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  Soils And Climatic Requirements

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Ikisan - Soil & Climatic requirements

Introduction

  • The climate-soil culture complex causes considerable difference in growth yield and fruit quality among citrus producing areas in the world.

 
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Ikisan - Suitable soil for citrus cultivation

Soils

  • Citrus trees grow in almost any soil that is well-drained, sufficiently aerated and allows tap root to penetrate to the desired depth.
  • Planting of citrus trees in unsuitable soils and sites has often led to early decline and sometimes total failure of many orchards in Andhra Pradesh.
  • The decline of Batavian orange plantations in Palacol area, the reduction in area under cultivation of Vadlapudi orange in parts of Guntur, Krishna and Godavari districts and the extremely short life of Sathgudi plantations in Anantapur district, revealed that presence of a hard pan formed due to calcium carbonate concretions in the soil determines the depth of the active root system and age at which citrus decline starts.
  • Early decline (even before 6-7 years after planting) was found in soils where the hard pan occurred in the soil, within a depth of 30 cm.
  • In order to allow the tree to develop a sufficiently deep root system, care should be taken to select deep, well-drained and medium-loamy soils without any hard pan in the sub-soil within the root zone.
  • The hard pan restricts the root system and creates stagnant moisture conditions within the root zone for prolonged periods, causing root rot and early decline of trees.
  • In shallow soils, "die-back' of twigs and sparse foliage and low yields are common symptoms in sweet orange.
  • Decline of trees is generally associated with soils containing excess i.e. more than 10 % free lime.
  • Presence of lime does enhance growth of citrus plants for a few years but the problems of die-back begins when feeding roots come into contact with calcium carbonate pan.
  • Further, excess presence of free lime reduces the availability of phosphorus, iron, manganese and zinc and increases deficiencies/disorders associated with these elements.
  • Heavy soils with high clay content (more than 30%) will have inadequate drainage and insufficient aeration. Poor aeration of the soil reduces the absorption power of roots and may hasten the decline or trees.
  • Presence of a free water table within the reach of the root zone also represents a hazard.
  • In general, the roots of citrus tree do not get injured so long as the water table remains beneath 0.45m.
  • The main threat to the health of an orchard is a fluctuating water table.
  • A water table below 1.5 metres in all seasons is conducive for citrus.
  • Because of a comparatively shallow root system, acid lime performs well in high water table areas like that of Tenali.
  • Soil reaction (pH) has a marked influence on the availability of plant nutrients.
  • Citrus prefers soils with a pH range of 6 to 7.
  • However, by adopting suitable management practices, citrus crop is being raised successfully in soils with a pH between 5.5 to 8.5.
  • Soils with a pH of more than 8.5 are unsuitable for successful growth and productivity of citrus.
  • Citrus trees are extremely susceptible to salt injury to should never be planted in saline soils.
  • Further, in alkaline, saline and acid soils, citrus trees suffer from several nutritional disorders and root diseases, remain unthrifty and exhibit early die-back symptoms.
  • Inadequate drainage and salinity aggravate leaf mottling disorders.
  • In light textured soil, the electrical conductivity of 1:2 soil water suspension should not be more than 0.8 m mhos/cm during monsoon season.

 
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Ikisan - Suitable climate for citrus cultivation

Climate

  • Although citrus plants grow well in tropical and subtropical climates, the commercial yields of citrus orchards in tropical regions are commonly 50% or less than that of those obtained in sub-tropical regions.
  • In tropical areas, citrus fruit tend to bloom sporadically whereas in sub-tropical regions it tends to bloom profusely in the spring, after winter dormancy, resulting in only one major crop in a year.
  • This is because in sub-tropical regions the shoots are dormant during the winter and when spring comes and with it the change in temperature; a major portion of the shoots flower at one time.
  • In tropical regions on the other hand, dormancy is not natural but induced by creating moisture stress (with-holding water supply for 4-6 weeks) to synchronize the flowering of a major portion of the shoots.
  • This is a common practice followed in Peninsular India.
  • Production technology generated at various research centres in India during the last five decades has helped a great deal in the rapid development of commercial citri-culture in the country.
  • The agro-techniques developed for the sweet orage and acid lime at the Fruit Reasearch Station, Ananthrajupet (Kodur) made it possible to obtain exceptionally high yields in certain well managed citrus orchards in the state.
  • Citrus species make little or no shoot elongation at temperatures below 120C or above 450C.
  • For sweet orange and lime, temperatures between 280 - 320C are considered ideal for optimum growth and productivity.
  • In the arid and semi-arid areas of Andhra Pradesh, while high moisture stress often limits growth, more often than the temperature, high temperatures at the time of flowering result in a low fruit set in sweet oranges.
  • Further, hot winds tend to cause excessive evopo-transpirational losses and often result in fruit drop.
  • Citrus species do best in regions with an annual rainfall of 1250 to 1850 mm.
  • As much, in arid and semi-arid areas, an adequate irrigation water supply is required for maintaining desirable soil moisture conditions.
  • In the humid tropics, citrus fruit tend to be large, with thin and smooth rind, has high juice content as compared to those grown in arid and semi-arid regions.
  • However, high humidity or rains, after a prolonged dry spell often causes the fruit to spilt.
  • In the tropics, lack of cold temperature causes very low breakdown of chlorophyll and synthesis of carotinoids in the rind, so the fruit may be pale green or at best pale yellow at maturity.
  • Also, fruit tend to have lower total soluble solids and acid concertarions in the juice in the arid tropics.
  • However, acid lime produced in the tropics develop a quite attractive colour and is ideal for export.
  • The acid concentrations are equally high in tropical and sub-tropical regions.

 
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