Thinning and Fertilizing Southern Pine Stands of the Lower Coastal Plain: Biological and Economic Effects
Abstract The interaction between thinning and fertilization (nitrogen and phosphorus) was investigated in seven slash pine (Pinus elliottii Engelm. var. elliottii) plantations and one natural loblolly pine (Pinus taeda L.) stand in the lower Coastal Plain of the southeastern United States. Thestands ranged in age from 14-20 years when the 2² factorial (thinning X fertilization) experiments were installed. Significant thinning X fertilization interactions occurred on five tests, but the nature of the interactions was inconsistent. Fertilization responses remained significant8 years after treatment and averaged 35 ft³/ac/yr. Fertilization increased stand volume production in the chip-n-saw product class more frequently than thinning. After 8 years, thinning increased individual tree volume growth by 0.50-3.05 ft³/tree over the controls; however, thinninggenerally decreased both total stand and chip-n-saw volumes at final harvest. Economic effects were examined by determining soil expectation values (SEV) for each thinning and fertilization treatment combination for various rotation lengths using uniform economic assumptions. The treatmentcombination that maximized stand volume production was not always the best financial choice. The increased growth rates due to thinning, fertilization, or both tended to extend the optimal rotation. A 4% real cost of capital with harvest merchandizing of pulpwood and chip-n-saw product classeseconomically favored fertilization over the other treatments. However, increasing the cost of capital (6% real) or merchandizing solely for pulpwood put fertilization at a relative disadvantage. South. J. Appl. For. 16(4):186-193