EXI'KIUMENTS ON < LOVER-SOILS. 157 



amounts of nitrogen per ariv in tlic (lilVmnt sections of the two 

 portions of Ibe ll-arrc tield. 



peklknta(;e of xituockn i'kk acre. 



Mnt Sei-imd T/iinl 



air iiic/ifn. xU iiirhen. six iitc/ua. 



/J>.i. Lb<. IJm. 



I. In poll, clover twico mown* i 3,:}50 1,875 \^',i2ii 



II. In soil, clovtr once mown and 8«'i'(liMi v 



aflerwur.lst ) 4,7jr, '.\:iiQ 2.235 



Equal to ammouiii : i 



♦ I. Clover twice nu.wn V 4,05') 3,275 1,600 



t II. Clover seeded ) ".,725 4,050 2,7t)0 



TMs. 



I. Nitroppn in roots of clover twice mown \ 34i 



II. Nitrofjcn in clover, onee mown, anil grown for seed after- V 



wurds .' ) 5U 



I. Wfi-^lit of dry roots per acre from .Soil 1 ( l,4'.>;;i 



II. Weiiriit of dry roots per acre from Soil II ) 0,022 



Total amount of nitronen in 1 jiere, 12 inches deep <'f Soil I*. ( 5,24'Ji 



Total amount of nitroiren in 1 acn. 12 inches deep of Soil lit. \ 8,12;Ji 



Excess of nitroiren in an acre of soil 12 inches deep, calculated 



as ammonia in [>art of Held, mown once and then seeded 



3,592* 



• Equal to ammonia ) t5,S74i 



t Equal to ammonia !l 9,807 



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

 roots greater in the part wiierc cl<iver was grown for .^eed, but tliat 

 likewise the different layers of soil were in every instaix'e richer 

 in nitrogen after clover-socd, t'.ian after clover mown twice for 

 hay. 



" Reasons arc 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 

 jdanls which it contains, a.s 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 e.xporimcnts, 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 farmers, and the direct and numerous experiments of Messrs. 

 Lawes and Gilbert, rises or falls, otlier 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 nitrogenoua 

 food accumulates in the soil during the growth of clover. 



