34 CALIFORNIA FRUITS: HOW TO GROW THEM 



hardened soil layers interfere with root development and make for 

 poor aeration and water supply. They must be broken up by plow- 

 ing or subsoiling. 



Rise of Ground Water. The rise of the water table mainly due 

 to excessive irrigation or the impermeability of one of the under- 

 lying soil layers is a question of the most serious significance and 

 one which the prospective purchaser of land or the owner of cropped 

 land must not lose sight of. For this reason precautions taken in 

 the examination of land for hardpan, irrigation with necessary, but 

 not superfluous, amounts of water and adequate provision for drain- 

 age will not only go far toward making land profitable at the time 

 cropping is commenced, but will prevent troubles for the future 

 through the accumulation of alkali and other baneful physiological 

 effects on plants of a high water table. 



Alkali. The term "alkali" denotes an accumulation of salts, in 

 a limited depth of soil, which may be of such nature and quantity as 

 to render the soil partially or totally unfit for profitable cropping. 

 The term has no necessary reference to the reaction of the soil, as is 

 commonly supposed, is therefore, a misnomer, and should not be con- 

 fused with the term "alkaline," as referred to soil, since the latter 

 denotes merely a "sweet" or favorable condition for the develop- 

 ment of most of our crop plants. 



The "Alkali" salts may include common salt, Glauber salt, car- 

 bonate of soda, Epsom salt, the chlorides of calcium and magnesium 

 and more rarely some others, but for practical purposes we may take 

 the ordinary classification, namely that of "black" and "white" 

 alkali as being sufficient for the needs of soil management. By the 

 "black" alkali, which is by far the most harmful of the sodium of 

 salts mentioned, we mean carbonate of soda. It is so called because 

 it dissolves out the humus and forms a black slimy layer on the sur- 

 face. Very small quantities of this salt are sufficient to make clay 

 soils unworkable because of the puddling effect it has on clay, and 

 similarly very small quantities of it have the power of stopping the 

 important process of nitrification. Since poorly aerated soils in the 

 arid regions are favorable to the reactions which produce "black" 

 alkali, especially where carbonates are plentiful or where excessive 

 amounts of nitrate of soda are used for fertilizing, no pains should 

 be spared to insure to soils, as nearly as possible, perfect aeration 

 through drainage and tillage ; great care should be exercised in the 

 use of irrigation water, and nitrate of soda should be employed 

 sparingly. 



The term "white alkali" is usually applied to either common salt 

 or Glauber salt, or both, in soils. Where present in sufficient quantity 

 white alkali salts may, through evaporation of water, be deposited 

 on the surface of the soil as a white efflorescence, such as that seen 

 in exaggerated form on the Nevada desert, on some soils of the San 

 Joaquin Valley and on some of the Coachella Valley soils. Of the 

 "white" alkali salts common salt is by far the more harmful, and 

 most fruit trees are not very resistant to it. They can, however, be 



