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

Nutrient flows and intensification options for smallholder farmers of the Lao uplands

South East Asia's agricultural landscape is rapidly transitioning from subsistence to intensive and market-oriented production, often with negative impacts on soil fertility. Ensuring that this transition is conducted in a sustainable way is critical, especially for the poorest who rely exclusively on natural resources that are of limited quality and quantity. This study aims to evaluate sustainable intensification options for smallholder ethnic minority farmers of the Lao uplands. Following a systematic selection of case study crop-livestock farms with different degrees of diversification and market orientation, we adopted a detailed nutrient flow approach to quantify nitrogen (N) and phosphorus (P) balances at farm level using a whole farm modelling tool. This was then used to simulate alternative sustainable intensification options relative to the baseline and their impact on farm performance and N and P cycling. Irrespective of the intensification level, nutrient balances were negative on all farms, with net nutrient removal between −34 and −130 kg N ha−1y−1 and between −9 and −20 kg P ha−1y−1. The positive effect of the sustainable intensification options on selected system performance variables was up to 15 times higher when its baseline value was low, i.e. when potential for improvement was high. Compared to the baseline (rice and maize monocropping systems), fallow plots during the dry season and low level of residues recycling, all intensification options increased land productivity and N balance by at least 12% on each farm, whereas the P balances were negatively impacted. The positive effects on the N balances might not be sufficient to reverse nutrient depletion, and additional nutrient inputs would be necessary. Four management principles are key to ensure a smooth transition from subsistence to intensive production: no residue burning, stay diverse, integrate livestock and use small amounts of P mineral fertilizer. If combined with efficient and integrative agricultural extension, seed systems and market development, these basic principles could be the key success factor for a sustainable development of the Lao uplands.</p