DEEP PLOUGHING.
Page 9
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A New Attachment for Breaking Without Bringing Up and Aerating the Subsoil but it to the Surface.
THE QUESTION of deep ploughing has been raised by " Agrimot " in THE COMMERCIAL MOTOR, and there is no doubt that the question is one of considerable importance. It is one to which I have been giving some attention lately, because, in conjunction with an American inventor, I am patenting some improved appliances bearing upon the issue. I ntay mention that the inventor in question, Mr. J. B. Jobson, has been working on the problem for a considerable number of years, and has already achieved some striking successes.
Value of the Subsoil.'
I do not think that the course advocated by " Cultor," viz., straight ploughing to such a depth as 12 ins., and bringing the whole of the subsoil to the top, is a sound one. Undoubtedly there is pronounced conservatism and prejudice in favour of old method; or old ideas, on the part of the fanning community, but this very widespread and, indeed, universally-held opinion as to the disastrous effect of bringing the subsoil to the surface has some foundation.
It depends on the subsoil. As a broad principle, however. I believe the old theory to be correct, and that Mr. Edge's experiment is one of the exceptions proving the rule. Nevertheless, to go on as we are doing, and have been doing for centuries, that is, -merely ploughing up the same old surface soil to the same depth year after year, is inefficient, and is far from being productive of the best results. It is inefficient For several reasons. For one thing, the plant rootage requires depth and requires moisture.
Delicate plant roots cannot penetrate solid, impervious soils. Where they do get down into the subsoil is where a crack exists, however small. But the old subsoil in most cases is merely a packed mass, and, as a rule, is loaded with moisture. As soon as the .moisture has been taken out of the surface soil in which the plants are growing, the plants look for further moisture in the subsoil, and because the latter is, as mentioned, just a solid mass, they are unable to reach it. To break up the subsoil, therefore, and to break it up finely, secures the desired effect, and also ensures a great continuity of the moisture in the soil.
A large proportion of the moisture in land is lost by evaporation, and the water, before it can be evaporated, i must be brought to the surface. Whereverthe soil s solid, this is done through the effect of capillary attraction. When the soil is broken up, as the surface soil should be, the capillarity is broken and the moisture is not able to reach the surface. Thus, as . it cannot be evaporated, it remains in the soil ready for the plant roots when they can get down to it. This is why packing of the soil by heavy tractors does so muchtdamage. It increases the capillarity of the soil and leads to greater evaporation, whilst at the same
time it prevents root penetration.
Breaking lip the Subsoil.
Again, the subsoil usually contains nitrates, which are of fine fertilizing value, for which the plant roots struggle valiantly. If this subsoil be broken up and the plant rootsbe enabled to get down into it, they can feed upon these nitrates. Moreover, the breaking up of the subsoil has the further effect of bringing its particles in contact with the air, and this aerating effect is beneficial in more ways than one. On the other hand, the subsoil does not contain the humus and other constituents of the top soil. Consequently, whilst it is desirable that the chemical constituents contained therein should be obtainable by the plants, it is not desirable that what is generally
termed sour soil, which is devoid of many of the other desirable constituents, should be brought to the surface. The difficulty in the past has been to secure a full and thorough breaking up and aeration of the subsoil without bringing it to the surface, to the detriment of the superimposed pOrtions, and this Mr. Jobson's patent plough effects. As will be seen from the annexed illustration it is totally different in construction from the ordinary mould-boardtplough. Instead of slicing tip the soil and turning it over more or less in a mass, it meets it at quite a different angle and breaks it up to a, much greater degree. This relates to both the surface soil and the subsoil, and, as will be seen from the sketch,. the plough is double, forming an under share and an upper share, with an aperture or space between them.
The under share, which is a subsoller, works in advance of the upper one, with the result that, just when the upper layer of soil has been lifted, the -lower layerof subsoil is being turned right over beneath it through the aperture between the two ploughs. As with the top surface, it is also considerably broken up. At the same time, it is being aerated. In the result, as will be seen, the subsoil is as fully turned over and broken up as the top soil, but it still remains subsoil, and no particle of it reaches the surface.
The effect of this will be readily perceived. The plant rootage having penetrated to the subsoil, is enabled to travel downwards without effort, and to extract the moisture and nitrates therefrom. If this breaking up of the.subsoil is continued year after year, preferably twice a year, the root growth, which penetrates the subsoil, will itself in time add humus to the subsoil. Consequently the effect in the long run will b.e to deepen the productive soil, the soil and the subsoil gradually assimilating to each other. The system, so tar as this plough is concerned, has been in commercial use now in all parts of the U.S.A. for the last two years. There is ample testimony to show, not only that the plough itself is much lighter in draft, although ploughing ideeper than the ordinary type ef plough, but that considerable increase in crop production is obtained by.its use, and that it will produce a larger yield at a lower cost. S.