78 IMPROVEMENT OF THE SOIL 



CHAPTER X. 



IMPROVEMENT OF THE SOIL BY MINERAL MANURES. 



Although animal and vegetable matters are consider- 

 ed the true food of plants, as they are of animals, yet the 

 plant, like the animal, is benefited by certain mineral and 

 saline substances, which seem necessary to both, as stim- 

 uli or condiments, and which act either upon the food, in 

 fitting it for use, upon the organs of digestion or nutrition, 

 or become essential in giving form, strength, and firmness 

 to the animal and vegetable structure. Thus the bones 

 of animals are formed from the lime and phosphorus 

 which are taken in with the food. Without lime, the 

 eggs of fowls would be without a shell. All the earths 

 enter more or less into the animal and vegetable structures, 

 and into the seeds of the latter. Lime is found in the 

 wheat, gypsum in the clover, sulphur in the turnip, silex 

 in the stalks of Indian corn, and most of the cereal gras- 

 ses. Mineral substances are also beneficially employed 

 in improving the texture of the soil, and in fitting it to 

 promote the growth of plants. 



The most important of the mineral applications is lime. 

 Lime benefits in two ways ; first, in its caustic state, 

 deprived of its carbonic acid by fire, it dissolves vegeta- 

 ble fibre, and converts it into the food of plants ; and at 

 the same time, by forming new chemical compounds with 

 matters that are soluble, it prolongs the nutritive action 

 of soft vegetable and animal substances beyond the time 

 in which they would have acted, if they had not entered 

 into a combination with it. Hence, caustic, or quick- 

 lime, should not be applied with common dung, but to 

 soils abounding in peaty, fibrous, and other insoluble, inert 

 vegetable matters. And secondly, in its mild state, or 

 as a carbonate, it improves the mechanical texture of 

 sands and clays ; rendering the first more compact and 

 more retentive of manure and moisture, and the latter 



