the lean season.
4. Unlike the vegetables and fruits, which are highly perishable items, groundnuts can be stored for a long period of time and sold when prices are high.
5. It provides a very nutritive green fodder (haulms) and feed (oil cake) which can be fed to cattle and also used as organic manures.
6. Groundnut crop is considered not only as an oilseed crop but also as a food crop because its kernels are rich in protein contents and vitamins.
2. Origin and History of Groundnut:
Cultivated groundnut originates from South America. The Arachis genus was distributed in Argentina, Bolivia, Brazil, Paraguay and Uruguay with largest number of species reported from Brazil followed by Bolivia. Arachis hypogaea is believed to have originated in North Argentina and Southern Bolivia, where the diploid wild (progenitors of groundnut) species (A. batizocoi Krapov & W.C. Gregory Morten nudum and A. duranensis Krapov & W.C. Gregory nov. sp.) that are closely related to tetraploid A. hypogaea and A. monticola Krapov & Rigoni are distributed in this region.
This suggests that this region is the primary center of diversity. The secondary center of diversity includes Guarani region of Paraguay-Parana, Goias and Mina Gerais region of Tocatins, San Fransisco, Rondonia North-West Mato Grosso of Brazil, eastern foothills of the Andes and Bolivia and Peru’s upper Amazon and West Coast.
North East Brazil is considered as tertiary center of Diversity. The credit for the introduction of the groundnut into India belongs to the Jesuit Fathers who followed Vasco De Gama shortly after his first landing in India.
The flora of Western India includes a large number of specimens of South and Central American origin, introduced by missionaries. The so-called ‘indigenous’ variety in modern India was likely of Brazilian origin. Since South America was discovered in early 1500 A.D., it is probable that the plant was introduced into India at the earliest by the first half of the sixteenth century.
3. Botanical Description
of Groundnut:
The groundnut is a low growing annual plant. The groundnut plant has prostrated to upright stems that sometimes reach a height of 46 cm. The plant usually grows slowly until about 40 days after planting. Plants start flowering about 25-40 days after planting. Growth is more rapid between 40-100 days. During this period 4-5 fold increase in peanut foliage occurs.
After sowing seedling emerge in 5-10 days, depending on sowing depth and soil moisture. Bunch type does not possess seed dormancy. But seed of spreading types have a dormant period of 1-6 months, after harvest, depending on temperature and storage conditions. However, the dormancy can be broken by heat treatment or ethylene treatment.
Root:
The groundnut has a tap root with its laterals covering a depth of 35-40 cm and spread of 30-35 cm of radius.
Stem:
The groundnut stem is cylindrical, hairy and becomes more or less angular with age. The central stem is usually taller and has a few laterals which form main basis for classification of different varieties and forms.
Leaves:
The groundnut has a pinnately compound leaf with two pairs of leaflets. There is a pair of stipules about 4 cm long with long alternate points which are fused with the petiole for about 1 half of their length. The leaves occur alternatively 1 at each node. The shape of leaflets varies from elliptic, ovate to oblong with the entire or ciliate margins, subcardate base and obtuse or shortly mucronate tip.
Flowers:
Groundnut can flower (orange yellow in colour) over a long period depending on moisture availability, and temperature. Usually flowering takes place between 24-30 days after sowing and is little earlier in bunch than in spreading types. The flowering period normally
lasts for 3-8 weeks in case of bunch type and 6-10 weeks in case of spreading type. Three to five flowers are produced in the axils of leaves (near the base of the plant) on reproductive branches.
Groundnut is a completely self-pollinated crop i.e. its own pollen fertilizes the ovule. It is a unique plant because after pollination, the ovary elongates to produce a peg (gynophore, which contains fertilized ovules at the tip) that buries the ovary into the soil.
The peg is positively geotropic i.e., it grows towards the soil and penetrates into the soil. The peg penetrates the soil up to a depth of 7-8 cm. The ovary starts developing into a fruit (pod) after taking a horizontal position in the soil.
The pods are formed within 5-7 cm depth of surface soil and this is known as fruiting zone or pod zone. The pegs that are formed 15 cm above the soil surface usually fail to contact the soil and these will wither and hence their fertilized ovaries abort.
Normally 60-80 days are required for pod development from flowering to maturation in spreading types and slightly less than that (50- 60 days) in bunch types. Vegetative development declines during pod filling. Bunch type takes 85-100 days to mature and spreading cultivars mature in 110-130 days under warm conditions.
The mature fruit may normally contain upto 4 seeds depending on variety. Single seeded pods may be produced when all ovules but the proximal abort. Seedless fruits called ‘pops’ may be produced when calcium is limiting.
Groundnut plants flower profusely but the proportion of ovaries that develop into mature pods (pod-set %) is usually around 4-20% and is inversely related to the number of flowers produced. Only about 2/3rd of the total number of pods produced reach full maturity. While the percentage of pegs developing into pods decreases as the flowering period progresses.
Full maturation of a pod, from the first opening of the flower requires about 60 days. The pod formation and development of groundnut is greatly influenced by fertilizer application. Lime application causes better nodulation and pod development.
Naphthalene acetic acid (NAA) has marked effects on pod formation and development, when applied at flowering stage. This reduces flowering period, increases fertility of genotype, and improves the pod size, resulting in higher pod yield. This hormone is commercially available as planofix and vardhak, which is applied at 40 ppm 40 days after sowing.
Seed:
The fruit is an indehiscent pod containing 1-5 seeds. The shell of the pod which contains the seed is morphologically the pericarp, and the thin skin that covers the seed or nut is the testa. The nut is composed of 2 cotyledons which contain oil and other food materials.
4. Geographic Distribution of Groundnut:
Groundnut is the sixth most important oilseed crop in the world. It is one of the most popular and universal crops cultivated in more than 100 countries in six continents. It is grown in about 25.2 million ha worldwide with a total production of 36.44 million metric and an average productivity of 1454 kg/ha. Its cultivation is mostly confined to the tropical countries ranging from 40° N to 40° S. The most important groundnut producing countries are China, India, Nigeria, USA, Indonesia and Sudan.
Developing countries constitute 97% of the global area and 94% of the global production of this crop. The production of groundnut is concentrated in Asia and Africa (56% and 40% of the global area and 68% and 25% of the global production, respectively. India occupies the first place in regard to acreage, while China ranks first with regard to total production. Asia and Africa together accounts for over 90% of area and production in the world.
India is a World leader in groundnut farming, its cultivation has declined from 6.8 million ha in 1980-81 to 6.29 million ha in the year 2007-08. ON the other hand from 5 million tons in the year 1980-81, the production has increased to about 9.12 million tons by the year 2007-08.
It is the single largest source of edible oils in India and constitutes roughly about 50% of the total oilseed production. Groundnut is grown mostly in five states namely Gujarat, Andhra Pradesh, Karnataka, Tamil Nadu and Maharashtra, and together they account for about 90% of the crop’s total area.
Gujarat and Andhra Pradesh account for more than half of the cultivated area. The other important states are Madhya Pradesh, Rajasthan, Uttar Pradesh and Punjab. In a recent study, a comparison was made between the trends of groundnut cultivated area before (mid-sixties) and after the green revolution in India. The study revealed that there was a decline in the cultivation of groundnut from the beginning of the green revolution in the northern states mainly because of the increased emphasis on cereal production, wheat, and rice.
The current productivity of groundnut in India is about 14.59 q/ha. About twenty five years ago, the productivity level was about 736 kg/ha. In comparison to other countries, the productivity level in India is deplorably low mainly because about 80% of the crop is grown under rainfed conditions (with average productivity of 800 kg/ha), where drought takes a heavy toll apart from the yield loss due to a plethora of pests and diseases.
In contrast, winter/summer groundnut grown under irrigated/assured residual soil moisture gives almost double yield (1567 kg/ha). Among different States producing groundnut, Tamil Nadu tops the list with about 19.57 quintal per ha, which is five quintal more than the all-India average.
5. Reasons for Low Groundnut Yields in India
:
1. Low plant population because of high cost of seed, small and marginal farmers cannot afford the seed costs. Farmers are using low seed rate of groundnut as the seed requirement of groundnut is as high as 100-150 kg/ha; the low seed rate results in low plant population thereby affecting the productivity of groundnut.
2. Small farmers do not want to invest on seeds as the crop is exposed to vagaries of rainfall leading to uncertain yields. About 80% of groundnut is cultivated under rainfed conditions, thus productivity is mainly governed by monsoon behaviour.
3. Most of the farmers use local seed which may be of poor quality.
4. Being a rain fed crop lack of optimum soil moisture at the time of sowing affects germination.
5. Non-adoption of seed treatment against seed- borne diseases may lead to decay and death of seed/seedling.
6. Cultivated in marginal and poor soils of low fertility status,
7. Farmers rarely apply fertilizers fearing crop loss due to failure of rains,
8. Multi nutrient deficiencies also contribute towards the decline in yields in many groundnut growing areas.
9. Use of complex fertilizers lead to deficiencies of Calcium and Sulfur affecting the yields,
10. No irrigation facilities to protect the crop from soil moisture deficit during breaks in rainfall during monsoon season, and
11. Neglected weed, insect pests and disease control.
6. Important Features of Groundnut
:
The special features of groundnut crop are as under:
1. Groundnut does not appear to be sensitive to day light.
2. It grows best on soils with a slightly acid reaction (pH 6-6.4); alkaline soils are undesirable.
3. Groundnut possesses well developed tap root with mainly laterals as well as adventitious roots.
4. Root grows to a depth of 90-120 cm in loose soils. An extensive net of roots is induced mainly between depths of 10 to 25 cm. in the upper soil layer.
5. Self-pollination is a rule; natural crossing due to insects does not exceed 2% and is usually less.
6. Some varieties have seed which germinates immediately. Others have seed which germinates only after a period of dormancy.
7. Groundnut seed absorbs moisture very rapidly at temperatures of 12°C and emergence occurs after 10-12 days. Temperature of 15-20°C are more favourable than lower ones and will ensure a rapid and uniform emergence.
8. Flowering starts about 30-35 days after germination and continues for about 60 to 85 days.
9. Pegs that are formed more than 15 cm. above the soil surface usually fail to reach the ground.
10. Delayed sowing causes reduced yields.
11. Sensitive to moisture stress in the pre-flowering stage. However, water requirement is very low. Moisture stress causes the greatest yield reduction.
12. Aflatoxin poses a major problem in so far as the quality is concerned.
7. Classification
of Groundnut:
Cultivated groundnuts are allotetraploids (2n=40) in contrast to wild diploid species (2n=20). The cultivated groundnut (Arachis hypogaea L.) belongs to genus Arachis in subtribe Stylosanthinae of tribe Aeschynomenea of family Leguminosae. It is a self-pollinated, tropical annual legume. At locations where bee activity is high, some cross-pollination can occur.
Cultivated groundnut has two subspecies, hypogaea and fastigiata, which in turn have two botanical varieties (var. hypogaea and var. aequatoriana). Each of these botanical varieties has different plant, pod and seed characteristics. However, most of the commercially cultivated varieties belong to the hypogaea (common name/market type – Virginia or runner), fastigiata (Valencia), and vulgaris (Spanish) botanical variety groups.
The characteristics of these three botanical varieties are described below:
1. Variety Hypogaea:
No floral axes or branches on main stem; alternating pairs of vegetative and reproductive axes on branches (alternate branching); inflorescence simple; vegetative branches moderate to profuse; primary branches longer than main stem; growth habit spreading, intermediate, or erect; usually two seeds per pod; pod beak not very prominent; seed size medium (runner market type) to large (Virginia market type); testa color generally tan (red, white, purple, or variegated also exist); cured seed dormancy moderate; maturity medium to late.
2. Variety Fastigiata:
Floral axes on main stem; irregular pattern of vegetative and productive branches with reproductive branches predominating on branches (sequential branching); inflorescence usually simple; vegetative branches sparse; primary branches shorter than main stem; growth habit upright; two to four seeds per pod; pod beak absent, slight, or prominent; seed size small to medium; testa color tan, red, white, yellow, purple, or variegated; cured seed dormancy little.
3. Variety Vulgaris:
Floral axes on main stem; irregular pattern of vegetative and productive branches with reproductive branches predominating, primary branches shorter than main stem; growth habit upright; mostly two seeds per pod (three seeds are rare); beak may or may not be present; seed size small to medium; testa color tan, red, white, or purple; cured seed dormancy limited.
Classification According to Growth Habits:
The groundnut is an indeterminate type. Three main types of growth habits distinguished as bunch, semi-spreading and spreading are recognized in varietal classification of cultivated groundnut.
(i) The Erect or Bunch Type:
It includes Arachis hypogaea sub species fastigiata Waldron The main axis is long and erect and the primary branches are oblique to the main axis. It is short duration, early-maturing, high yielding, and almost free from dormancy.
(ii) The Spreading or Trailing Type:
It includes Arachis hypogaea sub-species procumbens Lal. The main axis is very short and erect, the primary branches spread horizontally along the ground and usually lie within 2 cm of the ground except at the tips which are somewhat ascending.
(iii) The Semi-Spreading:
This is an intermediate forms between the spreading and the bunch. The primary branches are prostrate upto a few internodes and then grow erect.
Commercial Classification of Groundnut:
(i) Coromandal Type:
It bears smaller pods, with thin husk. Oval shape smaller seeds.
(ii) Big Japan or Bombay Bold Type:
The pods and seeds of this type are bigger than coromandal type.
There are 4 types of groundnut plants based on the growth habit viz., Spanish (bunch), Virginia (bunch), Virginia (runner) and Valencia (bunch).
In the Spanish (bunch) group, the plants grow erect, possess light-green leaves, have round, plump non-dormant seeds, with light-rose testa, small pods, rarely have more than 2 seeds/pod, produce pods in clusters at the base of the plant, and popularly cultivated type.
In Virginia bunch and runner type, the branches crawl either partially or completely on the surface of the soil, produce large pods all along them, possess dark-green foliage, have oblong, dormant brownish seeds and late maturing but yield higher than bunch types.
In Valencia bunch type, very sparse branching habit dark green foliage seeds long or short seed coats purple, red, russet, or tan many pods may have 3-4 seeds are relatively unimportant.