MOLE DRAINAGE DEMONSTRATED AT Y.F.C. FIELD DAY

Bay of Plenty Beacon, Volume 14, Issue 16, 25 July 1949, Page 4

MOLE DRAINAGE DEMONSTRATED AT Y.F.C. FIELD DAY

On Wednesday a successful demonstration of mole drainage was given on Messrs Sax Brothers’ property at a FieH Day arranged by, the Wainui Y.F.C. with the ance of Mr E. R. Marryatt, Instructor, Whakatane. There was an attendance of ovb-L 30 Y.F.C. members and interested farmers plus a contingent from the Whakatane District High School. Mr Marryatt first gave an interesting and highly instructive address on the nature of soils and the need for drainage. He explained how a soil, broadly speaking, consists of particles of mineral matter and organic matter. The size of soil particles varies with the soil type and also at different depths in any soil. The space between the soil » particles is called the “pore space” and it is here that surplus soil water is found. Surplus water moves by gravity through the pore spaces. Thus a 4 soil with large particles, sandy soil for example, lias 1 and is much freer "draining than a clay soil, which is very fine textured and compact. Excess water in the soil is undesirable from the farming point otv view because it restricts the growth. • of desirable plants' and encourages undesirable species. Excess water limits plant growth by restricting root development and by directly starving the plant. This is Caused by the water displacing air in the soil space and thus denying the plant essential oxygen and nitron gen.

The activities of soil micro-org-anisms are seriously curtailed by excess water and this is a contributing factor in the restriction of plant growth. In close-packed soils, such as clays, drainage by open ditches is not satisfactory simply because surplus water cannot move in the restricted pore space. It is in such cases that mole drainage is beneficiah

The speaker then went on to demonstrate the structure and action of a mole plough. The implement consists of a thick steel blade 6 to 8 inches widd. On th§. lower end is fitted a pointed “torpedo.” Behind this is metal cylinder called the plug. ' It is the size of the plug that determines the size of the mole channel. The blade is adjustable for depth and is attached to a frame which ' slides over the ground.. The passage of the blade through the soil leaves cracks through which the soil water can move and reach the mole channel and thus drain away. In this ‘ case the moles were pulled from an open ditch across a field with a fall of about 1 in 80. Ideally, moles should be pulled nearly at riht angles to the fall of the ground. This is to enable the water to get into the. whole channel more easily. Also too great a fall in mole will lead to scouring, especially at the outlets.

The mole plough used had a 2J” plug. These moles were pulled approximately 2ft deep and 6 feet apart. -“Fordson tractors were used to pull the mole plough, and Messrs and Co. of Whakatane, . demonstrated a tractor half track equipment. Mr Marryatt pointed out .that it was necessary to have the ground surface fairly even. The mole chan- ' nel, of necessity, followed the contour of the ground and. water would* tend to collect in any dips, leading to collapse and blockage of the mole in short time.

Mole draining can also be done in peat soils, provided there is not much timber in the peat. In such soils it is the slit left by the blade rather than the mole channel which provides an outlet for the surplus water.

The demonstration concluded with afternoon tea provided by members of the Wainui Y.F.C.