Soil Fertility and Farming Systems in a Slash and Burn Cultivation Area of Northern Laos(<Special Issue>Sustainable Agro-resources Management in the Mountainous Region of Mainland Southeast Asia)

Abstract

The physico-chemical properties of the soil in shifting cultivation fields in Xiang Ngeun district, Luang Phabang province were investigated in order to provide a basis for developing an agricultural system that will be sustainable under higher population pressure on the land and increased demand to engage in intensive farming. The soils in the study area have reasonably high contents of soil nutrients despite being on erosion-prone sloping land. Soil fertility status may not be fully restored even when the length of fallow is 10 years. The nutrients accumulated in the soil during fallow period are small compared with the nutrients supplied from the ash input when the biomass is burned so that soil nutrients were found not to be exhausted after a single year of cultivation. However, the density of weeds increases as the fallow period is shortened. Therefore, fallow plays an important role in weed control during the cropping period. These findings suggest that an agroforestry system that combines crop cultivation with paper mulberry production could be a sustainable farming system for short-fallow shifting cultivation. To be acceptable to the farmers, this agroforestry system must be effective both in controlling weeds and in generating income for the shifting cultivators.