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 ploughing and complete ploughing on the performance of Acacia mangium were compared. In the second trial the effects of complete ploughing, herbicide treatment and NPK fertilizer application were compared for four tree species commonly used in I. cylindrica grassland reforestation. Complete ploughing resulted in a threefold volume increment of A. mangium compared with strip cultivation. Coverage and height of I. cylindrica were lower in plots treated with complete ploughing. Complete ploughing and initial fertilizer application 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 age 36 months were 9.5 m³, 31.4 m³, 36.7 m³ and 0.5 m³ for G. arborea, P. falcataria, A. mangium and S. macrophylla, respectively. Intensive mechanical site preparation and fertilizer treatment are recommended in I. cylindrica grassland reforestation, as they clearly accelerate initial growth of trees. Strip treatments must not be used in grasslands. Further research on the effects of fertilizers is needed.