340 A G R I C U L T U R E [SUCCESSION merely raked out and left entire on the surface, as would happen but for this preliminary rolling. The grubbers are followed closely by harrows and a light roller, and these again by the grabbers ; but this time with seven tines on instead of five, after which a sufficient tilth is usually obtained. All this is on the supposition that the land is clean when these spring operations are commenced ; for should it be otherwise, it is usually better to begin with the grubber on the stale winter furrow, and to get rid of the weeds, before using the plough. If it is found necessary to plough near to the time of sowing, then the harrow and roller must keep pace with the ploughs in order to retain moisture and prevent the formation of clods. The Nor wegian harrow is the proper implement to use in such cases. Let it ever be borne in mind that if the soil is cleaned and sufficiently disintegrated, the less working it gets at this stage the better. It may be well indeed to remind the reader that although the fallowing process can most conveniently be gone about during the period which intervenes betwixt the removal of a grain-crop from the ground and the sowing of the succeed ing root-crop, and on this account is often spoken of in a loose way as being performed " in preparation for the root- crop," it is a fallacy to regard this laborious and costly process of tillage and cleaning as undertaken solely or mainly for the benefit of the turnip or other root-crop, then about to be sown. The other crops of the rotation benefit by it in a far greater degree, and it would be re quired on their account although turnips were not grown at all, as may be seen in the case of clay lands with their periodic naked fallows. It is the overlooking of this fact which has led people to charge the whole cost of this fallow ing process, and of all the manure then applied to the land, against the turnip-crop, and then to represent this crop as the most costly one which the farmer grows, one which often yields him less than it cost to produce it. Undoubt edly the cost of the fallow must be charged equally against all the crops of the rotation. Summer or Naked Fallow. Having thus described at length that modification of the fallowing process by which the soil is prepared for the sowing of green crops, we shall now, as proposed, speak of that prolonged form of it called a summer or naked fallow. From the facilities now afforded, by means of tile-draining and portable manures, for an extended culture of green crops, this laborious and costly process, which in its day was justly regarded as the very key to good and profitable farming, is now restricted to the more obdurate clay soils, or to cases where draining and other modern improve ments are neglected. The manifold advantages of having abundant crops of turnips, or mangel-wurzel, instead of naked fallow, sometimes tempt the occupiers of clay soils to push the cultivation of these crops beyond due bounds. We know of cases where, after large expenditure in draining, the cultivation of turnips has been carried to such an extent, and conducted so injudiciously, that the land has got foul and soured, and its gross produce has been reduced below what it was while the laud was undrained, and under a regular system of all but exclusive naked fallows. However thoroughly drained, clay soils retain their ticklish temper, and are so easily disconcerted by interference during un favourable weather, that the preparing of them for the cultivation of root-crops, and still more the removing of these crops when grown, is at best a hazardous business, and requires to be conducted with peculiar tact. Judicious farmers, who know by experience the difficulties that have to be overcome in cultivating such soils, are of opinion that all that can yet be ventured upon with safety is to prolong the period of the naked fallow s recurrence, rather than entirely to dispense with it. After a series of alternate grain and cattle crops, it is accordingly still their practice to wind up with a summer fallow, by which they rectify unavoidable defects in the tillage of preceding years, and put their land in good humour for entering again upon a fresh course of cropping. This process is begun by a deep ploughing in autumn, in performing which the land is gathered into ridges, that it may be kept as dry as possible during winter. When the more urgent labours of the following spring are so far dis posed of as to afford leisure for it, a second ploughing is given to the fallow, usually by reversing the furrows of autumn. This is followed at intervals by two cross-plough- ings, which are made to reverse each other, in order to keep the land level. As it is the nature of these soils to break into lumps, under the action of the plough, rather than to crumble down, the clods thus produced get so thoroughly parched in dry w r eather, that root-weeds enclosed in them are killed by sheer desiccation. To further this cheap mode of getting rid of them, the land is not rolled, but stirred by the grubber and harrow as frequently as possible, so as to expose the clods freely to the drought. We know by ex perience that fallows can be cleaned effectually by thus taking advantage of the tendency in clay soils to bake excessively under exposure to the hot dry weather which usually prevails in June and July. Should the season happen to be a showery one, this line of tactics must needs be abandoned, and recourse had to the judicious use of the grubber, Norwegian and common harrow, in order to free the weeds from the soil, and then clear them off by raking or hand-picking. This is more costly, and, as we believe, less beneficial to the soil than the simple method first noticed, which should therefore be attempted in the first place. As in hay -making, much can here be done in a few favourable days, by keeping grubbers and harrows at work, and turning the clods frequently. When farm-yard dung is to be applied to such fallows, it is desirable that it should be carted on and ploughed in before July expires. In applying it, two methods are followed. That usually adopted is, after marking off the ridges, to put down the dung in small heaps, at regular distances, and forthwith to spread it and plough it in. In the other, the land is formed into ridgelets, running diagonally across the intended line of the ridges, and the dung is enclosed in them in the manner to be hereafter described in treating of turnip culture. In either way,- after the lapse of several weeks, the surface is levelled by harrowing, and the land is gathered into ridges by the last of this series of ploughings, hence called the seea-furrow. When lime is to be applied to such land, this is the stage of the rotation which is usually chosen for doing so. It is spread evenly over the surface, imme diately before the last ploughing. In finishing off this fallowing process, it is necessary, on undrained lands, to be careful to clean out the ridge-furrows and cross-cuts, in anticipation of winter rains. But if such land is worth cultivating at all, it is surely worth draining, and this operation once thoroughly performed, puts an end to all further solicitude about furrows. CHAPTER IX. SUCCESSION OF CHOPS. Section 1. Rotation necessary. There are few agricultural facts more fully ascertained than this, that the growth, year after year, on the same soil, of one kind of plants, or family of plants, and the removal from it, either of the entire produce, or at least of the ripened seeds of such plants, rapidly impairs the general fertility of that soil, and, in particular cases, unfits it for bearing further crops of the kind by which it has been ex
hausted. The explanation of the causes of this phenomenon
