Wang, X., Su, X., Wang, L. et al. Effect of a six-year BiocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More Amendment on Water Productivity and Nitrogen Utilization of Maize and Comprehensive Soil Fertility. J Soil Sci Plant Nutr (2024). https://doi.org/10.1007/s42729-024-01932-5

Biochar is known for its ability to retain water and nutrients, which enhances water productivity and nitrogen (N) use efficiency, leading to increased crop yields. However, over time, biochar’s effectiveness in regulating water and N may diminish, altering its impact on crop yields. A two-year field experiment was conducted to assess these time-dependent effects, using a split-plot design. The main plots represented different periods of biochar addition: one year (Y1), two years (Y2), five years (Y5), and six years (Y6). Subplots included three biochar addition rates: no biochar (C0), 6 t·hm−2 biochar (C6), and 12 t·hm−2 biochar (C12).

Results indicated that short-term biochar addition significantly outperformed medium- to long-term addition in boosting maize yield, water productivity, N-use efficiency, and the soil fertility index (SFI). Notably, there was no significant difference between the Y6C6 treatment and the control group with no biochar addition, though higher biochar rates could mitigate this decline. Structural Equation Model (SEM) analysis revealed a positive correlation between increased soil NH4+-N and NO3−-N content and SFI. Additionally, nitrate nitrogen (NO3−-N) content positively influenced water productivity. However, as biochar addition periods extended, the effect of NO3−-N on SFI and water productivity weakened, while the impact of ammonium nitrogen (NH4+-N) on SFI intensified, affecting yield.

The C12 treatment emerged as the most effective, not only improving yield, water productivity, and N-use efficiency but also reducing the decline of beneficial effects on crops and soil over medium- and long-term biochar application.