Happiness! Our Soil’s Organic Matter is Growing by Astounding Amounts

With our very sandy soil (CEC = 4 to 5), organic matter is extra essential.  Sandy soil is notorious for rapidly leaching nutrients and drying out fast, but organic matter can hold onto nutrients and absorb water like a sponge.  This sorta makes up for sandy soil’s missing clay content. 

So check out our super duper chart!  It shows the eight fields under our care (40 acres total), our management decisions, and organic matter data from soil tests.

Progression of the 8 fields under our care from 2008 to 2012.

It’s not wise to think a single data point is accurate, but series of soil tests can show general trends. 

Differences between Scott and Neighbor Fields

From 2010 to 2012, the average percent change in our fields (Scott) is over 50 percent!  This makes us super happy.  That’s a lot of sequestered carbon in just two years.  Since May 2009, the average percent change is over 100 percent, but I’m wary of including the 2009 test because it’s different than the other three Logan Labs tests.  But, organic matter in the low 1% range corresponds to how poor the soil was when we first got here. 

The average percent change in our neighbor’s fields (the three with data) is over 20 percent, still good!  The difference is probably explained by our neighbor’s fields not being in grass like ours are/were, and maybe our August 2011 amateur rotovating (still makes me cringe to think about it) burned out some soil carbon. 

The Three Best Fields

Like I said above, it’s not good to concentrate on single data points, but the organic matter percentages correspond to our perceptions of field quality.  We’ve had a feeling for a while that Scott West, Scott Middle, and Neighbor North and West are the fields that need alotta help.  In contrast, the three fields showing organic matter over 3% make me say “DANG!” when I bush hog them.  The bush hog works hard and slows the tractor’s RPM.  They produce a lot of biomass for sure.  Our McCarthy field was the one I photographed this summer.  The pictures show very strong and healthy plants even under drought and heat stress, something I attributed to compost, which might be true.  

More Organic Matter from Cover Crops?

The test data are mixed (and too few) to see if the cover crop fields stored more organic matter than the grass fields.  (We have no livestock and don’t sell hay.)  I know for certain that our cover crops grow way more biomass than our grass produces, so maybe the difference will show up on our future soil tests.

Upcoming Plans

We’re going to spread this year’s batch of compost, foliar spray liquid fish & seaweed, and broadcast calcium and micronutrient fertilizers.  We haven’t decided what we’ll plant on each field this spring.  We’ll soil test again next fall to keep accumulating data.  But all in all, things are looking up for our rapidly improving soil!


4 responses to this post.

  1. Posted by Rich on December 5, 2012 at 7:27 pm

    The way I’ve always understood it, organic matter mainly comes from the root system of the plant decaying, instead of the organic material decaying from the above ground growth. So, in the long run, a perennial grass plant will give you more organic matter because it has a much bigger root system (and it also dies back and regrows when ever it is grazed or mowed differently than an annual grass plant does).

    I know that there is a corner of one of our wheat fields that for some reason had been “abandoned” years ago and just grew Johnsongrass, sunflowers, giant ragweed, and bermuda for years until I finally decided to mow it for a summer, then ran a disc and chisel over it, and start planting it about 2 or 3 years ago.

    After wheat harvest this summer, I planted some sorghum-sudangrass, then it stopped raining and got hot. Most of the field looked horrible, but that corner grew some haygrazer that was at least 6′ tall (3 years later, you could still see exactly where the weed patch had been because that’s where the sorghum-sudangrass looked the best).

    I know how important higher OM levels are, but I wouldn’t have believed that there could be that much difference if I hadn’t seen it with my own eyes, and it got me to thinking about trying even harder to increase my OM levels (even if it means rotating to perennials for a few years). The hard part is recreating the conditions that built that corner over the rest of the field.

    What kind of pasture grasses did you plant in your fields?

    How much compost are you spreading per acre?


    • Hello Rich! Your first paragraph – I’ve been pondering on that for a while. Excluding some of the native prairie perennial grasses, I’m questioning whether perennials are better than annuals when it comes to root mass –> organic matter.

      Our pastures are cool season mix with clovers, mostly orchard grass. They have never produced thick biomass (i assume the roots mirror above ground growth) like our annual cover crop fields have. When i flip up the pasture grass, the roots are skinny with no soil adhesion. As you know, sorghum sudan has incredible root mass, a lot of annuals do. This gets to why we’ve been rotovating our pasture fields and planting several cycles of annual cover crops before we go back to pasture again. The annuals really seem to do something in one season that 4 years of pasture have not. Maybe it would be different if we had grazing livestock on the grass, but I’ve heard that annuals also respond to grazing – sending down deeper roots, growing back extra fast, etc.

      Like your johnsongrass and giant ragweed, i’m starting to think that plant bulk (biomass and rootmass) is key, no matter if the plant is perennial or annual.

      Lots of permaculture-type people love perennials and hate annuals, but i wonder if what they’re really hating is continuous annual monocultures and tillage. I think diverse annual cover crops with no-till management hold tons of promise.

      Compost – we’re aiming for a thin spread of 1 ton/acre.


  2. Posted by Britt on December 11, 2012 at 12:43 pm

    I love the chart and the blog! I am a year or two ahead of you on putting cattle out to pasture and a year or two behind you on learning about the importance of soil and OM.
    The chart really is nice to see, as it gives me hope, that OM can be increased in my soil in my life time.
    Has the OM changed your PH?
    Keep up the blog and the “farm experiment” it is a big help to those of us on the learning curve.
    Thanks Britt
    Ross Land and Cattle
    Sulphur Springs, Teaxs


    • Thanks Britt! Glad to hear this gives you hope. pH – no, with our extremely sandy soil and wet climate, we have lots of mineral leaching, so our pH bounces around a lot. We’d probably need loads more OM to stop that from happening. Hopefully we’re on our way there. Best of luck with your cattle!


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: