172 



THE IKKIGATION AGE. 



PRIMER OF IRRIGATION. 



BY D. H. ANDERSON. 

 COPYRIOHT, 1903, BY D. H. ANDERSON. 



CHAPTER I. 



SOIL IN GENERAL ITS FORMATION, CHARACTERISTICS 

 AND USES FERTILITY AND STERILITY. 



The mere planting of a seed in the ground is not 

 sufficient to insure its growth, or development into a 

 useful or profitable plant. This fact is well known to 

 everybody, but what is not so well known is, the reason 

 or cause why a seed grows up into a vigorous plant cap- 

 able of reproducing seed similar to the one from which 

 i ! ' sprang, and how it does it. 



There are certain elements which are essential to 

 the growth of every plant, the development of every 

 germ, for without them it cannot live; these are heat, 

 light, air and moisture. A few grains of wheat dis- 

 covered in the coffin of an Egyptian mummy after 

 three or four thousands years' deprivation of the four 

 essential elements, were found inert, that is, they were 

 not alive, neither were they dead, for upon giving them 

 the essentials above referred to, the wheat sprang into 

 life and produced a plentiful supply of grain. 



PLANTS ARE LIKE ANIMALS. 



Still, notwithstanding the necessity of heat, light, 

 air and moisture, plants cannot flourish without proper 

 food. In this respect plants are similar to animals. 

 Among animals there is no universal specified diet, 

 some eating one kind of food, others another. We see 

 many that eat flesh exclusively, others whose sole diet is 

 insects. Certain animals eat herbs and grass, others 

 grain, and when we reach man we find an animal that 

 will eat anything and everything, hence we call man 

 "omnivorous." 



It is the same with plants, some devouring in their 

 fashion a certain kind of food, some another, and so on 

 all along the list. Plants are substantially like animals 

 that possess a stomach, they eat and digest, absorb and 

 assimilate the food they obtain. If the plant is not 

 furnished with its proper food, or if it is prevented 

 from obtaining it, it shrivels, droops, withers and dies 

 just like an animal that starves to death. 



There is another striking resemblance between 

 plants and animals, which is the instinct and power to 

 seek food. The plant being a fixture in the soil, can- 

 not of course, "prowl" about in search of food, but it 

 throws out roots, fibres and filaments in every direc- 

 tion, its instincts reaching in the direction of food as 

 surely and with as much certainty as the nose of an 

 animal scents its prey, or the eye of an eagle sees its 

 quarry. Not only does the plant seek food beneath the 

 surface of the earth, but it thrusts shoots, branches and 

 leaves up into the atmosphere for the purpose of ex- 

 tracting nourishment there also. 



It is, however, from the soil that plants receive the 

 principal supply of food necessary for their develop- 

 ment, hence an acquaintance with its chemical and 

 physical properties is important in helping us to under- 

 stand the nutritive processes of plants, and the operations 

 of agriculture. 



Volumes of books have been written on the general 

 subject of agriculture, but they are more adapted to 

 soils upon which falls sufficient rain to dissolve the salts 

 necessary to produce a crop. In a book devoted to irri- 



gation, the principles of agriculture and the adaptation 

 of the various elements of plant food in the soil, are 

 all the more important as the water employed in irri- 

 gation which is nothing but artificial rain is abso- 

 lutely within the control of man, and not dependent 

 upon meteorological uncertainties. One fact should, 

 however, be constantly borne in mind by the practical 

 irrigator, that pure water is absolutely sterile so far as 

 plant food is concerned, and if poured upon a pure 

 soil, which is also sterile, there can be no crop of any 

 sort raised. A remedy for supplying a defect of plant 

 food in irrigating water will be given in detail in 

 another chapter, the scope of this chapter being limited 

 to soils that contain plant food, or are arable, in which 

 case the quality of the water is of secondary importance. 



ORIGIN OF ARABLE SOIL. 



Arable soil owes its formation to the disintegra- 

 tion of minerals and rocks, brought about by mechanical 

 and chemical agencies. The rock may be said to stand 

 in about the same relation to the arable soil resulting 

 from its disintegration as the wood or vegetable fibre 

 stands to what is called the humus resulting from its 

 decay. To be fertile, however, the soil must contain 

 disintegrated vegetable matter. There is no fertility 

 in a heap of sawdust, nor is there in a heap of powdered 

 rock; indeed, the two might be combined and still re- 

 main sterile, it is only after both have been disinte- 

 grated by chemical or mechanical action that they be- 

 come plant foods capable of nourishing and maintaining 

 plant life. 



From this it results that soil consists of two grand 

 divisions of elements: inorganic and organic. The 

 inorganic are wholly mineral, they are the products of 

 the chemical action of the metallic, or unmetallic ele- 

 ments of rocks. They existed before plants or animals. 

 Life has not called them into existence, nor created 

 them out of simple elements. Yet these inorganic min- 

 eral elements of soil become part of plants, and under 

 the influence of the principle of life they no longer 

 obey chemical laws, but are parts of a living structure. 

 Through the operation of the laws of the life of the 

 plant, these mineral elements become organic and so- 

 continue until death comes and decay begins, when 

 they return to their mineral form. 



Organic elements are the products of substances 

 once endowed with life. This power influences the ele- 

 ments, recombines them in forms so essentially con- 

 nected with life that they are, with few exceptions, pro- 

 duced only by a living process. They are the products of 

 living organs, hence termed organic,' and when formed, 

 are subject to chemical laws. The number of elements 

 in the inorganic parts of soil is twelve : Oxygen, sul- 

 phur, phosphorus, carbon, silicon and the metals : potas- 

 sium, sodium, calcium, aluminium, magnesium, iron 

 and manganese. 



The number of elements in the organic parts of 

 soil does not exceed four: Oxygen, hydrogen, carbon 

 and nitrogen. 



The great difference between these two divisions 

 is, that while the inorganic elements are combinations 

 of two elementary substances, the organic are com- 

 binations of three or four elements, but never less than 

 two. These three elements, however, are variously 

 combined with the other elements to form salts which 

 enter into the great body of vegetable products, in fact 

 they are continually changing, the mere change of one- 

 element, or its abstraction forming a new product. It 



