For growth and prosperity

For growth and prosperity

Thursday, 19 May 2011

Soil types - Remedy for problematic soils - Salt/Salinity Stress

Banana performs extremely well on organically rich, well drained and sandy clay loam soils with pH ranging from 6.0 to 7.5. 

In the black cotton soil farmer must put river bed sandy soil, organic manure and decomposed press mud at the time of land preparation to maintain pH, porosity and nutrition. 

Soil Fertility
 Poorly drained, saline and nutritionally deficient soils are not suitable for banana.

Various types of problematic soils and the remedial measures suggested to reduce its toxicity before venturing into Banana cultivation:

1.            Acidic soil and its remedies: ( ‘Amila Nilam’ in Tamil)         
  • Acidity due to Lower Ph because of low Calcium (Ca). 
  • pH range < 6.5  is Acidic. 
  • Apply recommended dose of Calcium 10 days before applying any basal fertilizers then plough well to properly mix the Ca in the soil and irrigate. 
  • Cultivation of Banana is not generally recommended without taking soil remedial measures recommended for acidity.

2.            Alkaline soil and its remedies: ( ‘Kalar Nilam’ in Tamil)                           
·        Alkalinity due to higher Ph because of Sodium (Na).
·        Soil pH > 8 to 8.9 is Alkaline.
·        E.C < 4
·        E.S.P < 10% (For sodic soils > 15%)
·        Growth of sensitive deep rooted crops will be moderately affected.
·        Apply liberal Qty. of FYM, raise Green Manure crops and plough them back into soil to increase O.C thereby increasing the drainage capacity of the soil.
·     Basal application of 300 Kgs of Gypsum per Acre for every crop.  Apply more depending upon the alkalinity of the soil.
·        Use only Fertilizers like DAP, Zinc Sulphate (Zn So4), Ammonium Sulphate       (Am So4), Potassium Sulphate (K2 So4 ), Etc.,
·      Cultivation of Banana is not generally recommended without taking soil remedial measures recommended for alkalinity.

3.            Sodic soil and its remedies:
·        Presence of Sodium (Na) > 15 in Alkaline soil.
·        Soil pH > 9
·        E.C < 4
·        E.S.P > 15% (For Alkaline soils < 10%)
·        Sodium Carbonate in the Soil reacts with salts and Fertilizers and the end
               products get deposited as white patches above the soil.
·        Because of higher pH, nutrients in the soil are less.
·        Since the soil subsurface is harder, plant roots can’t able to penetrate it.

Sodium effect on soil structure: When wet, a sodic soil tends to seal, its permeability is dramatically reduced, and thus water infiltration capacity is reduced as well. When dry, a sodic soil becomes hard has the tendency to crack. This may result in damages to roots.

Remedy for Sodic Soil:
·        Raise Daincha or Sunhemp and plough it back into soil (incorporate).
·    Cultivate Sun Flower Crop every year. It was proved that the Sun Flower plant absorbs Na from the soil. After harvest, the total plant with dried leaves should be heaped and burned outside your field.(Readers comments are welcome!).
·        Apply Sugar mill waste 5 Tons.
·        Use only Fertilizers like DAP, Zn So4, Am So4, K2 So4 Etc.
·     Apply liberal Qty. of M.N nutrients especially Zn. (Zn So4 @ 40Kgs per Hect. as basal is necessary.
·        25% more N as Basal is necessary.
·        Raise Saline resistant varieties (Such as Trichy 1, Co 43 in Paddy)
·      For Paddy, transplant only matured plantlings of 35 to 40 days age. Plant 3 to 5 saplings per Kuthu.
·    Sodic condition can be rectified using Chemicals such as Gypsum, Sulphur or Pairates.
·       Cultivation of Banana is not generally recommended without taking soil remedial measures recommended for ‘Sodicity’.

Role of Gypsum (Ca So4)  in the reclamation of Sodic Soil:
·      Regular application of Gypsum (Ca So4) @ 200 Kgs per Acre will give good yields because of it’s S and Ca contents.
·        Contents of Gypsum: S 18% +  Ca 23%  +   P2 O5  5%)
·        It neutralizes the harmful Na in the soil and reduces the E.S.P.
For Sodic soil reclamation :
1) Deep plough the field twice especially by Disc plough. It breaks open the hard soil pan lies in the subsurface and brings out the Na rich soil to the surface.
2) Evenly spread Gypsum (Ca So4) 2 Tons – leading in good quality water (leaching) – cage wheel plough ‘Tholiyadippu’  - maintain Water level at 6’’ and wait for 2 days. - Ca So4 in Gypsum reacts with Na   ( Sodium Bicarbonate ) in the soil and becomes Na So4 – Drain out the frothy Na So4 solution from the field. – Irrigate immediately - cage wheel plough ‘Tholiyadippu’ 2nd time – Drain out the frothy Na So4 solution from the field.
3) Raise Daincha and incorporate in to the soil.
4) After that raise ‘Horse Gram’ ( “Kanam” in Tamil) and don’t take seeds in the first year – allow the seeds to drop and the plant to wither – after the rains i.e. in the next season seeds will germinate – allow it to grow - take seeds and plough/incorporate the plant back into soil.
         4.            Saline soil and its remedies: ( ‘Uvar Nilam’ in Tamil)                    
A saline soil is defined as having a high concentration of soluble salts, high enough to affect plant growth. Salt concentration in a soil is measured in terms of its electrical conductivity. In general, soils having an ECe of 4 dS/m or more is defined as ‘saline’.
Normal Ph range, but with more E.C, because of Sulphates and Chlorates of Ca, Mg, Na and K.
Soil with high soluble salts, hence E.C > 4
Density of the cell sap in the root system is lower than the density of the salts in the soil resulting in reverse osmosis. (i.e) water / cell sap will ooze out of the cell wall and into the soil.

Symptoms of Salinity Stress in banana
Salinity can affect plant growth in several ways, directly and indirectly:
Direct soil salinity damages 
                    i.            Decreased water uptake :
High salts concentration results in high osmotic potential of the soil solution, so the plant has to use more energy to absorb water. Under extreme salinity conditions, plants may be unable to absorb water and will wilt, even when the surrounding soil is saturated.  
                  ii.            Ion-specific toxicity :
When a plant absorbs water containing ions of harmful salts (e.g. Sodium, Chloride, excess of Boron etc.), visual symptoms might appear, such as stunted plant growth, small leaves, marginal necrosis of  leaves or fruit distortions.

Indirect soil salinity damages 
                    i.            Interference with uptake of essential nutrients:
An imbalance in the salts content may result in a competition between elements. This condition is called "antagonism", i.e. an excess of one ion limits the uptake of another ion. For example, excess of chloride reduces the uptake of nitrate, excess of phosphorus reduces the uptake of manganese, and excess of potassium limits the uptake of calcium. 
                  ii.            Sodium effect on soil structure:
In saline soils, sodium replaces calcium and magnesium, which are adsorbed to the surface of clay particles in the soil. Thus, aggregation of soil particles is reduced, and the soil will tend to disperse.

Factors affecting soil salinity: 

Several factors affect the amount and composition of salts in soils:

1.    Irrigation water quality – If the irrigation water is also saline, the high level of dissolved salts in the irrigation water will slowly accumulate over the years in the otherwise normal soil and ultimately turning it in to saline. Therefore, various parameters, such as source water EC and its minerals content should be tested. 
 2.   Fertilizers applied - The type and amount of fertilizers applied to soil, affect its salinity. Some fertilizers contain high levels of potentially harmful salts, such as potassium chloride or ammonium sulphate. Overuse and misuse of fertilizers leads to salinity buildup, and should be avoided.
 3.  Irrigation regimen and type of irrigation system - Higher the irrigation water quantity lesser will be the soil salinity. If the irrigation water quantity is less in saline soil the concentration of salts in the soil solution is increased when the soil dries.
Since salts move with the dissolved water, the salts accumulate in specific profiles (Soil depths) according to the irrigation regimen and the type of irrigation used. For instance, when irrigating using sprinklers, water and salts move deeper, according to the soil's infiltration capacity and the water quantity, until they stop at a certain depth. 
4.  Field's characteristics and agricultural history - A poorly drained soil might reach salinity level that is harmful to the plants and to the whole crop. A soil that was not flushed after a previous growing cycle might contain high level of accumulated salts.
Remedial measures:
    • Cultivate Saline (Uvar in Tamil) tolerant specific varieties of Paddy, Ragi, Cotton, Sugar cane and Chilies.
    • Apply liberal Qty. of FYM, raise Green Manure crops and plough them back into soil to increase O.C thereby increasing the drainage capacity of the soil.
    •  Level the field evenly - Irrigate Soft water ( free from Bicarbonates) copiously – maintain water level – then drain out the water completely -  the unwanted salts dissolves in the water and flows out. 
    •  Provide adequate channels to let in rainwater and water from the irrigation tank. Salts will be washed off during heavy rains. Drain out the salt dissolved water from the field. We can reduce the salt content of the soil by increasing the drainage capacity of the field.
    • Cultivation of Banana is not generally recommended without taking soil remedial measures recommended for ‘Salinity’
    A.Vishnu Sankar


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