EXPERIMENTS ON CLOVER-SOILS. 157 



amounts of nitrogen per acre in the different sections of the two 

 portions of the 11-acre field. 



PERCENTAGE OF NITROGEN PER ACRE. 



First Second Third 

 six inches, six inches, six inches. 

 Lbs. Lbs. Lbs. 



I. In soil, clover twice mown* ) 3,350 1,875 1,335 



II. In soil, clover once mown and seeded > 



afterwards! ) 4,725 3,350 2,225 



} 

 * I. Clover twice mown ............... V 4,050 2,275 1,600 



) 5, 



Equal to ammonia : 

 I. Clover twice mow 

 t II. Clover seeded .................... 5,725 4,050 2,700 



Lbs. 

 I. Nitrogen in roots of clover twice mown .................. ) 24i 



II. Nitrogen in clover, once mown, and grown for seed after- V 



wards ................................................... ) 5H 



I. Weight of dry roots per acre from Soil I ................. [ 1,493 i 



II. Weight of dry roots per acre from Soil II ................. j 3,623 



Total amount of nitrogen in 1 acre, 12 inches deep of Soil I*. ) 5,249s 



Total amount of nitrogen in 1 acre, 12 inches deep of Soil lit. j 8,12G 



Excess of nitrogen m an acre of soil 12 inches deep, calculated j KQOI 



as ammonia in part of field, mown once and then seeded.. . . j *&*~* 



* Equal to ammonia ...................................... ) 6,374? 



fEqual to ammonia ...................................... j" 9,867 



" It will be seen that not only was the amount of large clover- 

 roots greater in the part where clover was grown for seed, but that 

 likewise the different layers of soil were in every instance richer 

 in nitrogen after clover-seed, than after clover mown twice for 

 hay. 



" Reasons are given in the beginning of this paper which it is 

 hoped will have convinced the reader, that the fertility of land 

 is not so much measured by the amount of ash constituents of 

 plants which it contains, as by the amount of nitrogen, which, to- 

 gether with an excess of such ash constituents, it contains in an 

 available form. It has been shown likewise, that the removal from 

 the soil of a large amount of mineral matter in a good clover-crop, 

 in conformity with many direct field experiments, is not likely in 

 any degree to affect the wheat-crop, and that the yield of wheat on 

 soils under ordinary cultivation, according to the experience of 

 many fanners, and the direct and numerous experiments of Messrs. 

 Lawes and Gilbert, rises or falls, other circumstances being equal, 

 with the supply of available nitrogenous food which is given to 

 the wheat. This being the case, we can not doubt that the benefits 

 arising from the growth of clover to the succeeding wheat, are 

 mainly due to the fact that an immense amount of nitrogenous 

 food accumulates in the soil during the growth of clover. 



