Fertilization of Established Southern Pine Stands: Effects of Single and Split Nitrogen Treatments

Abstract

Abstract Data from six fertilizer trials established in semimature southern pine stands (five slash pine, Pinus elliottii Engelm. var. elliottii; one loblolly pine, Pinus taeda L.) were analyzed to determine the efficacy of single vs. split fertilizer treatments. Both fertilizer treatments supplied an elemental equivalent of 200 lb nitrogen (N)/ac and 50 lb phosphorus (P)/ac; however, the first treatment was delivered as a single dose, and the second treatment was a split N application (i.e., 50 lb N and 50 lb P/ac (initial); 150 lb N/ac (2 yr later). Cumulative responses of fertilized plots were still significantly greater than the controls in five trials after 8 yr and averaged 43% (15.7 ft²/ac) and 39% (607 ft³/ac) for basal area and stand volume growth, respectively. In general, no significant differences in either the magnitude or duration of response were detected between the single and split N fertilizer treatments. This suggests that delaying a portion of the N application for 2 yr will not diminish the level of growth responses attained. Therefore, land managers have flexibility in using either application method when implementing midrotation fertilizer prescriptions. South. J. Appl. For. 17(3):135-138.