Loblolly Pine Stand Fertilization at Mid-rotation to Increase Small and Large Sawtimber Volume
IPNI-2004-USA-GA26
25 Feb 2010
2009 Annual Interpretive Summary
Two fertilizer trials and an untreated control were established in 2004 near Bullard, Georgia, within a loblolly pine tree stand planted in 1978 and thinned in 2002-03. The objectives of the study were to:
- quantify the magnitude and duration of wood volume response to various fertilizer combinations,
- determine changes in product class distribution,
- determine the cash flow and rate of return for each fertilizer combination compared to unfertilized control plots, and
- discern when fertilizers are to be re-applied to maintain wood volume gain.
Fertilizer treatments examined NP, NPK, and NPKSCu in one trial and NP, NPCu, NPKCu, and NPKSCu in a second trial. The one-time fertilizer applications were applied in February 2005. Fertilizer levels applied per acre were 200 lb N, 50 lb P, 80 lb K, 60 lb S, and 5 lb Cu.
Data (4-year) were collected in January 2009. There were significant differences in 4-year growth increment for diameter as the control (0.883 in.) was significantly less than treatments supplying NP (1.02 in.), NPKCu (1.07 in.), and NPKSCu (0.963 in.). The volume per tree measurements were also significant with the control being significantly less than all fertilizer treatments. The NPKCu treatment had significantly greater volume per tree increment (4.1 cubic feet) than all other treatments except the NP treatment (4.0 cubic feet). There were no significant growth increment differences amongst treatments for trees per acre, diameter, height, live crown ratio, or volume per acre during the second measurement period (2007 to 2009). However, there were significant volume per tree differences for the 2007 to 2009 growth increment with the NPKCu treatment being significantly greater than the control and NPCu treatments. Pulpwood, superpulp, chip-n-saw, and sawtimber volumes will be estimated and tested for differences in early 2010. GA-26F