Development of a CFD crop submodel for simulating microclimate and transpiration of ornamental plants grown in a greenhouse under water restriction

International audiencePredictive models of soil-plant-atmosphere water transfers may be helpful to better manage water inputs to plants in greenhouses. In particular, Computational Fluid Dynamics appears to be a powerful tool to describe the greenhouse microclimate and plant behavior. Up until now, most models for potted plants grown in greenhouses were established for well-watered conditions. In this context, the aim of this work is to develop a specific submodel to simulate the distributed transpiration and microclimate during plants grown in pots inside greenhouses under water restriction conditions. A 2D transient CFD (Computational Fluid Dynamics) model was implemented and user-defined functions were adapted to take account of the crop interactions with the climate inside the greenhouse. The crop was considered as a porous medium and specific source terms for transpiration and sensible heat transfers were added. A specific submodel was also implemented to calculate the substrate water content based on the water balance between irrigation and transpiration. Particular care was paid to the modeling of stomatal resistance. In order to obtain the input data and to validate the CFD simulations, an experiment was conducted over 16weeks inside a greenhouse equipped with New Guinea impatiens ornamental plants grown in containers on shelves. Both well-watered and restriction conditions were analyzed. The results of the CFD simulations showed the ability of the model to correctly predict transpiration, air and leaf temperatures as well as air humidity inside the greenhouse for both water regimes. Different irrigation scenarios were then tested, progressively reducing the water supply by providing a lesser amount of water than the growing media water capacity. The simulations made it possible to assess the model response to different irrigation regimes on plant transpiration, usual growing media water potential and climate distribution inside the greenhouse. The tests also showed that the water supply could be reduced by 20% without significantly impacting the transpiration rate and, therefore, potential plant growth. The CFD model could thus be useful to test different irrigation scenarios and better manage water inputs

Computational fluid dynamics modeling of crop-microclimate interaction for plants under water restriction inside a greenhouse compartment.

International audienceIncreasing water-use efficiency in greenhouses is a way of reducing water inputs. To this end, better understanding and quantifying the crop sensible and latent heat exchanges in response to water restriction conditions could be helpful. This may be reached by using predictive models of water transfers in the soil-plant-atmosphere continuum. To date, most models for plants grown in greenhouses have been established for well-watered conditions. Following previous work undertaken on a scale restricted to the canopy and its close environment, the aim of this work was to simulate transpiration and microclimate for plants grown in pots on the scale of a greenhouse compartment for different irrigation regimes. To this end, a two-dimensional transient computational fluid dynamics (CFD) model was implemented. A specific routine was developed to include the resistance to air flow exerted by the crop, together with the sensible and latent heat exchanges with the ambient air. The routine uses the stomatal resistance, which depends on the substrate matric potential. This last parameter was inferred from the water content calculated from a water balance over the pot. Boundary conditions were established from experimental data collected inside a greenhouse compartment equipped with ornamental plants (New Guinea impatiens) grown in containers on shelves. Both well-watered and restriction conditions were analyzed. The results of the CFD simulations showed the ability of the model to correctly predict transpiration and air and leaf temperatures as well as air humidity inside the greenhouse for both water conditions. The CFD model could therefore be useful to test different irrigation scenarios and better manage water inputs

Computational fluid dynamics modelling of crop-microclimate interactions for plants under water restriction inside a greenhouse compartment

International audienceIncreasing water-use efficiency in greenhouses is a way of reducing water inputs. To this end, better understanding and quantifying the crop sensible and latent heat exchanges in response to water restriction conditions could be helpful. This may be reached by using predictive models of water transfers in the soil-plant-atmosphere continuum. To date, most models for plants grown in greenhouses have been established for well-watered conditions. Following previous work undertaken on a scale restricted to the canopy and its close environment, the aim of this work was to simulate transpiration and microclimate for plants grown in pots on the scale of a greenhouse compartment for different irrigation regimes. To this end, a two-dimensional transient computational fluid dynamics (CFD) model was implemented. A specific routine was developed to include the resistance to air flow exerted by the crop, together with the sensible and latent heat exchanges with the ambient air. The routine uses the stomatal resistance, which depends on the substrate matric potential. This last parameter was inferred from the water content calculated from a water balance over the pot. Boundary conditions were established from experimental data collected inside a greenhouse compartment equipped with ornamental plants (New Guinea impatiens) grown in containers on shelves. Both well-watered and restriction conditions were analyzed. The results of the CFD simulations showed the ability of the model to correctly predict transpiration and air and leaf temperatures as well as air humidity inside the greenhouse for both water conditions. The CFD model could therefore be useful to test different irrigation scenarios and better manage water inputs

Effects of prolonged water restriction on plant interactions with their environment – the case of potted ornamental crops grown in greenhouses

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Computational fluid dynamics modeling of crop-microclimate interaction for plants under water restriction inside a greenhouse compartment.

International audienceIncreasing water-use efficiency in greenhouses is a way of reducing water inputs. To this end, better understanding and quantifying the crop sensible and latent heat exchanges in response to water restriction conditions could be helpful. This may be reached by using predictive models of water transfers in the soil-plant-atmosphere continuum. To date, most models for plants grown in greenhouses have been established for well-watered conditions. Following previous work undertaken on a scale restricted to the canopy and its close environment, the aim of this work was to simulate transpiration and microclimate for plants grown in pots on the scale of a greenhouse compartment for different irrigation regimes. To this end, a two-dimensional transient computational fluid dynamics (CFD) model was implemented. A specific routine was developed to include the resistance to air flow exerted by the crop, together with the sensible and latent heat exchanges with the ambient air. The routine uses the stomatal resistance, which depends on the substrate matric potential. This last parameter was inferred from the water content calculated from a water balance over the pot. Boundary conditions were established from experimental data collected inside a greenhouse compartment equipped with ornamental plants (New Guinea impatiens) grown in containers on shelves. Both well-watered and restriction conditions were analyzed. The results of the CFD simulations showed the ability of the model to correctly predict transpiration and air and leaf temperatures as well as air humidity inside the greenhouse for both water conditions. The CFD model could therefore be useful to test different irrigation scenarios and better manage water inputs

Effects of prolonged water restriction on plant interactions with their environment – case of potted ornamental crops grown in greenhouses.

International audienceIn greenhouses, reducing water consumption by increasing water efficiency is of great interest in order to limit the environmental footprint of cultivation and reduce costs. However, satisfactory irrigation is needed to get plants of a good quality. When reducing water inputs, if the quality decreases because of visible physical adaptations, these are coupled to physiological adaptations that limit water losses by transpiration. Understanding these adaptations is therefore required in order to model and thus forecast plant transpiration in the scope of precision horticulture. For this purpose, an experiment was conducted to understand the effect of prolonged restricted irrigation on potted New Guinea impatiens. Plants were grown inside a 100-m2 greenhouse compartment. They were distributed on four shelves, irrigated with different amounts of water from 6 weeks after repotting. Irrigation was maintained at 25, 50, 75 and 100% of the effective transpiration of the most irrigated shelf. Transpiration of plants was monitored continuously on each shelf, as well as the climatic conditions and substrate properties until the end of cultivation at the 16th week. Plant transpiration was also simulated using a soil-plant-atmosphere model in order to account for the strong link between the climatic conditions and stomatal resistance, but also for the influence of substrate matric potential on stomatal resistance. This model provided good results to simulate plant transpiration under deficit irrigation

Effects of prolonged water restriction on plant interactions with their environment – case of potted ornamental crops grown in greenhouses.

International audienceIn greenhouses, reducing water consumption by increasing water efficiency is of great interest in order to limit the environmental footprint of cultivation and reduce costs. However, satisfactory irrigation is needed to get plants of a good quality. When reducing water inputs, if the quality decreases because of visible physical adaptations, these are coupled to physiological adaptations that limit water losses by transpiration. Understanding these adaptations is therefore required in order to model and thus forecast plant transpiration in the scope of precision horticulture. For this purpose, an experiment was conducted to understand the effect of prolonged restricted irrigation on potted New Guinea impatiens. Plants were grown inside a 100-m2 greenhouse compartment. They were distributed on four shelves, irrigated with different amounts of water from 6 weeks after repotting. Irrigation was maintained at 25, 50, 75 and 100% of the effective transpiration of the most irrigated shelf. Transpiration of plants was monitored continuously on each shelf, as well as the climatic conditions and substrate properties until the end of cultivation at the 16th week. Plant transpiration was also simulated using a soil-plant-atmosphere model in order to account for the strong link between the climatic conditions and stomatal resistance, but also for the influence of substrate matric potential on stomatal resistance. This model provided good results to simulate plant transpiration under deficit irrigation

Modelling soil-plant-atmosphere water transfer in greenhouse cultivation, under water restriction: how does plant growth affects transpiration and soil hydrodynamic properties?

International audienceIn greenhouses, optimized plant crop management is crucial for environmental reasons and for maintaining the competitiveness of the horticultural sector. In this context, reducing water consumption by increasing water efficiency is of high interest but requires predictive models of soil-plant-atmosphere water transfer. Such models have mainly been developed for open field conditions and very few models exist under greenhouse and plant in container contexts. The objective of this study is to develop a specific model predicting soil-plant water transport for plants in constrained conditions. In this prospect, " New Guinea " Impatiens were cultivated in containers inside a greenhouse during fifteen weeks under both water-comfort and water-restricted irrigation management. Plant transpiration and water status in peat were recorded every 10 minutes whereas measurements of peat saturated hydraulic conductivity (Ks) and water retention were performed every 30 days. Simulations of water-restricted plant transpiration were conducted using HYDRUS 1D with input data inferred from measurements. These data include the water-comfort plant transpi-ration, the hydraulic conductivity, the van Genuchten retention curve of peat and root water uptake parameters assuming that plant growth was negligible during water restriction. Experimental results show that the water matric potential reached a minimal value of-58 kPa during water restrictions. Results also reveal that peat water retention increased along time with root growth due to peat macroporosity decrease and microporosity increase. Simulations show that HYDRUS reproduces accurately the water-restricted plant transpira-tion for a given week and therefore gives promising results. However, even if formalisms have been validated, it appears that parameters are not steady during plant growth, suggesting the actual limit of soil-plant water balance models. Thus, peat hydraulic properties and root water uptake changes need to be modeled. Future works is needed to increase the simulation of the growth-dependent water-restricted plant transpiration and to take into account the spatial root distribution. Moreover, in order to get a complete growing media-plant-greenhouse climate model, the challenge is now to couple the soil-plant model with a plant-climate model under water restriction taking account accurately of the stomatal resistance

Modelling soil-plant-atmosphere water transfer in greenhouse cultivation, under water restriction: how does plant growth affects transpiration and soil hydrodynamic properties?

International audienceIn greenhouses, optimized plant crop management is crucial for environmental reasons and for maintaining the competitiveness of the horticultural sector. In this context, reducing water consumption by increasing water efficiency is of high interest but requires predictive models of soil-plant-atmosphere water transfer. Such models have mainly been developed for open field conditions and very few models exist under greenhouse and plant in container contexts. The objective of this study is to develop a specific model predicting soil-plant water transport for plants in constrained conditions. In this prospect, " New Guinea " Impatiens were cultivated in containers inside a greenhouse during fifteen weeks under both water-comfort and water-restricted irrigation management. Plant transpiration and water status in peat were recorded every 10 minutes whereas measurements of peat saturated hydraulic conductivity (Ks) and water retention were performed every 30 days. Simulations of water-restricted plant transpiration were conducted using HYDRUS 1D with input data inferred from measurements. These data include the water-comfort plant transpi-ration, the hydraulic conductivity, the van Genuchten retention curve of peat and root water uptake parameters assuming that plant growth was negligible during water restriction. Experimental results show that the water matric potential reached a minimal value of-58 kPa during water restrictions. Results also reveal that peat water retention increased along time with root growth due to peat macroporosity decrease and microporosity increase. Simulations show that HYDRUS reproduces accurately the water-restricted plant transpira-tion for a given week and therefore gives promising results. However, even if formalisms have been validated, it appears that parameters are not steady during plant growth, suggesting the actual limit of soil-plant water balance models. Thus, peat hydraulic properties and root water uptake changes need to be modeled. Future works is needed to increase the simulation of the growth-dependent water-restricted plant transpiration and to take into account the spatial root distribution. Moreover, in order to get a complete growing media-plant-greenhouse climate model, the challenge is now to couple the soil-plant model with a plant-climate model under water restriction taking account accurately of the stomatal resistance

Modelling the stomatal resistance under water comfort and restriction to assess the transpiration of a greenhouse New Guinea Impatiens crop

International audienceIn greenhouses, reducing water consumption by increasing water efficiency is of high interest. To reach this goal, predictive models of soil-plant-atmosphere water transfers may be used. However such models have been mainly developed for open field conditions and very few models exist for greenhouse plants grown in pots. Implementing these models requires an accurate estimate of the stomatal resistance Rs. The aim of this work is to implement and adapt the multiplicative Jarvis model (1976) to calculate Rs for greenhouse potted plants not only under water comfort but also under water restriction, through the introduction of a new multiplicative function depending on the growing media matric potential. The obtained model could then be tested to evaluate transpiration. To establish the model parameters, an experiment was conducted during sixteen weeks inside a greenhouse with ornamental plants grown in containers on shelves. Both water comfort and water restriction conditions were applied. The peat matric potential, radiation, temperature and humidity were continuously recorded while Rs was measured and transpiration was assessed with scales. Data collected on four weeks were used to fit the parameters of Rs depending on radiation and water pressure deficit under water comfort. The multiplicative matric potential function was then deduced from Rs measured on stressed plants. The model was validated against data and showed its ability to assess Rs both under comfort and water restriction conditions. The developed model of Rs could therefore help assess transpiration under various irrigation regimes