A Fertility Mystery



Oat/Barley field with a creek intersecting.  Notice the dark-green line in both fields with plants to the left of the line darker-green than plants to the right of the line.  Why?

I will explain how the field was managed.  Last year was a wet spring and I was unable to plant this field to oats like I had planned in April.  By the time I could work the soil around the first of June I decided to plant corn, instead.

I had read about grazing standing corn in the book, “Grassfed to Finish,” by Allan Nation.  Since I had low expectations about this field’s yield potential due to the late planting date, I decided this was the year to try this radical idea.  Even Citygirlfriend knew this was crazy.

It turned out ok, though.  I grazed eight steers for eight weeks starting in July when the corn was waist high and ending in August with the corn eight feet tall.  The steers gained well, about two lbs. a day, but that was no better than the steers that were grazing permanent pastures and alfalfa/grass hay fields.  So, since the gain was no better and the cost was higher to graze corn, I am not planning on grazing corn anytime in the future. 

The dark-green line is where I chopped down the corn and put up a single-strand electric fence.  I then cross-fenced and gave the steers a half-day to a day allotment at a time.  I also had a round bale of hay available so the steers would never accidentally run out of feed.

After the steers were butchered in August, I took down all the fencing and no-tilled oats into the bare ground.  I didn’t want the soil exposed to rain, sun, and wind.  So are you picturing how it looked?  To the right of the line was a corn field, and to the left of the line was oats.

We harvested the corn in October.  At this point, the oats were about knee-high.  We then grazed the field with the cows.  They ate much of the corn stalks and grazed the oats right down to the ground.

I disced the entire field this spring and then planted oats/barley and didn’t think twice about it.  And then I looked at it one day and noticed the line.  I knew I had to take a picture and present it to you.

The dark-green color indicates higher fertility and that higher fertility is probably more available nitrogen.  Why is there more nitrogen available?  What are the management differences?

The steers grazed and deposited their manure.  However, they wouldn’t have deposited their manure evenly.  You can see where cows deposited their manure on the right side as it shows up in darker-green clumps of forage.

I planted an oat cover crop.  Cover crops are supposed to add nitrogen to the soil.  Would it add nitrogen the next summer even though it was grazed off the previous October?

There was very little carbon on top of the soil this spring.  To the right of the line was corn stalks.  As microorganisms break down corn stalks, (carbon), nitrogen is used.  Maybe more nitrogen was available to the left of the line because of the lack of corn stalks.  This is where I’m placing my bet.

What do you think?  Is it one of these theories, or something else?  Your comments are welcome.

One Response to A Fertility Mystery

  1. buggyridgefarms says:

    “I planted an oat cover crop. Cover crops are supposed to add nitrogen to the soil. Would it add nitrogen the next summer even though it was grazed off the previous October?”
    All cover crops to not add nitrogen to the soil. Many use up excess N. They will return N if plowed under for green manure.

    Oats are not a legume. Therefore no nitrogen would be transferred from the bacteria in the root nodules to the soil.

    High carbon residue certainly will use up available soil N being broken down.

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