Most studies found the benefit of biochar in increasing plant photosynthetic rate (PR), but how experimental conditions affect PR response to biochar application remains unclear. Therefore, we performed a meta-analysis by including 965 pairwise comparisons from 135 studies. Generally, biochar application enhanced PR by 23 % on average, a statistically significant increase relative to the control. However, a large variation of percent change in PR ranging from −59 to +1267 % was also observed under different experimental conditions. Specifically, biochar properties including contents of potassium (K), phosphorus (P), sodium (Na), carbon (C) and ash and their determining factors (feedstock and pyrolysis temperature) significantly influenced PR responses to biochar addition, while biochar pH could not be used alone as an effective predictor of PR increases after biochar treatment. There was a potential match between soil pH and biochar pH, determining the performance of biochar in improving crop PR. However, the complementarity between soil pH and biochar pH was not sufficient to achieve the maximum increase in PR, appropriate biochar application rate was needed at the same time. The most suitable application rate of biochar was 10.1−20 t ha⁻¹ or 2.01–4 %. Moreover, it is essential to take the compatibility and complementarity between biochar, soil texture and management factors such as Nitrogen (N) application rate and growing environment into consideration. Overall, adding biochar into coarse textured soils or heavy metal contaminated soils is highly recommended for increasing plant PR. Co-application of biochar with nitrogen fertilizer is also worth being advocated. When the N application rate was 101−200 kg ha⁻¹ or ≤ 0.015 %, the maximum increase in PR was obtained. These findings can provide suggestions for biochar application in agricultural production to optimize PR benefits.

大多数研究发现生物炭在提高植物光合速率 (PR) 方面的好处，但实验条件如何影响 PR 对生物炭应用的响应尚不清楚。因此，我们通过纳入来自 135 项研究的 965 项成对比较进行了荟萃分析。一般来说，生物炭应用平均提高了 23% 的 PR，相对于对照而言，这是一个统计上显着的增加。然而，在不同的实验条件下也观察到 PR 的百分比变化范围从 -59% 到 +1267% 的很大变化。具体而言，包括钾 (K)、磷 (P)、钠 (Na)、碳 (C) 和灰分含量在内的生物炭特性及其决定因素（原料和热解温度）显着影响了 PR 对生物炭添加的响应，而 biochar pH 值不能单独用作 biochar 处理后 PR 增加的有效预测指标。土壤 pH 值和生物炭 pH 值之间存在潜在匹配，决定了生物炭在提高作物 PR 方面的性能。然而，土壤pH值与生物炭pH值之间的互补性不足以实现PR的最大增加，同时需要适当的生物炭施用量。生物炭最适宜的施用量为10.1-20 t ha⁻¹或 2.01–4 %。此外，必须考虑生物炭、土壤质地和氮（N）施用率和生长环境等管理因素之间的相容性和互补性。总体而言，强烈建议将生物炭添加到粗糙质地的土壤或重金属污染的土壤中以提高植物 PR。生物炭与氮肥共施也值得提倡。当施氮量为 101-200 kg ha ^-1或≤ 0.015 % 时，获得最大的 PR 增加。这些发现可以为生物炭在农业生产中的应用提供建议，以优化公关效益。