118 FUNDAMENTALS OF FRUIT PRODUCTION 



solution of calcareous or manganiferous soils where chlorosis is produced. 

 Possibly the application of acid in some form would be as effective in 

 preventing chlorosis as the apphcation of iron salts to the leaves or cut 

 surfaces. 



Acid Tolerance of Certain Crops. — Most deciduous orchard fruits are 

 acid tolerant to a considerable degree. The strawberry has been shown 

 to prefer an acid soil-"^ and the blueberry^^ demands a soil markedly 

 acid in reaction. In the practically neutral reaction of a good garden 

 loam it fails to thrive or even dies out. The superior development 

 of wild raspberries, blackberries, dewberries and haws in soils that are 

 at least slightly acid suggests that their cultivated relatives may be 

 at home in similar soil conditions. That deciduous fruits are not alone 

 in their tolerance or preference for soil acidity is indicated by the behavior 

 of citrus trees in acid soils. 



CoIIison" in reporting the results of a series of fertilizer experiments in Florida 

 says: "So far as could be noted an acid soil has no injurious effect on the growth 

 of the orange tree. On some of the most acid plots in the grove the trees are 

 vigorous and have made very good growth, ranking well up among the best plots 

 in the grove." 



Furthermore, practically all of the best orchard cover crops are dis- 

 tinctly acid tolerant. The following commonly used cover crops belong 

 in this class; cowpeas, soy beans, hairy vetch, crimson clover, rye, oats, 

 millet, buckwheat and turnip. ^^ 



Since deciduous fruit plants are predominantly acid tolerant, they 

 should not be exposed to a markedly alkaline reaction of the soil. Ammo- 

 nia in considerable amount depresses root growth and eventually kills 

 the roots, because of its effect on the soil reaction. Injuries resulting 

 from an excess of "alkali," as the term is generally used in the arid and 

 semiarid sect ons, are due not to any effect these salts may have on 

 the reaction of the soil, but rather to the excessive concentration of 

 the potassium and sodium salts that are present. The difference between 

 the toxic symptoms attending an alkaline or basic soil reaction and those 

 attending impregnation with "alkali" is well marked. A soil solution 

 having an alkaline reaction affects the roots before the shoots; the toxic 

 effects of a soil solution which is too concentrated are evident first in the 

 shoots. 



Concentration: Soil "Alkali." — As just pointed out, the term "soil 

 alkali" does not refer to the soil reaction, but to an excessive concentra- 

 tion of certain salts. The carbonates, chlorides and sulfates of sodium 

 and potassium are concerned chiefly, though occasionally other salts 

 accumulate in such amounts as to be injurious. 



Tolerance of Different Fruits. — The degree of tolerance of various fruit 

 crops to salts of different kinds is indicated by data presented in Table 13. 



