THE IRRIGATION AGE. 



599 



Notes on Practical 

 Irrigation 



D. H. Anderson 



Plant Foods Their Nature Distribution and Effects in 

 General. 



There are four substances which are essential to all 

 plant food; without them few plants could live, and what 

 is surprising, they form a very large portion of every 

 plant in one form or another. These substances are: 

 Carbon, oxygen, hydrogen and nitrogen. We shall take 

 them up in rotation and briefly explain their origin, nature 

 and action. 



Carbon. 



Carbon is generally known under the form of coal, 

 any kind of coal, but for experimental purposes it is 

 usually wood charcoal that is considered the nearest ap- 

 proach to pure carbon, there being none except the dia- 

 mond which can be called actually pure or crystallized 

 carbon. As wood charcoal, it is derived from willow, pine 

 box and several other woods, burned under cover so as 

 to prevent free access of air, and its manufacture is of 

 great commercial importance, kilns for its creation ex- 

 isting in thousands of places throughout the United 

 States, where forests abound and wood is in plenty. It 

 should be borne in mind that this carbon, or wood char- 

 coal, is an essential element of the plant, inasmuch as it 

 comes out of it by burning. Moreover, it is all manufac- 

 tured in the plant, extracted as part of its food from the 

 soil, or the air. 



Heated in air, charcoal, or carbon, as we shall call it 

 hereafter, burns with little flame, and is slowly consumed, 

 leaving only a white ash, the rest of the carbon disappear- 

 ing in the air. It is not lost, however, for by the burning 

 it is converted into a gas which goes by the name of "car- 

 bonic acid," which ascends and mingles with the at- 

 mosphere, to be again absorbed by plants to manufacture 

 more carbon, or, rather, a fresh supply of charcoal. This 

 carbonic acid gas is deadly, speedily causing death if 

 breathed. 



Carbon is light and porous and floats on water, but 

 plumbago or black lead, and the diamond, which are only 

 other forms of carbon, are heavy and dense. Both black 

 lead and the diamond, when burned in the air at a high 

 temperature, leave only a very little white ash, the rest 

 being converted into carbonic acid and disappearing in 

 the air like the common charcoal. 



Of this carbon, all vegetable substances contain a 

 very large proportion. It forms from 40 to 50 per centum 

 by weight of all parts of dried plants cultivated for the 

 food of animals or man, and the part it performs in the 

 economy of nature is therefore very important. 



Light, porous charcoals possess several notable prop- 

 erties in plant culture: 



First They absorb into their pores large quantities 

 of gaseous substances and vapors which exist in the at- 

 mosphere. Thus: They absorb over ninety times their 

 bulk of ammonia; fifty-five times their bulk of sulphuretted 

 hydrogen; nine times their bulk of oxygen; nearly twice 

 their bulk of hydrogen, and obsorb sufficient aqueous 

 vapor to increase their weight from ten to twenty per 

 centum. 



Second They separate from water, decayed animal 

 matters and coloring substances which it may hold in 

 solution. In the soil they absorb from rain, or flowing 

 water, organized matters of various kinds, and yield them 

 up to the plants growing near to contribute to their 

 growth. 



Third They absorb disagreeable odors and keep ani- 

 mal and vegetable matter sweet when in contact with it. 

 For which reason vegetable substances containing much 

 water, like potatoes, turnips, etc., are better preserved by 

 the aid of a quantity of charcoal. 



Fourth They extract from water a portion of the 



saline substances, or salts, it may happen to have in solu- 

 tion, and allow it to escape in a less impure form. The 

 decayed (half carbonized) roots of grass, which have been 

 long subjected to irrigation, may act in one or all of these 

 ways, or the more or less impure water with which they 

 are irrigated, and thus gradually arrest and collect the 

 materials fitted to promote the growth of the coming crop. 



Oxygen. 



We know oxygen only in its gaseous or aeriform 

 state, although it may be liquefied and even converted 

 into a solid form under the name of "liquid air." As a 

 gas it is invisible and possesses neither color, taste nor 

 smell. When inhaled in a pure state it is stimulating 

 and exciting to the vital functions,, but used in excess it 

 causes death. Plants refuse to grow in pure oxygen gas 

 and speedily perish. 



It exists in the atmosphere in the proportion of 21 

 per centum of the bulk of the latter, and in this state and 

 proportion it is necessary to the existence of animals and 

 plants, and to permit combustion everywhere on the globe. 

 The amount of it in water will surprise many readers, for 

 every nine pounds of water contains eight pounds of oxy- 

 gen. A knowledge of this fact will cause the full value 

 of water as an essential to plant growth to be appreciated. 

 Moreover, water possesses the power of absorbing still 

 more oxygen from the atmosphere than it contains nat- 

 urally. Thus, water will absorb from three and one-half 

 to six and one-half parts of oxygen to one hundred parts 

 of water. Rain, spring and river waters always contain 

 an additional proportion of oxygen, which they have ab- 

 sorbed from the atmosphere. This is taken up in the soil, 

 for, as the water trickles through the soil, it surrenders 

 the oxygen to the plants with which it comes in contact, 

 and ministers to their growth and nourishment in various 

 ways to be hereafter explained. 



But the quantity of oxygen stored in solid rocks is 

 still more remarkable. Nearly one-half of the rocks which 

 compose the crust of the earth, of every solid substance 

 we see around us, of the soils which are daily cultivated, 

 and much more than one-half of the weight of living 

 plants and animals, consist of this elementary body, oxy- 

 gen, known to us only as an invisible, imponderable, un- 

 perceivable gas. 



Hydrogen. 



Hydrogen is also known to us in the state of gas, and 

 like oxygen is without color, taste or smell. It is un- 

 known in a free or simple state, although chemists have 

 succeeded in obtaining it in small quantities, and is not 

 so abundant as either carbon or oxygen. It forms a small 

 percentage of the weight of animal and vegetable sub- 

 stances, and constitutes only one-ninth of the weight of 

 water. With the exception of coal and mineral oils, 

 known as "hydro-carbons," it is not a constituent of any 

 of the large mineral masses of the globe. 



It does not support life, and animals and plants in- 

 troduced into it speedily die. It is the lightest of all 

 known substances, being fourteen and one-half times 

 lighter than air. Water absorbs it in very small quantities, 

 one hundred gallons of water taking up no more than 

 one and one-half gallons of it. 



Nitrogen. 



This substance is likewise known only in a state of 

 gas. It exists in the atmosphere in the proportion of 

 79 per centum of its entire bulk, and is without color, taste 

 or smell. It is lighter than atmospheric air in the propor- 

 tion of 97J/2 to 100, and is deadly in its pure state to both 

 animals and plants. It is essential in the atmosphere we 

 breathe, moderating the combustion which would ensue 

 if the air were pure oxygen, and forms a part of many 

 animal and some vegetable substances, but does not enter, 

 except in small proportions, into mineral masses. It is 

 less abundant than any of the so-called organic elements, 

 but it performs certain most important functions in refer- 

 ence to the growth of plants. Spring and rain water ab- 

 sorb it as they do oxygen, from the atmosphere, and bear 

 it in solution to the roots of plants, one hundred parts of 

 water dissolving about one and one-half to four per centum 

 of the gas. 



