FORAGE CROPS. 367 



" An acre, according to these determinations, contains in the 

 three separate sections : — 



lbs. lbs. lbs. 



Phosphoric acid 3)975 • • • • 4. ' 5° • • • • 3>5oo 



Nitrogen 4)7-5 ••■• 3)35° •••• 2)2^5 



Equal to ammonia 5)7-5 • • • • 4,050 .... 2,700 



*' Here again, as might naturally be expected, the proportion 

 of nitrogen is largest in the surface where all the decaying leaves 

 dropped during the growth of the clover for seed are found, and 

 wherein root-tibers are more abundant than in the lower strata. 

 The first 6 inches of soil, it will be seen, contained, in round num- 

 bers, 2^ tons of nitrogen per acre, that is, considerably more than 

 was found in the same section of the soil where the clover was 

 mown twice for hay ; showing plainly that during the ripening of 

 the clover-seed the surface is much enriched by the nitrogenous 

 matter in the dropping leaves of the clover-plant, 



" Clover-roots. — The roots from i square foot of this soil, 

 freed as much as possible from adhering soil, were dried at 212'', 

 and when weighed and reduced to a fine powder, gave, on analysis, 

 the following results : — 



♦Organic matter 6476 



•j-Mineral matters 3 5 '^4 



* Containing nitrogen l-yoz 



Equal to ammonia 2066 



t Including clay and sand (insoluble silicious matter). i&04 



*' A square foot of this soil produced 582 grains of dried clover- 

 roots, consequently an acre yielded 3,622 lbs. of roots, or more 

 than twice the weight of roots obtained from the soil of the same 

 field where the clover was twice mown for hay. 



" In round numbers, the 3,622 lbs. of clover-roots from the 

 land mown once, and afterward left for seed, contained 51 J lbs. 

 of nitrogen. 



" The roots from the soil after clover-seed, it will be noticed, 

 were not so clean as the preceding sample, neverthele^, they 

 yielded more nitrogen. In 64*76 of organic matter we have here 

 1702 of nitrogen, whereas in the case of the roots from the 

 part of the field where the clover was twice mown for hay, we 

 have 8 1 "33 parts — that is, much more organic matter, and 

 1*635, or rather less of nitrogen. It is evident therefore, that 

 24 



