THE RAISIN INDUSTRY. 83 



Subirrigation. Subirrigation may be either artificial or natural. 

 The artificial Subirrigation has, as far as I know, only been used in a 

 few vineyards in Yolo and Solano counties, the report, shortly after it 

 had been established, being very flattering as regards its success. But 

 of late years we have heard nothing about this kind of irrigation, and 

 it is likely that some practical difficulty was encountered which could 

 not be fully overcome. The artificial Subirrigation consists in laying 

 larger and smaller cement pipes between the rows of the vines. These 

 pipes are perforated in various places, and, when filled with water 

 under pressure, the water runs through the perforated holes and keeps 

 the ground outside the pipes constantly moist, without causing the 

 surface of the soil to get wet and weedy, and herein consist the princi- 

 pal advantages of the system, as well as in the fact that rolling ground 

 can be irrigated thus without being previously leveled and without 

 being cut up with open ditches. The difficulty of keeping the holes 

 open and of preventing the roots of the vines from entering the pipes 

 is, I understand, very great and probably impossible to overcome. 

 Both irrigation water and liquid manures could by this system be 

 supplied to the roots of the vines directly without any waste, and, in 

 cases of diseases or attacks by underground pests, medicines or insecti- 

 cides could be brought to the soil with the least possible cost. 



The natural Subirrigation is caused either by the whole soil filling 

 up with water from the natural and original water level to the very 

 top or to the roots of the vines, or from an impervious hardpan or 

 clay, as subsoil, up towards the surface. As an example of the former 

 we might cite the country around the irrigated plains of the San 

 Joaquin valley, especially around Fresno and in Mussel Slough. Be- 

 fore irrigation was begun there in 1872, the surface water was from 

 sixty to seventy feet from the top east of the railroad, and from forty 

 to fifty feet west of the railroad, lower down in the valley. After five 

 years of irrigation it began to be noticed that the soil required less 

 water. The water in the wells began to rise, and the following year 

 the water stood in many places near or on the top of the surface. 

 Now the whole irrigated district ground Fresno has filled up with 

 water to such an extent that drainage ditches have become necessary 

 in some places in order to lower the water in the wet season some four 

 or five feet from the surface. Many more drainage ditches will be 

 required, as in wet winters the surface water in places is not only very 

 near the top, but actually forms ponds or swamps where formerly the 

 ground was entirely dry. 



In the old irrigated districts, water can now be found at from six to 

 ten feet in the driest season, while formerly the wells had to be from 

 fifty to seventy feet deep. In the older vineyards, and even in many 

 of the younger ones, no more surface irrigation is used; all that is now 

 required is to allow the water to run in the main ditches, in which the 

 water sinks sufficiently to keep up the supply of the evaporation of 

 the ground outside. Large tracts of land which have never been sur- 

 face irrigated are now sufficiently moist to grow vines to the greatest 

 perfection, and many of the best vineyards have never been irrigated 

 at all; in fact, nothing but drainage ditches have ever been made on 



