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Agronomic Services — Mehlich-3 Extractant

 

0.2N CH3COOH + 0.25N NH4NO3 + 0.013N HNO3 + 0.015N NH4F + 0.001M EDTA

 

Function of components

Acetic acid (CH3COOH)

  • buffers the extracting solution to pH 2.5 when all reagents are added and mixed, thus preventing calcium from being precipitated as calcium fluoride.

Ammonium nitrate (NH4NO3)

  • facilitates extraction of basic cations such as calcium, magnesium, sodium and potassium &
  • reacts with acetic acid to form ammonium acetate.

Nitric acid (HNO3)

  • extracts a portion of calcium phosphates &
  • its acid component [H+] aids in extraction of basic and micronutrient cations.

Ammonium fluoride (NH4F)

  • the fluoride extracts iron and aluminum phosphates &
  • the NH4+ ion complements ammonium nitrate in extracting basic cations.

Ethylenediaminetetraacetic acid (EDTA)

  • chelates micronutrients (particularly copper) &
  • prevents precipitation of calcium fluoride.

 

 


Last Update April 24, 2013

 

 

NCDA&CS Agronomic Services Division, Colleen M. Hudak-Wise, Ph.D., Director
Mailing Address: 1040 Mail Service Center, Raleigh NC 27699-1040
Physical Address: 4300 Reedy Creek Road, Raleigh NC 27607-6465
Phone: (919) 733-2655; FAX: (919) 733-2837