Long-term biochar addition improves post-rice wheat production by ameliorating soil mechanical impedance and moisture condition as well as promoting root growth

Biochar has been widely applied as an efficiency soil additive to modify the quality of cultivated field. However, the effects of long-term biochar addition on spatial and temporal dynamics of soil compaction, and the changes in soil moisture condition and plant root growth remain unclear. Hence, an eight-year (2015/16–2023/24) consecutive field experiment on wheat was conducted in the subtropical humid region of east China, using three treatments: no N fertilizer (PK), chemical fertilizer (NPK), NPK plus biochar (5 t ha −1 yr −1 , NPKB). Relative to NPK, across nine growing seasons of wheat, NPKB decreased the soil bulk density by 0.019 and 0.013 units (g cm −3 yr −1 ), and decreased the soil penetration resistance by 0.028 and 0.015 units (MPa yr −1 ) in 0–10 cm and 10–20 cm depths, respectively. Biochar addition improved soil water content from seeding to flowering, increased wheat root distribution during the whole growth period, and enhanced soil N supply capacity by promoting N adsorption, which gave rise to greater biomass and N accumulation and more biomass allocation in grain. As a result, NPKB increased wheat yield by 14.8 %, N recovery efficiency by 55.1 %, and crop water productivity by 14.9 %, relative to NPK, on average across four growing seasons of wheat. Therefore, long-term biochar addition has potential to substantially increase grain yield of post-rice wheat, water productivity, and N recovery efficiency. Hence, for the sustainable intensification cropping in the long-run, successive biochar addition could be a finable management for wheat production on the rainfed Yangtze River Region of China. • 8-year biochar addition (5 t ha −1 yr −1 ) in a post-rice wheat field was studied. • Biochar decreased 0–20 cm soil bulk density by 0.018 g cm −3 yr −1 . • Biochar decreased 0–20 cm soil penetration resistance by 0.029 Mpa yr −1 . • The averaged root mass density was 31.4 % higher with biochar in 0–40 cm soil. • The averaged crop water productivity was 14.9 % higher with biochar.