Objectives his study investigated the effect of soil texture on sweet potato plant architecture formation and quantified the relationships between plant growth indices and storage root yield, providing theoretical support for high-yield sweet potato cultivation.

Methods Two sweet potato cultivars, ‘Shangshu 19’ and ‘Yanshu 25’, were selected as test materials, and three soil texture treatments were established: sandy loam, loam, and clay loam. At the early, middle, and late tuber bulking stages (70−80, 100−110, and 130−140 days after transplanting), photosynthetic parameters were determined, sucrose and starch concentrations in leaves, petioles, and stems were quantified, and morphological traits of leaves and stems—including main stem length, internode length, petiole length, branch number, and basal stem diameter—were measured. The growth rate of each organ and the partitioning rate of photosynthates were calculated, and the relationships between morphological indices and storage root yield were analyzed.

Results Compared with loam soil, the sandy loam treatment exhibited the highest dry matter partitioning rate to storage roots and the largest single storage root weight, with storage root yield increasing by 7.14%−10.61%; in contrast, the clay loam treatment resulted in the lowest values for these indices, with yield decreasing by 7.26%−10.54%. Soil texture did not significantly influence the number of storage roots per plant. During the storage root bulking stage (70−140 days after transplanting), plants in the sandy loam treatment exhibited the shortest main stem length, internode length, and petiole length, as well as the smallest basal stem diameter, along with the lowest elongation rates, while the clay loam treatment promoted higher growth rates of these organs, leading to significantly greater values compared with those in the sandy loam treatment. Compared with the loam treatment, sucrose contents in leaves, petioles, and stem tops were significantly higher in the sandy loam treatment, while sucrose content in stem bases and starch content in all above-ground organs were significantly lower. In storage roots, both sucrose and starch contents increased markedly under sandy loam. In contrast, clay loam significantly reduced sucrose content in above-ground organs (except for stem bases) and increased starch content in all aerial parts, while root carbohydrate accumulation decreased. Sandy loam also increased the leaf sucrose-to-starch ratio and sucrose phosphate synthase activity in functional leaves, indicating enhanced sucrose export from leaves. The clay loam treatment showed the opposite trend. At the mid-root bulking stage, sandy loam promoted higher net photosynthetic rates and prolonged leaf functional duration. Although clay loam resulted in a higher leaf area index, it was accompanied by a shorter leaf functional period and lower photosynthetic rates. Path analysis revealed that, at the mid-bulking stage, main stem length, internode length, petiole length, and basal stem diameter were all negatively (P<0.05) correlated with yield. By integrating direct and total effects, main stem length was selected to establish a regression model. The model indicated that, under the experimental conditions, when the main stem length did not exceed 166.6 cm for Shangshu 19 and 186.0 cm for Yanshu 25 at 100 days after transplanting, there was a high probability of achieving storage root yields of 50 t/hm² and 60 t/hm² or higher, respectively.

Conclusions Sandy loam cultivation enhances sweet potato photosynthetic performance, characterized by greater photosynthetic export capacity from leaves and efficient photoassimilate translocation within vines. This promotes root bulking while suppressing excessive above-ground growth. Notably, shorter main stem length contributes to forming an ideal plant architecture—marked by robust vine growth, high photosynthetic efficiency, and efficient assimilate transport—thereby facilitating high yields. Conversely, the clay loam treatment induces excessive vegetative growth, causing significant photoassimilate retention in above-ground organs. This leads to insufficient carbohydrate accumulation in storage roots, ultimately reducing yield.