0)1 Nitrate of Soda. 



361 



Guano, 1 cwt. 

 Nitrate, 1 cwt. 

 Undressed 



Gnano, 1 j cwt. 

 Nitrate, cwt. 

 Undressed 



The difference as against guano is insignificant ; and since 

 guano further contains phosphorus which is certainly, and potash 

 which seems sometimes, useful to corn-crops, it is difficult to see 

 why cubic nitre at 16Z. should ever have been preferred to guano 

 at 9Z. by farmers who could purchase either. Still there must 

 be some reason, since both are employed upon corn-land in 

 England. Unfortunately we have very few comparative experi- 

 ments between the two manures,— and what is more unlucky, 

 those few, collected by Professor Johnston in his excellent lec- 

 ture,* were chiefly made during a summer so dry that they only 

 afcted by chance. Such contradictory results as the following 

 give us no information : — 



Produce per Acre. 

 Top-dressed with Eushels of Wheat. 



46 . Erskine, Renfrewshire. 

 . 54 

 . 44 



45 , Seisdon, Worcestershire. 

 . 41 

 . 39 



The only later experiment upon corn which I am acquainted 

 with is one made at this place, and published by me last year, 

 in which a single cwt. of nitrate surpassed two cwts. of guano.j 



Bushels of Wheat. Increase. 



Undressed . . .21 



Guano, 2 cwt. . ..24 . .3 



Nitrate, 1 cwt. with salt . 25i . . 4i 



This, however, was also made in a dry summer, and, though it 

 was carefully made, I have no doubt that the proportion of 

 increase is unfair towards the guano. In the absence, then, of full, 

 direct, experimental comparison, we must have recourse to the 

 best evidence on the respective powers of these two manures ; 

 and the result will, I trust, be found to warrant some minuteness 

 of investigation. Now Mr. Lawes informs me, as the result of 

 his long experience, that he would expect on the average from 

 one cwt. of guano, not from two as in this trial, three bushels of 

 wheat. But the increase from the Nitrate is also low. Taking 

 again the best evidence, I have ascertained from an eminent 

 agriculturist, the manager of Lord Leicester's farm, at Holkham, 

 Mr. Keary, that in that neighbourhood, which has not lost the 

 impress of Mr. Coke, cubic nitre is largely used, and gives an 

 average increase of six bushels per acre for a dressing of from 

 three quarters to an entire hundredweight. We may assume six 

 bushels then as the product per cwt. of Nitrate on moderate land 

 in fair order. On land in the highest condition it would give 



* Johnston's Lectures on Agricultural Chemistry, p. 281. 

 t Journal, vol. xii., p. 202. 



2 B 2 



