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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 −).
A young cabbage plant exhibiting nitrogen deficiency. Nitrogen deficiency is a deficiency of nitrogen in plants. This can occur when organic matter with high carbon content, such as sawdust, is added to soil. [1] Soil organisms use any nitrogen available to break down carbon sources, making nitrogen unavailable to plants. [1]
However, the excessive or inefficient use of nitrogen fertilizers can lead to environmental problems such as nitrogen leaching, runoff, and emissions of nitrogen oxides (NOx). [4] Nitrogen leaching occurs when nitrogen compounds, primarily nitrates , move through the soil profile and enter groundwater, potentially contaminating drinking water ...
[40] [41] From 1836 to 1876, Jean Baptiste Boussingault demonstrated the nutritional necessity of minerals and nitrogen for plant growth and development. Prior to this time influential chemists discounted the importance of mineral nutrients in soil. [42] Ferdinand Cohn is another influential figure. "In 1872, Cohn described the 'cycle of life ...
Plants called legumes, including the agricultural crops alfalfa and soybeans, widely grown by farmers, harbour nitrogen-fixing bacteria that can convert atmospheric nitrogen into nitrogen the plant can use. Plants not classified as legumes such as wheat, corn and rice rely on nitrogen compounds present in the soil to support their growth.
Nitrogen effects on biodiversity, carbon cycling, and changes in species composition have also been demonstrated. In highly developed areas of near shore coastal ocean and estuarine systems, rivers deliver direct (e.g., surface runoff) and indirect (e.g., groundwater contamination) N inputs from agroecosystems. [8]
Another important tool is the use of the nitrogen isotope [[15 N]], which can be distinguished from the more common 14 N isotope. Nitrogen-containing compounds thus labeled can be tracked and measured as they move through the fungus and into the plant, as well as how they are incorporated into nitrogen-containing molecules.
Nitrogen and potassium are also needed in substantial amounts. For this reason these three elements are always identified on a commercial fertilizer analysis. For example, a 10-10-15 fertilizer has 10 percent nitrogen, 10 percent available phosphorus (P 2 O 5) and 15 percent water-soluble potassium (K 2 O). Sulfur is the fourth element that may ...