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United States Department of Agriculture

Agricultural Research Service

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Research Project: Water Use in the Propagation of Vegetative Annuals

Location: Application Technology Research

Project Number: 5082-21000-017-08-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Sep 10, 2013
End Date: Sep 9, 2018

The objective of this project is to model water use in propagation for the purpose of matching water application with water demand in order to conserve water through maximizing water use efficiency.

An experiment will be designed and run inside of a growth chamber to measure the rates of evapotranspiration and transpiration gravimetrically using load cells. These load cells will be calibrated to measure the mass of the cuttings in grams taken over time. We will use this data to calculate these rates. On each load cell a group of cuttings 1, 3, 5 or 7 days old will be arranged. These cutting ages represent the time frame between the initial stress of being severed from the mother plant and not having roots to the beginning of the formation of new roots. Prior to being placed on the load cells each cutting will be placed in a water pick. The amount of water in the water picks will be quantified prior to the start of the experiment. Upon the conclusion of the experiment they will be weighed again and the amount of water taken up into the cutting will be calculated. This will show us how and if the amount of water taken up into the cuttings changes based on the environment and also cutting age. Mist will be applied to these cuttings prior to beginning the measurement of the rates of evapotranspiration and transpiration. The cuttings will be left in the chamber under a constant environment long enough for the mist to evaporate and a reliable rate of transpiration can be measured. Throughout the growth chamber sensors will be placed to measure air temperature, relative humidity, leaf temperature and light levels. The data from these sensors will indicate how these environmental factors affect rates of evapotranspiration and transpiration. We will also have leaf wetness sensors placed throughout the chamber as this may be utilized as a way to measure when to apply mist. The chamber will be kept at 21°C for the duration of the experiment based on typical greenhouse temperatures found throughout the industry. Two factors will be modified in the chambers. Light levels of 0, 50 and 200 W/m2 and a range of VPD levels 0.5, 1.0 and 1.5 kPa. These levels of VPD will be accomplished by adjusting the relative humidity of the growth chamber. Following statistical analysis the factors that contribute greatest to water loss will be determined. Using the results from this experiment a model will be developed from the major factors involved. We hypothesize that air temperature, relative humidity, light and cutting age will all play a significant role in model development. All of these factors are easily measured in a commercial greenhouse making them easy to use in the implementation of this model. Once the model is developed it will be tested using environmental sensors and a datalogger in our research greenhouse. This test will allow us to make adjustments as needed and also continue its use in our other research facilities for further investigation. Upon satisfactorily completing this model we will partner with commercial growers to do trial implementations in their facilities.

Last Modified: 10/20/2017
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