THE IRRIGATION AGE. 



245 



FURROW IRRIGATION. 



Applied to cultivated land, furrow irrigation is 

 allied to infiltration. Eunning water into furrows be- 

 tween the rows of plants and then cultivating over is a 

 very common method of irrigation by infiltration, and 

 is suitable for all shallow rooted plants, corn, potatoes, 

 and tubers generally. The after cultivation by which 

 the surface soil is pulverized, forms a mulch which re- 

 tains the moisture below for a long period. It is also 

 adopted on a large scale in orchards, vineyards, and 

 nurseries ; for small fruits, vegetable and flower gardens, 

 wherever, in fact, deep irrigation or sub-irrigation, 

 flooding, or flowing would be useless, or inefficient. It 

 is well to provide that the water or surface wet be pre- 

 vented from spreading as far as the stalks or bodies 

 of the plants, for that means rotting, restricting it to the 

 service of the roots. This renders this method of irriga- 

 tion more efficacious than direct irrigation for the reason 

 that the humidity is imprisoned around the roots where 

 it is needed and evaporation retarded. 



It is in the kitchen garden that infiltration attains 

 marvelous results, particularly in the culture of root 

 plants. In fact, it is the only system of irrigation which 

 enables plants to obtain the greatest quantity of nutritive 

 elements from a given surface. The soil is never at 

 rest, and where the climate is favorable, one crop after 

 another may be grown all the year around, and even in 

 climates where the farmer is satisfied with one crop each 

 season he may easily raise two. It is the equivalent to 

 hothouse culture so far as growth is concerned, but the 

 plants possess a quality unknown to forced cultivation. 



WINTER IRRIGATION. 



Infiltration or sub-irrigation is an admirable system 

 for what is known as "winter irrigation," when the water 

 supply is more abundant than is the case in the dry 

 or growing season in humid climates. Water is run 

 into the underground conduits to fill the soil with mois- 

 ture, and then by the further storing up of the water in 

 excess, surface irrigation becomes practicable when it 

 comes to planting, and plants are supplied with moisture 

 until their first true leaves are formed, by which time 

 their roots are in moisture laden soil and they grow to 

 maturity with very little after irrigation, unless shallow 

 rooted, in which case surface irrigation is always necessary. 



There are three atmospheric and meteorological 

 conditions which should be considered under the name 

 of winter: In the arid and semi-arid regions of the 

 South and Southwest and on the Pacific slope, where 

 the Kuro Siwa or Japanese ocean current creates a per- 

 petual spring climate, what is known as the winter sea- 

 son is the growing period generally for cereals and gar- 

 den products it is the "wet season." If there be any 

 rainfall at all it begins about November and ends in 

 April. Sometimes the rainfall is not more than five 

 or ten inches, perhaps fifteen inches, an amount so 

 small to a farmer in the humid regions that he would 

 not venture to move a plow, but eight inches is con- 

 sidered sufficient to raise a reasonable crop without 

 irrigation, provided there is constant cultivation. In 

 such regions every drop of water is utilized and care 

 taken to prevent evaporation. 



In such a climate the farmer dry plants, that is, 

 he puts his seed into the ground when the latter is as 

 dry as powder, plowing it up previously or plowing his 

 seed under. There being no moisture of course it does 

 not sprout, but lies in the soil as safely as in his barn 



bin. But when the first rain comes, perhaps only half 

 an inch, his seed is up in a few days, and then begins 

 cultivation to prevent evaporation. This is continued 

 during the entire season, after every shower, large or 

 small, so that his crop matures very well on eight inches 

 of water from the clouds, aided, however, by dews and 

 mists, which, as has been said in a former chapter, is 

 quite considerable. 



Here winter irrigation is of the most incalculable 

 benefit for the deciduous plants which spring into life 

 in March and April, small fruits, orchards and the 

 like, for it fills the soil with moisture, and when a trifle 

 of surface irrigation is added the plants continue grow- 

 ing with profusion and produce profitable crops. 



In the totally arid regions where there is no rain- 

 fall at all, nothing but aggravation mists, or heavy, foggy 

 dews, nothing can be grown without irrigation of some 

 kind, and experience has demonstrated that surface ir- 

 rigation can not very well be performed unless there is 

 an ocean of water at hand to be wasted in evaporation, 

 for the climate is usually hot. Now, if the soil can be 

 moistened by infiltration through subterranean conduits, 

 that moisture will remain in the soil for an indefinite 

 period and may be added to by subsequent irrigations. 

 The fact is, that this system of sub-irrigation furnishes 

 an artificial water table which provides capillary attrac- 

 tion something upon which to operate. 



The same results may be attained by running water 

 into deep open furrows, care being taken to cultivate 

 over immediately, and then infiltration or seepage will 

 begin operating, and whatever excess there may be will 

 find its way into the soil in all directions, from a higher 

 field to a lower one, and from one slope to another, for 

 instance. 



The second climatic condition is where the region is 

 cold and frosty, precluding winter growth, and without 

 very much snow or other precipitated moisture. Here 

 sub-irrigation prepares the soil for spring cultivation, 

 and sufficient water- is retained for surface irrigation 

 when needed. It should be observed that constant and 

 deep soil cultivation is as much necessary in such a 

 region as in an arid or semi-arid one, the rule being 

 that the roots of plants must be provided with adequate 

 moisture regardless of surface conditions. 



The third condition of climate is where the rains 

 and snows of winter are comparatively heavy, equal to 

 the rainfall in the sub-humid sections, but the cold is 

 too great to permit any sort of plant life. In such 

 case winter irrigation is as much of a necessity as in 

 the arid and semi-arid regions because the necessities 

 are the same. There is a cessation of water precipita- 

 tion in the spring of the year, or else the precipitation 

 during the growing season is not sufficient to mature 

 a crop, hence there must be water enough stored up in 

 the soil to meet the coming drought. 



IRRIGATION BY SPRINKLING. 



Water sprinkling is practically artificial rain in a 

 small way. In an arid climate it is of trifling advantage 

 unless other means of irrigating are employed, or unless 

 there is a thick growth of vegetation which shades the 

 ground, or "mats," as in the case of strawberries, etc. 

 It is adapted to garden culture, however, and in horti- 

 cultural cultivation generally it is of the highest excel- 

 lence. Where water can be conveyed in pipes, with 

 hydrants placed at intervals to admit of hose attach- 

 ments, there is no better system of irrigation, though 



