humus content in laterite soil ; alluvial soil ; mountainous soil and black soil .And also specify which is the highest amongst them .
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In laterite soil, the humus content is low as due to high temperatures most of the humus is taken up quickly by trees.
In alluvial soil, chemical contents such a potash, lime etc. are high but they are deficient in humus and nitrogen.
Mountain soils are rich in humus, but most of the humus present is not fully decomposed.
Black soils are deficient in humus or in some cases, they completely lack it.

Hope this information will clear your doubts about the topic.  
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