Profitable and sustainable agricultural production in resource-limited crop-livestock farming systems is largely dependent on the efficiency with which essential nutrients (N, P, K, Mg and S) are conserved and recycled. Although the economic and environmental importance of N cycling in agriculture is evident, the most feasible, profitable and sustainable practices that resource-limited and financially-challenged farmers can employ to increase N conservation and N cycling efficiency remain scarce. Based on the situation in Cambodia, five studies were designed to identify strategies to improve efficiency of N cycling through livestock in smallholder crop-livestock farming systems.