National-scale Scenario Analysis of Nutrient Management Strategies for Soil and Water Conservation in Korea

Nitrogen (N) and phosphorus (P) are essential nutrients for crop production; however, excessive nutrient inputs beyond crop demand remain a major driver of nutrient losses to soil–water systems, resulting in eutrophication, greenhouse gas emissions, and declining nutrient use efficiency. Nutrient balance, defined as the difference between nutrient inputs from fertilizers and livestock manure and nutrient outputs via crop uptake, provides an integrative indicator for assessing nutrient surpluses and associated environmental risks in agricultural land.

In Korea, national nutrient balances remain among the highest in OECD countries, reaching 240 kg N ha⁻¹ and 44 kg P ha⁻¹ in 2022, largely due to livestock-related nutrient inputs. To explore effective strategies for reducing nutrient surpluses and improving soil and water conservation, this study evaluated three national-scale nutrient management scenarios: (i) optimized fertilizer application based on soil testing, (ii) reduction in livestock numbers, and (iii) improvement of livestock manure treatment rates. Scenario analysis showed that nutrient balances could be reduced by up to 20%, 25%, and 50% under scenarios (i), (ii), and (iii), respectively, indicating that enhanced manure treatment is the most effective leverage for mitigating nutrient overloads at the national scale.

These findings highlight the importance of integrated nutrient management approaches that combine precision fertilizer use with improvements in livestock manure management. Furthermore, the results suggest that improving manure treatment efficiency, together with circular nutrient use and manure-to-energy conversion, can contribute to reducing nutrient losses to water bodies while supporting long-term sustainability and climate mitigation goals. This study provides a policy-relevant framework for advancing nutrient management strategies aimed at soil and water conservation in intensive agricultural systems.