Save the Microarthropods! Rethinking Tillage and Rotovating

We’ve gone from tillage-happy to tillage-doubtful.  We learned some things about tillage at the December 2011 Acres USA conference that really resonated with us, so we’re reconsidering our plowing down cover crop strategy in order to nurture a key part of the soil food web…

Rotovating in late August 2011

Up to now, our strategy for improving our sandy soil’s fertility involved growing massive cover crops to maturity and then plowing them down every spring and fall.  The “plowing down” involved using our rotovator (a very wide garden tiller) to incorporate most of the plant tissue into the topsoil so it could stimulate soil biology and eventually break down into organic matter.  At the Acres conference, we got confirmation from several speakers that this was the best method for improving soil’s biological fertility, especially if the plants are mature and lignified (more brown than green).  It felt great to hear this because it fit exactly with our plan!  Then we heard Jill Clapperton speak.  She was the rhizosphere ecologist for Canada’s agriculture department, and her research really compelled us to reconsider tilling so often.  Here’s why:

Lots of Tillage Hurts the Soil Animals in Middle of Food Web

Soil Food Web

The bottom of a very simplified version of the soil food web starts with bacteria and fungi, which are the primary digesters.  The middle group is the small animals, and they eat everything!  They prey on each other, bacteria and fungi, and plant residue.  This group consists of microarthropods (mites), earthworms, nematodes, enchytraeids, and some protozoa.  The top of the simplified food web is the larger animals that live on the soil surface like springtails, beetles, and even mammals like field mice.

Clapperton talked about long-term research results that showed some of the small animals in the middle of the food web disappearing after five years of tillage.  She said most of the small animals, especially the microarthropods, make their homes in the top few inches of the soil, and when tillage repeatedly destroys their infrastructure, the animals just leave.  The microarthropods cannot live in such an unstable environment.

Plants pick up and assimilate nutrients that have gone through soil’s biological system much better than nutrients from fertilizer.  For this reason, it behooves us as farmers with the goal of growing top quality grass to nurture the soil’s biology as much as we can.  We’d love to have the microarthropods on our farm just because they’re pretty amazing animals, but more than that, they are a very essential part of a vibrant soil food web.

Microarthropods are Voracious Predators

Macromite's Blog selection of soil mites, springtails, and Parajapyx. http://macromite.wordpress.com/2009/04/29/a-menagerie-of-microarthropods/

The animals in the middle of the food web are soil’s predators and recyclers.  This video shows two soil mites battling over a juicy springtail.  If we saw large, familiar animals trying to rip apart another animal like this on a regular basis, we’d probably have a whole different view of nature!  But violent predation like this happens all the time in the soil, and the soil’s health, and therefore the nutritious quality of our food, depends on it.  Here’s how:

The microarthropods chew up bacteria and fungi, poop them out, and regenerate the whole food web cycle in a very positive way around plant roots.  Without the good, natural predation check, the bacteria and fungi proliferate too much and start competing with plants for nutrients that plants need to grow and thrive.  Soil bacteria and fungi will beat out plants every time for nutrients if they’re allowed to do so.  Therefore, predators like microarthropods are essential for healthy, vibrant plants.

Microarthropods Stimulate the Soil Food Web

The microarthropods also help out bacterial and fungi.  They eat everything, including each other and larger pieces of plant residue.  Everything they eat is pooped out in new, much smaller particle sizes that are now accessible to bacteria and fungi for food.  This stimulates the bacteria and fungi to multiply at a good rate, in turn feeding the whole system.

Tiny Oribatid mite: Synchthonius crenulatus (Jacot) on a Times-Roman 12 pt Period. At http://macromite.wordpress.com/2009/07/01/full-stop-on-canada-day/

So, the middle of the food web is essential to healthy soil and therefore, high quality grass.  If repeated tillage makes them go away, we’re going to stop.

Our New Plan

Instead of rotovating our cover crops into the soil every spring and fall, we’re going to instead mow at the right time to kill them.  Clapperton advocates mowing because the clippings act as a good armor for the soil, and they insulate the soil from temperature extremes.  This helps the soil food web stay active during the hottest, driest times of the year.  She also said plant roots are soil’s most available form of organic matter.  Roots leak carbon and nitrogen compounds constantly to stimulate beneficial bacteria and fungi.  When the plant dies, the roots decompose into organic matter, and the tunnels left behind are great for air/water infiltration and for providing movement channels for earthworms and other animals.  Another disadvantage of tillage is that it collapses a lot of these tunnels.

We’re not going to sell our rotovator.  We’ll use it this spring to rough up our 20 acres of perennial pasture so we can give our new cover crop cocktail a good chance to grow.  We’ll rotovate very lightly and probably leave a lot of the grass standing.  We’ll then plant successions of cover crops, and then plant our final perennial pasture mix for grazing.  We might not ever need to rotovate our fields again, unless we want to kill the perennials again to do some crop rotation, or we detect soil compaction problems (unlikely in our very sandy soil, with the help of cover crops).

We hope that our new plan will help our soil thrive.  Giving up repeated tillage will hopefully give our farm a very healthy, complete soil ecology that includes the very necessary predators and recyclers and will also help maintain good soil structure with intact earthworm channels.

Most of the info in this post came from Jill Clapperton’s two presentations at Acres.  Audios of her presentations are available here.

5 responses to this post.

  1. Posted by Rich on February 19, 2012 at 6:27 pm

    I think I have commented before about ‘pasture cropping’ and ‘no-kill cropping’, but it sounds like it is similar to what you are doing on your farm.

    Some of these links can better explain the method than I can:

    http://www.regional.org.au/au/stipa/2001/p-05.htm

    http://www.pasturecropping.com/

    http://www.pasturecropnokillcrop.com/

    http://www.grainandgraze.com.au/library/pdf/81/75.pdf

    Basically, the method involves drilling cereals (wheat, oats, rye, etc.) into perennial grasslands to provide both livestock grazing (both before planting and after planting) and the option of a grain harvest with lower inputs. As a bonus, native warm season grasslands can be restored with these techniques.

    For the last few years, I’ve experimented with something that is close to no-kill cropping by drilling winter wheat into both native grass pastures and bermuda grass pastures. In the first year, both were cut for hay in the summer, then drilled in the fall, grazed with cattle in the winter, and the bermuda grass/wheat pasture was cut for hay the following spring.

    The second year (after drilling that fall, etc.), I was able to harvest the grain in the bermuda grass pasture (which was pretty exciting from a farming viewpoint).

    I don’t have anything to prove the difference, but the grass looks “different” in these areas, and the cattle seem to graze it differently.

    Even if you never plan on harvesting any grain, the methods might apply to your farm or might help reestablish perennial grasses or might just make it possible to feed some livestock over the winter with a little less hay..

    It is interesting enough, that if I can figure out more of the details, I could see converting most of our cropland to a ‘pasture cropping’ system in the future (it might work even better in converted cropland that in an established pasture for all I know).

    Reply

    • Hi, Rich. Thanks for your info, I will check out the links. i read somewhere, i think in one of Joel Salatin’s books, about a wheat farmer that drilled all his wheat into perennial pasture, like you mentioned. He brought cattle onto the pasture at the right time to eat the perennial grasses down to the ground, then drilled the wheat, then just before wheat emerged, brought the cattle back again to knock the grass back a second time. The farmer said he got the same yields as wheat farmers in his area, and he used no fertilizer. I guess letting all the perennial roots stay alive with all the associated soil life is a benefit, or at least not a detriment, to the wheat crop?

      I wonder if we even need to rotovate our pasture before we plant our cover crop. We’re planting about 60 lbs of cover crop seed per acre, and I want to give every seed a good chance. Our bushhog’s lowest setting leaves about 8 inches. Do you know of any mowing equipment that cuts grass near the ground? I could probably rent it from somebody.

      Reply

      • Posted by Rich on February 20, 2012 at 5:42 pm

        I first heard about the concept in a Holistic Management International newsletter, which had a column about the Australian technique. I don’t know if it will produce yields as high as a conventional field, but the profits might be as high or higher because of the reduced input costs and more total grazing available. If the cool season grassy weeds were controlled (with herbicides, etc.) the yields could probably come pretty close with greatly reduced input costs.

        That’s basically how I did it, except I baled bermuda hay in the summer, let the cows graze the regrowth in early fall for about a week after I had weaned their calves, then took them off and drilled the wheat the next day. The first freeze of the year came about a month later and the bermuda went dormant for the winter and the wheat was left to grow until January when I let the cows back on. I’ll probably take them off around the first of March so I can either get a grain harvest or cut it for wheat hay about April/May. The combination of dormant grass and the wheat seems to be a good ratio of dry matter and green matter because the cows always seem to “perk up” when they start grazing it (I wish I had more pasture planted this way).

        Besides that, all I know is that almost everybody that drove by did a double-take last year at the sight of me combining the little bit of wheat that I pasture cropped out in a bermudagrass pasture.

        There is another link that has some details about overseeding pastures with a
        low-input system that might apply to you at:

        http://www.noble.org/Ag/Forage/overseeding/Index.html

        “…Our bushhog’s lowest setting leaves about 8 inches. Do you know of any mowing equipment that cuts grass near the ground?…”

        Something like a sickle bar mower or a disc mower (like you were cutting hay) will cut pretty close to the ground. I’m unsure, but I think that some disc mowers (or sickle bar mowers) will leave a windrow after the grass is cut so that’s something you would need to check if that would be a problem (after all they are typically used for making hay).

      • Very cool! You know you accomplished something when drivers-by brake and turn their heads.

        Thanks again for the links you provided. I loved the Colin Seis et al videos in the pasture cropping link. That method makes a lot of sense to me – I need to think about the pros and cons of rotovating versus pasture cropping for converting our pasture into a big cover crop. Pasture cropping can save us a lot of rotovating labor time and save $ too, especially in not having to replant perennial grasses down the road. Our pasture grasses usually start to poop out in June as temps rise, maybe we could wait to drill the summer cover crop seed until then. But, we also wanted to use rotovating as a chance to spray beneficial biology and other goodies onto the soil. We also wanted to kinda start over because our pastures are pretty much just orchard grass and timothy – we never got legumes or broadleaves to grow. I will check into the sickle bar mower or disc mower. Hubby said he was afraid they’d get wrecked by all our groundhog holes!

  2. [...] also stimulate the middle of the soil food web, arguably the most important part – the mites, earthworms, and other recyclers that prey on bacteria and fungi to keep them in a [...]

    Reply

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 )

Twitter picture

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

Facebook photo

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

Google+ photo

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

Connecting to %s

Follow

Get every new post delivered to your Inbox.

Join 65 other followers

%d bloggers like this: