This study investigated the synergistic effects of biochar and nitrogen (N) fertilization on soil physical properties and leaf nutrient allocation in Ochroma lagopus Swartz plantations. Seven treatment groups were established: three nitrogen fertilizer levels; three biochar-nitrogen fertilizer combinations; and a control group (CK). The key conclusions as follows: Biochar-N co-application significantly improved soil quality in the short term, mainly reflected in reduced bulk density, increased porosity, mitigation of N-induced soil acidification (pH standardized at 6.8–7.2), and increased soil total N and P contents. At the leaf level, co-application significantly enhanced chlorophyll synthesis and NSCs accumulation, improved N use efficiency (higher leaf N content and lower C/N ratio in optimal treatments), and modulated carbohydrate partitioning (reduced soluble sugar/starch ratio, favouring long-term C storage). RDA showed soil P and pH were key regulators of leaf C: N:P stoichiometry: biochar elevated soil pH to improve P availability. Within the 150-day observation period, BN2 was identified as the most effective regime for maximizing O. lagopus growth (plant height and diameter at breast height) while maintaining soil C: N ratios conducive to nutrient cycling, thus achieving a balance between plantation productivity and soil sustainability during the seedling establishment stage.
Liu et al. (Thu,) studied this question.