82 Physics of the Soil 



problem. By growing the same crop year after year on the 

 same ground to which no nitrogen-bearing manures were 

 applied, they learned that when fertilizers containing the 

 essential ash ingredients of the plant were added to the 

 soil larger yields and more nitrogen could be taken from 

 the ground. 



They found that when wheat grown continuously for 32 

 years on the same soil without manure of any sort could 

 obtain but 20.7 Ibs. of nitrogen per acre, the same crop on 

 adjacent and similar land given fertilizers without nitrogen 

 could gather 22.1 Ibs. or 6.76 per cent. more. Barley, 

 which, with no fertilizers, during 24 years could gather but 

 18.3 Ibs. per acre per annum, did, when aided with other 

 ash ingredients, remove from the soil 22.4 Ibs. of nitrogen 

 per acre. Beans, which gathered from untreated land 31.3 

 Ibs. of nitrogen per acre during 24 years, took off from the 

 land under the other treatment 45.5 Ibs. per acre. So, 

 too, in a rotation of crops, 7 courses in 28 years, no fertil- 

 izers gave 36.8 Ibs. of nitrogen, while with superphosphate 

 of lime the yield was 45.2 Ibs. per acre. Again in the 

 mixed herbage of grass land 20 years without fertilizers 

 gave 33 Ibs. of nitrogen per acre, but where mixed mineral 

 fertilizers containing potash were given the yield was 55.6 

 Ibs. of nitrogen per acre. 



95. Store of Nitrogen in the Soil, The mean amount of 

 nitrogen in eleven arable and grass soils at Kothamstead is 

 placed by Lawes and Gilbert at .149 per cent, and for eight 

 other Great Britain soils at .166 per cent. Voelcker found 

 in four Illinois prairie soils .308 per cent., and C. Schmidt 

 gives for seven rich Russian soils .341 per cent. The 

 mean of these 30 analyses is .219 per cent, and yet a soil 

 containing but .1 per cent, will carry 4,000 Ibs. or enough 

 for nearly 60 40-bushel crops. 



96. Amount of Nitrogen in Four Manitoba Soils. As an 

 example of soils exceptionally rich in nitrogen the table 



