These results, if they are to be accepted as correct, must bring about a very considerable change in the generally received views in regard to fertility. We not only see more clearly the connection between a former vegetation and the stored up fertility in our soil, but we also see the importance of vegetation at the present day, as the only means by which the loss of nitric acid is prevented. The more completely the land is covered with vegetation, and the more growth there is, the greater will be the evaporation of water, and the less will be the loss of nitric acid by drainage.
I was not at all surprised to find, that the surface soil of a wood on my farm, was poorer in nitrogen than the soil of an old permanent pasture, to which no manure had been applied for twenty-five years, though during the whole period, the crop of hay had been removed every year from the land. The wood to which I refer is covered with oak, centuries old, and the foliage is so dense that but little underwood or other vegetation can grow beneath it. If both the wood and the pasture were put into arable cultivation, I have no doubt that the pasture would prove much more fertile than the wood land.
In our experiments on permanent pasture, it has been observed that the character of the herbage is mainly dependent on the food supplied. Weeds, and inferior grasses, can hold their own as long as poverty exists, but with a liberal supply of manure, the superior grasses overgrow and drive out the bad grasses and weeds. In consequence of the low price of wheat a good deal of land in England has been laid down to permanent pasture, and much money has been spent in cleaning the land preparatory to sowing the grass-seeds. I have on more occasions than one, suggested that the money employed in this process would be better expended in manure, by which the weeds would be “improved” off the face of the land. While walking over the abandoned portion of these estates I explained my views upon this point to the manager. They were, however, received with the usual skepticism, and the rejoinder that “there was only one way of getting rid of the weeds, which was by the plow and fire.”
There is nothing that speaks to me so forcibly as color in vegetation; when travelling by rail, I do not require to be told that such a farm is, or is not, in high condition, or that we are passing through a fertile or infertile district. There is a peculiar green color in vegetation which is an unmistakable sign that it is living upon the fat of the land. I need hardly say that, in this case, the color of the vegetation gave unmistakable signs of the poverty of the soil; but in the midst of the dingy yellowish-green of the herbage, I came upon one square of bright green grass. In answer to my enquiry I was told that, a “lambing-fold had been there last year,” and my informant added his opinion, “that the manure would be so strong that it would kill anything!” It had certainly killed the weeds, but in their place, some good grasses had taken possession of the soil.
The plan I proposed to adopt was, to spend no more money on tillage operations, but to endeavor to improve the pasture by giving to it the food necessary to grow good grasses, sowing at the same time a small quantity of the best seeds. I further suggested that a flock of sheep should be allowed to run over the whole of the land by day, and be folded there every night—about one pound of cotton-seed cake per head being allowed daily. By this means, as the fold would be moved every day, the amount of manure deposited on the soil could be estimated.
If there were a hundred sheep, receiving one pound of decorticated cotton-seed cake per head, daily, and the hurdles were arranged to enclose a space of twenty-five by twenty yards, in the course of ten days an acre of land would have received manure from one thousand pounds of cake; which amount would supply seventy-seven pounds of nitrogen, sixty-eight pounds of phosphate of lime, and thirty-two pounds of potash. This amount of cake would cost about sixteen dollars.
As regards the value of the cake as a food, it is somewhat difficult to form an estimate; but it takes nine or ten pounds of dry food—say roots, cake, and hay—to produce an increase of one pound of live weight in sheep. The cake has certainly a higher feeding value, than either hay or roots, but I will here give it only the same value, and consider that one hundred and ten pounds of increase of the animal was obtained by the consumption of the one thousand pounds of cake. The value of the increase of the live weight would be in England fully eleven dollars, leaving five dollars as the cost of the manure. Now the cake furnished seventy-seven pounds of nitrogen alone, which, if purchased in an artificial manure, would have cost nineteen dollars; and the other substances supplied by the cake, would have cost from four to five dollars more. The manures required, therefore, would be obtained much more cheaply by this than by any other process.
Labor would be saved by not cultivating the land. Manure would be saved by substituting vegetation which grows under or above ground, almost all the year round. And, by feeding the stock with cake, the necessary fertility would be obtained at the lowest possible cost.
It is probable that the land would require this treatment to be repeated for several years, before there would be a fair growth of grass. The land might then be broken up and one grain crop be taken, then it might again be laid down to grass.
Hitherto, I have considered a case where fertility is almost absent from the land, this, however, is an exception, as agriculture generally is carried on upon soils which contain large stores of fertility, though they may be very unequally distributed. By analysis of the soil we can measure the total amount of fertility which it contains, but we are left in ignorance in regard to the amount of the ingredients which are in such a form that the crops we cultivate can make use of them.