The commercial fertilizers that conventional farmers
use to maintain crop yields are prohibited from use under organic certification
standards. The organic growers interviewed maintain soil fertility in
several ways the use of legumes provides nitrogen, the incorporation
of organic matter into their soils makes nutrients available for plant
growth and the use of manures and other approved, off-farm inputs can
provide needed nutrients. The application of lime is a certified practice
that most Ohio farmers undertake to maintain appropriate soil pH levels.
Agronomists and Extension agents urge farmers to make routine soil tests
to determine the extent to which crop production has removed nutrients
from the farm and to form the basis for nutrient supplementation. We
were interested in finding out if the organic growers test their soils
and if they use the soil test to help make production decisions. Here
are their answers. Ron G. said that "Yes, we test about a half to
a third of the fields every year and lime accordingly. Generally, we
put on 4 tons to the acre on one third to one fourth of the acres yearly.
That keeps soil pH right about 6.3 to 6.5."
Dean M. "No, It's time we did soil tests again. We've had some
individual fields done and the levels are all improving. We just haven't
made it a part of our regular program." Nelson and Lynn W. "No,
what's a soil test?" He laughs, then adds:
We used to, but in the last three years we haven't done any. We've been
considering doing some lately because some of our alfalfa stands, some
spots haven't come up the best so we thought of doing some tests to see
what's going on there. We also haven't put lime on for a couple of years
and with using this manure from the diary we thought we might be getting
our soil a little acid and might need some lime to keep our alfalfa stands
Geoff M. "Yes,
I want to do it every year."
Jeff D. "I've
had them tested every three years, most of my ground, by an independent
soil agronomist, a local independent lab."
Byron K. "I've
tested my soil four or five times during the past 12 years."
Steve B. "I'll
pick a couple or three fields with different soil types, maybe my best,
medium and poorest fields and soil test maybe every other year."
If some of our organic farmers appear to be somewhat casual about monitoring
their soil fertility levels, it may well be because they are less concerned
than conventional farmers with the direct relationship between yearly
soil nutrient programs and crop yields, specifically between nitrogen
requirements and corn yields. It's already been noted that some of the
farmers interviewed do not raise corn but rather focus on rotating their
soybeans with small grains, that is, with crops that require less nitrogen
than corn. It could be argued, even for the organic corn growers, that
premium prices give them the luxury of neglecting a nutrient management
strategy designed for the highest yields possible.
Nitrogen (N) management for organic corn and small grains to a lesser
extent because of their lower N requirements involves the use of a green
manure crop, principally red clover, and, in some cases, the use of animal
manures. One of the farmers interviewed uses fish emulsion as a nitrogen
Jeff D. sows red clover in March into his fall-planted spelt or drills
it with spring-planted oats. After the small grain is harvested the clover
"It'll go through the winter with a clover
cover and then the next year I'll let it go and make a first cutting
of hay, or just let it go. ... I'd just as soon let it go and mow it
once during the summer. The roots will regrow better. Then I'll plow
it that late summer or early fall, chisel plow it. The chisel doesn't
really kill it and I'll go in in the spring the next year and work
it twice with the field cultivator. And then plant corn."
"Do you get enough N for the corn from the clover?", he was
asked. "Yes, the yields have been going up every year. Last year,
the best yield was 114 bushels per acre and the worse was 105 bushels." Geoff
M. He also uses a combination of red clover and sweet clover as his only
N source for corn. The clover is frost-seeded by broadcasting into a
standing wheat crop in February or March. After the wheat harvest, he
will mow the clover to keep thistle and other weeds from going to seed.
Then he will let the clover stand over the winter as a cover crop. The
following year he will let the field stand in clover but mow it to keep
the weeds down. (Geoff is considering combining the clover seed "as
Rex Spray does.") In the fall, or the following spring before planting
corn, he will disk-chisel it, perhaps twice.
When asked if he feels that his clover management
program provides sufficient nitrogen Geoff responded: "That's a good question. I think when
you leave it (the clover) for one year like that you're fine." He's
of the opinion that having a four-year rotation with the legume standing
for a year is a better system that shorter rotations. "I don't think
you get enough nitrogen in just a three year rotation."
Nelson and Lynn W. The
Wengers also have a four-year rotation that includes a corn crop. Their
green-manure crop of choice is alfalfa and, in addition, they apply
some dairy-cow manure for nitrogen. They have been averaging 135 bushels
of certified organic corn per acre over the past few years. "A
good crop of alfalfa has enough N for corn, especially if you plow down
some residue and add some manure. There's just no lack (of N). Our corn
is just picture perfect green in the summer." Admittedly, the Wengers
are unaware of the relative N contribution of their alfalfa compared
to that of their manure.
Some organic farmers use hairy vetch as a plow-down nitrogen source,
but for others it seems to be more trouble than it's worth. Geoff
M. thinks it has real potential on his southern Ohio farm and hopes to experiment
with it in the future, but Steve B. has tried it and decided not to use
it any longer.
We tried hairy vetch with rye, but my experience is that it hasn't worked
very well. I didn't think we were getting any nitrogen out of it. Just
seems like when it comes time to plow, there were no nodules on the roots.
And it's been a pain to plow under. The other thing about vetch is that
it says on the bag that 10 percent of the seeds are hard and won't germinate
the first year so I'm seeing more and more of it coming up volunteer
later in the wheat. They haven't docked yet but the place I haul to has
a sign that says that they can dock for vetch. That's the other reason
for getting away from it.
For those organic farmers with a two-year rotation, it seems to be necessary
to apply some nitrogen from an off-farm source, either poultry manure
spread at the rate of about 2 tons per acre or fish emulsion applied
at the rate of about 10 gallons an acre. Dean M. reported that he is
currently paying $20 a ton for poultry manure. Steve B., only one of
the seven farmers interviewed who uses fish emulsion, said that he pays
$3 a gallon for it.
There's a more fundamental difference, however,
between the nutrient management regimes of organic and conventional
farmers than their sources of nitrogen. It is not that organic farmers
are unaware of the short-term, crop-year benefits of adequate soil
nutrients, but rather that they take a long-term and more holistic
view of their farming practices. They understand more than others,
perhaps, the impact that crop rotations, cover crops, crop residues
and manures&emdash;and the timing of these practices
and applications have on the chemical, physical and biological
properties of their soils. Building better soils becomes a goal as important
in and of itself as much so as annual yields of specific crops. Long-term
soil building is considered "money in the bank" by organic
Nelson W. He expressed
well a view of soil building shared by most organic farmers: "We
need to think of the soil as a living organism and we need to feed
it. We need to take care of it and not poison it. If you take care
of it and feed it, it'll work for you. The soil life needs air, water
and it needs something to eat. If you get those three things working,
why you got a lot going for you."