Cover Crops Control Weed and Improve Soil Qualities in Citrus Orchard

Cover crop cultivation is a soil management practice to increase orchard sustainability. This study aimed to clarify the effects of eight cover crop treatments on weed control and soil qualities in the citrus orchard. The present study used coverage, soil physical properties, nutrient contents, enzyme activities, and soil bacterial community of eight cover crop species (February orchid, Chinese milk vetch, white clover, common vetch, perennial ryegrass, rattail fescue, white clover + perennial ryegrass, perennial ryegrass + tall fescue + orchardgrass + annual meadow grass) and a control (clean tillage) to characterize the impact of treatment on soil for 1 year. White clover, common vetch, rattail fescue, and the white clover + perennial grass mixture showed the high percentage coverage to control weeds. The rattail fescue treatment allowed significantly increased soil porosity. Fabaceae showed a distinct effect to increased soil organic matter content, which was reduced in soil planted with cereal species. In all cover crop treatments, bacterial and fungal diversity generally increased compared to the control treatment. Redundancy analysis indicated that soil organic matter content and available nitrogen, phosphorus, and potassium contents were the most important environmental factors that influence microbial communities. Among the different cover crop species, white clover, common vetch, rattail fescue, and mixed-species treatment comprising white clover plus perennial ryegrass showed promise for weed control. Compared with the clean tillage applied herbicide, soil qualities in cover crop soil generally showed increasing trends especially soil physical properties and microbial diversity.