imafan26
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Soil test results

I got my soil test results today, it took about 3 weeks.
It really did not surprise me, but some of the recommendations did, so maybe someone can explain this

First sample was from my home garden, labeled Mililani. I knew it was acidic, I grow acid loving plants so I want to keep it that way. I do add compost (whatever is cheapest), vermicast, whatever comes out of my potted plants, I till in my crop residues and I use redwood compost (acidic) I don not use manures.
I also use a starter fertilizer with each planting.
I get big plants, very productive tomatoes, hot peppers, citrus, chard, leaf crops but poor root crops (they are all leaves not much root)

The second sample was from my community garden plot and labeled Wahiawa. The soil in this plot has been extensively added to. Compost, and steer manure, also mulch has been turned in to add biomass. I till in healthy crop residues if they are soft, otherwise all hard residues and weeds are taken to the dump. I tried composting in the garden, but unless I bag the weeds for a while they just grow in my pile. I supplement with citrus fertilizer. It is a little colder and wetter than Mililani. I grow chayote, citrus, Asian greens, kabocha, hyotan, beets, carrots, asparagus, pineapple. Tomatoes and corn struggle. There are a lot of diseases in the gardens so I cannot grow onions, they always get rust and I need to grow PRSV resistant papaya and maize mozaic resistant corn.

Here are my results
Mililani, Wahiawa, expected result

pH= 6.0, 7.6, 6
Phos= 2154, 212, 37.5
K= 452, 472, 250
Ca= 3137, 7577, 1750
Mg= 352, 529, 350


The recommendations were for small amounts of nitrogen. Urea at Mililani and Sulfate of Amonia at Wahiawa. That made sense.
It also makes sense that phosphorus will be less available at Mililani than at Wahiawa.
https://www.avocadosource.com/tools/fert ... les/ph.htm

So, here is my dilemma, if Phosphorus is for fruiting and rooting,
why is fruiting great at pH 6.0 but not rooting?

At pH 7.6 acidic tomatoes are puny and have smaller than expected fruit with smaller yields., but roots like daikon, beets and taro are very good?
It seems to be an either or thing at the extreme ends of pH but what causes that?

Asian greens and leaf crops at both sites are very good, so I know I have more than enough nitrogen and there are no nutrient deficiencies on the plants in the soil. Not even the citrus in the alkaline soil which gets biannual citrus food supplementation.

They also recommended even more compost for the Wahiawa site to bring the pH down. I tested the compost in the past. It tested at a pH of 7.8, so how will that bring the pH down?

https://menehunemagichawaii.com/docs/CompostTDS.pdf

Bobberman
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Lime. or some sort of shell that has calcium even slow release. Soil needs lime to activate other minerals! Its not always the acid its the mineral or catalyst!

Smallgardener
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Location: SW Kansas

Are your levels on your sample in PPM? If so then you have plenty of the in the first two (no more Phos is needed) and you are adequate on the third.
For your 6 PH levels you do need some Lime but not much. If they did not recommend any lime I would not put any out. There is no real good way to lower ph. But you can help it by using Sulphur or Gypsom depending on the level of excess lime in the soil. If your excess lime is high then you use Elemental sulphur. If the excess lime is low then you use Gypsom. But then all you are doing is getting rid of salts on the soil.
6 ph is not bad at all. I would prefer 6 over 8ph anyday. if your plants like the 6 ph then don't change it. If you water alot then the water can raise your ph of the soil simply by adding calcuim and magnesium that is in the water.

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rainbowgardener
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I agree. pH of 6 is not extreme, it is slightly acidic. You said you are growing acid loving plants, so you do not want to add lime or try to change that. Many vegetables really like a pH of 6.

pH 7.6 is only slightly alkaline (7.0 is neutral). But since as noted many vegetables like it slightly acid, slightly alkaline is less favorable in the garden than slightly acid. You are quite right, if your compost tests at 7.8 it will not help bring your soil pH down. Usually compost balances itself out over the composting process, even if it starts out as acidic or basic. Are you putting alkaline ingredients in to your compost? Wood ash for one is quite alkaline and slow to break down, so it would affect your compost pH.

Smallgardener
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One more thing. I just thought of . Doesnt Peatmoss lower the ph. In a small controlled environment it could work. I believe I read it somewhere to use Peatmoss in containers to lower the ph for Blueberrys.

imafan26
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The soil test is measured in ppm (parts per million)
I made an error entering the pH for Mililani. It was 6.4. The expected level was 6.0 so the pH is fine. It could be tweaked a couple of points higher by adding some compost.

The strange thing is that at pH 6.4 the phosphorus is 2154
at pH 7.6 it is 212
and from my other garden plot reported at a pH of 7.8 it was 1857

The phosphorus levels get higher the farther they are from neutral on both ends of the scale.

Phosphorus is necessary for blooms and roots. It is strange that at the acidic end blooming and fruiting are enhanced while at the alkaline end rooting is better.

Maybe it really isn't so much about the nutrients' presence at all, but about their relative availability at different pH levels. It may be the relationship between the macro and micro nutrients that is responsible for the differences.

Peat moss has a pH of about 5 or 6 so it will lower pH faster. Every compost I have tested, the ones made on site, vermicompost and the local greenwaste composter all have pH around 7.8. None of them are neutral. I do not understand how an alkaline compost with a pH more alkaline than my Wahiawa garden is going to bring the pH down.

The Wahiawa garden has always had more compost and manure added to it than Mililani. I think it is why it is so alkaline to start with. The soils in Wahiawa and Mililani are oxisols and normally acidic.

Bobberman
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I never woried about the ph I just followed common sense and add what I thought was good for the soil. I think once you learn the basics the common sense takes over. My dad used chicken manure leaves and lime and had the best garen in the area especially corn and lettuce! Its also good to read about everything gardening and broden what you know! sometimes the weed that grows tells you what the soil is like! if you are really having problems a soil test is a good thing!

imafan26
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I think your dad is right if it ain't broke, it don't need fixin.

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applestar
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Hmmm.... My IMMEDIATE thought when I read your post was -- why not grow acid preferring crops at the one site and alkaline preferring crops at the other site?

More precisely, I mean if something doesnt grow well at one site, try growing it at the other and see if it does better, and grow what grows best/better at each location. I feel like what you have is a great opportunity -- it's not easy to completely change the nature of existing soil.

Is there a reason you can't/don't want to do that?

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This is a bit OT but we watched a nature/science program on how the Hawaiian Islands were formed. With a history like that, it's no wonder that there are varying pH and nutrient/mineral levels in the soil even just a little distance away. :shock:

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Ummm.... Just noticed the pH of compost you mentioned in the OP. Might this be related to the 60% compost seed starting mix that you are having problems with in another thread?

imafan26
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Location: Hawaii, zone 12a 587 ft elev.

I actually do grow more of the root crops in Wahiawa and tomatoes in Mililani. I'm just trying to figure out what makes the growing conditions so different.

The Mililani and Wahiawa soils are both oxisols, essentially weathered fine clay. The major difference has been in the quantity and type of organic matter that has been added.

The other post is not exactly the same. I usually make my own potting soil peat lite with either osmocote or vermicast added. When I cannot get enough peat or perlite I use potting soil. A few years ago super soil changed their mix and replaced the peat moss with compost. Seeds germinate well and initially grow well in the new mix. When the plants get about 6 inches tall, they yellow and die. This has happened over and over again. The mix is always wet.

I don't normally put any compost or manure in any potted plant. I have tried before and have not had good results.

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ElizabethB
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Good for you - your extension office is responsive enough to do lab test - some forum members can't get that done. A copy of the lab test has been sent to your County Agent so you can call and get a more specific interpretation and recommendations. That is part of the service you paid for when you had the test done. Please don't think I am brushing you off - you paid for a service so get your $$ worth.

Good luck



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