Blueberry mulch

[Bluemchen]

In an effort to find an ericaceous mulch for my blueberry plants (planted in holes filled with sand and ericaceous compost), I used a roughly chopped mix of pine leaves/ twigs and wood chipping. It is fresh, though and not rotted down at all. I read something that said mulches like that would rob the soil of nitrogen...

Should I take it off and if so any tips on what to use?

Thanks

[Demeter]

I'm planning to visit a local pine forest and pinch (with owners permission) some pine mulch from the ground there - should be well rotted.

[Bluemchen]

Nice idea.

[valmarg]

Bluemchen, I think you should be all right using the wood chippings and pine leaves as a mulch. I think it's when you add that sort of material to a compost heap that it robs the soil of nitrogen.

A couple of other things you could use as a mulch are coffee grounds and spent tea bags/loose tea.

valmarg

[SimonCole]

The robbing of nitrogen occurs to a degree, but it is important to remember that blueberries grow on low-nitrogen soils anyway. This is due to the acid nature of the soil (pH 5.5-4.5), which reduces the availability of nitrogen for uptake. This is enhanced by boggy conditions that are typically nutrient poor due to the slow rates of decomposition. Also the "O" or "H" horizon of soil which is typically on the surface will reflect quite well the conditions you have established. Although in future I would stick the trimmings somewhere to decompose a bit because you want the organic carbon most of all, to hold in the moisture, not so much the nutrients I would imagine. But this advice depends a bit on your soil...

What is the pH of your soil normally would you say?

[ChrisH54]

Had heard about putting composted bark on have just googled and came up with this link from the RHS hope this helps.
Royal Horticultural Society - Gardening Advice: Blueberry Care

Chris

[Bluemchen]

HI Simon,

My soil is neutral, but I have planted the blueberries in holes filled with ericaceous compost and sand mixture. The holes took around 70litres of mix to fill.
What do you mean by the O or H horizon of the soil?

[SimonCole]

The "O" or "H" horizon is the layer of soil nearest the surface that typically contains high levels of organic matter. Thus "O" for organic or "H" for humus. Below this you can get layers of other soils that are relatively poor in nutrients. O and H horizons occur in highly acid soils because there are no earthworms to churn the soil and pull the nutrients down to lower horizons.

I would assume that the low pH (acidity) could only be maintained for so long because carbonate ions may move into the compost from the surrounding soil (assuming you have a high pH normally). But some people have had lots of success using the method you've chosen. A mulch each year of un-rotted organic matter, like sawdust would help maintain the acidity better than rotted stuff that is normally more alkali.

[Bluemchen]

Wow, you know your stuff, Simon.
So what about adding flowers of sulphur to acidify the surrounding area? I would rather an organic method, though - will sawdust be adequate? Any tips on where to get some?
Thanks

[SimonCole]

It's tricky to know what to do. A lot of the older books use your method so I would guess that you could stick by that. They do say in one of my old books, to add fresh sawdust and this would provide ammonium through decomposition. Sulphur chips can be obtained from the ferrous metal industry, but may be slightly contaminated. I have seen them used experimentally in the re-establishment of heather on a slate tip, so would guess that they help to mildly acidify. I would stick away from them unless you've tested your soil and it is getting too alkali because they can be over-dosed and kill off the soil biology. You want the pH below 6 to be safe.
I hope everything goes well for you Bluemchen

[TonyF]

I read in several books/mags that the pine needle mulch was the way that blueberries prefer to grow, apparently they were originally pine-forest plants and they have sort of a genetic predisposition to ericacious.

I scraped up all the pine needles under out pine tree, well rotted or not and mixed them with a bag of ericacious compost. Despite moving the bushes twice, the latest last year, this year the bushes are smothered in flowers and it looks as tho we'll get a decent crop so it probably mean your mulch will work also.

[Bluemchen]

I have tested my soil pH, and it was neutral. So in the future, when testing I presume I need to test directly in the planting holes where I put the blueberries, as opposed to the surrounding soil?

[wellie]

Please forgive me for 'butting in' unnecessarily, but Trousers and I are on the edge of woodland seasonally dropping pine needles, and it's been good for our Blueberry bushes in containers so far?

But I also wanted to add a little 'something' to the thread if I may?
Whilst The Moggies were staying with us the other weekend, we went in search of Blueberry bushes to buy for them, and learned that, whilst there's Group 1, 2 & 3 Pollination Groups, and bushes are 'self-fertile' not needing to, it DOES help enormously, if you have two that are in flower at the same time , as the crop will be significantly increased.

Many of you will indeed know that, but I'm hoping that someone who doesn't will read this now and know it for a better and more productive crop in years to come.
It seriously pains me when I think that a mere 'handful' of Blueberries, in the height of the summer in a plastic punnet, costs you about £2.50, when a bush can cost you £10 at the start of the season, and give you more than £10 worth of fruit in its' first season!

[SimonCole]

I agree with Wellie they are a great opportunity!

As to pH, It may help to test the planting holes. For the first time in ages I was covering acidification of forests in my lectures today. It would seem that adding sulphur can take quite a time to increase the acidity; there is a kind of lag and then dump of protons (the sub-particles that cause acidity) because the soil holds them in buffer. Adding ammonia seems to be the thing to do. In the soil this is converted to the solute ammonium. Plants take this up and use it. As they do, they take in the four hydrogen protons bound to the nitrogen one. They then immediately shed some of the hydrogen protons that are pumped back into the soil, where they cause acidity. Ammonium is plentiful in urine and some fertilisers. I am working on a way of processing urine, but for the time being if anyone is having problems, fertiliser is the thing to use.

I've had a think again about mulches and they suffer a major drawback: they contain quite a lot of calcium which keeps things neutral. This is true too for pines. When you go into a forest the top, "O" or "H" horizon is neutral... it is the soil underneath that is acid through the action of roots described above. Thus a mulch will keep the moisture in, which is vital, but may have less of an effect on acidity.

So I will be looking for a fertiliser with no added calcium ions to maintain acidity.