Compost tea influence on lettuce (Lactuca sativa L.) root architecture

The presence of plant nutrients, phytohormones and other bioactive compounds in compost tea may singly or in combination influence root architecture. Repeated trials were conducted under greenhouse conditions subjecting lettuce plants to four increasing concentrations of a thermophilic-based aerated compost tea; 0, 5, 10 and 20% m/v, applied at either 100 or 200 cm³ plant^‑1 day^‑1 for 30 days. At the end of both trials measurements were made of yield, shoot and root dry matter, root-to-shoot ratio, root architectural traits and plant nutrient contents. The dependence of yield and plant nutrient content on root architecture was also examined. Increasing compost tea concentration up to a 10% m/v significantly (p<0.05) increased yield above the control for the higher application volume. Further increasing to 20% m/v reduced yield. Increasing concentration of compost tea showed a directly proportional relationship to root and shoot N. However, the effect was non-significant for P. Applying 200 cm³ of 5% m/v compost tea produced lettuce plants with greater root width, depth, volume, and surface area compared to all other treatments. Network surface area and depth was shown to explain some of the variability in yield and root N content respectively. Under similar conditions compost tea can improve the productivity and quality of horticultural plants.