Simulating Growth and Development of Tomato Crop

Crop models are powerful tools to test hypotheses, synthesize and convey knowledge, describe and understand complex systems and compare different scenarios. Models may be used for prediction and planning of production, in decision support systems and control of the greenhouse climate, water supply and nutrient supply. The mechanistic simulation of tomato crop growth and development is described in this paper. The main processes determining yield, growth, development and water and nutrient uptake of a tomato crop are discussed in relation to growth conditions and crop management. Organ initiation is simulated as a function of temperature. Simulation of leaf area expansion is also based on temperature, unless a maximum specific leaf area is reached. Leaf area is an important determinant for the light interception of the canopy. Radiation shows exponential extinction with depth in the canopy. For leaf photosynthesis several models are available. Transpiration is calculated according to the Penman-Monteith approach. Net assimilate production is calculated as the difference between canopy gross photosynthesis and maintenance respiration. The net assimilate production is used for growth of the different plant organs and growth respiration. Partitioning of assimilates among plant organs is simulated based on the relative sink strengths of the organs. The simulation of plant-nutrient relationships starts with the calculation of the demanded concentrations of different macronutrients for each plant organ with the demand depending on the ontogenetic stage of the organ. Subsequently, the demanded nutrient uptake is calculated from these demanded concentrations and dry weight of the organs. When there is no limitation in the availability at the root surface, the actual uptake will equal the demanded uptake. When the root system cannot fulfil the demand, uptake is less, plant nutrient concentration drops and crop production might be reduced. It is concluded that mechanistic crop models accurately simulate yield, growth, development and water and nutrient relations of greenhouse grown tomato in different climate zone

Technical solutions to prevent heat stress induced crop growth reduction for three climatic regions in Mexico

In the last 15 years a significant increase in greenhouse area has occurred in Mexico, from a modest 50 hectares in 1990 to over 2,000 hectares in 2004. The rapid increase in greenhouse area is a result of an attractive export market, USA. Mexican summer midday temperatures are well above crop optimum and cooling is needed if heat stress induced crop growth reduction is to be prevented. The objective of this study was to determine the effectiveness and feasibility of greenhouse cooling systems for tomato culture under desert, humid tropic and temperate Mexican weather conditions. These climate regions are represented by Mexicali, Merida and Huejutla respectively. The cooling systems included a variety of passive and active systems, which through an engineering design methodology were combined to suit the climate conditions of the 3 regions. The evaluation was conducted via simulation, taking into account the most important temperature effects on crop growth and yield. The results showed that the cooling systems were effective in decreasing heat stress to plants. Investment costs of greenhouse with cooling equipment were under USD 50 m-2 and operational costs were under USD 10 m-2 for all equipment combinations and treatments except for the humid tropic climate of Merida. Solutions for Merida were both economically and physically not feasible due to too high humidity levels. This model study clearly indicates that cooling is feasible in desert and moderate climate regions of Mexico but in humid tropic climate regions feasibility is a problem. Application of design methodology and design evaluation with help of simulation greatly contributed to pointing out effective and non-effective solutions to reduce heat stress in hot climates

Sustainable crop production in greenhouses based on understanding crop physiology

More precise control of growth conditions has led to a strong increase in crop yield in greenhouses. To further improve crop production, product quality and sustainability, we need profound knowledge of the responses of plants to environmental conditions as well as crop management by growers (e.g., pruning and plant density). In young plants, rapid leaf formation initially boosts production through its role in intercepting light. However, we propose that many full-grown crops invest too much assimilate in new leaves. Responses of plants to the environment are seldom linear, and show many interactions. Furthermore, short- and long-term responses can be very different because of acclimation and feedback mechanisms. Therefore, research should not only study plant responses under constant conditions, but also analyse multiple interacting factors under fluctuating conditions. Controlling the climate should focus more on the microclimate near plant organs than on the average greenhouse climate. For instance, the temperature of the apical meristem may deviate by 4°C from that of the air. Leaf initiation rate depends on the temperature of the apical meristem, independent of the temperature of the other plant organs, and this has a significant impact on the plant phenotype. LED lamps open opportunities for energy saving while improving growth, yield and product quality, as they allow the instantaneous control of spectrum, intensity and direction of light, and the decoupling of lighting from heating. Effects of LED light on yield can be attributed to effects on leaf photosynthesis, plant morphology, which affects the absorption of light, and dry-matter partitioning. LED light can also trigger secondary metabolite production, resulting in increased disease resistance, or increased antioxidants such as vitamin C or anthocyanins. A next step in the control of the production process is indoor production without solar light in vertical farms. This step is boosted by developments in LED technology.</p

Crop growth models for the -omics era: the EU-SPICY project

The prediction of phenotypic responses from genetic and environmental information is an area of active research in genetics, physiology and statistics. Rapidly increasing amounts of phenotypic information become available as a consequence of high throughput phenotyping techniques, while more and cheaper genotypic data follow from the development of new genotyping platforms. , A wide array of -omics data can be generated linking genotype and phenotype. Continuous monitoring of environmental conditions has become an accessible option. This wealth of data requires a drastic rethinking of the traditional quantitative genetic approach to modeling phenotypic variation in terms of genetic and environmental differences. Where in the past a single phenotypic trait was partitioned in a genetic and environmental component by analysis of variance techniques, nowadays we desire to model multiple, interrelated and often time dependent, phenotypic traits as a function of genes (QTLs) and environmental inputs, while we would like to include transcription information as well. The EU project 'Smart tools for Prediction and Improvement of Crop Yield' (KBBE-2008-211347), or SPICY, aims at the development of genotype-to-phenotype models that fully integrate genetic, genomic, physiological and environmental information to achieve accurate phenotypic predictions across a wide variety of genetic and environmental configurations. Pepper (Capsicum annuum) is chosen as the model crop, because of the availability of genetically characterized populations and of generic models for continuous crop growth and greenhouse production. In the presentation the objectives and structure of SPICY as well as its philosophy will be discussed

Tomato Yield in a Closed Greenhouse and Comparison with Simulated Yields in Closed and Conventional Greenhouses

In 2002 tomato was cultivated in a closed venlo-type greenhouse to investigate the influence of cooling with forced air movement along heat-exchangers combined with high CO2 level under summer light conditions on production and quality. Transpiration in the closed greenhouse with forced air movement was, compared to a conventional greenhouse, higher at low light levels (2 instead of 1 kg/m2) and lower at high light levels kg/m2 (4 instead of 5 kg.m2). Comparison of the observed yield with crop yields predicted with TOMSIM showed that yield was increased by 22% from 46.2 to 56.2 kg/m2 compared to a conventional greenhouse with CO2 concentration always above 500 ppm. The higher CO2 concentration in the closed greenhouse (always 1000 ppm) could explain only a 9% yield increase

Modelling Nutrient Uptake of Sweet Pepper

Models simulating dry matter production have been developed for a large number of greenhouse crops during the past decades. This paper describes how plant-nutrient relationships can be incorporated in a model for greenhouse crops, with sweet pepper as an example. Based on climatic data, the model simulates the growth of plant organs, transpiration, water uptake and uptake of the various macro nutrients. A mechanistic photosynthesis-driven model is used to simulate dry matter production. For each plant organ its required concentrations of the various macro nutrients are calculated, which depend on the ontogenetic age of the organ. The required nutrient uptake is calculated from these required concentrations and the dry weights of the organs. If there is no limitation in availability at the root surface the actual uptake will equal the required uptake. When the root system cannot fulfil the demand, uptake will be less, plant nutrient concentration will drop and crop production is potentially reduced. The model was tested on data from two different climatic regions (France and Spain). The model was also used to show some effects of the greenhouse climate on water and nutrient uptake. The rate of water uptake per unit radiation as well as the EC of the water taken up by plants was shown to vary considerably. Finally, the utilization of the model in an integrated control and monitoring system is discusse

Cultivar Differences in Temperature Demand of Cut Chrysanthemum

The influence of temperature on dry matter production, growth analysis parameters, stem length, number of leaves and flower characteristics of 25 cut chrysanthemum cultivars was investigated. Plants were grown in the greenhouse at two constant temperatures setpoints, 16 and 20ºC. Destructive measurements were carried out at the end of the long day period and at flowering. During the long day period relative growth rate was increased at high temperature for all cultivars due to an increase in net assimilation rate and for a few cultivars also by an increase in leaf area ratio. Significant temperature x cultivar interactions were only present for stem length, number of leaves and leaf area ratio. For all other characteristics there were clear differences between the two temperature treatments and the cultivars. Depending on the cultivar, flowering was delayed by 4 to 13 days when cultivated at low temperature. At flowering, a significant temperature x cultivar interaction was observed for all measured or calculated parameters. For example, for one cultivar both the differences in number of days till flowering and the total dry mass between 16ºC and 20ºC were small while for another cultivar there was a 34% higher dry mass at lower temperature, while the growth period was not much extended. Differences in dry mass at flowering between the two temperature treatments could be explained by differences in growth rate. These data show good possibilities for breeding for low temperature demand in cut chrysanthemu