MECHANICAL CLEARING AND GROUND PREPARATION FOR SOFTWOOD PLANTATIONS IN THE AUSTRALIAN CAPITAL TERRITORY

SUMMARY

The technique of clearing and ripping adopted in the A.C.T. is considered very satisfactory for plantation establishment in areas with a rainfall of less than 25 in. and where slopes are not greater than 15 degrees. This technique is now accepted as standard practice for such conditions in the A.C.T., and considerably improved results of establishment are becoming evident.

The main advantages under these conditions include a better initial “take” of the planted pines and the almost certain elimination of the need for refilling; better growth and vigour during the first few years, owing to cultivation and the efficient absorption of rainfall; reduction of run-off and evaporation, owing to the roughened surface of the ground; minimum growth of suckers of indigenous eucalypts following uprooting of the stumps; easier access for subsequent tending and utilization of the crop; and provision of a cleaner forest floor, which greatly simplifies fire protection. Costs of mechanized clearing and ripping are considered to be justified in comparison with costs of manual clearing and soil preparation.

In areas with a rainfall of less than 25 in. and where open grassland is converted to plantation, it is essential to prepare the soil by cultivation in order to reduce competition from grasses and to conserve all normal soil moisture. Under such conditions it is considered that cultivation by ripping, which breaks up the subsoil without turning it up to the surface, is much more satisfactory than normal ploughing, which may provide better cultivation to the top soil but which does not penetrate to a sufficient depth to achieve effective water conservation.

In areas where rainfall is more than 25 in. per year, and timber growth is consequently heavier, it is doubtful whether the higher costs of heaping and burning are compensated by the advantage of ripping. In such conditions it is the practice in the A.C.T. to burn in situ and to prepare the soil by digging holes with a mattock or spade.

Costs of mechanically pulling down indigenous forest and burning in situ are considerably lower than those of falling by axe work at present-day rates of pay and standards of work.