This issue’s Homestead Security column continues our series, Oil to Soil and Back Again. Part I (“Rapid Topsoil Formation in the Solar Age”) appeared in our Fall 2009 issue; Part II (“Harvesting Value from Your Leach Field”) was published in our Stick Season/Holidays issue (November 2009).

Highlighted here are few lesser-known soil-building strategies that are of particular relevance for the post-oil homestead and small farm.  I have not attempted to cover the most common forms of soil building such as composting, as there are ample resources available on such topics.
 
Cover cropping and winter cover

Cover cropping during the growing season as part of good crop rotation will probably be considered standard practice in life after the cheap-energy economy.  Peak oil holds a future in which imported growing media and nutrients in the form of soil, manure and other fertilizers will be increasingly expensive and/or unavailable.  Cycling fertility on site perpetually will be crucial in a post-peak future and will determine, in large part, the economic success of a farm and viability of a homestead.  

Since nitrogen is the most often-relied-upon off site input, producing (or harvesting) nitrogen on site via fertility farming will be central.  Indeed, home and farm landscapes in general should be thought of as nitrogen-capturing nets, sopping up atmospheric nitrogen and scavenging excess soil nitrogen for plant growth and soil organic-matter production.  Nitrogen-fixing plants such as clover, vetch, pea, and myriad perennials are components of this system, as are animals; land committed to these resources represents a significant portion of the productive acreage in a regenerative landscape.  This is why permaculturists are fond of planting at least one nitrogen-fixing plant for every “feeder” plant such as a fruit tree or berry bush. They serve as the fertility factory in the landscape, reducing or eliminating the need for fertility importing from off site.

It’s surprising how many organic home gardeners, and even organic farmers, tend their crops carefully throughout the season only to clean out the garden/field at the end of the year and leave exposed earth, spreading not a single pound of cover-crop seed, leaves, straw, hay, or other mulch.  This simple task protects the soil from six months of rain, snow, and wind until the next gardening season.  Without such cover, bare soil loses its finest and best material to the percussion of rain drops, the leaching effect of snow melt, and erosion by wind.  In addition, a dormant season planting of cover crops fixes nitrogen and sends organic matter (via roots) into the soil, boosting fertility and soil health for little cost and effort.  Some covers also aid in optimizing phosphorous, micronutrient, and other chemical levels in the garden.  All cover crops contribute organic matter to the soil, the foundation of good soil and plant health.  

Spread cover crops the day the garden is cleaned out at the end of the season, rake it in if necessary (depending on species), water if needed, and turn in the cover as soon as possible in the spring if it does not winterkill.  Buckwheat is a favorite cover (though it doesn’t fix nitrogen), because it winterkills reliably.  There are many good resources for cover crops available on-line and in print form.  Seek out the most appropriate covers for your phase of land development, soils, climate, your particular cropping cycle, and other relevant aspects of the site’s system such as animal-forage needs.

Tall-grass grazing

Picture a 10,000-head mob of buffalo or wildebeest thundering across the plains of North America or the Serengeti.  Is healthy topsoil what comes to mind?  For most of us, steeped in conventional ecology and environmental science, the answer is “Hell no!”  Instead, we imagine ecological destruction from overgrazing and desertification.

The association between grazing animals and land abuse is not unfounded:  Poor grazing practices (not necessarily “overgrazing”) contribute greatly to the desertification of large areas of the earth, wrecking soil and water and leaving a high climate-change bill. But that’s different from the quick movement of densely packed animals through a landscape, as in the American West, Africa, and other places where deep-soil prairie lands and massive herds of animals co-evolved.  

Modern grazing is typified by low-density animal stocking, occupying the same land area over long periods of time. (Picture your typical Vermont pasture dotted with a few animals here and there.)  This is the opposite approach to regenerative grazing, which builds soil and grows the healthiest animals.  Innovative graziers have recently been realizing that high-density, very short rotations (the cycles naturally performed by grazing herds for millennia) is a far more productive approach to managing pastureland.  

Enter intensive tall-grass grazing, mob stocking, or whatever your preferred term may be for regenerating the landscape through the application of grazing animals.  When a large number of densely packed, heavy animals moves through a landscape quickly, occupying that landscape just once or twice a season, the following soil-building events tend to occur:

1. Tall grasses, with correspondingly deep roots, are grazed down to within a foot of the ground, but not completely down to the ground which damages the plant’s ability to rebound.  Plant roots dieback as a response to this pruning, leaving organic matter (carbon) in the soil strata.  The deeper the roots have penetrated, the deeper into the soil this organic deposition occurs.  And the taller the grass was before grazing, the deeper the roots were able to grow.  This is the organic matter/carbon-pumping stage in the system, where atmospheric carbon is transported into the soil by plants.

2. Densely packed animals drop nitrogen in the form of manure as they graze.  They also turn up clods of sod, allowing access for rainwater to bring the newly deposited nitrogen and biological activity (microbes in the manure) into the soil.  Think of cattle as an enormous living rotovator spewing nutrients behind it; that’s the action of a massive animal herd if allowed to move through, not loaf upon, a patch of ground.  Rains wash the fertility and biological inoculants into the newly broken up soil, where it can penetrate deeply and not run off of the landscape as it would more readily were the surface unbroken.  This is the fertilizing and soil biology-enrichment stage of the process.   

3. Grasses left standing six to 12 inches by the quickly moving herd rebound quickly and are allowed to grow to hip height or taller before the herd is brought back again.  This is the resting and re-growth/root-penetration stage of the system.  
Visit http://www.wholesystemsdesign.com/rapid-topsoil-formation/ for an animation of this process.

These three steps are the primary reason why vast areas of land have been improved and sustained, not desertified, by the presence of massive animal herds.  Modern “mob stockers” like Joel Salatin and Abe Collins are applying this understanding to ecologically (“biomimetically”) manage their animal herds for the multifunctional production of meat, milk, soil fertility, drought resistance, greenhouse effect reversal, and the many other benefits of healthier, deeper soils.  

The take-home points here for the modern homesteader or restoration farmer are the following:

•    Let it grow!  You can only build soil as deeply as you can get your plant roots to penetrate (what comes up must go down), so the taller you let your yard or pasture grow before it’s cut/grazed the more soil you’re making (and CO2 you’re sequestering).  Think of any areas in grass as pasture or vegetable gardens-to-be – areas where you want good soil.  An upshot here is that mowing, if you mow, wants to happen three to five times per year, not per month.  

•    To the extent that you can, manage your animals for short grazing periods, in tall grass. Plan the grazing rotations carefully.  

Keyline agriculture

“Keyline” activities, such as plowing and ditching, convey water from the valleys, where it collects, toward the ridges, which are the driest areas of the landscape.  Keyline agriculture was conceived of in the drylands of eastern Australia, largely by P.A. Yeomans, and it is especially powerful for regenerating arid lands.  However, it probably has strong applications in Vermont, where the combination of soil compaction, clay soils and steep sloping land create water-limiting conditions where precipitation moves across, not into, the soil.  If drought conditions become more consistent, keyline approaches will also be crucial for lower-angle landscapes.  

The biological climax and dieback action described in the tall grass-grazing section above is probably the most potent soil-building tool for application across very large areas of the planet, but its effectiveness can be limited by soil compaction and water availability.  Fortunately, soil compaction can be addressed by subsoil plowing via a Yeomans-style keyline plow.  Other keyline methods of agriculture are aimed at water capture so that the root-dieback action can occur in lands where significant slopes cause water to run off so quickly that only minimal amounts actually enter the soil. This water-managing aspect of keyline agriculture is foundational and addresses the inconsistencies in water availability across a field.  

At its fullest extent, keylining involves storing water high in the landscape, usually via a pond; subsoil plowing (which loosens the soil rather than turning it like a moldboard plow) in a slightly downward-trending pattern from the valleys out toward the ridges of a field, bringing water from the wettest areas to the driest; and flooding the landscape after a grazing rotation, distributing the manure/bio-inoculants across and into the landscape.  Think of a rain or flooding event washing nourishment across and into the landscape.  Since roots only want to penetrate relatively loose soil where oxygen and water are present, keyline agriculture leads with the water, mechanically allowing water to enter areas of the soil not previously available.  
Water leads, roots follow, soil organic matter is deposited, carbon is banked in the soil. Flood prevention, climate stabilization, farm fertility, drought resistance, crop nutrient density and myriad other benefits result.  Deep, healthy soils support resilient ecologies and culture – most other functions can only be built atop its solid foundation.