Lettuce Crops Research Articles

An Energy-Efficient PAR-Based Horticultural Lighting System for Greenhouse Cultivation of Lettuce

This paper presents an intelligent horticulture lighting and monitoring system to achieve energy-efficient supplemental lighting while maintaining the light quality and intensity at desired levels in the photosynthesis spectrum. Energy-efficiency is achieved through delivering only the required net light intensity, consisting of sunlight and supplemental LED light, using an intelligent controller that does not depend on the lighting system model. To this end, an online neural-network learning control system is developed, comprised of low-cost light sensors for measuring the photosynthetic photon flux density (PPFD), dimmable LED light fixtures, cameras, and internet-of-things (IoT)-enabled firmware used for crop monitoring and performance evaluation. Experiments performed in a research greenhouse facility on the lettuce crop are presented which indicate that the system can deliver the desired Daily Light Integrals (DLIs) to the plants in the presence of changing daylight conditions. The proposed method can thus deliver the exact amount of light to a specific crop based on the required light recipes during different growth phases. The control performance is further compared with a conventional on-off time-scheduling method in terms of plant health, growth, and energy requirements. The experiments indicate that the proposed solution can reduce energy consumption per unit dry mass of lettuce by 28% when compared to existing time-scheduling methods.

Economic efficient use of soilless techniques to maximize benefits for farmers

<abstract> <p>The main challenge of the agricultural sector is the increasing pressure on natural resources, mainly water and arable land. Consequently, an urgent imperative arises to explore technological advancements that can boost food production in alignment with the growing demands. The Soilless Production System (SPS) emerges as a proficient approach for managing irrigation water, thereby making a significant contribution to food security. This research focuses on the efficient use of SPS and identifies the best economic use of the soilless techniques for different crops within an area characterized by limited land and water availability. The database for the study was generated through a farm survey to investigate the benefits of adopting SPSs as a sustainable agricultural practice. A linear programming approach was applied to develop an optimization model for resource allocation and crop mix selection, considering the development opportunities through the SPSs. Different scenarios were applied in the model. The results proved that adopting SPSs is a sustainable irrigation practice, since the technique promotes water use efficiency, generates profitability, and conserves the associated natural resources. The SPSs ensure sustainable use of water resources by increasing water use efficiency. The hydroponics cultivation system had 11 ± 1.7 times higher yields but required 82 ± 11 times more energy in comparison to the lettuce crop produced by the conventional production system (CPS). The result of the optimal solution shows that the total revenue of scenarios of the study is 109% of the revenue of the original value of the largest farmer. The water resources and the investment cost as constraints in the model are totally used, but the operational costs in the optimal solutions are 74% of the total operational cost in the original data. The optimal solution showed the importance of using computerized systems in which the control of the fertigation is better.</p> </abstract>

GREENBOX Technology I - Technical Feasibility and Performance in Warehouse Environment

Highlights There are pressures on food security due to increasing population, demand, and urbanization. GREENBOX uses controlled environment agriculture for urban crop production in warehouse settings. GREENBOX provided the required environmental conditions and comparable biomass output year-round. GREENBOX is technically feasible for urban crop production. Abstract. The surging worldwide population and urbanization have increased food security and safety pressures. Therefore, there is a need to increase food production capacity in urban areas to feed this growing population. We have developed the GREENBOX technology to grow vegetables in individual climate-controlled boxes in urban warehouse environments. A GREENBOX is a thermally insulated modular structure of standard size with an artificial lighting source, a hydroponic nutrient supply system, and environmental controls. GREENBOX units can be used together in various numbers to form different configurations and production capacities. This study was conducted to evaluate the technical feasibility and performance of the GREENBOX technology for urban crop production in warehouse settings commonly found in urban areas. Two model GREENBOX units, constructed with commercially available parts, were located in a high-ceiling headhouse of a laboratory greenhouse complex at Storrs, Connecticut, USA, for the study. Forty-eight (48) heads of Butterhead Rex lettuce (Lactuca sativa) were grown in the model GREENBOX units (24 in each) over a 30-day growing cycle for four seasons. Environmental data, including light, temperature, relative humidity, and carbon dioxide, were collected using iPonic sensors at a frequency of every minute and processed to 15-minute averages. Crop growth was quantified with biomass data, which were wet weight, dry weight, total leaf area, and lettuce head area, using destructive and non-destructive methods every three days. A lysimeter was used to determine the water consumption rate by plants every fifteen minutes. We derived the Daily Light Integral (DLI), Leaf Area Index (LAI), Specific Leaf Area (SLA), productivity, and water consumed per lettuce head, per unit wet weight, and per unit dry weight. Descriptive statistics were used to describe and analyze the results. The DLI in the GREENBOX ranged between 32.48-37.23 mol/m2.d at the lettuce heads' height, higher than the recommended minimum DLI of 6.5-9.7 mol/m2.d. GREENBOX does not rely on external light but solely on the artificial lighting source, regulated at the grower's discretion. The mean temperatures inside were 24.5-26.9°C, falling within the optimal range of 17-29°C for lettuce. The artificial lighting source was a heat source to sustain cultivation. All year, the average relative humidity was 35.53%-58.54%, mostly within the ideal range of 40%-60%. The CO2 concentration inside the boxes fell slightly below the ambient concentration of 350 ppm, between 301.39 and 311.34 ppm over different seasons. Measured growth parameters, including LAI (5.3-6.5 cm2/cm2), SLA (344.3-569.3 cm2/g), and productivity (6.33-7.38 kg/m2), all followed similar patterns, slightly different amongst seasons and higher in warmer seasons. GREENBOX used 1.83-2.69 liters of water per head of lettuce consistently year-round, 95% lower than soil-based irrigation. Lettuce plants were healthy and grew to full size in the 30-day cycle, regardless of the season. Our study showed that the GREENBOX technology was capable of providing desired environmental conditions for growing lettuce crops all year around in the experimental warehouse structure and consequently having a high potential to be applied in food production in mid-latitude urban settings. Keywords: Agricultural facility, Environmental control, GREENBOX, Lettuce, Urban agriculture.

Effects on Lettuce Yield Parameters and Toxicological Safety Assessment of a Plant-Derived Formulation Based on Rosemary and Eucalyptus Essential Oils

Essential oils from medicinal and aromatic plants are increasingly recognized as a promising class of green molecules for use in crop production. In many cases, the beneficial aspects of a substance are not supported by sufficient toxicological safety testing, even though recent reports suggest that some compounds may be toxic to terrestrial or aquatic non-target species. It is, therefore, essential to investigate the possibility of adverse effects on non-target animals and humans exposed to these substances through the consumption of fruit and/or vegetables. The present study aims to examine the potential effects on yield and quality parameters and investigate the level of in vitro and in vivo toxicity of an Eco-product (EP) based on rosemary and eucalyptus essential oils, to provide a measure for safe use in the agricultural sector. The product was evaluated in lettuce crop production and indicated that one-time application of the EP formula increases yield, activating various secondary metabolism pathways of the plant to cope with oxidative stress. Cytotoxicity assays and in vivo acute oral and dermal toxicity studies suggest that the tested compound does not pose any significant health hazard, and the dissolved product can be classified in Category 5, according to the Globally Harmonized System of Classification and Labelling of Chemicals (GHS).

Lettuce Fertigation with Domestic Effluent Treated with Orange Pomace Biochar

The objective of this study was to evaluate the adsorption capacity of orange pomace biochar, applying its benefits in irrigated agriculture. For this, a low-cost system for tertiary treatment using biochar was developed. The objective was also to compare the physicochemical and microbiological attributes of irrigation water with the limits established by the legislation. The impacts of wastewater from the filtration system on the soil and on the agronomic and biological characteristics of the lettuce crop were assessed. Biochar was produced in a muffle furnace and characterized by thermogravimetry and scanning electron microscopy (SEM). The experimental design was randomized blocks, in a 5 (irrigation depths) × 5 (combinations of water sources and fertilization) factorial arrangement, with three replicates. It was found that the use of biochar as a filter material improved the microbiological quality of wastewater. The water sources used in irrigation did not cause changes in soil salinity. Fertigation using wastewater that passed through the filtration system positively affected the agronomic characteristics of lettuce, with no need for top-dressing fertilization. Lettuce leaves produced in the experiment were acceptable for human consumption, according to the standards of Resolution-RDC No. 12, of 2 January 2001, of the National Health Surveillance Agency (ANVISA).

Plastome-based phylogeny and biogeography of Lactuca L. (Asteraceae) support revised lettuce gene pool categories.

This study generated and analyzed complete plastome and internal transcribed spacer (ITS) data of 46 Lactuca species, 13 African endemic (AE) Lactuca species, and 15 species from eight related genera in Lactucinae. The new plastome and nuclear ITS sequences were then used to reconstruct the phylogenetic relationships of Lactuca species. The whole-plastome data were used to estimate divergence time and ancestral area reconstruction of the identified major Lactuca lineages. The results showed that Lactuca species are generally similar in plastome size, Guanine and Cytosine (GC) content, gene structure, and categories, although crop lettuce (Lactuca sativa L.) and its gene pool relatives were found to have one unique pseudogene (ψ ndhF), and accD, atpF, cemA, clpP, and rpl22 showed signs of positive selection. Our phylogenomic analysis demonstrated that Lactuca is monophyletic after excluding Lactuca alatipes Collett and Hemsl and AE Lactuca species. AE Lactuca species are morphologically distinct from core Lactuca lineage and need to be excluded from Lactua. The core Lactuca species most likely originated from Asia-Temperate W ~6.82 Mya and then dispersed globally and formed nine clades. Finally, the lettuce gene pool concept was amended according to the phylogenetic and historical biogeographic analyses. This study revised the circumscription of Lactuca, revealed robust phylogenetic relationships within the genus, and provided insights into Lactucinae phylogeny. The lettuce gene pool species could be used as potential genetic resources for lettuce breeding.

Improving growing substrates by adding the seaweed Cystoseira baccata

We examined the impact of adding the seaweed Cystoseira baccata (Ochrophyta, Sargassaceae) in various forms to two different growing substrates: pine bark and gorse compost. Specifically, we examined the influence of the seaweed on the physical and chemical properties of the substrates, and on their agronomic performance on a lettuce crop. The seaweed was used in a 20% (v/v) proportion and three different forms, namely: fresh (FS), washed fresh (WFS), and washed and dried (WDS). The mixed substrates exhibited no signs of instability. FS and DWS increased the total water retention capacity of pine bark by 20% and 27%, respectively. Adding the seaweed in any of its three forms to this type of substrate, which is poor in nutrients and has a low electrical conductivity (EC), significantly increased its P, K, Mg and Na contents, as well as its EC (from 0.08 dS m–1 in the control substrate to 0.69, 0.12 and 0.27 dS m–1 in those containing FS, WFS and WDS, respectively). On the other hand, only in fresh form (FS) altered the salinity and total K content of a substrate rich in nutrients and salts such gorse compost (from 0.89 to 1.42 dS m−1 in terms of EC and 0.59% to 0.98% in K). All mixtures performed well as substrates for a lettuce crop. Those containing DWS increased aerial mass in gorse compost, while any of the tested formats increased aerial mass in pine bark.

Macronutrient cycling in hydroponic lettuce cultivation

In order to address issues of limited resources and contamination by fertilizers, nutrient solutions may be reused in hydroponics as an alternative to their disposal in the environment. This work evaluated the feasibility of nutrient replacement for the nutrient solutions reused during lettuce hydroponic cultivation. The experiment was carried out in an agricultural greenhouse in an NFT hydroponic system using the “Milena” lettuce cultivar. The experiment was divided into two stages: 1) monitoring and data collection and proposition of nutrient replacement management; and 2) validation of the proposed replacement management. Monitoring the consumption of the crop's nutritional solution in the first stage served as the basis for the proposed nutritional replacement management. Management was validated in the second stage through the evaluation of fresh and dry mass, crop nutritional status, and the amount of the fertilizer applied in the treatments: T1 - nutrient replacement with nutrient solution reuse; and T2 - nutrient replacement without nutrient solution reuse. The fresh and dry mass data and the amount of nutrients absorbed by the plants were submitted to the t-test at 5% probability, showing no significant difference between the treatments, making it possible to conclude that the nutrient solution reuse provided nutrient replacement during the lettuce crop cultivation.
 Keywords: hydroponic system, Lactuca sativa L., macronutrient rational use.

Effect of UV LED Intensity on The Growth of Red Lettuce in Indoor Hydroponics

Microclimate control is increasingly widespread in limited agricultural environments. This is especially important for the cultivation of plants that tolerate significantly different thermal and hygrometric conditions. Nevertheless, there is much to be done in automation and control technology in this area to achieve the best results in both quantitative and qualitative terms of the product. This applies especially to horticultural crops that are sensitive to the cultivation environment and microclimate. This work aims to characterize the microclimate parameters in a confined agricultural environment with perforated ducts for air conditioning supply. For this work, a microclimate control unit was used instead of a lettuce crop. It was placed into a confined agricultural environment at different locations in the space to obtain the main microclimate parameters. After setting the input of the microclimate environment, the instrument measured a series of physical quantities (temperature, radiant temperature, humidity, and air velocity). Tests were carried out by taking the optimum day temperature constant for growing lettuce and by varying the supply airflow rate by setting the fan speed at 30%, 50%, and 80%. The results of these tests are essential for performing real-time control of the microclimate environment and for managing parameters for optimization of the entire system. In addition, the air velocity test showed adequate velocity reduction and good air mixing. The values obtained are generally acceptable for indoor cultivation and the conditions created are suitable for growing plants in such an environment. Light is an essential need for plants so that plants can carry out the photosynthesis process properly. In indoor DWC hydroponics system, the source of UV light is LED lights for plants. Some of the advantages of using LED light include a small light spectrum, less heat production, low power consumption, and wavelengths of 660 m and 450 m that are needed by plants. This research project aims to create a DWC hydroponic system for growing red lettuce in an indoor hydroponics and see the effect of LED grow light on the growth of red lettuce. DWC hydroponics uses AB-Mix nutrients that are channeled through inch PVC pipes using pump power. The hydroponic rack used has a height of 1.7 m and a width of 40 cm and has 3 shelves, where each shelf has 9 nutrient containers. The red lettuce plants in the DWC system were provided with different light treatments by installing shading nets with different percentages of light penetration, namely, 75%, 50%, and 0%. From the results of these treatments, the average yield of red lettuce was 300 grams on the top shelf, 400 grams on the middle shelf, and 600 grams on the bottom shelf.

Using deep water culture as one of the important hydroponic systems for saving water, mineral fertilizers and improving the productivity of lettuce crop

Two experiments was carried out during for two successive seasons of 2020/2021 and 2021/2022 2021at the research farm of National Research Center (NRC) at Nubaryia Region, Al Buhayrah Governorate, Egypt., to Study of the performance of the deep water culture as one of the most important hydroponic systems in comparison with drip irrigation systems in open fields and under greenhouses on productivity, water productivity, fertilization productivity and some quality characteristics of lettuce. The experiment was arranged in a complete randomized block design with three replicates for each cultivar [two cultivars, CHE: CHEROKEE RZ (81-36) and AFI: AFICION RZ (81-82)] in each farming system [three farming systems, (Deep Water Culture (DWC) as hydroponic system, Drip Irrigation in Greenhouse (DIGH) with sandy soils, Drip Irrigation in Open Field (DIOF) with sandy soils)]. The study concluded that, by using the DWC, the vegetative growth characteristics were improved, productivity and water productivity increased, and the quality of the lettuce crop been improved.

ALFACE E RABANETE EM MONOCULTIVO E CONSÓRCIO SOB DIFERENTES LÂMINAS DE ÁGUA EM AMBIENTE PROTEGIDO

ABSTRACT Vegetables intercropping of results in a better use of natural resources, water, light, and nutrients, when properly managed. The objective of this work was to evaluate the performance of lettuce and radish in single crop and intercropping systems under different irrigation water depths. The experiment was conducted in a protected environment at the State University of Maringá, in Maringá, Paraná, Brazil. A randomized block experimental design was used in a 4×2 factorial arrangement, with four replications. The first factor consisted of four irrigation water depths (60%, 80%, 100%, and 120% ETc), and the second factor consisted of two crop systems (single crop and intercrop). A drip irrigation system was used, consisting of constant water table lysimeters. The variables evaluated were: shoot fresh weight, root dry weight, and leaf area for the lettuce crop; total fresh weight, root fresh weight, and root diameter for the radish crop; and yield, water use efficiency, and land use efficiency index for both crops. Shoot fresh weight, leaf area, and yield of lettuce, and total fresh weight, root fresh weight, and yield of radish increased as the irrigation water depth applied was increased. Total fresh weight, root fresh weight, root diameter, and yield of the radish crop were higher in the intercropping system. The water use efficiency of both crops was higher in the single crop, and the land use efficiency index was higher in the intercropping system.

SE-YOLOv5x: An Optimized Model Based on Transfer Learning and Visual Attention Mechanism for Identifying and Localizing Weeds and Vegetables

Weeds in the field affect the normal growth of lettuce crops by competing with them for resources such as water and sunlight. The increasing costs of weed management and limited herbicide choices are threatening the profitability, yield, and quality of lettuce. The application of intelligent weeding robots is an alternative to control intra-row weeds. The prerequisite for automatic weeding is accurate differentiation and rapid localization of different plants. In this study, a squeeze-and-excitation (SE) network combined with You Only Look Once v5 (SE-YOLOv5x) is proposed for weed-crop classification and lettuce localization in the field. Compared with models including classical support vector machines (SVM), YOLOv5x, single-shot multibox detector (SSD), and faster-RCNN, the SE-YOLOv5x exhibited the highest performance in weed and lettuce plant identifications, with precision, recall, mean average precision (mAP), and F1-score values of 97.6%, 95.6%, 97.1%, and 97.3%, respectively. Based on plant morphological characteristics, the SE-YOLOv5x model detected the location of lettuce stem emerging points in the field with an accuracy of 97.14%. This study demonstrates the capability of SE-YOLOv5x for the classification of lettuce and weeds and the localization of lettuce, which provides theoretical and technical support for automated weed control.

Assessing evapotranspiration in a lettuce crop with a two-source energy balance model

Assessing evapotranspiration in a lettuce crop with a two-source energy balance model

Chronic toxicity, bioavailability and bioaccumulation of Zn, Cu and Pb in Lactuca sativa exposed to waste from an abandoned gold mine

Abandoned mines with untreated waste cause environmental pollution. The complex mixture of mining waste includes high metal content, anthropogenic chemicals and sterile rocks. Adverse effects of contaminated soils have been widely assessed by the use of plants. The aim of this study was to assess the chronic toxicity of a contaminated soil by waste from an abandoned gold mine on Lactuca sativa and its relationship with the bioavailability and bioaccumulation of Zn, Cu and Pb. Soil samples were taken from the site of mining waste stacking and a reference site in La Planta (Argentina). Contamination indices were calculated and acute and chronic exposures on L. sativa were carried out. Phytotoxicity indices, morphological and biochemical parameters, and concentrations of Zn, Cu and Pb in pseudo total and bioavailable soil fractions and in plant tissue were determined. Concentration- and time-dependent toxicity effects were observed, especially on plant width, fresh aerial biomass, leaf area and percentage of plants with completely necrotic aerial biomass. High levels of Zn (1453.3 ± 220.3 μg g−1) were found in plant tissue compared to Pb (277.2 ± 18.0 μg g−1) and Cu (255.3 ± 25.6 μg g−1). Toxicological endpoints correlated with metal uptake and mining waste concentration. In addition, bioaccumulation factors correlated with mobilisable and water soluble fractions. The concentration of Pb in aerial biomass surpassed the permissible concentrations in leaf vegetables, even at the reference site, indicating that lettuce crop consumption could be risky for the local population's health. This study demonstrated a strong relationship between metal bioavailability, toxicity endpoints and bioaccumulation, contributing with novel information to future ecotoxicological risk assessments and remediation plans.

Validation of Recycled Nanofiltration and Anion-Exchange Membranes for the Treatment of Urban Wastewater for Crop Irrigation.

One of the alternative sources to tackle the problem of water shortage is the use of reclaimed water from wastewater treatment plants for irrigation purposes. However, when the wastewater has a high conductivity value, it becomes unusable for crop irrigation and needs a more specific treatment. In this work, recycled nanofiltration (rNF) membranes and anion-exchange membranes (rAEMs) obtained from end-of-life RO membranes were validated to evaluate their application capability in saline wastewater treatment. The use of recycled membranes may represent an advantage due to their lower cost and reduced environmental impact associated with their production, which integrates membrane-based technology into a circular economy model. Both recycled membranes were tested in crossflow filtration and electrodialysis (ED) systems. The results of the rNF membrane showed a high selective rejection of divalent ions (SO42− (>96%) and Ca2+ and Mg2+ (>93%)). In the case of the ED process, the comparison between rAEMs and commercial membranes showed an appropriate demineralization rate without compromising the power consumption. Finally, the quality of both system effluents was suitable for irrigation, which was compared to the WHO guideline and validated by the 7-week lettuce crop study.

Closed life-cycle aquaculture of sea lettuce (Ulva fenestrata): performance and biochemical profile differ in early developmental stages

Sea lettuce (Ulva) aquaculture has increased the last decade due to high productivity, wide environmental tolerance, and interesting functional and nutritional properties of the crop. Research focus has mainly been on adult biomass production, but knowledge of performance and biochemical content of early developmental stages – which are the basis to any large-scale production - is still limited. The life-history ofUlvaalternates between a diploid sporophytic life-stage and a haplontic gametophytic life-stage. Whereas the sporophyte give raise to recombinant gametophytes through zoids, gametophytes can give raise to parthenogenetically developing, clonal gametes in absence of a mating partner. This study shows that recombinant gametophytes have a faster ontogenetic development, higher growth rate, as well as higher protein, fatty acid, and pigment contents compared to clonal gametophytes of the cropUlva fenestrata. Nutrient addition is required for a normal development, but temperature and swarmer density have relatively small effects on the hatchery success, relative growth rate and biochemical profile of the juvenile biomass. Our study reveals that the selection of the life-history-phase in novel sea lettuce crop strains could largely contribute to the emerging seaweed aquaculture sector.

Reuse of post-culture mushroom substrate in horticultural seedbeds

The agronomic use of mushroom post-harvest substrates (SPCHs) in horticultural seedbeds could be an interesting alternative for the reuse of these wastes in line with the European circular economy strategy. This work evaluates the potential use of four treatments with different SPCHs, mushroom (-Ch), mushroom (-St), mushroom compost (-CO), and a mixture (SPCH-Ch and SPCH-St) as substrates for lettuce and chili pepper seed germination. The trial was carried out in a germination chamber using commercial compost as a control treatment. The evaluation was based on its chemical (salinity, N and C content), physical (bulk and real density, porosity and water retention) and plant effect (germination and biomass) characteristics. Of the chemical properties studied, the high salinity in SPCH-Ch and SPCH-CO was a limiting factor for the development of the horticultural species evaluated (electrical conductivity 1:2.5; p/v; ~11 dS m-1), and low germination percentages were observed. Regarding physical properties, porosity and water retention, the SPCH-CO, SPCH-St and mixture treatments presented some values outside the optimal range established for germination substrates. In the case of SPCH-St, its high C/N ratio could be a limitation for supplying N to the crop. In relation to biomass production (aerial and root) of lettuce and chili pepper, all the treatments evaluated obtained similar values to the control treatment. The mixed treatment presented the highest biomass values, significantly higher in the lettuce crop. In general, the mixed treatment proved to be the best alternative for use in the seedbed.

Combined Effect of Biochar and Fertilizers on Andean Highland Soils before and after Cropping

Although a number of works present biochar as a promising material for improving the quality of degraded soils, only a few show the effect of this material in soils from the Andean highlands. The objective of this work was twofold: (a) to study the effect of two types of biochars on two agricultural soils commonly found in the Andean highlands (Andisol and Inceptisol) and the corresponding soil–biochar–fertilizer interactions, and, (b) to assess the response to biochar of two vegetable crops (lettuce and radish) grown in succession in a simulated double-cropping system. Biochar was produced at 400 °C and 500 °C, for 1 h (B400 and B500, respectively), using hardwood residues. Properties of biochar that could potentially affect its interaction with soil and water (e.g., functional groups, surface area, elemental composition) were assessed. Experiments were conducted to test for main and interaction effects of biochar type, soil type, and the addition of NPK fertilizer on the soils’ characteristics. Bulk density and water content at field capacity and permanent wilting point were affected by two-way interactions between biochar and soil type. Biochar impacted bulk density and water retention capacity of soils. Higher available water content was found in soils amended with B400 than with B500, which is a consequence of the higher hydrophilicity of B400 compared to B500. After the lettuce crop was planted and harvested, the soil pH was unaffected by the biochar addition. However, after the second crop, the pH in the Inceptisol slightly decreased, whereas the opposite was detected in the Andisol. The CEC of the Inceptisol decreased (e.g., from 36.62 to 34.04 and from 41.16 to 39.11 in the control and in the Inceptisol amended with B400 only) and the CEC of the Andisol increased (e.g., from 74.25 to 90.41 in the control and from 79.61 to 90.80 in the Andisol amended with B400 only). Inceptisol amended only with biochar showed decrease of radish weight, while a large increase was found in B400 + fertilizer Inceptisol (i.e., from 22.9 g to 40.4 g). In Andisol, the weight of radish after the second crop increased in less proportion (i.e., from 43 g in the control to 59.7 g in the B400 + fertilizer Andisol), showing a visible positive impact of B400. The results suggest that biochar produced at 400 °C performs better than biochar produced at 500 °C because B400 apparently promotes a better environment for bacteria growth in the soils, as a consequence of more OH available groups in B400 and its better interaction with water and the fertilizer.

Sunflower Seed Husk as Promising By-Product for Soil Biodisinfestation Treatments and Fertility Improvement in Protected Lettuce Crop

One of the major challenges in biodisinfestation treatments against soilborne pathogens is the selection of the proper organic amendments and mixture features. The use of agro-industrial by-products is a sustainable alternative with proven efficacy, but the availability has to be considered in terms of location and quantity. Sunflower seed is one of the five major oil crops widely cultivated and the husk constitutes a significant part that is discarded. This by-product brings together the features to be considered an interesting organic amendment in agricultural soils because of its lignocellulose content, but no references have been found in this field. In this study, sunflower seed husk was used with fresh cow manure in biodisinfestation treatments, alone or combined with other by-products (rapeseed cake, beer bagasse and wheat bran). The assay was performed in summer in a commercial greenhouse with significant yield losses in lettuce crops caused by the root-knot nematode Meloidogyne incognita. Four different amendment mixtures were applied which included 3kg/m2 cow manure, as common waste, and 1 kg/m2 of by-products (dry weight), considering 6mgC/g soil in all treatments but different C/N ratio (23, 29, 31, 34) and by-products. Data was collected in three moments: (i) before and (ii) after biodisinfestation treatments and (iii) after harvesting the first crop after biodisinfestations. Crop damage was assessed through root galling index and the number of eggs in roots. The effects on the pathogen population and the whole soil nematode community were assessed along with some physicochemical and soil microbiological variables (respiration rate, microbial organic C, water-soluble organic C and physiological profile of heterotrophic bacteria through Biolog Ecoplates™). All treatments reported effectiveness in disease control without significant differences among them, but among times. However, soil temperatures during biodisinfestations were higher at higher C/N ratios and fertility variables also increased in these cases, mainly in the treatment with husk as the only by-product. Sunflower seed husk proved to be an interesting source of organic C to improve both biodisinfestation treatments and soil fertility in humid temperate climate zones.

Non-Invasive Monitoring of the Thermal and Morphometric Characteristics of Lettuce Grown in an Aeroponic System through Multispectral Image System

Aeroponics is a soilless cultivation technology integrating plant nutrition, physiology, ecological environment, agricultural automation and horticulture. One of the soilless advantages is that a non-invasive observation of the root system growth development is possible. This paper presents a vegetative growth evaluation of lettuce plants in an aeroponic chamber, where root and leaf development parameters were measured in three lettuce crops through plant images captured in the visible (VIS), near infrared (NIR) and far infrared (IR) spectra. A total of ninety lettuce plants was transplanted for this research, thirty for each experimental crop. The three lettuce crops were grown for thirty days in an aeroponic growth plant chamber inside a greenhouse under favorable conditions. The morphometric and thermal parameters of the lettuce roots (perimeter, area, length and average temperature) and leaves (perimeter, area and average temperature) were evaluated for each crop along ten image-capturing sessions through an implemented multispectral vision system. The average values of the root and leaf morphometric parameters obtained with the implemented imaging system along the lettuce growing period were statistically analyzed with Tukey testing. The obtained analysis results show no significant difference for a value of p ≤ 0.05 in 86.67%. Hence, the morphometric parameters can be used to characterize the vegetative lettuce growth in aeroponic crops. On the other hand, a correlation analysis was conducted between the thermal parameters computed with the root and leaf thermal image processing and the measured ambient temperature. The results were: R = 0.945 for correlation between ambient and leaf temperature, R = 0.963 for correlation between ambient and root temperature and R = 0.977 for leaf and root temperature. According to these results, the plant temperature is highly correlated with the ambient temperature in an aeroponic crop. The obtained study results suggest that multispectral image processing is a useful non-invasive tool to estimate the vegetative root and leaf growth parameters of aeroponic lettuce plants in a greenhouse.