60 ON INCREASING THE GROWTH 



Up to the present time they have obtained a yearly 

 increasing produce, and this, too, to an amount 

 which could hardly have been realized by the em- 

 ployment of the stable-manure produced upon their 

 farms alone. 



On the other hand, substances forming humus, or 

 already partially transformed into humus, are of very 

 great importance in improving the soil ; since they 

 are able to make binding and cold earth looser and 

 warmer, and thin and dry soil, on the contrary, more 

 binding and moist, as has been previously intimated. 



3. Alkalies (potash and soda). Of these bodies, 

 the salts of potash (potash in combination with 

 acids, carbonate of potash for example) exert the 

 most favorable and striking influence upon the 

 growth of plants, especially in the formation of their 

 strictly vegetable parts, or straw. This we see ex- 

 emplified in the action of wood-ashes, which are rich 

 in potash. According to its chemical nature, potash 

 belongs to the alkaline bodies, and in this particular 

 resembles ammonia. This similarity is manifested 

 also in its action, which, equally with that of am- 

 monia, is strongly forcing. Of the better known 

 manures, the urinous secretions of our domestic ani- 

 mals abound particularly in potash, inasmuch as the 

 alkalies contained in their food are for the greater 

 part eliminated by the kidneys. 



The fear has been expressed, that a soil, if the salts 

 of potash are not given to it, may become sterile 

 from want of these ingredients ; but this apprehen- 



