"The various manures compounded by chemists and manufacturers, should also engage your careful attention. They should not be recklessly thrown aside as humbugs, without trial or investigation, nor adopted and extensively used with blind confidence in their efficacy. I have used many of these manures by way of experiment, and the profit realized upon them has not justified me in enlarging my operations. Poudrette, manufactured in Baltimore; Bommers manure, Chappel's fertilizer and Kentish & Co.'s prepared guano, (used, it is true, upon a small scale,) have not realized the promises made in their behalf. Yet I would by no means discourage the praiseworthy efforts of the manufacturers, and hope they will persevere until, by lessening the bulk and increasing the power of their compounds, they may be able to prepare an article that for cheapness, convenience of application and efficacy, shall equal or surpass the best Peruvian guano."
That desideratum, Professor Mapes believes he has already attained by the addition of superphosphate of lime to the Guano, making a compound of two-thirds of the latter to one of the former, more valuable by weight than the pure article. That being the case will greatly increase the consumption of Guano, and greatly improve the condition of all that class of farmers who desire to make their poor lands rich.
Of the use of lime, Mr. Newton has the following testimony, which we embody here for its great practical value.
"Calcareous matter is the great want of most of our lands, and in some form is essential to permanent improvement. It should be regarded as the basis of all our operations, and never to be dispensed with for any substitute. From long experience in the use of lime, I am satisfied that the French plan, of light and frequent dressings, is not only much more economical, but much safer, in our climate, than the heavy dressings common in Great Britain. Fifty bushels of slaked lime to the acre, I have found amply sufficient for any of our lands, and a greater quantity often attended with injury to the soil and crops, whilst twenty-five bushels will answer every purpose on thin lands, deficient in vegetable matter. Ashes, bone dust, and the various marine manures that abound on the shores of the Chesapeake and its tributaries, will be found important auxiliaries in the work of 'keeping your lands rich,' whilst the necessity of clover and the proper grasses, to any system of permanent improvement, is too obvious to require comment."