32 



use by the plant. For this reason, a soil on which alkali weeds and 

 grasses have grown will be found to be rich in available |>lant food. 

 If a soil containing a large percentage of humus and sodium carbon- 

 ate is washed with water, the teachings will have a black color show- 

 ing that the sodium carbonate (black alkali) has dissolved the hu- 

 mus, and, consequently, a good proportion of the available plant 

 elements are being washed away; so that, in general, where there are 

 large quantities of alkali, the soil has really been improved so far as 

 accumulating a supply of plant food is concerned. 



After an irrigation, soils containing an excess of black alkali may 

 be covered over by a hard crnst impervious to water and not easily 

 disintegrated, which by no means improves the physical condition of 

 the soil but rather counteracts the benefits of previous cultivation. 

 Jn some soils this layer is formed below the surface and so greatly 

 hinders the natural drainage. 



A soil containing a predominance of common salt alkali will have 

 the property -of securing and retaining moisture. The hygroscopic 

 power will be high. An analysis of the crust of such a soil showed its 

 hygroscopic moisture to be 32 %. It is owing to this that salty lands 

 will support a certain kind of plant growth without irrigation. Cal- 

 cium choride in sufficient quantities will have the same effect. 



While a large amount of white alkali in the soil is not desir- 

 able, its presence indicates that the general condition of the soil is bet- 

 ter than in the case of excess of chlorides or carbonates. 



EFFECT OF EXCESSIVE ALKALI ON CANE. 



Both the soil and cane are benefitted by a moderate amount of al- 

 kali; the harm begins when the alkali is sufficient to interfere with 

 the natural functions of the growing cane. 



Seed cane is planted in the trough of the furrow and covered with 

 a few inches of earth. The alkali in the soil collects in the first few 

 inches of surface soil. The seed cane would lie, therefore, just where 

 the concentration of alkali is greatest. If the alkali is strong enough, 

 the buds are killed immediately in the sane way that they would be 

 killed if soaked in a strong brine. If the alkali is not strong enough 

 to kill them directly, the roots may sprout but they will have to battle 

 continually against its harmful influence. Although all the elements 

 of plant food may exist in the soil in the most assimilable condition, 

 the plant cannot properly utilize them for its normal development 

 because its tissues are constantly being attacked and destroyed, and 



