THE IKKIGATION AGE. 



149 



of percolation the water is run directly over and upon 

 the soil after the manner of flooding. The land is not 

 sloped but is flat, or level, a small How, however. !>eing 

 desirable rather than objectionable. Jt is adapted to 

 very light and unretentive soils and for shallow root- 

 ing plants like strawberries. 



The land is laid out in rectangular checks, or any 

 other desired form, and around the sides of the checks 

 are elevated ridges upon the top of which are laid 

 ditches in which the water flows slowly and quietly. 

 The water is admitted to the checks from several 

 points at the same time and distributes itself over the 

 surface uniformly, slowly soaking into the soil. 



In the hot summer months when it is desirable to 

 maintain the growth of shallow rooted plants, it is 

 an admirable system, and is enhanced in its effects by 

 spreading over the soil a mulch of rotten straw, or 

 coarse manure under which, protected from the sun, 

 the water slowly spreads with very little evaporation. 

 It possesses more beneficial aspects than mulching and 

 sprinkling, for the reason that the water is retarded by 

 the presence of the mulch from reaching the roots of 

 the plants, where it is needed, and evaporation is much 

 more rapid. 



For the hot, dry season, where there is no danger 

 of over-saturating the soil, the depressed bed is avail- 

 able for all kinds of vegetables, small fruits and flow- 

 ers, the use of it showing marvelous results. 



The system is in common use in Europe, where 

 the heat is not excessive, and where a light sandy soil 

 is under cultivation. It is the system adopted by the 

 market gardeners in the sand hills south of the city of 

 San Francisco, where the vegetable gardeners have 

 transformed large areas of apparently worthless land 

 into terraces, and on these have arranged depressed 

 beds in which enormous quantities of succulent vege- 

 tables are grown for the city market. The water is 

 raised by windmills and pumps from wells sunk in low 

 spots, and delivered to small flumes which run from 

 the windmill towers to the opposite hillsides. The 

 water is flowed upon the highest terrace and conveyed 

 thence by means of troughs and small ridge ditches 

 from terrace to terrace and all the beds filled. 



In all cases of surface or ditch irrigation the land 

 must be laid ,out to suit the flow of the water, which is 

 necessarily down hill, so to speak. If the land is not 

 smooth on a level or. slope, it must be leveled or 

 graded by means of a scraper or other device for re- 

 moving uneven portions and hillocks. If the land is 

 too uneven to be irrigated uniformly, then sub-irriga- 

 tion is the only remedy, or piping water to the tops of 

 the ridges, or by establishing a reservoir on the highest 

 spot, and thence running ditches in every direction 

 after tracing or laying out the courses with the leveler 

 as related in another and previous chapter. 



As much care must be taken proportionately in 

 field culture as in the case of small kitchen gardens, 

 the principle being the same. 



To put land in shape to irrigate it should first be 

 plowed as deep as possible and then cut into heds of a 

 larger or smaller size, depending upon the quantity of 

 land to be irrigated and the amount of water at the 

 disposal of the farmer. This may be done by means 

 of a drag constructed in the shape of the letter A, 

 from eight to twelve feet and more at the bottom, run- 

 ning to a point at the top. The land is dragged by 

 drawing the A-shaped contrivance point first across 

 the field from side to side. The wide spreading ends 



of the drag gather in the loose earth, clods and other 

 rough material and heap them up behind in the shape 

 of a ridge. These beds may be made from sixteen to 

 eighty feet -wide and ten 'to forty rods long; it all 

 depends upon the quantity of water at hand to fill 

 them. 



After the field has been laid off into beds, the 

 ground between the ridges must be leveled if uneven 

 or humpy, and for this purpose a scraper will be serv- 

 iceable. By it the humps should be scraped into the 

 low places, and then a harrow may be used and the 

 leveling process finished with a board leveler, well 

 weighted down. This is nothing more than a strong 

 thick plank weighted with stones and dragged back 

 and forth over the beds until they are in a perfect con- 

 dition to receive water uniformly upon the surface. 

 The ends of the beds should come up close to the main 

 ditch, or to the large lateral ditch, so that the water 

 can be turned on in full volume. These beds may be 

 irrigated one after the other by flooding, or by furrow 

 irrigation. Indeed, there is no limit to the manner 

 of irrigating, the great desideratum being to spread 

 the water uniformly over the entire bed. It will be per- 

 ceived that the system is similar to that of the smaller 

 depressed bed-irrigation, except that the ridge ditches 

 are not used, the ridges around the large beds being 

 used to retain the water and to mark out the land in 

 such shape and sized plats as to correspond with the 

 quantity of water on hand. The flow of water must 

 be sufficient so that it will rapidly cover the bed, and 

 if that is deficient then the beds must be made smaller,, 

 otherwise the plants at the upper end of the bed will 

 flourish and produce well, whereas those at the lower 

 end will be sickly and produce little if anything. This 

 often happens in the case of corn, potatoes, etc., when 

 the water runs either too rapidly or too slowly into the 

 furrows. The slope of the land should be such as to 

 provide a quick rush of water all along the line, and 

 its standing in the furrows to slowly soak into the 

 soil. For this purpose the source of the water supply 

 must be considerably higher than the land to- be irri- 

 gated, and the quantity delivered large enough to fill 

 quickly. Too slow a flow and too small a quantity will 

 soak the upper end of the bed and give the lower part 

 too little. 



One important thing to be guarded against in 

 laying out the land for irrigation is to avoid the wash- 

 ing out of the soil by the action of the flowing water. 

 Inasmuch as the land irrigated is always under culti- 

 vation and loosely put together after the action of the 

 plow, it is very easily washed into gullies, and every 

 gully means a lessening of fertility. There is not so 

 much danger in this respect when the land is covered 

 with a heavy crop and flooded, because then, the plants 

 will retard the rush of water and prevent damage by 

 washing. But in furrow irrigation, the furrow soon 

 may become a deep gully which the plow and cultivator 

 can not remove, and every subsequent application of 

 water will enlarge. To obviate this it is good farm- 

 ing to make the furrows short by damming with a 

 quantity of earth, and when one furrow the first one 

 is well filled, remove the temporary dam and let the 

 water flow down into another short furrow. This will 

 be the opening up of a succession of reservoirs which, 

 being small, will ' not be liable to cause any damage, 

 and will permit a speedy watering of the entire row of 

 plants. 



