Nutrient flows in smallholder crop-livestock farming systems of the Xiangkhouang province of Lao PDR: Analysis and suggestions for improved nitrogen and phosphorus management

Epper, Carole A.(2017). Nutrient flows in smallholdercrop-livestock farming systems of the Xiangkhouang province of Lao PDR: Analysis and suggestions for improved nitrogen and phosphorus management. (M.Sc. Thesis). ETH Zürich, Zürich, Swiss. 74 p.

Smallholder mixed crop-livestock farming systems are traditional in Lao People’s Democratic Republic (Lao PDR or Laos). For both crop and livestock production sectors a range of diversification and integration to the market can be found. While a range of diversification is already present in all farming systems all over Laos, intensive and market oriented farming practices are slowly expanding from the lowland to the upland areas. Previous observations of the farm management practices in Laos suggested that upland Laotian farmers are traditionally cultivating increasingly infertile soils due to monocropping practices and limited use of external nutrient inputs. These factors suggest that the agricultural soils are suffering further degradation and possibly soil nutrient depletion. Thus, in order to quantify the impact of the changing farming practices on nutrient depletion, nutrient budgets have to be assessed. In this MSc Thesis, eight farms from the upland Xiangkhouang province were selected based on four farm types, defined according to diversity and market orientation. Data was collected through structured interviews, participatory mapping and extensive literature research. Farms nitrogen (N) and phosphorus (P) budgets, balances and flows were analysed for the farm-gate and soil-surface of the total cropped area boundaries using a whole farming system model (FarmDESIGN). The N and P balances of the eight farms were all negative and showed clear N and P mining. This suggests that in the context of the Xiangkhouang province of Laos, diversity and market orientation do not clearly influence the extent of the soil nutrient depletion. The choices of crop and particularly residue management, the incomplete manure recycling and the use of monocropping cultures were most likely negatively influencing the nutrient balances. The implementation of possible management improvements showed that the complete mulching of all the residues produced on the farm as well as the recycling of the manure produced by the bull for fattening resulted in the increase of both N and P balances. The integration of grain legumes and green manure in rotation or intercrop had a clear positive impact on N balances through N2 fixation. The P balances only slightly improved through the intercropping practice, which caused less P exports from the farm-gate and soil-surface of the total cropped area boundaries. The simulations of the possible nutrient management improvements are very promising for N, but further options to improve the P balances should be carefully examined. The options to improve nutrient management should be implemented in the field in order to assess the feasibility of the improvements in that particular environment.