SOIL SUITABILITY AND MANAGEMENT FOR RICE PRODUCTION

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SOIL SUITABILITY AND MANAGEMENT FOR RICE
PRODUCTION
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Abstract

• Rice is an aquatic or semi-aquatic plant, loves
  water for its growth, grown in all types of
  soils.
• However, soils with better water holding capacity
  like heavy neutral soils (clayey, clay loamy and
  loamy) are preferred compared to light textured
  soils.
• Rice is the typical crop which requires
  different soil environment which vary with other
  arable and submerged crops.
• Since the rice is under submergence, many of soil
  constraints are alleviated.
• Majority of rice grown in problem soils and its
  nature of cultivation makes suitable in these
  soils.
• Learning objectives
• To learn the best suitable soil environment
  for rice cultivation
• To learn the possibility of raising rice under
  problem soils and their suitable management
  strategies.

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Introduction

• The wide range of agro climatic conditions
  suggests an equally wide variety of soils
  suitability for rice crop.
• Rice is an aquatic plant, mainly grown in heavy
  neutral soils (clayey, clay loamy and loamy) and
  also grown in light textured soils.
• Rice is grown on loamy sands in Punjab to heavy
  Vertisols in Andhra Pradesh of India.
• Important group of soils for successful rice
  cultivation are alluvial soils, red soils,
  laterite or lateritic soils and black soils.
• Rice prefers slightly acidic pH, but, can grow
  in 5-8 pH range.
• Because of its better adaptation, it is grown
  under extreme soil conditions such as acid peaty
  soils of Kerala (pH 3) and highly alkaline soils
  (pH 10) of Punjab, Haryana and Uttar Pradesh in
  India.
• With the exception of coastal saline soils,
  occurs in high rainfall, saline or alkaline soils
  adversely affect growth and productivity of rice.

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• Long back, Moorman (1978) observed that the most
  important soil sub-orders on which rice is grown
  are
• Aquents,
• Aquepts,
• Orchepts,
• Tropepts,
• Aqualfs and
• Aquults (Table 1).

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Major rice growing soils
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Rice Growing Ecosystems

• Rice is mainly grown in irrigated lowland, rain
  fed lowland, upland and flood prone ecosystems,
  covers 55, 25, 13 and 7 of worlds rice area and
  accounts 76, 17, 4 and 3 production,
  respectively.
• By considering these, irrigated ecosystem is the
  major one and mainly grown under submerged
  puddled condition.

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Special features of submerged soil

• In any case, one important characteristic of rice
  soils is that they must remain submerged at least
  for some time during the growth period of the
  crop.
• The submergence leads to gradual depletion of
  oxygen and causes reduction of a number of ions
  such as nitrates, sulphates, iron, manganese etc.
  in the soil.
• The following chemical reactions happen in soil
  under submergence which affects rice plant
  growth.
• Under acid soils, pH increases and reduction of
  pH occurs in sodic soils .
• Reduction in redox potential .
• Reduction of nitrates to N2O or N2
  (denitrification)
• Reduction of sulphate to sulfide resulting in
  sulfide toxicity, reported from highly reduced
  soils in Japan.
• Reduction of Mn4 to Mn2 and Fe3 to Fe2
  resulting in Mn and Fe toxicity in rice.
• Increased availability of native soil P due to
  release of occluded P.

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Problem soils and management for rice

• Problem soil is one where one cant grow crop(s),
  but, has to adopt some specific and economical
  management practices to alleviate the soil
  related constraints to some extent and
  simultaneously choose crops best suited for the
  situation.
• Rice is the typical crop which requires different
  soil environment to grow.
• Since the rice is under submergence, the
  constraints of the soil are partly alleviated.
• Majority of rice grown in problematic in nature
  and its nature of cultivation makes suitable in
  these soils.
• Hence, major problem soils under which rice is
  grown are briefed with their management.
  (Cont)..

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Problem rice soils include

• Sodic soils
• Saline soils (includes inland and coastal saline
  soils)
• Saline-sodic soils
• Acid, red and lateritic soils
• Acid sulphate soils
• Peat soils

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Sodic soils

• Soils with sufficient amount of exchangeable
  sodium to interfere with the growth of crops and
  with less quantity of soluble salts are referred
  as sodic or alkali soils.
• There are about 65 million hectares of these
  soils in Asia, where rice is grown.
• Rice is the most suitable crop to be grown on
  these soils because submergence or flooding leads
  to lowering of soil pH and also helps in lowering
  of salt concentration.
• 
  

Rice in sodic soils
(Cont)..
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 Soil management for rice cultivation

• Application of gypsum is the handiest method to
  reclaim sodic soils when the pH is more than 10.
• Shallow rooted rice crop may require 12-15 t ha-1
  depending on the soil texture and sodic status.
• Application of organic amendments such as FYM,
  compost and green manure incorporation, releases
  abundant Co2, organic acids, lowers pH and
  releases
• Using resistant varieties, increased seedling
  hill-1, use of aged seedlings (30-40 days), split
  application of nitrogen, use of slow release
  nitrogenous fertilizers (sulphur coated urea,
  urea super granules), leaching in summer season
  and raising green manure crops are some of the
  crop management strategies for better production
  of rice in sodic soils.

Gypsum application in rice fields (Source
http//agritech.tnau.ac.in/agriculture/agri_reosur
cemgt_soil_soilcontraints.html
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Saline soils

• Saline soils are those soils contains sufficient
  soluble salts to interfere with crop growth.
• Saline soils remain flocculated and the hydraulic
  conductivity is more or equal to non saline
  soils.
• Soil pH is lt 8.5, electrical conductivity is gt
  4.0 dSm-1 at 25oC and Exchangeable sodium
  percentage is lt 15 Cmol(P) kg-1.
• These soils are with low physiologically
  available water due to high osmotic potential,
  poor aeration and toxic effect of sodium
  carbonate, sodium chloride and sodium sulphate.
• Though rice crop is considered as salt tolerant
  crop, no rice variety can withstand the adverse
  effect of high salinity throughout its life
  cycle. Due to submergence in most of rice soils,
  imparts tolerance to salinity.

Rice in saline soils (Source http//cssri.nic.in/
expertise.html)
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Soil management for rice cultivation

• Maintenance of submergence throughout life cycle
  of rice are suggested to better rice crop under
  saline soil conditions
• Selection of salt tolerant rice varieties based
  on salinity levels and water depths.
• Deep ploughing before submergence, heavy
  pre-sowing irrigation, high seed rate, closer
  spacing, green manuring with Dhaincha (Sesbania
  aculiata), use of organic amendments, placement
  of N fertilizer below soil surface, split
  application of N,

Green manure incorporated rice field (Sourcehttp
//agritech.tnau.ac.in/agriculture/agri_majorareas_
greenmanuring_intro.html)
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Saline-sodic soils

• These soils contain both high amount of
  exchangeable sodium and soluble salts to cause
  crop growth.
• The pH values are gt 8.5 (but vary with salts
  proportion and exchangeable sodium), Electrical
  conductivity of saturated extract is gt 4.0 dSm-1
  at 25oC and Exchangeable sodium percentage is gt
  15 Cmol(P) kg-1.
• These soils generally occur in low-lying areas
  with obstruction of drainage and occasional water
  logging.
• These soils not only cause due to high salt
  content but also, poor internal drainage due to
  the presence of hard pan.
  

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Soil management for rice cultivation

• Gypsum application (5-7.5 t ha-1) followed by
  leaching with good quality water is essential.
• Gypsum application along with green manure
  incorporation enhances better yield of rice.
• Leaching after transplanting and leaching under
  intermittent submergence decreases salinity and
  sodicity.
• Cultural management is similar to saline or sodic
  soils.
•  

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Acid, red and lateritic soils

• These soils are
• Shallow to medium deep,
• Low water retentively,
• Dominant of oxides of Fe and Al,
• Low CEC,
• Dominant of kaolinite and
• Illite clay minerals etc.
• Higher fixation of P and K, poor N status, crust
  formation on the surface, susceptibility to
  erosion due to light texture in nature and slope
  etc are some of the characteristics of these
  soils.

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Soil management for rice cultivation

• Artificial compaction to reduce to deep
  percolation is needed.
• To correct soil acidity, lime or other basic
  materials such as calcium silicate are to be
  applied.
• Addition of organic matter, FYM, compost, green
  leaf manures application to satisfy the organic
  matter requirement in soils.
• Due to high fixation of P, powdered rock
  phosphate, partial acidulated rock phosphate is
  better than water soluble P fertilizers.
• Bronzing of rice may occur in these soils can be
  corrected by lime application, drainage, foliar
  application of urea etc.

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Acid sulphate soils

• As the name indicates these soils are acid and
  have pH values below 3.5 ( Entisols) or 4.0
  (Inceptisols) in the upper 50 cm.
• There are about 5 million hectares under these
  soils in Asia.
• These soils are generally found in tidal swamp
  areas.
• Fe-toxicity is a major problem in acid sulfate
  soils.
• This can be managed by soil drainage, liming and
  by adding green manure or compost.
• However, amounts of liming material needed in
  some of these soils are too large and soil
  drainage is difficult to provide, because it is
  to be done on an area basis and an individual
  farmer cannot do it.

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Peat soils

• Peat soils have organic matter content of at
  least 65 in the upper 50 cm, are characterized
  by high water table and are found mostly
  low-lying coastal areas.
• Chemical toxicities including organics such as
  phenols etc. are common.
• Sterility of rice
• Copper deficiency or non-availability may be
  responsible for this sterility.
• Clearing of trees and vegetation and providing
  drainage can reclaim and improve these soils.

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Summary

• The major rice growing soil orders are Alfisols,
  Entisols, Inceptisols and Ultisols.
• The most important characteristic of rice soil is
  that submergence for at least a part of the
  growth period.
• Submergence leads to changes in soils pH, which
  tends to reach neutrality both in acid as well as
  sodic / calcareous soils. Submergence increases
  the availability of Fe, Mn and P but leads to
  loss of N by denitrification and reduced nitrogen
  use efficiency.
• Major problem soil under which rice is grown are
  sodic soils, saline soils (includes inland and
  coastal saline soils), saline-sodic soils, acid,
  red and lateritic soils, acid sulphate soils and
  peat soils.
• Application of gypsum is important for sodic
  soils and selection of tolerant varieties with
  organic amendments are important for better
  growth of rice under saline soils.
• Lime application play greater role to reclaim
  acid soils. Ground rock phospahete is better
  alternative to water soluble P fertilizers in
  acid sulphate soils.

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Assessment

• Rice is an aquatic or semi-aquatic plant prefers
  to grow under submergence (True/False)
• Rice grow well under light textured soils
  (True/False)
• Submergence of soils generally neutralizes the
  soil (True/False)
• Most suitable amendment to reclaim the sodic soil
  is gypsum (True/False)
• Green manures and manures application can improve
  the saline soils and makes suitable for rice
  cultivation (True/False)
• Gypsum application followed by leaching with good
  quality water makes the saline-sodic soils
  suitable for rice (True/False)

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References

• Biswas, C.R. and A.K. Bandyopathyay. 1987.
  Agronomy of rice in coastal saline soils a
  review. Journal of Indian Society of Coastal
  Agricultural Research, 5 15-23.
• Hand book of Agriculture, 2006. Indian Council of
  Agricultural Research, New Delhi.
• Gupta, R.K. and I.P. Abrol. 1990. Salt affected
  soils Their reclamation and management for crop
  production. Advances in Soil Science. 11
  223-288.
• Moorman, F.M. 1978. Morphology and classification
  of soils on which rice is grown. In Soils and
  rice. IRRI, Philippines.
• Rajendra Prasad, 1999. A text book of Rice
  Agronomy. Jain Brothers, New Delhi.

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