
TY  - JOUR
A1  - Close, EA 
A1  - Powell, HKJ 
T1  - A field method for exchangeable (1<sub>M</sub> KCl extractable) aluminum(<sub>III</sub>) in soils
JF  - Soil Research
JO  - Soil Res.
Y1  - 1989
VL  - 27
IS  - 4
SP  - 681
EP  - 684
KW  - 
UR  - https://doi.org/10.1071/SR9890681 
N2  - A rapid method for estimation of exchangeable (1 M KCl extractable) aluminium(III) in soils is reported. It involves a 5 min extraction of a measured volume of soil, followed by incremental addition of the supernatant to the metallochromic reagent chrome azurol S (CAS) in hexamine buffer (pH 4.9). Formation of Al (CAS) (purple) from CAS (amber) is rapid. Iron(III) is masked by ascorbic acid. The intermediate colour of the resultant solution containing complexed and non-complexed CAS is compared with standards in polystyrene cuvettes. Tests on 17 soils with KCI-extractable aluminium levels in the range 50-850 mg kg-1 established that aluminium extracted in 5 min (X, mg kg-') is related to the 16 h value (Y, mg kg-1) by Y = 1.43X+ 32; r2 = 0.962**); an approximate conversion factor of 1.5 (Y = 1 .50 X) was applied to all measured values to estimate soil alumimium values. 
ER  -

