Application of Directly Brewed Compost Extract Improves Yield and Quality in Baby Leaf Lettuce Grown Hydroponically

Abstract

The aim of this work was to study whether the application of a directly brewed compost extract (added in the nutrient solution or by microsprinkler) could be used to improve the yield and quality of baby leaf red lettuce growing in a floating system, and to control the incidence of Pythium irregulare. Its effect on the quality of fresh-cut red lettuce was also studied. For this, two experiments were carried out over two growing cycles (winter–spring and autumn). The results showed that the use of compost extract added to the nutrient solution improved baby leaf lettuce growth and quality, reducing the nitrate content and enhancing the content of potentially health-promoting compounds such as phenols and flavonoids and the antioxidant capacity. Microbial quality was maintained during storage and the compost extract had no negative effect on the microbial load of the final product. In addition, application of the compost decreased the population of P. irregulare in the water. It is concluded that the application of directly brewed compost extract is of potential use in a sustainable soilless production system for baby leaf red lettuce, since it improves the yield and quality of the product and is able to control the incidence of P. irregulare.

Effect of Compost Extract Addition to Different Types of Fertilizers on Quality at Harvest and Shelf Life of Spinach

“…The addition of CE to the fertilizers tested did not affect adversely the yield, except for control plants where a decrease was observed. The latter result is in agreement with that obtained by Gimenez et al [20], who applied a CE by micro-sprinkler in baby leaf lettuce grown hydroponically and obtained a lower yield than the control. Other authors [27] have reported that the application of two microbial compost teas did not result in improved crop yields in spinach.…”

“…In general, nitrate contents slightly decreased after 6 days of storage for all the treatments (except DMPP treatments) according to the results obtained by Gomez et al [34] in celery, Miceli et al [35] in rocket leaves, and Giménez et al [20] in lettuce. This is because postharvest nitrate reduction requires exogenous microbial nitrate reductase activity, which is unlikely to be achieved without visible loss of quality [36].…”

“…CE can contain biostimulant agents that increase the photosynthetic function of the plant, which can induce the activation of the plant's secondary metabolism, causing an increase in the content of total phenolics and flavonoids and boosting the antioxidant capacity in baby spinach [19]. Additionally, Giménez et al [20] demonstrated that the CE application in lettuce did not have an effect on the microbial load of the final product at harvest and during shelf-life.…”

The Effect of Compost Tea Application on some Soil Characteristics

“…Results of soil samples analysis was shown in table (1). Results of soil analysis showed very low nitrogen content of the studied samples, clay loam texture, neutral alkalinity and salinity within acceptable range.…”

Effects of Jatropha curcas L. (Euphorbiaceae) composts on biochemical, phytochemical and nutraceutical quality of sorghum (Sorghum bicolor (L.) Moench) seeds

“…The phenolic contents of seeds are linked to environmental conditions (Salazar-López et al, 2018). The application of some compost increased the production of phenolics and flavonoids contents (Lakhdar et al, 2011;Giménez et al, 2020). The availability of nitrogen should influence the amounts of phenolics more strongly than terpenoids because phenolics are produced in the same shikimic acid pathway as aromatic amino acids as suggested previously.…”