• nitrification
  • The process by which ammonia compounds, including man-made fertilizer and the humus provided by organic matter or plant and animal origin, are converted into nitrites and then nitrates, which are then absorbed as a nutrient by crops. Excess nitrate can be leached into surface waters and groundwaters, causing pollution. Excess nitrate may also be converted by microbes back into gaseous nitrogen, which is an important greenhouse gas, and released back into the atmosphere. The ultimate source of nitrogen in the ecosystem is the molecular nitrogen in the atmosphere. To a very limited extent, some dissolves in water. However, none is found in rock.
Abstract from DBPedia
    Nitrification is the biological oxidation of ammonia to nitrite followed by the oxidation of the nitrite to nitrate occurring through separate organisms or direct ammonia oxidation to nitrate in comammox bacteria. The transformation of ammonia to nitrite is usually the rate limiting step of nitrification. Nitrification is an important step in the nitrogen cycle in soil. Nitrification is an aerobic process performed by small groups of autotrophic bacteria and archaea.

    硝化作用(しょうかさよう)はアンモニアから亜硝酸や硝酸を生ずる微生物による作用を指す。アンモニアを酸化し亜硝酸を生ずるアンモニア酸化細菌・アンモニア酸化古細菌、亜硝酸を酸化し硝酸を生ずる亜硝酸酸化細菌により反応が進む。これらの細菌は独立栄養細菌で、それぞれアンモニアの酸化、亜硝酸の酸化によりエネルギーを得る。有機成分の存在下ではほとんど増殖せず、死滅することもある。 土の中では、有機物に含まれる有機態窒素がアンモニアまで分解される、アンモニアから硝酸を生ずる硝酸化成が進み、作物に吸収される。野菜など多く園芸作物はアンモニア態窒素より硝酸態窒素を好んで吸収するであるため、この反応はきわめて重要である。アンモニア濃度が高く、硝酸化成が進まない場合、が生じることがある。