Lettuce Production Research Articles

Assessment of adaptive neuro-fuzzy inference system (ANFIS) to predict production and water productivity of lettuce in response to different light intensities and CO2 concentrations

The accurate estimation of water productivity (WP) and plant production becomes imperative in planning and managing irrigation practices. Light intensity and CO2 concentration are among the most important determinants of growth and WP of crops. In this study, the adaptive neuro-fuzzy inference system (ANFIS) was used to model the changes in growth parameters, stomatal properties, and WP of lettuce due to various scenarios of light intensity and CO2 concentration. The lettuce plants were exposed to four levels of light intensity [75, 150, 300, and 600 µmol m−2 s−1 Photosynthetic Photon Flux Density (PPFD)] and CO2 concentration (400, 800, 1200, and 1600 ppm). The results showed that growth parameters such as fresh weight, dry weight, and leaf area improved by increasing the PPFD and CO2 concentration from 75 to 300 µmol m−2 s−1 and 400–1200 ppm, respectively. Maximum fresh weight was recorded at 300 µmol m−2 s−1 PPFD and 1600 ppm CO2 concentration while the highest dry weight was obtained at 600 µmol m−2 s−1 PPFD and 1600 ppm CO2 concentration. Stomatal pore width and length decreased by increasing PPFD and CO2 concentration. Moreover, evapotranspiration increased when plants were exposed to higher PPFDs and CO2 concentrations. ANFIS predicted all growth parameters, stomatal properties, and WP with acceptable performance (R2 > 0.99, RMSE < 0.8 ×10−2). The findings provide agricultural engineers with an artificial intelligence-based model to predict the WP and production of lettuce by having the light intensity and CO2 concentration.

Evaluation of growth and phenolic compounds profile of purple lettuce under indoor cultivation

The objective of this study was to observe indoor cultivation system with LED lights (white and infrared) to purple lettuce cv. Mimosa in a micro-growing environment for home cultivation. A conventional cultivation with white lamps was used as a Control. The quality of lettuce was evaluated by measuring several parameters, including the number of commercial leaves (intact)/plant, stem diameter, height of the aereal portion, leaf area, absolute growth rate and productivity. Also individual phenolics contents and photosynthesis parameters were evaluated. The results obtained showed that indoor cultivation growing results around 60% higher number of leaves per plant and 4.75 x more leaf area in comparison to Control treatment (28 days after transplant). In addition, productivity and absolute growth rate of purple lettuce were positively affected by indoor cultivation system (a leaf area difference of 300 g.cm -2 more than the Control). The light intensity provided by the LED’s resulted in increased biomass and yield, mainly due to the elevated photosynthetic activity of plants. At the same time, individual phenolic compounds like chlorogenic acid, caffeic acid, chicoric acid, luteoline-7- o -glucoronide, quercetin-3-malonylglucoside, quercetin acetyl hexoside and cyanidine 3- o -malonylglucoside were identified in purple lettuce cv. Mimosa. Therefore, indoor cultivation system is a viable option to provide the consumer a more natural, practical and healthy food.

Sensitivity of lettuce cultivar Lucy Brown to pre-planting herbicide application

ABSTRACT Due to the low availability of herbicide active ingredients, the chemical weed management in lettuce crop is a challenge. The aim of this study was to evaluate the sensitivity of lettuce to the pre-planting application of the herbicides flumioxazin and trifluralin alone or in tank-mixture in lettuce, Lucy Brown cultivar. Two experiments were conducted. In experiment A, the soil was tilled before the herbicide application and it was tilled again before seedling transplanting. In experiment B, the soil was tilled just once before the herbicide application. The experimental design was in randomized blocks in a factorial scheme (3x3) +1 (2 factors with 3 levels and an additional control) with 4 replicates. We applied flumioxazin (120 g ha-1), trifluralin (450 g ha-1) and flumioxazin + trifluralin (120 + 450 g ha-1) in three different seasons before transplanting (0, 7 and 14 days). Lettuce productivity after trifluralin application (48.4 t ha-1) was higher than after flumioxazin application (16.8 t ha-1) in experiment A. In experiment B, flumioxazin decreased the number of lettuce leaves (25.6) at 14 DAT; no differences in lettuce productivity were verified, though. The herbicide trifluralin caused lower levels of phytotoxicity and was the most selective between the treatments when applied in the three seasons in both experiments.

Expression Profiling of Heat Shock Protein Genes as Putative Early Heat-Responsive Members in Lettuce

High temperatures due to global warming can cause harmful effects on the productivity of lettuce, a cool-season crop. To identify lettuce heat shock protein (HSP) genes that could be involved in early responses to heat stress in plants, we compared RNA transcriptomes between lettuce plants with and without heat treatment of 37 °C for 1 h. Using transcriptome sequencing analyses, a total of 7986 differentially expressed genes (DEGs) were identified including the top five, LsHSP70A, LsHSP70B, LsHSP17.3A, LsHSP17.9A and LsHSP17.9B, which were the most highly differentially expressed genes. In order to investigate the temporal expression patterns of 24 lettuce HSP genes with a fold-change greater than 100 under heat stress, the expression levels of the genes were measured by qRT-PCR at 0, 1, 4, 8, 14, and 24 h time points after heat treatment. The 24 LsHSP genes were classified into three groups based on the phylogenetic analysis and/or major domains available in each protein, and we provided a potential link between the phylogenetic relationships and expression patterns of the LsHSP genes. Our results showed putative early heat-responsive lettuce HSP genes that could be possible candidates as breeding guides for the development of heat-tolerant lettuce cultivars.

In-Field Evaluation of Drone-Released Lacewings for Aphid Control in California Organic Lettuce.

Aphids are one of the most economically important pests to California's Central Coast lettuce industry. Aphids vector the lettuce mosaic virus and are crop contaminants in the packaging of the product. Lettuce aphid, Nasonovia ribisnigri (Mosley) (Hemiptera: Aphididae), is one of the predominant aphid species in lettuce, and it poses unique management challenges forming colonies inside the lettuce head. Current management practices rely on repeated foliar insecticide applications to reduce aphid densities per plant. Some organic growers have explored the release of laboratory-reared beneficial insects to manage aphids in their commercial fields. This project sought to document the effects of drone-released lacewing eggs on lettuce aphid densities in organic romaine lettuce fields. Commercially reared lacewing eggs were released at a rate of 74,131 eggs/ha and organic-certified insecticides were sprayed following their respective label recommendations. Our results could be interpreted as preliminary evidence that drone release of lacewings could reduce aphid densities (15.6-150.0 aphids/lettuce head) when compared to the untreated plots (32.1-257.9 aphids/lettuce head). Aphid densities were also decreased after the application of foliar organic-certified insecticides (11.77-143.5). Traditionally, the cost of labor has limited the use of beneficials in the lettuce production system, but the use of drones for these releases may make this strategy more attractive. Based on our calculations, spraying an organic-certified insecticide is less expensive (direct operational costs of U.S. $ 116.36/ha) than releasing beneficial insects by hand ($ 185.40) or by drone ($ 176.00) when mimicking the conditions of this study.

Evaluation of Lettuce (Lactuca sativa L.) Production under Hydroponic System: Nutrient Solution Derived from Fish Waste vs. Inorganic Nutrient Solution

Organic fresh products are appreciated and are gaining a good reputation regarding human health and environmental concerns. Despite the fact that hydroponics are commonly used in vegetable production, growers are looking for sustainable cultivation systems. Therefore, the objective of this study was to investigate the effect of using an organic-based nutrient solution (NS) derived from fish waste in a hydroponic system on the vegetative growth and production of lettuce compared to a conventional inorganic NS. Plant growth, yield, physiological and nutrient content parameters were determined. The results revealed that the overall growth and fresh biomass of the organic NS grown lettuce were relatively lower than those of the inorganic NS. Stomata density was significantly higher in inorganic grown lettuce compared to the organic one. However, the total chlorophyll, carotene, phenolic compounds, and flavonoid contents, as well as antioxidant activity were significantly higher in lettuce grown in organic NS compared to the inorganic one. Leaf nutrient content at harvest was significantly impacted by the type of used fertilizer. Based on these findings, in hydroponic system, organic liquid fertilizer derived from fish waste (as an alternative NS source) requires further improvements to achieve optimal growth and yield comparable to that of conventional inorganic NS.

Effect of Organic Liquid Vermicompost as a Substitute for Chemical Fertilizer on Morphological and Biochemical Characteristics in Lettuce.

The use of organic vermicompost fertilizers is considered one of the promising fertilizer. Therefore, the experiment aimed to study the effect of using liquid vermicompost fertilizer as an alternative to chemical fertilizers in the production of lettuce, Crisp head variety. In this study, a field experiment was conducted during the two winter seasons of 2019-2020 and 2020-2021 at the Agricultural Research Station in the Abies region, affiliated to the Faculty of Agriculture, Alexandria University Egypt. This experiment aimed to evaluate the response of lettuce plants to the application of liquid vermicompost (LVC) fertilizer through four different concentrations (2.5%, 5%, 10%, and 20%), and the chemical fertilization treatment (100% NPK) in the recommended rate as a control treatment for lettuce production, on some vegetative growth characters; Fresh weight plant-1 (kg), head net weight plant-1 (kg), total yield fed-1 (ton), and unmarketable yield fed-1 (ton), in addition to some biochemical characteristics; vitamin C, dry matter, total soluble solids, and carbohydrates as well as estimate the element content and quality elements, such as nitrogen (N+), potassium (K+), phosphorus (P+), calcium (Ca2+), magnesium (Mg2+), and iron (Fe2+). The results showed a gradual significant increasing in the values of most of the studied traits by increasing the concentrations of vermicompost fertilizer from 2.5 % to 20%. The application of vermicompost treatment with a concentration of 20% LVC gave the highest significant values for most of the studied traits without a clear significant difference compared to the chemical fertilizer 100% NPK.

Intercropping pea (pisum sativum) with lettuce (lactuca sativa) and its Impact on the Growth, Yield and Nutritional Quality

A field experiment was carried out during the two successive seasons of 2017/18 and 2018/19. The aims of the experiment were to investigate the effect of different planting arrangement patterns: T1 (3 pea: 1 lettuce), T2 (2 pea: 1 lettuce), T3 (1 pea:1 lettuce), T4 (side pea: side lettuce) in addition to sole lettuce and sole pea (control) treatments regarding the growth, yield, and nutritional quality, along with the financial aspects of applying intercropping systems for lettuce and pea productivity. The obtained results revealed that all intercropping treatments except for T4 (side pea: side lettuce) treatment reduced the pea yield by 17%-62.9% and 17.2%-61.6% but increased the lettuce yield by 12.2%-37.7% and 27.7%- 60 % in the first and second seasons respectively according to the intercropping system applied. The highest pea yields were produced by both sole pea andT4 treatments, while the lowest pea yield was form T3, in both seasons. T3 treatment depressed pea pod yield to 60% of its mono-cropped yield. On the other hand, T1 and T2 treatments produced the highest yield for lettuce in both seasons. Intercropping lettuce with pea, led to an improvement in the protein percentage in pea. LER of pea/lettuce intercropping treatments were more than unit. Moreover, the highest values for both LER and MAI obtained fromT1 treatment. Calculated “aggressiveness” suggested that all secondary crop treatments were more dominant than pea in all intercropping treatments.

Nutrient Dynamics in Sandy Soil and Leaf Lettuce Following the Application of Urea and Urea-Hydrogen Peroxide Impregnated Co-Pyrolyzed Animal Manure and Bone Meal

There is a paucity of data regarding the effect of nutrient-enriched biochar amendments on nutrient dynamics in both soil and crops. This is important because unlike pristine biochar, nutrient-enriched biochar is applied to the soil in minute quantities as large amounts may led to over application of the nutrients loaded in it. The current study examined the effects of both phosphorus- and nitrogen-enriched biochars on the dynamics of both macro and micronutrients in the sandy soil and leaf lettuce grown thereon. The phosphorus enrichment followed co-pyrolysis of animal manure (cow dung) with 25% and 50% bone meal (w/w), while the nitrogen enrichment was achieved by soaking the co-pyrolyzed biochar into urea and urea-hydrogen peroxide. The performances of the nutrient-enriched biochar were compared with the conventional amendment of urea and triple superphosphate (TSP) in the production of leaf lettuce over a period of two seasons in a pot experiment. The nutrient-enriched biochar amendments resulted into higher microbial biomass carbon and carbon to nitrogen ratios than the conventional amendment. The conventional amendment caused more phosphorus, potassium, and magnesium accumulations in the leaf lettuce than the nutrient-enriched biochar amendments. The nutrient-enriched biochar amendments led to more accumulations of nitrogen, calcium, and micronutrient elements in the leaf lettuce and availabilities of all the nutrient elements in the soil and thus, nutrient-enriched biochar acted as a reservoir that could provide nutrients to the growing lettuce beyond a single growing season.

Fate of enteric viruses during leafy greens (romaine lettuce) production using treated municipal wastewater and AP205 bacteriophage as a surrogate

Water reuse programs are being explored to close the gap between supply and demand for irrigation in agriculture. However, these sources could contain hazardous microbial contaminants, and pose risks to public health. This study aimed to grow and irrigate romaine lettuce with inoculated wastewater effluent to track AP205 bacteriophage prevalence through cultivation and post-harvest storage. AP205 is a bacteriophage and was used as a surrogate for enteric viruses. Low and high dosages (mean ± standard deviation) of AP205 at 4.8 ± 0.4 log PFU/mL and 6.6 ± 0.2 log PFU/mL; respectively, were prepared to examine viral load influence on contamination levels. Foliage, leachate, and soil contamination levels were directly related to AP205 concentrations in the effluent. AP205 concentrations increased throughout cultivation for foliage and leachate, suggesting bacteriophage accumulation. During post-harvest storage (14 day at 4 °C), there was a significant decrease in AP205 concentration on the foliage. Results show that wastewater effluents usage for leafy greens cultivation can pose risks to humans and additional steps are required to safely apply wastewater effluents to soils and crops.

Seasonal occurrence and abundance of norovirus in pre- and postharvest lettuce samples in Nanjing, China

To assess the contamination of lettuce with norovirus in Nanjing city (China), two hundred and eighty one lettuce samples were collected between 2017 and 2018 from production sites (preharvest) and retail outlets (postharvest) and analyzed. The presence of norovirus was confirmed in 26.9% (71/264) of lettuce samples, with norovirus genogroup I detected more frequently (20.1%) than norovirus genogroup II. Norovirus was detected less frequently in lettuce samples from supermarkets (4.9%) than in samples from greengrocers or farmer markets (36.5%) and was detected both in field-grown (28.9%) and in hydroponic lettuce samples (30%). The norovirus occurrence and levels varied markedly by seasons. The norovirus was more frequently detected in the cold season, with evident correlations between norovirus contamination and ambient temperatures. Interestingly, the norovirus occurrence in loose lettuce was significantly higher (p < 0.05) than in packaged lettuce, highlighting that norovirus contamination might have occurred during lettuce production. The data of this study add to the currently limited body of information on norovirus occurrence in fresh produce in China, highlighting the need for implementation of effective food safety monitoring and management.

LED versus HPS Lighting: Effects on Water and Energy Consumption and Yield Quality in Lettuce Greenhouse Production

High-pressure sodium (HPS) lighting is increasingly replaced by LED lighting in lettuce greenhouse cultivation. In contrast to HPS lighting, LEDs do not heat radiation. Therefore, the leaf temperature is significantly lower under LEDs. This raises the question of whether LED lighting has a positive impact on the reduction in water consumption during lettuce production. In this paper, we investigated this question and found that the water consumption of lettuce produced under LEDs was significantly lower (−15%) than under HPS without loss of yield. We also found that supplementary lighting increases the concentrations of caffeoylquinic acid, dicaffeoyltartaric acid, dicaffeoylquinic acid and that of the total phenolic compounds in lettuce leaves by 61%, 39%, 163% and 38%, respectively. Only the LED fixture was also efficient enough to increase the concentration of caffeoyltartaric acid (+24%). Most of the phenolic compounds showed a very strong positive correlation with the chlorophyll concentration in lettuce, which predominated in the leaves exposed to the LED lighting. Based on these facts, we conclude that by optimizing the light composition, more sustainable plant production, higher concentrations of chlorophyll and some phenolic compounds are possible.

First Report of Fusarium oxysporum f. sp. lactucae Race 1 Causing Fusarium Wilt of Lettuce in Norway.

Lettuce (Lactuca sativa L.) is produced in Norway both in field and greenhouses. In Norway, greenhouse lettuce is one of the most important vegetables grown year-round. In winter 2018, wilting symptoms were observed on soil-grown lettuce of the cultivar Frillice in a greenhouse in south east Norway (Buskerud county). Affected plants showed stunted growth, wilting of outer leaves, and brownish discoloration of vascular tissues of taproots and crowns. According to the producer, the disease led to an estimated 10% of yield losses. Fungal isolates were obtained from crowns and roots of diseased plants collected from the greenhouse in 2018 and 2019. Two single spore isolates, 231274 from 2018 and 231725 from 2019, were used in further studies. The isolates were incubated on synthetic nutrient-poor agar (SNA) at 18-20 ⁰C, and a 12 hours dark, 12 hours UV light cycle. Isolate 231274 produced abundant macro- and microconidia characteristics of Fusarium oxysporum while macroconidia were never observed in isolate 231725. On potato dextrose agar (PDA), colonies of isolate 231274 were purple in color and colonies of isolate 231725 were pinkish with abundant aerial mycelium. For PCR-assay, DNA from mycelia was extracted using Easy-DNA kit (Invitrogen). A portion of the translation elongation factor 1-α (EF1-α) gene was amplified using primers F-728F (Carbone and Kohn. 1999) and EF2 (O'Donnell et al. 1998) as described by Aas et al. 2018. Blast analysis of both sequences (accession no. MW316853 for 231274 and MW316854 for 231275) obtained a 99% homology with the sequence of Fusarium oxysporum f.sp. lactucae (FOL) race 1 strain S1 (accession no. DQ837657)(Mbofung et al. 2007). Both isolates were identified as race 1 by using specific primers Hani3' and Hanilatt3rev (Pasquali et al. 2007) as described by Cabral et al. 2014. To complete Koch's postulate, lettuce plants of the cultivar Frillice were used. Race identity was confirmed using the differential lettuce cultivars Costa Rica No.4 (resistant to FOL race 1), Banchu Red Fire (resistant to FOL races 2 and 4) and Romana Romabella (resistant to FOL races 1 and 2) (Gilardi et al. 2017) provided by the breeding company Rijk Zwaan (De Lier, The Netherlands). For inoculation, roots of six 2-weeks old seedlings per cultivar were dipped in a spore suspension (1 x 106 CFU/ml) for 1 min, while controls were dipped in distilled water. Seedlings were planted in 250 ml pots containing fertilized potting substrate, and were placed in a greenhouse with temperature ranging from 15 to 35 ⁰C and an average of 23 ⁰C. After 10 days reduced growth was observed in cultivars Frillice and Banchu Red Fire for both fungal isolates. After 25 days wilting was observed in both cultivars. Affected plants presented discoloration of vascular tissue. No difference in growth was observed between cultivars Romana Romabella and Costa Rica No. 4 and their respective controls. FOL was re-isolated from all inoculated cultivars but not from controls. The colony patterns of the recovered isolates were the same than those of the isolates used for inoculation. These results confirm that the isolate belongs to race 1. Greenhouse lettuce in Norway is mainly produced in hydroponics. FOL is here reported to cause damages in soil- grown lettuce. Nevertheless FOL in hydroponic systems has been reported in Japan (Fujinaga et al. 2003) and Thailand (Thongkamngam and Jaenaksorn 2017). Thus, the possibility of infections in hydroponics remain a big concern for lettuce production in Norway.

Hydroponic Lettuce Cultivation Using Organic Nutrient Solution from Aerobic Digested Aquacultural Sludge

The aim of this study was to demonstrate how aquacultural sludge can be processed and utilized as an organic nutrient solution (ONS) for hydroponic lettuce production. By using a previous developed method, approximately 80% of the processed sludge was reclaimed as a clear, nutrient-rich solution. The performance of the recovered nutrient solution on lettuce growth was assessed in a nutrient film hydroponic system. The results were compared to the results obtained using a conventional nutrient solution (CNS). Yield, fresh weight, water consumption, and nutrient and heavy metal content in leaf tissue were measured. In spite of a 16% lower average fresh weight obtained in ONS compared to the weight obtained in CNS, there was no statistical difference of the yield of lettuce among the two nutrient solutions. After the cultivation period, 90% of the lettuce heads grown in ONS exceeded the marked weight of 150 g. Foliar analysis revealed a similar or higher content of all nutrients, except of magnesium and molybdenum in the leaves of lettuce grown in the ONS compared to lettuce grown in the CNS. This study shows that nutrients recovered from aquacultural sludge can be utilized as fertilizer, thereby reducing the dependency on mineral fertilizer in hydroponic and aquaponic systems.

Nutrient Solution Deprivation as a Tool to Improve Hydroponics Sustainability: Yield, Physiological, and Qualitative Response of Lettuce

Hydroponics growing systems often contain excessive nutrients (especially nitrates), which could lead to a quality loss in ready-to-eat leafy vegetables and posing a health risk to consumers, if managed inadequately. A floating raft system was adopted to assay the production and quality performance of lettuce (Lactuca sativa L. cv ‘Maravilla De Verano Canasta’) deprived of the nutrient solution by replacement with only water, three and six days before harvest. Yield and quality parameters, mineral composition, pigments, organic acids, amino acids profile, soluble proteins, and carbohydrate content were determined. Nutrient solution deprivation six days before harvest resulted in a significant reduction in leaf nitrate (−53.3%) concomitant with 13.8% of yield loss, while plants deprived of nutrient solution three days before harvest increased total phenols content (32.5%) and total ascorbic acid (102.1%), antioxidant activity (82.7%), anthocyanins (7.9%), sucrose (38.9%), starch (19.5%), and γ-aminobutyric acid (GABA; 28.2%), with a yield reduction of 4.7%, compared to the control. Our results suggest that nutrient solution deprivation three days before harvest is a successful strategy to reduce nitrate content and increase the nutritional quality of lettuce grown in floating raft systems with negligible impact on yield. These promising results warrant further investigation of the potential effect of nutrient solution deprivation on the quality attributes of other leafy vegetables cultivated in floating raft systems and in a “cascade” growing system.

Photo-selective shading screens as a cover for production of purple lettuce

Photo-selective shading screens are emerging practices that aim to combine crop physical protection with different solar radiation filtration to achieve desired physiological responses. The objective of the present study was to evaluate the effect of photo-selective shading screens on the growth and physiology of purple lettuce for two transplanting seasons in tropical climate in Brazil. A 2 × 4 factorial arrangement was used, being considered the first factor, the transplanting season (spring and fall), and the second factor is the three 35% shading photo-selective shading screens (red, black and silver) and full sun control. The experimental design was a randomized complete block with four replications. The variables studied were: total fresh matter, total dry matter, leaf number, stem diameter, stem length, leaf area, SPAD chlorophyll index, nitrogen balance indexes, chlorophyll, flavonoids and anthocyanins. The photo-selective shading screens influenced the microclimate and the growth variables of purple lettuce, mainly when these plants were sown in the fall. Planting lettuce during spring may result in lower yields due to the higher investment of plants in secondary metabolites to defend against abiotic stress. According to the results, photo-selective shading screens are an appropriate agronomic technique to reduce phenolic compounds and improve lettuce cultivation conditions and can be implemented within protected cultivation practices to improve crop performance.

Integrated Metagenomic Assessment of Multiple Pre-harvest Control Points on Lettuce Resistomes at Field-Scale.

An integrated understanding of factors influencing the occurrence, distribution, and fate of antibiotic resistance genes (ARGs) in vegetable production systems is needed to inform the design and development of strategies for mitigating the potential for antibiotic resistance propagation in the food chain. The goal of the present study was to holistically track antibiotic resistance and associated microbiomes at three distinct pre-harvest control points in an agroecosystem in order to identify the potential impacts of key agricultural management strategies. Samples were collected over the course of a single growing season (67 days) from field-scale plots amended with various organic and inorganic amendments at agronomic rates. Dairy-derived manure and compost amendment samples (n = 14), soil samples (n = 27), and lettuce samples (n = 12) were analyzed via shotgun metagenomics to assess multiple pre-harvest factors as hypothetical control points that shape lettuce resistomes. Pre-harvest factors of interest included manure collection during/post antibiotic use, manure composting, and soil amended with organic (stockpiled manure/compost) versus chemical fertilizer. Microbial community resistome and taxonomic compositions were unique from amendment to soil to lettuce surface according to dissimilarity analysis. The highest resistome alpha diversity (i.e., unique ARGs, n = 642) was detected in amendment samples prior to soil application, while the composted manure had the lowest total ARG relative abundance (i.e., 16S rRNA gene-normalized). Regardless of amendment type, soils acted as an apparent ecological buffer, i.e., soil resistome and taxonomic profiles returned to background conditions 67 d-post amendment application. Effects of amendment conditions surprisingly re-emerged in lettuce phyllosphere resistomes, with the highest total ARG relative abundances recovered on the surface of lettuce plants grown in organically-fertilized soils (i.e., compost- and manure-amended soils). Co-occurrence analysis identified 55 unique ARGs found both in the soil amendments and on lettuce surfaces. Among these, arnA and pmrF were the most abundant ARGs co-occurring with mobile genetic elements (MGE). Other prominent ARG-MGE co-occurrences throughout this pre-harvest lettuce production chain included: TetM to transposon (Clostridiodies difficile) in the manure amendment and TriC to plasmid (Ralstonia solanacearum) on the lettuce surfaces. This suggests that, even with imposing manure management and post-amendment wait periods in agricultural systems, ARGs originating from manure can still be found on crop surfaces. This study demonstrates a comprehensive approach to identifying key control points for the propagation of ARGs in vegetable production systems, identifying potential ARG-MGE combinations that could inform future surveillance. The findings suggest that additional pre-harvest and potentially post-harvest interventions may be warranted to minimize risk of propagating antibiotic resistance in the food chain.

Optimizing fen peatland water‐table depth for romaine lettuce growth to reduce peat wastage under future climate warming

SummaryForty percentage of UK peatlands have been drained for agricultural use, which has caused serious peat wastage and associated greenhouse gas emissions (carbon dioxide (CO2) and methane (CH4)). In this study, we evaluated potential trade‐offs between water‐table management practices for minimizing peat wastage and greenhouse gas emissions, while seeking to sustain romaine lettuce production: one of the most economically relevant crop in the East Anglian Fenlands. In a controlled environment experiment, we measured lettuce yield, CO2, CH4 fluxes and dissolved organic carbon (DOC) released from an agricultural fen soil at two temperatures (ambient and +2°C) and three water‐table levels (−30 cm, −40 cm and −50 cm below the surface). We showed that increasing the water table from the currently used field level of −50 cm to −40 cm and −30 cm reduced CO2 emissions, did not affect CH4 fluxes, but significantly reduced yield and increased DOC leaching. Warming of 2°C increased both lettuce yield (fresh leaf biomass) and peat decomposition through the loss of carbon as CO2 and DOC. However, there was no difference in the dry leaf biomass between the intermediate (−40 cm) and the low (−50 cm) water table, suggesting that romaine lettuce grown at this higher water level should have similar energetic value as the crop cultivated at −50 cm, representing a possible compromise to decrease peat oxidation and maintain agricultural production.

Optimal control as a tool to investigate the profitability of a Chinese plant factory - lettuce production system

Although optimal control has been used extensively for greenhouse climate management, its application to plant factories is still in its infancy. In this paper, profitability of growing lettuce in a Chinese plant factory is investigated by means of optimal control computations. To that end, first, a lettuce growth model is adapted to fit a plant factory environment. Next, this model is calibrated and validated using nine sets of experimental data with different LED light intensities. Using the calibrated and validated model, optimal control computations are used to produce a 3D plot revealing the influence of the electricity and lettuce price on maximum profit. Lettuce's physiological demand for dark periods during artificial lighting is incorporated by fixing this dark period to eight hours a day. Therefore, the optimal LED light intensity pattern obtained from the optimal control computations could be used in the actual production process. Maximum profit can reach 264.88 RMB m −2 assuming a Chinese plant factory fresh lettuce price of 34.5 RMB kg −1 . When lettuce must be sold at 5.01 RMB kg −1 , which represents the price for an open field product, profit always comes out negative. Besides, LED lighting is not advised when the electricity price is greater than 0.84 RMB kWh −1 under these circumstances. Profit is only positive when the lettuce price is over 20 RMB kg −1 . • LED light intensity in a plant factory is optimised to compute profitability. • Dark periods for proper crop growth are implemented through a switching function. • The dynamic lettuce growth model was calibrated on 9 sets of experimental data. • Maximum profit is positive when the fresh lettuce price is over 20 RMB kg −1 . • The maximum profit is 264.88 RMB m −2 in the case of a Chinese plant factory.

Develop an automated monitoring system that allows the creation of an efficient hydroponic ecosystem, which increases the production of lettuce per square meter

The agricultural production methods of the last decades, have stood out for the use of the spaces, leaving aside even the land, mediating the greenhouses; in order to protect crops from climate variations, pests, raising their quality through better physicochemical characteristics and longer shelf life. The purpose of this work is to develop an automated system by means of materials such as sensors and microcontrollers capable of controlling physicochemical variables in a greenhouse, in order to provide the concentrations of nutrients, for the creation of an efficient hydroponic ecosystem, and standardized for an increase to production, in the cultivation of Romain variety lettuce. It is important to point out that within the hydroponic system, the Romain lettuce variety is harvested, obtaining larger products with an approximate weight of 1200 to 1500 g per piece, compared to those grown by the traditional method whose weights range between 1100 to 1300 g per piece, with a shelf life of 8 days in refrigeration.