208 



ME LA WES' EXPERIMENTS UPON TURNIPS. 



experiments of MrLawes, similar to those described and discussed 

 in the previous sections, throw some additional light upon it. 



1. Experiments upon turnips. He drilled in certain mineral 

 manures with the seed over the whole field ; he then top-dressed 

 different parts of it with rape-dust, sulphate of ammonia, and a 

 mixture of the two. When the crop was gathered, the propor- 

 tion of nitrogen in the turnips grown upon each plot was deter- 

 mined as nearly as possible by repeated analyses. The numbers 

 in the following table represent the total produce, and the per- 

 centage of nitrogen in the dry turnip bulbs, produced by the aid 

 of the different manures : 



a The last line of this table, compared with the first and third, 

 shows that the proportions of nitrogen applied had no sensible re- 

 lation whatever to the total weights of the crops produced. This 

 agrees with the deduction we drew in the preceding section. 



b As to the quality of the crop, as indicated by the propor- 

 tion of nitrogen in the bulbs, it appears that it increased in all 

 the experiments till the quantity of nitrogen per acre reached 71 

 lb., but that it diminished when the quantity amounted to 113 

 lb. per acre. Still, the increase in the two cases when 42 and 

 71 lb. were applied respectively was by no means in propor- 

 tion to the quantity of nitrogen applied. 



All we can safely infer, therefore, from these experiments is, 

 that substances containing nitrogen, even when they add nothing 

 to the weight of the turnip crop, may improve its quality by 



