|Dickens, E.D. -|
Submitted to: The Open Forest Science Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 16, 2010
Publication Date: August 1, 2010
Citation: Burner, D.M., Pote, D.H., Mackown, C.T., Dickens, E. 2010. Growth and soil nutrient responses to stocking rate and nitrogen source for mid-rotation loblolly pine in west-central Arkansas. Open Forest Science Journal. 3:9-16. Interpretive Summary: Development and expansion of a pine straw industry is anticipated for the west-central US due to the large area of pine forestland, enhanced awareness of the economic value associated with pine straw harvesting, increased demand for natural landscaping products, and a large poultry industry providing a convenient fertilizer source in relatively close proximity to pine forests. Pine straw harvesting removes valuable nutrients which should be replaced by periodic fertilization, but fertilization does not always show a benefit by increasing tree productivity. A collaborative study between ARS-Booneville, ARS-El Reno, and the University of Georgia was conducted to determine if number of trees/ha (stocking) and fertilization affected tree growth, pine straw yield, and plant and soil nutrients in loblolly pine at about mid-rotation (12-14 yr post-planting). Stocking had a greater effect than fertilization on tree growth, probably because there were too many trees per unit area for them to adequately utilize the fertilizer nutrients. With pre-thinning applications having little to no benefit on pine growth or pine straw yield, landowners should defer fertilization of pine stands until after the first thinning to avoid waste of costly fertilizer. These particular stands need to be thinned for improved growth responses in the future.
Technical Abstract: Fertilization is needed to replace nutrients removed from pine straw plantations, but response to fertilization could be influenced by stocking rate. Our objective was to determine effects of three N fertilizer sources on loblolly pine (Pinus taeda L.) growth and pine straw yield as a function of stocking rate (trees/ha, TPH) at about mid-rotation (12-14 yr post-planting). Commercial mineral fertilizer (CF), poultry litter (PL, 5.4 Mg/ha), and pelletized poultry litter (PPL, 4.6 Mg/ha) were applied once in April 2006 at 0 (control) and 200 kg/ha of N to stocking rates of 2300, 1200, and 970 TPH near Booneville, Arkansas. Basal area (range 32.6 to 42.8 sq m/ha) was very high and did not respond to fertilization, and fertilization did not consistently increase pine straw yield compared to the control. Concentrations of pine straw N and foliar N increased with fertilization, especially with CF compared to litter. Topsoil nitrate-N and ammonium-N were greater for CF than PL and PPL 3 mo after fertilization, but responses at or beyond 9 mo after application did not differ from the control. Overstocking appeared to constrain tree growth, foliar N, and pine straw yield responses to fertilizer additions. Thinning should improve tree growth and pine straw yield responses to fertilizer applied at mid-rotation.