Question

Deep black soil is productive due to high proportion of

(a) sand and zinc

(b) gravel and calcium

(c) clay and humus

(d) silt and earthworm.

Answer 1

The answer is (c) clay and humus.

Explaination:

Clay is tthe material which has particle size less than 2 micron and exhibits plasticity characteristics on absorbing water into it and shrinks on removal of water. This is because the minerological properties of clay.

Humus is a colloidal substance and increases the soil's cation exchange capacity, hence its ability to store nutrients by chelation. While these nutrient cations are accesible to plants, they are held in the soil safe from being leached by rain or irrigation.

Also, humus can hold the equivalent of 80-90% of its weight in moisture and therefore increases the soil's capacity to withstand drought conditions.

The dark color of clay and humus helps to warm up cold soils in spring.