Yield, Growth and Water Use Efficiency of Tomato Subjected to Elevated Carbon Dioxide Under Drip Irrigation.

Agricultural and industrial practices have increased atmospheric carbon dioxide (CO2) which is considered to be a leading cause to global climate change. However, since CO2 is essential for photosynthesis and glucose production, increases in atmospheric CO2 could potentially lead to greater crop yield, productivity and water use efficiency. The goal of the study was to assess the effects of two CO2 levels and two irrigation regimes on the yield, growth and water use efficiency of fresh-market tomatoes. The experimental design consisted of four treatments replicated four times. The crop was , grown on a sandy loam soil in sixteen open-top chambers (15ft W x 5ft L x 10ft H) at the California State University-Fresno farm during the summer of 2011. Eight chambers received ambient air and the other half were subjected to elevated CO2 delivered through poly vinyl chloride (PVC) pipes. For the CO2 enriched plots, mean daily CO2 levels within the crop canopy averaged 600 ppm during the 8 hours of application, whereas concentrations in the ambient plots averaged 390 ppm. For each CO2 treatment, the crop was irrigated through a subsurface drip system at rates equivalent to 100% evapotranspiration (ET) and 80% ET based on California Irrigation Management Information System (CIMIS) data. Results of the first-year study showed no significant difference (α ≤ 0.10) in the yield of red and green tomatoes, and in the incidence of blossom end rot among the four treatments. However, CO2 and irrigation rate significantly affected (α ≤ 0.10) the yield of breaker tomatoes, with the greatest amount of breakers occurring within the plots subjected to elevated CO2 and 100% ET. Plant height affected with the highest levels measured in the Elevated CO2-100% ET treatment at harvest. Above ground biomass and root dry weight were significantly greater in enriched CO2 plots. However irrigation treatments did not have any effect on tomato root dry weight. There was no significant difference in water use efficiency among treatments. These results are a major contribution to the overall goal of our ongoing research aimed at evaluating productivity, quality and water use efficiency for vegetable crops subjected to elevated CO2 levels.