Soils Well - drained, light - textured, loose, friable sandy - loam or sandy clay loam soils, well - supplied with calcium and a moderate amount of organic matter are ideal for groundnut cultivation. Good soil drainage facilitates adequate exchange of air to meet nitrogen, carbon dioxide and oxygen requirement of the crop (soil aeration). Lack of proper drainage adversely affects root respiration,resulting in inhibition of root growth,ultimately affecting the plant growth and development through retarded metabolic functions. In the absence of adequate oxygen in the root zone, beneficial soil bacteria, especially the nitrogen - fixers become ineffective and uptake of nitrogen by roots is hampered. Since staining of groundnut pods reduces their marketable quality, light - coloured soils, which do not normally contain materials that stain pods, are preferred. Seed germination and seedling emergence are favoured in loose, friable and sandy - loam soils. The pegs can penetrate the soil easily and pods can be harvested from such soils with minimum losses of comparatively clean produce because the soil does not adhere excessively to the freshly dug pods. Adequate supply of calcium mineral in the soil is very essential for the production of groundnut pods with sound and mature kernels. A moderate amount of organic matter (about 2%) has been reported to increase the water and nutrient - supplying capacity of the soil, especially the micro - nutrients like zinc, copper, iron, manganese, boron and molybdenum to meet the plant needs without staining the pods. In addition to soil fertility, soil - texture is vitally important aspect of groundnut production. Heavy and fine - textured soils with stiff clay minerals (montmorillonite) cause serious difficulties in groundnut harvesting owing to a higher pod - retention. Such soils are therefore avoided for cultivation of rainfed groundnut because they tend to become hard and stiff during prolonged dry spells between two rains, thus severely interfering with peg penetration into the soil and their further development. Where as groundnut crop can be grown successfully on heavy - textured soils with a greater risk of pod loss at harvest. Fields with shallow top soil, poorly drained areas and those subject to excessive erosion should be totally avoided. Where groundnuts must be grown on heavier - textured soils, runner and pish varieties of groundnut are more suitable than the Virginia types. High groundnut yields are obtained on soils with moderate acidic reaction (soil pH 6.0 to 6.4), alkaline soils being undesirable. Yellowing of groundnut leaves and blackening of parts of pods occurred when the soil pH was 7.5 - 8.5. Soils having pH less than 5.0 are also not suitable for groundnut cultivation. The ill - drained acidic, alkaline and saline soils should be essentially avoided for groundnut production. There will be a reduction in groundnut yield due to soil salinity and to reduction in pod size and the number of pods per plant. Application of gypsum alleviates the detrimental effects of soil salinity by improving leaching of salts below the root zone. The normal yield of groundnut can be obtained on fairly heavy soils with good tilth and favourable moisture regime. A pod yield of 50.93 q / ha of the irrigated groundnut grown on clayey soil (more than 50% clay), with favourable pH, exchangeable sodium percentage (ESP) and calcium carbohydrate equivalent, as against 10.00 q / ha obtained on the similar soils, with less favourable pH, ESP and calcium carbonate equivalent. The soils which are most suitable for growing groundnuts should have good drainage, electrical conductivity less than 4.0 m.mhos / cm (saturation extract of soil), high clay content, ESP less than 5, pH lower than 8 and calcium carbonate equivalent less than 4%. Similarly, the electrical conductivity of irrigation water should be less than 4 m.mhos / cm and residual sodium carbonate (RSC) less than 2 m.eq / litre. The decrease in the pod yield when using saline water exceeding 4 m.mhos / cm was attributed to poor germination, retarded seedling growth, poor nodulation and reduction in size and number of pods per plant. In tropical and subtropical conditions of India, groundnut is extensively grown in light - textured red sandy, red loamy, alluvial and coastal - alluvial soils as well as on mixed black and red and medium black soils. A majority of both the bunch (more than 50%) and runner (about 80%) groundnuts in Southern India is grown on sandy, sandy - loam and mixed red and black soils. Groundnut is also grown on medium black soils, deep alluvial loams and on sandy and gravelly soils of poor fertility with low organic matter content.

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Climate As climate is the single major limiting factor in the crop production in the mater of the time of sowing, scheduling of irrigation, timing of fertilizer application, using of pesticides, etc. Groundnut is grown throughout the tropics and its cultivation is extended to the subtropical countries lying between 45o north and 35o south and up to an altitude of 1000 meters. The crop can be grown successfully in places receiving a minimum rainfall of 1250 mm. The rainfall should be distributed well during the flowering and pegging of the crop. The total amount of rainfall required for pre-sowing operations (preparatory cultivation) is 100 mm; for sowing it is 150mm; and for flowering and pod development an evenly distributed rainfall of 400-500 mm is required. The groundnut crop however, can not stand frost for long and severe drought or water stagnation. Climatic conditions such as temperature and rainfall significantly influence the groundnut production. Potential, warm and moist conditions are very favourable than cool and wet climate, which results in slow germination and seedling emergence, increasing the risk of seed rot and seedling diseases. Adequate rainfall well distributed during the growing season, especially during fruiting, is essential for maximum yield and quality of groundnut. Also a minimum 100 - day optimum temperature growing season is necessary for successful groundnut crop production.

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