David H. Fleisher

Effect of temperature perturbations on tomato (Lycopersicon esculentum Mill.) quality and production scheduling

Summary Controlled environment experiments were conducted to evaluate the effect of a 2-week change in air temperature imposed after first fruit-set on tomato production scheduling and on the quality of vine-ripened fruit. Experiments were conducted with hydroponically-grown tomato (Lycopersicon esculentum Mill., cv. ‘Laura’). Air temperature was altered from control day/night temperature values of 23°/18°C for a 2-week period starting 10 d after fruit-set. Plants were returned to the 23°/18°C temperature and a minimum of eight fruits per treatment were harvested at three ripening stages, breaker (when 25% of the fruit skin had acquired a red tint), breaker plus 3 d, and breaker plus 6 d. A perturbation of ± 5°C (28°/23°C and 18°/13°C) was used in two Experiments (E1 and E2) and ± 7°C (30°/25°C and 16°/11°C) was used in a third Experiment (E3). Fruits were more responsive to an increase than to a decrease in temperature. Reductions in days to harvest (from 3.1 – 8.5 d) and fruit fresh weight at later stages of vine-ripening were observed for the high temperature treatments. Colour indices, soluble solids contents (SSC), acidity and viscosity at each ripening stage were significantly affected by high temperature treatments. The results indicate that short-term temperature perturbations following first fruit-set can influence the rates at which changes occurred in the external appearance of fruit (colour) and in their internal characteristics. The results can be used to improve environmental control and management strategies for tomato growers.

ADAPTATION OF SUBSTOR FOR CONTROLLED–ENVIRONMENT POTATO PRODUCTION WITH ELEVATED CARBON DIOXIDE

The SUBSTOR crop growth model was adapted for controlled-environment hydroponic production of potato (Solanum tuberosum L. cv. Norland) under elevated atmospheric carbon dioxide concentration. Adaptations included adjustment of input files to account for cultural differences between the field and controlled environments, calibration of genetic coefficients, and adjustment of crop parameters including radiation use efficiency. Source code modifications were also performed to account for the absorption of light reflected from the surface below the crop canopy, an increased leaf senescence rate, a carbon (mass) balance to the model, and to modify the response of crop growth rate to elevated atmospheric carbon dioxide concentration. Adaptations were primarily based on growth and phenological data obtained from growth chamber experiments at Rutgers University (New Brunswick, N.J.) and from the modeling literature. Modified-SUBSTOR predictions were compared with data from Kennedy Space Centers Biomass Production Chamber for verification. Results show that, with further development, modified-SUBSTOR will be a useful tool for analysis and optimization of potato growth in controlled environments.

Manipulation of Tomato Fruit Quality Through Temperature Perturbations in Controlled Environments

Quality factors such as size, color, taste, and nutritional content are important criteria for marketing of greenhouse tomato fruit. While the majority of the research on fruit quality factors focuses on effects of post-harvesting and storage conditions, the environmental conditions during plant growth and the time for which the fruit is allowed to ripen on the vine also influence fruit quality. Growth chamber experiments were performed with tomato (cv. Laura) aiming to study the influence of air temperature perturbations during fruit set on fruit quality at maturity, the time to harvest, and the harvest window. Plants were grown in 6” pots and pruned to the 2nd true leaf above the first fruit cluster. Nutrients were provided through a drip irrigation system. All plants were grown under the same environmental conditions except for a two week period beginning 10 days after fruit-set during which plants were assigned to one of three day/night temperature treatments, 28/23°C, 23/18°C, and 18/13°C. Five tomato fruits were harvested from each plant at three distinct physiological ages; breaker stage (taken as the point at which 25% of the fruit begins to turn red), breaker stage plus three days, and breaker stage plus six days. Harvested fruits were analyzed for mass, size, color, soluble solids content, pH, acidity, viscosity, and other quality parameters. Initial results show significant temperature effects on fruit size, mass, developmental rate, and fruit processing characteristics. The results are applicable towards the development of more efficient plant production strategies for greenhouse growers and for NASA’s advanced life support research program.

Model-based predictive control for biomass production in advanced life support

Abstract A model-based predictive control (MBPC) algorithm for crop production in a biomass production component of an Advanced Life Support System (ALSS) is introduced. The MBPC adjusts light intensity, air temperature, and atmospheric carbon dioxide concentration setpoints so that crop growth (total and yield biomass) follows pre-determined production schedules. Mathematical models developed for wheat, soybean, and white potato using multivariate polynomial regression (MPR) are used as the feed-forward models in the control. The control algorithm is evaluated for its ability to compensate for simulated environmental disturbances and sensitivity to modeling and measurement errors. A 24-hour time increment is utilized

Control of Crop Growth in Advanced Life Support Systems

Abstract An elementary method for controlling crop growth in Advanced Life Support Systems is presented. Two models for crop growth are considered, one developed by the agricultural industry and used by the Ames Research Center, and a mechanistic model. termed the Energy Cascade model. The controller is applied to both models using wheat as the crop. A variety of circumstances are considered, such as model errors, measurement errors, and the incapability of applying the desired control input. It is shown that the proposed approach is a potentially viable way of controlling crop growth.

Scheduling and Control of Crop Production for Advanced Life Support

Abstract Advanced life support systems will support human lives during space journeys. Plants will provide food, consume CO2, produce O2, and clean water within the enclosed systems. Computer models were developed for the purpose of analyzing effects of crop production schemes on food supply and resource requirements and for controlling plant growth and development. An object-oriented approach was used to develop a top-level model for crop production scheme analysis. Another approach developed controlled environment crop growth and development models by modifying open field crop models for formulating model-based control algorithms. This paper presents an overview of these two different approaches.