Page 1353 : NITROGEN — NITROGEN-GATHERING CROPS
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Ni′trogen is an elementary [[../Gas|gas]] which in the free state forms nearly four fifths by volume of our atmosphere. In combination with other elements, nitrogen is a necessary constituent of all plants and animals, and it forms a very large number of important compounds, both natural and artificial. Its presence in the atmosphere was discovered in 1772 by Rutherford, at that time professor of botany in the [[../Edinburgh University|University of Edinburgh]]. It was more particularly investigated soon after by Priestley, Scheele, [[../Cavendish, Henry|Cavendish]] and [[../Lavoisier, Antoine Laurent|Lavoisier]]. It is a colorless, tasteless, odorless gas, and was formerly regarded as permanent and incondensable; but it can be liquefied at a sufficiently low temperature. Nitrogen is slightly lighter than atmospheric [[../Air|air]], and is fourteen times as heavy as [[../Hydrogen|hydrogen]]. It is but slightly soluble in [[../Water|water]], one hundred volumes of water at ordinary [[../Temperature|temperature]] dissolving only one and a half volumes of nitrogen.
While nitrogen is a constituent of all plant and animal organisms and of many important compounds, it is, in a free state, rather inert toward other elements and does not readily enter into direct combination with them. It is not combustible, nor does it act in the atmosphere as a supporter of combustion, as a lighted taper plunged into a jar of nitrogen will at once be extinguished. Nitrogen is not poisonous, since it is breathed freely along with oxygen by all animals; but it cannot support life, and an animal placed in it will die from suffocation for want of the [[../Oxygen|oxygen]] necessary for breathing. Its function in the atmosphere seems to be mainly that of diluting the oxygen with which it is there associated. Although nitrogen forms about 79.1 per cent. of the total volume, and 77 per cent, of the total weight, of the atmosphere, the free gas cannot be taken up by plants directly, but it is combined with other elements through the agency of certain [[../Bacteria|bacteria]] that exist in nodules on the [[./Root|roots]] of [[../Legume|leguminous]] plants, that is, those that are related to [[../Clover|clover]], [[../Pea|peas]] etc. Other plants, particularly [[../Grass|grasses]] and grains which require much nitrogen, are dependent upon the combined nitrogen of the [[../Soils|soil]]; hence nitrogenous [[../Fertilizers|fertilizers]], such as dried [[../Blood|blood]], ammonium salts and nitrates, as well as ordinary manures, are important in agriculture for use on soils containing insufficient nitrogen. Two of the important compounds of nitrogen are [[../Nitric Acid|nitric acid]] and [[../Ammonia|ammonia]]. This element also is an essential constituent of the [[../Proteids|proteids]] or albuminoids, which make an important part of our [[../Food|food]], as well as of the alkaloids, most of the dyes and a host of other natural and artificial compounds.
H. L. Wells.
Nitrogen-Gathering Crops all belong to the family of [[../Legume|leguminous]] plants or Leguminoseæ, having irregular, conspicuous [[../Flower|flowers]] or clusters and seeds in [[../Pod|pods]]. The bean and [[../Pea|pea]] are good examples. The [[../Clover|clovers]] do not seem at first sight to answer this description. All have abundant foliage, root deeply, and are remarkable for their ability to take pure [[../Nitrogen|nitrogen]] from the [[../Soils|soil]] and store it up in form available as plant and animal [[../Food|food]]. This is done by means of germ-like organisms which grow inside of tiny lumps on the [[../Root|roots]]. These nodules can be seen by washing the earth from the roots of any of these plants, and range in size from that of a pin-head to that of a small pea. These nodules will not appear on clover roots if none of the germs exist in the soil. Such a soil can now be inoculated with the germs by applying a solution containing them. The germs are put up in dry form like [[../Yeast|yeast]]-cakes and can be obtained from the Department of Agriculture, and be dissolved to make the solution. The nitrifying action goes on best in well-ventilated soils. In poorly drained soils just the opposite process, denitrification, is apt to occur, reducing plant food to unavailable simple nitrogen. The subject of nitrifying [[../Bacteria|bacteria]] is very complex, as they possibly also exert a fermenting influence on the minerals of the soil. Experiments have shown that an acre of [[../Cow-Peas|cowpeas]] at the Louisiana Experiment Station produced 65 pounds of nitrogen, and an acre of crimson clover at Cornell University produced 156 pounds, 30 of which were in the roots. Other clovers produce a greater proportion in the roots, as the mammoth clover, with 78 pounds in the roots out of a total of 146 pounds. It grows best in wet soils that usually are deficient in nitrogen, and so leaves much in the soil when the tops are cut off. Red clover, the usual variety grown on loams and heavier [[../Clay|clays]], contained
