Subject: Experts Talk Soil at MOFGA Meetings (MOFGA = Maine Organic Farmers & Gardeners Association)

From: "Noreastah" <[email-masked]>
Date: Sat, 9 Sep 2000 18:23:55 -0400

http://www.mofga.org/mofgj00j.html

Experts Talk Soil at MOFGA Meetings
June - August 2000 Issue of Maine Organic Farmer & Gardener
by Jean English

Jerry Brunetti is the managing director of Agri-Dynamics, a soil and animal
health consulting company that also markets holistic remedies for animals in
Easton, Pennsylvania. At MOFGA and Cooperative Extension's Farmer to Farmer
Conference in November, he spoke about improving soil chemistry and soil
health through diversified cropping systems and amendments.

Working primarily with "Plain Folk" (Amish and Mennonite) dairy farmers in
Lancaster County, Brunetti finds that these farmers have to deal "as much
with overfertility as anything else." They have "good, high-calcium soils,"
but because of the high animal population in Lancaster County, they also
have an "overkill of phosphate and potash. Potassium will be taken up a lot
more readily than calcium, leading to cationic imbalances in the animals,"
said Brunetti. These imbalances "are not healthy."

Another problem in this area is that "the Amish like to get in their fields
early, so they leave the soil bare over winter. It's a challenge to get them
to look at cover crops."

Third, Brunetti finds that Lancaster County soils often "have the fertility
but it's not getting into the plant because of air, water or decay problems.
Air management, water management, decay management and fertility management
all affect one another."

Agri-Dynamics works with the Albrecht model of soil fertility, said
Brunetti, which calls for calcium to comprise 65 to 75% of the base
saturation; magnesium, 12 to 15%; potassium, 3 to 5%; hydrogen, less than
10%; sodium, less than 1 to 3%; and the rest, trace minerals. He recommends
testing the soil at the same time every year, "otherwise, soil temperature
and biological activity will affect the results." A soil test, added
Brunetti, "is a guide to see if you're going in the right direction. For
more precise information, tissue testing" is required.

Brunetti pointed out that sulfate, borate and nitrate are all negatively
charged ions, so they tend to leach. However, soils high in organic matter
tend to hold these better. "The only way to affect cation exchange capacity
is to add humus," he said.

Maintaining sufficient sulfate in the soil will enable plants to utilize
available nitrogen better, since N is a component of all amino acids and S
of some. Thus, when both nutrients are at optimum concentrations, "you get
better protein content" in crops grown for animals. "To improve the sulfur
concentration in the soil, get the organic matter up," said Brunetti. "When
the N:S ratio is 10:1 or less, you're probably getting pretty good forage
quality, good quality protein," he added. The sulfur issue is one that may
be overlooked in Maine, since less S may be coming into our soils as
pollution and S is not reported on the standard soil test here. However,
many growers add the element as sulpomag.

One source of organic matter can be red clover planted as a cover crop. In
animal/cropping systems such as those Brunetti works with, soil microbes
need a lush cover crop like this to help them digest the large amounts of
straw that are being put back into the soil.

Brunetti illustrated the importance of the proper concentration of magnesium
in the soil by explaining that excessive Mg will tighten up soils, since the
element has cohesive properties. This cohesiveness can be "good for sandy
soils" but if too much Mg is present in a soil, you may have to add some
calcium. On the other hand, magnesium deficiency in cattle leads to a
disease called tetany. This can occur in the spring, when magnesium is not
becoming available in the soil as quickly as nitrogen and potassium are.

Regarding pH, Brunetti said, "If I see a low pH soil, I first look at the
base saturation. If it's 28% hydrogen, that tells me there's a soil
fertility problem, because the hydrogen ion is the easiest to knock off of
the soil colloid if calcium and magnesium are present." In a pH 5.2 soil,
for example, he'll "try to get the base saturation of calcium up to 65 to
75%. If I can get that and 12 to 15% magnesium and 3 to 5% potassium, the pH
will take care of itself."

He added that liming provides not just calcium to the soil and the plant,
but produces a variety of other responses as well. For example, when calcium
carbonate (lime) is added to the soil, some of the Ca taken up by the plant
roots. In response (to maintain a balance of ions within plant cells), some
hydrogen is released by root cells into the rhizosphere. Some of this H
combines with some of the carbonate from the calcium carbonate to form
H2CO3, which maintains an equilibrium with H20 and CO2. This CO2 (carbon
dioxide) enriches the atmosphere of the plant canopy, enabling the plant to
make more sugars (CH2O).

Brunetti talked about hardpan as a yield-limiting factor on some farms. "If
you have hardpan, you need to subsoil so that roots can get down deep and
bring nutrients up (and down). If you're subsoiling, do it when the ground
is not too wet and not too dry."

The importance of the 4 tons of microorganisms per acre of soil was
described by Thompson and Troeh in Soils and Soil Fertility (1978), said
Brunetti, when they said, "As below, so above." He said that fresh manure
provides much greater biological activity to the soil than composted manure.
A greenhouse study was mentioned in while composted dairy manure did almost
nothing for soil aggregation compared with fresh manure.

A Proactive Look at Soils

Soil scientist Fred Magdoff pointed out that there can be problems with
using ratios of base saturation as a guide to soil fertility. You can have a
great ratio on a soil with a cation exchange capacity of 4, he pointed out,
and have very little potassium or other elements available for plants.
However, 90 to 95% of the soil samples he sees in Vermont are within the
ranges of Albrecht's formula, Magdoff added.

Fred Magdoff continued speaking about the importance of soils at the Farmer
to Farmer Conference. Magdoff is a professor of soil science at the
University of Vermont and is chair of USDA's regional Sustainable
Agriculture Research and Education program (SARE). He has been working on
ways for farmers to build and maintain soil quality through wise use of
nutrients, cover cropping and manures, and much of this information is in
his and Harold van En's book, Building Soils for Better Crops ($19.95 &
$3.95 shipping & handling from Sustainable Agriculture Publications, Box 90,
Hills Bldg., Univ. of Vt., Burlington VT 05405-0082; Tel. 802-656-0484;
[email-masked].

Magdoff said that the concepts of "proactive" versus "reactive" are germane
to how you organize a farm. The common way of dealing with pests and soil
management to date has been reactive: You see a problem and react; you don't
have enough potassium, so you add potassium. The proactive approach, he
continued, is preventive. Like preventive medicine, you want to avoid
getting sick--and you want to avoid problems on the farm. "How can we design
systems so that we avoid problems?" he asked. "It's an ecological design
issue."

Knowing the difference between symptoms and problems is another issue. You
may have a low fertility soil or a soil with poor structure, Magdoff
explained, but these are symptoms of larger problems. "When we look at the
huge quantities of nutrients that accumulate on farms, people say that is a
problem. I say it is a symptom of an agriculture that's out of whack. It's
an irrational, anti-ecological arrangement in agriculture." He suggests
asking whether any given problem is really a symptom of a deeper, underlying
problem.

Nature Versus Nurture

"We may not be able to have a good soil everywhere," said Magdoff. "Some
soils are naturally less fertile than others." He talked about the nature of
soils versus the nurture of soils. "Almost all soils can be improved,
nurtured. Like our kids, we want them to live up to their potential."

Magdoff listed seven properties of well-nurtured soils. (The first three are
commonly discussed traits of soils; however, they are not enough, Magdoff
said.):

They should hold sufficient nutrients for plants--without excess nutrients,
so that runoff and erosion are not problems.
Their physical properties can be nurtured so that root penetration, water
percolation, aeration and other processes are optimized.
They should be well drained.
Soils should have low populations of disease organisms, nematodes, pest
insects and low weed pressure.
Large numbers of beneficial organisms should be present.
Naturally occurring, non-nutritional components of the soil, such as high
concentrations of aluminum or manganese, should be minimized.
You want a soil that resists problems. "You really see the difference
between a well managed soil and a conventional during problem times, like
drought," he explained. The well-managed soil "does suffer some degradation,
but it can bounce back."

The key issue in managing soils well, in his opinion, said Magdoff, is the
management of soil organic matter. Good organic matter management leads to
healthy soils, which lead to healthy plants, which lead to sustainable
agriculture, he said.

Organic Matter--Living, Dead and Very Dead

Magdoff described three types of organic matter, using terminology developed
in 1908 by Vermont soil scientists J.H. Hills, C.H. Jones and C. Cutler.
Organic matter can be living, dead and very dead. The percent organic matter
in a soil measured by a soil test lab "is not the only issue, and maybe not
even the major issue," he continued. "The type of organic matter is
important."

The living portion includes bacteria, insects, nematodes, fungi, earthworms
and plant roots. "Roots have a profound effect on the soil, and vice-versa,"
he said.

The dead portion is the active organic matter or particulate organic
matter--"the organic matter that decomposes fairly easily." It consists of
sand-sized particles of fresh residues extracted from the soil. You can
still make out what material this organic matter was made from, whether
fungi, leaves, and so on.

The very dead is the well decomposed organic matter, or humus. It is
"passive in the sense that it will not readily decompose because it's
already well decomposed. It's fairly resistant to decay." Typically, organic
matter comprises from 1 to 8% of agricultural soils, and 60 to 80% of that
is humus; 10 to 20% is active; and 10 to 20% is living biomass.

Soil organic matter has profound effects on many soil properties, Magdoff
continued. It is a source of plant nutrients, for example. The very dead
portion has a high cation exchange capacity--greater by weight than
clay--and has naturally occurring chelates that also hold nutrients.

Organic matter improves soil tilth by providing some of the structural
material that cements soil aggregates. The hyphae of mycorrhizae apparently
are especially important in exuding a sticky substance that stabilizes
aggregates. These aggregates promote water infiltration as opposed to the
erosion and runoff that occur when soils crust. "Crusting is a common
phenomenon," said Magdoff. Some crusting can be harmful, by impeding
germination, for example. As an example of the importance of the living
portion of organic matter, Magdoff said that in one experiment of a
10-inch-diameter soil core, one worm hole conducted 10% of the water that
infiltrated that soil.

Organic matter buffers against pH changes, Magdoff continued. "The more
organic matter you have, the more difficult it is to decrease the pH of your
soil."

It also protects against harmful chemicals. "Some soil tests are saying that
if you have a high organic matter content, you don't have to have a high pH.
You can grow barley at a pH of 4.5 if you have high organic matter, because
the organic matter ties up aluminum, which barley is very sensitive to."

Organic matter darkens the soil, which helps it warm in the spring, possibly
giving you a day or two head start on the planting season.

Soil organic matter is a carbon sink. "There's as much carbon in your soil
if you have 1% organic matter in the top 6 inches of your soil as in all of
the atmosphere above," said Magdoff. "Farmers may get paid in the future for
building up organic matter and storing carbon."

Humic materials in soils stimulate roots to divide and grow longer, Magdoff
continued. Even when plants are grown in nutrient solutions
(hydroponically), if humic acids are added to the solution, more root growth
occurs.

Organic matter helps maintain biological diversity in the soil, and
"diversity is your protection" as natural, beneficial organisms keep
potentially harmful organisms under control. Nematodes that are parasitic on
plants are a very small percentage of nematodes in the soil, said Magdoff.
Many of the others are beneficial, feeding on harmful nematodes, on fungal
hyphae and so on. The soil is "almost like a war zone in which diversity is
working for you. All of the organisms keep each other in check--the way our
government is supposed to work."

You have to add organic matter to soils continuously, said Magdoff. "You can
't slack off. You may miss one year, but not two." He cited a study in which
growing continuous corn silage for five years reduced the organic matter
from 5 to 4% of the soil--a 20% loss, which also added carbon dioxide to the
atmosphere.

Losses and Additions

Organic matter decomposition is increased by intense tillage, warm
temperatures, moist soil, light soil texture, and low lignin residues.
Erosion is enhanced by low infiltration rates, which are caused by surface
crusting, compaction and/or a lack of surface residues, by plowing up and
down slopes, and so on. "What's actually going up and down is the active
organic matter," said Magdoff. "The passive is not lost easily because it's
not easily decomposed." Goals for managing soil organic matter should
include, therefore, adding large quantities of organic matter; using
different types of residues (from different species and/or sources); and
reducing losses of organic matter.

Additions can be increased by using existing residues more effectively (don'
t spread manure in the winter, for example); by finding appropriate off-farm
sources of organic matter, such as shredded leaves from towns; by changing
rotations to include high residue and sod-type crops; and by using cover
crops when possible. "Follow any crop by itself and you get a 10% yield cut
just from the lack of rotation," said Magdoff. "No one knows the exact
cause, but the rotation effect can increase yield by 10 percent."

Magdoff reiterated Brunetti's comment about the value of uncomposted manure:
In one experiment that Magdoff did, compost did not help with soil
aggregation as much as manure did, because the compost was already
decomposed and therefore added no sticky substances to the soil.

Reducing tillage helps conserve organic matter on many soils. The real
purpose of tillage, Magdoff explained, is to destroy aggregation in order to
make a good seed bed. "Maybe zone tillage is one answer" to the question of
how to maintain organic matter but have a good seed bed. "Maybe no-till
systems will be developed for organic culture."

Evaluating Your Soil

One way to evaluate your soil is to evaluate your pest problems. Magdoff
said, "It's amazing what nature has done," as he told how many plants, when
attacked by insects, secrete volatile compounds that attract the specific
predator that attacks that pest. "These signals are enhanced in better
quality soils," he said. One grower told him, for instance, that he had no
insect problems on his organic fields, but many on his conventional.
Likewise, when corn borer moths were released in a greenhouse in which corn
was grown in conventional versus organic soil, "time after time, the moth
wanted to lay eggs in the conventional corn. This is one of the exciting
developments in the whole story of soil organic matter management."

One way to judge your soil is to look at it, smell it, feel it. Magdoff said
that when farmers brought their best and worst soils to a workshop at the
Rodale Institute, you could tell them apart by their odor (good ones have a
nice, earthy smell), structure and color (darker being better). You can also
use a penetrometer, which measures the force in pounds per square inch (psi)
required to penetrate the soil. At more than 300 psi, roots can't penetrate.

Root development is a clue to soil conditions. Are roots well branched? Do
they have good color? Are they growing laterally to avoid a compaction
layer?

You can measure water percolation by cutting the top and bottom off of a
coffee can, pushing the can into the soil, placing Saran Wrap over the top,
carefully pouring about a cup to a cup and a half of water into the Saran
Wrap, then removing the Saran Wrap carefully and seeing how long the water
takes to soak in. "Taking measurements in different places will give
different results," said Magdoff. "You need to reproduce measurements in
several parts of the field to get an accurate picture."

You can also look for crusting after rains, and/or "go out in the middle of
a rainstorm and see where runoff occurs." Magdoff talked about Steve Groff,
a Pennsylvania grower noted for his use of no-till, cover crops and good
rotations, who went out with a video camera during a rainstorm and taped
runoff from his farm and from his neighbor's. His farm produced much less
runoff, and what it did produce was clean; the neighbor's was abundant and
turbid. (For more information, see Groff's website:
www.cedarmeadowfarm.com.)

At the other extreme, during a drought you may see parts of your farm that
do better than others, Magdoff added. This can tell you where to put
additional compost. All observations and measurements should be carefully
recorded and organized from year to year, Magdoff recommended. Some states
are developing a soil card to help with these evaluations. It includes such
items as soil color, number of earthworms, condition of roots, amount of
organic matter, subsurface compaction, tilth, erosion, water holding
capacity, infiltration rate and drainage. (Eric Sideman is interested in
developing such a card for Maine soils.) Magdoff noted, as did Brunetti,
that you have to make observations under similar conditions (of soil
moisture and temperature, for instance) in order to be able to compare them
from year to year.

Tillage Tangent

In a brief discussion about reduced tillage, Magdoff said that you have to
be careful with the practice because it eliminates the option of plowing to
reduce compaction. One way to reduce compaction on no-till farms is to
control traffic to certain areas of the field. "It's better to pack the hell
out of a small area of the field than to have less compaction in a larger
area," he said. "Permanent raised beds are the ultimate in controlled
traffic."

Responding to a question about what type of cation exchange test to ask for
on a soil test, current or altered, Magdoff suggested always getting the
current, and keeping track of it each year or two. (The altered test tells
what the cation exchange capacity would be at a particular, altered pH; the
current tells the CEC at the unaltered pH.) He added that testing the soil
every two years is good enough, and Waldo County Extension Educator Rick
Kersbergen added that soil test cost less if they're sent to U. of Maine
between Jan. 1 and April 15; he also said that the soil should be held at
room temperature.

Cover Crops and Soil Fertility

Marianne Sarrantonio is the author of The Northeast Cover Crops Handbook,
was a researcher at the Rodale Institute, and joined the faculty of the
Sustainable Agriculture program at the University of Maine this winter. At
MOFGA's Spring Growth Conference in Unity in March, she talked about using
cover crops to build soil fertility.

Sarrantonio outlined four basic ways to do this:

Providing nitrogen through cover crops;
Increasing organic matter;
Protecting against erosion; and
Recycling nutrients from deep in the soil profile.

As an N source, legumes can make available or contain as much as 300 pounds
of N per acre, although 100 to 150 pounds is more common. Approximately
two-thirds of this N is "fixed" from atmospheric N when rhizobia bacteria
living symbiotically with legume roots take N out of the atmosphere and
convert it to a form that plants can use. Plants in return supply the
rhizobia with carbohydrates. Some 20 to 60% of the N in legumes generally is
available to the next crop. The variation occurs because this N is released
by decomposition, and environmental conditions impact decomposition. Very
dry, wet, acidic or mineral deficient soils limit microbial activity. The N
that isn't released may be retained in residues in the soil or in
microorganisms; this, said Sarrantonio, "is a key difference between
providing N as a legume versus as a bagged fertilizer."

To tell if the rhizobial relationship is working, Sarrantonio said to
carefully dig up the plant, wash its roots, and look for large nodules that
are clustered around the main part of the root. Break a few off, break them
in half and look for a pink color inside. If they're green, white or black,
N fixation is not occurring. You are looking for a lot of nodules, large
nodules (if that particular plant has large nodules; hairy vetch does not),
and active nodules.

"Just because you plant a legume doesn't mean you're getting N fixation,"
said Sarrantonio. "You need the right rhizobia in the soil. There's a close
match between the type of legume and the rhizobia. Vetch [rhizobia] is
different from clover, which is different from soy... It's important to
spend $2 and inoculate the legumes you're planting. The rhizobia may
[already] be in the soil, but there may not be enough of them," and they are
competing with other soil microorganisms.

The rhizobia that you buy is packaged in a peat substrate. It needs to stay
moist and relatively cool, and even under these conditions is good only for
about six months, so check the date on the package, Sarrantonio advised.
"The number of live cells plummets precipitously after the expiration date."
She encouraged conference participants to tell their farm stores to
refrigerate inoculum, and she advised against using 'multipurpose' inoculum,
since you are putting competing rhizobia right on the seed with the
desirable rhizobia.

To use the inoculum, moisten the seeds slightly, mix them with the inoculum,
then plant them as soon as possible. Some people recommend adding a sticking
agent (Kool-Aid is sometimes recommended) to help the bacteria adhere to the
seed, but Sarrantonio believes that that may promote fungal growth. Milk
does seem to work, she said, but she prefers to use water.

"If you're going to grow the same legume two years in a row, you probably
don't need to inoculate," Sarrantonio continued. "Past that, it's worth
inoculating."

Conference participant Dave Colson noted that he uses a spinner to sow his
seed, and if the seed is too wet, the spinner doesn't distribute it well.
"If the seed is that wet," Sarrantonio responded, "it's too wet. Let it dry
for half an hour or so before seeding. A pound of seed needs maybe 1/2
teaspoon of water to get the inoculum on."

The amount of N fixed varies from 20 to 300 pounds per acre. "Some legumes
are inherently poor fixers," said Sarrantonio. The common garden bean
 Phaseolus ), for example, "never pulls its own weight. You need to add N."
Hairy vetch and alfalfa, however, are excellent and "may provide 85 to 90%
of their own needs by fixation." The length and temperature of the growing
season impacts fixation; temperatures between 70 and 90 degrees F are
optimum for the process. The health of the crop is important. "The legume is
feeding the rhizobia. If [the legume crop] is not in good shape, it's not
providing enough carbohydrates." As mentioned, the proper strain of rhizobia
is critical; and environmental conditions, such as soil moisture, can
influence fixation.

Sarrantonio presented the following data to show that fixation varies with
cover crop species. The legume was overseeded into spring broccoli in
Pennsylvania to fix N during the month between summer and fall broccoli
crops there. Yield data were from Aug. 20 harvests.

Species, kg/ha, N kg/ha

Siratro, 978, 34.2
Berseem clover, 1008, 38.3
Dalichos biflorus, 1127, 33.8
'Huban' sweetclover, 1780, 67.6
Crotolaria juncea, 1394, 44.6
'Red Ripper' cowpeas, 2105, 79.9
New Zealand white clover, 1067, 40.5

Cowpeas produced the most nitrogen--79.9 kg/ha (roughly equivalent to
pounds/A) in five weeks. Although the data would be different in Maine,
Sarrantonio thinks that cowpeas are "worth looking at."

The Fate of N

What happens to the nitrogen that's fixed? A small amount may leak during
growth, but most of it is going into the legume, Sarrantonio said. The main
benefit to the crop comes after the legume dies and begins to decompose,
however. Since most of the N is in the tops of plants, if you remove the top
growth from a crop such as alfalfa or clover, only a little N remains in the
roots. You need to get into a system of using cover crops to get the
accumulated benefits of these plants, said Sarrantonio.

"Tillage has a tremendous effect on how much N is available" to a crop,
Sarrantonio continued. In conventional tillage, N can be placed as deep as 8
to 10 inches down in the soil by plowing, but no roots grow at that depth
early in the season, so N is vulnerable to leaching. In a no-till system, on
the other hand, N is concentrated in the top few inches of soil, so there is
less chance of leaching. When organic residues are left on the surface of
the soil, there is a greater chance of nitrogen going off into the
atmosphere, however. "You often see a reduced benefit of a legume when it is
left on the surface." The solution may be shallow tillage, Sarrantonio
speculated.

Organic Matters

Organic matter is important because it improves soil aggregation and tilth,
said Sarrantonio; it increases the cation exchange capacity of the soil (the
net sum of negative charges in the soil), thus is the key to keeping
nutrients in the soil when plants aren't using them; recycles nutrients;
provides habitat for microorganisms; and increases the water holding
capacity of the soil. "Some organic matter can hold up to 20 times its own
weight in water," said Sarrantonio.

Typically, non-legumes increase the organic matter content of the soil more
quickly than legumes, because the succulent, nitrogenous legumes are
decomposed quickly by microorganisms. Non-legumes have more carbon relative
to nitrogen, and high-carbon material usually doesn't break down so quickly,
Sarrantonio explained. Thus, grasses break down more slowly than legumes and
may even tie up N as they are breaking down. One solution may be to grow
grass-legume mixtures. Sarrantonio related another that she saw in
California: Crop of fava beans (high N) was grown, cut, and laid on the
ground, then was covered with straw (high C) in a sort of sheet composting
process.

In addition to providing nitrogen and holding nutrients, cover crops can
protect against erosion. They can increase water infiltration rates; their
roots can stabilize slopes; they can decrease the physical impact of
raindrops on soil structure; and they can slow the velocity of runoff.

One example of a cover cropping system, said Sarrantonio, is overseeding
peppers with white clover and ryegrass in the summer to protect the soil in
the fall. To protect soil in the spring, winter annuals such as hairy vetch
can be sown and then mow-killed in the spring. All winter annuals can be mow
killed, she noted. The soil may stay a bit cooler in the spring using this
method, and fungal diseases and slugs can build up as well. As an example of
a mow-kill, no-till system, she said that corn can be drilled into live
vetch, then the vetch can be mowed after a few weeks. In field trials (not
in Maine), this system added 10 days of growth to the vetch. In another
example, tomatoes were planted into hairy vetch and rye. The cover crops
kept the weeds down and the vetch added enough N for the tomatoes. MOFGA's
technical director, Eric Sideman, noted that this system works better in the
south than here because of climate differences.

Sarrantonio showed a graph comparing the amount of N taken up by
September-seeded cover crops (again, not in Maine) to make the point that
significant amounts of N can be conserved by using cover crops. She said
that among the crops used, cereal rye (the same as winter rye) is best for
Maine:

Cover kg N/ha
Cereal rye 71
Wheat 40
Ryegrass 38
Brassicas 35
Oats 28
Barley 32
Legumes 10

The key, said Sarrantonio, is getting the cover crop planted early enough
"to do the job."

A possible added benefit of cover crops, Sarrantonio continued, is that
mycorrhizae may enable these plants to take up nutrients--especially
phosphorus--that are outside of the normal rooting patter. "Legumes tend to
have good mycorrhizal relationships," she said, "probably because of the
nitrogen. You may not notice the benefit [immediately], but once P is in the
legume and the legume is plowed down, P is now in a more available organic
form."

Dave Colson asked Sarrantonio about managing yellow sweet clover, a biennial
that grows quite large. "How would cutting it during the second season
affect N fixation?" he asked. "Typically," Sarrantonio answered, "when you
cut any legume that will regrow, you get a temporary cessation of N fixation
while [the legume] reestablishes its growth. Also, the clippings add N to
the field and can shut down N fixation. You might cut it and remove it to
keep the soil 'starved' for nitrogen."

Eliot Coleman asked whether, over a 13-month, June-through-July period, it
would be better to grow sweet clover as a cover crop for the entire period,
or grow cow peas followed by rye and vetch. "From a soils point of view,"
said Sarrantonio, "sweet clover would probably be better because you don't
have the added tillage. From the point of view of mixed residues and being
easier to work with in the spring," the second option may be better. "But
not too much is better than sweet clover," she concluded.

Kersbergen on Assessing Soils

Rick Kersbergen of U. of Maine Cooperative Extension told how to assess soil
quality using simple tools and how to manage soil organic matter at the
Spring Growth Conference. "What changes are occurring on your farm? Are you
improving your soil health?" he asked.

To illustrate one simple way to assess soils, he showed two soils that he
keeps in his office--one with peat moss and manure additions, one without;
both are kept moist. The vast difference in color of the two can give you an
idea of how different management systems affect soils, he said.

"We destroy soil health every time we plow, till or cultivate," he said. "We
improve it when we add organic matter." Adding organic matter also helps the
soil respond to the negative impacts of whatever tillage is necessary.
Kersbergen reiterated Magdoff's assertion that raw manure "is much better
than compost or cover crops in producing soil with good aggregation."

To judge the stability of soil aggregates--which determines the ability of
the soil to resist breaking down--Kersbergen demonstrated how growers could
put soil in a 1.18 mm screen, put the screen in a tray of water, and shake
it gently. "What's left on the screen in terms of aggregates?" he asked, as
he pulled it out of the water, showing the number of clumps remaining. He
suggested screening rocks out of the soil first; and to get a better look at
the size and number of aggregates, the soil could be sieved through screens
of different finenesses.

Crusting indicates poor soil health, Kersbergen continued, and a single
green manure crop is not going to reverse that illness. He echoed
Sarrantonio's advice that growers need to develop long-term systems to keep
soils healthy. "Eighty percent of a green manure crop can decompose in a
single season," he said. "You need a continuum of green manure and fresh
manure additions."

To measure compaction, Kersbergen showed a penetrometer, which measures
resistance as it moves through the soil profile. "Rocks can be a problem,"
he noted, "so take multiple measurements." As an alternative, "you can just
use a wire [or fiberglass rod--especially if you're testing a hayfield or
forage crop and don't want to risk having a cow ingest a lost wire]" as
found on flags used to mark fields. Try pushing the wire into the soil
between crop rows, within rows, at tire tracks... "It shows how roots would
do going through the soil."

Kersbergen demonstrated the coffee can method of measuring water
infiltration into soil, mentioned above by Magdoff, but used a 6-inch piece
of stove pipe instead. Place a board on top of the stove pipe to drive it
into the ground, said Kersbergen. When he has used this technique to compare
how fast equal volumes of water penetrated soils that held sod or cover
crops, the sod had the highest rate of infiltration. Kersbergen said that he
's a big proponent of increasing sod in cover crop rotation systems. If sod
is in place for two years with no tillage, "there's great potential to
increase soil health." However, there are tradeoffs regarding nitrogen
additions and other inputs, he noted.

A pH meter, said Kersbergen, costs only $40 to $50 and is a good investment
for growers. To use it, mix equal volumes of distilled water and soil, let
the mixture sit for half an hour, then measure the pH in the soil slurry.

A Soil Health Test Kit, available from Gemplers and from Woods End Lab,
costs $200 to $1000 and measures respiration and other parameters of soil
health. And, of course, soil tests for chemical properties and organic
matter content are widely available and use accepted, well established
procedures to measure the nutrient status of soils.

When trying to maintain organic matter in the soil, Kersbergen reminded
growers that "there is a big difference between manures. Poultry manure
alone is not a good amendment. Chickens eat grains" and their manure does
not contain much fiber. "Cows eat grass," so theirs is more fibrous.
"Chicken manure is simply a fertilizer source; others are more fibrous and
better food sources for microorganisms."

He noted that weed seeds in liquid cow manure that had been stored for three
months were very low in viability, while viability of seeds in manure that
had been stored in stacks did not decrease much.

Ingham on the Soil Foodweb

Dr. Elaine Ingham, another speaker at MOFGA's Spring Growth Conference, is a
professor at Oregon State University and founder of the organization The
Soil Foodweb, Inc., which provides growers with information on the health of
their soil. After doing a double major in biology and chemistry at St. Olaf
College in Minnesota and receiving her M.S. in marine microbiology from
Texas A&M, Ingham went to Colorado State for her Ph.D. and Post-Doctoral
degrees in soil microbiology. At Colorado, she developed a database of
microbes in different soil types and found significant differences in
foodweb structures in irrigated versus dryland wheat soils. Ingham continued
her study of different soil foodwebs at the University of Georgia, where she
looked at soils from agronomic crop fields, from different rotations, from
forests and from the everglades. When she moved to Oregon State in 1986, she
had the chance to study the soil foodwebs of environments ranging from
rainforests to high cold desert. She now has a database on more than 80,000
soils from all over the world.

Ingham learned that the make-up of the soil foodweb depends on the plants
growing in that soil, and that the plants growing in a particular soil
depend on the nature of the soil foodweb. "It's not a chicken and egg
situation," she explained, but more of a feedback system in which plants do
influence what lives in the soil, but a point is reached at which the web
organisms have to be changed in order for new types of plants to grow.

Early succession tree species, for instance, such as poplar, birch and
alder, start in soil that is dominated by bacteria but move the soil life to
a fungal population. "Really productive forests" have 100 times more fungal
than bacterial biomass, while the most productive forests have 1000 times
more fungal than bacterial biomass.

Ingham's goal in studying soil foodwebs in different situations is to
determine what foodweb system will enable growers to raise crops without
depending on fertilizers and pesticides. She talked about the
strawberry-growing region of California, where the early settlers were able
to do just that for several years. After years of monoculture, however,
productivity began to decline. After World War II, pesticides and synthetic
chemical fertilizers became popular among growers--and pest populations
increased. More fungicides were needed to fight the Verticillium fungus.
Then the soil fumigant methyl bromide was employed to sterilize the soil so
that root-feeding nematodes were also kept at bay long enough for a crop of
strawberries to be grown. Starting in 1955, methyl bromide was used once
very three years. By 1965, it was used every year, and by 1970, it was used
on every crop rotation. For the last 14 years, methyl bromide has been
applied two or three times a year in some areas. This option will soon be
phased out, however, since methyl bromide depletes the ozone layer.

Ingham was called in to help find an alternative to methyl bromide. She
studied soils in the nearby chaparral and found the original soil foodweb
complex that had been destroyed by years of chemical applications in the
strawberry fields. In the chaparral, sheep and cows grazed and plants grew
with no inputs, and no harmful root-feeding nematodes were present in the
soil. The valley soil where strawberries grew, however, contained harmful,
root-feeding nematodes, spores of harmful fungi and other disease organisms,
and was very low in bacteria. Ingham found that by replacing half of the
volume of the soil in a strawberry bed with compost, she could get the soil
back to a productive stage, with yields greater than those from the methyl
bromide system. However, California does not have enough compost to amend
that much soil, so Ingham came up with an alternative method of introducing
beneficial soil organisms: She grew strawberry plants in plugs of compost
for three weeks, then transplanted the plugs to the soil beds. The system
worked: The first crop yielded 600 pounds per acre more than that using the
methyl bromide system; and by the fourth time compost-plug plants were used,
yields were double those of the methyl bromide system. "California is
finding that it costs less to do sustainable strawberries than methyl
bromide--but they have to know how to make good compost," she said.

She believes that adding organic amendments to the soil--humic acids,
compost, compost tea, etc.--is necessary to keep soil life alive. If you add
100 pounds per acre of an inorganic fertilizer to a soil at one time, "you'
re killing [soil organisms] basically through a salt effect," she explained,
adding that those who use synthetic fertilizers would do better to use split
applications--or to switch to organic amendments. Likewise, "Every pesticide
has an effect on a soil organism," she said. "Every one is killing a
beneficial organism." High concentrations of nitrate-nitrogen in the soil,
as well as soil compaction, also kill beneficial organisms and select for
disease-promoting bacteria.

Disease Suppression

"How do you get rid of plant feeding nematodes?" asked Ingham. "Get the
competition in," including fungal feeding nematodes, bacterial feeding
nematodes, and predatory nematodes. Also, mycorrhizal fungi help as their
hyphae "make it difficult for root feeding nematodes to get through the soil
to your root." The easiest way to get the competing nematodes in is to add
compost. "You cannot buy them," she said. Mycorrhizal fungi, however, can be
purchased and added to the soil. These fungi, she noted, do not survive
composting.

The members of the soil foodweb, from the protozoa, bacterial, fungi and
nematodes to the earthworms, centipedes, spiders, beetles and insect larvae,
create a system in which diseases are suppressed, nutrients are retained and
made available, toxic materials can be decomposed, and soil structure is
built. The plant that you grow is part of that foodweb, too. Ingham told
conference attendees to picture a plant growing in their field. "How many of
you put the root system into it?" she asked. "How much of the energy from
the top of the plant goes down to the roots? Sixty percent on row crops and
vegetable crops," she said, and 80% in trees. "More than half of the plant's
energy is below ground. That energy is used to grow structural roots to
support plants...and lateral roots to take up nutrients." About 50% of the
energy that goes into the root system is exuded into the soil as simple
sugars, proteins and carbohydrates--"cake and cookies" for microorganisms,
Ingham said. "Every plant has a different mixture of sugars, proteins and
carbohydrates that it makes," she continued, and you can tell what plant,
time of year and soil type is present by that mixture. The mixture is needed
"to wake up critters needed to protect against disease." For example, a
bacterial wall can form around a root system that will protect the root from
disease: A white rot fungus just 1 mm away from the biofilm will not
germinate.

The foodweb needed to fight diseases is complex. Ingham said that one
cucumber cultivar growing in the presence of one type of fungal rot can
require a succession of 12 species of bacteria to counter the disease. A
different mixture of bacteria will be required at a different temperature,
under different humidity conditions, and so on. Rarely is one disease
organism present. "Your plants are challenged by about 1000 things that are
trying to attack the root system. You need a lot of species to counter them.
'Bugs in a Jug' [commercial preparations of soil microorganisms] may only
have five or six; one brand has eighty. That's not enough. You need to
maintain as high a diversity as possible."

Nutrient Uptake

Not only can the proper soil foodweb help fight disease, but it may increase
the nutrient content of plants as well. "You may not necessarily see bigger
plants, but you will see plants with higher nutrient levels in them" when
the proper fungal and bacterial populations are present in the soil. Grapes
growing in a healthy food web, for example, had three times more protein
than those growing in a depleted system. Wheat had 10 times more protein;
organic produce had higher protein levels; concentrations of organic
nitrogen can be increased, adding flavor to crops. "We taste proteins as
being sweet," Ingham explained, and nitrogen is a component of proteins.
Concentrations of every micronutrient are increased when plants are growing
with mycorrhizal relationships, she added.

Nutrient Retention in Soils

Nitrate (NO3-) is the most leachable form of N in the soil, Ingham
continued. The ammonium ion (NH4+) is the second most leachable form. Thus,
she said, in agricultural soils, 80% of the fertilizer added ends up in the
groundwater. On the other hand, bacteria and fungi are the least mobile
forms of N in the soil. Bacteria make a "glue layer" that glues clay, sand,
organic matter and other particles together and improves the structure and
the filtration capacity of the soil. Fungi grow as long strands and bind
soil particles together, and they make enzymes that enable them to "pull
nutrients out of the soil.

"There is not a more concentrated form of N than bacteria on earth," Ingham
said. "Bacteria are sinks of nitrogen. They make enzymes to pull in
nitrogen." Plant roots do not make these enzymes, as plants evolved after
the system of bacteria and fungi existed in the soil. Bacteria, she
continued, maintain N as nitrate--the most efficient form of N for row crops
to take up--by maintaining the pH of the slime layer between 5.5 and seven.
Thus, the best soils for row crops are dominated by bacteria. For trees,
perennial herbs and shrubs, ammonium is the preferred form for uptake, and
fungi maintain that form.

Soil Structure
Bacteria "build the bricks" of soil structure with their slime layers, while
fungi bind soil particles together with their hyphae. Then microarthropods
and bacterial feeding nematodes create the spaces in those aggregates in
which they feed on fungi and bacteria. This produces good soil
structure--aggregates with air spaces.

When a soil is compacted, if a healthy foodweb exists, it will spring right
back, Ingham said. Otherwise, root feeding bacteria and protozoa are left,
the oxygen concentration drops, the aerobic organisms "go to sleep," and
facultative anaerobes "turn on anaerobic enzymes" that produce alcohol,
which kills roots; acetic acid, giving a smell of vinegar to the soil;
butyric acid, which gives a sour milk smell; valeric acid, which gives the
smell of vomit; and hydrogen sulfide, which has a urine smell. These
anaerobic decomposition products turn the soil into hardpan.

Above Ground Foodwebs

Not only has Ingham studied the soil foodweb, but she's looked at foodwebs
on leaf surfaces and found that the right community of organisms there can
fight diseases. Leaf surfaces produce exudates that can feed pathogens, she
explained, so "you want to use those exudates for beneficial organisms so
that infection sites are occupied" and pathogens can't become established.
In one experiment, she sprayed 70% of a leaf surface with Botrytis cinerea,
then applied Foliacin bacteria over 100% of the leaf surface. No disease
occurred. She has done this with other pathogens and found similar results.
"You don't need 100% coverage," she said. On grapes, 70% worked, but 50%
didn't. She added that you need to apply beneficial sprays early to avoid
foliar diseases, because pollutants, fungicides, dust, and other airborne
particles can increasingly interfere with the process over time.

Making Good Compost

To make good compost, Ingham gave two recipes: one for bacterial dominated
composts, which are used for annual row crops; and one for fungal dominated
composts, which support growth of perennial plants (including strawberries).
The recipes are:

Bacterial Dominated Compost
***25% (by weight or volume) high nitrogen material, such as legumes or
fresh manures. If poultry manure is used, drop this to 15%; if pig manure is
used, drop it to 5 percent
***45% "green stuff" to feed bacteria--grass clippings, coffee grounds (the
beans are green when harvested). If you used pig or poultry manure above,
increase the percentage of green material.
***30% woody material, such as hay, straw, wood chips (after the scent of
volatile compounds has disappeared), dry brown leaves but not solely oak
leaves)
Fungal Dominated Compost
***25% high nitrogen material
***30% green material
***45% woody material

After making the pile, it should heat to 135 degrees within 24 to 72 hours;
if not, it doesn't have enough nitrogen, and/or pesticides in the material
may have killed decomposing organisms. You can add a 1% sugar solution to
the pile to feed the bacteria that can degrade the pesticides, said Ingham.
If those bacteria have already been killed, they can be added back as "Bugs
in a Jug"--i.e., commercial preparations.

The pile should heat to 155 to 160 degrees, when it should be turned so that
beneficial organisms aren't killed. After turning the pile three or four
times, the organisms should have "used up the juicy material" and protozoa
should be proliferating. The temperature will now drop below 135 degrees.
When the temperature is around 115 degrees, nematodes start to proliferate;
this is the material that should be used to make compost tea, if that is
your goal, and this material must be aerobic, said Ingham; if it's
anaerobic, "you're selecting for disease." If compost tea is not your goal,
the pile can sit until it soon reaches the ambient air temperature,
indicating that it is mature. If you turn it at this point and it heats
again, it was not mature. As mature compost ages, the diversity of species
that populates it increases for about six months; then diversity decreases,
and after two years, it is "no different from topsoil" as far as microbial
life.

Mature compost should have a moisture content of 15 to 50 percent, said
Ingham. "Dig into the pile with your hand. Take a handful from the middle.
If you can squeeze moisture out, it's too wet. If you can only squeeze one
drop out, it's good. If you blow on it and can get dust off of it, it's too
dry."

Abundant Resources

For more information, Ingham referred people to her website,
www.soilfoodweb.com. Not only is her site packed with information, but
readers can subscribe to her free e-mail magazine from the site. She can
also be reached at Soil Feedweb Inc., 1128 NE 2nd St., Suite 120, Corvallis
OR 97330; Tel. 541-752-5066; Fax 541-752-5142; or at [email-masked].
Her site links to www.growingsolutions.com, where you can order an excellent
manual on making compost tea. "Some of the most amazing stuff we're working
on now," she said, is controlling "botrytis, mildew, late blight, early
blight, black spot on roses" and other diseases with compost teas.

Ingham was the primary author of Soil Biology Primer, available from
[email-masked] or by calling 1-888-LANDCARE (dialing the last E is not
necessary; it's just there to make the acronym). This 54-page booklet,
produced by the Natural Resources Conservation Service, is a
well-illustrated (with many of Ingham's photos), easy-to-read introduction
to what lives in the soil and why it's important.

Michigan Field Crop Ecology: Managing Biological Processes for Productivity
and Environmental Quality, is available for $12 from Michigan State Univ.,
Bulletin Office, 10-B Ag Hall, East Lansing, MI 48824-1039. The 86-page
booklet was written for Michigan farmers and edited by M.A. Cavigelli, S.R.
Deming, L.K. Probyn and R.R. Harwood. Chapters include Field crop
ecosystems, Soil ecology, Carbon, Nitrogen, Cover Crops, Pest ecology and
management, The insect community, Nematodes, Directions for farm change, and
Bringing it all together.

Better Homes and Gardens Special Interest Publications put out a magazine
called Perennials in the spring of 2000 that had an article called "Soil's
Alive!" by Ann Lovejoy. The article is an excellent introduction to the
field of soil life, with good illustrations and a photo essay that shows how
to make compost tea.

Other resources, including soil microbiology textbooks, are cited on Ingham'
s webstie and in the comprehensive bibliography "Soil Biology Educational
Resources," available from USDA Natural Resources Conservation Service Soil
Quality Institute, 2150 Pammel Dr., Ames IA 50011; Fax 515-294-8125; email
[email-masked] or [email-masked]; website www.statlab.iastate.edu.

Minerals and Rock Powders

Agricultural Alternatives Consultant Mark Fulford, who lives in Monroe and
has been farming for 25 years, spoke about the use of minerals and rock
powders at the Spring Growth Conference. "There are lots of poor, sick,
tired out soils in New England," he said. The combination of geological
processes, weathering, environmental pollution and poor practices has
depleted soils of a lot of their mineral content and biological activity.
"Some soils have all the minerals but not enough life. Others have the
opposite." You must build the soil foodweb and the mineral content of the
soil; "You can't have one without the other," said Mark, explaining that the
microorganisms are the "delivery system" for the minerals.

When Fulford has seen fruit trees growing in younger soils that have more
igneous material than our New England soils, he has observed that the trees
are healthier. He listed many characteristics of crops grown in soils that
are deficient in available minerals, versus those from soils that are rich
in minerals:

Plants and Livestock from Soils Deficient in Available Minerals:

Late to missing maturity
Scant blossoming
Abortive fruit setting
Poor yields, sparse fruit and foliage
Susceptibility to wind damage
Intolerant of drought conditions
Subject to disease and insect attack
Easily decayed, necrotic
Lodging under moderate wind and rain pressure
Discolored foliage
Insipid color and flavor to downright inedible
Crop easily overwhelmed by noxious weeds
Low brix levels (a measure of soluble solids)
Low protein levels
Unpalatable forage; livestock turn up their noses at mediocrity
Excessive need for feed supplements and high vet bills
Unmistakable mediocrity
Plants and Livestock from Soils Rich in Available Minerals
Robust growth
Consistently early maturity and highly productive yields
Resistant to wind, water, cold, heat and prolonged drought
Not attractive to destructive insect attack and displays high tolerance to
infestations without compromising the crop
Resistant to plant pathogens
Less weed competition, which often occurs in imbalanced soils
Good plant color, all season
Easily pollinates and holds blossom and fruit set
High brix readings for soluble solids in both foliage and leaf
Healthy livestock, low vet bills
Exceptional flavor
Long storage with low decay
Highly palatable to livestock who may invite friends and relatives as
unannounced guests from neighboring farms. "You cannot fool a hungry cow."

After observing better plant growth on younger, more mineral-rich soils,
Fulford became interested in paramagnetism--the weak magnetic fields
inherent in these minerals. "There is an electrical and magnetic component
of the soil, and you can use it to cut down on diseases, increase
productivity," and more, he said. When he began using paramagnetic rock
powders and minerals on his farm, he found greater mineralization of the
soil in the living base, less trouble with climate zones (i.e., crops had 2
to 3 degrees more frost resistance and fruits matured earlier), less trouble
with insects and diseases, and more beneficial organisms. His potato bug
problem was gone.

Using a paramagnetic meter to measure a typical garden soil gives a reading
of 8 to 10, said Fulford, while an active, minerally-charged soil will have
a reading of 100 to 200. Adding a compost-rock mineral mix to the soil can
produce a highly charged, productive, disease resistant soil.

Among the minerals Fulford has used are rock phosphate, greensand, granite
meal and Azomite--a finely ground rock dust powder that has a high
paramagnetic charge on it. "I eagerly buy about a pallet load a year and put
it in my compost pile," said Fulford. He adds two or three 50-pound bags of
rock powder per cubic yard of compost when he first builds the pile. Putting
25 to 30 pounds of this composted mineral matter around a mature fruit tree,
at an expense of about $8 to $10 per tree, "is worth it for an heirloom
tree, but not for a Mac or Red Delicious," joked Fulford. Rather than put
the minerals in the compost, they can be scattered around the base of the
tree, then the compost can be spread, then a couple of layers of cardboard
can be applied "to buy time before the quackgrass comes through it." Using
these methods, "you can get a crop three to four years earlier," said
Fulford.

Greensand and rock phosphate can also be added in with the litter in animal
bedding, and the animals will mix the materials together for you. Other ways
to add minerals and rock dusts include:

Field broadcasting dry rock powders
Overcasting in sheet composted cover crops
Foliar feeding through liquid solution or dry dusting. Foliar feeding can be
enhanced by adding spreader stickers, said Fulford, such as hydrogen
peroxide, ascorbic acid, biodynamic potentizing, combining them with liquid
or dry humic and folic acids, or in compost teas.
Fulford's handout concluded with some definitions:
Cation Exchange Capacity--available parking places for nutrients
Humus--stored sunshine
Soil without life--dirt
Field quality testing tool--loose cow
Composting--culinary art of soil enhancement recipes
Farm without a garden--economic establishment with quality of life issues
Paramagnetic rock powders--an agricultural ignition key
Paramagnetism/diamagnetism--soil yin yang\

You can contact Fulford about his consulting services at Box 151, Monroe ME
04951; Tel. 207-525-7761. For more about paramagnetism, see Paramagnetism:
Rediscovering Nature's Secret Force of Growth, by Philip S. Callahan, 1995
and 1998, Acres USA.