MANUAL RECORDING OF MINIRHIZOTRON DATA AND ITS APPLICATION TO STUDY THE EFFECT OF HERBICIDE AND NITROGEN-FERTILIZER ON TREE AND PASTURE ROOT-GROWTH IN A SILVOPASTORAL SYSTEM

The use of a simple counting method using a borescope and minirhizotro n system to study the interaction of roots of wild cherry trees (Prunu s avium L) and pasture in an upland silvopastoral system is described. Operator variation was greatest when distinguishing different tree ro ot categories (e.g. white, brown, woody) but was not significant in re lation to total tree or grass root counts or species differences. Anal ysis of covariance was used to take these differences into account in a field trial using several operators. The seasonal patterns of tree a nd pasture root growth were different. Tree roots peaked in May before maximal shoot growth. The peak in pasture roots occurred two weeks ea rlier. Tree height growth was increased by the use of herbicides to co ntrol grass growth but this effect was only apparent during August whe n the soil was dry and when pasture root counts were reduced.