682 



TABLE II. The average amount of ash, nitrogen, phosp 

 acid and potash per cent, and per ton in some plants : 



In table i. we see the actual components in 100 parts of 

 the ash or mineral matter taken from the soil by various plants. 



No. ii. gives the amount of ash, nitrogen, phosphoric acid, and 

 potash in 100 parts of the different crops mentioned. They are 

 also reckoned out to Ibs. per ton of the crops. 



It would seem from table n. that the leguminous plants re- 

 quire a larger supply of nitrogenous manures than the cereals, as 

 they contain more nitrogen. They do not require more, in fact, 

 they are more benefited by potash. The reason for them 

 containing more nitrogen than the cereals is that they have 

 the power of absorbing nitrogen from the air, a power not 

 possessed by other plants, in fact, they arc considered to 

 enrich the soil with nitrogen. Thus it is that cereals which 

 require a good supply of nitrogen, should follow Leguminous 

 crops in the rotation. To show how severe some crops 

 are on the fertility of the soil we will take the case of wheat and 

 potatoes. .Suppose we had a crop of, say 30 bushels of grain and 

 3,100 His. of straw per acre. If the grain alone was sold off the 

 farm it would carry away 34] H>s. of mineral m liter, containing 

 15), His. of phosphoric acid, equal to i 13 H>s. of superphosphate ot 

 30 per cent, tricalcic phosphate made soluble ; tjj, H>s. ot potash, 

 equal to (>S ll.s. of kainit and nitrogen, 3_\\ l\>^., equal to ihj U.S. of 

 a ->7 per cent, sulphate ot ammonia. If the straw was also sold, as in 

 the case of chaff, it would take away iS<y_> ll.s. of mineral matter, 

 containing 21.', H>s. of phosphoric acid, equal to 153 lls. ot super- 



