GARDEN AND ORCHARD.

New Zealand Herald, Volume LXIV, Issue 19638, 17 May 1927, Page 15

GARDEN AND ORCHARD.

THE VEGETABLE GARDEN. TRENCHING THE SOIL. BY B.T.R. The autumn season is rapidly drawing to a close, and winter, with its usual accompanying wet weather, will soon be here. If the wet wintry conditions should happen to be prolonged into what oupht to be the spring season, fcho garderer may find it a difficult matter to get his ground prepared for the spring crops in a thorough manner in time. Any gardener who has the foresight to take steps to avoid such a contingency will be wall rewarded for his trouble, if it might be called such. In any case, even if the early part of spring is not wet, the preparation of the soil will be found much easier if something is done before the winter sets m. The best method of setting out in this direction is to trench all unoccupied ground when the first opportunity offers. Gardeners have been advised to sow all spare ground with some green crop, which is an excellent practice. In preparation for such a sowing, however, deep working of the soil, by means of trenching, is most desirable. Ground should be worked over again when spring comes, and the green manure turned under. The most efficient method is, again, to trench the plot. It might be argued that it is unnecessary to trench before winter if it is to be clone in spring in any case. There is something to be said in favour of the pre-winter operation, however, which makes it important. If the subsoil is of a clayisb nature it becomes very much compacted if it is not loosened up for several years. It is consequently practically impervious to the drainage water. Difficult Drainage. As a result of this state of the subsoil, the rain water, which is so plentiful daring winter, finds difficulty in draining away. The ground, therefore, is kept in a more or less sodden condition throughout the wet season. In order to prevent this state of affairs as far as possible, the trenching operations should be performed before the winter, for the loosening of the subsoil, such as is effected by doing this, results in improved drainage. Following on this improvement and as the direct outcome of better drainage comes a more rapid drying up of the soil. This often makes it possible to work the plot (if it is desired to do so) when an untrenched piece of ground would still be sodden. Furthermore, the rapid drying up of the ground will make it possible to make the final preparations sooner than would be the case otherwise, and so the various crops could be put in earlier. It will be seen, therefore, that the two trenchings are, on the whole, desirable for the above reasons alone. Another great advantage lies in the fact that the texture of the subsoil is improved to a greater extent by beinj stirred up twice than it is by being worCed once only. With tap-rooted crops fhis is important, as it allows of, and even encourages, a more extensive root development. A word or two on how to trench will, perhaps, be of assistance in guiding gardeners to proceed in the correct way m performing this operation. The tools which are required are a spade and a fork. With the spade the first spit across! the whole width of the plot is dug out and carried to the rear of the plot, oeing deposited behind the rear boundary of th(S area that is being trenched. A second 6pit should also be transferred, but it is not essential to do this. It is advisable, however, as it makes the trenching a much easier operation, and also it can be performed mora thoroughly. Speaking from experience the writer can recommend the wider trench. Loosening the Subsoil. By means of the fork the subsoil, which lias been made accessible by transferring the topsoil, should then be effectively loosened by being "dug" over. This having been completed the third spit of topeoil should then be dug with the spade end thrown to the position originally occupied by the first spit. Likewise the fourth spit is removed to where the second gpit was. The third and fourth spits of subsoil are now exposed and these may be forked over, after which they should be covered with the next two spits of topsoil. This procedure should be followed until the last two spits of subsoil have been stirred up. The soil which was used at the commencement is then used to fill in this trench, and the operation is comThe procedure described above is not the true method of trenching, but is_what is known -aa bastard trenching. It is, however, tli© method most commonly in vogue. The true method of trenching may be used onlv on soils which have topsoil of a depth cf two spade depths or . more, for when using this system the second spade depth (which is usually subsoil). is brought to the surface. If this were done or, the average garden soil the results would be disastrous, for the bringing of inferior soil to the top would starve the majority of crops which are surface feeders. In this fact lies another auvantai'e of the bastard trenching system, viz., thfit it is possible to worn the subsoil without in anv.way impoverishing the topsoil by introducing inferior soil into it. Although it is not very often that true trenching is carried out, yet it may be useful to a few who are fortunate enough to possess a good deep topsoil, to hew to set about this operation. With bastard trenching the soil is worked to two spade depths, but with true trenching it is loosened to a depth equal to three spades. The advantage of the true method, where it can be employed, is that fresh supplies of good soil are brought to the top. Method of True Trenching. The method which is followed with true trenching is to remove, first, the nrst width of topsoil and place it to the rear • of the plot. The second laver of soil is also removed and deposited m a separate heap. The third layer is then forked up, and the next lot of topsoil is dug up and thrown on to it to become the second laver of soil. The next second layer of soil is then placed on top of the lajer of topsoil. which was dug jnst previous y. Thus the relative positions of these two laws are reversed. The procedure is then repeated until the whole plot is evcept for the filling up wiith the soil that was moved at the beginning. a • which was moved first, i.e., the topsoil, is thrown in first so that the second layer eoil may be on top. . . It will be seen that true trenching is a much more laborious operation and it cannot be wondered st that bastard ti enching is the more popular method. True trenching, however, is the only torv means whereby fresh snrface soil mav be obtained. This, of course, with the provision that the fresh ' surface soil is good "topsoil," is a result which is desirable, and one to be aimed less to sav. it is nott necessary to cnange the topsoil annually, but, where practicable. a change every five or six years will do much good. Turning Under Green Manure. In the spring when the green manure crop is ready to be turned under. it will be found that bastard trenching]provides an excellent method for carrying out this work. The green crop may be cleared off the spits that are to be moved to the rear and it also may be placed in the rear. After the first lot 01 subsoil has been forked over, the green manure off the second lot of topsod mav be placed on the loosened subsoil and then covered with the topsouThis ensures that the manure is thoroughly buried. At the end the manure that was removed is placed in the trench ana covered with the transferred soil.- ine above procedure illustrates perfectly the method of true trenching, the gre«n crop representing the uppermost layer of sail, and the first layer of soil corresponding with the second layer of topsoil. How the two layers change places is Ehown very clearly. An alternative method of performing any baeWrd trenching is to divide the i (pist crosswise into convenient widths.

The soil from one division only is all that is necessary to remove. The subsoil may then be forked up and the topsoil from the next division thrown on to it. It is really the same process being employed, the difference being that instead of working straight from the top of the plot to the bottom, the operator works from one side to the other and back again in narrow strips. A second alternative method which may be used in place of that just described, consists of dividing the plot into two halves. The first topsoil from one half is thrown over to the other side, but not on the plot itself. Wheia one. half has been trenched the second hali is commenced from the end where? the other was finished. The first lot of topsoil from the second half iis used to fill in at the end of the first part and vice versa. When thfl method is followed it is unnecessary to transport the soil to the rear of the plot, which is a great saving. Provided that the pldt is not too wide (which is not very likely in a small garden), it will not be a difficult task to throw the soil to what will be the back of the second half of the plot. Ihe plot may be divided into three if it is rather large. In this-case, how- ®^ er > it will be necessary to transport the soil to the opposite corner of the Plot. _ Although when it is necessary to divide the plot into thirds the transporting of the soil is not obviated, yet there is only a third portion of the quantity that has to be removed if the direct method "" is followed, as was described first of all.