Manures and their Uses

Abstract

THIS is a hand-book for farmers and students, and may be described as a smaller and less ambitious successor to the treatise on manures, by the same author, reviewed some months ago in NATURE. The principal value of this latter work consists in the direct information it contains as to sources of phosphatic, potassic, and nitrogenous manures, including guanos, in all parts of the world. The analyses, localities, amounts imported, and values, are all interesting facts for farmers, and this little book may well take its place in an agricultural library as supplying knowledge which otherwise might need research through many scattered sources of information. When, however, we consider the book as a means for imparting sound views on agricultural principles, we must advise caution on the part of the reader. Dr. Griffiths is one of those teachers who are infected with an inordinate affection for chemical manures. He believes, with M. Ville, that “the farmer who uses nothing but farmyard manure exhausts his land.” Now, a man who starts with such an obvious fallacy can scarcely get into the right path. This doctrine is contrary to science and practice; and until Dr. Griffiths relinquishes it he cannot hope to enjoy the confidence of any farmer. We venture to put the matter in two or three positions from which it can be clearly viewed. Dr. Griffiths says, “This [farmyard] manure is erroneously supposed to contain all the necessary plant-foods required for the growth of crops.” Erroneously ! why, farmyard manure at least must contain all the constituents of straw, for it is largely made of straw. Similarly, it must contain the elements of turnips and root crops, when it is composed of them in no small proportion. Also it must contain the constituents of corn, because all meals and cakes which are consumed by cattle, and all hay, which is also consumed by cattle, contain the constituents of corn in the form of nitrogen, phosphorus, sulphur, potash, lime, magnesia, &c. Whether looked at chemically or approached through pure reasoning, it is clear that farmyard manure is the true restorer of fertility, the very milk of plants, the very life-blood of the soil, if such an expression may be allowed. Farmyard manure during its decay has its elements liberated from organic combinations gradually, and when wanted, as well as in a condition so available for the food of plants, that as a manure it is inimitable. No other manure can in all cases be applied to all crops with the same marked effects. It is strange that farmyard manure alone acts promptly and certainly upon leguminous crops such as beans, peas, and clover. No chemical manure, whether nitrogenous or phosphatic, can be relied upon to affect these crops, and yet farmyard dung tells upon them at once. Dr. Griffiths lays stress upon the fact that animals retain phosphates and nitrogen for the formation of bones, nerves, and muscles, and therefore to some extent rob the land. This fact is, however, entirely over-ridden by the customary importation of extraneous matter on to the farm in the form of foods purchased. The amount of phosphates and nitrogen removed by animals in their bodies is as nothing compared to the tons of cake, meal, hay, and even roots which are imported. Neither must we forget the town manure which is so often bought by farmers, and which will compensate for such a loss as that which Dr. Griffiths fears. Too much prominence is given to chemical manures, and too little importance is attached to stock-feeding as a manurial agency. Dr. Griffiths quotes many writers upon matters on which they are scarcely to be regarded as authorities. On such matters he might just as well have told us his opinion, instead of backing it up with the name of a solicitor who has been dead for years and whom nobody now knows of. Neither is an agriculturist, pure and simple, an authority on a chemical point such as the valuation of farmyard manure on the basis of its chemical constituent parts.

Manures and their Uses.

By Dr. A. B. Griffiths. (London: George Bell and Sons, 1889.)