2014 ASHS Annual Conference

Daily Water Use of Tomato Plants as Affected by Environmental Conditions and Plant Age

Alex Litvin, Anish Malladi, and Marc van Iersel

                Daily water use (DWU) by plants is affected by the size of the plants as well as the environmental conditions to which they are exposed. As plants grow, DWU increases as well. Environmental conditions, such as daily light integral (DLI) and vapor pressure deficit (VPD), can also affect DWU. We measured DWU of young ‘Moneymaker’ tomatoes and environmental conditions in the fall of 2013, to quantify their effects on DWU. Plants were grown from seed in 15-cm pots filled with a peat-perlite substrate in a greenhouse for 53 d. Irrigation was controlled by a datalogger, which maintained the substrate moisture levels at 35% (v/v). Plants were irrigated as needed and the datalogger recorded how much water was applied each day, as well as environmental conditions. Stepwise selection was used to describe DWU as a function of plant age and environmental conditions.  Plant age and the interaction between age and VPD accurately described daily water use of the plants (r² = 0.95, P < 0.0001). DWU by tomato plants generally increased over time, and peaked at 425mL/plant. However, DWU during the last 20 d of the study fluctuated by over 200 mL/plant. These fluctuations were correlated with changes in VPD, emphasizing the impact of environmental conditions on plant water use. Our findings describe how fluctuations in environmental conditions affect DWU by plants through the early phase of their lifecycle. This information can help growers better schedule irrigation and reduce the negative consequences of over- or under watering.