EXPERIMENTS ON CLOVEK. 



139 



" The ash of wheat contains, in 100 parts : 



Grain. 



Phosphoric acid 50.0 



Sulphuric acid 0.5 



Carbonic acid 



Silica .' 2.5 



Lime 3.5 



Magnesia 11.5 



Potash 30.0 



Soda, chloride of sodium, oxide of iron, sand, etc 2.0 



Total.., 



Straw. 

 5.0 



2.7 



67.0 

 5.5 



2.0 

 __13.G 



4.8 



100.0 



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

 bushels, which, at 60 Ibs. per bushel, gives 1,500 Ibs. ; and as the 

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

 duce will be 3,000 Ibs. According, therefore, to the preceding 

 data, there will be carried away from the soil : 



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

 In 3,000 Ibs. of the straw. . 150 Ibs. of mineral food, (in round numbers). 



Total 175 Ibs. 



** On the average of the analyses, it will be found that the com- 

 position of these 175 Ibs. is as follows : 



25. Ibs. 150. Ibs. l'<5. Jbs. 



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

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

 whilst a good crop of clover removes as much as 672 Ibs. 



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

 8 : ;raw of one acre of wheat, consists of silica, of which there is an 

 ample supply in almost every soil. The restoration of silica, there- 

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

 single instance on record, proving that silica, even in a soluble 

 condition, has ever been applied to land, with the slightest advan- 

 tage to corn, or grass-crops, which are rich in silica, and which, for 

 this reason, may be assumed to be particularly grateful for it in a 

 soluble state. Silica, indeed, if at all capable of producing a bene- 

 ficial effect, ought to be useful to these crops, either by strengthen- 

 ing the straw, or stems of graminaceous plants, or otherwise bene- 

 tting them ; but, after deducting the amount of silica from the 



