AVAII.ABr.K XITKOc^.EX OF TTIK SOIL. 281 



than the most barren sand. Tri eiglit distinct trials the 

 crops "weighed (dry) but 3 to 5 times, in one case 8 times 

 (average 4 times), as much as the seed; while in sand, 

 pumice, or burned soil, containing no nitrogen, Boussin- 

 gault several times realized a crop weighing 6 times as 

 much as the seed, though the average crop of 38 experi- 

 ments was but 3 times, and tlie lowest result l{r times the 

 weight of the seed. 



The fact that the nitrogen of this garden soil was for 

 the most part inert is strikingly shown on a comparison 

 of the crops yielded by it to those obtained in barren 

 soil with aid of known quantities of nitrates. 



In a series of experiments with the Sunflower, Boussin- 

 gault {Ar/ronomie, etc., I, -p. 233) obtained in a soil desti- 

 tute of nitrogen a crop weighing (dry) 4.6 times as much 

 as the seeds, the latter furnisliing the plants 0.0033 grm, of 

 nitrogen. In a second pot, with same weight of seeds, in 

 which the nitrogen was doubled by adding 0.0033 grm. in 

 form of nitrate of soda, the weight of crop was nearly- 

 doubled — was 7.6 times that of seeds. In a third pot the 

 nitrogen was trebled by adding 0,0066 grm. in form of ni- 

 trate, and the crop was nearly trebled also — was 11.3 

 times the weight of the seeds. 



In another experiment (p. 271) the addition of 0.194 

 grm. of nitrogen as nitrate of potash to barren sand with 

 needful mineral matters, gave a crop weighing 198 times 

 as much as the seeds. But in the garden soil, which con^ 

 tained, when 40 grms. were employed 0.104 grm., and when 

 130 grms. were used 0.338 grm. of nitrogen, the result of 

 growth was often not greater than in a soil that contained 

 no nitrogen, and only in a single instance surpassed that 

 of a soil to which was added but 0.0033 gim. The fact 

 is thus demonstrated that but a very small proportion of 

 the nitrogen of this soil was assimilable to A^'getation. 



I'rom these beautiful investigations Boussingault deems 

 it highly probable that in this garden soil, and in soils 



