Responses of Fraxinus griffithii C.B. clarke to fertilizer application and weed control

Effects of fertilization and weed control on growth of Fraxinus griffithii C.B.Clarke. The treatments consisted of fertilizer application, NPK (15-15-15) 10 gm/tree/year and control, in combination with four treatments of weed control (twice manual weeding per year, oxyfluorfen 0.5 kg (ai)/ha and oxyfluorfen 0.5 kg(ai)/ha + glyphosate 1.5 kg(ai)/ha, oxyfluorfen 1.0 kg (ai)/ha and oxyfluorfen 1.0 kg(ai)/ha + glyphosate 2.0 kg(ai)/ha, and control. Fertilizer was applied in June. Manual weeding and herbicide applications were carried out twice, in June and October. Diameters at root collar and total height were measured every 3 months since the first fertilization and weed control. The analysis of variance and Duncan's new multiple-range test techniques were used for statistical interpretation. Weed control ratings were recorded 30 days and 45 days after the first treatment of weed control and 45 days, 145 days, and 250 days after the second treatment of weed control. Diameter at root collar and total height of seedlings did not respond to fertilizer application at the rate of 10 gm/tree/year, while the positive response to weed control was found on diameter and height growths. The response of Fraxinus griffithii to herbicide applications was different from manual control. Tree growth affected by manual weeding was less than that of herbicide application. Several advantageous effects of herbicide application were found to be true over the manual weeding including weed control rating. There was no interaction between fertilization and weed control. The current findings suggested that weed control was necessary to stimulate diameter and height growth of Fraxinus griffithii. Oxyfluorfen applied in June at the rate of 0.5 kg(ai)/ha together with 0.5 kg(ai)/ha oxyfluorfen+1.5 kg(ai)/ha glyphosate applied in October were the most favorable treatments of weed controlling during the first year at Angkhang planting site.