Thursday, October 28, 2010

Duck and Duckweed

This park was one of our favorite places to go when the kids were little.  There was a fountain in the middle and the water was really clear we could see small fishes in the water.  The other day I was surprised to see that it is now almost completely covered with tiny little floating plants called duckweeds (Lemna minor).   

Given the right conditions, duckweeds can be very prolific.  One reason for this fast growth in this pond could be high nitrogen content of the water.   The sloped surrounding grass area is kept green year round - meaning high amounts of nitrogen is applied on a regular basis.  It is expected that some nitrogen find their way to the pond through runoff.  A second reason for the high nitrogen content of the water could be due to the animal waste from all the ducks in area.

It appears that the duck population in the area cannot keep up with the growth of the duckweed.  I wonder what the Community Service District will do with this pond - to get rid of the duckweed infestation.  They could keep it that way or do something to remove it so that the water can be clear again.  They could increase the duck population but that will only increase the amount of animal waste going into the water.  They could skim the duckweed regularly but that would be labor intensive.  Duckweed is rich in nitrogen and would make an excellent composting material; local gardeners can be encouraged to do their part and harvest some of the duckweeds. 

Any suggestion?


Bom / Plant Chaser said...

No suggestions from me. I've never seen duckweed this profuse. Ours is more a problem of pollution and garbage, unfortunately.

One said...

Good observation from you. I think your idea to harvest duckweed as a nitrogen rich compost material is an excellent idea. There might be micro -organism that can be poured in to aid in balancing things up a little.

fer said...

I know this problem from a lake back at my country, they first tried to manually remove all the excess plants, but it was simply too much of waste of work. That until later, when they started using the plants to fed animals and as fertilizer

Curbstone Valley Farm said...

I think my suggestion would be to stop using synthetic high-nitrogen fertilizers on the surrounding lawns. Use a mulching blade on the grass when it's cut. When we had lawns, we never needed to fertilize them. Runoff like that, when it escapes into tributaries and streams, is what leads to toxic errant algal blooms in creeks and oceans.

Otherwise maybe they can turn the fountain back on, but they'll need much bigger skimmer box and filter! They could probably pay for skimmer by selling the duckweed for compost though :P I think composting it is a great idea.

Rosie Nixon Fluerty said...

I see this all of the time and have plenty of photographs of it. I call ponds like this pea soup. I would not know what to suggest to those with large expanses of water. My only experience is with garden ponds and a great tip is to rinse all new pond plants before you place them in the pond incase there is the slightest bit of duckweed attached to the plants from elsewhere.

Helen Lewis said...

Bom - I know exactly what you are talking about. I would say that this is a "greener" problem than the pollution that would be seen in the Pasig River. :)

One - Yes, Duckweed is quite common in many bodies of waters. The problem in California is that we do not get much of freezing temperatures that would kill the weed in the winter.

Helen Lewis said...

Fer - Indeed it is a lot of work to skim the weed from the water. I think that converting duckweed into a useful resource as feed and fertilizer is the only way to conquer the problem.

Curbstone Valley Farm - You speak with wisdom! If it was my own pond, I would take your advice immediately. However, for the parks services to go organic is a dream that we all dream at the moment. :) I'm hoping for a change.

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