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Reno, NV

Hi,
I am in the desert and my soil organic matter is only 0.5% which is pretty normal for here but my goal is to get it up to 8 or 9% OM. The cow manure I have is still too hot to use so I need to get some commercial compost to get going this year. I went and checked it out and its pretty clean...I guess they screen it. Anyway, does anyone know how many inches of this stuff I should put in to reach that %OM. Im trying to start out with a good baseline before I get my soil test done in a month to fine tune nutrient needs. I know, its not fall, but its what I've got ;) Advice is much appreciated.

2/29/2016 9:46:10 PM

Glosta

Ok lets try to explain this so none of use get lost. Including me.

Your test is done a basic guideline of 6 inch soil depth. some labs do 8 inch, some do 12 but the general guideline is 6 inch. The general soil weight at 6 inch is 2 million lbs per acre this is where fertilizer recommendations come from. so if .5% of your soil is OM then every 1000 sq ft you have 2295 lbs of OM. now as you add compost and till you will change the depth profile of your soil. For the sake of easy math lets say you add 6 inches of compost with 50% om. and don't till then you will retain that 50% OM if you test that top 6 inches. now lets say you you completely mix that top 6 with the first test 6 to a full depth of 1 foot. now you have taken the 50% and mixed it with the .5% giving you 55.5% over 1 foot. split evenly you now have 27.75% in the top 6 inches. so your question can only be answered if you know how deep you will be tilling after the OM is added. this way you can figure out what the depth adjustment will be.

3/1/2016 12:13:46 AM

Glosta

sorry the 50% and 55.5% were typos. too many numbers too late at night. hope my point didn't get lost in my typos.

3/1/2016 12:16:51 AM

Colorado

Rich I wouldn't try to get there in one season.4 inches/season is a lot and even that will put your K+ sky high. LL grew a 2109 in 2/3% org. Also make sure the commercial stuff isn't high in wood chips.

3/2/2016 12:55:34 AM

Muddy Waters

Spread it out 2-3 inches over the surface & till

3/2/2016 7:43:11 AM

Reno, NV

Thanks for the tips everyone. My idea was to till 6" of compost in a foot deep. Maybe it would be a good idea to add some peat to the equation so that I could up my CEC this year without loading the soil up too high with K for my first season back in it.

3/3/2016 12:37:30 AM

Pocatello (cliffwarren@yahoo.com)

Found on the web: http://www.extension.umn.edu/agriculture/tillage/soil-management/soil-management-series/organic-matter-management/

How do organic matter levels change?

To build organic matter levels in topsoil, more organic matter must be added than is lost to decomposition and erosion. Like a person trying to lose or gain weight, increasing organic matter is about changing the balance between how much energy goes in and how much is burned off.

Another way to think of soil is like a giant wood stove. You continually add organic matter (wood), and it burns to release energy and nutrients that will be used by plants and microorganisms. Ideally, you want a slow, steady burn that releases nutrients to plants as needed.

Intensive tillage aerates the soil and is like opening the flue or fanning the flames. Decomposition is desirable because it releases nutrients and feeds soil organisms. But if decomposition is faster than the rate at which organic matter is added, soil organic matter levels will decrease.

Reducing decomposition is only half the equation. It is just as important to increase the amount of organic matter added to the soil. Organic matter can be either grown in the field or brought to the field.

How long does it take? Building organic matter is a slow process. First, the amount of residue and active organic matter will increase. Gradually, the species and diversity of organisms in the soil will change, and amounts of stabilized organic matter will rise. It may take a decade or more for total organic matter levels to significantly increase after a management change. Fortunately, the beneficial effects of the changes appear long before organic matter levels rise. These improvements, however, can be reversed in a year or two by returning to previous practices.

11/15/2016 3:42:09 PM

Pocatello (cliffwarren@yahoo.com)

Why does it take so long for organic matter levels to increase? An acre of soil six inches deep weighs about 1000 tons, so increasing the proportion of organic matter from two to three percent is actually a 10 ton change. However, you cannot simply add 10 tons of manure or residue and expect to measure a one percent increase in soil organic matter. Only ten to twenty percent of the original material becomes part of the soil organic matter. Much of the rest is converted over several years into carbon dioxide.

11/15/2016 3:42:17 PM

Pocatello (cliffwarren@yahoo.com)

One thing I learned from the above is that OM is not a volume measurement, it's a weight measurement! So we may think that tilling in these leaves and manure are helping more than they actually are. In recent years I've tried to wrap my head around OM in soil. Whenever you till, you reduce OM due to decomposition. I would never till unless you are tilling something in. What we should be doing, perhaps, is never tilling, but adding lots of OM to the surface and just let it break down. Let the worms go crazy and maybe do the tilling for you. But I don't know.

11/15/2016 3:47:14 PM