2006 Annual Report 4d.Progress report. This report serves to document research conducted under a Specific Cooperative Agreement between ARS and The Ohio State University. Additional details of research can be found in the report for the parent CRIS 3607-21000-011-00D Develop Improved Technologies for Soilless Greenhouse Plant Production to Minimize Water, Labor, Agrochemical Inputs and Environmental Impacts. This Specific Cooperative Agreement is devoted to activating an outdated 12-chamber system to collect data on the interactive effects of light CO2, and fertilizer concentration on various aspects of plant growth and nutrient utilization. Use of this system, once renovation is complete, will enable studies to be completed in far shorter time providing analogous data with similar statistical power than that obtainable with a greater number of stand-along growth chambers or greenhouses. Major tasks were. 1)checking and improving the integrity of the 12 chambers in the system where air leakage was a major concern,. 2)restoring the air handler, which is the main control for temperature and humidity of the 12 chambers. Replacement of parts and regular system maintenance was performed,. 3)replacing the obsolete data acquisition and control system with a data logger based system. The old system was removed completely and replaced with a more modern, serviceable system, and. 4)installing a CO2 control system to control desired CO2 concentration level in the chambers. Three studies have been completed to date investigating the interactive effects of light, CO2, and fertilizer concentration on nutrient uptake, partitioning, plant productivity, crop quality, and development using petunia as a model plant. These studies tested the light level at which additional fertilizer was beneficial and what effect, if any, CO2 had on plant growth and nutrient uptake at the different light levels. Plants were evaluated for appearance, harvested periodically, and separated into flower, stem, and leaf biomass. Biomass was then dried and analyzed with ICP-OES for essential macro- and micro-nutrients. Low fertilizer-grown plants had consistently earlier and more flowers, but showed symptoms of nutrient deficiencies in the final few weeks of production at all light and CO2 levels. There were significant interactions between light and fertilizer treatments for different nutrients. Calcium uptake was greatly influenced by light level, Fe, P, and K were influenced by the fertilizer supply and Mg and B were inversely influenced by fertilizer supply at high light. These data suggest new management strategies are needed to improve fertilizer use efficiency in different environments. These results were presented at the American Society for Horticultural Science annual meetings in New Orleans (July, 2006).