Cultivation and drainage are usually the first operations carried out to prepare a site for planting. Their effect is to create a favourable planting site for new transplants by loosening compacted soil, removing surface water and creating a raised planting position to lessen the effect of competing vegetation. In past years, several cultivation practices where used such as ploughing with large single or double mouldboard ploughs, mole and tunnel ploughs and rippers depending on the soil conditions. Today, however, mounding using excavators is the most common practice on most sites. Small mounds are excavated and placed at 2 metre intervals. The drains that are formed by removing the mounds are spaced at 12 metre intervals. Planting takes place on the top of the mounds.
Mounding has been shown to produce more symmetrical and therefore more stable root systems than of most of the other cultivation methods; it also can be carried out using excavators which are widely available.
Cultivation and drainage can result in soil disturbance so care has to be taken to ensure that sediment is not carried into water courses, particularly if ground preparation is followed by prolonged and heavy rainfall. The Forest Service has produced the Forestry and Water Guidelines which require that soil disturbance is avoided close to all aquatic zones. The Guidelines also require that buffer zones be established along all water courses that feature on the OS 6” maps. These buffer zones vary in width depending on the slope of the site and are usually open space or are sparsely planted with native trees and shrubs to encourage bank side vegetation. This will slow down run-off from the site and catch sediments and nutrients to prevent them entering the water courses. Correct drain alignment, spacing and depth and the construction of sediment traps along drains help to ensure that erosion and sediment build-up are controlled.
Planning the cultivation and drainage of a site requires skill and experience and is an important aspect of the establishment process. Its effects can last for many years after the new plantation is established influencing not only stream water quality on the site but also the subsequent growth and wind stability of the forest crop.
The following Forest Service guidelines are relevant :