Evaluation of mechanical methods for treating Pinus radiata logging residue.  C. J. Leitch and P. W. Farrell.  August 1980.  14 pp. (unpubl.)

SUMMARY

Three methods were evaluated for mechanically treating Pinus radiata D. Don logging residue, as alternatives to the conventional practice of windrowing and burning. Two of the treatments, the Williames Chopper Plough operated at high rotor speeds and a Roller Chopper, chopped the residue without disturbing the soil; the third, the Williames Chopper Plough operated at low rotor speeds, ploughed the residue into the soil. The trials were carried out in the Rennick State Forest in south-western Victoria where second-rotation growth studies on the infertile soils of this locality have shown that tree growth is enhanced by retaining logging residue in the form of a mulch. This was attributed to the retention of nutrients and organic matter which otherwise would be lost during burning, to moisture conservation beneath the mulch and to the suppression of weed competition by the mulch.

The trials showed that it is both physically and economically feasible to treat and retain logging residue on the site rather than to heap and burn it. Of the two mulching treatments, the Chopper Plough produced a superior mulch to that of the Roller Chopper in heavy slash; the mulch being more uniform, less dense and comprised of smaller chips. Both treatments left a significant number of large pieces of residue which would increase the difficulty and therefore, the cost of replanting and other plantation management operations. In lighter slash, where pulpwood is also harvested, it is likely that the Chopper Plough and the Roller Chopper would produce mulches of similar quality containing few large residue pieces; in such a situation, the only advantage of using the Chopper Plough would be that it would macerate hardwood logs and stumps which had survived the original clearing. The heavy slash sites which had been ploughed by the Chopper Plough were comprised of loosely packed soils with large residue pieces spread throughout, making it more difficult and therefore, more costly to establish a new crop.

The estimated comparative total costs (1980 $) of site preparation by windrow burning, maceration (with minimum soil disturbance), ploughing (residue incorporated into soil), and roller-chopping are $970, $620, $1105 and $550 per hectare respectively, including the cost of nutrient replacement by fertiliser application. Without nutrient replacement, comparative costs are $200, $250, $545, and $180 per hectare respectively. Roller-chopping is therefore the most economic treatment, whether or not nutrient replacement costs are considered.

Also published:

Leitch, C.J. and Farrell, P.W. (1980)  Evaluation of mechanical methods for treating Pinus radiata logging residue.  Agric. Eng. Conf., Geelong, Sept.-Oct. 1980, pp. 21-26.