154: MANURES. 



the foregoing offices. For instance, we harrow stable 

 manure into a clay loam. It furnishes the plant with 

 eight or ten kinds of food ; the salts contained in the 

 manure act on the silicates in the soil as stimulants ; 

 and the manure itself, mingling with the heavy soil, 

 renders it more open and porous. Or if we sow plas- 

 ter upon a clover field, it performs at least two offices : 

 it feeds the clover with sulphuric acid and lime, and 

 it stimulates the soil, hastening the decomposition of 

 organic matter contained in it. 



ORGANIC MATTER— HOW TO ASCERTAIN ITS 

 AMOUNT IN A SOIL. 



288. By recurring to Table lY., it will be seen that 

 among the ingredients of soils, is organic matter. 

 This, so far as of vegetable origin, consists of oxygen, 

 carbon and hydrogen, with a very little nitrogen. So 

 much of it as is of animal origin contains the same ele- 

 ments, with a larger proportion of nitrogen, and a very 

 little sulphur and phosphorus. This organic matter is 

 essential to the fertility of soils. Its tendency is to in- 

 crease in lands that are in grass, but to diminish in 

 those under the plough, till it comes below the point 



essential tcf fertilitv. 



»/ 



289. The farmer may easily decide, whether a field 

 is deficient in organic matter. He may take a hand- 

 ful of soil from half a dozen places ; mix all together ; 

 dry it as dry as it can be made in the sun ; put it on 

 white paper and dry it in an oven at a temperature 



