80 BOARD OF AGRICULTURE. 



served or unestimated influence on production, yet being in a good 

 degree at least based on known truth, is Avorthy of careful consider- 

 ation, and may prove suggestive of improved practice. It may be 

 briefly explained as follows : The analyses of plants show that they 

 all contain a certain amount of inorganic ingredients, or in other 

 words, of mineral substances, which, after the combustion of the 

 plant, remain behind in the form of ashes. This ash is that portion 

 of the plant which it obtained from the soil, (the portion which was 

 obtained from the atmosphere and from moisture having all passed 

 away in gaseous form.) and consists of lime, potash, soda, silica, 

 phosphoric acid, and other substances, and in proportions varying 

 greatly according to the jtUnit^ from the combustion of which 

 tlie ash is obtained. 



Thus we find that clover, potatoes, turnips, kc, have drawn heavily 

 upon the potash in the soil, while wheat and other cereal crops demand 

 more largely of phosphoric acid, and leguminous plants, as peas, 

 befans, &;c., abstract lime in abundance, and so of all others, the ingre- 

 dients or the proportions of the ingredients of no two being exactly 

 alike ; each having its own distinct and specific requirements. As 

 these mineral substances could not be furnished to the plant either 

 from the atmosphere or from water, it is clear that they umst have 

 been derived from the soil, and it is demonstrably certain, having 

 been proved by the most careful and decisive, experiments, that the 

 absence from the soil of the proper quantity of any one of the neces- 

 sary elements, will prevent the perfect development of the plant, and 

 that its presence in the soil or its addition to it by means of manure, 

 is as necessary a condition of successful growth as is liglit, air or 

 moisture.. 



Some of these mineral substances, as potash, phosphoric acid, &c., 

 exist in different soils in widely differing proportions, and in most 

 cases in very limited quantities. Now, as the requirements of differ- 

 ent species or fiimilies of plants vary so much from each other, that 

 a soil, which, after successive crops of one plant being removed from 

 it, refuses longer to produce a remunerating crop, (that is to say, 

 will not produce a respectable crop without a too costly manurial 

 application to supply its wants,) may yet yield freely of another 

 species, the value of a judicious rotation stands out in a strong 

 light. 



