TRACTOR WHEELS.
Page 19
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A Partial Fallacy and the Danger of a Little Learning on the Part of the Salesman. By Henry Sturmey.
ANYalgE WHO HAS looked even casually into the question of farm tractors cannot fail to have remarked upon the wide variation in wheel design. We have almost every possible arrangement of wheels that can be thought of, and of course we have machines which have no wheels at all, but chain track supports instead. Then we have had considerable controversy as to whether a wheel or chain track shall or shall not be arranged to run in the furrow. It is concerning this last point I particularly desire to write in this article.
I know some men who say most emphatically that they would not consider a machine which ran in furrow for one Moment. Others, on the contrary, make a. strong talking point of the fact that such a design is a special feature of their construction. The claim against such an arrangement is that half the weight of half or ntore of the tractor, seeing that it may throw .down a little on the side running in furrow, will pack the soil beneath. Those who so design their machines that they shall run in furrow claim that the traction spuds or strakes, with which their wheels are fitted, act as sub-soil disturbers, so that, whilst they may pack the soil beneath them to a certain extent, the spuds promptly tear it up. Now, we want to look into this matter a little more deeply before forming any fixed opinion for or against the system. if the soil be packed into a smooth, hard and impervious" mass at the bottom of the furrow, it will form a water channel, collecting the water draining from the adjoining surface and conveying it away from the land according to the fall thereof. But one of the objects of cultivation is to break up the soil, thus enabling it to retain its moisture below • the surface, where the roots ...of the growing crops may get at it.
So far, so good. If this theory could be applied generally to all soils, there would Tbe no difficulty whatever in forming an opinion, which it is needless to Bay would be adverse to the running of the wheel in the furrow. But the nature of the soil varies widely in the different localities and possesses divergent characteristics. Consequently, whilst it would, be detrimental to have water drained away from alight, pervious soil, when we come to heavy soils. and particularly heavy clays—as, for instance, those of Essex—exactly the reverse pertains, because here we have an, impervious sub-soil through which the water cannot percolate. In this instance the danger is that it will be held in the soil in too great a quantity. Hence it is desira•ble that the surface water, should be carried off, and since it cannot percolate downwards to any extent, what • are termed " stetch furrows" are provided at regular intervals expressly for carrying this surplus moisture away. It will be seen that what is good for one soil is fatal to another.
Then we have the claim which is quickly made by the enterprising and astute salesman, namely, that the breaking up of this sub-soil by the wheel spikes is good for the land. It is true that sub-soiling, or breaking up of the under surface, is a desirable thing on. some some lands, unless there be a considerable A 2$ h.p.
amountoof iiIip with the driving wheel running in furrow, lio real sub-soiling action takes place. For example, take a machine having conical projections. Th* points sink into the soil below the -wheel, and compressing it round their surface, leave the soil almost as they went ; that is to say, with little, if any, longitudinal movement. Unless there is considerable slip, the effect of such action is to provide merely a series of small-pits or pockets in which the water is able to collect. Furthermore, it must be remembered that, even were the action of the wheel strakes or grippers a true sub-Boiling one, the effect would not be beneficial under all conditions' of soil. Besides, only one fUrrow in three or four, according to the number of ploughs employed, would be so treated. The section of the surface of any field will show a top layer of regularly-cultivated soil resting upon the sub-soil, which may consist of earth very similar in nature to the su.rface soil, but—With the effects of cultivation not in it. On the 'other hand, it may consist of bare rock, or of a coarse soil, which would be detrimental—aImost poisonous—to crops ifdt were mixed with the surface 'cultivation. When 'RI] b-soil are
deep and of the same general character as the surface soil, then both-deeper ploughing and sub-soiling will be generally beneficial, because by breaking up and loosening the. sub-soil to a greater depth, the root fibres of the plants are enabled, as the surface becomes drimi.to penetrate deeper after water. When a sub-soiling attachment is fitted to a plough, it takes the form of a breaker-up of the subsoil surface, by the passing of points or edges through it, and not merely by making holes in it. At the. same time, whilethe surface is broken up, none of the lower earth is brought up to mix with the upper cultivated portion of the soil. A study of the above conditions and requirements emphasizes how fallacious It is for manufacturers and salesmen of tractors to talk glibly of their wheel strakes having a beneficial sub-soiling action, without any reference to the nature of the land on which they are to be used. Such statements only raise derisive smiles among their intending cus.tomers.