Changes in rhizosphere properties of trifoliate orange in response to mycorrhization and sod culture

Sod culture with white clover is a common practice as part of soil management in citrus orchards. However, it is not clear whether such sod culture affects plant growth, soil properties, and the mycorrhizosphere of citrus. In this study, white clover was planted around trifoliate orange (a popular citrus rootstock) under mycorrhization with or without Rhizoglomus intraradices. After four months, the sod culture substantially stimulated root mycorrhizal colonization and soil hyphal growth. Plant growth performance of trifoliate orange was significantly increased by either mycorrhization under non-sod culture or sod culture under non-mycorrhization, whereas sod culture under mycorrhization significantly decreased the growth performance. Both mycorrhization and sod culture significantly increased the concentrations of easily extractable glomalin-related soil proteins (EE-GRSP), total GRSP (T-GRSP), and soil organic carbon (SOC), the distribution of water-stable aggregates in the size of 2-4, 1-2, and 0.5-1 mm, and the activity of soil peroxidase and phosphatase. The mean weight diameter was notably increased by mycorrhization, irrespective of sod or non-sod culture, but was higher with sod culture under mycorrhization than under non-mycorrhization. Root colonization, soil hyphal length, SOC, EE-GRSP, and T-GRSP were significantly and positively correlated with aggregate stability. These results suggested that sod culture stimulated mycorrhizal development and potentially improved soil properties in an AMF-inoculated citrus orchard.