On Tuesday I went to a field day on no-till tobacco production. Tobacco is a warm season solanaceous crop -- like tomatoes or peppers -- that is usually transplanted into freshly-tilled soil in late spring. After fall harvest the remaining stubble is usually left to decompose in the bare soil until the next spring, when the plow comes around again.

In recent decades people have started to recognize that soil suffers when it's left bare, or routinely disturbed by cultivation. Bare soil is susceptible to wind and water erosion. Cultivation destroys the soil structure, further increasing its susceptibility to erosion. Cultivation also introduces a lot of oxygen to the soil very quickly, resulting in a brief boom in the microbial population, and a rapid depletion of the soil organic matter that the microbes eat. (Organic matter is a valuable component of soil because it holds on to the nutrients and water that plants need; soil microbes help release nutrients into the soil solution, making them accessible to plants, and exude sticky material that holds soil particles together, reducing soil's susceptibility to erosion.) In the long term, cultivation reduces soil organic matter content and soil microbial populations.

No-till grain production is now fairly common, but very few farmers grow transplanted crops, like tobacco, without cultivating. It turns out that one of them happens to be a sixth-generation Kentucky farmer who took the 'Introduction to Sustainable Agriculture' course that I co-taught last semester. The field day was at his farm.

We saw a nice demonstration of how soil that hasn't been tilled holds together better than soil that is routinely cultivated. Clods of soil collected from sections of the farm that hadn't been cultivated for 10 years were suspended in water next to a clod collected from a routinely cultivated section. You can see the clod on the left disintegrating while the clod in the middle holds firm:

After harvest the land is seeded to a winter cover crop that protects the soil from winter erosion, saves nutrients that might leach out of the soil in the absence of plants, and feeds soil microbes. The farm is experimenting with different winter cover crop mixes, most of which include a nitrogen-fixing legume species.

At the Kentucky State University Research and Demonstration Farm we often use a mixture of rye, which grows quickly and out-competes weeds; and hairy vetch, which fixes nitrogen and twines its way up the rye. Here are the two plants together, towering over a yardstick:

Nitrogen-fixing crops like hairy vetch harbor bacteria in their roots that are able to convert nitrogen gas from the air around us into nitrogen that is available to plants. A winter cover crop of hairy vetch can add more than 100 pounds of nitrogen to the soil per acre (Kansas State University pdf), enough to feed a nitrogen-demanding crop like corn.

Of course organic farmers have been using nitrogen-fixing cover crops for decades; the organic standards don't allow synthetic nitrogen fertilizer. Conventional farmers have known about the advantages of cover cropping, but using nitrogen fertilizer has long been cheaper than managing cover crops. Soaring fertilizer prices have changed that. Suddenly tactics like no-till production and cover cropping aren't just better for the soil; they're cheaper, too.

Michael Bomford provides research and extension services related to organic agriculture and small-scale renewable energy production through Kentucky State University's Land Grant Program.

Over the weekend a group of thinkers working with Post
Carbon Institute have been discussing the mineral content of rain. Often
when we discuss minerals and rain we are talking about the manner in which
minerals and inorganic nutrients are readily leached from the soil. Leaching is when minerals are not able to hold
in the soil and are thus washed out by the natural flow of groundwater. A soil’s
tendency to leach is influenced by the way that the soil is tilled, cropped,
and fertilized.

For instance, inorganic fertilizers provide crops with plant
available nutrients in the form of chemicals like nitrate (NO₃^-).
The problem is that nitrate readily washes out of the soil if the plants are
unable to utilize it before heavy rains. Many farmers are beginning to realize that
heavy fertilizer application in the fall amounts to a waste of money since a majority
of the nutrients are lost by spring due to sever washout by winter rains or
spring snow melt.

Leaching of minerals also occurs when soil is left bare to
face winter rains. In this case, leaching is accompanied by a loss in top soil
from the process of erosion. Imagine rain drops as tiny explosions on bare
soil, blasting minerals loose, collecting in water particles, and flowing away
as surface runoff.

Fortunately, farmers do not need to resign to the fact that
rains always mean a loss in minerals and nutrients. By cover-cropping and the
addition of compost, a farmer can protect the soil from direct rainfall and increase
the organic matter in the soil in the form of root biomass. Roots and organic matter
create a healthy habitat for soil microbes that play a key role in mineralizing
soil nutrients and forming soil aggregates that resist leaching.

One great benefit to having a diverse soil food web of
fungi, bacteria, and protozoa is because organic minerals are “sequestered” in
the biomass/bodies of microbes and recycled through in their metabolic
processes. Instead of washing out of the soil, the minerals actually become the
body of bacteria and fungi! In a series of food chain and energy exchanges the
minerals in the soil are converted from one form to the next; changing from plant
detritus to the body of a soil organism, then to metabolic wastes of that
organism and into plant available forms of, and then consumed and incorporated into
the body of another soil microbe. All these changes occur in and around in the
rhizosphere (root-zone) of plants, and demonstrate an interconnected web of
energy and nutrient cycling and nutrient retention.

Also consider the fact that bacteria and fungi create a natural
glue that sticks to everything. Through the production of “glomulin”, nutrients
are retained and soil aggregates are formed. As organic matter is decomposed, the
biology in the soil help to form stable negatively charged humic (humus)
molecules which bind together with positively charged cat ions, electrically holding
minerals and preventing them from leaching. Important cat ions retained in
colloidal humus particles include: calcium, iron, magnesium, potassium, sodium,
and copper.

As you can see, there is a lot happening below the
soil, and farmers and gardeners have an opportunity to utilize cover crops, compost,
soil biology, and appropriate timing of fertilization to prevent soil erosion
and leaching of nutrients.

Broadcasting a Cover Crop of Crimson Clover in October to Protect Bare Soil from Winter Rain

Recently Sown Cover Crop of Legumes mixed with Rye and Barley Provides Root Biomass and Use Boilogy to "Fix" Nitrogen from the air

For years, many farmers have applied fungicides to battle against certain
species of fungi that devastate their crops. While this method has appeared
necessary for years, a revival is occurring where farmers are looking to work
with nature in place of a “no-hold barred” war against it. Indeed, it is
possible (and profitable) to use soil biology to fight pathogenic fungi and to unlock
the stored nutrients in the soil and secure fertility naturally.

I have recently returned from Southern Oregon where I visited Mycorrhizal
Applications, located in Grants Pass,
Oregon. This company was founded
by scientist Dr. Mike Amaranthus who studied soil biology for over 20 years at Oregon State
University. This company believes
that a diverse and healthy web of soil microbes is the key to the future of
fertilizer. Thus, Mycorrhizal Applications distributes beneficial bacteria inoculants
and researches and produces significant quantities of specialty-fungal inoculants.
This is no fringe practice as is demonstrated by their international consumer
base.

In the Dryland Demonstration in Willits, CA,
we too are planning on using mycorrhizal inoculants to support our grain crop
as the fungi mineralize phosphorous, calcium, and iron provide and transport it
to the roots our wheat. These fungi additionally help the plant obtain and
retain water (crucial for dry farming). To apply these microbes we will coat
our grain seed with fungal spores and then broadcast the wheat into the soil.
This concept may be new to a lot of people and so the following blog is dedicated
to addressing:

"What Are Mycorrhizae?"

The word "mycorrhizae" literally
means "fungus-roots" and defines the close mutually beneficial
relationship between specialized soil fungi (mycorrhizal fungi) and plant
roots.

About 95% of the world’s land plants form the mycorrhizal
relationship in their native habitats. It is estimated that mycorrhizal fungal
filaments explore hundreds to thousands more soil volume compared to roots
alone.

Benefits include:

• Improved nutrient and water
  uptake
• Improved root growth
• Improved plant growth and
  yield
• Reduced transplant shock
• Reduced drought stress

In some cases, the fungi live inside the root (endo-mycorrhizal) and in other
cases it lives on the outside of the root (ecto-mycorrhizal). In both
instances, the organism is capable of providing nutrients and water necessary
for plant growth. In turn, the plant (via photosynthesis) provides necessary
sugars to sustain the growth of the fungi.

Follow
this link to read the FAQ
section from Mycorrhizal Applications where you will learn more about these
exciting creatures that are capable of unlocking the fertility of the soil naturally.

The Sebastopol Demonstration Energy Garden is located within the Sebastopol Sandy Loam series, which is described as a moderately fertile, well drained soil. Permeability is moderately slow in the subsoil, runoff is medium, and the hazard of erosion is moderate.

Soil texture is determined by the relative proportions of sand,
silt and clay and organic components that soil has. Sand is the largest particle, silt particles are smaller than
fine sand but can still be seen by the human eye, and clay particles are
microscopic.

Sandy soil—tends to be very
light and dries out swiftly. Water drains very quickly and makes the
soil easy to dig. It is the first to warm up in the sun.

Silt soil—retains moisture and feels slippery when wet. Retains nutrients better than sand but does not dry out as quickly.

Clay soil—a
very heavy soil, it holds moisture for long periods of time when wet
and dries hard as a brick. Clay soil retains nutrients and is very
fertile but is heavy, sticky and very hard to dig. It is the last to
warm up in the sun.

Loam soil—the ideal
soil texture, it is composed of sand, silt and clay. The ideal loam
soil contains 40% silt, 20% clay and 40% sand and organic matter. Loam
is a separate category because none of its compontents account for more
than 50%.
Loam soils are ideal for most plants, although many plants grow well in non-loan soils.

8/3/07 8/11/07

So as to test soil texture, we performed a comparitive test of samples from different parts of the garden.

A) Soil sample from path; untreated

B) Soil sample from bed; ammended with mango mulch

C) Sample of purchased compost; mango mulch ammendment

D) Sample of the compost developed on site.

We filled recylcled mason jars a quarter full with a portion of each sample, added water and a couple drops of biodegradable dish washing soap, and allowed them to settle for a week. Based on the thickness of each settled layer, we determined the proportions of sand, silt, and clay in our soil.

Using a basic LaMotte soil test kit and a soil auger, we tested each sample's pH, and the quantities of available nitrogen, phosphorous, and potassium.

The pH of our soils ranged from 6-8 and it appeared that the more organic materials that the soil contained, the more alkaline it was. The phosphorous content of our samples ranged from medium to high (75lb/acre-100+lb/acre).

The nitrogen content of our compost is tremendously high compared with the other three samples which could be expected because our chickens are allowed access to the piles. Aside from sample D, merely trace amount of nitrogen were present. The potassium content of our samples correlated with the proportion of organic marterial in the soil. The purchased mango mulch expressed the highest content, followed by the compost we have developed.

Nitrogen- stimulates leaf and stem growth. Nitrogen deficiency
causes reduced growth and pale yellowish green leaves. The
older leaves turn yellowish first since the nitrogen is readily moved
from the old leaves to the new growth. If the soil is cold and wet,
nitrogen in the soil is not as available to the plants. Excess nitrogen
may cause potassium deficiency.

Phosphorus-is important in the germination and growth of seeds, the
production of flowers and fruit, and the growth of roots.
Phosphorus deficiency causes reduced growth and small leaves that drop
early, starting with the oldest leaves. Leaf color is a dull,
bluish green that becomes purplish or bronzy. Leaf edges often turn
scorched brown. Excess phosphorus may cause potassium
deficiency.

Potassium- promotes general vigor, disease resistance and sturdy growth. Potassium deficiency causes stunted growth with
leaves close together. Starting with the older leaves, the leaf tips and edges turn scorched brown and leaf edges roll. Excess
potassium may cause calcium and magnesium deficiencies.

Using a disecting microscope at a magnification of 30x we analyzed the
contents of each sample, here looking for the amount of sand, clay,
silt, and organic materials. At this magnification the mycelium of
fungi was visible.

A. B. C. D.

A. Mostly sand w/ small amounts of silt

B. Finer sand particles and more silt than A.

C. Mostly organic materials. Mycorrhizae present among other mycelial growth.

D. More silt than A and B. Mycellial growth present as well as organic remnants.

Using a microscope at a magnification of 600x we analyzed the biology of each soil sample.

Without
a doubt conventional agricultural practices, including the use of inorganic fertilizers,
chemical weed and pest management, and intensive tillage disrupts the life of
the soil. Organic matter is lost through tilling practices because bacteria
feed on newly available carbon and nitrogen, releasing the carbon in the plant
matter as carbon dioxide into the atmosphere. Applications of quick release chemical
fertilizers such as anhydrous ammonia actually dissolve organic matter and kill
soil microorganisms on contact. It takes weeks and months for bacteria and
fungi to reestablish populations after a single application of anhydrous
ammonia.

It
is important to understand that innumerable microbes participate in an
interconnected web of interactions above and below the surface to decompose
organic matter in the soil and both store it and make it available to the
plant. These microbes include bacteria, protozoa (amoeba and flagellates),
fungi, nematodes, micro arthropods, and of course earthworms. Each of these
creatures feeds on plant matter and one another, fertilizing the soil with their
wastes, consuming plant debris and even mineralizing parent matter from rocks
thereby making these nutrients available to the plant to take in from the
roots. In soils with low organic matter or soils that have been salted through
the use of inorganic fertilizers, the biology in the soil is severely disrupted
and the chain of interactions has been broken. Similarly, in areas where
pesticides have been used, non-target organisms are damaged or destroyed,
affecting the biological diversity of the soil. As mentioned above, if there is
not a complete web of biology in the soil then organic mater will be lost as
the bacteria respire. However, if we have a complete food web the process
occurs differently. Instead of losing the carbon, bacterial feeding nematodes
or amoeba consume the bacteria. As their populations increase they become new
biomass in the soil adding both structure and the ability to retain nutrients
as they become the composition of their very bodies. Nutrients become available
to plants as these organisms deposit their metabolic wastes into the area of
the roots.

If
we are to have truly sustainable agricultural practices we need to start at the
soil. An understanding of the processes and needs of the soil biology will
allow us to maintain the health and vitality of the soil while reducing the use
of inorganic fertilizers. Many sound agricultural models that have proposed the
extensive use of compost and have often touted it as the perfect addition to
the soil. Compost is rich in nutrients, humus, has a balanced pH, and is a
medium for billions of beneficial microorganisms including bacteria and fungi.
These organisms form symbiotic relationships with the root structures of the
plant (rhizosphere) and even protect the plant from weeds, disease, and harmful
microbes as established populations of competitive and beneficial biology over
compete against the “baddies”.

After
tilling the soil it is a good idea to follow up with an application of
activated compost tea. Activated compost tea uses compost as a microbial
medium, extracts the microorganisms into water, and promotes the rapid
reproduction of bacteria and fungi by feeding a nutrient mix. Then the water is
aerated for 12-24 hours (depending on the size of the brew) to make sure that
the microbes in the compost have available oxygen and remains aerobic as the
organisms reproduce. A nutrient mix acts as a food for the growing microbes and
a crucial ingredient to tea. Our selection of nutrient mix will influence the
type of organism we want to select for. For instance, if we want to feed
bacteria we emphasize sugars, a protein source, and provide extra minerals. If
we want to create an environment suitable for fungi we add more complex foods
including fish hydrolosate, soluble kelp, and protein meals such as feather
meal or whey.

Compost
tea has a very short shelf life and it is important that once you are done
brewing the tea that you spray it onto the soil within four hours. If you wait
too long, the increased population of microbes may consume all the remaining
oxygen in the mix and making the tea anaerobic, and therefore, potentially
harmful to the soil.

We
recently had the opportunity to apply compost tea to the soil following our
attempt to open the soil at Brookside Farm with walk behind rototillers. The
mix was brought down to the farm site from David Drell, who had created
excellent compost and agreed to brew the batch of tea for us. After the final
cross-cut pass was made I donned the backpack sprayer and diluted the mix to 1
part tea and 2 parts un-chlorinated brook water. I then set out to apply a soil
drench. Typically 20 gallons of tea is used for one acre if you are doing a
soil drench but since we had only about ¼ acre to cover 5 gallons was
appropriate. I simply walked in rows and sprayed the tea onto the soil. The
intention is that the microbes will begin to establish a healthy population to
our already healthy soil. Furthermore, we hope that they will assist in the
decomposition of the newly incorporated sod.

There are many symbiotic relationships in nature. Plants and herbs can be grown together to enhance growth, helpful predator insects are attracted by a specific flower to combat a specific crop pest, and even bacteria interact with special leguminous plants to transform nitrogen into a form that plants and animals can use. In this blog, I would like to focus on nitrogen fixation, a very special relationship between bacteria, plants, the soil, and the atmosphere.

In brief, nitrogen fixation is a process where inert N2 (nitrogen gas) is converted into usable ammonia (NH3). This form of nitrogen is important to plants and animals as it helps to manufacture amino acids, proteins, nucleic acids and other nitrogen-containing components necessary for life.

Nitrogen fixation by legumes is a partnership between a bacterium and a plant. The plant supplies all the necessary nutrients and energy for the bacteria. Examples of legume plants include Alfalfa, Fava Beans, Vetch, Peanuts, Soy Beans, and Clover. Other plants benefit from nitrogen-fixing bacteria when the bacteria die and release nitrogen to the environment or when the bacteria live in close association with the plant.

A common soil bacterium, Rhizobium, invades the root of a legume and multiplies within the root cells forming bump-like masses called nodules. Within these nodules, nitrogen fixation is done by the bacteria, and the NH3 (ammonia) produced is absorbed by the plant. A way to determine whether or not nitrogen fixation is occurring in a plant is to investigate the roots. When fixation occurs the nodules turn from white or gray to pink.

It is a common misconception that nitrogen fixing plants deliver nitrogen directly to the soil via their root systems. The following is from the W.C. Lindemann, a Soil Microbiologist from New Mexico State University:

The amount of nitrogen returned to the soil during or after a legume crop can be misleading. Almost all of the nitrogen fixed goes directly into the plant. Little leaks into the soil for a neighboring non-legume plant. However, nitrogen eventually returns to the soil for a neighboring plant when vegetation (roots, leaves, fruits) of the legume dies and decomposes. When the grain from a grain legume crop is harvested, little nitrogen is returned for the following crop. Most of the nitrogen fixed during the season is removed from the field. The stalks, leaves and roots of grain legumes, such as soybeans and beans contain about the same concentration of nitrogen as found in non-legume crop residue. In fact, the residue from a corn crop contains more nitrogen than the residue from a bean crop, simply because the corn crop has more residues. A perennial or forage legume crop only adds significant nitrogen for the following crop if the entire biomass (stems, leaves, roots) is incorporated into the soil. If forage is cut and removed from the field, most of the nitrogen fixed by the forage is removed. Roots and crowns add little soil nitrogen compared with the aboveground biomass.

Taking the implications of the above paragraph seriously, it is important to till in a legume cover crops in order to utilize the nitrogen fixed from the atmosphere. This process is similar to carbon sequestration process mentioned in the previous blog. When we incorporate plant matter back into the soil we feed the microbial life of the soil foodweb. These microbes mineralize nutrients in the soil, aid aggregation of soil particles, and help to form humus that improve overall health and vitality of the soil.

To read W.C. Lindemann’s paper and to learn more about nitrogen fixation check out the following links:

http://www.cahe.nmsu.edu/pubs/_a/a-129.pdf

http://overton.tamu.edu/clover/cool/nfix.htm

At the beginning of November, initial soil preparation began at the Brookside Farm. Soil tests were taken and the results indicated that the soil is teeming with microbial life and lacks nothing in regards to nutrients for the growth of healthy crops. The soil type we are working with is “Felix loam”. Because loam is evenly composed of sand, silt, and clay it has the duel advantage of being able to both hold water and drain when there are no significant water inputs. This loam compacts less than clay, while it containing more nutrients than sandy soils.

We are beginning with healthy soil and intend to maintain it through organic farming methods including cover cropping, crop rotation, and compost teas. Furthermore, the aim is to back away from machine powered soil cultivation and harvest methods which have the disadvantage of soil compaction and large monetary investment in a non-sustainable method of farming.

The acre at Brookside Elementary was an unused baseball field. The infield was markedly more compacted than the sod-covered outfield. Initially, there were doubts that the cover crops would be able to make a dent in the compacted soil that had been turned over only about 2.5 inches. These doubts have been put to rest as the winter rye and barley are beginning to make headed way. Clover and fava were also seeded and they too are beginning to spout. The overturned outfield is already showing significant clover growth.

If you want more information about the soil at the Willits Energy Farm, check out the Brookside Soil Report.

Winter Rye Cover Crop

Barley Cover Crop Growing in Overturned Sod

Crops Sprouting in Overturned Sod and Compacted Infield