Nitrate of Soda as a substitute for Guano. 389 



the Peruvian, the ground of that superiority of course being the 

 same, the excess of phosphates in a given weight of Bolivian 

 guano. 



Mr. Lawes even found that where he had supplied his 

 turnips with superphosphate all the nitrogenous manures he 

 could add to that manure produced no increase in his crop. 



Nitrogenous Manures Mean produce of Turnips 

 added. per acre. 



Tons. Cwts. 



Phosphates, &c v . . 12 8 



,, with 10 cwt. of rape-cake . 13 4 

 ,, with 3 cwt. sul ph. ammonia . ]2 5 

 , . with 10 cwt. rape-cake, and 



3 cwt. ammonia ... 12 4 



Still, though both experience and experiment in the South 

 of England are in favour of giving phosphorus only to turnips, 

 and of reserving nitrogen for the corn crop, it would be rash to 

 assert that our northern farmers are wrong when they use guano, 

 and deference is due to their experience also. We find, indeed, 

 that ammonia sometimes thins the plants, and that it produces the 

 growth of leaf rather than bulb. Possibly from our necessarily 

 late season of sowing, that excess of leaf has not time to mature 

 the weight of bulb, which the cooler skies of the north allow it 

 to ripen by permitting an earlier sowing. Be that as it may, I 

 thought it right to try nitrate upon turnips this year, in order 

 to ascertain whether, in case of need, it might become a sub- 

 stitute for guano with this crop also. Guano itself, however, was 

 not used in the comparison because that being a compound 

 substance, the experiment would have been more complicated. 

 All that I wanted to know was whether the nitric acid of the salt 

 would act upon rootcrops like the ammonia of the birds'-dung, 

 since if this were so the other constituents of guano might be 

 easily added. The nitrate and the ammonia* were applied in 

 equal quantities, and they acted exactly alike ; so much so, indeed, 

 that, though very small doses of each were applied through the 

 water-drill, they both seemed equally to have killed all the seed. 

 However, some stragglers came up, sufficient to fill the rows, 

 which grew very slowly at first, but became luxuriant after- 

 wards, and certainly would have gained bulk for another month 

 if they had not been stopped by a November frost. No differ- 

 ence could be seen in the action of the two manures, and the 

 test of weighing showed their effect to have been nearly identical. 



* The sulphate of ammonia was used, and was well mixed with the soil, so 

 :.'that there was no risk of its escape by evaporation. 



2 D 2 



