Tag: soil : our life

• The topsoil is darker because it contains dead organic material in many stages of decomposition. 
• This degradation produces a substance called humus that is composed of carbon-rich compounds and imparts a dark color. Thus, the correct answer is option D.

Humus is organic matter containing nutrients from the soil. It is nothing but dead and decaying organic matter where saprophytes convert complex organic material into simple nutrients. These nutrients are then available to the plants through humus.

Black cotton soil is rich in clay, which has very small sized particles. These small sized particles obstruct water movement and hence, this soil has high water holding capacity and low percolation.

Percolation tanks are artificial structures designed to facilitate the infiltration of surface water into the soil to recharge groundwater aquifers.

There are different systems constructed to increase the amount of water which is present in the groundwater reserves. The percolation tanks are constructed in the land which is highly permeable. The water from the runoff which gets collected in the tank is then percolated in the ground. This system helps to recharge the groundwater system. These are one of the methods which are used for the conservation of the water resources.

Soil porosity is percentage and type of soil pores or interstices. It is of two types - microspores and macrospores. Macrospores are  non capillary pores of more than 20 micrometer diameter. Gravitational water flows through macropores greater than 50 micrometer. Macropores hold air. In good soils,their number is 20 percent. Micropores are capillary pores with diameter of less than 20 micrometer. They hold capillary water. Good soil contain 30 percent microspores. Solubility and availability of plant nutrients depends on porosity because if the pore size is more water will wash away all the nutrients to water table as gravitational water and if porosity is less there will not be any air, respiration of roots and hence, absorption of nutrients will suffer.

Field capacity is the capacity of field. The amount of water retained by a unit weight of undisturbed soil after complete drainage under controlled conditions is called as field capacity.
Water held up in capillary space between soil particles is called as capillary water.
Gravitational water is the water that seeps down the surface of earth and makes up the water table.
Storage water is normally not used to describe soil water.

Venaparthy is a small village which is situated in the state of Andhra Pradesh. The village is known for being an area which is free from the problems due to groundwater pollution and water crisis. There are percolation tanks which are set up in the village and the nearby locales. These percolation tanks help in the collection of water in the earthen dams and recharge the groundwater in these regions. 

Soil salinity is the presence of excess salts especially those of sodium, potassium and magnesium.