Fertilization response in a natural bottomland hardwood stand in north-central Louisiana

The effect of nitrogen and phosphorus fertilization on growth of a natural bottomland hardwood stand in north-central Louisiana was evaluated. A typic al mixed stand of pole-sized and small saw-timber bottomland hardwoods with about 23.7 m(2) ha(-1) of basal area was used in the study. Soils were Guy ton silt loam (Fine-silty, siliceous, thermic Typic Glossaqualf). Three fer tilizer treatments plus a control were replicated three times on 0.1 ha plo ts. The treatments consisted of nitrogen (168 kg ha(-1)) as ammonium nitrat e, phosphorus (56 kg ha(-1)) as triple super phosphate, and N+P. Trees grea ter than 10 cm at dbh were measured for diameter before fertilization and r emeasured after one and two growing seasons. Diameter increment served as t he response variable. Results showed a statistically significant (p<0.05) i ncrease (70 pet greater than the control) in diameter growth for the 2 year total increment on the N+P treatment with all species combined. While the small sample size and relatively high amount of variability resulted in no further statistical significance among the treatments, the data did reveal trends that need further investigation. Sweetgum (Liquidambar styraciflua L .) responded to N alone, while the oaks (Quercus), especially the white oak s, responded to P alone. The oaks also responded to N+P, while no similar r esponse was seen from sweetgum for that treatment. (C) 1999 Elsevier Scienc e B.V. All rights reserved.