Plant-soil interactions in multistrata agroforestry in the humid tropicsa |
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Authors: | G Schroth J Lehmann M R L Rodrigues E Barros J L V Macêdo |
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Institution: | 1. Biological Dynamics of Forest Fragments Project, National Institute for Research in the Amazon (INPA), C.P. 478, 69011-970, Manaus-AM, Brazil 2. College of Agriculture and Life Sciences, Department of Crop and Soil Sciences, Cornell University, 909 Bradfield Hall, Ithaca, NY, 14853, USA 3. Embrapa Amaz?nia Ocidental, C.P. 319, 69011-970, Manaus-AM, Brazil 4. National Institute for Research in the Amazon (INPA), C.P. 478, 69011-970, Manaus-AM, Brazil
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Abstract: | Multistrata agroforestry systems with tree crops comprise a variety of land use systems ranging from plantations of coffee,
cacao or tea with shade trees to highly diversified homegardens and multi-storey tree gardens. Research on plant-soil interactions
has concentrated on the former. Tree crop-based land use systems are more efficient in maintaining soil fertility than annual
cropping systems. Certain tree crop plantations have remained productive for many decades, whereas homegardens have existed
in the same place for centuries. However, cases of fertility decline under tree crops, including multistrata agroforestry
systems, have also been reported, and research on the causal factors (both socioeconomic and biophysical) is needed. Plantation
establishment is a critical phase, during which the tree crops require inputs but do not provide economic outputs. In larger
plantations, tree crops are often established together with a leguminous cover crop, whereas in smallholder agriculture, the
initial association with food crops and short-lived cash crops can have both socioeconomic and biological advantages. Fertilizers
applied to, and financed by, such crops can help to `recapitalize' soil fertility and improve the development conditions of
the young tree crops. Favorable effects on soil fertility and crop nutrition have been observed in associations of tree crops
with N2-fixing legume trees, especially under N-deficient conditions. Depending on site conditions, the substitution of legume `service'
trees with fast-growing timber trees may lead to problems of competition for nutrients and water, which may be alleviated
through appropriate planting designs. The reduction of nutrient leaching and the recycling of subsoil nutrients are ways to
increase the availability of nutrients in multistrata systems, and at the same time, reduce negative environmental impacts.
These processes are optimized through fuller occupation of the soil volume by roots, allowing a limited amount of competition
between associated species. The analysis of temporal and spatial patterns of water and nutrient availability within a system
helps to optimize the use of soil resources, e.g., by showing where more plants can be added or fertilizer rates reduced.
Important research topics in multistrata agroforestry include plantation establishment, plant arrangement and management for
maximum complementarity of resource use in space and time, and the optimization of soil biological processes, such as soil
organic matter build-up and the stabilization and improvement of soil structure by roots, fauna and microflora.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | fertility management nutrient cycling spatial and temporal patterns sustainability tree crops |
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