The Drainage of Grass Land.

Feilding Star, Volume XVI, Issue 57, 1 September 1894, Page 2

The Drainage of Grass Land.

Adapted from " Permanent arid Temporary Pastures" by T. Watson^ No. 2. ' '" : It is a mistake to suppc)Be that the rainfall goes direct to the drains and is at once expelled from the land.; On the contrary, the ram sinks into the land until it meets and mixes with the subsoil water, and the .drains- do not begin to run until the water rises above their level; and while water, however small the quantity, is flowing in a drain-pipe, and probably long after it has ceased to flow, it may be taken for granted, that i the subsoil is saturated with moisture up to the level of the drains. The rise and fall of the subsoil water is, therefore, determined by the level of the drain, rather than by the surface of the soil, as it would appear in an undrained state. Thus, in well-drained land, the atmosphere is being continually carried into the soil by rain, and forced into it by atmospheric pressure as toe subsoil water falls to a lower level, and:the air is expelled when the water rises. , A water-logged surface is not' only jurious to plant life because there is too much moisture in it and top little warmth, but because neither r*in nor atmospheric air can enter from abqve, nor mineral constituents be drawn from below. Drainage sets all these natural forces in motion, and they open the soil and disintegrate its particles for the benefit of the plant life upon it. Again, drainage is always benefici^ >in promoting the early, apd late growth of grass, and this is of enormous vadne in feeding stock. The early autumn and late Bpring frosts do not arrest growth on drained land so quickly aa on : that which is sodden with moisture. Thus one of the effects of drainage -is to produce an ever growing crop. .It has been urged with perfect truth that from arable Land manures are often .washed into drains, especially in wet seasons, and that in draining, a farmer may be providing an outlet for manure which he has placed on the surf ace at great expense. Experiments have - proved that, with one exception, ior which the remedy is easily applied, the loss of fertilisers by means of tiie drains is practically nil when a green crop is on the ground.. On the contrary, water flowing from drains under a bare fallow alongside, was at the same time, highly charged with raannrial matter. Hence the grass farmer is protected from this particular loss, as the arable 'farmer cannot always be. The exception alluded to is the possible -loss of lime. This essential constituent of plant life is one of the substances most easily lost by the drains, and it accounts for the necessity of applying this mineral from time to time on drained land which happens to be deficient in it. Bnt while anunonia —which becomes oxidised into, nitrio acid, and, entering into combination with lime, forms nitrate of Ume-~__*y possibly be wasted, it is satisfactory to remember that superphosphate of lime and other forms of phosphoric' acid are never lost. Nor . does : it appear that potash is easily abstracted, so that there need be no hesitation in applping Uiese substances from fear that they will be carried away by the drains. It may lie accepted as a general truth that grass land should not be drained so deeply, as arable land. There is no doubt that grass can advantageously take /mora water than grain crops. Further, Ijhe roots of most grasses do not penetrate very deep, and therefore it is desirable to have the water soirie what nearer the surface that on land set apart for arable purposes. The manner in which drainage should be carried out in any particnlar case depends on soil, chma^, emd other considerations. These coriditidris must of course be taken into account, but they concern the details and not the principle of the work. All soils which rest upon a porous subsoil do' not need, draining. Other land may he retentive," and yet lie so high, or at such a st^ep inclination, that the water is discharged with sufficient rapidity without artificial aid With these exceptions all clay lands, whether the clay is only in the subsoil or rises to the surface, and all peat lands whether the peat has clay beneath it or not, and in fact all land that is habitually saturated with water, must be effectually drained before a pasture worth, having can be established. The prejudice which occasionally exists against the adoption of a system of drainage can generally be traced to bad workmanship or neglect to maintain the drains in proper order. It is a safe general rule not to make any single drain too Jong, and plenty of fall should be given, or the pipea may" no;f work well after tbey have been laid some time. A good fall renders them to a considerable extend self-cleansing, and the small drains should not enter the large ones at right angles, bnt always obliquely, bo that the water may retain tbe momentum received in its previous career. No definite rule can be laid down as to the depth the pipes should be inserted or tbe distance between the rows. In heavy land they must be. near together, and not too deep; but in lighter land the lines may be comparatively far apart. About three feet deep with the : rowa fifteen feet apart may be giv<s fo % general prpportlob, but' diversity of ampface conformation and subsoil will frequently require a deviation from these figures. The after keeping of the drains in proper working order, it is soersely necessary to remark, is of the greatest importance, for neglect may render them worse than useless. " . ,