PRINCIPLES OF MANURING. 43 



The method of farming that is surest to incapacitate most soils 

 for phmt production, is that of continuous cropping without the use 

 of manures. B}' such practices the fertile plains of the West have 

 in some states been brought to a condition that requires for their 

 cultivation, methods similar to those for a long time used of neces- 

 sit}- in Maine. A sj^stem of farming that leads to such a resnlt 

 should be designated as careless, and ignorant, especiall}- in older 

 states. Judged b}- its results, what proportion of Maine agriculture 

 could escape the above designation ? 



Cause of Infertility. 



What change does the soil undergo that diminishes its power for 

 plant production? We must arrive at an answer to this question 

 somewhat indirectl}'. A discussion of the changed composition of 

 the soil, as shown by analysis, would not tell us all we desire to 

 know. 



If a plant is burned some of it passes off and disappears in the 

 air, and a portion remains behind as the ash. When wood is burned 

 we speak of the residue as " ashes." Were I to burn a stalk of 

 wheat or corn with the ripened grain attached, and carefully save 

 and anah'ze the ash, I should find it to contain several compounds, 

 made up principally of the following substances, viz : phosphorous, 

 sulphur, silicon, chlorine, potassium, sodium, calcium, maguesium 

 and iron. A similar examination of that portion of the plant which 

 passed off in the air would reveal the presence of oxygen, hydrogen, 

 nitrogen and carbon. The plant in growing had gathered these ma- 

 terials from the soil and air. From them the plant had been builded 

 by the forces of nature. Now if these materials are available in 

 sufficient quantities, there seems to be no reason wh}' a plant 

 may not reach its fullest size and development. In fact, there sel- 

 dom is any reason wh}* luxuriant crops do not grow, save a simple 

 lack of materials to grow from. Is this lack one that extends to 

 all, or onl}' part of the ingredients that plants are found to contain? 

 In replying to this question, it should first be stated that not all the 

 substances found in plants are absolutely essential to their growth. 

 It seems that vegetable life n)akes use of some substances snnply 

 because they are at hand, and not because they are needed. 



Our German friends have proved for us what are the essential 

 constituents of the structure of our common agricultural plants, and 

 they have conclusively shown that any of our ordinary crops could 



