Lettuce Seedlings Research Articles

Nitrogen Accumulation and Initial Growth Response in Lettuce Planted at Different Periods After Hairy Vetch Incorporation

One-month-old lettuce seedlings were planted in the field with and without prior hairy vetch (Vicia villosa L.) incorporation (HV and Fallow, respectively). The periods between hairy vetch incorporation and lettuce planting were 1 day, 8 days and 15 days. The inorganic nitrogen concentration in the soil was higher after hairy vetch incorporation, as well as the nitrogen concentration in the lettuce leaves from the HV plot compared to the Fallow plot, at any planting period. When lettuce seedlings were planted 8 days after hairy vetch incorporation, the leaf dry weight in the HV plots was 11% lower than that in the Fallow plots 4 days after planting; however, leaf growth recovered and the dry weight was 24% higher 12 days after planting, which could be due to enhanced leaf growth as the result of additional accumulated nitrogen provided by the hairy vetch. In the incubation experiment, it was suggested that the inhibitory effect of hairy vetch decomposition was not due to allelopathic substances. Therefore, in the hairy-vetch-incorporated field, growth suppression in the lettuce plants occurred early and continued for a short period after hairy vetch incorporation, but the damage due to the growth suppression effect was minor. More importantly, nitrogen supplied from the hairy vetch promoted lettuce growth after the inhibition period.

Assessment of Drought Response in Kimchi Cabbage, Radish, and Lettuce Seedlings Using RGB Image Analysis

Assessment of Drought Response in Kimchi Cabbage, Radish, and Lettuce Seedlings Using RGB Image Analysis

Impacts of black soldier fly, Hermetia illucens, larval frass on the emergence and seedling vigor of three vegetable crop species

Abstract The waste material from rearing black soldier fly, Hermetia illucens (L.), (Diptera: Stratiomyidae), larvae (BSFL), frass, could serve as a partial replacement for fertilizer or growing media, such as peat. Studies have shown that depending on the crop life cycle, long or short, the incorporation of frass can have positive impacts on vegetable growth. Investigating the earlier stages of growth, such as emergence, can provide more information on the acute impacts of insect frass on plant production. Two greenhouse studies were designed to investigate the use of frass in vegetable production at the seedling stage: BSFL frass as a partial replacement for peat in a growth germination medium and BSFL frass as a fertility replacement in a growth germination medium. Tomato, lettuce, and arugula seeds were grown in a standard control growing media, a growing media amended with frass to partially replace peat, and a growing media with frass applications to substitute the fertility source. In all treatments and varieties, the control growing media produced better or comparable results to the treatments. As a peat replacement, the two tomato varieties, lettuce, and arugula seedlings grown in frass had comparable seedling vigour and days to emergence to those grown in the control. As a fertility replacement, seedlings grown in frass had significantly lower percent emergence in all four cultivars when compared to the control. The tomato varieties also had significantly lower seedling vigour in the BSFL fertility treatments than the control. Depending on crop and growing media composition, the impacts of frass on early plant development vary. The adoption of frass into growing practices should include preliminary tests for nutrient composition and microbial contamination.

Synthesis and characterization of novel dithiocarbamic thioanhydrides and their application for plant growth stimulant and phytotoxic activity

In this study, nineteen thioanhydrides were synthesized from the S-acylation reaction of sodium dithiocarbamates with various acyl chlorides in chloroform at room temperature. The synthesized thioanhydrides were evaluated for their growth-stimulating and phytotoxic activities. Benzoic (1a), 4-methoxy- (1b), 4-chloro- (1c), 2-bromo- (1e), 4-fluoro- (1f.) and 4-nitrobenzoic 1H-1,2,4-triazole-1-carbothioic thioanhydrides (1 g) showed moderate to excellent growth-stimulating activity, along with this (1c) exhibited excellent phytotoxic activity, 2,4-dichlorobenzoic 1H-1,2,4-triazole-1-carbothioic thioanhydride (1d) and 2,4-dichlorobenzoic pyrrolidine-1-carbothioic thioanhydride (2b) demonstrated inhibiting and moderate phytotoxic activities. Thioanhydrides (1a-c, 1f., 1 g) exhibited excellent germination energy and germination capacity of wheat seeds: 1a 82 and 90%, 1c 80 and 84%, 1 g 82 and 90% (0.01 mg/ml); 1b, 1 g 78 and 94%, 1c 78 and 90%, 1f. 80 and 94% (0.1 mg/ml). Thioanhydride (1e) showed moderate activity, germination energy and germination capacity were 72 and 76% (0.1 mg/ml), 78 and 84% (0.01 mg/ml). Thioanhydride (1d) demonstrated activity as a growth inhibitor with germination energy, and germination capacity 54 and 58% (0.1 mg/ml), 44 and 42% (0.01 mg/ml). Thioanhydride (1c) exhibited excellent phytotoxic activity analogically to herbicide 2,4-D only on lettuce seeds. Compounds (1d and 2b) were moderately active, inhibiting the growth of lettuce and bent grass seedlings.

Assessment of the efficiency of image analyzer applications in determining substrate quality for vegetable seedling development

The aim of this study is to evaluate the efficiency of images analyzer applications in determining substrate quality for vegetable seedling development. Two leaf coverage determiner apps using digital images, Canopeo and GreenTest, were tested and their values were compared with results obtained from NDVI, fresh mass, dry mass, and humidity in a substrate testing experiment for lettuce seedling development. The experiment, employing a completely redomized design with 4 treatments (control, witness, humus and organic compost) and 4 repetitions, took place in a greenhouse in Londrina, Paraná, Brazil, in April 2022. Results indicated that the Canopeo app demonstrated greater sensitivity in distinguishing between treatments and exhibited a very strong correlation with other scientifically employed analyses. In contrast, GreenTest showed moderate correlation and lower sensitivity in the analyses. In conclusion, Canopeo proves to be a reliable application for determining leaf coverage and analyzing the performance of vegetable seedlings.

Toxicity of paclobutrazol-based pesticide on Lactuca sativa L.: germination, seedling development, and DNA damage.

Paclobutrazol, a fungicide of the triazole class, is widely used as an inducer of early flowering and fruiting by inhibiting gibberellin formation. However, biological assays using model organisms to evaluate their cytogenotoxic and mutagenic potential are still scarce. Therefore, this study aimed to investigate the effects of the commercial product Cultar® 250 SC (CP) and the pure substance (PBZ) on the germination and initial seedling development of Lactuca sativa L. (lettuce), in addition to evaluating the effects of CP on the mitotic activity and DNA, as we believe that PBZ has a greater toxic potential than CP on seed germination, and that the latter has cytogenotoxic and mutagenic effects on L. sativa. Lettuce seeds treated with CP and with PBZ in the doses of 0.25, 0.50, 1, 1.5, and 2g L-1 showed significant reductions in germination rate, as well the CP reduced the root and initial development seedling development. PBZ showed greater inhibition of germination compared to CP. In direct exposure to PBZ, there was not sufficient seedling development for analysis, while in discontinuous treatment, there was inhibition of root growth (except for doses of 0.25 and 0.50g L-1) and in the development of the aerial part. While no mitodepressive effect was observed in meristematic cells treated with CP, increased frequencies of chromosomal alterations, including condensed nuclei and micronuclei, were evident in both meristematic cells and the F1 region. The Comet assay further demonstrated higher levels of DNA damage at higher paclobutrazol doses, supporting the findings of increased micronucleus frequencies. Consequently, it can be concluded that the CP exhibits greater toxicity towards seed germination compared to lettuce seedlings, and PBZ has a greater toxic potential than CP in relation to these parameters. However, the impact of CP on seedlings was relatively minimal, as evidenced by their limited effects on development, cell proliferation, and DNA, suggesting a slight toxicity of this agent. Therefore, we infer that Cultar® 250 SC should be used with caution. Thus, this study emphasizes the importance of employing joint analyses to better elucidate and correlate the mechanisms of action of potentially toxic substances. Furthermore, it provides a basis for discussing the application of Cultar® 250 SC and seeking more sustainable alternatives in food production.

From Waste to Plant Production: Cattle Dung Compost as an Alternative Nursery Substrate to Commercial Peat for Producing Lettuce Plants

The limited availability of peat-based substrates, a nonrenewable resource, and the negative environmental impacts associated with their extraction require the conservation of this resource. We assessed the use of cattle dung compost as a stand-alone nursery substrate, replacing peat substrate for the production of lettuce (Lactuca sativa L.) seedlings. A completely randomized design was employed, using cattle dung compost (C) and commercial peat (P, control treatment) in various combinations (100% P; 25% C/75% P; 50% C/50% P; 75% C/25% P; 100% C) to assess their effects on different growth parameters of lettuce. Twenty-eight parameters (e.g., seed germination, seedling survival, diameter, height, biomass growth) were assessed, corresponding to the time when the seedlings are transplanted. All treatments achieved 100% seed germination and seedling survival; indicating the successful establishment of lettuce seedlings across all tested substrates. However, seedling growth was found to be significantly influenced by substrate type. Seedling diameter was significantly increased by 10.8% in the 50% C/50% P substrate, while seedling height was significantly increased by 7.7, 6.8, and nearly 10%, respectively, within the 25% C/75% P, 50% C/50% P and 100% C substrates, relative to the control. Other substrate treatments were not significant. Similar or significantly higher values than the control were also observed for biomass growth under the tested substrates, indicating the beneficial effect of cattle dung on the initial growth of plants during the nursery phase. Cattle dung compost, used as a growing substrate, demonstrated similar or superior results to commercial peat, suggesting its potential as a viable alternative potting medium for sustainable horticulture.

Coffee and its waste repel second-stage juveniles of Meloidogyne species and inhibit their infection of lettuce roots

Summary Second-stage juveniles (J2) of Meloidogyne species are known to be repelled by several compounds. Although such repellents could serve for nematode control, effective, practical and sustainable repellents are unknown. The present study tested instant coffee crystals (ICC) and a methanolic extract of spent coffee grounds (SCG) for their repellency against, and infection inhibition of, J2 of Meloidogyne species on agar plate assays. J2 of Meloidogyne javanica, M. hapla and M. marylandi were repelled by the SCG extract and ICC. When ICC were mixed with chemical J2 attractants, their attractiveness to M. javanica J2 was reduced or abolished. ICC and the SCG extract deposited near lettuce seedling roots on the agar plate reduced the number of M. javanica, M. incognita, and M. hapla J2 attracted to the root tips by 84.3-96.4%, decreased infection rates by 37.5-75.0%, and increased root length 1.3- to 2.8-fold compared to seedlings grown on the non-treated side of the same plate. Thoroughly mixing the SCG extract into the plated agar reduced the number of J2 of the three species attracted to lettuce root tips by 46.7-98.6% and the infection rate by 87.5-95.8%, and increased the root length of the seedlings up to 2.8-fold, although no nematicidal effect was found. The same SCG-treated agar plate reduced the attraction of M. javanica J2 to a chemical attractant. The results suggest that ICC and the SCG extract have repellent and infection-inhibitory activity against Meloidogyne J2 and are potential control means for Meloidogyne species.

N-Acetylcysteine Mitigates Oxidative Stress Induced by Transplanting Lettuce Seedlings into a DFT Hydroponic System

Oxidative stress results from an imbalance between the production and accumulation of reactive oxygen species (ROS), which can impede plant growth under various environmental stresses. While waterlogging is a well-known inducer of oxidative stress, the effects of oxidative stress on plant roots grown using the deep flow technique (DFT) hydroponic system remain poorly understood. In this study, we demonstrate that N-acetylcysteine (NAC) enhances the growth of lettuce seedlings transplanted into a DFT system. NAC application significantly improved both shoot and root growth, with the most pronounced effects observed at a concentration of 0.3 mM. Moreover, NAC mitigated the accumulation of hydrogen peroxide in roots following transplantation. It also reduced a temporary increase in lipid peroxidation and total phenolic content in both roots and shoots. These results suggest that NAC functions as an antioxidant, alleviating oxidative stress by scavenging hydrogen peroxide in the roots. Importantly, NAC’s protective effects may extend to other hydroponically grown crops, offering broader potential for reducing oxidative stress across various cultivation systems.

The Selection of Lettuce Seedlings for Transplanting in a Plant Factory by a Non-Destructive Estimation of Leaf Area and Fresh Weight

Selecting uniform and healthy seedlings is important to ensure that a certain level of production can be reliably achieved in a plant factory. The objectives of this study were to investigate the potential of non-destructive image analysis for predicting the leaf area and shoot fresh weight of lettuce and to determine the feasibility of using a simple image analysis to select robust seedlings that can produce a uniform and dependable yield of lettuce in a plant factory. To vary the range of the leaf area and shoot fresh weight of lettuce seedlings, we applied two- and three-day irrigation intervals during the period of seedling production and calculated the projected canopy size (PCS) from the top-view images of the lettuce seedlings, although there were no significant growth differences between the irrigation regimes. A high correlation was identified between the PCS and shoot fresh weight for the lettuce seedlings during the period of seedling production, with a coefficient of determination exceeding 0.8. Therefore, the lettuce seedlings were classified into four grades (A–D) based on their PCS values calculated at transplanting. In the early stages of cultivation after transplanting, there were differences in the lettuce growth among the four grades; however, at the harvest (28 days after transplanting), there was no significant difference in the lettuce yield between grades A–C, with the exception of grade D. The lettuce seedlings in grades A–C exhibited the anticipated yield (150 g/plant) at the harvest time. In the correlation between the PCS and leaf area or the shoot fresh weight of lettuce during the cultivation period after transplanting and the entire cultivation period, the R2 values were higher than 0.9, confirming that PCS can be used to predict lettuce growth with greater accuracy. In conclusion, we demonstrated that the PCS calculation from the top-view images, a straightforward image analysis technique, can be employed to non-destructively and accurately predict lettuce leaf area and shoot fresh weight, and the seedlings with the potential to yield above a certain level after transplanting can be objectively and accurately selected based on PCS.

Mobility and growth in confined spaces are important mechanisms for the establishment of Bacillus subtilis in the rhizosphere.

The rhizosphere hosts complex and abundant microbiomes whose structure and composition are now well described by metagenomic studies. However, the dynamic mechanisms that enable micro-organisms to establish along a growing plant root are poorly characterized. Here, we studied how a motile bacterium utilizes the microhabitats created by soil pore space to establish in the proximity of plant roots. We have established a model system consisting of Bacillus subtilis and lettuce seedlings co-inoculated in transparent soil microcosms. We carried out live imaging experiments and developed image analysis pipelines to quantify the abundance of the bacterium as a function of time and position in the pore space. Results showed that the establishment of the bacterium in the rhizosphere follows a precise sequence of events where small islands of mobile bacteria were first seen forming near the root tip within the first 12-24 h of inoculation. Biofilm was then seen forming on the root epidermis at distances of about 700-1000 µm from the tip. Bacteria accumulated predominantly in confined pore spaces within 200 µm from the root or the surface of a particle. Using probabilistic models, we could map the complete sequence of events and propose a conceptual model of bacterial establishment in the pore space. This study therefore advances our understanding of the respective role of growth and mobility in the efficient colonization of bacteria in the rhizosphere.

Myrtus communis leaf extracts repel Meloidogyne spp. second‐stage juveniles and prevent root infection

AbstractThe use of repellents for nematode control has not been established. Leaf extracts of Myrtus communis, an evergreen shrub with wide distribution in the Mediterranean and some other regions, were tested for repellence of second‐stage juveniles (J2s) of Meloidogyne species. Extracts obtained with several solvents and water repelled M. javanica J2s on agar plates, with the 60% methanol extract showing the highest repellent activity. M. hapla J2s were also repelled by the aqueous and 60% methanol extracts. Adding the 60% methanol extract to fluopyram, a chemical J2 attractant, reduced and abolished, respectively, the attraction of M. javanica and M. hapla J2s to it. When the methanolic extract was added near lettuce seedling roots on an agar plate, the number of M. javanica, M. incognita and M. hapla J2s attracted to the root tips was reduced by 70.0%–98.2%, infection rates decreased by 50.1%–95.8% and root length increased by 61.8%–186.7% compared to control seedlings grown on the same plates. When the methanol extract was mixed into the agar plate, the three Meloidogyne species' attraction to and infection of lettuce seedlings was reduced by up to 75.4% and 100%, respectively, and root length increased up to 3.4‐fold. The acetone extract mixed into the agar reduced the attraction of M. javanica J2s to fluopyram but did not affect their repellence by KNO3. The results suggest that M. communis leaf extracts have repellent and infection‐inhibitory activity against Meloidogyne J2, offering potential control means for Meloidogyne species.

Biomass of Eichhornia crassipes as an Alternative Substrate for the Formation of Lettuce Seedlings

The production of lettuce has increased significantly due to the use of hydroponic systems that rely on substrates. Disposal and acquisition costs present problems, necessitating the identification of sustainable alternatives. The present study aimed to evaluate the use of Eichhornia crassipes (water hyacinth) dry matter in a substrate for the formation of lettuce seedlings. Water plants were collected to obtain their dry matter, and twelve mixtures were formed with Sphagnum and perlite. Mixtures with more water hyacinth dry matter exhibited greater water retention. However, these mixtures also lost water at a faster rate than those containing primarily Sphagnum dry matter did. Higher percentages of germination were detected in the mixtures with water hyacinth dry matter, but these seedlings also presented higher concentrations of proline, such as 16.0 µg mL−1. The mixtures with water hyacinth dry matter presented the highest ion concentrations, mainly at high levels of humidity. Mixtures with a high proportion of water hyacinth dry matter had a greater water retention capacity and a high percentage of lettuce seed that germinated. The mixtures with a higher proportion of Sphagnum led to greater root length, greater concentrations of chlorophyll in cotyledonary leaves, and better morphological development of the seedlings.

Growing lettuce seedlings in different organic composts used as substrate

Lettuce is the most important vegetable in the world and the most consumed in Brazil. Seedling production with a good quality substrate is very important in the lettuce crop production process. The objective of this study was to evaluate the performance of organic compost substrates in the production of lettuce seedlings. The experiment was carried out in a greenhouse, using polyethylene trays containing 128 trapezoidal cells in a completely randomized design with a 5 × 2 factorial scheme consisting of 5 substrates (commercial substrate; compost I; compost II; compost III; compost IV) and P2O5 supplementation (absent and 0.525 kg m−3 P2O5) and 4 replications. Substrates were produced by composting agro-industrial waste: sawdust, wood shavings and residues from a restaurant, pig litter, cattle manure, residues from the shoot and tubers of sweet potato, soybean residue, and drained bovine ruminal residue. The emergence, plant height, number of leaves, fresh root and shoot biomass, and clod stability of the substrate were evaluated. The substrate formulated from pig litter, cattle manure, and sweet potato (compost II) and pig litter and drained bovine ruminal residue (compost IV) formed seedlings with a greater clod stability of the substrate, plant height, number of leaves, and fresh root and shoot biomass. Substrates based on composting pig litter, cattle manure, and sweet potato (composts II) and pig litter and drained bovine ruminal residue (compost IV) were most suitable for producing lettuce seedlings.

Foliar spraying with amino acids and their chitosan nanocomposites as promising way to alleviate abiotic stress in iceberg lettuce grown at different temperatures

We analyzed the effects of foliar spraying with amino acids, chitosan (CHS) and nanocomposites (NCs) of chitosan with the amino acids proline, l-cysteine and glycine betaine (CHS-Pro NCs; CHS-Cys NCs, CHS-GB NCs, respectively) on the changes in the physiological and biochemical parameters of iceberg lettuce grown at the control temperature (20 °C) and under chilling conditions (4 °C). The physicochemical parameters of the phospholipid monolayers (PLs) extracted from plants showed the effects of the treatments on the properties of the monolayers, namely, the packing density and flexibility. We observed increased accumulation of proline at 4 °C, and differences in the concentrations of sugars in most of the analyzed variants were a consequence of the lowered temperature and/or the use of organic compounds. A temperature of 4 °C caused a significant increase in the l-ascorbic acid level compared with that at 20 °C. Differences were also found in glutathione (GSH) content depending on the temperature and treatment with the tested organic compounds. CHS NCs loaded with Pro and GB were effective at increasing the amount of phenols under stress temperature conditions. We noted that a significant increase in the antioxidant activity of plants at 4 °C occurred after priming with Cys, CHS-Cys NCs, Pro and CHS-Pro NCs, and the CHS nanocomposites were more effective in this respect. Both low-temperature stress and foliar spraying of lettuce with various organic compounds caused changes in the activity of antioxidant enzymes. Two forms of dismutase (SOD), iron superoxide dismutase (FeSOD) and copper/zinc superoxide dismutase (Cu/ZnSOD), were identified in extracts from the leaves of iceberg lettuce seedlings. The application of the tested organic compounds, alone or in combination with CHS, increased the amount of malondialdehyde (MDA) in plants grown under controlled temperature conditions. Chilling caused an increase in the content of MDA, but some organic compounds mitigated the impact of low temperature. Compared with that of plants subjected to 20 °C, the fresh weight of plants exposed to chilling decreased. However, the tested compounds caused a decrease in fresh weight at 4 °C compared with the corresponding control samples. An interesting exception was the use of Cys, for which the difference in the fresh weight of plants grown at 20 °C and 4 °C was not statistically significant. After Cys application, the dry weight of the chilled plants was greater than that of the chilled control plants but was also greater than that of the other treated plants in this group. To our knowledge, this is the first report demonstrating that engineered chitosan–amino acid nanocomposites could be applied as innovative protective agents to mitigate the effects of chilling stress in crop plants.

Molecular characterization and transcriptional response of Lactuca sativa seedlings to co-exposure to graphene nanoplatelets and titanium dioxide nanoparticles

The widespread use of nanomaterials in agriculture may introduce multiple engineered nanoparticles (ENPs) into the environment, posing a combined risk to crops. However, the precise molecular mechanisms explaining how plant tissues respond to mixtures of individual ENPs remain unclear, despite indications that their combined toxicity differs from the summed toxicity of the individual ENPs. Here, we used a variety of methods including physicochemical, biochemical, and transcriptional analyses to examine the combined effects of graphene nanoplatelets (GNPs) and titanium dioxide nanoparticles (TiO2 NPs) on hydroponically exposed lettuce (Lactuca sativa) seedlings. Results indicated that the presence of GNPs facilitated the accumulation of Ti as TiO2 NPs in the seedling roots. Combined exposure to GNPs and TiO2 NPs caused less severe oxidative damage in the roots compared to individual exposures. Yet, GNPs and TiO2 NPs alone and in combination did not cause oxidative damage in the shoots. RNA sequencing data showed that the mixture of GNPs and TiO2 NPs led to a higher number of differentially expressed genes (DEGs) in the seedlings compared to exposure to the individual ENPs. Moreover, the majority of the DEGs encoding superoxide dismutase displayed heightened expression levels in the seedlings exposed to the combination of GNPs and TiO2 NPs. The level of gene ontology (GO) enrichment in the seedlings exposed to the mixture of GNPs and TiO2 NPs was found to be greater than the level of GO enrichment observed after exposure to isolated GNPs or TiO2 NPs. Furthermore, the signaling pathways, specifically the “MAPK signaling pathway-plant” and “phenylpropanoid biosynthesis,” exhibited a close association with oxidative stress. This study has provided valuable insights into the molecular mechanisms underlying plant resistance against multiple ENPs.

Analysis of the Physicochemical Parameters of Millicompost and Vermicompost Produced at IFS Aracaju with the Development of Arugula and Lettuce Seedlings

O problema da geração de resíduos sólidos ainda é uma séria questão a se resolver. O gerenciamento de resíduos tem como disposição final apenas os aterros sanitários, já para uma destinação ambientalmente sustentável há diversas possibilidades. Sendo os resíduos orgânicos facilmente putrescíveis, essas possibilidades incluem práticas que podem ser feitas em casa, como a compostagem, a vermicompostagem e a gongocompostagem. O projeto “Vem e Composta” realiza a vermicompostagem no IFS Aracaju desde 2020, mas recicla pouco material vegetal seco. Neste sentido, devido à necessidade de reduzir os resíduos castanhos produzidos no campus, implantou-se a gongocompostagem. Esta técnica instalou-se em 2022 com a montagem de dois gongolários feitos com lixeiras de 60 litros reutilizadas, onde foi iniciada a compostagem de folhas e galhos secos com diplópodes coletados em zonas urbanas de Aracaju. O intuito deste trabalho foi produzir composto orgânico de pronto uso e, posteriormente, comparar com o vermicomposto que já é produzido na casa de vegetação do campus. O gongocomposto apresentou teores de umidade (77,62%), carbono (80,2 g kg-1), nitrogênio (15,5 g kg-1), cálcio (3,95 g kg-1) e magnésio (1,04 g kg-1) maiores que os do vermicomposto. O vermicomposto mostrou-se mais rico em fósforo (0,298 g kg-1) e potássio (4,8 g kg-1) e mais denso que o húmus de gongolo. O pH para ambos foi semelhante. O gongocomposto mostra-se como uma alternativa eficaz para tratamento de resíduos de poda e produção de substrato de qualidade, promovendo maior taxa de germinação e desenvolvimento de sementes de alface e rúcula quando comparado com o vermicomposto.

Potential of producing organic lettuce seedlings without peat using agricultural and agro-industrial compost

Peat is an unrenewable resource. Compost can partially replace peat in the growing seedling substrates due to its high electrical conductivity (EC), bulk density (BD), and pH. This study aimed to assess the potential of substituting peat for seedling substrate with compost made from a mixture of agricultural and agro-industrial wastes. Four compost piles (C1–C4) were constructed as follows: C1: a 1:1:1.5 weight ratio mixture of filter mud, mushroom waste, and date-palm fronds, while C2–C4: a 0.5:1 weight ratio mixture of either bagasse, cutting grassland, or date-palm fronds and cattle dung. After four months of decomposition, the compost’s physical, chemical, and biological properties were estimated in comparison to commercial compost (CC), peatmoss (PM), and their ideal ranges (IR) for seed germination and seedling growth. Composts differed significantly in their physical and chemical properties. Some composts revealed property values within the IR. In comparison to PM, Composts have a lower C/N ratio and organic matter, along with higher BD, EC, and pH. Cattle manure enhanced organic matter and carbon, total nitrogen and potassium, and ammonium levels, and reduced ash levels in C2–C4 compared to filter mud in C1. In winter 2018 and 2019, C1–C4 substrates were compared with CC and PM substrates to determine their suitability for producing crisp lettuce ‘Big Bell’ seedlings under plastic-house conditions. Substrates had significant effects on lettuce seedling traits. Shoots of C2–C4 substrate seedlings grew more rapidly than those of other substrate seedlings due to the increased length and diameter of their stem and leaf area.

Sheep manure compost: a viable growing substrate for lettuce seedling production

Sheep manure compost: a viable growing substrate for lettuce seedling production

Soil Type and Associated Microbiome Influence Chitin's Growth Promotion Effect in Lettuce

Chitin amendment of peat substrate has been proven effective in promoting lettuce growth and increasing phenolic compounds in lettuce seedlings. However, the effect of chitin soil amendment on lettuce growth in mineral soil remains unexplored. The effect of chitin amendment of mineral soil on lettuce growth and metabolite changes was investigated for the first time in the present study in comparison with chitin-amended peat substrate. Our findings showed that chitin addition in peat substrate increased lettuce head weight by approximately 50% at harvest, whereas this increase was 30% when chitin was added to mineral soil. Targeted metabolomics analysis indicated that chitin addition affected the phenolic compounds in lettuce seedlings, but this effect varied between soil types. Moreover, untargeted metabolomics analysis suggested that using peat substrate or mineral soil had a greater influence on produced lettuce metabolites than chitin addition. Rhizobiome analysis showed that specifically Mortierellaceae family members, known for chitin degradation and plant growth promotion, significantly increased in peat substrate upon chitin treatment. In mineral soil, three bacterial genera and five fungi, including known plant-growth-promoting genera, were significantly more abundant upon chitin treatment but Mortierellaceae family members were not. We assume that the observed effects primarily stem from soil characteristics and from chitin-induced alterations in rhizobiome composition, particularly the presence of Mortierellaceae members, leading to promoted lettuce growth. Despite the variability, chitin remains an environmentally friendly alternative to synthetic fertilizers in lettuce production, but its beneficial effects are dependent on rhizobiome composition, which should be considered before chitin application. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .