THE IEEIGATIOK AGE. 



335 



It is not safe, however, to rely upon thirteen and 

 one-third inches of rainfall during the growing sea- 

 son. Farmers know to their cost that then the rain 

 possesses a very retiring disposition, and the skies are 

 brazen for long periods, long enough, sometimes, to 

 either ruin the crops or to stunt them and produce only 

 a small percentage of what was expected from their 

 early start and growth. In other words, the growing 

 season is also the season of drouths, except in those re- 

 gions where winter is the growing season, there being 

 no frosts to retard vegetation. Yet, strange to say, even 

 with all the uncertainties of summer moisture good 

 crops are sometimes grown and that on a small per- 

 centage of the annual rainfall. With irrigation sup- 

 plying the deficiency of rainfall there is a certainty of 

 a good, profitable crop every year. 



What has been said thus far relates to land which 

 contains natural moisture or a water table, a supply 

 of water which is brought up to the surface by capillary 

 action or by accretions from heavy rains, and where the 

 soil is wet enough to require a system of drainage to 

 carry off the surplus. It is easy to perceive that under 

 such conditions plants will draw moisture from below 

 by means of their tap roots and thus supply themselves 

 with plant food to make up for any deficiency of pre- 

 cipitation. Where those conditions prevail, irrigation 

 becomes supplemental and is not only useful but es- 

 sential in the humid regions to overcome the possible 

 damage likely to occur during the period of drouths. 

 To dose the soil with water having a water table near 

 enough the surface for the tap roots of plants to reach 

 would be a waste and of no benefit to plant life, as 

 will be readily believed when it is understood that too 

 much water is as detrimental to plant life as too little. 



Where there is moisture in the subsoil, and even a 

 modicum of rainfall during the summer months, the 

 author would suggest that if the deficiency amounts to 

 six inches, or four inches, or thirteen inches, such de- 

 ficiency be made good by an artificial application of 

 water at regular intervals, one surely just at the period 

 of flowering and the last one just before the ripening 

 of the fruit, or at the period when they are said to be 

 "in the milk." At that time a chemical transforma- 

 tion is taking place in the economy of the plant, and 

 it must be supplied with the material to continue it, 

 else it will shrivel and die of old age before ripen- 

 ing. 



The same observations may be adapted to those 

 semi-arid regions where the frosts of winter prevent the 

 existence of plant life, and the rainless summers de- 

 mand irrigation as necessary to raise a crop of any kind. 

 There are fall rains and winter snows, and by keeping 

 the ground open to their reception the moisture can be 

 retained for a long enough period to start the infant 

 plant well on its way in the spring, but after the first 

 true leaves are formed irrigation must begin and con- 

 tinue during the growing period, for there is no rainfall 

 to be depended upon as an aid to agriculture. Under 

 such conditions plants do not require any more moisture 

 than in any other region, and hence it is stated as a 

 broad proposition that the same quantity of moisture 

 that will raise a crop in the humid regions will also 

 raise one in the semi-arid districts, where winter is a 

 bar to winter growth. 



In what are designated as "arid and semi-arid" re- 

 gions, with a semi-tropical climate, although there is 

 very little rainfall, it is surprising how far the small 

 precipitation will go toward maturing a crop without 



the assistance of artificial applications of water. Five 

 inches will raise a crop planted in dry ground before the 

 rains come, and by careful and continual cultivation of 

 the ground that crop will be profitable enough to make 

 it worth while to plant. In favorable soil one inch of 

 water will wet the ground down about eighteen inches or 

 two feet,, and the first rain penetrating to the seed that 

 has been plowed under "dry" will cause it to sprout 

 within three or four days. From that time on until the 

 crop matures, in March or April, if the rain begins in 

 December or January, the farmer cultivates plants that 

 can be cultivated and harrows his wheat and barley to 

 keep the soil open as much as possible. There may not 

 be any moisture in the subsoil on the contrary it may 

 be as "dry as a bone" for a hundred feet down but 

 the crop grows, and with few inches of rain it reaches 

 maturity. Of course, it is not luxuriant vegetation, 

 .nor is the wheat and barley as high as a man's head. 

 But it produces enough for his stock and his vegeta- 

 bles, unless sugar beets and deep-rooting plants fur- 

 nish him with a good supply. Some of these "dry 

 farmers" say they are satisfied with eight inches of 

 rainfall and consider fourteen inches a "wash out." In 

 such regions the summer months, from May to No- 

 vember, and sometimes into December, the skies are 

 iloudless and not a particle of rain falls. Then irriga- 

 tion is an absolute necessity, and it is practiced so as 

 to continue the growing season all the year round and 

 to produce a succession of crops without any cessation. 

 There is undoubtedly more evaporation from the soil 

 than in the humid regions, but that is diminished by 

 deep cultivation and pulverization of the soil. Plants, 

 however, do not require any more moisture than in any 

 other region, and when the quantity consumed by the 

 plant during its period of growth is carefully gauged 

 that is the amount of water to give the soil, with 

 about 25 per cent added to the account of evapora- 

 tion. 



After all is said the quantity of water to be given 

 the soil artificially is governed, in a great measure, by 

 the nature of the soil. In Chapter V, "Eelations of 

 Water to the Soil," this subject is treated and the 

 reader is referred to that chapter for the facts and 

 figures. There is one axiomatic proposition which is 

 here repeated in this connection because it is the key 

 to the whole matter : "The more water the soil contains 

 in its pores the greater the evaporation." Plants are 

 like the hum'an body gorge it, even with the most nour- 

 ishing foods, and it becomes sick ; give it too little to 

 keep iip its system and it becomes anasmic. With just 

 enough, an equilibrium is maintained and health is se- 

 cured as a matter of course. This idea is what the 

 author seeks to convey in calling attention to the fact 

 that what a plant needs is the amount of provision 

 to rriake for it; all beyond that is superfluous, a waste 

 of material, not productive of any beneficial results. 



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 1 year, and The Primer of Irrigation 



