THE IMPORTANCE OF WEED-CONTROL AND THE USE OF TREE SHELTERS FOR ESTABLISHING BROADLEAVED TREES ON GRASS-DOMINATED SITES IN ENGLAND

The results of seven experiments are used to illustrate the mechanisms of weed competition and its effects. Studies of soil moisture tension and foliar nutrient content indicated that competition was primarily for moisture and nutrients reducing the survival and growth of young trees. These effects are greater on soils with poor moisture retention, or where the climate results in high soil moisture deficits. To be effective, weed control must eliminate root competition. This can be done by cultivation, herbicides or mulching; cutting weeds above ground level is ineffective. Tree shelters accelerate the height growth of young trees and protect them from mammals and herbicide drift.