Plastic Mulch Reduces Irrigation, Weeds, Fertilizer; Adds to Production TIme

I wondered what would happen if I took plastic mulch, like they use in vegetable row production and applied it to pot-to-pot container production.  I eventually found a way and a team to run the experiment and had some interesting findings.  

The first commercial grower using the plastic mulch in production

We wrapped #1 containers, filled with potting soil, with black or white plastic mulch and planted ligustrum liners through a punched hole in the plastic.  We put a normal amount of slow-release fertilizer and used overhead irrigation to water them.  Water was scheduled by soil moisture sensors.  We grew the plants for 22 weeks and compared them to a control without plastic mulch. 

We found that black plastic saved about 82% of the water applied, and white plastic saved about 91% compared to the non-mulched control.  Water from irrigation is still able to move down the stems and into the plant hole and reach the soil.  Plastic mulch reduced weed growth seven-fold and weeding times by nine-fold.  Plastic mulch reduced the amount of fertilizer that was lost due to irrigation leaching.  Over the course of our experiment, fertilizer kept releasing, wasn't flushed by irrigation, and wound up affecting the pH negatively.  So in the future I would recommend using much less fertilizer with plastic mulch; maybe even one half less than normal.  This could be looked at with further experiments.

Amazingly, the soil temperatures were not affected by plastic mulch and this might be due to the fact moisture sensors were continually triggering the control plot to irrigate or when pots are grown pot-to-pot radiation may be reduced between pots, so mulch doesn’t really add a benefit.

Plastic mulch added about $4.94 per 1000 containers or $0.005 per pot which is about the same as normal herbicide applications during a production cycle which wouldn’t be needed using this method.

In our study, plastic mulch plants also took about 2-3 weeks longer to grow.  This might have been due to higher fertilizer salt and extremely low pH in the soil from reduced irrigation volumes.  In the future, this will need to be looked at a little closer in other trials.

Overall the study showed promise in using plastic mulch to reduce labor and some inputs when growing container pots.

For more information you can check out the journal article in HortTech http://horttech.ashspublications.org/content/28/1/58.abstract or watch the presentation https://ashs.confex.com/ashs/2017/videogateway.cgi/id/4216?recordingid=4216