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Determination of available BORON in given soil.

TITLE  - Determination of available boron in given soil.

Method -
1) Azomethine H
2) Hot water extraction method.

Scientists - burger and truog (1939) 

Reagents -
  • Azomethine H - Dissolved 0.45 gram Azomethine H and one gram ascorbic acid in hundred ml distilled water
  • Buffer solutions - Dissolved  250 gram ammonium acetate and 15 gram EDTA (disodium salt) in 400ml distilled water then add 125/8 Glacial acetic acid slowly.
Calcium carbonate solutions - 0.01 M Dissolved 1.11 gram calcium chloride in 900ml distilled water and make the volume of one litre.                                                                                                 PROCEDURE -
Extraction  - take 20 grams soil sample in conical flask (250 ml flask)
  •  Add 14 ml 0.01 molar calcium chloride solution.
  •  boil and Reflux for 5 minute.
  •  after cooling filter the content .
Estimation  - Take 5 ml filtrate in 25 ml of volumetric flask .
  • Add to 2ml buffer solution and 2ml Azomethine H solutions. 
  • stand for one hour for colour development.
  •  after 1 hour volume is made up to the mark (25 ml ).
  • measure the colour intensity on spectrophotometer at 420 NM wavelength .
  • run the blank 
  • (note don't use borosil glass in while procedures ).                                                       
  PREPARATION OF STANDARD CURVE.    
  •     Preparation of stock solution- 
0.571 gram boric acid dissolve in 1 litre of water 
  • Preparation of working solution. - take 5 ml of stock solution in volumetric flask and dilute the mark 100 ml.                            
  •  Take 0, 2, 6 ,8, 10 ml working solution in 25 ml of volumetric flask. 
  • Add 2 ml of buffer solution Azomethine H solutions. 
  • stand for 1 hour colour development after 1 hour volume is made up to the mark 25 ml.
  • measure the colour intensity on spectrophotometer.      
                         
   OBSERVATION 
  • weight of soil sample -    20 gram.
  •  volume of extract -          40 ml.
  •  volume of filter taken -   5 ml. 
  •  final volume of filtrate after colour development.                   -25ml .     
 Formula -
  • available Boron (mg/kg)=                                 y × spectrophotometer absorbance.               × volume of extractant/volume of filtrate taken.                                                                  × final volume/weight of soil.                           
  • Where y is Graph Factor.                                     
  • Calculations 
B = G. F. ×spectrophotometer absorbance (reading)                                                                      × 40/5.                                                                         × 25/20.                                                                                                                                    
  B = Graph factor × spectrophotometer absorbance × 10.     

(put graph factor & spectrophotometer reading)    
  • Available Boron = ----------mg/kg.                         
  • Interpretation of results :(rating) -
  • Low.              <0.5 mg/kg
  • Medium.       0.5 to 1mg/kg
  • High.              >1 mg/kg.          
 Results 
  • Hence given soil sample has -------(rating) content of boron. 

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