Biochar is a potential source for improving soil fertility and crop yield by enhancing phosphorus (P) availability. But the information on quantitative effect of biochar addition on soil P availability is still limited. To address this query, we conducted a meta-analysis with 507 data from 95 eligible literature. The results showed that irrespective of biochar characters (raw material, C:N ratio, pyrolysis temperature, application rate), soil characteristics (texture, pH, organic carbon content), and fertilizer application, biochar addition significantly improved soil available P content by 57.6%. Meanwhile, biochar addition promoted P utilization of crops. The response ratios of plant P concentration to biochar addition were generally lower than those of soil available P. The average response ratio of plant P concentration was 30.6%. The biochars, derived from livestock manure, low-temperature pyrolysis, with lower C:N ratio, alkaline, or higher application rate, were more effective to improve soil available P content and plant P concentration in sandy and loamy soils. For main enzymes involved in P cycle, biochar addition increased activity of alkaline phosphatase (2.8%) but decreased the acid phosphatase activity (17.8%). Overall, biochar addition positively affects soil available and plant P concentration, but has a minute effect on soil phosphatase. The improvement of soil P availability might mainly be ascribed to a great amount of active P fractions in biochar itself.
生物炭改善土壤肥力和提高作物产量的作用与土壤磷素有效性的提高密切相关,但是关于生物炭添加对土壤磷素有效性影响的定量效应尚不明确。本研究对95篇符合条件的文献中的507组数据进行整合分析,以评估生物炭添加对土壤磷素有效性的定量影响。结果表明: 不论生物炭原料、制备温度、C/N、施用量、配施化肥与否,以及土壤质地、pH、有机碳含量如何变化,生物炭添加均使土壤有效磷含量显著提高,平均较不添加对照提高57.6%。同时,生物炭添加促进了作物对磷的利用,但植株含磷量对不同添加条件下生物炭的响应程度基本上均低于土壤有效磷,部分条件下未达到显著水平,平均响应比为30.6%。在砂质和壤质土壤中,添加拥有较多灰分的畜禽粪便生物炭,以及较低C/N、低温裂解的碱性生物炭、较大施用量对增加土壤有效磷和植株磷含量更有效。作为土壤磷素循环的主要酶,生物炭添加使碱性磷酸酶活性平均增加2.8%,而酸性磷酸酶活性则平均降低17.8%。总体上,生物炭对土壤有效磷和植株磷含量有显著的正向效应,但对土壤磷酸酶活性的影响较小,磷素有效性的提高可能主要源于生物炭自身携带较高含量的有效磷组分。.
Keywords: biochar; meta analysis; plant phosphorus concentration; soil available phosphorus; soil phosphatase.