Nitrate of Soda as a substitute foi' Guano. 



385 



forget th;it, besides Nitrogen, guano contains phosphorus and 

 potash. These ingredients, however, can be easily added to each 

 ton of saltpetre, if wanted, at a cost of 1/. 135. 9tZ. for phosphorus, 

 and 145. ^d, for potash ; but the potash I believe would be rarely, 

 and the phosphate not often, required. 



Large as is the importation of guano, the crops to which it is 

 applied are few, and the comparison of it with nitrate of soda as 

 applied to those crops, need not be tedious, for guano is used 

 chiefly as follows : — First, as a top-dressing for grass ; next, drilled 

 with wheat in autumn, or sprinkled over wheat as a top-dressing 

 in spring ; lastly, for turnips. 



The practice of top-dressing grass can hardly, indeed, be called 

 a practice as yet. The careful experiment directed by H.R.H. 

 Prince Albert to be made on the Windsor Farm, and recorded 

 in this Journal,* while it proved that the use of both the leading 

 nitrogenous manures is profitable upon grass, gave the advantage 

 to guano. This advantage might have been accidentally due to 

 the heavy rains which, prevailing at the time, may have washed 

 down the nitrate below the roots of the grass. But information 

 which has just reached me from an eminent Scotch farmer, Mr. 

 Hope, of Fenton Barns, confirms the Windsor experiment. 

 Mr. Hope's opinion derives great weight from the extent of his 

 experience, for he occupies 660 acres, and states moreover that, 

 zinless portable manures are applied at the rate of 11. per acre over 

 the whole farm^ he cannot continue to farm at a profit, \ He writes 

 to me thus : — 



" For many years I have been in the habit of applying nitrate as a top- 

 "drcssingf for clover and rye-grass, to be cut as green food and for hay. I 

 generally sow it broad-cast on the grass early in April. I have Ibund that 

 180 lbs. per imp. acre was a fair allowance, but that it paid better, from a 

 heavier crop being obtained at less expense, to give only 90 lbs. nitrate and 

 180 lbs. of Peruvian guano, this being also better than double the quantity of 

 guano by itself." 



This result of Mr. Hope's experience is intricate, but appears 

 to show on the one hand that, on his particular soil, the nitrogen 

 of the saltpetre requires to be aided by the phosphates, perhaps 

 even by the potash contained in guano, and to prove on the other 

 hand that a small dose of those salts is sufficient, while the 

 superior fixity of the nitrogen contained in the nitrate com- 

 pensated its greater quantity in the guano. For we know that in 

 dry weather a total loss by surface exhalation has sometimes 

 attended the use of guano ; and as upon grass-land guano of 

 course cannot be harrowed in, it would appear thriftier to use 

 nitrate only, with the addition of superphosphate, and, if re- 



* Journal of Eoyal Agricultural Society, xiii., p. 347. 

 t See Mr. Stevenson's account of Mr. Hope's farm in the present number, p. 317. 



