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Nitrogen is plentiful in the Earth's atmosphere, and a number of commercially-important agricultural plants engage in nitrogen fixation (conversion of atmospheric nitrogen to a biologically useful form). However, plants mostly receive their nitrogen through the soil, where it is already converted in biological useful form.
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 −).
In plants with bacterial symbionts, which fix atmospheric nitrogen, the energetic cost to the plant to acquire one molecule of NH 3 from atmospheric N 2 is 2.36 CO 2. [13] It is essential that plants uptake nitrogen from the soil or rely on symbionts to fix it from the atmosphere to assure growth, reproduction and long-term survival.
In its natural state, nitrogen exists primarily as a gas (N2) in the atmosphere, making up about 78% of the air we breathe. Nitrogen finds extensive usage across various sectors, primarily in the agriculture industry, and transportation. Its versatility stems from its ability to form numerous compounds, each with unique properties and applications.
Soil gases (soil atmosphere [1]) are the gases found in the air space between soil components. The spaces between the solid soil particles, if they do not contain water, are filled with air. The primary soil gases are nitrogen, carbon dioxide and oxygen. [2] Oxygen is critical because it allows for respiration of both plant roots and soil ...
Approximately 78% of Earth's atmosphere is N gas (N 2), which is an inert compound and biologically unavailable to most organisms.In order to be utilized in most biological processes, N 2 must be converted to reactive nitrogen (Nr), which includes inorganic reduced forms (NH 3 and NH 4 +), inorganic oxidized forms (NO, NO 2, HNO 3, N 2 O, and NO 3 −), and organic compounds (urea, amines, and ...
Plants that contribute to nitrogen fixation include those of the legume family—Fabaceae— with taxa such as kudzu, clover, soybean, alfalfa, lupin, peanut and rooibos. [45] They contain symbiotic rhizobia bacteria within nodules in their root systems, producing nitrogen compounds that help the plant to grow and compete with other plants. [58]
The Leaf Color Chart (LCC) is a diagnostic tool used to determine the nitrogen level in rice plants relative to the shade of green of the plant's leaves. It is a ruler-shaped strip containing at least four panels of color, ranging from yellowish green to dark green.