Timber tree-based contour hedgerow system on sloping acid upland soils

As the population pressures in the upland increase, agroforestry is inevitably the most appropriate technology to enhance the productive and protective functions of farming systems to benefit both the people living inside and outside the watersheds in a suitable manner. Contour hedgerow is one of the agroforestry systems suitable for sloping uplands where farmers grow tree crops as hedgerows and food crops as alleycrops. Smallholder farmers in Southeast Asia have begun farming timber trees in association with food crops on fertile soils as the dominant enterprise using their own capital resources. A collaborative study between the International Centre for Research in Agroforestry (ICRAF) and Philippine Nuclear Research Institute (PNRI) was established to evaluate the performance of fast growing timber trees as hedgerows on subsistence cereal based farming systems, and the role of N-fixing trees as interplant in enhancing the growth of the trees as well as the cereal crops. There were 4 fast growing timber trees being compared: Acacia mangium (N-fixing), and Swietenia macrophylla (non-N-fixing), Gmelina arborea (non-N-fixing), Eucalyptus deglupta (non-N-fixing). A. mangium was also used as interplant to determine its influence on the growth of non-N-fixing trees as well as to the cereal crops. Ammonium sulfate enriched with 10.12 15 N atom percent was applied in solution to the upland rice, as alleycrop, at the rate of 60 kg N/ha in the isotope subplot in 2 splits: 30 days after emergence and at panicle initiation stage. This study was conducted in acid upland soil in Claveria, Misamis Oriental.Acacia mangium grew faster compared with G. arborea, E. deglupta, while S. macrophylla grew slower. The growth of E. deglupta and G. arborea was positively affected by N-fixing interplant in low soil fertility environment. G. arborea and A. mangium produced the highest lateral pruning biomass supplying organic nutrients to the associated annual crops. The amount of nutrient yields was proportional to the volume of pruning biomass. Upland rice rows close to the trees had reduced plant height and grain yield. G. arborea was found out to be the most competitive affecting over-all yield of upland rice. But its competitiveness was reduced when interplanted with A. mangium. Grain yield was affected by the different hedgerow species and N-fixing interplant. Row analyses indicated that the first crop of rice was significantly affected by the hedgerow regardless of species. But G. arborea was the most competitive providing the lowest over-all rice yield. Soil nutrients were not affected by the different hedgerow species. Available P was affected by soil depth. Planting of N-fixing timber trees has no significant effect on Fertilizer Nitrogen (FN) yield, % fertilizer Nitrogen Utilization (FNU) of both grain and straw observed on Total Dry Matter Yield (TDMY), Nitrogen Yield (NY), % Nitrogen Derived From Fertilizer (%Ndff) of both grain and straw.This study will be continued to understand more in-depth the tree-soil –crop interactions, particularly on the long term N dynamics of this agroforestry system

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