94 AMERICAN MANURES. 



of silica is only one half of that required for 

 wheat straw. 



BUCKWHEAT. 



Thirty bushels of buckwheat the estimated 

 product of an 'acre of 40 Ibs. to the bushel 

 = 1200 Ibs. The straw weighs about 2000 Ibs. 

 The grain and straw contain: 



Grain. Straw. Total. 



Ammonia.. ..18-24 Ibs. 1-20 Ibs. 19-44 Ibs. 



Phosphoric Acid. 12-00 " 12-20 



Sulphuric Acid.. 5*22 " 6-20 



Lime 1-56 " 22-00 



Magnesia 2-40 " 4-20 



Potash... . 2-04 " 55*20 



24-20 

 11-42 

 23-56 

 6-60 

 57-24 



Silica 0-24 " 6-60 " 6'84 



The reader will notice that this crop requires 

 a large amount of potash, while the amount of 

 ammonia and phosphoric acid is comparatively 

 small. The potash seems to take the place of 

 silica in the formation of the straw, as only a 

 small amount of that substance is required. As 

 this straw contains very little ammonia, it is 

 almost worthless as fodder ; but as manure it is 

 valuable for its phosphoric acid, lime and potash. 



POTATOES. 



One hundred bushels of potatoes, of 60 Ibs. to 

 the bushel = 6000 Ibs. of tubers. The tops, when 

 dry, weigh about 3000 Ibs. ; and the tops and 

 tubers of such a crop contain : 



