Promising Composts as Growing Media for the Production of Baby Leaf Lettuce in a Floating System

Abstract

The floating system is a successful strategy for producing baby leaf vegetables. Moreover, compost from agricultural and agri-food industry wastes is an alternative to peat that can be used as a component of growing media in this cultivation system. In this study, we experimented with three composts containing tomato (Solanum lycopersicum L.), leek (Allium porrum L.), grape (Vitis vinifera L.), and/or olive (Olea europaea L.) mill cake residues, which were used as the main component (75/25 volume/volume) of three growing media (GM1, GM2 and GM3) to evaluate their effect on the growth and quality of red baby leaf lettuce (Lactuca sativa L.). We used a commercial peat substrate as a control treatment (100% volume) and in mixtures (25% volume) with the composts. The plants were cultivated over two growing cycles, in spring and summer, and harvested twice in each cycle when the plants had four to five leaves. We found that the percentage of seed germination was significantly higher in plants grown in peat than in those grown in compost growing media. The yield was affected by the growing media in the summer cycle, and we obtained the highest value with GM1. Furthermore, the second cut was more productive than the first one for all the growing media in both cycles. The lettuce quality was also affected by the growing media. In general, the total phenolic content and antioxidant capacity in the leaves was higher in plants grown in the compost growing media, particularly in the second cut, but the nitrate content in the leaves was greater in some of the compost treatments compared with the peat treatment. In addition, an in vitro suppressive activity study demonstrated that the interaction between different fungi and bacteria observed through metagenomics analysis could contribute to the effectiveness of the compost in controlling Pythium irregulare. The use of compost as a component of the growing media in the production of baby leaf vegetables in a floating system does not only favor the crop yield and product quality, but also shows suppressive effects against P. irregulare.

Estimation of Yield, Photosynthetic Rate, Biochemical, and Nutritional Content of Red Leaf Lettuce (Lactuca sativa L.) Grown in Organic Substrates

“…As a result, neither pH nor EC had any negative effects on plant development. These findings are consistent with Morales et al [30] and Giménez et al [31].…”

“…According to Lakhdar et al [43], compounds rich in the ability to cause an oxidative process in plants can be found in the compost made from tomato, leek, vineyard, and olive mill cake residues used as growing media. These compounds stimulated the secondary metabolites in lettuce grown in various agroindustrial byproducts [31,44]. In greenhouse cultivation, temperature rises in the root zone of leafy vegetables can cause changes in the development of secondary metabolites, primarily phenolic compounds [45,46].…”

Comparison of organic substrates in urban rooftop agriculture, towards improving crop production resilience to temporary drought in Mediterranean cities

“…Although this is a parameter that we have not measured, there is research on the positive effect of the presence of organic matterin this case, compost. Several positive interactions given by the presence of biological activity can be mentioned, including the suppressive effects against pathogens 26,27 www.soci.org F Parada et al…”

Strategic Successive Harvesting of Rocket and Spinach Baby Leaves Enhanced Their Quality and Production Efficiency

“…Among several methods of hydroponically grown crops, the floating system is the easiest and cheapest means of leafy vegetables' production [11]. Floating is a closed system with important benefits such as low cost, water and nutrient use efficiency, environmentally friendly, production efficient, and it provides the option for mechanization and automation of crop production [12,13].…”

“…These leafy vegetables revegetate after the first harvest, and thus, it is possible to conduct four or five successive harvests in a few weeks since their roots remain intact. Apart from time shortening between harvests, this approach results in cost reduction, resource use limitation, and labor facilitation [11]. Specifically, compared to several individual sowings, cultivations, and harvests, revegetation facilitates baby leaf production by limiting the initial resources needed (i.e., seeds, trays, substrates), as well as conserving water and nutrients, which are only replenished when needed.…”