Impact of Glyphosate on Weed Biomass and Growth of Coconut Seedlings in Nurseries

The effects of five different weed management systems on growth of coconut seedlings were evaluated to determine an economical and effective method for controlling weeds in coconut nurseries in the low country of the wet zone in Sri Lanka. The treatments comprised of manual weeding (T1), application of glyphosate at 1.44 kg ai/ha (T2), 1.08 kg ai/ha (T3), 0.72 kg ai/ha (T4) and 0.36 kg ai/ha (T5) applied at three-month intervals. Treatments 1 and 2 significantly reduced the weed biomass when compared to other treatments. The growth of coconut seedlings (in terms of height and girth) increased significantly (P<0.05) with the application of glyphosate at 1.08 kg ai/ha (T3) at the end of the nursery growth period. At the higher concentration (1.44 kg ai/ha) the growth of seedlings was reduced at the latter part of the experiment. Therefore, the most costeffective treatment of controlling weeds in the study was to apply glyphosate at the rate of 1.08 kg ai/ha (3l of commercial mixture/ha). Manual weeding was neither effective no economical. DOI: http://dx.doi.org/10.4038/cocos.v19i1.475