Nutrient Cycling Efficiency in Mixed Crop-Livestock Systems: Mechanisms, Environmental Benefits and Future Directions

The world needs more food, yet the environment is getting worse, nutrients are being lost and resources are becoming scarcer.It has raised the interest in sustainable agriculture systems with circular resource utilization.The integration of crop production with livestock husbandry in mix crop-livestock systems (MCLS) is a potential approach to improve the efficiency of nutrient cycling.This study presents the current knowledge on the mechanics, environmental benefits, issues and potential improvements of nitrogen cycling in MCLS.The soilplant-animal-manure nexus enables the recycling of nitrogen (N), phosphorus (P) and carbon (C), thus enhancing nutrient use efficiency and decreasing the dependence on synthetic fertilizers.Evidence suggests integrated systems can improve nitrogen use efficiency by 50-70% and soil organic carbon stocks by 10-30%, while reducing nitrate leaching by 20-40%, and reducing greenhouse gas emissions through better manure management and carbon sequestration strategies.Greater recycling of nutrients also results in greater soil structure, water retention, microbial biodiversity and ecosystem resilience.However, the benefits are restricted by the complexity of labor and management, spatial isolation of crop and animal enterprises, nutrient imbalances due to manure N:P ratios and the requirement for major infrastructural investment.New technologies include precision nutrient management, real-time detection of manure and variable rate application of organic fertilizers, anaerobic digestion, biochar integration and nutrient recovery systems.This is a great opportunity to boost nutrient retention and efficiency of resource consumption.Regional networks for nutrient exchange and policy instruments such as carbon credits and payments for ecosystem services could promote wider adoption.Collectively, MCLS provide a good foundation to further promote circular agriculture, thus enhancing environmental sustainability and reinforcing long-term food security under increasing climate and resource constraints.