FERTILIZERS. 



233 



years (E. S. R., 9, p. 540). The apparatus and methods employed were 

 essentially the same as in the earlier experiments, except that the soil 

 used was taken from the field which has been devoted to experiments 

 on the continuous growth of maize on the same land (E. S. R., 9, p. 551). 

 Three series of experiments were undertaken : (1) With oats followed 

 by Hungarian grass; (2) with Hungarian grass; and (3) with rye and 

 oats followed by Hungarian grass. The soil used was a sandy loam on 

 which maize had been grown continuously for 8 years and which had 

 received no fertilizing material of any kind for 6 years. With the excep- 

 tion of nitrate of soda and ground bone, the fertilizing materials used 

 were the same as in the experiments of 1896. At the beginning of the 

 experiment the moisture content of the soil in the pots was kept between 

 10 and 15 per cent. When the heads first began to appear the quantity 

 of water was increased so that the moisture content of the soil was be- 

 tween 15 and 20 per cent. After the removal of the oat crop (both roots 

 and above-ground part) from the pots, the soil was returned to the pots 

 without further addition of the fertilizers and Hungarian grass was 

 planted. Details as to fertilizers applied and the weight and nitrogen 

 content of the crops produced are given in full in a table. The princi- 

 pal results are summarized as follows: 



Percentage availability of different forms of nitrogen in pot experiments with oats and 



Hungarian grass. 



Nitrate of soda . . 



Dried, blood 



Dry ground fish . 



Ground bone 



Tankage 



Horn and hoof. . . 



Linseed meal 



Cotton-seed meal 

 Castor pomace. . . 



Experiments in 1897. 



1.6 gm. I 1.2 gm. 

 fertilizer, fertilizer. 



Per cent. 

 (79. 6) 

 (65. 1) 

 (60. 3) 



49.8 

 (68. 8) 

 (60.4) 

 (59.2) 

 (59.9) 



Per cent. 

 (89. 3) 

 73.1 

 67.3 

 18.3 

 48.8 

 67.9 

 68.7 

 65.1 

 66.4 



fertile, *™* 



Per cent. Per cent. 



102.5 

 77.3 

 63.6 

 16.1 

 53.4 

 72.1 

 72.4 

 67.7 

 66.0 



102. 5 



75.2 

 65.5 

 17.2 

 50.7 

 70.0 

 70.6 

 66.4 

 66.2 



I Nitrogen 



Average availabil- 



of exper- ity reck- 



iments, oned on 



1894-1896. nitrate, 



1897. 



Per cent. 

 64 

 43 

 44 



Per cent. 

 100.0 

 73.3 

 63.9 

 16.7 

 49.4 

 68.3 

 68.9 

 64.8 

 64.6 



" It appears that in every case a much, larger percentage of the fertilizer nitrogen 

 was taken by the crops in the experiments of 1897, natural soil, than in the previous 

 cultures made in coal ashes and peat. Part of this increase is due to the inclusion 

 of roots with the crops in 1897. 



"The percentage availability of nitrogen to the oat crop of 1897 would have been 

 made less by about 12 per cent on the average if the roots had been excluded. 



"If we may assume that a like percentage added to the percentage availability as 

 determined in the experiments of 1894, 1895, and 1896 will correctly compensate for 

 the exclusion of the roots in those experiments, it still appears that on the average 

 a larger percentage of nitrogen was assimilated in the experiments of 1897 than in 

 the earlier ones. This is particularly noticeable in the case of nitrate and of dried 

 blood. 



" In these experiments of 1897 the nitrogen of raw knuckle bone, ground to pass 

 a sieve with circular holes one-fiftieth of an inch in diameter, had only one-sixth of 

 the availability of the nitrogen of nitrate, one-quarter of that of linseed, cotton seed, 



