TheOxygen cycleis the biogeochemicalcyclethat describes the movement ofoxygenwithin and between its three main reservoirs: the atmosphere (air), the total content of biological matter within the biosphere (the global sum of all ecosystems), and the lithosphere (Earth's crust).2)the trapping of the sun's warmth in a planet's lower atmosphere, due to the greater transparency of the atmosphere to visible radiation from the sun than to infrared radiation emitted from the planet's surface.3)a microscopic organism, especially a bacterium, virus, or fungus.

Nutrient managementis the science and practice directed to link soil, crop, weather, and hydrologic factors with cultural, irrigation, and soil and water conservation practices to achieve optimalnutrientuse efficiency, crop yields, crop quality, and economic returns, while reducing off-site transport ofnutrientsSoil erosionis the displacement of the upper layer of soil, one form of soil degradation. A low level of erosion of soil is a naturally occurring process on all land. The agents ofsoil erosionare water and wind