104 THE SOIL OF THE FARM. 



in the manure, we have recovered something less than 

 fifty per cent, of the amount supplied, and this, too, 

 under the influence of an unusually favorable season! 

 Taking an average of seasons, it would be much nearer 

 the truth to say that n^t more than one- third of 

 the nitrogen supplied is recovered in the croj). Pota- 

 toes contain twenty-five per cent, of dry matter in 

 every one hundred pounds; if we take a bushel to weigh 

 fifty pounds, eight bushels will weigh four hundred 

 pounds; which amount is equivalent to one hundred 

 pounds of dry matter, and will contam one pound of 

 nitrogen. 



To obtain this one pound of nitrogen in the produce, 

 we find it necessary to apply three pounds in the manure, 

 and as the nitrogen costs about twent3^-five cents per 

 pound, this large difference between the amount supplied 

 and that recovered becomes a very serious consideration. 



I might further observe that as our experiments are 

 conducted with more care and attention than could pos- 

 sibly be given to crops grown under the ordinary opera- 

 tions of agriculture, I do not think it would be safe to 

 reckon on a smaller loss than that which we have incurred, 

 and the probability is that it might be much larger. 



The general conclusion to be drawn from these experi- 

 ments, as well as from those upon root crops in general, 

 such as turnips, mangels, and sugar beets, is that they do 

 not obtain their nitrogen from the atmosphere; and that, 

 when supplied with that substance, the amount recovered 

 in the crop is very much less than that supplied in the 

 manure. 



The Loss of Mtroffcn as Mtric Acid.— In one of the 



arable fields at Rothamsted we placed, ten years ago, 

 three sraujres, each havins: an area of one one-thousandth 

 of an acre, at tlie various depths of twenty, forty, und 

 sixty inches below the surface. The operation was per- 



