Control of natural regeneration of radiata pine during second rotation establishment using slash retention techniques.  P. W. Geary, S. J. Pollett, D. S. Thomson and D. W. Flinn.  April 1987.  29pp. (unpubl.)

SUMMARY

It is now standard practice in the Rennick Plantation in south-west Victoria to retain the logging slash from the harvesting of first rotation stands of radiata pine in situ, in order to conserve nutrients, organic matter and soil moisture for the second rotation (2R) crop. However, the chopper-roller that has been used to macerate the slash into a suitable mulch has not been able to eradicate the dense populations of natural radiata pine regeneration that develop in multi-thinned stands and survive the clearfelling operation. They consequently pose a major problem in 2R establishment using slash retention techniques.

A number of alternative methods for controlling these wildlings and macerating the logging slash were evaluated in the Rennick Plantation during 1982-4. Treatments included the single or sequential use, pre- or post-clearfelling, of chopper-rollers, a rotary slasher, a delimbing flail, low intensity prescribed fire, motorized brushcutters and the herbicide amitrole.

Slashing the wildlings prior to clearfelling with the National Hydro-ax rotary slasher, followed by a low intensity prescribed fire, was found to be the most effective and operationally feasible treatment tested. This treatment destroyed 95% of the wildling population, at a cost of $110 ha^-1, and is now a routine part of the 2R establishment sequence used in the Rennick Plantation. However, some follow-up hand-cleaning is still required 12-18 months after 2R planting, to eliminate those wildlings either surviving or germinating subsequent to the treatment.

In 1984, the total cost of the 2R establishment sequence, including the control of natural regeneration, was about $520 ha^-1. This is higher than costs previously reported for 2R establishment using slash retention techniques, but still provides significant savings when compared with the alternative of high intensity slash burning, especially when replacement fertilizer costs and the benefits of mulching are considered.