building soil year after year

I remember a month or two back I was telling somebody about how I was searching for land inland.  "Why inland?" - I ticked off a list of reasons including "where it gets cold in the winter, you can build the soil faster because the soil microbes are more dormant ..." and an eavesdropper interjected "that's not true" - I ignored them and went on with my list.

I suspect that the interjector is simply under-informed in this space.

So!  I present my gobbledygook and if I am wrong, maybe somebody can offer more information.

The general idea is that if I take steps to build the soil with organic matter, it will last more growing seasons because the microbials are dormant in the winter.  So if I put a bale of hay on the ground, it will decompose faster in warmer climates.  Maybe twice as fast.  Maybe faster than that.

First, consider the peat bog.  Organic matter building up thicker and thicker over years and years.  I'm not aware of peat bogs happening anywhere but in really cold regions. 

Next, I've heard that in jungles, the organic matter is almost all in the plant life and that the soils are incredibly thin. 

Finally, I had a conversation with a fella the other day who was stationed on the northern-most point in alaska doing research.  He said there was hardly any life up there, but in the warmest part of the summer when the snow melted, you could dig down and .... never find soil.  It was just peaty-mossy stuff forever.  Dig and dig and dig and ....  no dirt.  No trees growing anywhere.  Granted, this isn't proof of my theory, but it is pretty indicative.

I'd think you could build the soil faster in a warmer climate with very mild to no winter. If you keep feeding the soil microbes year round, you have more of a "growing season" for them. I'd suspect this is why the dense jungles are in warmer climates. The result is less soil, more organisms. It takes the idea that the soil is alive to its natural extreme. I think the plan should be not building the soil itself, but the organisms in the soil. What's the point of building the soil if there is little growing in it? From what I've been studying on permaculture, the idea is to have more living OM in the soil. The living OM will stay put. Also returning the straw, chaff, and unused plant parts to where they were grown naturally builds the soil OM. Most of the OM in a plant is derived from gases in the air. The more growing season you have the more OM you can return to the soil, as there is more plant material generated in a year. Take your bale of hay example. Lets arbitrarily say you can grow one bale in a 100 sqft area in an area that has winters. Since you have longer seasons in a warm climate, you could potentially grow 2 or more bales from that same 100sqft. If you return that hay to the ground where it was grown, you will be building the soil OM faster in warmer climates.

Hay might not be the best example especially if you're using the hay for livestock feed. I recently saw a video where by selecting certain forage species, you could let your animals out to pasture year round, even in winter. That negates the extreme loss of nutrients from the soil due to removing the entire plant above ground. This deeply limits the need for hay. This leaves crops that you can return the straw and chaff to the soil.

Now ask yourself this: "Which environment is richer in life, the jungle or the peat bog?" I think the answer to this makes whether or not the soil is building faster a moot point.

I don't know that it is really a hard fast rule, just different.  There are acid peaty areas in the sub tropics, they are usually swaps though.

Yes, organic mater does break down quicker in hot climates but then again, we get to garden year round so everything happens quicker.  In cooler climates one must play way ahead with their soil improvement because it will take more time for the soil microbes to make nutrients available to the plants.  In hot climates, Lasagna gardening doesn't require so much waiting, pile and plant (though sunflowers and corn would like you to wait till the cardboard deteriorates before you plant them.)

So, organic mater breaks down quicker but stuff often grows faster and year round so you can conntinually keep the ground producing more organic matter to keep it built up.  Methods need to be a bit different though.  I think no till gardening methods are far more important to hot wet climates since tilling tends to loose organic matter from the soil and since it breaks down so much faster here, anything that looses it even faster is to be avoided.

Then again, there is more involved than just simply the temperature of the climate.  Is it hot and wet?  Or Hot and Dry?  Different methods and priorities will exist for the different situations.

So, Is it really better to live where a bail of straw will last you a year because the soil if frozen and dormant for all but a short planting season or are you better in a hot climate where you need 4 bails of straw because you get 4 full planting seasons out of the year?  There is a major bonus those in a cool climate get that we don't here in the sub-tropics, ya can't root cellar here.

I think the root cellar would not be needed there because you can just reap what you need when needed.

To some extent you can eat fresh food year round but one must adapt one's diet to the food available in the season and that can take some getting used to after growing up in our society.  Heck, it can be challenging to figure out how to prepare some of the lesser known veggies when most of the population has no idea what they are.

well Paul I welcome all comers to the inland peat bog frozen north..as what you described is absolutely my property.

we do have areas that are NOT peat bog..but in our area of the world we have what they call MICHIGAN PEAT..it is not the lifeless stuff of the tundra..but it is full of nutrients..people beg to come dig it up..but we don't let em..it is OUR bog.

yes things grow year around in Michigan..under the snow..it doesn't stop growing and the compost pile doesn't stop working..it might slow down, but it doesn't stop.

a good warm place to park your butt in the winter is in the middle of the compost pile.

yes we PLAN AHEAD for everything here..unlike the needs to do so in the south..i guess..never really lived in the south.

you have to plan ahead when you are going to have freezing temperatures at least 9 months out of 12..sometimes 12 out of 12..but we still manage to trick mother nature and get our crops out of the ground in the fall..and sometimes even here we can get 3 cuttings of hay..although i do not cut hay..i let my fields die down naturally and the deer graze them..and fertilize them.

to be honest there is great variety in our soils here..there is the deep black peaty soil and forest duff in the swampy forests on our property..and then there is the open fields..being slowly overtaken by trees we are planting..as we are not fond of the fields ourselves..they are generally clay that is at least 4' deep and sometimes way deeper than that..and the topsoil is fairly thin on top..but rich in nutrients..and generally if you stick something in the ground there..it will grow !! Then we do have a few areas where the topsoil is very thick but under it ..instead of clay ..is pure white sand..don't know why? the say we were left by glaciers..so they say..maye the glaciers had gathered sand and melted it in those strips of sand..i'm no geologist..but i do know our soil varies a great deal and it is fairly virgin..here..i do have a very in depth history of the property and know it was not utilized until the 1800's and then a farmer bought up (homestaeded) a square mile of the property here..and grew celery on a small pot of it..he ran a well drilling business off of the property..and he had enough animals to keep him alive..and that was about it..there was a chicken coop and maybe a cow at one time?? the land WE live on..was never used for farming except the one 45 x 45 area that we are now trying to rebuild..it is overtilled hardpan..and doesn't want to grow anything..we are working on building it up..it was too far from our old house but we are near it now and have a desire to see it improved.

the areas where our house are now were initially uncleared..until we had to clear them..so the soils were wonderful..we did NOT allow them to be removed..they were put back on top after the contractors left..Joel still has a pile of topsoil that he is gleaning from to put back over when ever there is any soil disturbed..we save everything we can on our soils.

i am so thank ful that our soils are very fertile and that i'm not stupid enough to remove that fertility without replacing it..so it will take care of us for a good long time

I grew up in Michigan but we lived up in the North West lower part of Michigan where sand seemed to be the order of the day.  (At least I was prepared for the sandy part of Florida gardening if not for the heat and weather.)

where ? I'm in the nw lower peninsula of Mich

Traverse City
(That is what the TC in TCLynx stands for)
We still have a historical family home in Alden near Torch Lake.

I'm 36 miles south

the ole homestead is between US 131 near Manton south of the Manistee river and west of Lake City..we are kinda in the ausable river valley which from Michigan you would realize is the coldest point in the northern lower pen..so we are cold..10 degrees colder than the nearest town most of the time.

we sit just above the water table in MOST Of the land we own..or it bubbles to the surface and forms streams and bogs..

our homes are on the dryest area of the property and as you go toward the river..things get wetter and wetter and deeper and darker..

Brenda Groth wrote:
I'm 36 miles south

Where 36 miles south?  Sounds like you got a good swath of glacier varied land there.  I do miss northern Michigan but there is little work for a stagehand there.  I try to get up to visit every summer, probably won't be till August this year.

Ok, sounds like interesting place.  Good for lots of water plants at least.

I think in the end, nature will regulate the process of soil building as long as we're returning our unused portions back to the soil. This should be fairly true where ever you are. I see what you're getting at with winters and soil build-up. I don't really see soil build-up as the defacto standard for land fertility. It varies from place to place. To quote Brenda's sig: Bloom where you're planted.

TCLynx wrote:
To some extent you can eat fresh food year round but one must adapt one's diet to the food available in the season and that can take some getting used to after growing up in our society.  Heck, it can be challenging to figure out how to prepare some of the lesser known veggies when most of the population has no idea what they are.

Have you ever read Mark Bittman's "How To Cook Everything"? It doesn't cover absolutely everything, but it covers a very wide range of foods. It teaches the basics of all the food groups and from there you can adapt many things to serve different purposes. I've learned a lot from it and can usually find a culinary use for just about anything put before me. Not that I'm a great cook. I'm just a bit better at it than I used to be due to that cookbook.

Will have to check that cook book out, thanks

another reall good book on eating locally is "Animal Vegetable Miracle" there is a website  www.animalvegetablemiracle.com  the family decided to move to a farm and eat only locally for a year..it was quite a challenge..they tried to grow as much of their own food as possible and then buy what they had to buy only grown locally..it was an interesting book..

It is true that the tropical regions have their advantages, but building soil is .... different.  You can build the soil and probably get the same value out of it, but it will get used up 3 to 5 times faster.

I guess some folks like the tropical areas.  And some folks like the puget sound area.  And I guess I like the areas that are inland.  And maybe if I just leave it that vague I can get on with my life.  But I'm a dummy that goes on to list:  more sun, fewer bugs, less fungal problems, generally the same growing season, easier to build soil ....

To each one's own.  Heck if we all wanted to live in exactly the same place, it would get really crowded.

oh heck just give me any opportunity to brag on Michigan and I will..that's all.

Ain't that the truth, TCLynx. Paul, i guess I'm not really sold on the soil building part. I think one could grow more plant life per space in a hot, rainy environment: i.e. rain forest. The plant life is returned back to the soil at roughly the same rate it is used. Thus attaining equilibrium. No need for all the extra soil. Our woodlands come closer to this than any other type of land in the temperate zone, I think. I can see you, in the Puget Sound area, having a challenge in building soil from raw earth due to the excessive rain. Is this where you were coming from with your idea, and wanting to move inland? I can't say I blame you. Being a Hoosier all my life, I can't see myself living anywhere else either.

You have much to brag about, Brenda. Michigan is a great place.

jeremiah bailey wrote:
. I think one could grow more plant life per space in a hot, rainy environment: i.e. rain forest. .

I'm curious about that. not that I plan on moving to a tropical zone! but it is an interesting subject. I think what constitutes food probably has something to do with it (edible doesn't neccessarily equal food in my book) factors such as different pollinaters may affect which food you can grow but it does seem with a year round growing season more could be cultivated. of course without freezes alot of pests and diseases don't get a yearly knock down........lots of factors to consider.

Those so-called diseases and pests are mitigated in other ways besides winter freeze. I can't think of anything that isn't attacked and/or eaten by something else. You may have some trouble with certain non-native plants that are sensitive to a particular pest or pathogen that thrives in the area, but what area doesn't have that problem? If you want further evidence about plant density in a hot, wet place, look at the green houses we use in the temperate zone. All they do is hold heat and humidity, and lengthen the season from what is natural to the climate. In essence, it is a micro climate that is closer to being a rain forest than the surrounding area. You can grow a more dense population of plants in a greenhouse than otherwise possible. I don't know if I'd experiment with a green house or not. They seem like a lot of extra work, and expense. But an effective experiment to test Paul's theory would be to have two identical crops grown on the same soil, next to each other in a field. One crop be planted under a greenhouse, the other is not. Everything would be done the same for each crop aside from the greenhouse. Each year the soil depth would be measured, and soil analyses be done for each plot. My bets would be on the greenhouse building soil faster.

i have a teensy tiny greenhouse here in Michigan. it is only 6x8' double wall ..

i have it sitting OVER the tank of our septic system (for heat)..the floor is dirt with good stuff added..it isn't very deep soil.

in the area of Michigan where i live it is called the au sable river valley, it is the coldest part of the lower peninsula..and it requires that you wait until the full moon in june to put out your tender plants..or they freeze..last night we had 27.7 degrees..

however..i have had tomato and pepper plants now growing in the greenhouse for a couple of months..there are peppers on some of the peppers..no maters yet but it has been a really really cold spring..we put a few candles in the greenhouse when frost is expected ..to keep the ambient temperature above freezing..(and if they don't start something on fire like last night ron put one by the boardwalk "head injury" and i went out this morning and it was smouldering, had to pour water on it) generally they will keep it frost free down to about 22 degrees.

we also use coldframes..and other means of keeping things growing longer than normal..we can keep tomatos and peppers growing in the greenhouse for about 8 months in an area that has a 3 mo growing season if we are lucky.

we also plant our greens in the shade here..as well as a lot of other crops..so they will bear a long time in the summer, so i have lettuces and baby greens for longer than the normal season..we also leave a lot of things in the ground growing over the winter..and if the deer don't get them some we can harvest in the spring..or during the winter if it is nice ..but of course..we can't grow nearly what they can in the warmer climes..

I however, would rather have it this way..i am ..like some plants,...extremely heat sensitive..i've had heat strokes in the past and they say once you have you are susceptible to them..so i prefer the cooler weather.

today it got up in the low 60's for a little while..and then it clouded over and we are in the 50's again..but we are picking rhubarb, asparagus, lettuce, peppers, green onions and mushrooms out of our garden..as well as many perennial herbs..you get used to putting things by..whether it is freezing, drying, canning, jerking, root cellaring, pickling or whatever..that is just a way of life in the frozen north..

at least one thing..we don't OWN an air conditioner.

I would imagine that a greenhouse is handy for growing things up there. I see them here and there around Indiana. Speaking of greenhouse heat sources, your septic tank idea gave me another idea. Has anyone ever tried a hot compost pile in a greenhouse? That sounds like a symbiotic relationship. The greenhouse does its thing by being an extra insulator, holding in sun heat and moisture, keeping the environment viable for the compost pile earlier and longer, and the compost pile generating heat to help raise the ambient temperature of the greenhouse. Added benefit of having fresh compost ready for seedlings and up-potting. It would be a biomass heater for the greenhouse with a very beneficial waste product.

yeah it does help to have the greenhouse..you can see the transplants are doing OK in there..June 1..but the seedlings are barely visible on the outside edges in side the greenhouse.
[/img]
the tank in under and in front of the greenhouse and the pipe to it runs under the boardwalk.
[/img]
and the soil around the boardwalk is very shallow but the farther away it is deeper..i still manage to grow quite a little produce on top of my septic tank !
[/img]
there is a lawn behind the greenhouse where the leachfield is and then gardens go down from there..this shows the lawn behind the drainfield.
[/img]

I think one could grow more plant life per space in a hot, rainy environment: i.e. rain forest. The plant life is returned back to the soil at roughly the same rate it is used. Thus attaining equilibrium.

All of that is true.  And in only loosely related with my point.

According to my point, organic matter decaying on the forest floor in a jungle is consumed rapidly.  The "soil" is more like "dirt" because of this rapid decomposition.  But!  The plants in the jungle do fine because they get lots of rain and lots of nutrients all the time. 

Right. To my thoughts though, soil build up is a moot point. The jungle, in my opinion, is the penultimate permaculture. Everything is returned to the soil, and used again at roughly the same rate. True, it is not really possible in our climate to achieve this, without huge expenses in infrastructure and energy at the least. But what I'm getting at is that soil build up is not the important factor. Nature will use what's in the soil as she sees fit. The other factors besides soil play the major determination in this.

According to your original assertion, the fact that microbes are more dormant in winter leads to faster soil buildup. I may have been misled somewhere, but I always thought it was the microbes that built the soil from organic matter added to the soil. If they're dormant, how are they building soil? Unless there is other context that is missing here from your original conversation that involved the evesdropper, I have to agree with that person. The winter months are when the soil is not being built up. I'd reason that the soil build up is due to other factors, such as erosion, runoff, and usage of the soil by plants, (lack thereof all three in winter.)

I guess my thinking is to focus the rich soil on the growing season.  Cold climates help with that. 

I've never heard of that before. How does the cold climate help? I'd think in any environment, you'd have to "focus the rich soil on the growing season." The microbes are what turn organic matter into more soil. How do dormant microbes help build soil?

If I have poor soil and I am trying to grow something, I can add a bunch of OM to the soil and then grow something. 

In a cold climate, that OM will last three times longer than in a warm climate.  Maybe ten times longer than in a hot climate.

just a guess, imo it will not last longer in overall measurements like growing days or season is my bet, if you can harvest a tomato all year  like 3 regular crops i figure that uses 3 times the nutrients and maybe with the extra strength sunshine maybe 4 times the yield? also tropical dry seasons would likely slow system nutrient use overall but then there is less leaching, i seem to be rambling it seems like apples and oranges, best to do what suits where you are and what you like.

Leif Kravis wrote:
just a guess, imo it will not last longer in overall measurements like growing days or season is my bet, if you can harvest a tomato all year  like 3 regular crops i figure that uses 3 times the nutrients and maybe with the extra strength sunshine maybe 4 times the yield? also tropical dry seasons would likely slow system nutrient use overall but then there is less leaching, i seem to be rambling it seems like apples and oranges, best to do what suits where you are and what you like.

but isnt that due to the bigger growth rate in tropical systems? Not only does organic matter decompose faster in tropical climates, it is also used by plants to produce living biomass faster. The overal biocycles all slower in temperate climates, plants grow slower, soils build slower. But soils build, in contrary to hotter climates where soils build and get used.

So a soil built in a topical climate doesnt last as long as in a temperate climate, but it does produce more yield faster. To go back to your example paul, in a colder climate you will build 3 times as much soil, but (roughly!) in a tropical climate this soil will be converted into food faster (3 times more?). And that was the main aim of having soil wasnt it? to grow crops?

I think comparing hot to cold climates about soil building isnt necessarily helpfull. Soil plays such a different role in the system. Specially for the choice of going inland or staying close to the shore(?), it doesnt change the role of soil. So you are in a nontropical climate anyway, and in a non-tropical climate building (building it up, not only creating it) soil is imperative.

To figure out where to get land, this soil thing isnt the only thing in the equation i guess, also important to be where you feel good, and to be on a piece of land where you fee you could build a longer lasting relationship with. But how much food it produces is also important (i guess this was why soil building came to mind?). And for this apart from the story of building soil, cold winter temperatures also slow you down, since the soil needs more time to warm up and generally after colder winters things like trees tend to need more time to get going.

Not saying warmer winters are necessarily better. Just adding to the equation.

... Still not getting why soil will build up faster in a cool climate with colder winters than in a cool climate with warmer winter... (if that is what you mean...)

but i would go for my feeling rather than (too much) reasoning, since people (me) tend to reason towards their feelings (instinctive preferences).

paul wheaton wrote:The general idea is that if I take steps to build the soil with organic matter, it will last more growing seasons because the microbials are dormant in the winter.

If you manage to have more growing seasons in a year, it might be that the organic matter lasts for the same number of growing seasons, even if it disappears twice as fast.

A lot of what makes rainforest soil thin is high precipitation, and the leaching of nutrients. If most of the soluble nutrients are gone, it would make sense that microbes have to consume more calories to get enough. Temperate rainforests have the same problem: I spent some time on the Smith river near the CA/OR border last summer. The erosion gullies (which probably started when Jeddediah Smith began destroying the local beaver population) showed a deep cross section of the soil, and the topsoil was very thin. As in tropical rainforests, some plants have to resorted to eating insects for their NPK. There are huge blooms of these carnivorous plants along some of the road cuts. Still, with so much rain, there was a lot of life around.

In cold climates, its easy to store organic matter in the soil, so you can build it up year after year and bank it in the soil.  Also the long summer daylengths help to produce prolific plant growth during the short growing season.  In hot, humid climates you have to store organic matter in the plant life as any organic matter in the soil is quickly broken down.  Here you have to be continually adding decaying plant matter to the soil to maintain its organic content.  You have to maintain a thick and nearly continuous plant cover or after a few years you'll end up with mineralized, low organic content soil.

This is where the European settlers in South Carolina ran afoul with their agriculture.  They tried to manage fields like they did in northern Europe, kept weed free and with lots of bare soil exposed for large portions of the year.  Typically cotton in the summer, with mostly bare soil through the winter between each summer's cotton crop.  It only took a decade of this sort of treatment to completely mine out the organic matter of the native soil that had accumulated over thousands of years, reducing a foot thick layer of native gray high organic topsoil to the low organic red clay now associated with Piedmont region of the state.  But as virgin land was plentiful back then, when the fields lost their fertility, they just cleared a new section of trees and started the whole process again, leaving the abandoned old fields to erode away until they could regrow a cover of pines, ending up as acidic red clay.  At the time, some people called this "land butchery".

As I am building up the organic matter in my garden soils they are regaining their gray color.

I believe that I agree with Paul about the cold helping to store the organic matter, but being a Michigan native I guess I've never lived anywhere where organic matter was depleated from the soil, except where people have overfarmed the soil and depleated it by never adding anything back.

I sheet compost here on most of my gardens near the house (cause snow prevents going very far with the materials in the winter) and the soil closest to the house where we throw out stuff in the winter is so rich that you can nearly stick your bare hand down into it without tilling ..and I don't till any soil unless I absolutely have to (which is seldom)..

the surrounding area around our property is a mix of peat, clay and sand, and the only area that really seems to be at all void of organic material is the sandiest areas, which are few and far in between here.

I do tend to put everything I can back into the soil, by usually using it as a mulch on top of the soil,, seldome digging it in..I let the worms do the work.

also we do tend to get animals that will take an interest in the sheet compost, and come and nibble on it from time to time, but they leave behind their own deposits which make the soil even richer (nice I don't have to spread the manure, they do that for me too)..

In the spring when the snow melts, there is always a large supply of deer and rabbit and bird manure that has been fairly evenly spread over my property , i just raid the piles out if they are too thick....so it is trye that snow does seem to gather and hold organic materials at least on our property.. Of course we don't have a problem with the wildlife here as some people do, we live in epace with each other..they seldom do any damage to my plants..

I also tend to allow moost of my plants to die down naturally in the autumn, and odn't clean up the garden areas until the spring.I know when it comes to disease this isn't considered a good habit, but we end up with a lot of rotting materials int he spring that help to feed the soil ..and we et a lot of self sown seedlings that way as well..if you have plats that are invasive as self sown seedlings you will want to remove those seedheads though

Paul

I remember reading an article many years ago that claimed the reason northern climates were so much better off was due to the frost cycle.
Unfortunately, I couldn't find that article, but I did find a study that may have been a source. It's economic theory and what not, most of it greek to me, but it was an analysis of wealth & productivity based on the frequency of frost, and it determined frost is good for us.

"Climate is defined in terms of the frequency of frost in winter, after a frost-free summer. 
A threshold of five such days was chosen to define climate zones and split the sample, in
a way that is clearly exogenous and has plausible economic effects.  One major channel
for these effects could be that seasonal frosts kill exposed organisms, raising the
productivity of investment in human capital and in agriculture by selectively reducing
competition from pests, parasites and disease vectors. " (emphasis mine)

Source: http://www.csae.ox.ac.uk/workingpapers/pdfs/20-13text.pdf

Replace "human capital" with "soil" and call it your own. 

The article I read, if I can put any faith in my memory, said the frost cycle lead to a more efficient breakdown of vegetable matter, making it available for the microbes which kept the nutrients in place in the soil, rather than feeding the insects which carry the nutrients away.  They claimed it added 1% to the yearly GDP of those countries lucky enough to freeze.  Compound that over 1000 years and it leads to a phenomenal advantage.

Frost does help to loosen and fluff up the top layer of soil.  Around here the frost line only goes down about 1 to 2 inches, but in the northern states it would loosen up the entire vegetable root zone.  That's why double digging is useful in warm climates in loosening up soil that hasn't had the benefit of frost heave to loosen it.  Although an active compost pile can do the same thing as its released nutrients supercharge the soil organisms in the soil underneath it and their activities act to loosen up the soil.

I don't know about that theory of insects carrying the nutrients away in frost free climes.  Most small soil insects don't travel far, living and dying in the same small volume of soil.  Larger insects, such as flies, wire worms, dung and rove beetles are just as likely to be importing nutrients in the form of their bodies and their eggs from other locations as they are to be carrying them away from your location.

Yeah, that insect theory may not hold water.  Like I said, I'm relying on memory.  Unless northern climates support lower insect loads leaving more nutrients for the microbes?

I do think, however, that Paul is correct in thinking the soil benefits from a freeze cycle. 

What is weird for me is to think the microbes are bad and need to be stunted. Are they consuming nutrients or releasing them to be useful? I always thought they made the nutrients available to the plants. Maybe they do both.

Maybe the frost cycle gives us humans a fighting chance to time our plantings so our food crops out-compete or at least hold their own against the microbes at harvesting the nutrients from last year's detritus.

I should go back to school.

While your decomposition rate is less, your primary production rate is also less.  To model it really simplistically You'd have to compare three curves -- one gain, and two losses... primary production on the plus side, volitilization, and microbial decomposition on the minus side, and look for cumulative difference.  Primary production increases with temperature, nutrient availability, and soil moisture.  If you are looking for maximum soil humus accumulation as a function of climate, look to the native ecosystem for evidence... While bogs are neat... they accumulate due to anaerobic soil.. not optimal for primary production.  Maximum stable organic humus accumulation (as opposed to just accumulation of woody material -- temperate rainforest kicks butt)... occurs in tall grass prairie... Mollisols... not too hot, not too dry, not too wet, not too acid, cold winter... I'd say Montana ain't too bad, but perhaps a little dry and a little windy during the growing season to maximize the primary production curve side of the equation?.. and the growing season is a little short.  Then again Eden is where you make it... we moderate climate to achieve this effect... Paul will figure out how to increase summer water, break wind, and extend his season to moderate his climate.