In May 1987, hexazinone (Velpar® L) was applied by helicopter at 0, 1, 2, and 4 kg active ingredient (a.i.) in 45 L of total solution per ha to a sandy loam site approximately 74 km northwest of Thunder Bay, Ontario. Container (FH408 paper pot)jack pine (Pinus banksiana Lamb.) and container (FH408 paper pot) and bareroot (1½ + 1½) black spruce (Picea mariana [Mill.] B.S.P.) were hot-planted 1 month and deferred-planted 12 months after herbicide application. Survival, height, and diameter growth were monitored annually, through the fall of 1991. Jack pine container stock planted 1 month after hexazinone treatment at 2 and 4 kg a.i./ha suffered 12% greater mortality than trees planted 1 yr later. However, the benefits of early establishment and herbaceous weed control offset these early losses and hot-planted areas supported equal volumes at age 4, and 2.3-fold more volume per ha than deferred-planted areas 5 growing seasons after herbicide treatment. Black spruce container and bareroot stock exhibited high tolerance to hexazinone throughout the range of rates tested. Overall, a 1 yr delay in planting resulted in stem and stand volumes that were less than half of those observed in hot-planted areas. Growth response was positively related to the level of herbaceous weed control achieved, with 4 kg treated areas supporting volumes 2- to 4-fold greater than those on untreated areas. The data illustrate significant growth advantages associated with early crop establishment and herbaceous weed control. North. J. Appl. For. 16(2):72-81.
Document Type: Journal Article
Plant Community Consultants, Ltd., 11 Country Club Place, Sault Ste. Marie, Ontario P6A 5Z8
Publication date: June 1, 1999
More about this publication?
Each regional journal of applied forestry focuses on research, practice, and techniques targeted to foresters and allied professionals in specific regions of the United States and Canada. The Northern Journal of Applied Forestry covers northeastern, midwestern, and boreal forests in the United States and Canada.