SOME POINTS IN PRACTICE 



rise fast enough to supply the plant dur- 

 ing spells of very dry weather. Further- 

 more, such soils prevent the downward 

 penetration of the roots of the plant, and 

 are therefore to be avoided. Again, soils 

 containing a large quantity of humus 

 (decaying vegetable and animal matter) 

 are much better than those which are 

 lacking in this quality. Humus not only 

 increases the moisture-holding capacity 

 of soUs, but also improves their mechani- 

 cal texture. Although arid soils are 

 usually comparatively poor in humus, 

 they are much richer in nitrogen than the 

 soils of humid regions, and so, smaller 

 amounts suffice. It has also been recently 

 found that the nitrifying germs are pres- 

 ent in large numbers in the soils of the 

 drier regions and in a very active state. 

 Soils known to be poor in lime should be 

 avoided, or supplied with marl or quick- 

 lime, preferably with marl. Of course, 

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