Enhancing agroecosystem sustainability: Integrative soil health strategies in regenerative organic soybean production on Andosol in Japan

Regenerative agriculture prioritizes soil health to enhance ecosystems and crop production. No-tillage organic farming with cover crop rotation improves sustainability. However, economic barriers must be considered. This study evaluated the involvement of biochar into long-term no-tillage combined with cover crop as a regenerative organic approach on soil health and carbon sequestration as well as to assess the economic viability of this farming system. The field experiment was designed as a randomized complete block with a split–split plot arrangement consisting of different tillage practices (no-tillage, rotary cultivator, and moldboard plowing), cover crop (rye, hairy vetch, and fallow), and biochar applications (with and without biochar), in four replications. The study also included two farming scenarios, soybean and soybean + rice production, for economic analysis. Results showed that incorporating biochar into the continuous no-tillage with cover crop rotation increased soil organic carbon and its stock in the topsoil profile (0–30 cm), improved soil health indicators by reducing soil bulk density and penetration resistance, and increased microbial activity, thereby promoting nutrient cycling. Soybean yield varied under the no-tillage system, resulting in a low benefit–cost ratio; however, the integration of soybean with rice production improved this ratio in organic farming–based no-tillage management. Compared with moldboard plowing, no-tillage with rye resulted in the lowest cost of soil organic carbon production. Given these findings, integrating biochar into long-term no-tillage management centered on regenerative organic farming would improve environmental quality and provide economic advantages, strengthening the resilience of natural system, specifically in Andosol, Japan.