INFLUENCES OF ROOT PRUNING ON REPRODUCTION AND ACTIVITY OF ROOTS IN MATURE TEA PLANTS

Regeneration and activity of roots after root pruning have been studie d using mature (18-year old) tea plants grown in a field. The amount o f the newly-developed white roots in a 20 cm deep-soil layer was great est in the late September I plot (combination of hard root pruning and nitrogen application in late September every several years) followed by the late August I plot (light root pruning at every late August:the most conventional management) and late Autust II and late September I I plots (combination of hard root and shoot pruning in late August or late September every several years). Root activity determined by an ac tivable tracer method accurately reflected the degree of root reproduc tion. Root pruning and root-shoot pruning remarkably restrained subseq uent shoot growth. These growth reactions of shoot and root to root pr uning obtained through the present experiment resembled those in young tea plants. It was confirmed that root pruning is applicable as one o f the techiniques for regenerating tea plants irrespective of age beca use root pruning promoted active reproduction of roots in mature plant s. It was judged that the activable tracer method in tea plants is eff ective to grasp the root activity in soil layers at a practical level.