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Kutztown, PA

Last Fall I was told my OM was perfect at 5%.This fall it's up to 18%. Funny thing is I didn't add anything but a very thin layer of maple leaves. My plan for this fall is a layer of cow manure and a 10-12" chisel till to give the bacteria a little O2. What are your thoughts on OM, i.e. what's the sweet spot, what's your go to OM, when do you apply it' what's your tillage plan???? I'm changing my site name to "Garwolf the Brain Picker"

10/14/2022 3:21:19 PM

Lodi, California

People have grown 2000+ in less than 5%. They've also grown them in 15+. It's an interesting question.

I don't know how your OM could have gone up so drastically. I've added 4" of compost and my organic matter was 7% 2 years later. It might be sampling error, or it could be legit who knows.

10/14/2022 7:53:26 PM

Lodi, California

If your soil actually is 18% organic matter, you'd be able to tell, and if it were me I probably wouldn't be putting on more compost

10/14/2022 7:55:28 PM

Grittyville, WA

I agree with Ashton, when I had a spot tested up at 18-20 percent things got noticeably spongy-- like the stuff on the ground in a forest.

10/14/2022 9:18:20 PM

Greater Mpls/St. Paul Metro

I have repeatedly made the claim that 5-6% is the sweet spot. I'll stand behind that argument until I'm proven otherwise. As an aside, there's not a soil on earth that goes from 5%-18% with only a thin layer of leaves. As such, sampling error and/or lab error is the only plausible answer here.

10/15/2022 9:36:50 AM

Greater Mpls/St. Paul Metro

Why 5-6%? Sure, 2000lbers are grown in all types of soil, nutrient levels, and OM levels. It definitely shows what the species are capable of. But with these anecdotal observations, one must always ask "what if this or that had been maximized, then what?" Example: what if the 2000lber grown on 2% OM was grown in a 5-6% enviro. Could it have reached 2800? Possibly.

I explain the rationale for 5-6% sweet spot in my Giant Pumpkin Fertility guide. And in a nutshell, here's the quick version: above 6%, these soils hold excessive water and become a fertile harbor for disease organisms. Moreso than what 2-3% OM would harbor. Further, mineralization of nutrients from 5-6% OM more than meets the fertility needs of a giant pumpkin, ensuring that all the groceries you need for a whopper are stored in that organic fraction. Lastly, this range also implies maximum biological activity without overshooting into disease range. Keep in mind that excessive Carbon (the major portion of organic matter) can be problematic too. More carbon (organic matter) requires more nitrogen to strike the coveted 12:1 ratio of an ideally humming system. On the other side of this argument, some may assert that 1,2,3 percent is ideal. Usually this is accompanied by lighter texture soils and lower disease pressure. The downside is that the soil holds less fertility and you gotta be pumping the fertilizers in much more frequently to keep driving growth. I'm the type of bear who likes his porridge "Warm". Why throw ice cubes in the hot stuff or eat the cold stuff while sitting on the stove if you dont have to? 5-6% OM is Goldilocks warm porridge. And again, in true bayesian style, I am more than happy to have my mind changed on this principle if someone can offer a more cogent argument.

10/15/2022 9:37:04 AM

Deer Park, WI

Whoopsie, I made the above two posts under the wrong acct. Shoulda been this one. Apologies.

10/15/2022 9:38:44 AM

Deer Park, WI

Gritty...I'm picking up your comment from a previous thread regarding different forms of OM. Your point is correct, current OM testing doesnt distinguish the different types of organic carbon in the soil. Please reference my most recent article in the GPC newsletter for a deeper discussion on testing methods to determine water soluble, organic carbon and nitrogen levels in the soil profile (as performed on the Haney test). Teaser: there's a grower from Anoka MN who recently won a little weigh off in CA who used this type of testing to help fine tune the dials of his soil. Lastly, I am hoping to present on this very topic in Boston, assuming the GPC will still have me.

10/15/2022 9:46:54 AM

Grittyville, WA

Thanks Joe. Was it Barlow I think who grew one to nearly 2k hydroponically? So maybe that one was grown at 0% OM. And then the Patons used peat moss this year and look at those results... G for Grow plus OM and you get OMG. (I dont know what percent OM they ended up with after all that added peat moss-- whatever it is seems to work.)
I look forward to some smart reading, thanks.

10/15/2022 1:48:49 PM

Kutztown, PA

Well it must be a lab area. I carefully sampled at 20 location, 6" deep, with a stainless steel spoon, collected the exact same amount from each location, carful not to put in anything that would compromise the results, mixed it all up thoroughly, put it in a gallons zip lock and sent it to Western Labs. I've been wondering how it went from 5 to 18 when nothing was added. The question now is which lab result is wrong - last years or this years? Hmmm - what to do. Maybe another analysis.

10/17/2022 10:09:26 AM

Kutztown, PA

I think I got a bad result. I sent a question to the lab. My patch certainly isn't spongy. In fact compaction is another reason I plan to chisel till. Last year the lab recommended that may OM was in the sweet spot and that the most OM I should add was maybe a dressing of maple leaves. All I added was a very light dressing (not really even a layer). Any body use mushroom soil for OM?

10/17/2022 10:39:10 AM

Kutztown, PA

Fortunately the lab still had my soil sample and has promised to rerun the OM. I know from experience in the environmental field that labs make mistakes but since an OM calculation is just a matter of burning off moisture then burning off the OM with no chemistry you'd think it would be hard to miscalculate. Maybe they forgot to burn off the moisture. Anyway, since I took exception to Ashton implying that I might have screwed up the sample collect I decided to check in with the lab :) Thanks Ashton. I'll have the rerun results later today I think and will post them here.

10/18/2022 8:27:44 AM

Kutztown, PA

St. Croix, Can you please explain the 12:1 ration concept?

10/18/2022 8:29:35 AM

Lodi, California

Garwolf anything's possible, just trying to provide rational explanations. I have no idea what your soil is like, but it I saw it, I'd probably be able to tell you whether your OM was closer to 7 or 18

10/19/2022 1:01:23 PM

Lodi, California

What I meant by sampling error, is maybe you got a sample from an area that, for whatever reason, happened to get more organic matter than the rest of your garden. I assume you took several samples tho then mixed so it should even out.

10/19/2022 1:04:02 PM

Grittyville, WA

There can be a monkey at the levers, I sent two samples of the exact same very homogenous dirt in and got results in that varied as much as the wind. The results were similar, but hardly the same.

As for organic matter, if its not composted, I think the issue is, it will compete for oxygen and nutrients in the soil, until it breaks down completely. Tilling vs no-till probably have different levels (and types) of organic amendments which can be added to reach their optimal sweet spot.

10/19/2022 1:27:32 PM

Kutztown, PA

Gritty, funny you should say that. I just got the OM rerun results back today. 9.4%. So, I have a 5% last fall, an 18% that was rerun now resulting in 9.4%. Maybe I'll just keep sending samples in until I get the result I'm lookin for :).
I've done a shallow till with a regular 26" garden tiller the last two seasons. I figure if I go to deeper tillage this fall that will help decomposition. I think your implying that green OM isn't what I need and I agree.

10/19/2022 2:23:41 PM

Lodi, California

Joe, thanks for the info about organic matter. I have noticed people here in cali tend to go high on the organic matter. We gave no rain in the summer and it's very dry, so it may be better to have higher organic matter here than say, in New York, or any state that gets lots of rainfall.

10/19/2022 2:27:31 PM

Grittyville, WA

I have a layer of pumice under me here so maybe thats why 18-20 % gave me good results, plus there's no issue with heavy precipitation in the summer here.

10/20/2022 12:33:11 AM

Bethlehem CT

My thoughts are that pumpkins as do most plants have very sensitive roots. If your soil stays too wet for too long you will have problems.

10/20/2022 8:49:07 AM

Kutztown, PA

I guess there's a 'sweet spot" for every soil/drainage type then - right?? Moisture will be hard for me to predict in SW PA. Year before last it seemed to rain every few days, then got 8" all at once in Aug. I was reluctant to water at all. This year rain was scarce. Better to dry than to wet since I can control the water when it's dry. Question: What if your nitrogen is to high - wouldn't the addition of some inert OM like soft would flakes help bring it down a little?

10/20/2022 9:05:24 AM

Lodi, California

I added some compost that had a lot of woody material from horse stall bedding. It composted several months then sat in the soil several months, and I still had to really push the nitrogen hard just to keep the growth from being stunted. Be careful adding wood to your soil.

10/20/2022 7:33:25 PM

Bethlehem CT

Garwolf I wouldn't try to correct too much Nitrogen by adding wood chips because Nitrogen that is available to plants from the soil is a fleeting element, you could get it out quicker by watering heavily and leaching the Nitrogen out of the root zone. Or just give it time to dissipate. The woodchips will tie up that nitrogen for a longer time than the excess nitrogen alone and potentially be more of a nuisance than the high N alone.

10/21/2022 9:02:34 AM

Kutztown, PA

Thanks Big Moon, I'm finding out that there aren't any quick fixes. What are your thoughts on how to decrease OM? Is it just a waiting game? I think I'm just going to rake everything off the surface. Also, since I want to throw good money after bad :), I sent more samples for OM % analysis. This time I divide the patch into two thinking one end might be better than the other since I've gardened there less.

10/21/2022 9:43:03 AM

Grittyville, WA

I think bigmoon is correct, tilling woodchips in could mess up your nitrogen for years, unless you were fertigating daily I dont know how you'd get consistent optimal results. Straw or leaves would break down in a more maneageable timeframe, but I am wary of tilling a lot of organics into the soil. Its probably not just nitrogen, but sulfer etc that the microbiology will hog away from the plants. Garwolf, I think you should try till vs no-till. You could cover the surface with organics during the winter then scrape off what remains in the early spring to get the soil to warm up. I think you're going to shoot yourself the foot if you try to oxidize all the organic matter out of your soil. I think that 3-5 % spot is for industrial agriculture where the soil structure has already been ruined crop residue is being tilled in. My cynicism shines through. Figure out if its broke before you try to fix it.

10/21/2022 3:38:16 PM

Grittyville, WA

The 3-5 % spot is for industrial agriculture where the soil structure has already been ruined and crop residue is being tilled in...?

When they study this stuff they are using one set of parameters? Which cultivation technique was studied? I think that 3-5 % is probably whats optimal for a tillage based system. For no-till, or a lighter surface scratch method, I bet the OM could be much higher with no detrimental effect. The high yield corn guys are the ones to watch. Ignore me and copy them, seriously :)

10/21/2022 3:55:51 PM

Kutztown, PA

Gritty, you're probably right. Maybe I'll just rake off all of the OM, i.e. weeds etc. and let the microbes do their magic. Probably just way over thinking OM. The whole thing with getting funky lab results has further reduced my confidence in lab results. Other than guessing it's all we got. At least some of it should break down over the winter and early spring I suppose.

10/21/2022 4:10:22 PM