Turnips After Grass.

Star (Christchurch), Issue 5212, 20 March 1895, Page 4

Turnips After Grass.

EARLY VERSUS LATE PREPARATION OF LAND. J [BY MB 3. BATNB, DIRBCTOB OP WNCOLN j COLLEGE.] ! An interesting experiment has been made on the Lincoln College farm to demonstrate to the students the difference between early and late cultivation for the turnip crop-after lea. The field for experiment is about six acres in extent, and had lain in pasture for four years. The Boil may be described i as a clay loam, of even texture andquality, i free from stagnant water and in good heart. Indeed, so far as quality of land goes, no better selection could have been made with a view of obtaining reliable results. It was divided into eight plote, the even ones— 2, 4, 6 and B— being cultivated early; and the odd ones — 1, 3, 5 and 7— being cultivated late. The amount of labour bestowed on each plot was the same, and so, too, was the Coßt of the manures. The early cultivation began on Sept. 29, and the late cultivation on Nov. 15, thus making a difference of seven weeks between the two. The turnip seed waß drilled on Dec. 20, on the flat, and to all outward appearances the tilth and condition of the whole field before sowing was the same, and such as to warrant a uniform and good crop. But far different has it proved; the turnips on the early cultivated plots are of iuxariant growth and completely cover the ground, while those on the late cultivated plot3 are stunted in growth, are very patchy, and look as if they had only been sown about three weeks. The weight of crop we refrain from estimating at present, as the actual weights per acre will be taken and these made known after the turnipa have come to maturity. Suffice it to eay, however, that, judging from appearances, the crop on the early cultivated plots will be .a success, while that on the later cultivated ones will prove a failure. And whence comes this difference P Not from the cultivations, nor from the manures, nor from the time of drilling, as these were all the same; nor from any imperfection on the part of the drill, aa it worked efficiently, but from the length of time the land lay exposed to atmospheric influences. Clay soils cannot be forced into a tilth by late cultivation without the moßt Berious consequences. If dry weather follows, they become hard and baked owing to excessive evaporation. They lose their moisture to the depth to which they have been ploughed or stirred, and it takes a considerable time before the moisture of the subsoil permeates tho cultivated or overlying soil, owing to the slowness with which the water rißes by capillarity. If wet weather follows they become muddy and pasty, owing to the fact that the particles oi a clay soil that have not been exposed to the atmosphere run more freely together than do the particles of the soil that have been exposed some time. In neither case can small seeds be expected to germinate readily and evenly, or to produce plants of a vigorous growth and development. j Of all claßses of soils, clays should be ploughed early, so that they may become mellow and pulverised by having the fullest advantages of all the natural atmospheric agents which assist the farmer in securing the very object he wishes to obtain, namely, a moist, deep and fine seed bed, abundantly supplied with plant food. In short, a farmer who ploughs and does subsequent tillage operations on clay land, trying to accomplish in a short time what experience and science say should take, much longer, doe? so against his own interests, in not working in harmony with che natural atmospheric agents which are, so to speak, at his disposal. '■ And what are the natural atmospheric agents ? Frost, rain, heat, wind, &o. In New Zealand extremes of temperature are not very marked ; we have not, as in the Old Country, the hard frosts followed by rapid thaws which, might in a fortnight do more towards pulverising the soil than can possibly be accomplished in a much longer time in this country. Yet, though we have not extremes, we have many and sudden changes of temperature; for example— Blight frosts followed by strong aunshino, rain followed by drought, strong winds, &c, all of- which play their part in bringing about a pulverisation of the soil. And while this pulverisation is being brought about^ so also is the chemical condition of the ingredients in the soil being changed. The very large percentage of insoluble ingredients is being converted slowly into a soluble condition, and thus becoming fitted for assimilation by the crop ; and should there be — which is by no means of infrequent occurrence in clay soils-— any ingredients harmful to plant growth, a large proportion oi these, through the soil being exposed to the air, becomes changed into harmless and useful ingredients. Lastly, in the atmosphere there are compounds containing nitrogen, useful for plant growth, which are brought down by rains, mists, dews, &c, and are absorbed and partially retained by the soil, more especially when it is in a finely pulverised condition; Hence by cultivating early we not only work with Nature, but secure her help in obtaining— and that in not too short a time — a finely pulverised soil, free from ingredients harmful to plant growth and well stocked with soluble plant food. One of theße plant foods we may mention, inasmuch as the field had lain in grass for four years, is nitrogen; Nitrogen is, as we know, an element in every plant, and, therefore, must be obtained in some way by the plant. During the time the field lay in grass, a large quantity of nitrogen was being stored up in the roots, stemß, and leaves of the grass, and should have been of the greatest use to tbe young - seedling turnips had it been in a condition capable of being taken in by them. But not so ; the nitrogen being an element in, and forming part of, the organic matter, nothaving time to decompose in the soil, was in* reality of no use to the turnip. In the case of the early cultivation, however, the orgunic matter decomposed, and the nitrogen assumed a new relationship in the soil. It was no longer an element in the organised structure of roots and stems, but became an element in a soluble salt (nitrate), on which tho plant could freely feed. 'Hence, instead of getting as much of that all-important elemont as possible, practically none of it was obtained by the turnips in the late cultivated plots, as the time allowed for decomposition of organic matter was not sufficient. To sum up, we believe that 9 the reasons why the turnips on the late cultivated strips are practically a failure are : — Firstly, and of the greatest importance, want of moisture in the soil at the early stages of turnip growth cauged by excessive evaporation, as the clay land was broken up towards spring and the soil left so dry as to prevent some of the turnip seed from germinating, and the seeds that did germinate from producing vigorous plants. Secondly, want of suitable plant food containing nitrogen; that want being occasioned by the non-decomposition of organic matter in the soil. Thirdly, the want of a naturally fine, deep and mellow tilth, containing mineral plant food — other than nitrogenous — in a soluble condition ; the ground being too . short a time exposed to atmospheric influences. [The paper was illustrated by a photograph of two of the plots, Nos. 5 and 6, which brings out very strikingly the great difference in the crops— the turnips on the early-cultivated land being very thick and luxuriant in growth, while those on the late - cultivated plot are seen only in patches and are stunted in growth. — Ed.]