Gardening Notes

Hutt News, Volume 2, Issue 37, 20 February 1930, Page 9

Gardening Notes

NITROGEN AND PLANTS.

The subject of nitrogen and its relation to Riant life, is continually cropping up from time to time in the newspapers, as to the great things done, and the possibilities- .to be expected from it as a plant and food producer. It is a recognised thing that he who would be successful in 'horticulture today must have some knowledge of the chemical constituents of his plants, and what they feed •■ on, .so ,as to get the best results from them. Of late years it has been found that nitrogen, in conjunction with carbon, plays a greater part in our plant and food economy than we are often aware of. v'

Nitrogenous constituents are of great importance in the healthy growth and production'of leaf and flower, as well a3 of flavour, as seen in fruits and, vegetables dependent in no small: measure for the proper supply of this desirable ingredient through soil and manuring, To thoroughly understand tho process of nitrogen, the whole chemical composition of plants would need to be studied, but in this article we will confine out remarks to nitrogen and its uses—its peculiar nature and vital necessity to mankind, its increasing rarity in an available form, its vast abundance in a ''free' state, and the attempts to "fix" it in a cheap form. ■ :

The department of the nitrogen atom is extremely interesting to t>he student of chemistry. It is one of the most and most powerful of the elements when it enters into combination with other atoms. It drives ,our bulletsin the form of gunpowder, explodes our mines as dynamite and guncotton; it dissolves our metals as nitric acid; it extracts our gold as cyanide, and in many other ways menaces or ministers to mankind.

Scientists in the past have been ac- I eustomed to ascribe much, to carbon a» the paramount constituent of the body, but the vital moving thing we call life now recognised to be the versatile and restless nitrogen. Yet this nitrogen, which is so useful and energetic when combined with otJier elements, ibe-. comes, when isolated by itself, a stubborn, lazy and inert gas. It constitutes 79.1 per cent, of volume, and 76.9 pet cent by weight, of theatmosphere; and is also. found widely distributed as .nitric acid' and metallic nitrjates, as well, as in ammonia, and in animal and vegetable organisms. It is a colourless, tasteless and odourless gas. Nitrogen is either "free" or "fixed." Nitrogen, of the air is "free" when mixed ■with, other elements, it is "fixed." We have it in the fixed form in the following well-known fertilisers, Peruvian guano—ammonium sulphate and nitrate

of soda.

As plants—and animals, too—depend upon tie soil for every trace of nitrogen they contain, the soil is continually being exhausted; and the object of science is, to -find a more speedy way to replenish the-soil than the slow trans formation' of billions of nitrifying organisms used by NatuTe. „

For we filch nitrogen from the soil much, faster then it is restored by natural processes, and the land grows sick. ITo cure this, as we all know, we, have to manure it. "That is, we add to the soil substances containing fixed nitrogen in the form of annimal inanuTe orfertilisers. Scientists look upon these forms of, manures as having their limitation, and are seeking a means of fixing the inexsiaustable supply of free nitrogen in the air, in some available cheap form. It has been-known to our forefathers for generations past that grain and root crops always thrive best where leguminous plants have grown. After careful search tiiere was found what they /called the nitro-bacteria nodules on the Toots^ which are capable of storing up nitrates from the nitrogen of the air.

Of this Dr. Voelfrher says; "On the roots of leguminose plants of the suborder of Papilionaeeoe have been observed swellings, or 'nodules,' as they are called, and examination of these has shown them to be of bacterial origin, and to contain organisms which' •have the power of assimilating the atmospheric nitrogen distributed throughout the soil, and of. building it up to the nitrogenous constituents of these plants It was found by Hellriegel that when these nodules were present the plant

throve and contained nitrogen far in excess of anything capable of being accounted for by the nitrogen in the seed the soil, the water or the ammonia of the atmosphere, while in the absence of nodules tie nitrogen and consequent (growth were bounded by the amounts i supplied from the other sources. Also, that wh.en nitrogen was withheld, only a stunted growth, was obtained, and no nodules were formed. Hence the conclusion —since abundantly confirmed— was come to that these plants were able, through the agency of the -organisms contained in the nodules on their roots, to take .up and assimilate atmospheric nitrogen. In this way has been explained^ what was far a Jong time ? a myster,viz., that clovers, peas, beans, while themselves essentially nitrogenous in composition, were able to dispense with special nitrogenous manuTing, and at ..the same time left the soil on which they had being growing richer in nitrogen than before. It would seem possible; too,that there are certain low forms of organism in the soil which possess this same power, but. with this exception, the capability would appear to bo'restricted to t&e 1 Papilionaceoe. Prom this has come tire idea of inoculating the seed before sowi ing with materials that may ensure the. production of nodules on the roots to utilise atmospheric nitrogen. ' ' Illinois Bull No. 94-2-04, says: "In general, each species of leguminous plants'- thas its own particular form of bacterium which produces nodules up the roots, and that unless particular bacteria are present ;in the soil no nodules will bo formed, and the crop will suffer from the lack of nitrogen. The soil .must, if it lack the bacteria, be inoculated with, it."

This led up to a Californian "firm" sending out small cardboard boxes, resembling sweetmeat boxes, containing a small tube one and a half inches by half-inch, and a tiny packet, for 25 cents. By mixing the- contents of the packet, with water, nitrifying bacteria are released, when we may either wet the seed before sowing 'or. mix t&e soil with the liquid and sprinkle round the plants, and stiT -it in. •

American experimenters say the culture itself does not contain the nitrogen but simply the organisms which .have the poweT of fixing nitrogen, and which —if properly handled—twill increase in »such numbers as to be of material benej fit to the plants with which they have [been associated.

A French scientist, speaking of the use of nitrate of soda in the. culture of flowers, says: "The nitrate was in all cases beneficial, especially, when used in a diluted state. The most generally useful proportion for pot plants was' found to "be one part of nitratei jtp 2,000 parts of water —in other words, one-half gramme (says, 8 grains) to one litre (If pints; imperial) of water; 8 or 10 waterings with the solution were administered at intervals, during the growth, of the plant, and the greatest care taken to secure accurate results-

Some difference exists as to how. the plants •get fkere nitrogen. Many claim thai; the nitrogen is conveyed to tho soil by rain in the several forms of ammonia, nitric .acid, and nitrous acidy and these, by the process of nitroficationj" and oxidisation, are, converted into nitrates, the form in which, they become -available for* use by the plants. Th^ change into nitrates is affected in tfce soil by organisms" known as nitrifying organisms or bacteria, whose activity depends on a proper soil base, such as lime, oxygen, and suitable temparatuTe. Carbonic acid, with, water provides the main portion of the plant's structure. From this it obtains nearly the whole of its caiibon, which is taken in by thie leaves, and decomposed in the presence of sunlight, arid distributed to build up different parts of its structure; There is no evidence that plants have power to take in nitrogen' by their leaves, but recent discoveries have shown that "tliey have the power to utilise it by their., roots. • i

But that whicE concerns us most is, of what use is this nitro-culture to t»he gardener? According to experiments, it is of little use where-the soil is already rich in nitrogen, as the nodule-forming bacteria have a preference for- poor or medium soils.

- A yew tree •which is said to date back to prehistoric times-grows-in Scotland. It is thought that an unfinished) design of entwined hearts was hurriedly abandoned owing to -the approach of a hungry brontosaurus.-