Fertilization Increases the Return on US Pine Forest Farming

Loblolly pine is the most important commercial pine tree grown in the southern United States, with unmanaged forests taking up to 50 years to mature and managed plots maturing in as little as 20 years. Although loblolly pine responds very well to management including fertilization, thinning, and removing woody vegetation, little is known about how much extra wood or added economic value late fertilization after thinning produces.

Working with the University of Georgia, IPNI conducted a series of studies to determine how much growth and value was gained from applying fertilizers to thinned loblolly pine stands. The research compared the growth of unfertilized trees over a 6 to 8-year growth period to trees that received fertilizer.

On study areas with low soil fertility, loblolly pine growth was greatly improved by the single per acre dose of 91 kg N and 23 kg P. When foliar K concentrations were low, the addition of K fertilizer provided an additional growth advantage.

The trees that received fertilizer and where woody vegetation was controlled produced an additional 1 to 1.5 tons of wood per acre per year compared to the untreated control plots. Additionally, fertilizer treatment improved the wood class distribution resulting in more valuable sawtimber sized trees.

Forest fertilization improved profitability by US$250 to $700/acre over the 8-year study period. The return on fertilizer investment ranged from 4 to 20% in the study sites, with an 8 to 15% economic return being the most common. The study clearly showed that loblolly pine producers can improve both the growth and value of their trees through fertilization.