Crop-livestock integration provides opportunities to mitigate environmental trade-offs in transitioning smallholder agricultural systems of the Greater Mekong Subregion

CONTEXT: The Greater Mekong Subregion has been undergoing rapid agricultural transformation over the last
decades, as traditional diverse subsistence-oriented agriculture is evolving towards intensified commercial
production systems. Negative environmental impacts often include deforestation, nutrient pollution, and
greenhouse gas (GHG) emissions.
OBJECTIVE: This study aims to explore the potential of crop-livestock integration to mitigate trade-offs between
economic and environmental impacts of smallholder farming systems at different stages of agricultural transition
and degrees of agricultural diversity across the Greater Mekong Subregion.
METHODS: We chose a ‘middle ground’ between detailed modeling of few, representative farming systems and
modeling of large household populations. 24 low and high diversity farms were selected in Laos (Xieng Khouang
province), Cambodia (Ratanakiri province) and Vietnam (Central Highlands) from a survey dataset of 1300
households. These farming systems were simulated with the whole-farm bio-economic and multi-objective
optimization model FarmDESIGN, calculating operating profit, GHG emissions and nitrogen (N) balance. Two
optimizations (‘business as usual’ vs. ‘crop-livestock integration’) were performed, generating ‘solution spaces’ or
alternative configurations aiming to maximize profitability, keep farm N balanced and minimize GHG emissions.
RESULTS AND CONCLUSIONS: Agricultural systems across the sites differed in their production orientation and
management practices, representing various stages of agricultural transition. Nitrogen balances varied between
sites, being negative in Ratanakiri (average 􀀀 20.5 kg N ha􀀀 1 y􀀀 1) and Xieng Khouang (􀀀 36.5 kg N ha􀀀 1 y􀀀 1) and
positive in the Central Highlands (73 kg N ha􀀀 1 y􀀀 1). Negative balances point to unsustainable mining of nutrients
due to sale of cash crops without sufficient inputs, and positive balances to the risk of environmental
contamination. Total GHG emissions ranged from 0.52–8.12 t CO2e ha􀀀 1 and were not significantly impacted by
stage of agricultural transformation or agricultural diversity. GHG sources in Ratanakiri and Xieng Khouang were
determined by crop residue burning while in Central Highlands fertilizer and livestock were main emitters. High
diversity farms obtained higher operating profits (10,379 USD y􀀀 1) than low diversity farms (4584 USD y􀀀 1).
Crop-livestock integration, a combination of measures including introduction of improved forages grasses,
manure recycling and residue feeding, and reduction of residue burning, resulted in larger ‘solution spaces’, thus
providing farmers with more options to mitigate agro-environmental trade-offs.
SIGNIFICANCE: These findings underline the potential of crop-livestock integration to support sustainable
intensification pathways in the Greater Mekong region. Public and private investment in further research and
extension is needed to develop and scale context-specific crop-livestock integration practices.