MOLE DRAINAGE ON A MANAWATU FARM

Evening Post, Volume CXXIV, Issue 108, 3 November 1937, Page 21

MOLE DRAINAGE ON A

MANAWATU FARM

(CONTINUED FROM PAGE 20.)

overthe ridge at ythe plough is tripped and leaves the ground near outlet B. The tractor turns, the plough is set up again near outlet B, and a parallel mole drain is drawn six to nine or up to eleven feet from the. first drain. The plough is next tripped , at: outlet A, and the process repeated until 4 to 6 mole-drains are drawn The plough is next set lip in the outlet drain A, figure 2, and without altering the depth, is drawn so as to cut across the blind ends of the drains.already dravn. This drain is .continued ori.es an ordinary mole drain to outlet 78. The plough is then set up in outlet B and agdin the plough is drawn so as to cut across the previously made mole drains. The process is illustrated in Figure 3. The method of cutting across the ends of groups ;or'fans:of completed drains with gathering drains opening into the outlets is continued across the field. New outlets are .made use of as the work proceeds. Where it is not possible to work to two outlets the mole is drawn to the highest point-requir-ed ."away, from the outlet, the tractor turned, and a parallel drain drawn back to the outlet. The same method of cutting across the ends of groups of these drains with a mole drain discharging direct into- the outlet is adopted. It will be noted that the mole plough is in the ground the whole of the time with the exception of the short turns, and that no time is wasted running back to the outlets.

Each of the intermediate drains'terminates in a bliiidend and'while the tractor work is gping on the work of connecting these intermediates up with the outlet mole. drains leading to the outlet ditches is proceeded with. The crossing of 7 these intermediates' with a mole drain 'intended as an outlet results in the complete blocking of .the first drawn drains whether, the outlet drawn is drawn at the same level as in this case or Within two or three inches Neither above or below. .For, the purpose of providing for the free passage of waterandwhat is more important for. the .clearance of silt in later years >fi-om the iniiprmediates ■ to* the outlet drain, a cleaiy'full-sized; corinec-; tion must be made between them. This is easily and rapidly acccmplished with the aid of : a simple tool, made in the form of a corkscrew with a universal joint-in the handle.

The points-where the outlet drain cuts each intermediate .are marked— a hole is dug in the blind ehd of the intermediate ' down, to the mole drain so as to cut it at a short distance from its junction with the outlet drain. The corkscrew/ augur with .--.a universal joint.isy;used to clear the. clay plugs blocking this.drain. 'With .the removal of, these: plugs, if .there is sufficient water, in .the mole drain, it will run into.- the hole' which Was dug but can be diverted to the outlet drain by plugging up with good clay the open end of the,mole drain which has just been,cleared..'The hole is then filled in, and the, Connection is completed. THE PERMANENT OUTLETS. " The "final 'process is,;the laying of tiles, ■. preferably -' foiir-inch unglazed drain tiles,' in ; each of the outlet ditches''to give; a" permanent outlet not likely to: be 'trampled' in and blocked by cattle or .'sheep.' The bottom of the outlet trench1 into which the outlet mole drains have' been drawn -is built vpv so- that HKe tiles when1 laid will be close qp:to;thfese'openih'gs. Hojes are mafleiin the.sidesof thetiles opposite the } mole -'d^ain' outlets and pieces of tile.or special,short lengths,of 2jin tile are used to make a.' direct connection between the niplesand the tile draini

Sticky clay' is then used to pack over the connections and along the length of four-inch'tiles to ensure a. permanent job. The outlet is then filled in. The implement used for cutting tiles to suitable lengths and for cutting holes in the sides of the tiles is made from an ordinary worn mower knife section.fitted to Vshort handle, and a hammer is used to p«nch out the hole when the outline'is sufficiently Chipped with the other •implement. !

A length of 3-inch'hose fitted with a corkscrew at one end and a plug of hard wood at the other is: useful for clearing obstructions in the outlet drains when as sometimes occurs the plugs are not' properly cleared from the intermediates. •It is also useful later in clearing obstructions such as silt accumulations near the outlets and in maintaining the drains in good order. Ay •. : The effectiveness of mole drainage is clearly1 shown by examining drained and undrained paddocks. In the surface of a paddock as yet undrained, the pasture is weak, and open, and the soil wet and sloppy, ideal conditions for sheep, parasites and bad foot rot,,and always, liable .to, rush invasion. In an adjoining field, mole-drained for four years-and-sown-inthesame good rye

and white clover, the rye and clover are .flourishing, with little chance of reversion to browntop or rushes. The surface is dry and firm, and able to carry heavy cattle during the winter. PERMANENCE AND RENEWAL. Most of the usual methods of mole drainage on such country had been tried out during some twelve years by Mr. McLeod, including the connection of deeper outlet drain's with intermediates by means of a spear Or the use of totara slabs placed over the junction when this had been cleared. His experience has been that generally the efficiency of the drainage has , improved up to about three yeaijs, then I there^ has been, a rapid falling off in the effectiveness., Wet patches appear and spread throughout the field until the system has to be renewed in about five years. Although the first area drained by the new method has been done for five years only, the fact that there has been a steady improvement in the effectiveness of the drains during this period and that the discharge of water at the outlets after rains is still as good as ever indicates that-a much more permanent" and satisfactory job has been done. Renewal of the drainage system if and when required is not difficulty in that to commehce operations all that is required is to dig out

the short length,of' tiles 'from -each I outlet. ■'••"■'• ','•■,'■' COST OF THE WORK;. Detailed costs for the- ■-complete mole drainage of the !32-aci-e area described in this article are 7as follows:—Fuel, A3? gallons -at Is Id, £2' 5s 6d; oil, 29''hours at 3d- per .hour, '7s 3d;' wages, three men 29 hours at 2s per hour, £8 14s; depreciation; tractor and plant, at Is 6d per hour, £2 3s 6d; tiles for outlets, 18s; wages, 2 men 8 hours at"2s per hour, tiling otitletsj ;'£ 1 12s;! total, £16 Os 3d.' Cost 'per, acre, 10s. ''.* * ■' ■*/ ■■ : ' ■■■■■>;■ ■ ■■■ \

SCOPE OF MOLE DRAINAGE. Tlieessehtial conditlphs!Jorj satisfactory niole drainage'are:-— ,'

I.' s.A7 suitable; stiff iClay', subsoil-,free £rortv^pbslractions;;sji^j'y-Bis|p:irqhst<^e. pans, rpots, or;large'; stones .. which would; interfere (with ithe s'drawing ;of

the rtiole drain plough through the soil; ■; y-; \- ■ .' ".■'■" '■". '' 7

2. The stiff: impervious subsbil must be within 20 to 22 inches of the surface, as -this -is the maximum /depth that the usual.plough will go.

3. There must be' an appreciable fall in "the direction.of the mole', if the drains'are tp last. On flat land or land with little fall mole drains do not last long, but .'are' afteri well worth putting in because of their effectiveness while they do last. •'.'"•

. There are many thousands of acres of country in the Manawatu, Rangitikei, and Southern Hawke's Bay districts with conditions almost ideal for effective and lasting mole drainage. The ■ illustration of a portion of Mr. McLeod's farm is typical of such country. The free drainage of. several inches of dark loam soil is held up by a stiff impervious clay subsoil, the fall is generally good, and suitable places for' outlets are easily found. The lower plough-able-slopes of much, of .the steeper, hi 11,,, c.ounlry in many districts "lie wet'and, cold in the winter because of, the stiff subsoils and the mole plough caivbe used with good results on such land.- In many, other districts; particularly;.'in : North Auckland and Southland.the. stiff, clay soils I can- often be- drained -and (improved- by

mole drainage and the method described adopted with advantage.

The mole plough is not effective on relative loose and open soils where the drainage may be bad bri account of a pan formation. Mole drainage, though effective, cannot be made lasting on i-elatively flat land such as river flats and swamp land, even where the subsoil may be ideal for the purpose. The fall is not enough to keep the drains cleared of silt and they rapidly tend to silt up although the outlets may be kept clear.

If mole drains will last, however, for three to four years as they often do in land with a slight fall, and can be I put in for a few shillings per acre, | the effective removal of surface water is well worth while, The renewal of the drains is easily done when a tractor and mole plough working to suitable open drains can do up to 15 to 20 acres per day. ....... -..-'■ GENERAL NOTES ON MOLE DRAINAGE. Opinions vary as to the best cepth Ito draw the moles, and the best time to do the work, but the following general recommendations are considered sound under average conditions. ■-.-,., -. < ,-,.-.: Depth of Drains.—A minimum depth of 12in with the plug working .at least two inches in the clay subsoil is advisable. With mole drains nearer the surface the sides of the. drain are likely to crumble rapidly in dry weather. There is also the danger of damage to the drains at soft spots by heavy cattle or by the plough. Mole drains drawn deep in the clay, particularly in stiff impervious clays, are. generally ineffective, the water taking' too , long to pass into the drains.1 Deep drains, however, last well. In practice, a depth of 14 to 18 inches with the mole drains about 3in in the subfjoil: is fouhd ,to give good results in rapidity of,drainage and in lasting drainage. Time to Drain.—The best time to do the work is when the subsoil is wet and the surface dry. The dry surface means less cutting about and more effective pulling power of the tractor. The wet subsoil ensures less draught and good clean mole drains. Suitable conditions seldom'occur both in respect of the dry surface soil" and wet subsoil, until the land is dtying out in the spring. September and;. October are often good months in'which to'do the work. Mole drains drawn under very wet surface conditions are liable' to blockage by soil going, down, the knife cuts. The.results, however, are quick and spectacular, and "there is a. tendency therefore to do ythe' work under these conditions,. which are riot at all' fayburable for lasting-work. [ '/■'

Other Points.—There are a.number of other points regarding mole draiinage,

the size of plug, speed of the plough, pulling across the. steepest slope, not crossing depressions, correct spacing, and many others which should be considered. A 2i.in to 3in plug is generally used, and this size of plug is suitable to most conditions. The stiffer and stickier the'soil, the smaller the plug, and vice versa.

The best speed for the plough is about 2i to 3 miles per hour.- Fast work is not desirable as the drain sides tend to be, drawn .in and in somewhat dry: soils .will flake. - ' '

Although it is held that the.mole drain lasts, better ; ; if. drawn,away, from the outlet and up the slope, this is not essential to good work.' Pernjanertt outlets and the provision of sufficient pressure in the'stream, of .water doyen the moles'is considered of far greater importance, and also ,the saving 'of time when-the plough is, kept in the ground continually/

Depressions 7 should.- not toe crossed, as silt is liable to collect in the depressions in the'drains and/cause blockage. The' mo.dern;type;of'.light' mole plough can be used to cross the narrow finishes and fearirigs, as. the general depth of the mole drain is not affected in crossing these. An effective spacing in' most soils is about nine feet, but onverywet,-stiff /soils the moles should be as closed as six, feet! Mole drains should be close together when running down the grade and wider apart across the fall or steeper slopes.

The method Of mole drainage described in this article is confidently recommended to those practising mole drainage under similar conditions, and farmers'are further recommended to consider the possibilities of the mole plough' where good drainage is; required. . . ■; ' -.■■','. >