s:1870:"%T Spatial variability of soil pH and phosphorous in relation to soil run-off following slash-and-burn land clearing in Sumatra, Indonesia 
%A Rodenburg, J. 
%A Stein, A. 
%A Ketterings, Q.M. 
%A Van, Noordwijk.M. 
%X Slash-and-burn land clearing on sloping land may lead to increased soil run-off following disappearance of the protective vegetative cover. In turn soil run-off and redeposition affects soil fertility and spatial patterns of fertility parameters in a field. This study seeks to clarify the role of spatial patterns of post-burn dead biomass (necromass) in soil run-off and redeposition and their combined effect on spatial patterns in soil pH and resin-extractable P. The study is carried out on a post-productive rubber (Hevea brasiliensis) agroforest in Sumatra Indonesia. Soils are classified as Dystric Fluvisols. After slash-and-burn of vegetation the field was planted with rubber seedlings and rice (Oryza sativa). For comparison the adjacent rubber agroforest site was sampled. Soil run-off is expressed here as the quantity of downward moving soil that passed the specific location of a flow trap. Existing physical soil run-off barriers and crop performance were scored. Despite serious soil run-off from the steeper upper slopes little soil was actually lost because of the slope form of the field presence of natural soil run-off barriers and the planted crop. Spatial variability of soil pH decreased at the expense of small-scale within-strata variability mainly because of the patchy distribution of soil run-off barriers. Soil run-off aggravated by slash-and-burn did not result in development of a clear soil fertility gradient down slope. In areas of high soil run-off potential clear burns should be avoided because soil run-off barriers like remnants of slash-and-burn and surface litter maintain the soil and its fertility. 
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