Academic journal article Southeast Asian Studies

Farmers' Perceptions of Imperata Cylindrica Infestation in a Slash-and-Burn Cultivation Area of Northern Lao PDR

Academic journal article Southeast Asian Studies

Farmers' Perceptions of Imperata Cylindrica Infestation in a Slash-and-Burn Cultivation Area of Northern Lao PDR

Article excerpt

I Introduction

Slash-and-burn cultivation (SBC), also called shifting cultivation, is an important food production system widely practiced in the tropical mountainous regions of Southeast Asia (Rasul and Gopal 2003). SBC practices, which involve repeated cycles of slashing and burning of secondary forest or shrub vegetation, temporarily growing crops, and then letting the land revert to secondary forest growth or fallows, are similar throughout the region. In Laos, the SBC system is practiced in about 13% of the land by 39% of the total population (JICA 2001) and is viewed by the government as an unsustainable form of land use. It needs to be replaced with more permanent and productive land use systems.

The SBC system in Laos has been less and less productive in recent decades as a result of the reduction of fallow periods and the introduction of new species of weeds. Average fallow periods reported for the 1950s, 1970s, 1990s, and 2000s were 38, 20, 5, and 2-3 years respectively (Roder et al. 1997; Saito et al. 2006). Short fallow periods serve to increase weed infestation in upland rice (Roder et al. 1995), deteriorate soil fertility (Gourou 1942; Whitaker et al. 1972; Brown and Lugo 1990; Fujisaka 1991), and lead to a decline in non-timber forest products (NTFPs) (Foppes and Ketphanh 2005). The increase in population coupled with improper planning and implementation of upland development policies in many SBC areas has resulted in more land shortages and rural poverty (ADB 2001; Jones et al. 2005).

Imperata cylindrica is one of the most dominant, competitive, and difficult weeds to control in the humid and sub-humid tropics of Asia, West Africa, and Latin America. It is one of the most stubborn weeds in both SBC as well as intensive agriculture in West Africa (Chikoye et al. 1999; 2002). Lao upland farmers in the north perceive Imperata to be one of the most important weeds after Ageratum conyzoides, Chromolaena odorata, Commelina spp., Panicum trichoides, and Lygodium flexuosum and one of the most undesirable fallow species after Cratoxylon prunifolium and Symplocos racemosa in slash-and-burn rice systems (Roder et al. 1995; 1997). Imperata is also perceived as a key indicator of poor soil and land degradation (Saito et al. 2006; Lestrelin et al. 2010).

There may be as much as 57 million hectares of Imperata grassland in Asia, about 25 million hectares of which is in Southeast Asia. In Laos, Imperata was reported to have the potential to invade 0.8-1 million hectares (World Bank and Australian International Development Assistance Bureau 1989; Garrity et al. 1997), a figure that is expected to have increased in recent decades. There are primarily two reasons for this: shortened fallow periods, due to which the suppression of aggressive weeds such as Imperata cylindrica is less effective; and/or intensive use of short fallow lands for crop production where Imperata is still dominant.

Our study on the spatial distribution of Imperata grassland (characterized as a "micro-grassland") in northern Laos revealed that it was unevenly distributed throughout the study area (Fig. 1). In addition, the study found that increased land use intensification through diversifying SBC areas into more permanent crop production systems was strongly correlated with the spread of Imperata grassland (Keoboualapha et al. 2013). The purpose of this study was to capture the local perceptions of such infestation and its impacts on agriculture. The more specific objectives of the study were: (1) to characterize the main agricultural land uses and major crops in the most Imperata-infested area of Nambak District in Luang Prabang Province, northern Laos; (2) to estimate the extent of and describe Imperata infestation at the household level as perceived by affected farmers; and (3) to identify the existing strategies and constraints in dealing with Imperata infestation. The findings of this study will highlight the significance of Imperata grassland to concerned research and development communities as a crucial issue for sustainable development in the uplands of Laos. …

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