Cover crops are crucial in conservation agriculture for preventing soil erosion. For Citrus unshiu production, rattail fescue (Vulpia myuros (L.) C.C. Gmel) is a popular cover crop because its growth season differs from the citrus season, minimizing nutrient competition. However, no studies have examined its effects on the seasonal concentrations of flavonoids and monoterpenes in citrus peels, which are often used as medical ingredients. In this study, our aim is to determine the effects of cover crops on the sugar content and medicinal properties of unripe citrus fruit during the growing season. Samples collected in 2022 were examined for the effects of cover crops on the sugar concentration of fresh pulp. In addition, samples were taken from three randomly selected trees in each cover crop treatment (0, 50, and 100% area coverage) at the thinning (July, August, and September) of 2023 and 2024 to analyze hesperidin and d-limonene concentrations using standard methods. The results showed that cover crops reduced the sugar concentration of fresh pulp but had no impact on hesperidin concentrations across all thinning events and had inconsistent effects on the d-limonene concentration. Hence, while the use of rattail fescue might negatively affect the sugar concentration of mature Citrus unshiu, the use of premature fruits for medical ingredients could compensate for this loss.
絢 et al. (Thu,) studied this question.