Factors influence these soils like the type of rocks that they come from, their age, rainfall and certain climatic factors, topography, and human activity. One very interesting characteristic of soil is its capacity to absorb and hold water due to how loosely or tightly soil particles are packed. The organic matter on the soil helps its water holding capacity or may affect it by causing changes on the soil, called soil density. The soil must provide a plant air to breathe, water to drink, nutrients and shelter from damaging conditions. Plants respond to the different soils.
Water holding capacity in soil is also important for plants.
Human population increase has become a problem for the environment and its refuse or waste. Waste disposal refers to the methods people use to get rid of unwanted materials. The overloading of the natural processes of decay can spread diseases. Most of the waste is buried and these sites are used for constructions. Some waste are burned in incinerators.