The effect of herbaceous weed control on planted loblolly pine during a droughtThis article is part of a larger document. View the larger document here.
Seedling survival in loblolly pine (Pinus taeda L.) plantation establishment is often mentioned as a justification for herbaceous weed control (HWC). However, the effects of HWC treatment during drought have been difficult to find. Sometimes this research was proprietary in nature. Also, since weather patterns vary from year to year, drought may not have coincided with a research study.In the spring of 2007, a demonstration for a HWC comparison was installed on retired pasture at the North Branch Station near Holly Springs, MS. Second-generation loblolly seedlings from Weyerhaeuser were planted using a 10- by 10-foot spacing on March 27. Approximately half the area received HWC, and the other half did not (control). Broadcast HWC was simulated with a two-pass operation approximately 1 month after planting. The first pass was a 4-ounces Arsenal AC® plus 2- ounces Oust® mix sprayed at 15 gallons per acre (GPA) in a 5-foot band over the seedlings. The second pass was 32 ounces glyphosate in 15 GPA sprayed between the rows. Three measurement plots of one-tenth acre were randomly located on each treatment: control (no treatment) versus broadcast HWC. Initial measurements were taken August 14, 2007. Average survival on control plots was 84.4 percent, and 83.9 percent on treated plots. There was a late summer drought that growing season, so the study was measured again in mid-February 2008. Average stocking on control plots was 230 trees per acre, and survival was 37.1 percent. Treated plots, on the other hand, had an average 433 trees per acre and 74.7 percent survival. Broadcast HWC can affect survival of young pine plantations during drought years.