Agricultural and Pastoral.

Otago Witness, Issue 987, 29 October 1870, Page 10

Agricultural and Pastoral.

DRAINAGE OF LAND.

A correspondent of the Qacenslander writes on this subject as follows :—: —

There are at least three ways of arranging drains. There ia — first, longitudinal draining ; draining with the fall o£ the land, or straight up and down the rise. Secondly, we have cross draining, or the plan of going directly across the fall ; and thirdly, there is diagonal draining, or gointj from corner to corner partly with the fall and partly across it.

It may tie very true that all these three ways of uraining will do, but that is not the question. It is not what will do, but %\hat will do best. It is what will cost least, last longest, and what will prove most satisfactory. I shall strive to point out the advantages which longitudinal possesses over cross draining ; and I can dismiss the third, or the diagonal plan, by pointing out that all the objections to cross draining apply, although not with equal force, to it. Diagonal draining has, further, the great drawback which is ail its own, that the main drains, which are the most expensive, must necessarily extend round two sides of the field, or at least be much longer than is otherwise desira le. There is one thing that must be borne in mind in dealing with this subject. The principal object of subsoil draining is not to take the water off the land — this only happens as a matter of course. The real design of draining is to make the soil porous, and uniformly so to the required depth. If we consider the matter, we will find that there is a great difference between those two results. There is abundance of land which is dry enough, and on which no water lodges, which has still so tenacious a subsoil that the rain will not penetrate it freely but runs off it. Now, the good that draining does to such land as this, is so to split up the clay of the subsoil, that the rain may percolate freely and also equally through it in all directions.

I will now sta'rf the objections to cross draining, asking you to bear in mind that they also a;. ply to diagonal draining. Ist. While water is running in a cross drain, the land on the lower side of it is not beneficially influenced by the drain ; on the contrary, the lower side rather receives water from it than has any taken off. ....

2nd. That as the upper side_ of the drain has to do double work, this is one of the reasons why the drains must be placed much closer than is required by the longitudinal system. 3rd. It is a well-known fact that the strata -which compose the subsoil, crop out at the surface in many instances, rather than lie parallel to it, therefore cross draining is very likely to miss the points where the strata are wet, whereas longitudinal drains are as sure to cut the ends of these strata, and thereby withdraw any water they may contain. 4th. In cross draining the water falls more unequally at different points in the drain than on the longitudinal plan, and the co; s. quence is that there is a great tendency in the tiles or other materials to sink or give way at spot 3 which receive an unusual gush of water, thus rendering the drain more or less uselebS. sth. My last reason is, that in the longitudinal dr.dn the water has the least possible distance to travel, and as it has all the available fall, it runs off far quicker than it can on any other plan. The water is thus allowed to follow the course that the attraction of gravity dictates, and a proportionate economy in tiles or draining materials is the result. I think 1 bave thus shown that at least the preponderance of evidence is in favour of withdrawing the superfluous water by the shortest cut, which is also the least expensive.