INFLUENCES OF ROOT PRUNING ON SHOOT GROWTH AND YIELD OF THE SUMMER CROPS IN MATURE TEA PLANTS

In 1990, different root pruning treatments in conjunction with shoot p runing and the application of nitrogen and organic materials were carr ied out on 18-year-old tea plants (Camellia sinensis (L.) O. Kuntze). The pruning treatments consisted of 1) light pruning every late August and application of organic materials (conventional), 2) heavy root pr uning and application of heavy nitrogen and organic materials only in late September of 1990 (late September I), 3) heavy root pruning plus shoot pruning only in late August of 1990 (late August II), 4) heavy r oot pruning plus shoot pruning and application of heavy nitrogen and o rganic materials only in late September of 1990 (late September II), a nd 5) no pruning (control). The influences of the root pruning treatme nts on shoot growth and yield in the following summer tea season (seco nd and third crops) were studied from 1991 to 1994. For the control pl ot, shoot numbers per unit plucking surface area and 100-new-shoot wei ghts in the second and third crop seasons showed no remarkable annual changes, and yields in both crop seasons were almost steady over four years. For the late August I treatment, yields in both crop seasons we re steady and maintained the same level as the control over four years . For the late: September I treatment, the yield of the second crop tu rned increased after the second year through an increase in shoot numb er without a decrease in shoot weight, although there was a reduction of about 10% in the first year. The late August II and late September II treatments failed to give better yields for the second and third cr ops as compared to the control throughout the four years. The influenc es of root pruning on shoot growth and yield of summer crop seemed to diminish after the first crop. Some treatments, however, affected yiel ds in the second crop season and even in the third crop season. The re sults prove that root pruning is effective to improve productivity of summer crop season and that treatment under favorable conditions is in dispensable.