Question

What is humus? Distinguish between Mor and Mull humus.

Answer 1

Hint: It is dark, organic material that forms in soil when plant and animal matter decays. It is partially decomposed organic matter. Humus contains many useful nutrients for healthy soil, which are essential to the fertility of the earth.

Complete step-by-step answer:
The organic component of soil, formed by the decomposition of leaves and other plant material by soil microorganisms. The thick brown or black substance that remains after most of the organic litter has decomposed is called humus. Earthworms help in mixing the humus with minerals in the soil. Humus is often used to fertilize the soil. Aside from adding nutrients, it also loosens the texture of the soil. Humus makes the soil porous, thereby, increasing its air and water holding capacity. Being black, it absorbs heat to warm up the soil.

Mor	Mull
Humus formation, or raw humus condition, occurs in the soil that has few micro –organisms or animals, such as earthworms, to decompose the organic matter that lies on the soil surface. Three humus types, mor, moder, and mull form in upland forests under aerobic conditions.	Humus formation is mostly found in the hardwood forests, deciduous forests, or grasslands and mostly in warm, humid climates. Granular humus layer known as mull, which is the porous mixture of organic material and mineral soil. Mull humus acts as a place of shelter for many bacterial and invertebrate animals such as earthworms.

Note: Out of the 8 types of soils found, alluvial soil and forest or mountain soil are found to have high humus content. But the soil that has an equal part of sand, silt and clay i.e. loamy soil is the type of soil which is richest in the humus content.