From Imperata cylindrica grasslands to productive agroforestry

Conversion of an Imperata cylindrica ecosystem into an agroforestry ecosystem is a complex process. Integrated control of the I. cylindrica grass is needed in combination with planting deep-rooted pioneer tree species, a legume cover crop and annual food crops. I. cylindrica grasslands are generally poor in nutrients, but they are not necessarily poor from a soil biological perspective and may contain high densities of mycorrhizal spores. Experiments in the nursery and in the field were conducted to provide the knowledge needed to design and improve smallholder options for converting I. cylindrica grasslands into productive and sustainable agroftroresy systems. Inoculation with mycorrhizal fungi (resting spores in ‘Mycofer’ belonging to Glomus manihotis, Glomus etunicatum, Gigaspora rosea and Acaulospora tuberculata), did not promote tree seedling growth in the nursery, but it leads to a significant increase in survival rate of the four tree species tested, once these were transplanted to the field. However, this rate increased by 6.5°/e only. Nursery inoculation of the trees did not have any positive effect on the subsequent growth of those trees that survived the critical early stage. There is no compelling need for the use of the inoculum of the type used in the nursery. The perfonnance of three out of four selected tree species growing in the alang-alang grassland, and their capability to outshade the grass, mahogany (Swietenia macrophvlla King, Meliaceae), sungkai (Peronema canescens Jack., Verbenaceae) and candle nut(Aleurires moluccana (L.) Wilid., Euphorbiaceae) made them most suitable to be planted in those useless lands. Breadfruit or sukun (Artcx’arpus altilis Fosberg, Moraceae) proved itself unsuitable for the harsh conditions of large parts of the I. cvtindrica grasslands. It only performed well in specific sites. The field experiments showed no statistically significant differences in tree growth linked to the method used for initial alang-alang suppression. Ploughing, herbicide use or the simple pressing’ method all proved acceptable as part of the overall system used. Spraying herbicide and ploughing are the most efficient methods to reduce alang-alang biomass. Pressing is the cheapest method to prepare acceptable tree growth, but is less attractive for inter-cropping. As a cover crop, able to outshade alang-alang after one year, to prevent its recovery and to improve soil fertility at the same time, Puerariajavanica (Leguminosae-Fabaceae) is a good option. An overall tree-LAI

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