Effect of site preparation and initial fertilization on the establishment and growth of four plantation tree species used in reforestation of Imperata cylindrica (L.) Beauv. dominated grasslands

Abstract

Site preparation methods used in reforestation of Imperata cylindrica grasslands were studied in South Kalimantan, Indonesia. In the first trial the effects of strip plowing and complete plowing on the performance of Acacia mangium were compared. In the second trial the effects of complete plowing, herbicide treatment and fertilization (NPK) were compared with four tree species commonly used in Imperata grassland reforestation. Complete plowing resulted in threefold volume increment of Acacia mangium compared with strip cultivation. Coverage and height of I. cylindrica were lower in plots treated with complete plowing. Complete plowing with initial fertilization was the most effective method for stand establishment for Gmelina arborea, Paraserianthes falcataria and Acacia mangium. Swietenia macrophylla did not respond to the treatments. The response to the treatments was clearest with Paraserianthes falcataria. The highest mean annual volume increment estimates at the age of 36 months were 9.5 m 3, 31.4 m 3, 36.7 m 3 and 0.5 m 3 for G. arborea, P. falcataria, A. mangium and S. macrophylla, respectively. Intensive mechanical site preparation and fertilization are recommended in I. cylindrica grassland reforestation, as they clearly speed up the initial growth of trees. Strip treatments must not be used in grasslands. Further research on the effects of fertilization is needed.