Effect of Soil Solarisation on Fusarium Wilt Suppression, Soil Microbial Dynamics, Growth, and Yield of Cucumber (Cucumis sativus L.)

Abstract

Fusarium wilt, caused by Fusarium oxysporum f. sp. cucumerinum, is a major soil-borne disease that significantly constrains cucumber (Cucumis sativus L.) production worldwide. Soil solarisation has been proposed as an environmentally friendly alternative to chemical disease control. This study evaluated the effectiveness of soil solarisation in suppressing Fusarium wilt and enhancing the growth and yield of cucumber under field conditions. The experiment was conducted over nine weeks at Matogun Airport Signal Farmland, Oke-Aro, Ogun State, Nigeria. Two treatments, namely solarised soil and non-solarised soil (control), were arranged in a Completely Randomised Design (CRD) with three replicates. Soil samples were collected before solarisation and at two-week intervals after treatment to determine changes in fungal and bacterial populations, while cucumber growth, yield, and disease incidence were assessed throughout the experimental period. Fungal isolates identified included Trichoderma, Aspergillus, Penicillium, Rhizoctonia, Fusarium, Pythium, and Rhizopus species, whereas bacterial isolates comprised Bacillus, Pseudomonas, Enterobacter, Klebsiella, Azotobacter, and Actinomycetes. Fungal colony counts declined markedly following solarisation, from 5.40–9.63 × 10² cfu mL⁻¹ before treatment to 1.50–2.23 × 10² cfu mL⁻¹ after six weeks. In contrast, bacterial populations increased from 2.80–4.27 × 10² cfu mL⁻¹ to 8.57–14.13 × 10² cfu mL⁻¹. Cucumber plants grown in solarised soils exhibited improved vegetative growth and higher fruit yields, producing 22.67–23.33 fruits per plant compared with 12.67–14.33 fruits per plant in non-solarised soils. Fusarium wilt incidence (40.00–42.33%) occurred only in non-solarised plots. The study demonstrates that soil solarisation effectively suppresses soil-borne fungal pathogens, enhances beneficial bacterial populations, reduces Fusarium wilt incidence, and improves cucumber productivity. Soil solarisation is therefore recommended as a sustainable disease management strategy for cucumber cultivation.