Leaf-Derived Allelopathy in Sweetpotato ( Ipomoea batatas ): Chlorogenic Acid Accumulation and Weed Suppression

Abstract

Sweetpotato ( Ipomoea batatas ) is an important food security crop but is highly susceptible to weed interference due to its prostrate growth habit and limited herbicide options. While root-derived allelopathy in sweetpotato has been studied extensively, leaf-derived allelopathy remains poorly understood. This study provides the first formal report of leaf-mediated allelopathy and its role in natural weed suppression. Two cultivars, Heart-O-Gold and 529, were analyzed for chlorogenic acid (CGA) concentrations using HPLC. Results showed that CGA content increased with leaf age, reaching up to 1% of fresh weight, with leaf tissues containing significantly higher levels than roots. Field and greenhouse experiments demonstrated that sweetpotato leaves shed quadratically beginning in the fourth week after planting, contributing an estimated 1.2 - 2.8 t/ha of dry matter across the season. Pot experiments using shed leaves as mulch revealed complete suppression of Palmer amaranth and grasses, with only minimal purple nutsedge emergence at pot edges. These findings indicate that sweetpotato leaf shedding and decomposition release substantial amounts of allelopathic compounds, particularly CGA, creating a natural mulch that extends the weed-free period beyond the critical 2 - 6-week window after transplanting. Leaf-derived allelopathy thus represents a sustainable, above-ground mechanism of weed management, with potential applications in cultivar selection, organic mulch development, and eco-friendly cropping systems.