322 FARMERS' INSTITUTES. 



and other root crops, and accelerates the ripening of grain and fruit. Any 

 manures remaining in the ground in the inactive condition will be made 

 active and available by the use of lime. 



Ilagnesia is found in all fertile soils, but the amount is often very small. 

 While it is indispensable in plant growth, its influence is much less marked 

 than lime, because of its inferior chemical activity. The amount removed in 

 ordinary crops is small. If we take a crop of wheat (thirty bushels) barley 

 (forty bushels) and oats (forty-five bushels), the grain and straw of these three 

 crops would contain about twenty-four pounds of magnesia, or eight pounds 

 an acre for each crop. 



Potash. — All fertile soils contain potash in available forms. It is one of 

 the most important chemicals of agriculture. No crop can be raised, or plant 

 grow in the absence of potash. The amount removed in crops is much larger 

 than the oxide of iron, lime and magnesia, being about forty-five pounds to 

 the acre in grain crops, and much more in root crops. 



The amount found in different soils varies widely. Clay loams contain .5 

 to .8 per cent. ; light loams from .3 to .4 per cent, and sandy soils of great 

 depth may fall as low as .1 per cent, and still be fertile. These are the esti- 

 mates of Hilgard. 



Keferring to the tables of analyses, you see that the sands of the plains 

 contain a good supply of potash, the lowest being .63 per cent (25,000 lbs. 

 per acre), and the highest 1. per cent (more than 40,000 lbs. per acre). The 

 abundant supply of potash iu these soils, in connection with their great 

 depth, is a hopeful feature in their agricultural possibilities. The Chemist 

 of the Department of Agriculture says that a soil containing .125 (^) per 

 cent should furnish potash enough for a century. On this basis, the plains 

 should be good for five hundred to eight hundred years of cropping. 



Sulphuric acid. — The sulphates are present in very small amount in the 

 soils of the plains. It is only by using a considerable amount of soil that 

 satisfactory reactions for sulphates can be secured. You will notice that the 

 two soils that have been cultivated — Metcalf's and Hanna's — have more sul- 

 phuric acid than the virgin soils. A similar fact came to my notice many 

 years ago in analyses of water from stations on the Grand Rapids & Indi- 

 ana railroad, when I found the amount of sulphates in the water gradually 

 increased from Mackinaw City to Fort Wayne. In the uncultivated regions 

 the sulphates were in very minute amount, but where lands had been brought 

 under cultivation the sulphates were found in increased quantity. A part 

 of this increase came from the use of plaster on the fields, but a part comes 

 from the oxidation of sulphide of iron in the soil, in consequence of culti- 

 vation. The well water at Grayling contains small, nearly insensible quanti- 

 ties of sulphates and sensible quantities of chlorides. The amount is so 

 small in this general filtrate from the soil (well water) that I am inclined to 

 think that good results will follow the use of plaster and salt on the plains 

 when once the soil is subdued and adequately supplied with humus or 

 organic matter. 



Phosphoric acid is found only in small quantity even in the most fertile 

 soils. The largest amount found by Hilgard in the upland soils of West 

 Tennessee and Mississippi was .25 per cent. In the rich alluvial soils of the 

 river Eaisin bottoms I found .4 per cent. 



Hilgard states that in sandy loams .10 per cent, accompanied by a fair sup- 

 ply of lime, secures productiveness, but that a soil containing less than .05 



