IRRIGATION AND DRAINAGE. 79 



jure garden vegetables, therefore underdrainage of the 

 orchard is a different proposition from that of the garden. 

 It should be stated for the distant reader that the term 

 "garden" in California is not understood to include fruit 

 trees, except in villages or suburban places. 



The growing season of the vegetable crop is also re- 

 lated to the matter of underdrainage. While the winter 

 garden on a retentive soil in a region of quite large rain- 

 fall, may be greatly improved by underdrainage, the sum- 

 mer growth of the same plants perhaps, and of field crops 

 of shallow-rooting vegetables, may be benefited by such 

 surface treatment during the winter as shall promote the 

 absorption and retention of the whole rainfall to the soil 

 and subsoil. This practice may insure the perfection of 

 a crop without irrigation which could not be grown on 

 a less retentive soil nor on one currently drained on its 

 surplus water. 



The practice of irrigation may create a need for under- 

 drainage which may not exist on land used for rainfall- 

 gardening. If the soil is naturally well drained this need 

 will not, however, occur, unless the natural escape of sur- 

 plus water has been destroyed by rise of the bottom water 

 which has, in some large districts in California, followed 

 excessive irrigation, and the seepage of water from leaky 

 ditches. Especially unfortunate, too, has it been that this 

 rise of the ground water has brought within reach of cap- 

 illary action and surface evaporation alkaline salts which 

 are destructive to vegetation. But here again the growth 

 of vegetables can be successfully pursued on lands with 

 water too near the surface to favor fruit trees, providing 

 the rise of alkali does not occur. For the growth of vege- 

 tables, then, it is not generally imperative that the land 

 be underdrained, even if irrigation is practiced, though 

 there are cases of retentive soils in which this is desirable. 

 In irrigation in a humid climate where a heavy downfall 

 of rain may immediately follow a saturation by irrigation, 



