1844 



ENCYCLOPEDIA OP PRACTICAL HORTICULTURE 



ash. The term "plant food" is often con- 

 fined to these three substances which are 

 so often needed. 



Lime may also be needed by the soil, 

 but the object of an addition of lime is to 

 correct the acidity of the soil or to per- 

 form other functions, rather than to serve 

 as a plant food. 



The object of fertilizers is to supply 

 phosphoric acid, nitrogen or potash in 

 available forms, that is, in such com- 

 pounds that plants can easily take up the 

 plant food. 



A soil, to be fertile, must contain plant 

 food in such forms that plants can secure 

 a sufficient amount of it. A soil may con- 

 tain a large quantity of plant food, yet 

 not produce good crops, because the 

 plants cannot secure the food which it con- 

 tains. We apply the term active plant 

 food to the plant food contained in the 

 soil in such forms that plants can easily 

 take it up. 



Physical Deficiencies of Soils 



Some of the physical deficiencies of 

 soils will here be mentioned only briefly. 



The soil may be too shallow. If this 

 is caused ,by rock near the surface, the 

 soil is not suitable for cultivated crops. 

 If caused by hardpan, it must be broken 

 up. If caused by water, the soil may be 

 drained. Soils in arid regions should be 

 deeper than those in humid regions. 



The soil may be too wet. If properly 

 situated this condition may be remedied 

 by drainage, either by ditches or by tile 

 drains. 



Porous and stift soils are both bene- 

 fited by organic matter, such as is pro- 

 duced by manure or green crops plowed 

 under. Lime may improve stiff soils, 

 making them more easily worked. 



Soils which blow too easily may re- 

 ceive benefit from manure. A wind-break 

 may also be of advantage. 



Chemical Deficiencies 



Acid soils contain an excess of acid. 

 The remedy is to apply lime in sufficient 

 amounts to correct the acid. Acid soils, 

 judging from our work under way, are 

 not found to any large extent in Texas. 



Definite conclusions, however, cannot be 

 reached until further work has been done. 

 Alkali soils contain too much soluble 

 salts. These consist of sulphate of soda, 

 chloride of soda, and carbonate of soda, 

 as a rule, but we have sometimes found 

 calcium chloride to be present. Crops 

 vary in their sensitiveness to alkali. Some 

 plants will not stand much, while others 

 will stand very large auantities. Alfalfa, 

 when young, will not stand much alkali, 

 but it appears to endure a large quantity 

 when it is old and well established. 



Most of the alkali which has been 

 brought to our notice occurs in compara- 

 tively small spots, but often is very 

 troublesome on account of its effect upon 

 the appearance of the field in which it 

 occurs. The remedy for alkali is under- 

 drainage, either by means of deep ditches 

 or tile drains. 



Deficiency of Apple Plant Pood 



A soil cannot be productive unless it 

 supplies the plant with sufficient food; 

 that is, unless it contains sufficient "ac- 

 tive" plant food. The amount of active 

 plant food depends upon conditions sur- 

 rounding the soil, as well as on the chem- 

 ical and physical character. The pres- 

 ence of sufficient moisture, and of decay- 

 ing vegetable matter, appear to aid in the 

 maintenance of a supply of active plant 

 food in the soil. A "run-down" soil may 

 often be "brought up" by increasing the 

 activity of the agencies which make inac- 

 tive plant food active. 



G. S. Praps, 



Chemist, Texas Agricultural Experiment Sta- 

 tion. 



COMPOSITION OP PEUIT SOILS 



The percentage of essential elements of 

 plant food in the typical soil of each of 

 the more prominent fruit districts of the 

 State of Washington is shown in Table 

 L These figures were obtained by aver- 

 aging the results of all the analyses of 

 soil samples from each of these districts 

 which were collected during the progress 

 of the soil survey of the state, which 

 was conducted by the Division of Chem- 

 istry of the State EJxperiment Station 

 during the years of 1893 to 1907 inclusive. 



