Decision-Making Aid for Loblolly and Slash Pine Mid-Rotation Fertilization

Dr. E. David Dickens - Assistant Professor of Forest Productivity, Warnell School of Forest Resources, The University of Georgia

Stand Criteria:

• Loblolly/slash pine stocking - 400 to 900 TPA (young stand) or 60-90 sq ft BA/ac (< 120 BA/ac)
• Best trees/best genes present on site?
• Hardwood stocking < 10% of BA/ac
• Fusiform rust incidence < 30%
• Live crown ratio (goes with stocking) >35% to 40%

Soils criteria:

• Drainage class - very poorly drained to excessively well drained (for flatwoods use CRIFF soil groups for P fertilization at planting)
• Soil water holding capacity (poor internal drainage or deep sands can present problems)
• Depth to bedrock, fragipan, or pan (highly eroded or shallow soils to bedrock are problems)
• Soil texture (% sand, silt, clay)
• Soil series/group classification

Landowner objectives/ cutting regime:

• Years to next thinning or final cut (ideal is 6-10 years)
• Owner finances (how many acres can they afford to fertilize, may need to prioritize stands for fertilization) income from thinning can be used to pay for fertilization

Diagnostic Tool Information:

• Leaf Area Index (LAI) -done in July-August, if < 3.0 then stand could use N (or N+P)
• Foliar test - if N or N and P less than 1.2% (N) and 0.10% (P)  for loblolly pine and 0.8-1.2% (N) and 0.08-0.09% (P) for slash pine, then stand could use N or N and P
• Soil test -P - if P (using double acid extract or Mehlich I procedure) < 8-12 lb/ac, then stand could use P for both loblolly and slash pine