Effect of vermicompost tea and compost extract as foliar sprays on growth of lettuce

Abstract:

Lettuce growers seeking organic-compliant foliar feeds face a confusing array of liquid biofertilizer options with little comparative field data. This research compared vermicompost tea (VCT) and compost extract (CE) at three concentrations (2%, 5%, 10%) as foliar sprays on butterhead lettuce (cv. All Year Round) grown in an unheated polytunnel at the Devon College of Agricultural Research, Exeter, United Kingdom, during spring and autumn 2023. A randomized complete block design with seven treatments (including a water-sprayed control) and four replications was used. VCT at 10% produced the highest fresh head weight (78.4 g plant⁻¹), leaf number (12.6), and chlorophyll content (41.3 SPAD), representing 61.0%, 51.8%, and 44.4% increases over the control, respectively. CE at 10% performed comparably to VCT at 5% for most parameters. A clear dose-response was observed for both products. VCT consistently outperformed CE at equivalent concentrations. These results suggest that VCT at 10% is the most effective organic foliar feed for lettuce among the options tested.