THE RAISIN INDUSTRY. 85 



attained : absence of distribution ditches, which take up valuable 

 land and which cost money to keep clean from weeds ; less growth 

 of weeds on the surface of the ground ; greater mellowness of the top 

 soil and less work in plowing generally ; a greater and more uniform 

 supply of moisture, which, instead of being near the top of the ground, 

 is accumulated deeper down, thus causing the roots to go down instead 

 of spreading near the surface ; no expensive irrigation, which will 

 require plowing every time after the water is spread on the surface; 

 a greater coolness of the ground and a lower temperature generally, 

 which shows itself in a more vigorous growth of the vines, a greater 

 supply of grapes and less danger from sunburn. These and many 

 more are the advantages of subirrigation and seepage combined. To 

 attain them in a raisin vineyard, no labor and reasonable cost should 

 be spared. 



Drainage. Drainage is necessary in all vineyards where large quan- 

 tities of water are used for irrigation, and principally at the very time 

 that subirrigation begins. Thus in Fresno county the best raisin vine- 

 yards are those in which the land is both subirrigated and drained. 

 When irrigation commences in any certain district, no one thinks of 

 drainage as a possibility, and great carelessness is shown in locating 

 ditches and other irrigation works. But in a few years, when the soil 

 is full of water which finds no outlet, drainage becomes both necessary 

 and desirable. A very successful and highly necessary drain has been 

 constructed through a part of the Fresno district, which so filled up 

 with water during the rainy winter of 1883-84 that much of the 

 ground could not be plowed until late in the spring. The drain 

 remedied the evil and drained the soil, and the vineyards grown there 

 are now counted among the best and most profitable. The water thus 

 drained off lowered the water level from six to seven feet. In very dry 

 seasons this ditch is filled with water, and serves then to keep the 

 soil moist through seepage or subirrigation. 



The Influence of Irrigation on the Soil. It is by many considered 

 that irrigation helps to fertilize the soil. The spring and flood water 

 contain great quantities of mud and humus, which when spread over 

 the land will greatly increase its. fertility. Even ordinary river water 

 contains salts and other ingredients, which will fertilize the soil to no 

 small degree. Another cause of the increased fertility of subirrigated 

 soils is that the water which constantly evaporates carries with it 

 salts, etc. , from the lower strata up towards the surface, and makes 

 them accessible to the roots of the vines. But, on the other hand, if 

 the water or the soils contain alkalies or other destructive substances, 

 these also are deposited on the surface to the great detriment of the 

 vines, and often to such an extent that the vines will, die or become 

 sickly. Too abundant flooding may also leach out of the soil its 

 soluble salts, and carry them deeper down in the ground. But if this 

 soil after a while fills up with water and becomes subirrigated, the 

 evaporation of water from the surface will gradually carry these salts 

 back to the surface, when they will increase the fertility of the soil. 

 Where drainage is very perfect, constant irrigation will gradually rob 

 the soil of many of its soluble salts, and carry them to places where 



