As root exudation may be altered by drought stress, we investigated if biochar amendment could moderate these effects. In a pot experiment with maize, treatments amended with straw or wood biochar were exposed to different irrigation regimes: well-watered (irrigated to 90% of water holding capacity (WHC)), drought (no irrigation for 4 days), and recovery (irrigated to 90% of WHC for 4 days after drought). Photosynthesis was measured during plant growth. At harvest, the leaf water potential (LWP), plant biomass, rhizosphere and bulk soil NH₄⁺ content, pH, multiple substrate-induced respiration (MSIR), and rhizosphere content of selected primary metabolites (as an indication of root exudation) were determined. While the plant biomass was unaffected by biochar amendment, biochar had positive effects on the LWP and photosynthetic parameters in the initial drought and recovery phases. Furthermore, soil pH and NH₄⁺ content were affected by biochar and the C-substrate utilization (MSIR) increased in the biochar treatments, independently of irrigation. Both biochars significantly altered the rhizosphere content of primary metabolites, especially under full irrigation and drought, and it is suggested that direct and indirect effects of biochar application on soil properties are the cause of these changes. Biochar specifically increased the content of organic acids, and drought even had an additive effect on the content of succinic acid in the wood biochar treatment.

由于干旱胁迫可能会改变根系分泌物，我们研究了生物炭改良是否可以减轻这些影响。在玉米盆栽试验中，用秸秆或木材生物炭修正的处理暴露于不同的灌溉制度：充分浇水（灌溉到 90% 的持水量 (WHC)）、干旱（4 天不灌溉）和恢复（干旱后 4 天以 90% 的 WHC 灌溉）。在植物生长期间测量光合作用。收获时，叶片水势 (LWP)、植物生物量、根际和大块土壤 NH ₄ ⁺测定了选定初级代谢物的含量、pH、多底物诱导呼吸 (MSIR) 和根际含量（作为根系分泌物的指示）。虽然植物生物量不受生物炭修正的影响，但生物炭对干旱初期和恢复阶段的 LWP 和光合参数有积极影响。此外，土壤 pH 值和 NH ₄ ⁺含量受到生物炭的影响，并且在生物炭处理中碳底物利用率（MSIR）增加，与灌溉无关。两种生物炭都显着改变了初级代谢物的根际含量，特别是在充分灌溉和干旱的情况下，这表明生物炭应用对土壤性质的直接和间接影响是这些变化的原因。生物炭特别增加了有机酸的含量，干旱甚至对木材生物炭处理中的琥珀酸含量产生了累加效应。