Biochar addition is an effective measure to enhance agricultural productivity and improve soil fertility. However, the response of agricultural productivity to biochar addition varies greatly depending on the production background. In this study, meta-analysis and machine learning methods were used to systematically analyze the effects of biochar addition on maize yield and partial factor productivity of nitrogen (PFPN) in China. The results showed that: 1) Maize yield and PFPN with biochar addition could be significantly increased by 10.49 %-15.02 % and 13.32 %-18.26 %, respectively. 2) In terms of region, year and field management, biochar addition demonstrated more significant yield-enhancing effects in South China under the following conditions: average annual precipitation ≥ 800 mm, average annual temperature ≥ 16℃, biochar application duration of 2 years, biochar application amount of 25–35 kg·ha −1 and planting density ≥ 90,000 plants·ha −1 . The PFPN-improving effects were most pronounced in Northwest China under the following conditions: average annual precipitation＜200 mm, average annual temperature 8–12℃, biochar application duration of 1 year, biochar application amount of ≥ 35 kg·ha −1 and planting density ≥ 90,000 plants·ha −1 . 3) In the soil environment, the growth rates of yield and PFPN varied with different environmental factors (e.g., soil type, texture and physical properties), and the growth rates remained within the ranges of 4.07 %-56.55 % and 5.17 %-45.64 %, respectively. 4) Analysis using Random Forest, Gradient Boosting Machine, and multi-factor optimization models revealed that maize yield was primarily regulated by the synergistic effects of annual average temperature, experimental year, biochar application amount, and soil total nitrogen content. Meanwhile, PFPN exhibited more sensitive responses to experimental duration, biochar application amount, soil texture, soil pH, and soil total nitrogen content. In conclusion, this study systematically clarified the mechanism by which biochar enhances maize productivity, providing scientific basis and technical support for high-yield and efficient maize cultivation in China and other similar ecological regions. • Biochar significantly increases maize yield (10.49 %-15.02 %) and nitrogen use efficiency (13.32 %-18.26 %) in China. • Clarifies the regional heterogeneity in productivity gains and efficiency improvements between southern and northwestern China. • Identifies 35 kg·ha⁻¹ as the optimal biochar application rate for simultaneously enhancing yield and nitrogen use efficiency. • Demonstrates that climatic conditions, biochar application rate, and soil properties as key drivers of biochar effects.
Tian et al. (Fri,) studied this question.