In-depth insight into the short-term effect of floor management practice on young apple trees development and soil microbial biodiversity and activity

PLOS One | https://doi.org/10.1371/journal.pone.0329979 August 7, 2025 5 / 15 from the “agricolae” package. In case of not normal distribution, the non-parametric Kruskal-Wallis analysis with Fisher’s least significant difference post hoc test was utilized, introducing the Benjamini-Hochberg correction, with significance set at p ≤ 0.05, using the Kruskal function from the “agricolae” package. PCA was performed using “prcomp” command from the “stats” package and visualized using “ggplot2” and “ggfortify” packages. Heatmaps were generated using “heatmap.2” command from “gplots” package. Results Plant growth response Both tested living mulches mixtures partly negatively affected the main crop growth during the first two growing seasons (Table 1). Indeed, apple trees showed lower trunk diameter growth after the first season particularly when associated with Trifolium repens and Festuca ovina living mulch mixture than control trees. Even though no effect on trunk growth was observed during the second season, the control trees showed significantly higher trunk growth in 2-year perspective than the two mixtures. Both tested living mulch mixtures did not affect the number of 1-year-old shoots during both seasons, but reduced significantly their length over the 2 years, particularly Mix 2 (Table 1). As a consequence, after 2 vegeta- tive seasons control trees developed a significantly higher total length of 1-year shoots (644.9 cm), compared to Mix1 (505.9 cm) and Mix2 (422.5 cm). The flowering intensity and yield potential were also affected by the living mulch mix-

tures (Table 1). The number of flowers per tree resulted was about 60% and 75% of the value observed for control trees, respectively for Mix 1 and Mix 2, which was reflected in a similar lower rate of fruitlets. Table 1. Apple tree growth and potential yield as affected by two living mulch mixtures. Season Control Mix1 Mix2 Trunk diameter growth (mm) 2021 2.6 ± 3.4 a 0.5 ± 1.6 b 1.3 ± 1.9 ab 2022 3.8 ± 3.4 a 3.6 ± 1.5 a 3.2 ± 2.6 a Cumulative 6.4 ± 1.7 a 4.1 ± 1.3 b 4.5 ± 1.7 b One-Year Shoot Number 2021 10.9 ± 2.2 a 10.3 ± 2.4 a 9.8 ± 2.1 a 2022 29.7 ± 5 a 28.1 ± 4.8 a 25.9 ± 6.8 a Cumulative 40.6 ± 5.4 a 38.3 ± 5.4 a 35.7 ± 6.1 a Average Length of One-Year Shoot (cm) 2021 12.6 ± 3.0 a 10.4 ± 3.1 a 11.8 ± 2.7 a 2022 17.1 ± 3.1 a 14.0 ± 3.4 ab 11.0 ± 4.2 b Cumulative 15.8 ± 2.7 a 12.9 ± 2.9 b 11.5 ± 3.1 b Total Length of One-Year Shoot (cm) 2021 135.9 ± 31.3 a 104.0 ± 31.9 a 115.2 ± 39.8 a 2022 509.0 ± 143.7 a 401.9 ± 152.4 b 307.3 ± 188.7 c Cumulative 644.9 ± 158.9 a 505.9 ± 171.9 b 422.5 ± 177.0 b Flowering intensity (flowers number) 2022 194.1 ± 55.9 a 114.3 ± 63.8 b 143.9 ± 35.4 ab Fruiting potential (fruitlets number) 2022 28.7 ± 7.3 a 21.1 ± 11.3 ab 19.9 ± 7.8 b Mean±SD, n = 15. Letters show statistically significant differences for the comparison of data in the row for p ≤ 0.05. https://doi.org/10.1371/journal.pone.0329979.t001