• The season for the cultivation of groundnut crop varies considerably in India on account of variations in soil and climatic conditions in different states. In India, groundnut is cultivated in 3 seasons viz., Kharif (monsoon or rainy season), Rabi (winter season) and Summer.
• In Tamil Nadu, groundnut is grown in five seasons viz., Adipattam (June-July), Karthikaipattam (Oct-Nov), Margazhipattam (Dec-Jan), Masipattam (Feb-March) and Chithiraipattam (April-May).

• About 90% of the groundnut in India is sown in the kharif season under rainfed conditions.
• In Pollachi area of Tamil Nadu which gets the benefit of pre-monsoon showers, Spanish bunch varieties are sown in the first week of April. In Ramanathapuram and Tirunelveli districts, which receive monsoon rains very late, sowings are taken up as late as September. Between these two extremes, there are central and coastal districts where sowing is done from June to August. July-August sowings are most common.

• Groundnut is raised in rabi season on a limited scale in areas where winter is not severe and night temperatures do not go below 15^oC. This crop is usually raised in rice fallow situation to utilize the residual moisture after the harvest of rice. Where irrigation facility is available, 2 or 3 irrigations are given in the later stages of the crop. The rabi crops are sown from September to December. The growth and yield of September sown crop is poor even though it may receive 2 or 3 irrigation.
• Low temperatures delay the germination of seed and cause setback in the plant growth and reduce flower production. If the crop is sown in November or later with an early maturing cultivar, the growth and yield can be better. Rabi groundnut is raised in coastal regions, river deltas of Cauvery and in other irrigated areas in parts of Tamil Nadu.

• Groundnut needs good sunshine and high temperature to produce more pods. Summer, is therefore the ideal season for groundnut cultivation wherever irrigation facilities are available and soil is suitable. In parts of Tamil Nadu (Pollachi, Theni and Tenkasi regions) the crop is raised under irrigation in summer.
• Sowing is taken up from the second fortnight of December to March. But the crops sown in December and first fortnight of January give higher yield than those sown later. The summer crop gives more than thrice the yield of the kharif crop due to favourable climate conditions for the growth and development of the crop and low incidence of pests and diseases.
• High temperature coupled with adequate light intensity leads to more enzyme production in the leaf, which facilitates greater photosynthetic activity. The average total dry matter produced per plant in bunch variety at harvest is 25.7 g in summer crop as compared with only 14.8 g per plant in kharif crop.
  

• Groundnut seed with its high oil content is a good substrate for the development of pathogens. There are several seed and soil-borne diseases of groundnut which cause considerable damage to the seeds and seedlings emerging from soil. The pods have to be shelled only few days before sowing and the seeds be treated with fungicides.
• Seed treatment with any one of these fungicides is effective in protecting the seedlings against seed and soil-borne diseases resulting in higher plant stand.
  

carbendazim @ 2 g per kg ;

captan @ 4 g per kg of seed;

thiram @ 4 g per kg of seed;

mancozeb @ 4 g per kg of seed.

• Seed treatment with fungicides has to be done using a seed treatment drum or by placing the required quantity of fungicides and seed in a pot and rotating the pot, mixing the fungicide and seed so that the surface of each seed gets a complete coating of the fungicide. This will reduce pre-emergence rots and post germination mortality of seedlings.
• Inoculation of seed with efficient strains of nitrogen-fixing bacteria is necessary for areas where groundnut is not generally grown. Seed inoculation with 3 packets (600g) of TNAU 14 Rhizobium culture per ha is recommended. This can be treated with seeds using rice kanji as binder.
• The effect of seed treatment with fungicides lasts only 20 - 30 days from sowing and most of the chemicals used for seed treatment to prevent fungal diseases also kill the inoculating rhizobia, thus rendering artificial inoculation ineffective.
• The ability of antagonistic microorganisms as seed inoculants has been well proved against pathogens and they have the capacity to multiply in the rhizosphere region.
• These bio-control agents are also compatible with the nitrogen fixing bacterium, Rhizobium. Hence, the bio-control agents like Trichoderma viride (4 g/kg of seed) or Pseudomonas fluorescens (10 g/kg of seed) can be used for seed treatment as they are more advantageous than chemical seed treatment.

• Good quality seed of improved varieties suitable for the area is one of the most important factors for increasing productivity. Good seed is essential for establishing the required plant population, good development and yield. Purity, good viability, uniformity of seed size, colour, weight and freedom from seed-borne diseases are the chief characteristics of good seed. This can be achieved by the use of certified seeds.
• Purity of seeds is essential because mixed seeds do not ensure a uniform crop stand and lowers the market value of the product. Germination, stand of the crop and ultimate yields depend on the viability of the seed.
• Bunch types (Spanish and Valencia) have non-dormant seeds whereas semi-spreading (Virginia bunch) and spreading (Virginia runner) have dormant seeds. The non-dormant seeds germinate immediately after maturity. The dormant seeds usually require a resting period of 60 to 75 days before maximum germination can be obtained.
• Dormancy can be broken by exposing the seed to ethrel or by storing seeds along with ripening bananas for 3 to 4 days in air tight containers.
• The seed germination is 90 to 95 % in bunch types and 85 to 90 % in spreading types. Germination less than 85% is not considered satisfactory though minimum germination percentage of 70 is prescribed as seed standards for certification of labeled seed.
• Wherever the hand shelling of groundnut pods is not possible due to scarcity of labourers, groundnut decorticators (both hand operated and power operated) can be utilized for shelling the pods for seed purpose.

• In this equipment, shelling is carried out by rubbing action of the rocking assembly. Sieves can be placed based on pod size and variety. The dimension of the equipment is 115 x 50 x 132 cm (length, breadth and height respectively). Using this unit, 100 kg of pods can be shelled in an hour with a working cost of Rs. 15.50 per hour. Three persons are required to operate the unit. The cost of equipment is Rs. 2000/-

Power operated groundnut decorticator

• In this method shelling is carried out by rubbing action of the oscillating sector. Sieves can be placed based on pod size and variety. The dimension of the equipment is 133 x 35 x 135 cm. With the help of this equipment, 400 kg of pods can be shelled in an hour by one person. The cost of operation comes around Rs.15.00 per hour and the unit needs 1 HP electric motor for its operation. The cost of the equipment is Rs.15,000/-.

• Seed rate is the important criteria for obtaining optimum plant population in the field to achieve good yield. The seed rate should be determined so that in normal circumstances of normal rates of establishment, a full ground cover is achieved when the crop ceases vegetative growth.
• Seed rate depends upon the average size of seed expressed as natural test weight (100 kernel weight), inter- and intra- row spacing adopted.
  

*JL 24, Co 2, VRI 2, TMV 10 and Co3

• It will be better to use the seed rate based on the germination percentage of the seed aiming to achieve the optimum plant stand of 33 plants/m2.
  

• The spacing to be adopted depends on the size of the mature plants and how well they cover the ground. The changes in intra-row spacing have less effect on yields than changing in the spacing between the rows.
• Pods mature slowly on crowded plants than on widely spaced plants. Close planting suppresses the formation of late flowers so that the pods from adjacent plants are formed closure to the base of the plant, therefore, mature more evenly.
• In Tamil Nadu the recommended spacing for groundnut varieties is 30x10 cm.
  

• The three methods of sowing are

seed drill (bullock drawn or power drawn);

sowing behind the country plough and

hand dibbling.

	Groundnut can be sown under rainfed conditions using the seed drill. Tractor drawn TNAU improved seed drill is available for this purpose. But because of high initial cost and absence of facilities for repairing in villages this equipment has not become widely popular.

• In this type of seed drills, spacing between the rows, the distance between seeds in a row and depth of placement of seed can be regulated.

Tractor drawn TNAU improved seed drill

• This equipment can be mounted to tractor drawn cultivator, which is commercially available. This implement is suitable for sowing large areas in less time before the moisture is depleted in the dry tracts especially for rainfed conditions.
• This mounted implement, having a dimension of 235 x 113 x 115 cm requires 35 HP tractor for its operation. It weights 425 kg. It covers an area of 4 hectares per day with an operating cost of Rs.300/ha. The cost of implement is Rs.9,500/-
.
• The common method of sowing in Tamil Nadu is to drop the seed behind the country plough. The area covered by this method is less (0.30 ha). In this method, it is inconvenient to work bullock drawn inter-cultivation implements between the rows as uniform spacing is not maintained between the rows. It is also difficult to regulate the depth of sowing and usually the stand of the crop is not uniform.
• Dibbling the seed with hand is practiced mostly in irrigated areas. This is a very tedious, time consuming and expensive method of sowing. The seed rows are opened by tyne hoes and the seeds are dibbled in rows.

Depth of Sowing

• The depth of sowing of the seed influences germination and emergence through soil temperature and availability of moisture.
• In light soils, seeds are sown to a depth of 5-7 cm and in heavier soils to a depth of 4.5 cm. The depth of sowing should be less when the soil contains plenty of moisture than when it is moderately dry.
• Too shallow sowing limits germination as the upper layers of the soil dry out before radical emerges and suspend germination.
• Slight compaction of the soil over the seed is necessary to have good contact of the seed with soil and to ensure quicker germination and this can be achieved by drawing a beam or a blade-harrow across the line of sowing.

• The technique can be well used for rainfed situation as well as for taking up gap filling operation to achieve optimum population in the field. This new seed management technique has been developed to separate the dead seeds from the seed lot before sowing for the maintenance of plant population. The various steps involved in the technique are given below.
• The seed graded using 18/64" round perforated sieve may be hardened by soaking in 50% of volume solution of calcium chloride (5 g/lit of water) for 6 hours.
• Thenspread the seeds over the moist gunny bags and cover with the moist gunny for 20-24 hours.
• After 20-24 hours of covering, the kernels with visible expression of radicle emergence (just sprouted) are to be separated and dried under shade.
• The process has to be repeated for 2-3 times at 2 hours interval and all the viable seeds which expressed radical emergence are to be further separated and dried under shade.
• The viable seeds thus separated should be dried under shade immediately and can be used for immediate sowing.
• The seeds can also be stored for 7-10 days by drying to original moisture content after separation (when such viable seeds are used for sowing, the field emergence will be about 95% and the final field population can be maintained more than 90% with the resultant increased yield of about 15%). This technique involves three stages namely absorption, separation of dead seeds and pre-emergence sowing of viable seeds.

• One of the critical factors limiting the groundnut yield is low plant population. Optimum plant population depends upon plant type (bunch or runner), soil fertility, available soil moisture and other inputs during the crop period.
• For Spanish-bunch types following a most common spacing of 30x10 cm and a seed rate of 125 - 140 kg/ha, the optimum plant population will be 3,30,000/ha.

To maintain the required plant population in the field the following points are to be considered.

• use Certified seeds
• For Spanish bunch varieties, use the seed materials within 3 months after harvest since it looses viability thereafter.
• Hand shelling of pods is preferable for better germination. In case of scarcity and high cost of labour, use hand decorticator or power decorticator.
• Use kernels within 7 days after shelling. In the case power decorticated kernels, there are more chances of damage to the embryo. Hence, power decorticated kernels should be used as early as possible.
• Treat the seeds with fungicides/bio-fungicides to protect against seed and soil- borne diseases.
• Treat the seeds with bio-fertilizers, which help the plant to mitigate the moisture stress.
• Ensure uniform depth of sowing to obtain uniform field emergence.
• Avoid bird damage in the field by scaring birds.
• Ensure optimum moisture availability at the time of emergence.
• Fill the gaps within 10 days after sowing.
• For rainfed sowing and for gap filing, use the seeds treated with calcium chloride to ensure higher field emergence to maintain optimum plant stand.
• Wherever the incidence of rootgrub, millipede and termite is noticed, soil application of granular insecticide at the time of sowing is to be done.
• Care should be taken to level the field properly to avoid water stagnation at the time of sowing.

• Raise one row of cowpea for every 5 rows of groundnut wherever red hairy caterpillar is endemic to minimise plant protection.
• Raise intercrops like redgram, blackgram, sunflower, sesame or other pulses.
• Cumbu can be raised as intercrop.
• Groundnut + sesame or groundnut + blackgram in the ratio of 4:1 or groundnut + cowpea at 6:1 ratio and groundnut + sunflower at 6:2 ratio may be raised.

• Spreading of seven micron thickness black polyethylene film as mulch to irrigated groundnut along with preplant incorporation of fluchloralin @ 1.0 kg ai/ha increase the groundnut productivity under flat bed system

Benefits

• Early and enhanced germination of seeds (within 5 days)
• Early crop vigour and flowering (17 DAS)
• Uniform and basal setting of flowers
• Higher pod setting ratio ( 20 - 22 %)
• 100 per cent weed control
• Increase in soil temperature and humidity
• Enhanced soil microbial activity
• Early harvest (7-10days); enhanced pod yield (40 - 60% over control)