@article{fdi:010042795,
  title = {{R}unoff and sediment losses from 27 upland catchments in {S}outheast {A}sia: {I}mpact of rapid land use changes and conservation practices},
  author = {{V}alentin, {C}hristian and {A}gus, {F}. and {A}lamban, {R}. and {B}oosaner, {A}. and {B}ricquet, {J}ean-{P}ierre and {C}haplot, {V}incent and {G}uzman de, {T}. and {D}e {R}ouw, {A}nneke and {J}aneau, {J}ean-{L}ouis and {O}range, {D}idier and {P}hachomphonh, {K}. and {P}hai, {D}. {D}. and {P}odwojewski, {P}ascal and {R}ibolzi, {O}livier and {S}ilvera, {N}orbert and {S}ubagyono, {K}. and {T}hi{\'e}baux, {J}ean-{P}ierre and {T}oan, {T}. {D}. and {V}adari, {T}.},
  editor = {},
  language = {{ENG}},
  abstract = {{R}apid changes in upland farming systems in {S}outheast {A}sia generated predominantly by increased population pressure and 'market forces' have resulted in widespread land degradation that has been well documented at the plot scale. {Y}et, the links between agricultural activities in the uplands and downstream off-site effects remain largely unknown because of the difficulties in transferring results from plots to a larger scale. {M}any authors have thus pointed out the need for long-term catchment studies. {T}he objective of this paper is to summarize the results obtained by the {M}anagement of {S}oil {E}rosion {C}onsortium ({MSEC}) over the last 5 years from 27 catchments in five countries ({I}ndonesia, {L}aos, {P}hilippines, {T}hailand, and {V}ietnam). {T}he purpose of the study was to assess the impacts of cultivation practices on annual runoff and erosion rates. {I}nitial surveys in each catchment included topography, soils and land use. {M}onitoring included climatic, hydrologic and erosion (total sediment yield including bed load and suspended sediment load) data, land use and crop yields, and farmers' income. {I}n addition, new land management options were introduced through consultations with farmers and evaluated in terms of runoff and erosion. {T}hese included tree plantations, fruit trees, improved fallow with legumes, maize intercropped with legumes, planted fodder, native grass strips and agro-ecological practices (direct sowing and mulch-based conservation agriculture). {R}egressions analyses showed that runoff during the rainy season, and normalized runoff flow coefficient based on erosive rainfall during the rainy season (rainfall with intensity exceeding 25 mm h(-1)) increase with the percentage of the catchment covered by maize. {B}oth variables decrease with increasing soil depth, standard deviation of catchment slope (that reflects terrain roughness), and the percentages of the catchment covered by fallow (regular and improved), tree plantations and planted fodder. {T}he best predictors of sediment yield were the surface percentages of maize, {J}ob's tears, cassava and footpaths. {T}he main conclusions generated from this study were: (i) soil erosion is predominantly influenced by land use rather than environmental characteristics not only at the plot scale but also at the catchment scale; (ii) slash-and-burn shifting cultivation with sufficiently long rotations ({I} year of cultivation, 8 years of fallow) is too often unjustly blamed for degradation; (iii) in its place, continuous cropping of maize and cassava promotes high rates of soil erosion at the catchment scale; (iv) conservation technologies are efficient in reducing runoff and total sediment yield at the catchment scale; (v) the adoption of improved soil management technologies by upland farmers is not a function of the degree of intensification of their farming system and/or of their incomes. {T}he results suggest that if expansion of maize and cassava into already degraded upland systems were to occur due to increased demand for biofuels, there is a risk of higher runoff and sediment generation. {A} failure to adopt appropriate land use management strategies will result in further rapid resource degradation with negative impacts to downstream communities.},
  keywords = {{S}oil erosion ; {U}pland rice ; {M}aize ; {C}assava ; {S}hifting cultivation ; {S}teep slopes},
  booktitle = {},
  journal = {{A}griculture {E}cosystems and {E}nvironment},
  volume = {128},
  numero = {4},
  pages = {225--238},
  ISSN = {0167-8809},
  year = {2008},
  DOI = {10.1016/j.agee.2008.06.004},
  URL = {https://www.documentation.ird.fr/hor/fdi:010042795},
}