82 REPORTS OF EXPERIMENTS WITH DIFFERENT TOP-DRESSINGS. 



nitrogen as both acid and base in the nitrate of ammonia, and 

 thus there is a base or an acid, as the case may be, which is in 

 itself valuable ; as in the nitrate of soda there is the whole of the 

 soda, besides the nitrogen, by the quantity of which the salt has 

 been valued, and the more lasting effect of these dressings probably 

 arises from this cause. 



The nitrate of soda has increased the first crop more than the 

 nitrate of lime, and nearly as much as the nitrate of ammonia ; 

 they, both of them, have had rather a better effect on the second 

 crop than the nitrate of ammonia, while on that crop they are 

 about equal to the sulphate of ammonia and the chloride of 

 ammonium. They have not improved the first crop, however, quite 

 as much as the chloride of ammonium, though they have done so 

 more than the sulphate. Thus, as these nitrates stand in their 

 results between the two ammonia salts, it cannot be inferred that 

 nitrogen, in the form of a nitrate, is either more or less valuable 

 than nitrogen in the form of ammonia.. The Peruvian guano has 

 been far the most productive and profitable of any of the dress- 

 ings ; but, as stated in remarking on the first and second crops in- 

 dividually, it is unfair to compare it as a source of ammonia alone, 

 owing to the manurial value of the phosphates and other salts 

 which it contains. These results, however, show that these salts 

 are very valuable to rye-grass and clover, when there is rain soon 

 after the guano is applied. 



The mixed dressing of nitrate of soda and sulphate of ammonia 

 has given the heaviest total crop after the guano. On the first 

 crop it stands fourth best in its results, giving 4 cwt. less than the 

 guano, and 1J cwt. less than the chloride of ammonium. On 

 the second crop it appears to have done no damage, or rather has 

 made up for the damage done to the clover by increasing the grass 

 crop. 



The chloride of ammonium in solution did not produce such a 

 good first crop as the chloride of ammonium applied in powder. 

 This is probably owing to its having scorched the plants more at 

 first, for the second crops are almost equal. From this it may be 

 inferred, that both the nitrate of lime and nitrate of ammonia 

 might have produced larger first crops had they been applied in 

 powder, or in more dilute solutions, as they are both caustic salts. 

 Most experiments on the action of ammonia salts on clover ap- 

 pear to have shown that they are injurious to it. Yet in these, 

 there can be no doubt that the first crop of clover stood higher and 

 looked better in the plots which had received some nitrogenous 

 dressing, than on the blank plots. This order was certainly, on 

 the whole, reversed on the second crop. 



From the irregularities of crop noticed on the various plots of 

 the same experiment, there is no doubt that it would be more satis- 

 factory were each experiment tried on six or eight plots, instead 



