Nutrient supplementation increased growth and nitrate concentration of lettuce cultivated hydroponically with biogas slurry.

摘要

Recycling of biogas slurry, a by-product of biogas production, via vegetable production is a multi-benefit and sustainable utilization strategy regarding agriculture and environment. A glasshouse experiment was conducted to investigate the effects of P and Fe supplementation on growth and quality of lettuce cultivated hydroponically with diluted biogas slurry. The results showed that direct supplementation of P into diluted biogas slurry together with Fe improved the lettuce growth significantly, and decreased the root to shoot ratio. However, growth responses of lettuce to single addition of P or Fe into diluted biogas slurry were not significant. In addition, supplementation of P and Fe improved leaf chlorophyll content (determined as SPAD value), nitrate concn. significantly or slightly of the lettuces but not vitamin C content. However, addition of P and Fe or microelements through foliar spray was not effective for enhancing growth and quality except for improving leaf SPAD. In conclusion, as a nutrient solution, the tested biogas slurry needs Fe and P supplementation, and P should be added together with Fe or post Fe supplementation in terms of lettuce yield. Also, direct addition of Fe into diluted biogas slurry was better than foliar spray.