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Nitrogen is a chemical element; it has symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seventh in total abundance in the Milky Way and the Solar System.
Abundance (atom fraction) of the chemical elements in Earth's upper continental crust as a function of atomic number; [5] siderophiles shown in yellow Graphs of abundance against atomic number can reveal patterns relating abundance to stellar nucleosynthesis and geochemistry.
Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of soil or soil type; i.e., a soil containing more than 85 percent sand-sized particles by mass. [2]
One rock, "Bounce Rock," found sitting on the sandy plains was found to be ejecta from an impact crater. Its chemistry was different from the bedrocks. Containing mostly pyroxene and plagioclase and no olivine, it closely resembled a part, Lithology B, of the shergottite meteorite EETA 79001, a meteorite known to have come from Mars.
Soils with humus can vary in nitrogen content but typically have 3 to 6 percent nitrogen. Raw organic matter, as a reserve of nitrogen and phosphorus, is a vital component affecting soil fertility. [156] Humus also absorbs water, and expands and shrinks between dry and wet states to a higher extent than clay, increasing soil porosity. [174]
In general, organic matter contacting soil has too little nitrogen to support the biosynthetic needs of the decomposing soil microbial population. If the C:N ratio of the decomposing organic matter is above circa 30:1 then the decomposing microbes may absorb nitrogen in mineral form as, e. g., ammonium or nitrates. This mineral nitrogen is said ...
Some rocks, such as limestone or quartzite, are composed primarily of one mineral – calcite or aragonite in the case of limestone, and quartz in the latter case. [35] [36] Other rocks can be defined by relative abundances of key (essential) minerals; a granite is defined by proportions of quartz, alkali feldspar, and plagioclase feldspar. [37]
Nitrogen is the most critical element obtained by plants from the soil, to the exception of moist tropical forests where phosphorus is the limiting soil nutrient, [36] and nitrogen deficiency often limits plant growth. [37] Plants can use nitrogen as either the ammonium cation (NH 4 +) or the anion nitrate (NO 3 −).