Effects of Fertilization and Endophyte Application on Growth of Planted Longleaf Pine

Abstract

Longleaf pine (Pinus palustris) is an important economic and ecological species in the Southeast. The removal of fire from southeastern forests and a landowner preference for loblolly pine (P. taeda) and slash pine (P. elliottii) has resulted in a major decrease of the range of longleaf pine. This study investigates the potential of two fertilization methods and inoculation with diazotrophic endophytes to reduce time in the grass stage and improve diameter growth in longleaf pine. The study area was located in Clarke County, Mississippi, on soils that consisted of a mix of fine sands and sandy clays. A total of four treatments were applied in a randomized complete block design to a recently clearcut stand. The site was chemically prepped prior to establishment. Treatments included control, broadcast fertilizer [nitrogen (N)-phosphorus (P)-potassium (K) 32-14-5] applied at a rate of 35 pounds per acre, and controlled release fertilizer bags (NPK 19-8-3) applied adjacent to each seedling. Diazotrophic endophytes were also applied in a separate treatment adjacent to each planted seedling 1 year following establishment. We measured root collar diameter (r.c.d.), survival, and the number of seedlings that had initiated height growth. Overall r.c.d. and grass stage emergence did not show a significant difference during second year measurements for both fertilization treatments and endophyte inoculation. Survival, however, was significantly lower in the broadcast fertilization treatment compared to the control. Increased competition from shrubs, grasses, and naturally regenerated loblolly pine in broadcast fertilization plots likely contributed to the low survival. Reducing time spent in the grass stage may help re-establish longleaf pine to its native range and increase ecological diversity across the Southeast.

Parent Publication

• Proceedings of the 22nd Biennial Southern Silvicultural Research Conference

Citation

Doughty, Baylor; Polinko, Adam; Siegert, Courtney. 2024. Effects of Fertilization and Endophyte Application on Growth of Planted Longleaf Pine. In: Bragg, Don C.; Oswald, Brian P.; Koerth, Nancy E., eds. Proceedings of the 22nd biennial southern silvicultural research conference. Gen. Tech. Rep. SRS-274. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station: 294–299. https://doi.org/10.2737/SRS-GTR-274-Pap45.