[nafex] mulching blueberries with woodchips

Lee Reich leeareich at gmail.com
Wed Dec 26 17:31:32 EST 2012


In my experience and understanding of what's going on in the soil, over time there shouldn't be much difference on the effect between any of the organic mulches. High C/N mulches do not tie up N because their breakdown rate is mostly at the soil-mulch interface, so is slow, with the subsequent mineralization rate about matching the rate at which N is tied up. This theory matches my 30 years experiences with mulching blueberries with various organic materials. I do add soybean meal, 1-2 pounds per hundred square feet to keep the plants vigorous; yields are very good, about 11 quarts per plant.

I think the important thing is to mulch with any weed-free organic material, without fussing between whether to choose one material or another. A fabric weed barrier not only is usually ineffective for long term weed control but also is counterproductive, interfering with biological activity at the mulch-soil interface.

Also, chlorosis due to pH that's too high or poor drainage is the same. Iron is not available to the plant in either case, with the resulting interveinal chlorosis of youngest leaves first.

Lee Reich, PhD
Come visit my farmden at http://leereich.blogspot.com/
http://leereich.com/

Books by Lee Reich:
A Northeast Gardener's Year
The Pruning Book
Weedless Gardening
Uncommon Fruits for Every Garden
Landscaping with Fruit
Grow Fruit Naturally

On Dec 24, 2012, at 1:41 PM, Michael Dossett wrote:

> Alan,
>  
> Telling the difference between a chlorosis derived from excessive pH and one caused by poor drainage is actually fairly straight forward.  A combination of leaf tissue nutrient analysis and soil pH testing, in this case, was enough to confirm what was going on and verified the site history.  Overall, leaf tissue nutrient analysis is a great way to monitor what is going on and tells you far more than a simple soil test for nutrient analysis.
>  
> I noticed two things about your links to land grant university guidelines about wood chips that are worth pointing out.  One is that they are for the upper Midwest and the SE.  I already mentioned that pine-bark substrates and mulches were the rule of thumb for production in the SE.  This fits very well with their production systems and conditions.  The other thing I noticed about your links is that the actual guidelines (not the project report from the grant, which only compared woodchips to no mulch and did not compare to sawdust nor did it give actual guidelines) also recommended sawdust.  If you read my email, I noted that in the Pacific Northwest, the conventional treatment is sawdust, with or without compost underneath.  I'm not saying that woodchips won't work, but if you read what I wrote, where wood chips or hog fuel were used in side-by-side treatments under the same growing conditions as compared to sawdust with and without compost,
> sawdust performed better, therefor I would not recommend wood chips in this area.  This is based on observations from grower's experimenting on their own, as well as grower-managed replicated research plots and university-managed trials. The links you provided are not at all contradictory to the argument I was making, but don't provide enough information for people to decide which of these was better, only that either can be used as a mulch and that wood chips is better than no mulch at all.  Aside from potential differences in the types of wood and trees that chips may come from, wood chips and sawdust break-down differently and do different things for the soil and at different rates.  They tie-up nitrogen differently so that fertilization regimes will have to be adjusted, they need to be replenished at different rates, they alter C/N ratio of the soil differently, and in many areas where incorporation of sawdust is recommended, incorporating wood
> chips would also change porosity and drainage differently in addition to magnifying the effects already mentioned.  These all go into adjusting the production system, rather than merely one aspect and are likely to change with different growing climates.
>  
> Oregon State University currently has a project for organic blueberry production using weed mat as a weed control.  This is in various combinations with sawdust and compost mulches on their own as well, as above and below the weed mat.  One thing that has come out of the preliminary results, so far, is an effect on soil temperature and canopy temperature that is changing the rate of water use in the plants and also a change in the rate of loss of soil organic matter.  Not to mention the fact that voles loved the weed mat and the researchers found the need to bait under the mat to control them.  This is the sort of project that will be able to provide real recomendations for organic blueberry production down the road as it takes into account all aspects of the production system including fertility, irrigation, and soil management in addition to growth and yield.
>  
> Michael 
> 
> Michael Dossett
> Mission, British Columbia
> www.Mdossettphoto.com
> phainopepla at yahoo.com
> 
> From: Alan Haigh <alandhaigh at gmail.com>
> To: nafex at lists.ibiblio.org 
> Sent: Sunday, December 23, 2012 1:17 PM
> Subject: [nafex] mulching blueberries with woodchips
> 
> Michael, how can you tell the difference from a chlorosis derived from
> excessive pH from one caused by poor drainage?.  I'm a little suspicious
> that those low points may have been like low points in many fields-
> possessing poor drainage.  Of course this is an obvious observation that
> was probably explored.
> 
> Here in the northeast woodchips are often used to mulch blueberries in home
> orchard settings, which is all I'm knowledgeable about and I fail to see
> why they should ever create problems- relatives like rhododendrons are
> routinely mulched with shredded wood as well and these plants thrive under
> this treatment at scores of estates I've seen. .  The only trouble I've
> had  with shredded wood is that it sometimes mats up and excludes rain
> water- it just runs off the surface.
> 
> I don't completely trust the kind of anecdotal examples you supply (not
> that I'm not offering the same thing with much smaller scale examples).
> I'd need a lot more info about how mulch was applied and what the weather
> and soil issues were- actually I'd need to see the site myself to be
> satisfied.  Always the problem with contradicting anecdotes.
> 
> Here are several mostly landgrant university guidlines that do recommend
> mulching blueberries with woodchips.  I'd be interested in any research
> based info you have on the affects of mulching blueberries with woodchips
> as I couldn't find any actual research on the subject.
> 
> http://mysare.sare.org/mySARE/ProjectReport.aspx?do=viewRept&pn=FNC97-193&y=1998&t=1
> 
> http://mysare.sare.org/mySARE/ProjectReport.aspx?do=viewRept&pn=FNC97-193&y=1998&t=1
> 
> http://www.ces.ncsu.edu/hil/hil-8207.html
> 
> http://www.ipm.iastate.edu/ipm/hortnews/2001/3-23-2001/blueberries.html
> 
> 
>> 
>> I have no doubt that what you say about humic acid production and mulching
> blueberries may be true, but there are a lot of >variables at play, such as
> what kind of mulch, or what kind of wood chips, and where the trees grew
> etc.? Just as there are exceptions to every rule, there are circumstances
> in which blueberries can be successfully grown in soils with a pH range
> higher than the 4.5-5.5 typically recommended; however, as a general
> guideline, most people will have the best shot at success if they follow
> this.? I have been to literally hundreds of different blueberry operations
> over the years, both in the NW and elsewhere?(there's more than 30,000
> acres in blueberry production within a 45 minute drive of my house) and the
> one thing I can say is that I absolutely cannot recommend wood chips as a
> mulch for blueberries.? While some people may have success with it
> elsewhere, in this area, every single field I've seen where they have
> mulched with wood
> chips or hog fuel, has underperformed, often times in comparison with the
> same variety being grown by the same person just a few rows away with
> conventional treatments of compost and sawdust.? As I've said, there are
> always exceptions.? In Georgia and Florida, most of the commercial
> blueberry production takes place in pine bark substrate, or with
> incorporated pine bark in the soil.? They have developed a system where
> this works for them, although they still have to acidify the soil.? In fact
> one very large blueberry farm I visited in Florida last month was growing
> primarily in a pine bark incorporated and mulched system with sulfuric acid
> in the water to help acidify, and they still had iron deficiency in some
> low spots in their fields.? It turns out that these spots were where there
> were limestone tailings near the surface that had been left there decades
> before, and they just couldn't get the soil and water acid enough in these
> places to avoid
> nutrient problems.
> ?
> Every site is different and not all wood chips or other materials are the
> same, and different cultivars certainly have a range of tolerances for
> differing soil conditions and production practices.? I encourage people to
> try to get their conditions as close to what the recommendations are as a
> start, because I believe this will be their best chance for success.?
> Having said that, sometimes you have to improvise and experiment to find
> another solution, and I encourage people to do that too.
> ?
> Michael
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