It is everywhere. The air we breathe is mostly nitrogen. It is in the soil, bound less to porous soils than heavy soils, and available to plants through the roots as ammonium or nitrate ions. Some organisms accumulate nitrogen from the air. The bacteria that do this accumulate the nitrogen in nodules on roots and make it available to the soil when the plant dies and the tissues breakdown. From there it can be absorbed by other plants. Nitrogen is part of molecules that are found in all aspects of theplant's physiology. At optimal levels they contribute to the growth and development of the plant in a myriad of ways. This is not to say that there is always enough nitrogen to support plant health. Deficiency symptoms in plants can be expressed as a discoloration of the foliage. Too much nitrogen can cause plant tissues to be "hot" to the taste. Nitrogen is available commercially either in synthetic formulations, alone or in combination with other nutrients, or in an organic form, principally as highly pure urea or as raw manure. Once the nitrogen is solubilized in the soil, and becomes available to the plant, there is no difference in the ion form that crosses the root cell membrane regardless of the type of the material originally placed into the soil. Proponents for both sides state the benefits; the synthetic material is readily available to the plant, the organic material is released over time likely making sure the great majority of it is used by the plant. There are other pros and cons to useof synthetic or organic in vegetable production but that is not the aim of this commentary.
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