218 CALIFORNIA FRUITS: HOW TO GROW THEM 



allied to this is the action of alkali on soils thus artificially water- 

 soaked. This has been made the subject of a special publication 

 by Professor Hilgard, to which allusion has already been made 

 in Chapter III. Drainage is plainly essential, both in individual 

 farms and in districts where the water level is rising too high, and 

 the striking statements given below by Professor Hilgard should 

 incite all to give immediate attention to the needs of vines and 

 trees in this regard. 



The following summary of drainage needs, and the advantage 

 ol providing drainage when needed, is made by Professor Hilgard : 



In the valleys and plains of the arid irrigation countries the soils are pre- 

 dominantly of a light, sandy or silty nature, easily penetrated to great depths 

 by water and air. With these the roots of plants also reach to such depths, 

 drawing therefrom not only moisture but also plant food, which in these 

 soils is, as a rule, very abundant. The plants of the arid region thus are 

 enabled to utilize nearly as many feet of soil mass as in the regions of 

 summer rains inches would be drawn upon; and it is evident that this advan- 

 tage, which postpones for a long time the need of fertilization, should not 

 be lightly thrown away. Each farm in the arid region has several similar 

 ones underground, which with proper management can be fully utilized. 



But this presupposes that the water, air and roots can all penetrate 

 under irrigated culture as they do in the natural condition. It means that 

 the ground water level shall not be allowed to rise to such an extent as 

 to prevent the penetration and healthy life of the roots in the depths of the 

 soil mass. If by intentional or careless over-irrigation, or by leakage from 

 the ditches, the water level is allowed to rise within a few feet of the sur- 

 face, the wonderfully productive lands of the arid valleys are reduced to 

 the same condition as are those of the humid countries: a shallow layer 

 of surface soil, within which alone the roots can exercise their functions 

 of plant nutrition. The natural result is that this layer soon becomes 

 exhausted, and copious artificial fertilization is required to maintain prof- 

 itable production. 



And even this is 'the most favorable case. When, in addition, the upward 

 movement of the soil water carries with it the entire mass of salts of various 

 kinds which exist in all arid soils, and brings them within reach of surface 

 evaporation, these "alkali" salts impregnate the soil to such an extent as to 

 render the cultivation of many crops unprofitable, or sometimes altogether 

 impossible. 



Summarizing the advantages of systematic land draining it may be said 

 that: 



1. It prevents the drowning out of the deeper roots of plants by the 

 rise or fluctuations of the ground water, by which the vineyards and orchards 

 are so frequently rendered unprofitable. 



2. It prevents, or at least limits definitely the shallowing of the soil 

 caused by high-lying ground water, resulting in the need of early and 

 copious fertilization, which would otherwise not have been called for in 

 many years. The annual cost of such fertilization will soon exceed the first 

 cost of drainage. 



3. Drainage does away definitely with the alkali evil. When drainage is 

 established the land can easily be so handled as either to remove all the 

 alkali, or to leave in the soil so much of it as may be rationally considered 

 beneficial, on account of its usual content of valuable and highly available 

 plant food. To prevent the waste of much of this soluble plant food, the 

 use of gypsum is also valuable; but subsequent swamping of the land would 

 cause a return of the black alkali unless drainage were provided for. 



