Work

Synergistic Effects of Earthworm and Straw Application on Soil Enzyme Activities and Nutrient Cycling in Continuous Greenhouse Watermelon Systems

Year: 2026

Type: article

Abstract: Continuous greenhouse watermelon cultivation is widely constrained by declining soil function, impaired nutrient cycling, and increasing soil-borne disease pressure. Developing biologically driven strategies to restore soil–crop coupling is therefore critical for sustainable protected horticulture. Here, we conducted a two-year field experiment (2024–2025) using a randomized block design with three treatments (CK, ST, and STE), three replicates per treatment, and a plot area of 22.5 m2 to evaluate how straw application alone and in combination with earthworms regulate soil processes and crop performance in a continuous greenhouse watermelon system. Compared with CK and ST, earthworm–straw co-application (STE) exerted stronger effects, particularly during the mid-to-late growth stages. In 2024, STE increased soil organic matter by 25.34% and 30.28% relative to CK at the fruiting and harvest stages, respectively; in 2025, the corresponding increases were 25.22% and 27.62%. STE also significantly increased total nitrogen at nearly all growth stages, with the maximum increase reaching 67.23% relative to CK at harvest. In 2025, total phosphorus under STE was significantly higher than under CK and ST across all growth stages, with increases of 75.82% and 79.63%, respectively, at the fruiting stage. Neutral phosphatase activity was markedly enhanced, increasing by 292.24% at the fruiting stage in 2025. These improvements were accompanied by higher plot yield and lower wilt disease incidence, with yield increasing by 34.00% in 2024 and 21.29% in 2025 relative to CK, while disease incidence decreased by 41.46% and 56.06%, respectively. Integrative Mantel tests showed that total nitrogen was the factor most strongly associated with watermelon yield, with the correlation coefficient increasing from r = 0.490 (p = 0.001) in 2024 to r = 0.662 (p = 0.001) in 2025. Co-occurrence network analysis further revealed a strong positive correlation between yield and total nitrogen (r = 0.848 in 2024; r = 0.673 in 2025) and a negative correlation between disease incidence and total nitrogen (r = −0.661 in 2024; r = −0.822 in 2025), indicating progressively strengthened soil–plant functional coupling over time. Our findings demonstrate that earthworm–straw co-application strengthened soil nutrient transformation capacity and enhanced soil suppressiveness against wilt disease, thereby providing an effective ecology-based strategy for alleviating continuous-cropping constraints in greenhouse watermelon systems.

Source: Horticulturae

DOI: 10.3390/horticulturae12040503