PH around 7.7 - What should I do?

Discussion in 'Planting, growing, nurturing Plants' started by russell_c_cook, Sep 19, 2015.

  1. russell_c_cook

    russell_c_cook Junior Member

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    Hi everyone,

    I have a raised bed at Northey Street City Farm in Brisbane. I did a few tests of the pH today and found it between just over 7 in one spot to almost 8 in another. It was a simple DIY kit from Searles.The tomatoes and tatsoi both seem to be doing well, but the beans are looking a little unhappy.

    Any tips on what action might be appropriate here? Add in some earthworms? Dig up the plants and add some acidic compost? Stick with plants that can get by in these conditions, and let the soil slowly move more towards neutral as the bio-community becomes richer?

    Any tips would be great :)
     
  2. songbird

    songbird Senior Member

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    pH of 7.7 - 8.0 is not that horrible, but if you want to gradually lower it use elemental sulphur in small quantities along with your compost. worms probably will not have as much effect (depending upon species) as the organic materials that they'd feed upon.

    are other people using the same soil for their gardens there? are they having similar issues with the beans?
     
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  3. Geoff Lawton

    Geoff Lawton Administrator Staff Member

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    Yep gradually add sulphur powered not too much like sugar on a donut and wash it in, do not use ash on the garden or in your compost mixes, you could add some bentonite powder to add fine clays, you soil is probably sandy, well drained with some ash incorporated is my guess, keep adding compost with mulch on top.
     
  4. russell_c_cook

    russell_c_cook Junior Member

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    Thanks for the ideas guys.

    My idea for now is to stick with alkaline-hardy plants, and mix in compost with every planting, and see what happens. I put in some Jerusalem artichokes today, my reading suggests they should be able to cope. I'll try elemental sulphur if the pH isn't going down in a few months time.

    Has anyone heard of using pine needle mulch to gently reduce pH? I've read online that it can work, but also that it doesn't and is ill-advisable. Any thoughts?

    My sister is in the plot next to me and her beans look better than mine. That may be because she used 4 sacks of Activ8 to supplement her soil, and I only added 3 sacks of dried compost which seemed to contain some uncomposted wood. I've heard others have used sulphur as a soil amendment.
     
  5. songbird

    songbird Senior Member

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    as with most gardening answers it can vary what happens. adding some pine needles as a carbon source isn't likely to make that much difference as compared to any other carbon source. there are other compounds in pine needles that make them not the best for constant use, but using them one out of five times might be ok, but again, for some plants and then not others... others may find it objectionable...

    uncomposted wood chips will act as a nitrogen sink and yes, that would affect bean growth for a while (even when beans are supposed to add nitrogen to the soil, they should be innoculated if the soil doesn't have sufficient amounts of supportive microbes). they may catch up later.

    i had a really good example this year of the differences between plants even if you think they shouldn't be treated differently. the green peppers i normally do not amend or fertilize, but this year i did and they hardly grew at all at first and then the growth came on late in the season. exact same garden, exact same amendment, the red peppers took off from the start and never looked back. had a great crop of red peppers... in the past few years the red peppers haven't done as well as the green so i tried something different and learned something. now it is likely we'll stop growing green peppers completely as we like the red peppers a lot more.
     
  6. Bryant RedHawk

    Bryant RedHawk Junior Member

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    On Asnikiye heca we have found that if you plant with the intensive style (closely spaced plants) the plants themselves will make minor adjustments to the soil pH through dispersion of exudates. This is interesting to us mostly from the observed changes in the immediately surrounding soil. When we did analysis of these soils we found a sphere of 0.2 reduced pH, these spheres were present at every root area. I had chosen a 5m x 8m spot where the pH measured 8.6 weighted average and at the end of the growing season the pH now measures 7.5 weighted average. This was achieved by the combination of using pole beans, yellow straight neck squash, bell pepper and sweet potato all planted in a 4cm thick, decomposing, hardwood mulch. Coffee grounds were also sprinkled on top of the mulch at monthly intervals, the depth of these added grounds was 5mm and they were placed as a ring around each of the plants base. No other additions were made. A control plot of 1m2 was amended the same but no plants were grown. The control pH change from the amendments was 8.6 at onset and was 8.3 at termination which was the pull date for the growing area.

    These findings show me that our best methodology for bringing pH down to slightly acidic (6.5 is our target pH) would be to incorporate compost at a rate of 1 cu. meter per 4 cu. meters of garden space. this would be done by broad forking this amendment into the top 8 cm but without turning the soil. We have many different mycorrhizal fungi growing in our soil and the microbiology of the soil is good enough to support 100 worms per 40 cm 2 area so this is a good indicator that things are not really bad but could be improved with judicial additions. This coming spring I am going to continue the experiment to see how the pH adjustment goes. We have not used any sulfur to date but do have some spaces that will get some in the future to lower the pH to levels that blueberries desire for thriving.

    Like Songbird has mentioned, every space is different and observation is the key to deciding what needs to be done for each to arrive at the desired end point.
     
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