Seaweed Extract Enhances Drought Resistance in Sugarcane Via Modulating Root Configuration and Soil Physicochemical Properties

Seaweed extract is widely used in sustainable agricultural management and can promote sugarcane growth even under low-water availability conditions. However, to date, little information has been gained regarding the role of seaweed extract in regulating sugarcane root configuration and soil physicochemical properties under drought conditions. In this study, the effects of seaweed extract on soil physicochemical properties of sugarcane were studied by soil culture experiments, and the effects of seaweed extract on root architecture of different sugarcane varieties "YT03-393" (drought-sensitive variety) and "cv. ROC22" (drought-resistant variety) were explored by hydroponic experiments. The results revealed that the application of seaweed extract increased the proportion of aggregates > 0.25 mm in the soil and increased the moisture content of the soil under water deficiency conditions. Furthermore, the seaweed extract application increased the activities of urease, sucrase, acid phosphatase, and glucosidase in soil and increased the soil contents of available nutrients such as N, P, and K. Under drought stress, seaweed extract promoted root growth in deeper soil. The proportions of root dry weight and root length density in the soil of 20-40 cm depth increased by 45.0% and 9.8%, and 38.3% and 8.9% in cv. YT03-393 and cv. ROC22, respectively. Additionally, seaweed extract application improved the activities of antioxidant enzymes, including SOD, CAT, and POD, in roots and alleviated the oxidative damage of roots caused by drought stress. It can be concluded that seaweed extract application can improve soil physical structure, promote enzyme activities, and increase the available N, P, and K of the soil. Furthermore, seaweed extract can promote root growth, change root architecture, and improve the water use efficiency of roots, thus improving drought resistance of sugarcane plants.