143 



CHAPTER IX. 



MEANS ADOPTED FOR IMPROVING THE SOIL AND MAINTAINING 

 ITS FERTILITY BY TEE APPLICATION OF MANURES. 



VEGETABLE AND MINERAL MANURES. 



213. Vegetable Manures. — The animal manures which 

 have been described in the preceding chapter, you have seen 

 derive then* valuable qualities from containing certain com- 

 pounds which, by their decay, are capable of affording am- 

 monia (154), and also the various inorganic materials which 

 are equally indispensable for the nourishment of our crops. 

 Therefore, by placing these manures in the soil, we restore 

 to it the matters taken away in the course of cultivation. 

 When we apply to our fields the decomposing straw, leaves, 

 and other vegetable remains of the manure heap, we in the 

 same way replace in the soil, the ingredients which the stems 

 and leaves of our crops had appropriated during their growth. 



214. Green manuring But in addition to employing ani- 

 mal excrements, and the decomposing litter and refuse vegetable 

 matters collected in the manure heap, the farmers in various 

 parts of Europe have been accustomed from the earliest 

 times to enrich their poor or exhausted soils, by growing 

 npon them certain crops, which instead of being used for 

 food, are ploughed in to serve as manure. This practice of 

 green manuring, as it is termed, is regarded as signally 

 beneficial in the countries in which it is practised; thus the 

 farmers in the north of Germany find that the most effectual 

 method of obtaining good crops of rye from sterile sandy soils 

 is to manure them with several crops of spun-ey or of white 

 lupins, and in the United States, both clover and Indian corn 

 are frequently ploughed in for the purpose of enriching the 

 land. In some parts of England and Scotland, buck-wheat 

 and vetches arc grown as manure- crops, and turnips are also 

 occasionally ploughed in spring as a preparation for wheat. 



215. When green vegetables are buried in the soil, they un- 

 dergo the same changes as when placed in the manure heap ; 

 they are rapidly resolved into their original elements, and yield 

 up the mineral matters and gases which they had accumulated 



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