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XIV. — Comparison of Guano with other Manures. — By David 
Barclay, M.P. 
To W. Miles, Esq., M.P. 
My dear Sir, — The very extensive use of guano as a manure, 
and the ])rospect of very large supplies from Peru and the West 
Coast of Africa, induced you to recommend to the Council of our 
Society, that some of its members should undertake to test the 
relative value of the ditterent kinds, including Potter's artificial 
guano, as compared with farm-yard manure ; and Humphrey's com- 
pound was subsequently proposed to be tried at the same time. 
1 undertook, for one, to make these experiments. We were in- 
structed to sow Skirving's Swede, and to apply 20 tons of farm- 
yard dung to the acre, 3 cwt. of guano, and such quantities of Pot- 
ter's guano and Humphrey's compound as the proprietors might 
desire. 
The land which I selected for making these experiments is a 
light flinty loam of uniform quality, with a chalk subsoil. Long 
strips of an acre each were measured with exactness, and admitted 
of 16 rows of plants in each strip, at the distance of 26 inches be- 
tween the ridges. Four acres were drilled on the 22nd of June; 
the fifth acre, with Humphrey's compound, was delayed for want 
of seed till the 26th. Instead, however, of 20 tons of dung as 
proposed, only 12 tons were applied ; of the African and Peruvian 
guano, and of Humphrey's compound, 3 cwt. each ; and of Potter's 
artificial guano 4 cwt. by his desire : all were mixed with 9 cwt. of 
ashes, and drilled in with the seed on the Scotch system. The 
5 acres were twice hoed. About the middle of January, 1845, 
2 entire rows out of the 1 6 in each strip were raised, trimmed, and 
weighed, and the weights, multiplied by 8, must have given 
the weight per acre with accuracy, as, owing to the great length of 
the rows, no material departure from exact results could take place. 
The following table will show the cost of each manure, the pro- 
duce per acre, the value estimated at 155. per ton, also the cost of 
each manure, and its application per ton of roots. 
The long drought which we experienced will account for the 
small produce per acre, and may possibly have exercised a greater 
influence on one description of manure than on another ; I can- 
not, therefore, consider my experiments so decisive of the relative 
value of the manures as if the season had been more propitious : 
but should the trials undertaken by others correspond in their re- 
sults with mine, information will be elicited which may be useful 
to the agricultural body. It was remarked that the drought ap- 
peared to have the most influence on the acre manured w ith dung, 
turning the leaves more yellow than on the other strips dressed 
