In this essay we will discuss about:- 1. Origin and Distribution of Groundnut 2. Area and Production of Groundnut 3. Climate and Soils 4. Agroclimatic Zones 5. Groundnut Varieties 6. Tillage and Seasons 7. Seeds and Seeding 8. Nutrient Management 9. Cropping Systems 10. Water Management 11. Weed Management 12. Package of Practices 13. Aflatoxin Problem.
Contents:
- Origin and Distribution of Groundnut
- Area and Production of Groundnut
- Climate and Soils Suitable for Cultivating Groundnut
- Agroclimatic Zones of Groundnut
- Groundnut Varieties
- Tillage and Seasons of Groundnut
- Seeds and Seeding of Groundnut
- Nutrient Management for Groundnut
- Groundnut Based Cropping Systems
- Water Management for Groundnut
- Weed Management for Groundnut
- Package of Practices for Groundnut
- Aflatoxin Problem in Groundnut
1. Origin and Distribution of Groundnut:
Groundnut, king of vegetable oilseeds in India, occupies pre-eminent position in national edible oil economy. Also known as peanut, monkeynut or moong fali (Hindi), occupies the first place among oilseed crops grown in India. Botanical name Arachis hypogaea for groundnut is derived from Greek works Arachis meaning legume and hypogaea meaning below ground, referring to formation of pods in the soil.
There are two main schools of thoughts on the origin of groundnut, one supporting the view that it had originated in Africa and the other to South America. However, recent botanical surveys and archaeological excavations have indicated South America as the most likely centre of origin of groundnut.
It appears that Portuguese introduced the groundnut plant from Brazil into Africa. At the beginning of sixteenth century, groundnut was introduced into India by Jesuit Fathers who followed Vasco De Gama shortly after his first landing in India.
The spread of groundnut in some countries is striking, particularly in India and China. At present, groundnut is grown on a large scale in almost all the tropical and subtropical countries. Most important are India, China, USA, Nigeria, Senegal, Indonesia, Brazil and Argentina.
2. Area and Production of Groundnut:
On global basis (2006), groundnut is grown in around 22.25 M ha, spread over 85 countries, with an annual production of 47.75 M t and productivity 2.15 t ha-1. India ranks first both in the area (6.0 M ha) and production (7.0 M t) contributing to about 40 per cent of the area and 46 per cent of the world production. Major groundnut producing countries are China, India, Nigeria, USA, Indonesia, Sudan and Senegal.
During 1950-51, the area under groundnut cultivation was 4.5 M ha with a production of 3.4 M t. The area increased to 8.3 M ha and production to 7.5 M t. by 1990-91. The area under groundnut gradually decreased from 1994-95.
However, the production was nearly constant around 7.8 M t largely because of increase in productivity from 940 to 1080 kg ha-1 by 1997-98. Highest production of groundnut (8.98 M t) was during 1998-99, which declined to 4.1 M t during 2002-03 and to 4.9 during 2006-07 (Table 9.1).
Groundnut accounts for 28 per cent of the total area and 36 per cent of total oilseed production in the country. As per 2009-10 statistics, groundnut is cultivated in 5.48 M ha with a production of 5738.5 M t accounting to a productivity of 1007 kg ha-1. Largest area under groundnut is in Gujarat (1.82 M ha) followed by AP (1.30 M ha).
Production is highest (1.76 M t) in Gujarat followed by AP (1.01 M t). Among the major groundnut producing states, productivity is highest in Tamil Nadu (2113 kg ha-1) followed by WB (1969 kg ha-1).
3. Climate and Soils Suitable for Cultivating Groundnut:
Although, groundnut is predominantly a crop of the tropics, the approximate limits of present commercial production are between latitudes 40°N and 40°S and up to an altitude of 1065 m, where rainfall during the growing season exceeds 500 mm. From the productivity of groundnut in several countries, it is evident that semiarid and arid regions with 500-700 mm rainfall during crop period are ideal for groundnut production.
Rainfall:
The crop can be grown successfully in places receiving a minimum of 500 mm and a maximum of 1250 mm. Rainfall should be adequate during flowering and pegging stages. Ideal rainfall for successful groundnut crop would be 80-120 mm during summer to facilitate preparatory cultivation, 100-120 mm at sowing, 200 mm from flowering to peg penetration and about 200 mm from early pod development to pod maturity.
Variability in amount and distribution of rainfall is the most important factor limiting the productivity of rainfed groundnut, which constitutes around 90 per cent of the total area under the crop. Continuous rains leads to excessive vegetative growth resulting in poor pod yield.
Rains at harvest cause germination of kernels in non-dormant Spanish and Valencia cultivars besides problems in pod drying. Year to year variations in groundnut productivity are largely due to variation in rainfall distribution, especially during flowering and pegging stages of the crop.
Temperature:
Soil temperature less than 18°C delays emergence of seedlings. The embryo is killed above 54°C. Groundnut performs well in dry temperature range between 24° and 33°C but can survive up to 45°C. Ideal temperature for reproductive stage is between 24° and 27°C. Rate of pod growth will be maximum between 30° and 34°C.
Light:
Groundnut crop canopy responds to increased light intensity up to full sunlight. Groundnut is a day length insensitive plant. About 60 per cent solar radiation for 60 days after emergence appears to be critical. Low light intensity prior to flowering slowdown the vegetative growth and increase the plant height.
Flowering phase is most sensitive to reduced light intensities. Low light intensity at early flowering leads to flower abortion. Low light intensity at pegging reduces peg and pod number besides reduced pod weight. In the absence of soil moisture stress, clear days have greatest potential for optimum growth and development leading to high pod yield.
Soils:
Groundnut is grown on all types of soils such as sandy, sandy loam and heavy black soils. It is seen to thrive best on sandy loams. Heavy and stiff clay soils are not desirable as they tend to become hard during dry weather thereby interfering with peg penetration into the soil and also make the harvest extremely difficult. Most suitable soils for groundnut production are well drained light sandy loams with an ample supply of calcium and moderate organic matter.
Groundnut is one of the most acid tolerant crops with a critical pH range of 5 to 5.5. Ideal pH is 6.5 to 7.0. It is considered moderately sensitive to soil salinity. A salinity threshold (salinity at initial yield decline) of 3.2 dS m-1 has been reported. Groundnut is highly susceptible to waterlogging.
4. Agroclimatic Zones of Groundnut:
Groundnut growing areas in the country are divided into six zones:
Zone I (Northern Zone):
Uttar Pradesh, Punjab, Haryana, Bihar and northern Rajasthan (Jaipur, Ajmer, Bharatpur, Surai, Madhopur and Tonk).
Zone II (Western Zone):
Gujarat, southern Rajasthan (Chitorgarh, Udaipur and Jhawar).
Zone III (Central Zone):
Madhya Pradesh (excluding Mandsour and Ratlam) and Maharashtra (excluding Satra, Sangli, Solapur, Kolhapur, Osmanabad and Nandea).
Zone IV (Southeastern Zone):
Orissa and northern Andhra Pradesh (excluding Srikakulam, Vijayanagaram and Visakhapatnam).
Zone V (Peninsular Zone):
Karnataka, Andhra Pradesh (excluding the three districts of zone IV) and southern Maharashtra (Satara, Sangli, Solapur, Kolhapur, Osmanabad and Nanded).
Zone VI (Southern Zone):
Tamil Nadu.
5. Groundnut Varieties:
Varietal Improvement:
According to Seshadri (1962), there were four varieties under cultivation in India by 1960, all of which were introductions: Coramandal, Bold, Peanuts and Red Natal. They were marketed under different names in different parts of the country. The first two were spreading types and the latter two bunch types.
Groundnut varieties now under cultivation fall under three botanical groups: Spanish, Valencia and Virginia. All the cultivated varieties falls under three habit groups: bunch (Spanish/Valencia) semispreading (Virginia bunch) and spreading (Virginia runner).
In India, groundnut breeding was first taken up in the erstwhile composite states of Mysore (Hebbal), Madras (Palakuppam, South Arcot), Madhya Pradesh (Akola), Uttar Pradesh, (Kanpur), Mumbai (Karad and Kopergaon) and Punjab (Samrala). Based on introductions and selections from indigenous and exotic germplasm, a number of promising strains were developed.
Some of the varieties such as TMV 2, AK 12-24, Kopergaon 1, Punjab 1 etc developed during the period 1935-1950 are popular even today in several parts of the country. Subsequently in sixties, work carried out in Gujarat (Junagadh) resulted in the development of J 11(SB XI), a Spanish bunch type with a wider adaptability, resistance to collar-rot and aflatoxin which has been a serious constraint limiting exports of groundnut extractions. Together with TMV 2, J 11 has become more popular under a wide range of agroclimatic conditions.
The other significant achievements on the varietal front during sixties were the release of TMV series 6, 7 and 8 (Virginia bunch) from Tamil Nadu; S 206 and S 230 (Spanish bunch) from Karnataka; C 501 (Virginia) from Rajasthan. The productivity potentials of groundnut were further improved with release of 20 more high yielding varieties in seventies which include 9 of Spanish bunch (Tamil Nadu: TMV 9, POL 2, Co 2, Co 1, TMV 12; Karnataka: Dh.3-30; Haryana: MH 1; Madhya Pradesh: Jyoti; Gujarat: Gaug 1), 6 of Virginia bunch (Andhra Pradesh: Kadiri 3; Tamil Nadu: TMV 10 and TMV 11; Maharashtra: TG 1; Bihar: BG 1 and BG 2) and 1 of Valencia category (MH 2 from Hisar) and 4 of Virginia runner (Kadiri 71-1 of Andhra Pradesh, M 13 of Punjab, Chandra of Uttar Pradesh and GAUG 10 of Gujarat).
Notable achievement during this period was the development of early maturing bunch variety JL 24 (Phule Pragati) from an exotic accession, EC 94943. The early flowering and synchronous pod maturity character made it one of the most popular national varieties, especially where terminal soil moisture stress is common.
The establishment of the ICRISAT and the consequent availability of a wide range of germplasm collections provided unique opportunity to groundnut breeders to broaden their genetic base for the development of improved varieties. Under the AICORPO, since 1967 a number of Virginia bunch types were developed and released for commercial cultivation.
Despite the above developments the productivity levels of groundnut in the country are subjected to high degree of fluctuations owing to its high degree of interaction with environment together with a number of biotic and abiotic stresses. Extensive screening of germplasm resources has now resulted in the identification of a number of lines of potential value in the breeding programme.
Increased use of such germplasm accessions in the breeding programmes resulted in the development and release of a number of varieties possessing tolerance resistance to abiotic and biotic factors in the last decade.
The notable ones are: ICGS 11, ICGS 44. ICGV 86325, TAG 24 and DRG 12 (tolerant to BND), Girnar 1, ICG 44, ICGV (FDRS) 10. ICGV 86590 and CSMS 84-1 (multiple resistance to pests and disease and drought tolerance) and Tirupati 2 and Tirupati 3 (tolerant to Kalahasti Melady).
From 1936 to 2010, around 150 improved groundnut varieties were developed and released for various groundnut growing states or regions. Under good management these varieties gave pod yields around 5 t ha-1. Unlike in rainy-season (kharif) groundnut, there has been a remarkable increase in the area and production of winter rabi/summer groundnut in the country since 1970.
Breeding programmes have been stepped up only in recent years for developing early maturing (100 days), high-yielding varieties that are specifically adapted to the rabi/summer conditions. The varieties exclusively released for rabi/summer cultivation include Spanish bunch group, viz. RSHY 1, TAG 24, DRG 12, TG 26 and ICGS 1. The HPS groundnut holds enormous export potential. There are few varieties that possess bold kernels: Somnath, BAU 13, TKG 19A and B 95.
Recommended Varieties:
A large number of improved varieties have been released for cultivation under different agroclimatic conditions. Recommended varieties for different states in the country are given in Table 9.7.
6. Tillage and Seasons of Groundnut:
Tillage:
Land preparation for groundnut depends on the soil type and onset of monsoon for rainfed crop and on the previous crop grown for irrigated crop. Light red soils are usually ploughed twice with the summer rains followed by two to three harrowings. In Tamil Nadu, 4 to 6 ploughings are considered optimum. There is no agreement on the number of ploughings necessary for obtaining higher yields.
In general, it is observed that deep ploughing of light soil once or twice results in higher pod yield than repeated shallow ploughings for rainy season crop. Deep ploughing aids in higher rainwater storage in root zone to minimise the adverse effect of drought during the crop season.
In Maharashtra and Karnataka, medium deep soils are ploughed twice followed by several harrowings till the rains are received for seeding. In Andhra Pradesh, black soils are only harrowed several times without any ploughing.
Setline cultivation is practiced in Saurastra region of Gujarat. Pearlmillet and groundnut are grown in 90 cm wide rows. The rows are in the same position over years and ploughing is done only in the rows and harrowing only clears inter-row space. Organic manners, if any, and fertilisers are ploughed into the row before sowing. Due to higher infiltration of rainwater in the row, soil moisture will be available to the crop over a longer period.
Groundnut sowing is often delayed due to late rains leading to poor yield. Under such situations, it is advisable to prepare the land, taking advantage of summer rains. When once the land is prepared, groundnut sowings can be taken up with the earliest monsoon rain. If the land is not well prepared for sowing in time, the existing weed growth can be eliminated by non-selective herbicides such as Gramoxone and sowings can be taken up immediately.
In command areas and under well irrigation, land preparation for irrigated groundnut after kharif rice is a problem if the soils are relatively heavy textured. The land is frequently ploughed at high soil moisture content for sowing the groundnut in optimum time. This results in soil compaction leading poor crop stand and low yield. If the soil is not well prepared, soil bulk density beyond 1.6 g cm-3 limits the peg penetration.
Under such situations, it is desirable to give one light ploughing even at high soil moisture content such that the soil drying process will be hastened. When once the soil moisture content is brought down considerably, the field can be harrowed 3 to 4 times at 2 to 3 days interval for taking up groundnut sowing.
Seasons:
The crop growing season should be ideal for growth and development of crop for optimum yield. India has a unique distinction of growing groundnut in four major seasons: kharif (80% area), rabi (11% area), summer (5% area) and spring (4% area). Thus, kharif groundnut (June-July to October-November, depending upon the south-west monsoon) is the most important crop for the country.
Kharif:
Around 80 per cent of the area under groundnut is during kharif under rainfed conditions. Depending on the onset of monsoon, the season extends from April to August. In Pollachi area of Tamil Nadu, which gets the benefit of premonsoon showers, Spanish bunch type is sown in April.
In Ramanathapuram, and Tirunelveli areas, sowings are taken up in August-September due to late receipt of rains. In other areas of south India, sowings are done from June to August. Other parts of the country complete the sowings in June-July. Earlier the sowings in June, higher will be the yield.
Rabi:
Groundnut cropping during rabi is limited to areas where winter is not severe and temperatures do not glow below 15°C. Rabi groundnut crop is usually after kharif rice where irrigation water is inadequate for rabi rice. Sowing period extend from October to December. In general, second half of November is the ideal sowing time.
Summer:
Groundnut yields are higher during summer due to ideal climate and irrigation although the crop period. This crop is largely confined to south Indian states. Sowings commence during second fortnight of December and continue up to February first fortnight. Mid-Dec. to Mid-Jan is ideal for high yield.
7. Seeds and Seeding of Groundnut:
Quality seed is essential for establishing adequate plant population for efficient use of growth resources leading to economic pod yield.
Seeds:
Germination less than 85 per cent is not considered satisfactory. It is a practice among formers to set apart good quality pods for seed purpose. Selected pods are thoroughly cleaned, dried, packed preferably in gunny bags and stored in a well-ventilated place.
Groundnut pods for seed purpose are usually hand shelled about a week in advance of sowing. The viability of seed will be last if shelled long before seeding. Shellers are also used for shelling the pods to minimise the cost of groundnut production. After shelling, shrivelled and damaged seeds are rejected by hand picking. Seeds retained on 5 mm sieve (100 kernel weight above 27 g) germinates early and produce vigorous plants for high pod yield.
Seed treatment against seed and soil borne diseases is essential for stand establishment by preventing damage to seeds and seedlings emerging from soil. Seed treatment with Thiram (3 g kg-1), Bavistin (2 g kg-1) or Dithane M 45 (3 g kg-1) is effective for about 20 days from sowing.
Most of the chemicals used for seed treatment against fungal and bacterial diseases also affect Rhizobium, thus rendering the inoculation ineffective for a short time. When both seed treatment and inoculation are essential, seeds may be treated with fungicides and Rhizobium culture sprayed into seed rows and covered with soil. Granulated Rhizobium strain can also be sown with seed.
Optimum Time of Seeding:
A large number of trails have been conducted all through the groundnut growing areas for determining optimum time of sowing for kharif, rabi and summer groundnut. In spite of fixing an ideal dates for seeding kharif groundnut in different places, there is no scope for adhering to the recommended dates because of year to year variation in the onset of monsoon. Rabi and summer groundnut sowings largely depends on the harvest of proceeding crops in the intensive cropping systems.
In general, June seeding appears to the ideal for kharif groundnut, November for rabi and mid-December to mid-January for summer crop (Table 9.8).
Spacing and Seed Rate:
Inadequate crop stand is one of the major factors limiting the productivity of groundnut Optimum plant population depends on plant type (bunch or spreading), soil fertility, soil moisture and management practices. There is no agreement on optimum spacing and plant population for groundnut in India. The crop is seeded with spacing between 15 x 10 and 45 x 20 cm corresponding to plant densities of 7.0 and 1.1 lakh plant ha-1.
Often, significant variations in pod yield of groundnut are not observed due to differences in plant population, indicating plasticity. Higher plant population reduce the number of branches per plant while lower plant population increase the number of branches per plant. In groundnut, number of pods per plant is the major yield component determining the final pod yield. Number of pods per plant increase with increasing number of branches per plant.
As such, there is no significant variation in pod yield due to differences in plant population. In general, irrespective of initial plant population above 3.33 lakh plants ha-1, the final plant population at harvest tends to be around 3 lakh plants ha-1. As such, a spacing of 30 x 10 cm (3.3 lakh plants ha-1) appears to be the ideal for kharif bunch types under most situations.
A spacing of 22.5 x 10 cm is optimum during rabi and summer seasons. Under conditions of Africa, USA and Israel, the row spacing even for bunch type ranges from 50 to 75 cm with intra-row spacing between 10 and 20 cm. For spreading types the spacing vary between 75 x 20 and 100 x 20 cm.
Of the total operating cost of production, cost of seed alone is around 40 per cent. Seed rate recommended for groundnut (about 120 kg ha-1) in India is more than twice to that in Africa, USA, Israel etc. There is need to reexamine the seed rates recommended for different types of groundnut to bring down the production cost considerably.
Seed rate depends upon the test weight (100 kernel weight), row and intra-row spacing. Most common spacing recommended for bunch types is 30 x 10 cm. At this spacing, seed rate workout to about 120 kg ha-1 to obtain a plant population of 3.3 lakhs ha-1. In the case of spreading types, the most common spacing is 30 x 15 cm, requiring a seed rate of 100 kg ha-1 to obtain a plant population of 2.2 lakh plants ha-1. Bold seeded varieties require an additional seed rate of 20 kg ha-1.
In Andhra Pradesh, recommended seed rates for bunch types are 120 and 150 kg ha-1 during kharif and rabi respectively. Corresponding seed rates for semi spreading types are 150 and 180 kg ha-1. These seed rates appear to be relatively higher than the actual requirement under most situations. Recommended spacings (ICAR) in major groundnut growing states in India are given in Table 9.9.
A closer spacing of 22.5 x 10 cm is recommended to Spanish bunch under irrigation, especially in Andhra Pradesh. Gap filling, if necessary, should be completed taking advantage of the soil moisture at the time of sowing the seed within a week. If gap filling is done taking advantage of subsequent late rain, plants from the first sowing smother the later gap filled plants. As such, there may not be any yield advantage due to gap filling.
Determination of Seed Rate for a Given Plant Density:
Seed rate depends on row spacing, plant population, test weighty of seed and percentage germination. For experiments, it is desirable to increase the seed rate by around 20 per cent to ensure adequate stand establishment.
Given:
100 seed weight = 32 g
Plant population = 3 33 000 plants ha-1
100 per cent germination.
Find:
Seed rate ha-1 and 15 m-2 plot with eight 5 m rows?
Solution:
Seed rate per ha:
3 33 000 plants ha-1 = 33.3 seeds m-2
32 g per 100 seed = 0.32 g per seed
33.3 seeds m-2 x 0.32 g per seed = 10.65 g seed per m-2 or
10.65 g x 10000m2/1000 g kg-1 = 106.5 kg ha-1
Add 20 per cent to meet unforeseen losses due to birds, insects or diseases during germination.
106.5 kg ha-1 + 20% or 106.5 kg ha-1 x 1.20 = 127.8 kg ha-1
Seed per plot:
10 000 m2 requires 127.8 kg seed
1 m2 requires:
127.8 kg x 1000gkg-1/10000 m2 = 12.78 g m-2
A plot of 15 m2 will require 12.78 g m-2 x 15 m2 = 191.7 g
Seeds per row:
A plot of eight rows requires 191.7 g
Hence, one row requires:
191.7 g/8 rows = 23.96 g per row
If the germination percentage is 80 per cent, then the seed rate will be:
If 80 seeds out of 100 seeds germinate, required seeds for 100 plants will be:
100 x 100/80 = 125 seeds should be sown.
This means for each gram of seed, 1.25 will be the multiplying factor to compensate for germination loss.
Then the seed requirement would be:
125 kg ha-1 x 1.25 = 160 kg ha-1
192 g per plot x 1.25 = 240 g per plot.
24 g per row x 1.25 = 30 g per row.
Method and Depth of Seeding:
Mechanical or bullock drawn seed drills are used for sowing the groundnut seed. The other method is dropping the seed in plough furrow behind country plough. Hand dibbling is also adapted to a limited extent.
Groundnut is mostly sown under rainfed conditions with a bullock drawn seed drill in Andhra Pradesh, Karnataka and Maharashtra. The number of cultures for seed drill varies from 3 to 6 with 15 to 60 cm between cultures. One ha of land can be covered with a drill of 6 cutlers drawn by bullocks in 4 hrs.
Tractor drawn mechanical seed drills are also used if the area to be covered is large. Sowing with indigenous bullock drawn or mechanical seed drill is the best method of seeding for uniform stand establishment. Intercultivation and harvesting can also be easily carried out with implements resulting in considerable saving in production expenditure.
Common method of sowing in Tamil Nadu and adjoining areas of Karnataka and Andhra Pradesh is dropping the seed in furrows behind the country plough. It is often argued that in this method, the seeds are placed at uneven depths and often on the ridges of the furrows leading to uneven germination and poor stand establishment.
It appears that this method is more ideal when the soil moisture content is relatively low at sowing since the seed is dropped deeper in soil than that with drilling. There is no problem for using intercultivation implements since the row spacing can be maintained as in the case of drilling.
Groundnut seed can emerge even from around 20 cm depth at soil bulk densities more than 1.6 g cm-3. However, sowing deeper than 8.0 cm is not desirable. In light soils, the seeds are usually sown to a depth of 5-7 cm and in heavier soils to a depth of 4-5 cm. Depth of sowing should be less if the soil moisture content is higher than when it is relatively dry.
It is desirable to work a wooden plank after seeding to establish adequate soil-seed contact to ensure quicker and higher percentage of germination. A blade harrow along the line of sowing is more effective than working a wooden plank since the former operation can slightly compact the soil besides uprooting the emerging weeds, if any.
8. Nutrient Management for Groundnut:
For every 1.0 t of pods and 2.0 t of haulms about 63 N, 11 P2O5, 46 K2O, 27 CaO and 14 MgO kg ha-1 are removed by the groundnut crop. Of these, about 50 per cent nitrogen, 80 to 90 per cent phosphorous, potassium, calcium and magnesium are found in haulms.
On sandy loam soils, for the production of 100 kg pods 4.38 kg N, 0.92 kg P2O5, 3.12 kg K2O, 1.25 kg Mg and 4.0 g Zn are required. A balanced fertiliser programme with particular emphasis on P, K, Ca and Mg is essential for optimum pod yield.
Deficiency Symptoms:
Nitrogen deficiency is characterised by a general chlorosis of leaves, which become light yellow or nearly white in some cases. The stems become distinctly red besides poor nodulation. Lack of phosphorus leads to dark blue-green leaves with reduced size.
Characteristic symptom is the deep red or purple colouration of the stem in later stages, older leaves yellow and drop down. Potassium deficiency leads to stunted growth, with drying up of leaf margins. The stem gets a reddish colour at the tip of branches.
Calcium deficiency is characterised by development of localised pitted areas on lower surface of leaves. Later on, large necrotic spots are found on both the leaf surfaces, which give the leaf a bronze colour. The youngest foliage presents a distorted appearance. The basal stem cracks and dieback of the shoots occurs during the later stages.
Calcium deficiency leads to poor filling of pods (pops). Sulphur deficiency produces pale green colour in leaves. Magnesium deficiency leads to interveinal chlorosis, which starts, from leaf margins and advances towards midrib.
Iron deficiency produces stunted growth and characteristic chlorosis symptoms. Small and distorted terminal chlorotic leaflets with a few yellowish white spots indicate iron deficiency. Boron deficient leaves resemble calcium deficient leaves except that in the former necrotic areas are localised near leaf margins instead of being distributed over the entire leaf surface.
Nutrient Concentration:
The primary function of plant analysis is to diagnose problems or to monitor the nutrient status during crop growing season for timely correction of problems, if any. Concentrations of N, P, K, Cu, Mn and Zn in groundnut leaves, generally, decrease with increasing age. The concentration of Ca markedly increases with leaf age and Mg concentration tends to increase. Adequate concentration of different nutrients is given in Table 9.10.
9. Groundnut Based Cropping Systems:
At national level, nine major cropping systems have been identified. In Gujarat, besides sole crop of groundnut, pearlmillet, sorghum, cotton and pulses are the alternate crops. In south India, rice forms an alternative crop, especially during rabi/ summer. Under rainfed conditions, sorghum, pearlmillet, fingermillet and cotton are the alternate crops. In Maharashtra, sorghum and cotton are the alternate crops to groundnut.
Sequence Cropping:
In general, groundnut crop is rotated with cereals, commercial crops and oilseed crops. Yield of cereals following groundnut usually increased by around 25 per cent. Some of the promising crop sequences for major groundnut growing states are given in Table 9.12.
Intercropping:
Important cereal crops grown with groundnut are pearlmillet, sorghum and maize. Other long duration crops grown with groundnut as intercrops are pigeonpea, cotton and castor. Short duration intercrops with groundnut are sesame, sunflower, cowpea, greengram and blackgram Suggested intercropping system are given in Table 9.13.
10. Water Management for Groundnut:
Irrigated groundnut accounts for over 20 per cent of the total area under the crop in the country. Yields around 4.2 t ha-1 have been reported under irrigation in several situations.
Critical Stages for Irrigation:
Adequate available soil moisture is essential throughout the growth duration of the crop for normal growth and development. However, certain growth and developmental slates are more sensitive to water deficits than other stages leading to low pod yield of groundnut.
Studies on critical states for soil moisture stress indicated that peak flowering (45-60 DAS) is the most sensitive stage. Very early growth phase (up to 20 DAS) is least sensitive. Flowering, peg penetration and early pod development stages are the three moisture sensitive stages for pod yield. Several other studies indicated that the period from peak flowering to early pod development (50-75 DAS) is very sensitive to soil moisture stress.
Since flowering is almost a continuous process in groundnut from about 25 DAS to physiological maturity, there is overlap of flowering, pegging and pod development. As such, it is difficult to pinpoint the exact stage most sensitive to soil moisture stress. Therefore, it is reasonable to state that the period from peak flowering to early pod formation is the most critical phase for water deficits in groundnut.
Scheduling Irrigation:
On sandy loam soils, scheduling irrigations at 25 per cent DASM throughout the growth period results in high pod yield. Irrigating the crop at 25 per cent DASM from pegging to early pod development and at 50 per cent DASM at other stages appears to be ideal for high water use efficiency without significant reduction in pod yield. An IW/CPE ratio of 1.0 at moisture sensitive stages and 0.6 during other stages leads to high water use efficiency.
Keeping the total quantity of irrigation water applied constant, high frequency irrigation leads to high pod yield of groundnut on sandy loam soils. At several situations, 10-12 irrigations at 10 days interval resulted in highest pod yield. On sandy loam soils, seven irrigations: presowing irrigation, 25, 35,45, 55, 70 and 90 DAS appears to be ideal at times of water scarcity.
Based on several experimental results throughout the country, it is evident that a good crop of groundnut can be grown with 8 irrigations. There is no necessity for irrigation up to 25 DAS. After presowing irrigation, the next irrigation should be 25 DAS followed by four irrigations at 10 days interval.
Later two irrigations can be at 15 days interval. For bunch types, there is no need for any irrigation after 90 days of sowing. If the soil is very hard for harvesting the crop, a light irrigation may be necessary a day or two before pulling out the plants.
Depending on the soil type, evapotranspiration during the crop period and crop duration, water requirement of groundnut, on an average, ranges between 450 and 650 mm. The water utilisation efficiency (pod yield per unit of water evapotranspired) is 0.6 to 0.8 kg m-3. The crop is usually irrigated by check basin method. However, border-strip method is more suitable than other methods. Sprinkler irrigation is ideal for groundnut crop on sandy soils.
11. Weed Management for Groundnut:
Weed problem is severe in early stage of groundnut because of its slow growth. The competition is from both grasses and broad leaf weeds.
Important weed flora in the groundnut crop is indicated below:
Weed competition is critical up to 35 DAS. Yield losses to the extent of 70 per cent are not uncommon, especially under rainfed conditions. When once pegging beings (40 DAS), there should not be any disturbance to pegs through manual or mechanical weeding.
Cultural Management:
Most common methods of weed control in groundnut crop are hand weeding and harrowing. Line sowing with a row sparing around 30 cm facilitates working with different types of bullock drawn implements. Intercultivation usually starts around 10 days after emergence and continues up to 35 DAS at 7-10 days interval till pegging begins.
Weeds within the row are removed by hand weeding. Hand weeding is done twice, first around 20 DAS and the second about 35 DAS. There should not be any intercultivation or hand weeding from 40 DAS.
Use of Herbicides:
Cultural methods alone may not provide complete weed free environment for groundnut crop and repeated cultural practices may be costly or labour may not be available for timely weeding. Under such situations, herbicide use is the only option.
Any of the following herbicides are effective against many weed species:
PPI herbicides:
These herbicides can be PPI or PPS (prcplant surface). They will be effective only if rain or irrigation follow their application. Herbicides can be applied about 5 DAS (before crop emergence).
PRE herbicides:
A mixture of Oxadiazon and Dinoseb each at 1.7 kg ha-1 gives excellent control of weeds besides reducing stem rot in groundnut. Fluazfop (150-250 g) is a promising POST herbicide for controlling grasses, particularly Cynodon doctylon, 35-40 DAS.
12. Package of Practices for Groundnut:
Crop production practices discussed elaborately under different heads have been summerised as package of practices for groundnut.
Package for Rainfed and Irrigated Crops:
Tillage:
1. One or two deep ploughings followed by harrowing before sowing is adequate for a kharif rainfed crop on light red soils.
2. Medium black soils need one ploughing followed by two to three harrowings before sowing.
3. Deep plowing aids in storage of rainwater in crop root zone to minimise soil moisture stress during drought period.
Varieties Recommended for AP:
1. Anantha, Rohini, Bheema, TAG 24, TG 47, Greeshma, Prasuna, Abhaya, Apoorva, ICGV 86590, K 134, Tirupati 3, ICGV 86325, DRG 12, Kadiri 4, JCC 88, Kadiri 5, Kadiri 6, ICGS 76, Kalahasti, Narayani, TG 26,TMV 2.
2. Go for drought tolerant varieties under rainfed situation.
Seeds and Seeding:
1. Optimum sowing time is early-June for kharif groundnut, second half of November for rabi crop and mid-December to mid-January for summer crop.
2. Recommended seed rates during kharif are 120 kg ha-1 with a spacing of 30 x 10 cm for bunch types and 100 kg ha-1 with a spacing of 30 x 15 cm for semi spreading and spreading types.
3. Method of sowing is drilling or dropping the seed in plough furrows behind country plough.
4. For an irrigated/summer crop, recommended seed rates are higher by 20 kg for both the types with closer spacing (22.5 x 10 cm for bunch and 30 x 10 cm for semi spreading).
5. In AP, recommended seed rates are higher: 120 and 150 kg ha-1 for bunch and semi spreading respectively during kharif and 150 and 180 kg ha-1 for bunch and semi spreading respectively during rabi/summer.
6. Optimum seeding depth is 5-7 cm in light soils and 4-5 cm in heavier soils.
Fertiliser Schedule for AP:
1. 20 N + 40 P2 O5 + 60 K2 O kg ha-1 for rainfed crop and 30 N + 40 P2O5 + 60 K2 O kg ha-1 for rabi/summer irrigated crop.
2. Gypsum 500 kg ha-1 at flowering/peg formation.
3. Zn SO4 at 25 kg ha-1 for intensively cropped soils under irrigation.
4. For kharif rainfed crop, apply entire recommended dose of fertiliser at sowing by drilling/ placement.
5. For irrigated crop, apply entire dose of P and K and 20 N at sowing by drilling/placement. The remaining 10 N should be top-dressed by placement 30 DAS.
Water Management:
1. The period from peak flowering to early pod development (45-75 DAS) is most sensitive to soil moisture stress. In other words, flowering, peg penetration and early pod development are more sensitive to water deficit.
2. If irrigation water is not a limiting problem, a total of 8 irrigations (pre-sowing irrigation followed by an irrigation 25 DAS, 4 irrigations at 10 days interval and final two at 15 days interval) are adequate for optimum yield.
3. At times of deficit supplies, an irrigation 25 DAS followed by two at 15 days interval between 45 and 75 DAS appears to be the minimum requirement.
Weed Management:
1. Critical period of weed competition is up to 35 DAS.
2. Cost effective weed management under rainfed conditions is repeated intercultivations (harrowing) up to 35 DAS followed by a manual weeding.
3. A mixture of Oxadiazon and Dinoseb, each at 1.7 kg ha-1, gives excellent control of weeds under several situations.
4. Integrated weed management involving the above two appears most effective and economical, provided the crop is not subjected to prolonged drought/soil moisture stress during the crop period.
Contingency Plans for Drought Situation:
Rainfed groundnut crop is regularly exposed to the vagaries of monsoon resulting in poor productivity. Late onset of monsoon beyond mid-June and intermittent drought spells during July- August are quite common. The following implementable action plan is suggested to circumvent the impact of aberrant monsoon activity.
Contingency Plans for Management of Late Onset of Monsoon:
1. In the event of delay in the onset of monsoon beyond 15 July, it would be better to opt for sunflower crop up to mid-September.
2. If sowings are not possible even for sunflower up to mid-September, it would be ideal to opt for a castor crop up to the end of September.
3. Beyond September, short duration legumes and cereals including greengram, blackgram, soybean, cowpea, sorghum, pearlmiliet etc. can be cultivated for reasonably good economic returns (crop substitution).
4. Groundnut and pigeonpea/sunflower/castor/pulse crops as intercrops, to a large extent, enables partial risk coverage to drought situations.
Contingency Plan for Mid-Season Drought:
1. As in the case of delayed onset of monsoon, intercropping to a large extent enables partial risk coverage to mid-season drought.
2. Effective weed management is a pre requisite under drought situations. Integrated weed management strategies, involving repeated inter-cultivation, need to be followed in anticipation of mid-season drought.
3. Harvesting excess run off water, at times of runoff, in micro ponds and its reuse to provide a minimum of one life saving irrigation for stress management and yield improvement.
4. Due to drought, if plant stand is reduced to around 50 per cent of the initial, it would be advantageous to sow sunflower/castor/soybean as intercrops for every 4 to 6 rows of groundnut after receipt of rains in September without destroying the standing groundnut crop.
5. If the pant stand is reduced to less than 25 per cent of the initial stand due mid-season drought or other abnormalities, it would be advantageous to go for resowing with short duration crops like sesame, soybean, greengram, blackgram, horsegram, cowpea etc., in early October.
13. Aflatoxin Problem in Groundnut:
In most groundnut growing areas of the world, the pod mycoflora of groundnut is dominated by Aspergillus, Fusarium and Penicillium. Several species belonging to these general are reported to produce mycotoxins in many agricultural commodities. One such fungus commonly found in groundnut is Aspergillus flavus, which produce aflatoxins when growing in groundnut seed and groundnut products.
Aflatoxins are toxic and carcinogenic to a wide range of animal species and to humans. Their presence in groundnut products presents a serious health problem. Of the 18 known aflatoxins, B1 is the most important in toxicity followed by G1 and M1.
Aflatoxin Contamination:
Insects may damage shells and seeds during crop period, field drying and storage. Such damage can facilitate invasion of seed by A.flavus. Delayed harvest, slow and irregular field drying can also result in seed invasion.
Now it is established that groundnut without such damage can be invaded by A.flavus and contaminated with aflatoxin in the field before harvest. Drought stress is associated with seed invasion by A. flavus before harvest. Over maturity and low seed moisture content in the field appears to increase the incidence.
Significant fresh invasion by A. flavus and aflatoxin contamination can also take place during postharvest drying period. At harvest, groundnut seeds contain about 40 per cent moisture and are susceptible to fungal invasion until their moisture content drops to around 8 per cent.
The length of the time seeds remain at critical moisture probably influence the amount of aflatoxin produced. In years of frequent rains at harvest, a high percentage of seeds are invaded by A. flavus. In areas where rains continue after harvest, field drying is a problem leading to serious aflatoxin contamination. Groundnut is safe from A. flavus when its moisture content is around 8 per cent during storage. However, if the produce becomes accidentally wetted by rain, it leads to rapid invasion by flavus.
Gravity of Aflatoxin Problem:
In recent years, Indian groundnut export is dwindling despite the fact of world’s largest groundnut producing country. The Republic of China is the largest supplier of HPS groundnut which holds 28 per cent share of international trade of groundnut pods followed by USA (22%), Argentina (21 %), Vietnam (8%) and South Africa (2.5%). The share of India is only 2 per cent.
During the last 5 years, the world trade has increased by about 30 per cent. However, the Indian trade registered a declining trend due to poor quality standards. The European countries are skeptical about reliability and continuity of supply as well as the quality from the aflatoxin point of view. As a result, India confront with almost ban like situation for the entry of its groundnut produce in the European market.
The physical and chemical standards for groundnut export fixed by the importing countries are stringent. In view of the very stringent aflatoxin regulation (2 ppb B1) imposed by the European Union, there is need to reorganise the whole gamut of operations to meet the new challenges.
The need of the hour is to develop a firm strategy to save India from the European union market and target the UK, Germany and Netherlands, the largest groundnut import market in the world. There is needed for blending scientific knowledge into production, processing and export system.
The Indian groundnut export can be increased if appropriate technology including varietal selection, soil moisture management, timely harvest and drying around 8 per cent moisture arc adopted. This may bring down the groundnut aflatoxin content to permissible level and match with the international standards.