The nitrogen is absorbed by the plant in some form of combination from the soil.
The nitrogen of the atmosphere is not called into requisition, except by a few plants and under special conditions, as will be explained later.
Similar observations have been made in the case of various compounds of nitrogen, though these have not been so complex as the proteids.
The power of fixing atmospheric nitrogen by the higher plants seems to be confined to this solitary group, though it has been stated by various observers with more or less emphasis that it is shared by others.
These are: (I) That the green plant is so stimulated by the symbiotic association which leads to the hypertrophy, that it is able to fix the nitrogen or cause it to enter into combination.
Whichever opinion is held on this point, there seems no room for doubt that the fixation of the nitrogen is concerned only with the root, and that the green leavec take no part in it.
Indicates that if 28 grammes of nitrogen could be made to unite directly with 16 grammes of oxygen to form nitrous oxide, the union would cause the absorption of 18500 calories.
Manures), manufactured or imported, to state the percentage of the nitrogen, of the soluble and insoluble phosphates, and of the potash in each article sold, and this statement was to have the effect of a warranty.
The exhaustion of the soil induced by both barley and wheat is, however, characteristically that of available nitrogen; and when, under the ordinary conditions of manuring and cropping, artificial manure is still required, nitrogenous manures are, as a rule, necessary for both crops, and, for the spring-sown barley, superphosphate also.
It was in the year 1886 that Hellriegel and Wilfarth first published in Germany the results of investigations in which they demonstrated that, through the agency of micro-organisms dwelling in nodular outgrowths on the roots of ordinary leguminous plants, the latter are enabled to assimilate the free nitrogen of the air.
Since Hellriegel's striking discovery farm crops have been conveniently classified as nitrogen-accumulating and nitrogenconsuming.
The attitude taken up later on with regard to this problem is set forth in the following words, which are quoted from the Memoranda of the Rothamsted Experiments, 1900 (p. 7): - " Experiments were commenced in 1857, and conducted for several years in succession, to determine whether plants assimilate free or uncombined nitrogen, and also various collateral points.
Under this system the clover is ploughed up in the autumn, the nitrogen stored up in its roots being left in the soil for the nourishment of the cereal crop. The following summer the wheat crop is harvested, and an opportunity is afforded for extirpating weeds which in the three previous years have received little check.
The root-crops, indeed, may contain two or more times as much nitrogen as either of the cereals, and the leguminous crops, especially the clover, much more than the root-crops.
The greater part of the nitrogen of the cereals is, however, sold off the farm; but perhaps not more than to or 15% of that of either the root-crop or the clover (or other forage leguminous crop) is sold off in animal increase or in milk.
Most of the nitrogen in the straw of the cereals, and a very large proportion of that of the much more highly nitrogenyielding crops, returns to the land as manure, for the benefit of future cereals and other crops.
Wouldn't that be something: Plants that would convert nitrogen from the atmosphere directly into ammonia they could use or plants that gave off the odor of other plants that pests avoid?
The chief thing in his eyes was not the nitrogen in the soil, nor the oxygen in the air, nor manures, nor special plows, but that most important agent by which nitrogen, oxygen, manure, and plow were made effective-- the peasant laborer.