Linear programming-based optimization of the productivity and sustainability of crop-livestock-compost manure integrated farming systems in midlands of Vietnam

Farmers' livelihood in the midlands of the northern part of Vietnam relies mainly on crop production and livestock rearing. Green manure and animal dung are commonly used for crops, particularly in rice culture - a staple food crop, and sugarcane - a cash crop. Due to the small-scale livestock systems, the animal dung is limited, which results farmers in preferring a smaller sugarcane cultivation area. This research study was to investigate and to optimize the effect of animal and green manures and their combination together with heat-compost technique on the improvement of the quality of organic manure, soil fertility and yield in three farm categories. The study revealed that the farmers in the small, medium and large farm categories should raise livestock up to 4 pigs and 3 buffaloes, 7 pig and 5 buffaloes, and 20 pigs and 13 buffaloes, respectively to match with the available resources. The optimized livestock herd holding and sugarcane cultivation area resulted in 88.7% increase of the return from livestock and 62.5% from crops in the small farm size, 25% from livestock and 9% from crops in the medium farm size and 171% from livestock while unchanged from crops in the large farm size.