Land Resources

Land forms 1/5th of earth’s surface. About 36.6% of land is occupied by human dwellings, deserts, mountains, rocks, glaciers and polar ice marshes. About 30% of land is covered by forests About 22% is occupied by meadows and pastures. Only 11% is suitable for ploughing. Surface layer of land is soil which occupies 4/5th of the land.
Variads of bacteria, fungi and several animals which are involved in detritus pathway inhabit the soil. Study of soil is called pedology. It is formed from two processes¾weathering (breaking down of rocks into small particles) and pedognesis (maturation of soil through development of humus).

Of the particulate constituents clay and humus are main determinantes for properties of soil. Humus is formed by accumulation of partially of soil. Humus is formed by accumulation of partially decayed and partially synthesized organic materials.
It makes the soil granular. It increases air spaces thus increasing water holding capacity of sandy soils. Humus is rich in nutrients and so enchances plant growth. Being black it absorbs heat and warms up the soil An ideal soil has 20% non-capillary pores and 30-40% capillary pores.