FORAGE CROPS. 349 



" The ash of wheat contains in lOO parts : — 



Grain. Straw. 



Phosphoric acid 50-0 .... 50 



Sulphuric acid o'5 .... 2'7 



Carbonic acid 



Silica 25 67-0 



Lime.. 35 •••• SS 



Magnesia 115 .... 20 



Potash 300 130 



Soda, chloride of sodiunn, oxide of iron, sand, etc ... . ao .... 4'8 



lOO'O .... loo-o 



"The mean produce of wheat per acre may be estimated at 25 

 bushels, which, at 60 lbs. per bushel, gives 1,560 lbs. ; and as 

 the weight of the straw is generally twice that of the grain, its 

 produce will be 3,000 lbs. According, therefore, to the preced- 

 ing data, there will be carried away from the soil : — • 



In 1,500 lbs. of the grain . . 25 lbs. of mineral food (in round numbers). 

 In 3,000 lbs. of the straw. .150 '< " »' 



Total 175 lbs. 



" On the average of the analyses, It will be found that the com- 

 position of these 175 lbs. is as follows : — 



In the Grain. In the Straw. Total. 



Phosphoric acid 12-5 lbs 7-5 lbs 20.0 lbs. 



Sulphuric acid 01 " .... 4-0 " .... 4-1 *♦ 



Carbonic acid 



Silica 06 " .... 100-5 " .... loil " 



Lime 09 " .... 82 " .... 91" 



Magnesia 29 '* .... 30" .... 59" 



Potash 75" .... 19s " .... 270 " 



Soda, chloride of sodium, oxide of ) 



iron, sand, etc J 05 " .... 73" .... 7"8 " 



2S lbs. 150 lbs. 175 lbs 



"The total quantity of ash-constituents carried off the land in 

 an average crop of wheat thus amounts to only 175 lbs. per acre, 

 while a good crop of clover removes as much as 672 lbs. 



" Nearly two-thirds of the total amount of mineral in the grain 

 and straw of one acre of wheat consists of silica, of which there 

 is an ample supply in almost every soil. The restoration of silica, 

 therefore, need not trouble us in any way, especially as there is 

 not a single instance on record proving that silica, even in a solu- 

 ble condition, has ever been applied to land with the slightest 

 advantage to corn or grass crops, which are rich in silica, and 



