Piper nigrum–Areca catechu intercropping mitigates soil problems related to continuous P. nigrum cropping, but the exact reason for this is not clear. In this study, the intercropping system increased P. nigrum’s single plant weight by 27.0–55.5% and unit yield per hectare by 5.1–33.5% in 2019–2022. Intercropping altered the metabolic profiles of root exudates from both species, with increases in flavonoids (epicatechin and 4′,5,6,7-Tetramethoxyflavone), alkaloids (litebamine), and amino acids (proline betaine, L-homocysteic acid and L-homocysteic acid). Intercropping further increased the abundance of dominant soil bacteria, including GAL15 (354.9%) and Bacteroidota (70.4%) in the P. nigrum rhizosphere, and Firmicutes (141.8%) and WPS2 (75.3%) in the A. catechu rhizosphere. In the intercropping system, the abundance of soil flavonoids, including tangeritin, trifolirhizin, and hexamethylquercetagetin, which participated in improving nutrient absorption and plant growth, increased by 106.4~356.0%, 28.9~45.5%, and 45.2~127.1%, respectively, during the whole growing period. Overall, intercropping with A. catechu promoted carbon input to the P. nigrum soil via root exudates. This increased the diversity of P. nigrum rhizosphere beneficial bacterial communities, as well as the amounts of nutrients and plant growth-promoting secondary metabolites. Together, these effects improved nutrient uptake and utilization, thereby driving the sustainable production of P. nigrum, and ultimately achieving higher yields.

Black pepper plants maintain synchronous vegetative growth and flowering during their lifetimes, even in the juvenile phase. How to limit the duration of flowering, facilitate a return to vegetative development should be studied. Light intensity has been reported to affect the levels of stored carbohydrates in some horticultural trees. However, it is unclear whether increased flowering intensity in adaptable light intensity is due to the regulation of carbohydrates in black pepper. Here, we report the characterization of carbohydrates and enzyme turnover in major source leaves under shading treatments during the juvenile phase of pepper. In addition to the previous finding that carbohydrate levels are correlated with flowering time, we report the novel finding that carbohydrate contents in the leaves control floral quantity. To gain insights into the underlying physiological mechanisms, we analyzed the effect of shading on sugar contents and floral transition, which revealed that shading regulated carbohydrate levels, an increase in starch accumulation improved floral quantity, and sucrose-starch ratio played a negative role in inflorescence quantity. Based on this analysis, we characterized the changes in enzyme activities in the leaves that affect carbohydrate dynamics and identified the key indicator enzymes and optimal shading intensity for the five developmental periods. Highlight: We identified the key carbohydrates, indicator enzymes and optimal shading intensity to control inflorescence quantity during the juvenile phase in black pepper for labor-saving.