Objective Resource waste and an environmental burden are consequences of improper disposal of horticultural waste, making it a significant concern in horticulture. Tomato plant residues that accumulate from tomato production in greenhouses, contain a lot of nutrients and organic matter. In the composting process, microorganisms decompose residues into nutrient rich substrates. If these were amended to arable land, this could save fertilizer and help to close nutrient cycles. Methods In the present study, it was investigated in a pot experiment whether compost from tomato residues is suitable as fertilizer and soil amendment to produce lettuce (Lactuca sativa 'Speedway'). Therefore, conventional organic fertilizer was substituted either by 100 % or 50 %. In addition, control treatments, with or without conventional organic fertilizer were cultivated. Results The results show that the addition of tomato plant compost increases water holding capacity, carbon content, pH, total amount of macro nutrients as well as available P, K and Mg, but reduces ammonium and nitrate content compared to the fertilized control. The 100 % substitute leads to reduced yield and water use efficiency. Therefore, using composted tomato plant residues as a sole N fertilizer is not efficient due to limited plant available N release. Yet, substituting 50 % of conventional organic fertilizer with composted tomato plant residues maintains yields while preserving the aforementioned positive effects. Conclusion We demonstrated that composted tomato plant residues are suitable as fertilizer and soil amendment. The residues from one hectare of tomato production have the potential to substitute 50 % of conventional fertilizer for lettuce production on one and the same hectare. This could effectively reduce waste, close nutrition cycles, and promote environmentally friendly horticulture.

This is the first study who presents an approach to predict secondary metabolites content in tomatoes using multivariate time series classification of greenhouse sensor data, which includes climatic conditions as well as photosynthesis and transpiration rates. The aim was to find the necessary conditions in a greenhouse to determine the maximum content of secondary metabolites, as higher levels in fruits can promote human health. For this, we defined multiple classification tasks and derived suitable classification function. Cross-validated high accuracy results demonstrate the effectiveness of the approach. Considering a period of three weeks, we found that PPFD levels between 396.0 μmol/m2s and 511.2 μmol/m2s as well as transpiration rates ranging from 4.4 mg H2O/m2s to 7.47 mg H2O/m2s were observed as optimal for the contents of beta carotene, lutein, and lycopene. Optimal contents for naringenin and phloretin diglucoside can be achieved at lower PPFD ranges from 229.4 μmol/m2s to 431.2 μmol/m2s and from 35.76 μmol/m2s to 262.28 μmol/m2s and at lower transpiration rates from 4.71 to 6.47 mg H2O/m2s and from 3.04 to 4.26 mg H2O/m2s, respectively. It was discovered for the first time that, photosynthesis rates also play a significant role in the accumulation of secondary metabolites. Photosynthesis rates between 0.39 μmol CO2/m2s and 1.21 μmol CO2/m2s over three weeks were crucial for the optimal accumulation of phenolic acids such as caffeic acid derivates, coumaric acid hexoside, ferulic acid hexoside and coumaroylquinic acids as well as for quercetin and flavonoid. An optimal temperature range between 20.94 and 21.53°C and a PPFD from 250.0 to 375.2 μmol/m2s was classified as beneficial to synthesize these compounds. Optimal light intensity for the total phenolic acids (129.35 - 274.34 μmol/m2s) and for the total flavonoids (31.24 - 249.31 μmol/m2s), the optimum relative humidity levels are between 83.45 - 91.29% and 87.13 - 91.29%, respectively. Based on these results, this study provides the first evidence that the impact of a single climate factor on secondary metabolites in tomato fruits should not be considered in isolation, but rather, all climatic factors during a growth period must be taken into account to predict the optimal accumulation of individual phenolic compounds and carotenoids in tomatoes. Our results have laid the headstone to help growers target their climate controls to maximize the health-promoting phytochemicals in tomatoes.

Controlled environment agriculture is a promising alternative to conventional production methods, as it is less affected by climate change and is often more sustainable, especially in circular and recycling frameworks such as aquaponics. A major cost factor in such facilities, however, is the need for skilled labor. Depending on available resources, there are endless possibilities on how to choose ingredients to realize a desired nutrient solution. At the same time, the composition of the desired solution is subject to fluctuations in fish water quality, fertilizer availability, weather, and plant development. In high-evaporation scenarios, e.g., summer, nutrient solutions might be mixed multiple times per day. This results in a complex, multi-variable task that is time-consuming to solve manually, yet requires frequent resolution. This work aims to help solve this challenge by providing methods to automate the nutrient mixing procedure. A simple mass-balance-based model of a nutrient mixing tank with connections to different water sources, drains, and fertilizers is provided. Using methods of static optimization, a program was developed which, in consideration of various process constraints and optimization variables, is able to calculate the necessary steps to mix the desired solution. The program code is provided in an open-source repository. The flexibility of the method is demonstrated in simulation scenarios. The program is easy to use and to adapt, and all necessary steps are explained in this paper. This work contributes to a higher automation level in CEA.

The authors would like to make the following corrections to the published paper [...]

Urban and peri- urban horticulture presents major challenges, such as low water and land availability for agricultural use. So far, there are no data on the amount of water needed for vegetable production in Mexico City (CDMX). Therefore, the objective of this study was to estimate the yield and water use efficiency of two representative crops in urban gardens, including romaine lettuce and cherry tomato, for 13 urban gardens in CDMX. In addition, the rainwater storage capacity was estimated using data from the closest weather station from each orchard, in order to make statements about the coverage of the water demand for the plants. Yield and water use efficiency for lettuce production ranged between 0.10 and 1.20 kg m(-2) as well as 0.21 to 2.93 kg m(-3) water, respectively. These indicators for the case of cherry tomato were between 0.25 and 3.40 kg m-2 and between 0.32 and 5.52 kg m(-3) water, respectively. Irrigation in the urban gardens was done in an empirical way and using fresh water. It was found, in most of the cases, an excess of water supply which can be up to 0.27 and 0.4 m(3) m(-2) for a complete growth season of lettuce and cherry tomato. The rainwater storage capacity in a year was estimated using an 80 % probability of exceedance. The accumulated rainwater storage varies from 0.261 to 0.5215 m(3) m(-2) in the orchards, which could supply the water requirements for a complete season of lettuce (0.128 to 0.389 m(3) m(-2)) or cherry tomato (0.145 to 0.569 m(3) m(-2)).

Source-separated, nitrified, and decontaminated human urine constitutes a promising plant fertilizer that contains a large share of the nitrogen and phosphorus in household wastewater, and other plant nutrients. However, human urine contains high levels of sodium and chloride that can affect salt-sensitive greenhouse crops. Replacing mineral fertilizer with nitrified urine fertilizer could reduce the environmental impact of lettuce production in hydroponic systems, if marketable yield, appearance, and produce quality are not affected. In the present study, a treatment combination of a nitrified urine fertilizer and mineral fertilizers was used to grow lettuce through the nutrient film technique. This was compared to a conventionally fertilized control treatment. No significant differences were observed regarding yield, phenotype, and contents of nitrate, heavy metals, phenolic acids, and chlorophyll in leaf tissue. Calcium content was significantly reduced and sodium was elevated in nitrified urine treatment. For the elements nitrogen, phosphorous, and potassium, a saving of 48%, 13%, and 15% was calculated, respectively. The calculated carbon footprint from the total fertilizer production was reduced by 34.25%, caused by the nitrified urine treatment. Based on these results, a nutrient solution composed of nitrified urine fertilizer combined with mineral fertilizer may be a promising alternative for growers to produce lettuce with a reduced environmental impact without loss of plant quantity and quality.

Vegetables cultivated in cities, carry the risk of absorbing pollutants generated by anthropogenic activities, increasing the health risk of those who consume them. Heavy metal concentrations (As, Cd, Cr, Ni and Pb) were analyzed in water, soil and in plant parts of lettuce (roots and leaves) and cherry tomatoes (roots, stem, leaves and tomato fruit) lettuce and cherry tomatoes, cultivated in urban gardens in Mexico City. In none of the studied sites was the heavy metal concentration in the soil above the permitted limits. In irrigation water, Cr surpassed the permitted limit in 5 sites and that of Cd in one site. Ni surpassed the established limit for lettuce and cherry tomato in the rank among 0.7 and 31.15 mg kg -1 in 9 sites, Cr exceeded the allowed limits 1.45-38 mg kg -1 in 11 sites, As go beyond the established limits between 5-52 mg kg -1 in 4 sites and to a lesser extent, Pb was above the allowed limits between 15.5 and 26 mg kg -1 . According to the translocation factor, lettuce and cherry tomato could be an important phytoextractors of Cr and Cd respectively. The compound risk value for lettuce ( TTHQ ) was greater than one in three sites for lettuce and five sites for cherry tomato. Also, in gardens A, D, E and J, the Hazard Index ( HI ) showed a potential risk ( HI >1), which reveals the danger of consuming both vegetables given the conditions of soil, water and air and taking into account all paths of exposure.

La horticultura urbana y periurbana (HUP) presenta grandes desafíos, como la poca disponibilidad en el suministro del agua y de tierra. No existen datos sobre la cantidad de agua que se utiliza para la producción de hortalizas en la Ciudad de México (CDMX). Por lo tanto, el objetivo del presente estudio fue la estimación de los rendimientos y la productividad del agua para dos hortalizas representativas en jardines urbanos: lechuga romana y tomate cherry en 13 huertos urbanos de la CDMX. Asimismo, se estimó el volumen de agua de lluvia que se puede almacenar en cada huerto, utilizando la estación meteorológica más cercana. El rendimiento y la eficiencia del uso del agua para la producción de lechuga oscilaron entre 0.10 y 1.20 kg m-2, así como de 0.21 a 2.93 kg m-3 de agua, respectivamente. Estos indicadores, para el caso de tomate cherry, estuvieron entre 0.25 y 3.40 kg m-2 y entre 0.32 y 5.52 kg m-3 de agua, respectivamente. El riego en los huertos se hace de manera empírica y utilizando agua potable; el exceso en el suministro de agua puede ir de 0.27 a 0.4 m3 m-2 para un ciclo completo de lechuga y tomate cherry, respectivamente. Utilizando una probabilidad de excedencia del 80 %, se estimó la captación de agua de lluvia para todo el año, generando un almacenamiento acumulado entre 0.261 y 0.5215 m3 m-2 en los huertos urbanos. Esta cantidad de agua podría suplir los requerimientos hídricos de lechuga (de 0.128 a 0.389 m3 m-2) o tomate cherry (de 0.145 a 0.569 m3 m-2) para un ciclo completo.

Shortage of water availability and awareness of the need for sustainable resource management have generated a significant increase in the use of recycled water for irrigation and processing of crops and harvest products, respectively. As a result, irrigation systems face the challenge of neutralizing plant pathogens to reduce the risk of their dispersal and the subsequent occurrence of diseases with potentially high economic impacts. We evaluated the efficacy of an innovative electrolytic disinfection system based on potassium hypochlorite (KCLO) to inactivate major pathogens in hydroponically grown tomatoes: Fusarium oxysporum (Synder and Hans), Rizocthonia solani (Kühn), Tobacco mosaic virus (TMV) and Pepino mosaic virus (PepMV). The electrolytically derived disinfectant was prepared on-site and added to the recirculating fertigation solution once a week for 60 min in an automated manner using sensor technology at a dosage of 0.5 mg of free chlorine/L (fertigation solution at pH 6.0 ± 0.3 and ORP 780 ± 31 mV). Tomato fruit yield and pathogen dispersal were determined for 16 weeks. At the applied dosage, the disinfectant has been shown to inhibit the spread of plant pathogenic fungi and, remarkably, plant viruses in recirculating fertigation solutions. Phytotoxic effects did not occur.

The automotive industry is evolving rapidly with increasingly rigorous emission targets and leaps toward electrification and autonomous driving. These forces continue to trigger lightweight solutions, advancing the adoption of novel composite materials for diverse applications. Composite materials have been used for body parts in sports and luxury vehicles for a long time, enabling design freedom, astonishing aesthetics and leading-edge driving performance. This extended abstract discusses state of the art composite manufacturing processes enabling cost-efficient high-quality parts 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.

Light emitting diodes (LEDs) are an energy efficient alternative to high-pressure sodium (HPS) lighting in tomato cultivation. In the past years, we have learned a lot about the effect of red and blue LEDs on plant growth and yield of tomatoes. From previous studies, we know that plants absorb and utilize most of the visible spectrum for photosynthesis. This part of the spectrum is referred to as the photosynthetically active radiation (PAR). We designed a LED fixture with an emission spectrum that partially matches the range of 400 to 700 nm and thus partially covers the absorption spectrum of photosynthetic pigments in tomato leaves. Tomato plants grown under this fixture were significantly taller and produced a higher fruit yield (14%) than plants grown under HPS lighting. There was no difference in the number of leaves and trusses, leaf area, stem diameter, the electron transport rate, and the normalized difference vegetation index. Lycopene and lutein contents in tomatoes were 18% and 142% higher when they were exposed to the LED fixture. However, the ß-carotene content was not different between the light treatments. Transpiration rate under LED was significantly lower (40%), while the light use efficiency (LUE) was significantly higher (19%) compared to HPS lighting. These data show that an LED fixture with an emission spectrum covering the entire PAR range can improve LUE, yields, and content of secondary metabolites in tomatoes compared to HPS lighting.

Concepts of semi-closed greenhouses can be used to save energy, whereas their technical equipment often causes a decrease in the light received by the plants. Nevertheless, higher yields are achieved, which are presumably triggered by a higher CO2 concentration in the greenhouse and associated higher photosynthesis because of the technical cooling and the longer period of closed ventilation. Therefore, we examined the effects of photosynthetic photon flux density (PPFD) and CO2 concentration on plant photosynthesis and transpiration in tomato using a multiple cuvette gas exchange system. In a growth chamber experiment, we demonstrated that a light-mediated reduction in photosynthesis can be compensated or even overcompensated for by rising CO2 concentration. Increasing the CO2 concentration from 400 to 1000 µmol mol−1 within the PPFD range from 303 to 653 µmol m−2 s−1 resulted in an increase in net photosynthesis of 51%, a decrease in transpiration of 5 to 8%, and an increase in photosynthetic water use efficiency of 60%. Estimations showed that light reductions of 10% can be compensated for via increasing the CO2 concentration by about 100 µmol mol−1 and overcompensated for by about 40% if CO2 concentration is kept at 1000 instead of 400 µmol mol−1.

This work presents an adaptive architecture that performs online learning and faces catastrophic forgetting issues by means of an episodic memory system and of prediction-error driven memory consolidation. In line with evidence from brain sciences, memories are retained depending on their congruence with the prior knowledge stored in the system. In this work, congruence is estimated in terms of prediction error resulting from a deep neural model. The proposed AI system is transferred onto an innovative application in the horticulture industry: the learning and transfer of greenhouse models. This work presents models trained on data recorded from research facilities and transferred to a production greenhouse.

Combining information of plant physiological processes with climate control systems can improve control accuracy in controlled environments as greenhouses and plant factories. Through that, resource optimization can be achieved. To predict the plant physiological processes and implement them in control actions of interest, a reliable monitoring system and a capable control system are needed. In this paper, we focused on the option to use real-time crop monitoring for precision climate control in greenhouses. For that, we studied the processes and external factors influencing leaf net CO2 assimilation rate (AL , µmol CO2 m-2 s-1) as possible variables of a plant performance indicator. While measured greenhouse environmental variables such as light, temperature, or humidity showed a direct relation between AL and light-quantum yield of photosystem II (Φ2), we defined three objectives: (1) to explore the relationship between climate variables and AL , as well as Φ2; (2) create a simple and reliable method for real-time prediction of AL with continuously Φ2 measurements; and (3) calibrate parameters to predict chloroplast electron transport rate as input in AL modelling. Due to practical obstacles in measuring CO2 gas-exchange in commercial production, we explored a method to predict AL by measuring Φ2 of leaves in a commercial hydroponic greenhouse tomato crop ("Pureza"). We calculated AL with two different approaches based on either the negative exponential response model with simplified biochemical equations (marked as Model I) or the non-rectangular hyperbola full biochemical photosynthetic models (marked as Model II). Using Model I can only be used to predict AL with large uncertainty (R2 0.64; RMSE 2.21), while using Φ2 as input to Model II could be used to improve the prediction accuracy of AL (R2 0.71; RMSE 1.98). Our results suggests that (1) Φ2 light signals can be used to predict net photosynthesis rate with high accuracy; (2) a parameterized photosynthetic electron transport rate model is suitable predicting measured electron transport rate (J) and AL . The system can be used as decision support system (DSS) for plant and crop performance monitoring when leaf-dynamics are up-scaled to the plant or crop level.

Short- and long-term phenotypic changes of hydroponically grown tomatoes as a result of seedling production substrates were examined. As such, plants were grown for two weeks in three different seedling production substrates: horticultural growing medium on peat basis, perlite, and a 1:1 mixture of peat-perlite, before they were transplanted into a rockwool based hydroponic system. Germination of plants in the perlite treatment resulted in significantly smaller leaves, lower stem diameter and a delayed start of harvesting compared to the other treatments, while no differences in the amount of marketable tomatoes were observed at the end of experiments. The perlite treatment yielded fewer small and blossom end rot fruits. Applying Lichtenthaler's index and the normalized difference vegetation index showed lower chlorophyll concentrations in the leaves of the perlite treatment. The car-ratio index revealed a tighter ratio of carotenoid to chlorophyll in the perlite treatment implying some kind of stress. Due to the absent influence of smaller leaves and assumed lower chlorophyll concentration on yield, a higher photosynthetic radiation use efficiency (PRUE) was expected. Applying the photochemical reflectance index, which is correlated to the PRUE, could not support this hypothesis. Reflectance indices calculated for the optical properties of fruits did not suggest any differences in fruit pigmentation. It is therefore possible to save a portion of the finite resource peat by using perlite as seedling production substrate without worrying about loss of yield and fruit pigmentation.

Due to root respiration, a minimum oxygen concentration in the root zone of plants is necessary. To keep the plant healthy and fully efficient the concentration should not fall below a plant specific critical value. Especially in nutrient film technique, the oxygen concentration can deplete heavily during the daytime. Besides the root respiration also microorganisms, living in the root zone of the plants, consume oxygen and have to be considered. In double recirculating aquaponic systems (DRAPS) fish waste water is used for preparation of nutrient solution for plant production in hydroponics. The fish waste water, delivered by a recirculating aquaculture system (RAS), probably contains high amounts of microorganism which can compete with plants for oxygen. The present study was conducted to investigate the oxygen concentration of nutrient solutions used in both, conventional hydroponics and in DRAPS, respectively. Therefore, the oxygen concentration within the cultivation trenches of conventional hydroponics (control; nutrient solution prepared with fresh water, electrical conductivity (EC) 1.8 dS m(-1)) and DRAPS (nutrient solution prepared with fish waste water (AP), EC 1.8 dS m(-1) (low) and EC 3.0 dS m(-1) (high)) were investigated. To evaluate whether the differences in oxygen depletion might be almost due to the used process water, the oxygen consumption of the prepared nutrient solutions was investigated separately without plants. The oxygen concentration within the cultivation trenches followed a typical daily fluctuation pattern with a decreasing oxygen concentration during the day. As time passed from April to June the depletion during the day increased and was strongest in AP high. In June the oxygen concentration dropped partly to zero in AP high, while it dropped only to nearly 150 mu mol L-1 and 60 mu mol L-1 in control and AP low, respectively. The oxygen consumption of pure nutrient solution (without plants) was significantly different between AP high and control, which also affects the oxygen concentration within the cultivation trenches.

Closed fertilisation systems improve the water use efficiency of greenhouse crop production, which reduces groundwater pollution considerably. However, the uptake ratio of water and the individual nutrients is not constant over the cultivation period of most crops. This may result in ion imbalances in the nutrient solution if the composition of the supply solution is not adequately adapted to the growth stage of the crop and the growing conditions. To overcome this, it is necessary to develop an ionspecific nutrition control system. The optimal composition of the supply solution can be estimated based on models of the plant's water and nutrient uptake depending on the stage of its phenological development and environmental conditions. Ion-specific sensors can then measure the composition of the drainage solution online and use it as feedback control. In an initial trial, the research team varied the total concentration of nutrients expressed as electrical conductivity (EC) depending on the climate in the greenhouse. This strategy was compared to the supply of nutrient solution of a constant EC of 3 dS m(-1), as this level is often used in horticultural practice. Tomato cultivar `Pannovy' was grown in rock wool slabs in a greenhouse with ten closed nutrient cycles at Grossbeeren from April 22 to August 24, 2015. Ion-specific sensors measured the nutrient composition of the drainage solution online. Additionally, laboratory measurements were carried out every 14 days to determine the nutrient composition of the supply and drainage solution. The climate-driven adjustment of the EC in the nutrient solution supplied to the plants resulted in a more stable and on average lower EC in the drainage solution compared to the supply of solution at a constant EC of 3 dS m-1. During a harvest period of 10 weeks, the model-based treatment provided a 30% higher yield and a lower fraction of fruit with blossom-end rot compared to a constant EC.

The research was focused on the identification of interactions between hypochlorite used as a disinfectant for a recirculating tomato production system and the spread of microorganisms, plant characteristics and fruit quality. Potassium hypochlorite (1% KCLO) supplemented once a week for 90 min into different nutrient solution ranks until a free chlorine concentration of 1 mg L-1 (DI) and 2 mg L-1 (DII) caused benefits but also hazards. Results showed that microorganisms were suppressed by up to 100%. Plants exposed to treatment DI showed a comparable plant height in comparison to control plants, whereas this plant parameter was significantly increased by 12 cm caused by treatment DII after a growing period of seven weeks. However, the formation of leaves was more pronounced by treatment DI. This was obviously the main reason for an increase in yield by 10% (DI) calculated in comparison to control plants. While phytotoxic problems can be excluded, the chlorate (ClO3-) content in tomatoes increased from 0.01 mg (control) to 0.22 mg (DI) and 0.25 mg (DII) ClO3- kg(-1) fresh weight. This enhancement should be seen as critical value because new maximum residue levels (MRL) will be defined next year. The levels of lycopene increased with increasing concentrations of hypochlorite as well, which was probably based on a stress response owing to the accumulation of chlorate. Apart from the ClO3- accumulations in fruit, treatment DI represents the most promising disinfection for recirculating tomato production systems.

Aquaponics combine the production of fish and plants in a sustainable way due to the double use of water and nutrients. Compared to conventional single recirculation aquaponic systems (SRAPS), the double recirculation aquaponic systems (DRAPS) are improved by the combination of two separate recirculating systems: the recirculating aquaculture system (RAS) for fish rearing and a closed hydroponic cycle for plant production. Both systems are connected in one direction to transfer the nutrient rich fish waste water to the hydroponic unit. The unidirectional connection of both systems allows the optimisation of fish waste water for plant growth by addition of mineral fertilizer without negative effects on fish rearing. DRAPS is a relative new approach and information about the functionality and successful use are rare. Therefore, more research on DRAPS is necessary. The present study was focused on different growth and production parameters of tomatoes produced in DRAPS compared to those produced in conventional hydroponics. Investigations during an annual production in 2015 showed that tomatoes produced in DRAPS have a comparable plant growth and development as obtained for conventional hydroponics. Even the fruit quantity and the fruit quality, including nutrient contents, were similar in both production systems.