It is hard to believe, but most of the chemical, physical and biological phenomena occurring in nature depend on the humidity of the environment. As concerns the soil, humidity is not a stable feature of soil cover. It is influenced by many factors: meteorological conditions, groundwater level, mechanical soil composition, nature of vegetation, etc. Nevertheless, soil moisture plays an important role in the food chain, provides the growth and development of plants that ultimately become an animal and human nutrition. Due to evaporation, percolation, absorption, diffusion, natural and artificial water supply, soil moisture undergoes to complex dynamism, which constantly changes the ratio between liquid and gaseous phases. Soil humidity is about 0.001 percent of the total amount of water on Earth, but without it, plants cannot grow. Soils play a significant role in the hydrological cycle of our planet. The total amount of water vapor rarely exceeds 5 ppm compared to   the wight of the soil, but the condensed forms (liquid and/or ice) can easily reach 30-50%. 

Water enters soil from above as precipitation (rain or snow) or snowmelt, and from below as groundwater rises. The top surface of the groundwater is called the water table. Water is absorbed through plant roots, moves through plants, and evaporates back into the atmosphere through a process called transpiration. Water in soil is subject to freezing, thawing or evaporating as temperatures fluctuate, which affects plant growth.

Data about soil moisture can help crop growers produce the most robust yields. Soil moisture data also helps us better understand and predict weather and climate changes, early drought (an extended period of below-average precipitation that affects crop production and water supplies) warning signs, the extent of flooding and even help to identify the possible spread of diseases caused by insects that breed in standing water.

Soil moisture is affected by a variety of factors including soil texture (particle size), precipitation, vegetation (amount and type) and topography (landforms—hills, valleys, etc.). In general, soil particle size and soil moisture are inversely related. Soil layers made up of large particles retain less soil moisture. This is mainly due to gravitational water infiltrating (permeating through open spaces) easily through the larger pore spaces between larger particles.

More precipitation potentially means more soil moisture, but the type and intensity of the precipitation affect the amount of soil moisture, too. Long, moderate rainfall has the opportunity to soak into the soil, increasing soil moisture content in soil layers. Short, intense periods of precipitation can cause flooding, as the soil cannot absorb It quickly. The amount of vegetation cover also plays a role in soil moisture content. More vegetation cover leads to more organic ground cover, which protects the surface soil from evaporation and retains soil moisture.

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