The manuring of grass is a question of very great interest and importance, but is, at the same time, beset with peculiar difficulties. Grass is grown under two conditions—first, that grown on soils exclusively set apart for its continuous growth (permanent pasture); and secondly, that grown for the purpose of being converted into hay and of providing pasture in the ordinary rotation of crops (rotation seeds). The manuring of the former is somewhat different from the manuring of the latter.
Effect of Manure on Herbage of Pastures.
The nature of the herbage growing on pasture is very much influenced by the manure applied. This, indeed, is one of the most noteworthy features connected with the manuring of grass, and has been especially observed in the Rothamsted experiments, where the influence of the different manures on the various kinds of herbage has been investigated with great care. The herbage constituting pasture is, as every farmer knows, of a varied description. We have in pastures a mixture of plants belonging both to the gramineous and leguminous classes, as well as a variety of weeds. Now the result of the application of different manures tends respectively to foster the different kinds of grasses. Thus when one kind of manure is applied, grasses of one kind tend to predominate and crowd out grasses of another. It has been found that the more highly pasture-land is manured the simpler is the nature of its herbage (that is, the fewer are the different kinds of herbage growing on it). Unmanured pasture, on the other hand, is more complex in its herbage. The result is, that the application of manure to pasture-land is attended with certain dangers. To maintain good pasture it is desirable to effect a proper balance between the different kinds of grasses. For this reason permanent pasture may be said to be, of all crops, the least commonly manured. As a rule it is only manured by the droppings of the cattle and sheep feeding upon it.
Influence of Farmyard Manure.
It is found that the influence of farmyard manure upon the composition of the pasture does not tend, to the same extent, to the undue development of one type of herbage over another; and in this respect it is probably to be preferred to artificial manures.
The same reasons, however, do not hold with regard to rotation seeds, where an abundant growth is desired, and complexity of herbage is not so important. A further reason which exists for the manuring of meadow-land is the greater impoverishment of the soil taking place under such conditions. As illustrating the influence of different manures on different kinds of herbage, it may be mentioned that in New England wood-ashes, a manure commonly used there, have been observed, when applied to pasture, to bring in white clover, and that the application of gypsum had the same effect. An explanation of this fact may be found in the influence of potash on leguminous crops. The chief value of wood-ashes as a manure is due to the large percentage of potash they contain, while the value of gypsum is probably to be accounted for by the fact that it has an indirect action, and sets free potash from its inert compounds in the soil. In the Rothamsted experiments this point has been verified, and potash has been shown to increase the proportion of leguminous plants on a grass-field. Nitrogenous manures, on the other hand, more especially sulphate of ammonia, have been found to increase the proportion of grasses proper, and to diminish the proportion of leguminous plants. The effect of farmyard manure, while less marked in inducing simplicity of herbage, has a similar effect to sulphate of ammonia; while phosphates and other mineral manures exercise an influence similar to that of potash. Mixtures of mineral and nitrogenous manures gave the largest returns obtained, but their influence was to increase the proportion of grasses proper. Sewage irrigation also tends chiefly to develop grasses.
Influence of Soil and Season on Pastures.
Manures are not the only factors influencing the quality of pastures. The nature of the soil, as well as the age of the pasture and the character of the season, exert a very considerable influence. Grass growing on damp or badly drained soil is invariably of poor quality, the coarser grasses predominating. Old pastures, again, are generally of better quality than new ones.
Nitrate of soda is a common manure for grass grown for hay. It is often applied at the rate of 2 or 3 cwt. per acre. It is best, however, to apply it in smaller doses. On soils where lime is abundant, superphosphate may be applied, if necessary, at the rate of 2 or 3 cwt. per acre, or bones at a similar rate. Basic slag has been found to meet with good results as a manure for grass-land, especially where the soil is rich in organic matter.