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Showing posts with label Soil Science. Show all posts
Showing posts with label Soil Science. Show all posts

Soil pH and Buffer pH |Cation Exchange Capacity (CEC) | Soil Colloids

 Soil pH and Buffer pH 

 

Soil pH This is a measure of the soil acidity or alkalinity and is sometimes called the soil "water" pH. This is because it is a measure of the pH of the soil solution, which is considered the active pH that affects plant growth. 

Soil pH is the foundation of essentially all soil chemistry and nutrient reaction and should be the first consideration when evaluating a soil test. The total range of the pH scale is from 0 to 14. Values below the mid-point (pH 7.0) are acidic and those above pH 7.0 are alkaline. A soil pH of 7.0 is considered to be neutral. 

Most plants perform best in a soil that is slightly acid to neutral (pH 6.0 to 7.0). Some plants like blueberries require the soil to be more acid (pH 4.5 to 5.5), and others, like alfalfa will tolerate a slightly alkaline soil (pH 7.0-7.5). 

The soil pH scale is logarithmic, meaning that each whole number is a factor of 10 larger or smaller than the ones next to it. For example if a soil has a pH of 6.5 and this pH is lowered to pH 5.5, the acid content of that soil is increased 10-fold. If the pH is lowered further to pH 4.5, the acid content becomes 100 times greater than at pH 6.5. The logarithmic nature of the pH scale means that small changes in a soil pH can have large effects on nutrient availability and plant growth. 

Buffer pH (BpH): 

This is a value that is generated in the laboratory, it is not an existing feature of the soil. Laboratories perform this test in order to develop lime recommendations, and it actually has no other practical value.  

In basic terms, the BpH is the resulting sample pH after the laboratory has added a liming material. In this test, the laboratory adds a chemical mixture called a buffering solution. This solution functions like extremely fast-acting lime. Each soil sample receives the same amount of buffering solution; therefore the resulting pH is different for each sample. To determine a lime recommendation, the laboratory looks at the difference between the original soil pH and the ending pH after the buffering solution has reacted with the soil. If the difference between the two pH measurements is large, it means that the soil pH is easily changed, and a low rate of lime will suffice. If the soil pH changes only a little after the buffering solution has reacted, it means that the soil pH is difficult to change and a larger lime addition is needed to reach the desired pH for the crop.  

The reasons that a soil may require differing amounts of lime to change the soil pH relates to the soil CEC and the "reserve" acidity that is contained by the soil. Soil acidity is controlled by the amount of hydrogen (H+) and aluminum (Al+++) that is either contained in, or generated by the soil and soil components. Soils with a high CEC have a greater capacity to contain or generate these sources of acidity. Therefore, at a given soil pH, a soil with a higher CEC (thus a lower buffer pH) will normally require more lime to reach a given target pH than a soil with a lower CEC. 

Soil Colloids  

During physical and chemical weathering processes in which rocks, minerals, and organic matter decompose to form soil, some extremely small particles are formed. Colloidal-sized particles are so minuscule that they do not settle out when in suspension. These particles generally possess a negative charge, which allows them to attract positively charged ions known as cations. Much like a magnet, in which opposite poles attract one another, soil colloids attract and retain many plant nutrients in an exchangeable form. This ability, known as cation exchange capacity, enables a soil to attract and retain positively charged nutrients (cations) such as potassium (K+), ammonium (NH4+), hydrogen (H+), calcium (Ca++), and magnesium (Mg++). Also, because similar charges repel one another, some of the soluble negatively charged ions (anions), such as nitrate (NO3-) and sulfate (SO4=), are not bonded to soil colloids and are more easily leached than their positively charged counterparts.  

Organic colloids contribute a relatively large number of negative charges per unit weight compared with the various types of clay colloids. The magnitude of the soil's electrical charge contributed by colloids is an important component of a soil's ability to retain cationic nutrients in a form available to plants.  

Cation Exchange Capacity  

The ability of a soil to retain cations (positively charged ions) in a form that is available to plants is known as cation exchange capacity (CEC). A soil's CEC depends on the amount and kind(s) of colloid(s) present. Although type of clay is important, in general, the more clay or organic matter present, the higher the CEC.  

The CEC of a soil might be compared to the size of a fuel tank on a gasoline engine. The larger the fuel tank, the longer the engine can operate and the more work it can do before a refill is necessary. For soils, the larger the CEC, the more nutrients the soil can supply. Although CEC is only one component of soil fertility, all other factors being equal, the higher the CEC, the higher the potential yield of that soil before nutrients must be replenished with fertilizers or manures.  

When a soil is tested for CEC, the results are expressed in milliequivalents per 100 grams (meq/100 g) of air-dried soil. For practical purposes, the relative numerical size of the CEC is more important than trying to understand the technical meaning of the units. In general, soils in the southern United States, where physical and chemical weathering have been more intense, have lower CEC's (1-3 meq/100 g) than soils in the northern United States, where higher CEC's are common (15-25 meq/100 g) because weathering has not been as intense. Soils in warmer climates also tend to have lower organic matter levels, and thus lower CEC's than their northern counterparts.  

Soils high in clay content, and especially those high in organic matter, tend to have higher CEC's than those low in clay and organic matter. The CEC of soils in Maryland generally ranges from 1-2 meq/100 g for coarse-textured Coastal Plain 

soils to as high as 12-15 meq/100 g for certain Piedmont and Mountain soils. The CEC of most medium-textured soils of the Piedmont region ranges about 8-12 meq/100 g.  

There are many practical differences between soils having widely different CEC's. It has already been mentioned that the inherent fertility (exchangeable nutrient content) of soils varies in direct relationship to the magnitude of the CEC. Another important CEC-related property is soil buffering capacity, that is, the resistance of a soil to changes in pH. The higher the CEC, the more resistance soil has to changes in pH. The CEC and buffering capacity are directly related to the amount of liming material required to produce a desired change in pH. Higher CEC soils require more lime than those with low CEC's to achieve the same pH change. 

If CEC is analogous to the fuel tank on an engine, soil pH is analogous to the fuel gauge. The gauges on both a large and a small tank might read three fourths full; but, obviously, the larger tank will contain more fuel than the smaller tank. If a soil test indicates that two soils, one with a low CEC and the other with a high CEC, have the same low pH, indicating that they both need lime, the one with the higher CEC will require more liming material to bring about the desired pH change than will the one with the lower CEC. The reason for this difference is that there will be more exchangeable acidity (hydrogen and aluminum) to neutralize in the high CEC soil than in the lower CEC soil. Thus, a soil high in clay or organic matter will require more liming material to reduce soil acidity (and raise the pH) than a low organic matter sandy soil will.  

Nutrient Deficiency Symptoms in Plants - IBPS AFO Study Material

 Nutrient Deficiency Symptoms in Plants


Nitrogen

  • General yellowing of lower leaves
  • Inverted V shaped Yellowing in cereals
  • Buttoning of cauliflower
  • Proteolysis in cells
  • Red leaf of cotton (also due to Mg toxicity)
Phosphorus
  • Sickle leaf disease
  • Purple  leaf disease
  • Anthocyanin pigmentation
Potassium
  • Marginal necrosis
  • Marginal Chlorosis of Grapes
  • Potato blotchy
  • Accumulation of Diamine putrescine
  • Dying back of tips
Calcium
  • Blossom end rot of Tomato (BER)
  • Bitter pit of apple
  • Tip hooking
  • Cavity spot of Carrot
  • Internal browning of Lettuce
  • Blackheart of Celery
  • Milk fever in cattle
Magnesium
  • Grass tetany of cattle
  • Bronzing of citrus
  • Sand drown of tobacco
  • Red leaf or reddening of Cotton (toxicity)
  • Inter- veinal chlorosis in lower leaves
  • Sulfur
  • Yellowing in upper leaves.
  • Tea Yellow
Boron
  • Internal necrosis of Mango , Aonla
  • Internal cork of Apple, Tomato
  • Browning / Hollow stem of Cauliflower
  • Cracked stem of celery, Lucerne
  • Lucerne Yellow / Alfalfa yellow
  • Heart rot of Sugarbeet , Marigold
  • Hard fruit of Citrus
  • Die back of Apple
  • Water core of Turnip
  • Brown heart of Wheat, Turnip
  • Sterility in Wheat
  • Top Sickness of Tobacco
  • Canker of Sugarbeet
  • Drought spot of Apple
  • Hen- Chicken disease of Grape
  • Crown chocking of Coconut
  • Fruit cracking of Tomato, Pomegranate
  • Snakeheads in Walnuts
Zinc
  • Khaira Disease of Rice
  • White bud of Maize
  • Mottle leaf of Citrus
  • Little leaf of Citrus
  • Frenching of Citrus
  • Little leaf of Cotton
  • Rosette Disease
  • Little leaf of Mango, Litchi
  • Fern Leaf of Potato
  • Leaf bronzing of Litchi
Silicone
  • Freckle disease in Sugarcane
Manganese
  • Grey specks of Oat
  • Speckled yellow of Sugarbeet
  • Pahaia Blight of Sugarcane
  • Frenching of Tung Tree
  • Crinkled leaf of Cotton (Toxicity)
  • Marshy Spot of Pea
Molybdenum
  • Whiptail of Cauliflower
  • Scald of Legumes
  • Yellow spot of Citrus
  • Khaira of Citrus
  • Downward cupping of radish
Iron
  • Interveinal chlorosis of young leaves
  • Leaf blanching of Sugarbeet
  • Bronzing of Rice (Toxicity)
  • Green neck of Citrus
  • Silver green leaf of Tomato
  • Lime- induced Chlorosis
Copper
  • Reclamation Disease
  • Stem melanosis of Wheat
  • Exanthema / Gumming
  • Dieback of Citrus
  • Wither tip of Apple
  • Rough bark of Apple

Chlorine
  • Brown centre of Potato
  • Susceptibility of Fusarium rot
  • Gray spot of Coconut
  • Tip burn of Betel vine
 Other Disorders
  • Jonathan spot of Apple : Water Deficiency
  • Blackheart of Potato : Oxygen Deficiency
  • Richness in Cauliflower: Temperature
  • Cat face in Tomato : Temperature
  •  Blacktip of Mango : SO2, NO2
  • Tip burn / Pansukh of Rice: Oxygen Deficiency

Daily Dosage -JRF / SRF / IBPS Agricultural Field Officer Study Material - Nutrient Deficiency Symptoms - Soil Science Oneliner

Nutrient Deficiency Symptoms - Soil Science Oneliner

1. Dieback of citrus is due to deficiency of Copper (Cu).

2. Sickle leaf disease occurs due to deficiency of phosphorus.

3. Due to Calcium deficiency failure of terminal bud caused.

4. Yellow disease of tea is due to Sulphur deficiency.

5. Top sickness of tobacco is due to Boron deficiency.

6. Little leaf of cotton is due to Zn deficiency.

7. Pollen sterility in wheat is due to Boron deficiency.

8. Excess vegetative growth is due to supply of excess Nitrogen.

9. Whip-tail of cauliflower is due to Mo deficiency.

10. Deficiency symptoms of N,P,K,Mg and Mo appears in  older leaves.

11. Deficiency symptoms of Fe,Mn,Cu,S appears on new leaves.

12. Deficiency symptoms of Zn appear on both old and new leaves.

13. Purple colour in leaves is due to deficiency of Phosphorus deficiency.

14. Zn toxicity is reduced by addition of Super phosphate.

15. Condition when crop required more of given nutrient yet shows no deficiency symptoms is called as “Hidden Hunger”.

16. Sunflower is an indicator plant of Boron.

17. Osmotic regulation is maintained by Potassium.

18. Al & Si is also known as Ballast element.

19. Functional nutrients are 21 (17 essential + 4 beneficial).

20. Sodium (Na) is most important element for deflocculation of soil.

21. Calcium (Ca) is important for flocculation of soil.

22. Potassium is useful to increase disease resistance in plant.

23. Nutrient mobility concept was given by ‘R.Bray’.

24. Concept of functional nutrient was given by ‘D.J.Nicholas’.

25. Mycorrhiza is most suitable for the absorption of Phosphorus.

26. Nutrient index concept is introduced by ‘Parker’.

27. Reclamation disease is due to deficiency of Copper.

28. Master nutrient of oilseed is Sulphur.

29. Indicator plant for phosphorus deficiency is mustard.

30. Mg is responsible for activation of RUBP (Rubisco) and germination of pollen.

31. Zn is involved in Auxin production.

32. Mo is needed for synthesis of ascorbic acid.

33. Cl is used as nitrification inhibitor.

34. K is essential for tuber crops.

35. Phosphorus is also known as ‘Key of Life’.

36. Phosphorus is helpful for anti-lodging of plants.

37. Potassium is also known as Traffic Police Man.

38. White bud in maize is due to Zn deficiency

39. Excess of B Nutrient in soil causes the Deficiency of - Mo

40. Energy Exchange elements - H,O.

Daily Dosage - Soil Science Oneliner for all Competitive Exam

  Soil Science Oneliner for all Competitive Exam



           1. Maximum phosphorus availability in the range 6.0 to 6.5
2. The most deficient micronutrient in soil is zn
3. Soil fertility and fertilizers was written by Samuel l tisdale.
4. Intracellular deposits of silicon element is known as plant opals.
5.“Indian society of soil science” (ISSS) headquarters is located in New Delhi, 1934.
6.“International soil reference and information centre” is located  in Netherland(1966).
7.“International union of soil science” Australia(1924).
8. For nitrification optimum ph is 8.5.
9. Humus fraction lightest in colour is fulvic acid.
10. Pedoturbation is the process of soil mixing.
11. In India, Histosols soil order have negligible area.
12. Partical density of clay soil is 2.8 cm/cc.
13. First production of fertilizer in india is single super phosphate(SSP) 1906.
14. Calcareous soil is formed in arid as well as humid region.
15. Active soil forming factors are climate and organism.
16. Fungi have add highest biomass in soil.
17. Soil colour determination by munsell’s Colour chart.
18. Positive bacteria colour is red.
19. “Sulphur institute” is located in Washington DC (1960).
20. First product of urea is ammonium carbonate.
21. Foliar application is best method for application of Fe and Zn.
22. Soil application is the best method for Ca, B, S, and Mo.
23. Kandic and arfullic origin found in alfisol order.
24. Surface colour of alkali soil is black.
25.Lowest classification of soil is series.
26. Sugerbeet is an indicator plant for sodium.
27.Wheat is an indicator plant for copper.
28.Silicon is essential for Rice and Maize.
29.PH of cat clay soil <4.
30. Phosphorus solubilizer bacteria besillus, aspergillus and pseudomonas( trick BAP).

Daily Dosage - Soil Science Oneliner for all Competitive Exam

Soil Science Oneliner for all Competitive Exam


 
1.             Black soil are best suitable for Dry land Agriculture.

2.             Red color of red soil is due to presence of Iron oxides.

3.             Most dominant mineral present on earth crust is Feldspar (48%).

4.             Mechanical analysis of soil separation is done by Hydrometric method.

5.             Kaolinite is most dominant mineral present in Red soil.

6.             Clay soil has highest total pore space.

7.             The weight of furrow slice of soil is 2.25x 106 kg/ha.

8.             Order of black soil is vertisol.

9.             The term Zero tillage is coined by Jethrotull.

10.        USA is the first country to introduce zero tillage.

11.        The microorganisms has highest biomass in soil is Fungi.

12.        National Bureau of Soil Survey and Land Use Planning is located Nagpur.

13.        Central Soil Salinity Research Institute is located at Karnal Haryana.

14.        Central soil testing laboratory is located at Patna, Bihar.

15.        B horizon is also known as illuvial horizon.

16.        A horizon is also known isElluvial horizon.

17.        O horizon is absent in Arable soil.

18.        O horizon is present in forest soil.

19.        Highest production of FYM is in Karnataka.

20.        C:N ration of micro organism is 4:1 to 9:1

21.        Ammonical fertilizers should be applied in Reduced zone.

22.        Nitrate fertilizer should be applied in Oxidized zone.

23.        Wood is mainly decomposed by Actinomycetes.

24.        The smell of soil after the fresh shower is due to Actinomycetes.

25.        Population of actinomycetes is higher in Alkaline soil.

26.        By adding organic matter Bulk density will decrease.

27.        Vermiculite is a 2:1 non-expanding type of mineral.

28.        Montmorillonite is a 2:1 expanding type of mineral.

29.        Kaolinite is a 1:1 non-expanding type of mineral.

Sunhemp is most outstanding green manure crop.

Daily Dosage - Soil Science Oneliner for all Competitive exams

Soil Science Important One liner for all Competitive Exams


  1. Wheat is an indicator plant for copper.
  2. The density of soil water is maximum at 40c.
  3. Organic carbon content in soil average 0.5- 0.7%
  4. Available nitrogen-(240-280kg/ha).
  5. Available phosphorus- (11-22 kg/ha).
  6. Available potassium- (110-280 kg/ha).
  7. Available sulphur-(6-16 ppm).
  8. Enrichment of water bodies by nutrients and consequent bloom of algal and other aquatic plants is termed as ‘Eutrophication’.
  9. Particle density of Alluvial soil is 2.55 gm/cm3.
  10. Macro and Micro spore ratio should be 1:1 in soil.
  11. Fertilizer control order 1985.
  12. Marshy soil are generally deficient of Zn.

  13. Downward movement of nutrients and salts from the root zone with water is known as ‘Leaching’.
  14. A vertical section of soil through all its horizons is called ‘Soil Profile’.
  15. ‘A’ horizon is also known as Fertile horizon.
  16. The smallest volume of soil is called as pedon.

  17. A+B horizons are together called as Solum’.
  18. A+B+C horizons are together called as Regolith’.
  19. The arrangement of primary particles of the soil is known as Soil Structure’.
  20. The relative proportion of sand, silt and clay particles is termed as Soil Texture’.
  21. Newly formed alluvial soil is called as Khadar’.
  22. Old alluvial soil is termed as Bhangar’.
  23. Soil moisture content is determined by Tensiometer’.
  24. A mass of rotted organic matter made from waste is called as Compost’.
  25. Peaty soils are generally deficient of Cu