Hydromulch & Compost Study

Hi All

Time to blog the results of our, almost year-long, Hydromulch Study conducted at the Erosion Control Training Facility in Redding, CA.  

We were testing whether thick applications of Hydromulch would in fact "smother" or hinder seed establishment.

We used Nassella pulchra, Elymus Glaucus and I think 1/3 Leymus triticoides (these are relatively large grass seeds but widely used in No. CA.).  

We did uniform soil prep (trackwalking), put the seed down uniformly UNDER (not with) the hydromulch and then covered with all kinds of commonly used hydromulches - Soil Guard, Flexterra, TeraMulch, hydrostraw, and the cotton mulch (NAG).

We documented NO discernible ill effects from higher rates.  Actually just the opposite!!!  

This winter had such intense storms it was very unusual and the lower rates of hydromulch resulted in quite a bit more erosion - one more storm and I predict the seed and slopes would have been lost on the 2000#/ac applications.

 

What is most significant is that we also applied a compost blanket 2" thick.  There was NO reduction of seed establishment, if fact the compost blanket grew the BEST grass, by covering seed with 2" of compost.

This finding is consistent with all my experience in putting down compost blankets with the Compost Blower machine - Hilltop Burn Dump (2005), Alberta DOT Pembina River 2006 and 2008.

Hope you enjoy and hope this paper somewhat "lays to rest" the notion that Compost Blankets at 2" will smother seeds.   

We must, as EC Specialists, find a balance between veg establishment and effective erosion control during the establishment period.  Good luck   

John

CLICK HERE TO DOWNLOAD THE PAPER

BUT:  What say you?  What's been your experiences and/or opinions?  Leave some comments below and let's get some conversation going!

Update on Friday, September 4, 2009 at 2:39PM by WatchYourDirt

Quick Follow Up:  The paper that is available for download is a summary version of the full paper, which will be presented at EC10 in Dallas, TX.  Yet another reason to get yourself down south this winter!

Comments

[Scott Satterthwaite]

Thanks John and Dave. EPA is proposing effluent limitations for pollutants (nutrients, sediment and turbidity) from construction sites. When I sent this information to a county stormwater engineer consultant he was impressed with the trial, yet was concerned about nutrients leaching from the compost material. I have worked with other types of compost BMPs and believe the nutrients are either tied up or used up in the bio process.

[Greg Balzer]

I believe your findings about the seed germinating through the compost, but there are others here at Caltrans that are skeptical. Could you post a few photos with captions that compare/contrast the results. As a "visual" I 'd much rather look at a few photos that read "yet another" report.

Thanks,

Greg

[scott frazer]

John

What was the rainfall during the duration of your hydromulch study?

My own experience in Tehachapi, CA during the development of several wind energy sites was that hydromulch is not as effective as using broadcast straw tucked in well by hand or with a roller with modified sheeps foot design.

My feeling was that in areas that receive less than 10 inches of rainfall per year the glue holding the hydromulch together creates a paper-mache that is likely to inhibit seed germination. We had some contrators try applications without the usual binding agent and these seemed to have better results. We were working on the edge of the east slope of the Sierra Nevada where Mojave desert influence was significant. Of course the steep slopes with shallow soils and high wind speed all tended to dry out the site before plants could germinate.

Best Regards,