Introduction Groundnut, scientifically known as Arachis hypogaea L., belongs to the family Fabaceae (Leguminosae). The genus name Arachis is derived from a Greek word referring to legumes, while hypogaea indicates its “below-ground” fruiting habit. It is commonly known by several names including peanut, earthnut, monkey-nut, and manila nut. Importance Groundnut is a highly concentrated food source, as its kernel contains about 45% oil and roughly 20% protein of high biological value. It is also rich in vitamins such as thiamine, riboflavin, niacin, and vitamin E. The extracted oil is mainly used as a vegetable oil, while the residual oilcake serves as an excellent organic manure and animal feed. The cake contains around 7–8% nitrogen, 1.5% phosphorus, and 1.5% potassium, making groundnut an effective crop for improving soil fertility within cropping systems. Centre of Origin and Distribution The highest diversity of Arachis species occurs in South America—mainly Argentina, Bolivia, and Brazil. Bolivia is regarded as the primary centre of origin. From Brazil, the crop was introduced to Africa by the Portuguese in the sixteenth century and later reached India via African trade routes. Globally, groundnut is widely grown in tropical and subtropical regions. Groundnut Growing Zones in India In India, it is cultivated across states such as Gujarat, Andhra Pradesh, Karnataka, and Odisha. Groundnut cultivation in India can be grouped into zones such as the northern zone (including parts of Punjab), western zone (Gujarat and Madhya Pradesh), central zone (Madhya Pradesh and Maharashtra), south-eastern zone (Odisha and north coastal Andhra Pradesh), peninsular zone (Telangana and Rayalaseema), and southern zone (Tamil Nadu and Karnataka plateau). Within Odisha, both kharif and rabi seasons contribute to total production, with rabi accounting for a larger share. Districts like Jajpur, Bargarh, Ganjam, Malkangiri, and Balasore are major producers. Classification Cultivated groundnut varieties are classified mainly into Virginia, Spanish, and Valencia groups based on their branching pattern. Virginia types exhibit an alternate branching system where the main axis remains non-reproductive, and vegetative and reproductive branches appear alternately along the laterals. Spanish and Valencia groups show sequential branching, where reproductive branches arise continuously along cotyledonary and lateral branches. These types often bear reproductive branches even on the main stem, and most tertiary or higher-order branches bear pods. Spanish types may produce some tertiary vegetative branches, whereas Valencia types generally do not. Botany Groundnut is an annual herb with a well-developed taproot that may reach a depth of over a metre, though most roots remain within 5–35 cm of the soil. The root spread typically extends 12–14 cm from the base. Plants may show a spreading (prostrate) or erect (bunch) growth habit. Leaves consist of two pairs of leaflets, and the subspecies hypogaea tends to have darker foliage than fastigata. Flower, Peg, Pod, and Kernel: Groundnut follows an indeterminate growth pattern, with flowering beginning about three to four weeks after emergence. Flowering continues for several weeks, depending on the growth type. The plant produces yellow flowers in leaf axils on reproductive branches, and pollination is largely self-fertilized. Fertilization is usually completed within a few hours of pollination.After fertilization, the ovary elongates into a peg or gynophore, which grows downward soilwards due to positive geotropism. Once the peg penetrates roughly 7 cm into the soil, it develops into a pod. Pods are indehiscent and may contain one to five seeds. The outer covering is a pericarp, and the thin skin of the seed is called the testa. The edible seed is the kernel, which accounts for 55–75% of pod weight. Climate and Soil Requirements Groundnut thrives in tropical and subtropical climates between latitudes of 40°N and 40°S, and is cultivated up to about 1,065 m above mean sea level. The optimum temperature range for growth and flowering is 25–30°C. Temperatures below 13°C limit growth, while temperatures above 35°C reduce pollen viability. Soil temperatures below 18°C affect seed germination.The crop requires bright sunlight; low light during flowering and pegging increases flower abortion and reduces pod formation. It is relatively drought-tolerant once established, though evenly distributed rainfall of 500–1,000 mm is ideal. Soil Requirements Well-drained, loose, friable sandy loam soils rich in calcium and moderate organic matter are best suited for groundnut cultivation. Sandy and loamy soils are preferred over clayey soils, as hard clay restricts peg penetration. The ideal soil pH ranges from 6.0 to 6.5. Poorly drained soils and soils with high acidity or alkalinity should be avoided, as acidic soils may produce empty pods without kernels. Production Technology Land Preparation For uniform germination and high yield, a weed-free, well-pulverized seedbed is essential. This is achieved through summer ploughing followed by two ploughings at the onset of monsoon. Acidic soils should be amended with lime or paper-mill sludge about two weeks before sowing. In termite-prone areas, chlorpyrifos granules may be applied at the final land preparation stage. Raised beds or ridge-furrow systems are recommended in high-rainfall regions. The Broad Bed and Furrow (BBF) method developed by ICRISAT is beneficial, especially in rabi season. Sowing About 90% of the crop is sown in the kharif season. Timely sowing with the onset of monsoon ensures better growth and higher yields. Early sowing helps utilize rainfall efficiently, reduces weed pressure, and allows planting of a second crop in sequence. In Odisha, sowing begins from mid-June to early July. Spacing and Seed Rate Erect and semi-erect types are typically spaced at 30 × 10 cm, whereas spreading types require 30 × 15 cm. Since Spanish bunch types form most pods close to the taproot, a spacing of 20–30 cm between rows and 10 cm within rows is ideal. Seed rate is around 125 kg kernels per hectare for bunch types and about 75 kg per hectare for spreading types. Sowing depth should be around 5 cm. Seed Selection and Dormancy Management Seeds harvested in rabi lose viability faster than those from kharif, and shade drying of rabi produce helps retain viability. Vivipary (pre-harvest sprouting) is a challenge, and foliar sprays of maleic hydrazide at 60 and 75 days after sowing induce dormancy and prevent sprouting by up to 80%. Seed Treatment Seeds are treated with fungicides such as carboxin + thiram, captan, carbendazim, or thiram to prevent seed-borne diseases. For biological nitrogen fixation, seeds should be inoculated with appropriate Rhizobium strains at sowing. Varieties Numerous varieties are grown depending on habit, duration, oil content, and resistance characteristics. Popular ones include AK 12-24, Smruti, Phule Pragati, ICGS-44, TAG-24, TG-3, TMV-2, Kadiri-3, Devi, Kadiri-6, Kadiri-9, Dharani, among others. These differ in duration (around 95–110 days), shelling percentage, oil content, and tolerance to drought or bud necrosis. Fertilizer Management A general recommendation is 20–40–40–20 kg N–P₂O₅–K₂O–S per hectare along with farmyard manure. Entire fertilizer dose is applied in furrows before planting, ensuring seeds do not contact fertilizer directly. Application of phosphorus through single superphosphate helps meet sulfur needs. If SSP is not used, gypsum should be applied at about 250 kg per hectare around 20–25 days after sowing to supply calcium, which is essential for pod formation as calcium movement through the gynophore is limited. Micronutrient Management Acidic soils limit availability of boron and molybdenum. Boron deficiency leads to pollen abortion, hollow-heart formation, and poor gynophore development. Soil application of borax or foliar sprays correct deficiencies. Molybdenum deficiency reduces nitrogen fixation and can be corrected by treating seeds with ammonium molybdate. Zinc deficiency, common in sandy soils, is corrected through soil application of zinc sulfate or foliar sprays. Interculture and Weed Management The first weeding is done about two to three weeks after sowing, followed by earthing up to help peg penetration in erect varieties. Soil should not be disturbed after flowering starts. Pre-emergence herbicides such as pendimethalin or metolachlor may be used, and post-emergence herbicides like quizalofop or fluazifop control grassy weeds. Growth Regulation Excess vegetative growth at flowering can be managed through application of NAA (20 ppm), which enhances pod setting and improves test weight and yield. Water Management Drainage is essential during kharif to remove excess water. During rabi, irrigation should be applied every 10–15 days depending on soil moisture. Flowering, pegging, and pod formation are the critical moisture stages. Mild early water stress may synchronize flowering. Plant Protection Major Pests: White grubs and termites can be controlled through seed treatment, soil application, and drenching with chlorpyrifos or other recommended insecticides. Hairy caterpillars are managed through light traps and insecticidal sprays. Leaf caterpillars, thrips, and leaf miners are controlled using pheromone traps, biological agents, or specific insecticides. Major Diseases: Tikka disease caused by Cercospora species is managed through resistant varieties, seed treatment, and periodic fungicide sprays. Collar rot caused by Aspergillus niger results in basal stem rot and can be controlled through seed treatment, soil drenching, and regulated irrigation. Bud necrosis, a virus disease transmitted by thrips, is managed through vector control and tolerant varieties like Kadiri-3 and AK-12-24. Post-Harvest Management Harvesting, Curing, and Storage: Timely harvesting is crucial for high pod and oil yields. Signs of maturity include yellowing leaves, shedding of older leaves, appropriate testa colour, and darkening inside the shell. After lifting, plants are kept in small stacks for a few days for curing before pods are separated. Pods should be dried to about 5% moisture to avoid aflatoxin contamination. Under good management, bunch types yield about 1.5–2.0 t/ha, while spreading types may yield 2–3 t/ha. Stored pods should be kept in well-ventilated storage rooms, preferably on wooden platforms. Cropping Systems: Groundnut is widely grown in mixed cropping systems with crops like pigeon pea, rice, cotton, sunflower, sesame, and pearl millet. It also fits well in crop sequences such as groundnut–wheat, groundnut–maize, groundnut–mustard, groundnut–onion, and groundnut–sunflower. Aflatoxin Management: Aflatoxin contamination is caused by toxigenic strains of Aspergillus flavus, Aspergillus nomius, and Aspergillus parasiticus. These toxins pose serious health hazards in humans and animals. To prevent pre-harvest contamination, crop rotation should be followed, drought stress avoided during pod development, and mechanical injury to pods minimized. Post-harvest management includes careful handling of pods during harvest, eliminating damaged or immature pods, rapid drying, avoiding re-wetting, maintaining cool storage conditions, and preventing insect infestations inside storage structures. Related resources ICAR - Indian Institute of Groundnut Research Groundnut export market outlook - APEDA Package of practices of groundnut for different states State-wise groundnut varieties notified under Seed Act Integrated Pest Management package for groundnut Organic production of groundnut