Hot water extractable soil

The hot water extractable soil B method is based on refluxing air dry soil for 10 minutes with deionised water at a 1 2 soil/solution ratio. After replacing liquid lost during reflux, extracts are filtered while hot and allowed to cool. The first of the two analytical finishes is a colorimetric procedure which utilises azomethine-H (Rayment Higginson 1992). It is preferred when ICPAES is not available. Other colorimetric procedures for determining B, including carminic acid (Hatcher Wilcox 1950) and curcumin (Hayes  

Metcalfe 1962) need concentrated acids or organic solvents. The likelihood is that ICPAES will yield higher results than azomethine-H. 

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