142 



[August, 1908, 



SCIENTIFIC AGRICULTURE. 



NEW NITROGEN FERTILIZERS. 



By L. G. Blackman. 



The principal constituents of plant 

 food are present in greater or less pro- 

 portion in most soils. As the latter are 

 formed by the disintegrating and general 

 weathering process of rocks, the com- 

 position of a particular soil is dependent 

 to a great extent upon the nature of 

 the rock from which it has been derived. 

 Intermingled with the inorganic decora- 

 posed rock there is present in every 

 f'ertilie soil a variable proportion of 

 decomposed organic matter, the accu- 

 mulation of former generations of 

 animal and vegetable growths. It is the 

 latter ingredient, termed " humus " 

 which gives the soil much of its agricul- 

 tural value, and upon which to a great 

 extent plants feed, for vegetation, as 

 well as animals, is incapable of support- 

 ing life directly from inorganic sub- 

 stances alone. 



In a natural state the earth's successive 

 growths of vegetation contribute to the 

 accumulation of the soil's humus. Each 

 generation returns to the earth an added 

 deposit of matter in a form readily 

 available as plant food. The continual 

 cultivation of crops and their removal 

 from the soil by man, however, depletes 

 the soil of much of its valuable plant 

 food, and this process being continued, 

 a time is soon reached when the land 

 becomes so exhausted that it cannot be 

 profitably cultivated without artificial 

 reinforcement. 



In order that a plant may grow to 

 advantage, it is of prime importance that 

 a sufficient supply of all the elements 

 of its food be present in an assimilable 

 form. At times, although such elements 

 are contained in the soil, they are locked 

 up in some chemical combination with 

 other elements, which renders them 

 unavailable by vegetation. Speaking 

 broadly, the main necessary food of 

 plants may be said to be carbon, hydro- 

 gen, oxygen and nitrogen, and in less 

 degree potash, lime, magnesia and 

 phosphoric acid. 



The four latter foods (being the 

 ingredients of the primitive rock)' are 

 abundant in most soils, and as the 

 supply of carbon, hydrogen and oxy- 

 gen is usually fully provided for by 

 means of rain and the atmosphere, the 

 chief question affecting the well-being 

 of a plant, once the soil has been deplet- 

 ed of its natural humus, is a supply 

 of available nitrogen. This element 

 constitutes the chief bulk of our atmos- 

 phere, but plants are unable to assi- 



milate it in a free state, that is, unless 

 it is first* chemically combined with 

 another element. Although surrounded 

 by an inexhaustible supply of this neces- 

 sary food, vegetation, therefore, will 

 languish, and die unless some means is at 

 hand to render it available. This is 

 generally accomplished by the chemical 

 combination of nitrogen with hydrogen 

 in the form of ammonia, or with potash 

 or soda in the form of one of the well- 

 known " nitrates," so largely employed 

 as artificial fertilizers. 



Nitrogen is a necessary constituent 

 of every organic body. Although it 

 plays so important a part in the com- 

 position of living matter and exists in 

 such inexhaustible quantity in the atmos- 

 phere, the free nitrogen of the air is not 

 drawn upon for plant and animal food, 

 becauss it possesses the property of 

 refusing, under most circumstances, to 

 combine with other substances. This pe- 

 culiarity of nitrogen is remarkable when 

 we consider the readiness with which 

 some other elements combine with one 

 another as seen, for instance, in the case 

 of oxygen. The slow combination of this 

 latter gas with some metals is exempli- 

 fied in the coi rosion or rust of iron and 

 in the tarnishing of silver. The more 

 rapid and energetic combination of oxy- 

 gen with other substances produces, as 

 is well-known, the phenomenon of fire. 



So noteworthy is the inertness of 

 nitrogen, that Lavoisier, the emnient 

 French chemist, in reference to this 

 quality termed it Azote, a name signifiy- 

 ing "without life," and which is still 

 in general use by the French. On ac- 

 count of this property the element was 

 long regarded as a more or less useless gas 

 whose chief function lay in diluting 

 the atmospheric oxygen and thus ren- 

 dering it suitable for animal respiration. 



How comes it then, in view of the 

 refusal of nitrogen to enter into com- 

 binations with other elements, that 

 this element, so extremely insoluble in 

 water, plays such an important part in 

 the economy of plant life ? What subtle 

 force is at work which overcomes its 

 inert quality and renders it suitable for 



* The distinction between a mechanical and a 

 chemical mixture is most important. In a mecha- 

 nical mixture the ingredients are simply mixed 

 together aiid no new body is formed, while in a 

 chemical mixture an entirely new body is produced. 

 The mechanical mixture of hydrogen and oxygen 

 is an invisible gas, but their chemical mixture 

 produces water. In the air, oxygen and nitrogen 

 are mixed mechanically, while if they were in 

 chemical combination they would produce suffocat- 

 ing ammonia and nitric acid gasses in which 

 nothing now living could exist, 



