Improving the rhizosphere microbiome in Florida citrus groves through mulching and cover crops to foster sustainable horticultural practices

Plant-rhizosphere microbiome interactions are an understudied component of citrus production. This is even more important in Florida flatwood soils, which pose significant challenges in achieving sustainable and effective fruit production due to low natural fertility and organic matter. Citrus growers apply soil amendments, including mulch and cover crops, to ameliorate their soil conditions. Thus, the aim of this research was to evaluate the effects of mulch and cover crops on soil characteristics and rhizosphere composition. The field trials lasted 3 years and plant material consisted of sweet orange, lemon, and grapefruit trees grafted on common rootstocks used in Florida citrus production. The experiment consisted of two treatments, which included trees treated with mulch, cover crops, and a control. The soil and leaf nutrient contents, soil pH, cation exchange capacity, moisture, temperature, and rhizosphere fungal and bacterial compositions were examined over the course of the three years. Citrus trees treated with soil amendments resulted in significantly greater soil moisture and rhizosphere bacterial diversity compared to the control. The better soil conditions detected during the samplings correlated with the significant increases in the diversity of the rhizosphere fungal and bacterial community composition. Similarly, the reduced rates of leaching and evaporation (at the soil surface) of soil amendments applied to Florida sandy soils likely played a large role in the significant increase in moisture and nutrient retention.