202 RELATION OF THE WEIGHT OF THE CROP 



nitrogen contained in the several salts employed in them. Hav- 

 ing already shown the absolute increase of crop obtained by 

 the use of each, I shall here calculate and exhibit in a tabular 

 form only the increase obtained by the use of each application, 

 supposing the quantity of nitrogen added by it to have been 

 one hundred pounds. 



1. In Mr Main's experiment upon oats, a hundred pounds 

 of nitrogen, in the form of 



Increase for every 100 Ib. of nitrogen 



applied. 

 Grain. Straw. 



Sulphate of ammonia, gave . 37f bush. 7J cwt. 



Sal-ammoniac, . . . 47f ... 14^ ... 



Nitrate of soda, ... no increase none 



This experiment lends no support whatever to the opinion 

 that the sensible increase of crop caused by these applications 

 on the same soil has a direct relation to the percentage of 

 nitrogen they respectively contain. 



2. In Mr M'Lintock's experiment upon oats, a hundred 

 pounds of nitrogen, in the form of 



Increase for every 100 Ib. of nitrogen 



applied. 

 Grain. Straw. 



Sulphate of ammonia, gave . 42J bush. 124 stones 



Muriate of ammonia, . . 52^ ... 176 



Nitrate of ammonia, . . 63 ... 205 



Nitrate of potash, . . . 196 ... 684 ... 



Nitrate of soda, . . . 55 J ... 240 ... 



In the above numbers, also, there is no similarity, so that we 

 are forced to one of two conclusions either that the experi- 

 ments are worth nothing, or that the effect of these applications, 

 when made to corn crops, is not determined by the proportions 

 of nitrogen they respectively contain. 



3. In the experiments upon grass made at Barochan, on 

 three different fields, one hundred pounds of nitrogen, in the 

 form of 



Increase for every 100 Ib. of nitrogen 



applied. 

 1. 2. 3. 



Sal-ammoniac, gave 63 stones 46j stones 20j stones 



Sulphate of ammonia, 78 ... 39 ... 30 



Nitrate of potash, . 160 ... 119 ... 70 



Nitrate of soda, . 113 ... 82 ... 80 ... 



