Effects of nitrogen sources on the wood properties of Gmelina arborea relevant to pulp and paper production

Abstract

The effects of different nitrogen sources and levels of application on the physical and histological properties, and on resultant values relevant to pulp and paper production, Gmelina arborea seedlings on latosolic soil were investigated. The nitrogen sources were: nitrate-nitrogen (NO 3N) supplied as potassium nitrate (KNO 3), ammonium-nitrogen (NH 4N) given as ammonium sulphate (NH 4) 2SO 4, ammonium nitrate-nitrogen (NH 4NO 3N) applied as calcium ammonium nitrate (CaNH 4(NO 3) 2) and urea-nitrogen (urea-N) fed as compound urea. The levels of application were 0.0, 2.5, 5.0 and 7.5 g N per plant. The control treatment received no form of nitrogen fertilizer. All the nitrogen sources improved the specific gravity of gmelina wood on latosolic soil. The longest fibre cells were produced with NO 3N and the shortest with NH 4N. Urea-N produced the narrowest fibre cells while NH 4N produced the widest fibres with the thickest walls. The coefficient of suppleness was not affected by the nitrogen sources. In relation to the control trees, urea-N and NO 3N sources produced a significantly higher slenderness ratio. Runkel ratios obtained with the various nitrogen sources were homogeneous. In nearly all the parameters measured, the optimal values were recorded with the first level of nitrogen application (2.5 g N per plant). The implications of the findings on pulp and paper production using G. arborea grown on latosolic soil are discussed.