INVESTIGATIONS INTO THE WEED INFESTATION, WEED SEEDBANK AND TEA GROWTH IN RELATION TO THE DIFFERENT WEED MANAGEMENT METHODS IN YOUNG TEA (CAMELLIA SINENSIS L. KUNTZE) PLANTATION

摘要

A field experiment was conducted in the Low-Country of Sri Lanka, during the period 1994 to 1995 to investigate weed seedbank density in soil and severity of weed infestation and growth of tea in relaion to weed management methods during early tea establishment. Manual weeding at various intervals was compared with the use of various herbicides, with and without mulching. Weed seedbanks were determined using "seed germination method" and "Malone's seed extraction method" before and 12 months after imposition of treatments. Seedbanks were reduced marginally (6%) (p>0.05) with the use of herbicides, but increased (40%) when manual weeding was less frequent than six week intervals. Glufosinate ammonium at 0.2 kg a.i. ha" and 2, 4-D at 0.94 kg a.i. ha~(-1) followed by at 0.17 paraquat kg a.i. ha~(-1) were less effective in weed control and had little influence on reducing seedbank density. Weed control with herbicides was superior to that of manual weeding (P<0.05). Manual weeding at six-week intervals and herbicide treatments affected tea growth similarly, but the former was not cost effective. Neither agronomic nor economic advantage was achieved with manual weeding at two-week intervals. Plots allowed to remain weedy for 12 weeks or more adversely affected tea growth. Application of oxyfluorfen at 0.29 kg a.i. ha~(-1) followed by paraquat at 0.17 kg a.i. ha~(-1) or glyphosate at 0.99 kg a.i. ha~(-1) was more cost effective and superior to manual weeding (p<0.05) at six-week intervals due to minimum weed infestation. Mulching of tea inter-rows with grass loppings (at 38 t. ha~(-1)) was more beneficial for tea than not mulching, whilst a live mulch of weeds suppressed tea growth. A combination of mulching and chemicals followed by manual weeding at 10-week intervals would appear to be the most appropriate integrated weed management system during establishment of young tea.