154 THE IREIGA Tl ON A GE. 



despite what was considered abundant irrigation, i. e., allowing the 

 water to run for a given length of time, deemed to be sufficient. Yet 

 on being called in to investigate the causes of the trouble, the station 

 staff found that the irrigation water had failed to penetrate during the 

 alloted time to any beneficial extent, so that the trees were, in the 

 main, suffering from lack of moisture a fact that could have been 

 verified by any one of the owners concerned, by simply boring or dig- 

 ging a hole or two. But no one had thought of doing so, and all kinds 

 of mysterious causes were conjectured to be at work in the suffering 

 orchards. A definite knowledge of the rapidity with which irrigation 

 water penetrates downward and sideways in his soil should form a 

 part of the mental equipment of every irrigator, particularly in ar- 

 ranging his head ditches. For in sandy lands it may easily happen 

 that when these are too far apart, the water near the head ditch is 

 already wasting into the country drainage at the depth of ten or twelve 

 feet, before any has reached the end of the furrows, or has wetted the 

 lower half adequately. Many such cases come under our observation, 

 and such ignorance of the conditions governing one of the most im- 

 portant factors of success is hardly excusable in any one. Nor is the 

 quality of the water used indifferent in this connection; for waters 

 containing alkali will fail to penetrate the soil as quickly as would 

 ordinary stream waters. 



Preventing evaporation. But supposing the moisture to have 

 reached the depths of the soil, whether from rains or from irrigation, 

 it is essential that proper means be employed for retaining it in the 

 land, and especially to prevent evaporation. That this is best accom- 

 plished by a mulch on the surface, and that the best mulch for the 

 purpose, which need not be hurled on or off and is always ready, is a 

 surface layer of loose, well-tiled soil, is now pretty well understood 

 by all. But the extent to which the presence or absence of such a non- 

 evaporating layer influences plant growth and fruit production in a 

 critical time, is not so fully appreciated. Plate 3 gives an illustrative 

 example of trees grown this season on adjacent fields, with only a lane 

 between, the soil and all natural conditions being absolutely identical; 

 the only difference being the presence or absence of cultivation. In 

 the present case the cultivation was omitted on principle by one 

 owner, who considered cultivation superfluous on the loose, generous 

 soil of Alameda creek; while his neighbor, across the way, held the 

 opposite belief, and had this season cultivated to an extra depth to 

 conserve moisture. The cultural results are sufficiently shown in the 

 plates and need no comment, although it may be of interest to men- 

 tion that the year's growth on the one hand was over three feet, on 

 the other barely three inches. 



The difference of 244 tons per acre of ground shown by the analyses 

 is ouite sufficient, according to the data given at the beginning of thi& 



