Effect of Palmolive® Pure + Clear Dishwashing Liquid on Plant Growth

Welcome to my office, the Doctor is IN!

I taped containers of Swiss Chard (Beta vulgaris) 'Bright Lights' to my office windows using packing tape.  They were started in small peat containers and transplanted as seedlings to these plastic buckets.  They are 20 weeks old today.

I prepared a High Dose of detergent using 50 mL of Palmolive® Pure + Clear Dishwashing Liquid dissolved into tap water in the amber bottle pictured here.  After agitation until no changes in refractive index were observed (when the solution appeared homogenous), 60 mL of the High Dose solution was transferred to a 3.78 L jug of tap water.  This was considered the Low Dose solution.  The control plants were watered with 100 mL of tap water from the same source as the Low and High Dose solutions.  Each plant was watered with the same volume of liquid at approximately 10 am this morning.

We hope to determine whether the detergent will be harmful or beneficial for the plants' growth.  We also hope to get a rough estimate of whether 'more is better' since many fertilizer treatments are beneficial at low dose while harming the living organism when applied in excess.  The experiment is projected to last 4 weeks.  I hope the blinds will serve as graph paper, in which case the plants are starting out at -13.5 blinds high.

The significance of this project is to determine whether it is safe for edible plants to be treated with grey-water from the 'farmhouse.'  Detergents are known for their insecticidal properties, and also as being a source of phosphate.  We hypothesize that the Low Dose will be beneficial for plant growth, while the High Dose will hinder plant growth and may even be lethal.  

The detergent treatment doses were prepared such that the Low Dose is a similar concentration as would be employed while washing dishes.  The experiment is controlled by using tap water, which does not include any nutrient solution.  Future studies may also include a chemically-fertilized group AND a group watered with grey-water from the dishes.  This work has relevance as more systems are being designed to reclaim water resources and incorporate vertical agriculture in urban spaces.