Abstract
![Nutrient Cycling in Pastures](https://webarchive.library.unt.edu/eot2008/20090305040747im_/http://attra.ncat.org/images/nutcycle/nutcycle1.jpg)
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Nutrients in a pasture system cycle through soil organisms, pasture
plants, and grazing livestock. Appropriate management can enhance
the nutrient cycle, increase productivity, and reduce costs. Two
practical indicators of soil health are the number of earthworms
and the percentage of organic matter in the soil. A diversity of
pasture plants growing on healthy soils use sunlight and the nutrient
resources in the soil to effectively produce animal feed. Paddock
design and stocking density can also affect the efficiency of nutrient
cycling in a pasture system. Supplementation of natural fertility,
based on soil tests, balances the soil's mineral composition, resulting
in better plant and animal growth and increased soil health.
Table of Contents
Introduction
When nutrients cycle efficiently in a pasture system, they move
through various soil organisms and pasture plants, then through
the grazing animals, and back to the soil again as manure and urine.
This publication provides a general outline of the nutrient cycle,
and gives pasture managers some guidelines for working with the
many elements of these complex systems. For more detail and more
technical information, refer to the companion ATTRA publication,
Nutrient
Cycling in Pastures.
Pasture managers can effectively increase soil fertility by understanding
the functions of the plants and animals living in and on the soil.
Not only can soil organisms generate mineral nutrients or make them
available, but these same minerals can also be recycled several
times in a growing season, if the soil ecosystem is healthy and
plant cover is optimal. With good management, nutrients can cycle
quickly with minimal losses to air and water. Less fertilizer will
be required, and this means increased profitability for the entire
farm.
Three different groups of living organisms drive the nutrient cycle:
soil organisms, pasture plants, and grazing livestock. Each will
be discussed separately below. They all work together to produce
good-quality soils, which in turn produce good-quality pastures.
Good-quality soils don't erode, since water flows quickly into the
ground and is stored there. Good-quality pastures are springy underfoot,
with deep green forage that covers the soil and a moderate amount
of dead residue under the canopy. They produce nutritious forage
with balanced mineral levels. Livestock find these forages palatable
and thrive on them. Animal manure and plant residues quickly break
down to be used again.
Producers create this kind of soil through good management. They
use smart grazing strategies. They test their soils regularly and
apply fertilizers, lime, and organic amendments as needed. They
monitor the results of these decisions and make note of their observations
for future reference. They understand their forages and adjust stocking
rates and paddock rest periods. They make harvesting and seeding
decisions to maintain and improve their soil and pasture resources.
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Soil Organisms and Nutrient Cycling
The soil is alive with organisms, ranging from visible insects
and earthworms to microscopic bacteria and fungi. These living organisms
are working for the grass farmer, to whom they are extremely important.
We might even refer to them as soil livestock. In fact,
the soil can be viewed as home to a great complexity of life, rather
than just a medium to support plants. An acre of living soil may
contain 900 pounds of earthworms, 2400 pounds of fungi, 1500 pounds
of bacteria, 133 pounds of protozoa, 890 pounds of arthropods and
algae, and even small mammals in some cases. (1)
An understanding of underground biological cycling can enable the
pasture manager to benefit from this herd of soil livestock.
Soil bacteria are the most numerous, with every gram of soil containing
at least a million of these tiny one-celled organisms. There are
many different species of bacteria, each with its own role in the
soil environment. One of the major benefits bacteria provide for
plants is to help them take up nutrients. One of the primary ways
they do this is by releasing nutrients from organic matter and soil
minerals. Certain species release nitrogen, sulfur, phosphorus,
and trace elements from organic matter. Other species break down
some soil minerals and release potassium, phosphorus, magnesium,
calcium, and iron. Still other species make and release plant growth
hormones, which stimulate root activity. Some bacteria, either living
inside the roots of legumes or free-living in the soil, fix nitrogen.
Other services provided to plants by various species of bacteria
include improving soil structure, fighting root diseases, and detoxifying
the soil.
Actinomycetes are thread-like bacteria that look like fungi. While
not as numerous as other bacteria, they perform vital roles in the
soil. Like other bacteria, they help decompose organic matter into
humus, releasing nutrients. They also produce antibiotics to fight
root diseases. And they are responsible for the sweet earthy smell
of biologically active soil.
Fungi come in many different species, sizes, and shapes in soil.
Some species appear as thread-like colonies, while others are one-celled
yeasts. Slime molds and mushrooms are also fungi. Many fungi aid
plants by breaking down organic matter or by releasing nutrients
from soil minerals. Some produce hormones and antibiotics that enhance
root growth and provide disease suppression. There are even species
of fungi that trap harmful plant-parasitic nematodes. Mycorrhizae
are fungi that live either on or in plant roots and act to extend
the reach of root hairs into the soil. Mycorrhizae increase the
uptake of water and nutrients, especially in soils with nutrient
deficiencies. The fungi, in turn, benefit by taking nutrients and
carbohydrates from the plant roots they live with.
Many species of algae also live in the soil. Unlike most other
soil organisms, algae produce their own food through photosynthesis.
They appear as a greenish film on the soil surface following a rain.
Their primary role is to improve soil structure by producing sticky
materials that glue soil particles together into water-stable aggregates.
A soil aggregate looks like a minature crumb of granola. In addition,
some species of algae (the blue-greens) can fix nitrogen, some of
which is later released to plant roots.
Protozoa are free-living animals that crawl or swim in the water
between soil particles. Many soil protozoa species are predatory,
eating other microbes. By consuming bacteria, protozoa speed up
the release of nitrogen and other nutrients through their waste
products.
Nematodes are abundant in most soils, and only a few species are
harmful to plants. The harmless species eat decaying plant litter,
bacteria, fungi, algae, protozoa, and other nematodes. Like the
other soil predators, nematodes speed the rate of nutrient cycling.
Earthworms are good indicators of soil health. Research in New
Zealand pastures has repeatedly shown improved soil qualities where
worms thrive. Studies have also proved that forage production nearly
doubles when worms are introduced and establish themselves in pastures.
This higher production might be attributed to other related changes,
not just the direct activity of the worms themselves. Nevertheless,
there is a demonstrated correlation between worm population and
forage production. (2)
Earthworm burrows enhance water infiltration and soil aeration.
Earthworms pass soil, organic matter, and soil microbes through
their digestive systems as they move through the soil. This process
increases the soil's soluble nutrient content considerably. Worms
eat dead plant material left on top of the soil and redistribute
the organic matter and plant nutrients throughout the soil horizon.
Research shows that a thick layer of dead organic material remains
on the surface in pastures without any worms. Earthworms also secrete
a material that stimulates plant growth. Some increase in plant
growth, as well as the improved soil quality, can be attributed
to this substance. In addition, a Dutch study revealed that worms
reduced the transmission of some parasitic nematodes in cow pats.
(3)
As Charles Griffith of the Noble Foundation has said, you can never
have too many earthworms. He was working toward a goal of 25 per
square foot, but reports from New Zealand mention 40 per square
foot in soils where worms were introduced only seven years earlier.
(4) Earthworms thrive where there is no tillage,
especially in the spring and fall, their most active periods. They
prefer a near-neutral pH, moist soil, and plenty of plant residue
on top. They are sensitive to some pesticides. Fertilizers applied
to the soil surface are often beneficial, but anhydrous ammonia
is deadly, and tillage destroys nightcrawler burrows. Efforts to
protect and increase worm populations will be rewarded with healthier,
more productive pastures.
In addition to earthworms, there are many other species of soil
organisms visible to the naked eye. Among them are dung beetles,
sowbugs, millipedes, centipedes, slugs, snails, and springtails.
These are the primary decomposers. They start eating the large particles
of plant residue. Some bury residue, bringing it in contact with
other soil organisms, which further decompose it. The springtails
eat mostly fungi, and their waste is rich in plant nutrients. All
these organisms—from the tiny bacteria up to the large earthworms
and snails—function together in a whole-soil ecosystem. Because
humans cannot see most of the critters living in the soil and may
not take time to observe the visible ones, it is easy to forget
about them. They are present in biologically active soils and perform
many useful functions, if pastures are managed for their survival.
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Organic Matter is Essential
to Soil Health
Organic matter is critical for storing water and nutrients in the
soil. It holds nutrients in plant-available forms that don't easily
wash away. It creates an open soil structure into which water, dissolved
minerals, and oxygen can move, ready for plants to use. It provides
further nutrient storage in the soil and can disable certain plant
toxins. In addition, beneficial soil organisms depend upon organic
matter as a source of food. These countless tiny plants and animals
create an ecosystem that releases mineral nutrients, increases their
availability to plants, and helps protect plant roots from disease.
Testing for soil organic matter (OM) is a simple way to make sure
there is a functioning community of organisms in the soil. All the
organisms mentioned above, except algae, depend on organic matter
for their food. The primary decomposers start with raw plant residues
and manure. Their by-products are eaten by other species whose wastes
feed still other microbes. After moving through several species,
these raw materials become soluble plant nutrients and humus. The
humus contributes to well-structured soil, which in turn produces
high-quality forage. It is clear that when this soil ecosystem is
working, there are many benefits to the pasture system visible above
ground. The complex ecosystem underground would be hard to evaluate,
but soil organic matter, as measured in regular soil tests, is a
simplified way to monitor the health of this invisible world.
The organic matter test can be requested through local Extension
facilities. This kind of soil analysis measures, by weight, the
percentage of soil that is OM. Organic matter includes minerals
that are part of living organisms, as well as dead plant material
that has not yet been digested. Because organic matter levels are
harder to maintain in warmer, more humid climates, what constitutes
a "high" or "low" percentage will vary in different
parts of the country. Local Extension agents or soil scientists
can help define relative values. A single test will show a beginning
point, and subsequent soil tests can indicate whether progress is
being made toward a higher level of soil organic matter.
Maintaining or building organic matter is the first step to developing
soil humus. Humus results from the final stages of organic matter
decomposition. Favorable biological processes which decompose the
organic matter into humus can be limited or even stopped by lack
of nitrogen, lack of oxygen, unfavorable temperature, or unfavorable
pH. Once stable humus has accumulated in the soil, it has a host
of beneficial effects on plants. These positive effects are directly
related to the presence and diversity of microbial life.
Benefits
of a humus-rich soil include:
- Granulation of soil particles into water-stable aggregates
- Decreased crusting
- Improved internal drainage
- Better water infiltration
- Fixation of atmospheric nitrogen
- Release of bound nutrients
- Increased water and nutrient storage capacity
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Pasture Plants Also Cycle Nutrients
Rhizobium bacteria live in legume root nodules and convert nitrogen
from the air into forms the legume can use. This nitrogen is used
by the plant and generally does not become available to nearby plants
until the legume dies. Some of the nitrogen fixed by white clover,
however, is available as soon as four months into the season. With
red clover, the interval is six months, and alfalfa-fixed nitrogen
takes 6 to 12 months to become available. Although white clover
is credited with fixing less nitrogen than either red clover or
alfalfa, if that nitrogen is available sooner, with efficient nutrient
cycling it could be used more than once in a growing season. It
therefore becomes just as important as other legumes as a source
of new nitrogen in the nutrient cycle. In addition, some nodules
separate naturally from the legume roots during a grazing cycle,
thus becoming available to other plants. Some legumes have "leaky"
nodules and share more of their fixed nitrogen than others.
A nitrogen molecule can be fixed by white clover in one day. If
eaten by a cow and excreted in urine, it could take as little as
two weeks before it's again available in plant tissue. If the clover
isn't eaten directly, the nitrogen that it harvested from the air
may naturally become available to nearby grasses in as little as
four months. Nitrogen in a leaf that falls on biologically active
soil can be used again in the same growing season.
A final way in which nutrients become available to the forage plants
(and thus to the grazing animal) is through the action of deeply
rooted plants. Trees, many broadleaf weeds, and forages such as
alfalfa have taproots that go deep into the soil horizon where some
grass roots cannot reach. The nutrients from these deeper soil levels
are used by the plant, but become available at the soil surface
once the tree leaves fall or the weeds die, decompose, and release
their nutrients.
The roots constitute at least half the weight of a grass plant.
Many native warm-season perennial grasses have root systems that
reach six feet or more into the soil horizon. They occupy a huge
underground area and form a network that holds the soil in place.
Every year 20-50% of this mass, as well as all of the top growth
in temperate climates, dies and becomes organic matter which, in
biologically active soil, is broken down quickly. Cool-season grasses
also contribute organic matter through root and shoot dieback.
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Grazing Livestock Affect Pasture
Nutrient Cycles
Livestock feeding on pasture use a small proportion of the minerals they ingest in forages to build bones, meat, and hide. The rest is excreted in dung and urine. In general, urine contains most of the nitrogen (N) and potassium (K) wastes, and dung contains most of the phosphorus (P) the animals don't use. Refer to the box below page six to learn about the value of urine and dung in pastures.
Value Of NPK In Manure
And Urine |
One 1000-pound cow produces 50-60 lbs. of
manure and urine per day, which contains: |
0.35 lb. N @ 24¢/lb. |
= 8¢ N |
0.23 lb. P @ 22¢/lb. |
= 5¢ P |
0.28 lb. K @ 14¢/lb. |
= 5¢ K |
Total NPK |
= 17¢ |
Therefore: |
|
10 cows |
$ 1.70/day |
100 cows |
$ 17.00/day |
500 cows |
$ 85.00/day |
Note: If you add the value of organic matter
and trace minerals in the manure, the total value of the manure
doubles! |
Source: Salatin,
Joel. 1993. One Cow Day of Manure: What's It Worth. Stockman
Grass Farmer. September. p. 11. |
Nutrients in urine are soluble and move in the soil solution to
the roots. When N and K are present at higher levels in the feed,
they are excreted in manure as well. The liquid forms can be taken
up by a plant at once and are then very quickly available again
as food. Sheep, which do not avoid urine spots as cattle do, can
immediately cycle this mineral again.
Phosphorus and some other minerals cycle through animals primarily
in manure. It can take from six months to two years for manure to
break down and for the phosphorus to cycle back into the plants.
The speed of the cycle is affected by various biological agents
as well as by mechanical means. Dung beetles bury manure with their
eggs in burrows. This activity not only places the minerals back
into the soil where plant roots can use them but it prevents fly
eggs from hatching as well. Some pesticides designed to control
livestock parasites unfortunately kill dung beetles as well. This
side effect can deal a serious blow to the ability of the natural
ecosystem to function. For more information on this subject see
Dung Beetle Benefits
in the Pasture Ecosystem.
Other agents that help to break up manure piles include ants, birds,
and earthworms. Pesticides that are lethal to these non-target species
can thus have unforeseen negative consequences for nutrient availability.
If dragging or clipping is economical, these operations physically
scatter the dung so that smaller organisms can cycle it. The potential
of creating a larger area of forage rejection, however, is a consideration.
Another negative effect is that more nutrients are lost into the
air during mechanical scattering.
To recapture and evenly distribute these nutrients for soil organisms
and plants to use requires some knowledge about grazing behavior.
In smaller paddocks, with high stock density, urine and dung are
more evenly distributed than in large ones. Livestock are less selective
in their grazing habits and space themselves more evenly within
the area allotted for a grazing period. They will graze closer to
dung piles and exhibit less avoidance of urine spots so that more
forage is used for animal production.
In large areas, cattle act as a herd and go to water together.
When water is available nearby, however, animals drink individually
and return to graze in other areas. If they must travel in a lane
to the water, manure will concentrate in these non-productive areas
en route. When there is not enough room at the water tank for all
to water at once, those waiting will manure that area, concentrating
nutrients where they are less likely to contribute to plant and
animal productivity.
Good management helps distribute nutrients that will feed soil
microbes and encourage healthy soil ecosystems. Locating water,
minerals, shade, and fly-control devices in different parts of the
paddock also discourages nutrient concentration. It is even more
beneficial if these high-use areas can be relocated for each grazing
cycle or placed in areas that would not otherwise attract livestock
use. Supplemental feed, likewise, should be placed either where
nutrients are needed or under the fence. The location should vary
with each feeding.
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Nutrient Cycling in Relation
to Other Natural Cycles
Two other cycles—water and energy—interact with the
nutrient cycle. They are separated for purposes of discussion here,
but in reality they function as a whole system.
Water Cycle
Water is a nutrient, in one sense, since it is one of the raw ingredients
used by plants to make carbohydrates. It is also key to nutrient
cycling because plant nutrients are soluble and move with water.
Downward leaching of plant nutrients occurs with water movement.
Soil itself moves in water, taking with it insoluble nutrients such
as phosphorus. The area around roots must be moist, since nutrients
are taken up dissolved in water.
Management determines how effective the water cycle will be in
pastures. If rainwater can enter the soil easily, runoff losses
are less. Maximum infiltration of rainfall keeps groundwater tables
charged up, wells running year round, and drought damage to a minimum.
Soil surface conditions that foster high rainwater intake are abundant
ground cover (by living plants and surface litter) and good soil
aggregation. The best-aggregated soils are those that have been
in well-managed perennial grass. (5) Though
aggregation can be maintained under crops, the perennial activity
of grass provides both aggregate-forming processes and aggregate-stabilizing
humus.
A grass sod extends a mass of fine roots throughout the topsoil.
The grass sod also provides protection from raindrop impact. A moderate
amount of thatch continually provides food for soil microorganisms
and earthworms that generate the glue-like substances that bind
aggregates into water-stable units. The dead material, as well as
the plants themselves, shade the soil, maintaining a cooler temperature
and higher humidity at the soil surface.
Conditions that reduce water intake and percolation are bare ground,
surface crusting, compaction, and soil erosion. These conditions
are not usually present in well-managed perennial pastures. Bare
ground leads to erosion, crusting, and weeds. Crusting seals the
soil surface when the soil aggregates break down. Excessive trampling—especially
in wet conditions—and the impact of falling raindrops on bare
soil are two common causes of crusting. Therefore, it is important
to move water sources, feedbunks, and minerals before bare ground
and crusting develop.
Energy Cycle
The energy cycle is powered by sunlight, which plants convert into
carbohydrates. In order to capture the most solar energy, the plant
canopy needs to be very dense. If the pasture has both broadleaf
plants and grasses, the different leaf orientations further increase
energy transformation. Taller plants receive light, even at the
extreme angles of sunrise and sunset. Horizontal leaves capture
the noon sun better than upright grass leaves. Increased efficiency
in energy conversion can be achieved if the pasture is considered
a three-dimensional solar collector. Even trees, if they are trimmed
high and do not make dense shade, contribute to such a system.
Energy from plants is also transferred into the soil ecosystem
through the death and decay of plant roots and residue. The plant
roots and residue are decomposed first by soil-dwelling insects
and other primary decomposers. The waste and by-products from the
primary decomposers are broken down still further by secondary decomposers.
Finally the components of the residue become humus. At each step
of the decomposition process, energy is either being used to create
the next generation of decomposer or is lost as heat. The energy
cycle and the nutrient and water cycles require a biologically active
soil to function.
A thick stand of green plants covering the soil for as long a time
as possible creates high energy flow. This good-quality forage,
provided to livestock at the right stage of maturity, is the next
link in the energy cycle. Livestock convert plant material into
meat, milk, and fiber. The leftovers become urine and manure. Livestock
products are sold, and the waste products again cycle through the
decomposer organisms. Minimal loss of energy depends on proper stocking
rates, good decisions about when animals are moved, and how much
rest the plants require.
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Supplementing the Nutrient Cycle
One of the first steps in assessing the nutrient cycle on any farm
is to consider nutrient inputs and outputs. In what forms do nutrients
enter the farm? What nutrients leave and in what form? What nutrients
are generated or made available on the farm? The box below provides
some examples.
Farm Nutrient
Budget
Nutrients imported to the farm in:
- Purchased livestock
- Chemical fertilizers
- Manures from off-farm (credit for multiple years)
- Livestock feed (grain, hay)
- Wind and water
Nutrients generated on the farm:
- Atmospheric nitrogen captured by legumes
- Rock minerals dissolved by microbial acids
- Subsoil minerals mined by deep roots of trees and other
plants
- Nutrients made available to the crop by changes in pH
Nutrients exported from the farm:
- In products sold (crops, livestock)
- By wind and water (erosion)
- By leaching into groundwater
- Volatilized as gas
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Lime is a particularly important amendment in pasture management.
While it has always been considered necessary for adjusting pH,
there is growing evidence that the amount of calcium has important
consequences for plant production and animal health. Allan Nation,
editor of The Stockman Grass Farmer and student of grass-based
livestock systems, listed many reasons to apply agricultural lime
annually. His list is reproduced below.
Lime
200-500 lbs. of finely ground, face-powder-consistency ag lime applied annually:
- Helps prevent weeds such as dandelion, plantain, chickweed, and buttercup.
- Helps with the movement and absorption of phosphorus, nitrogen, and magnesium.
- Benefits bacteria, fungi, protozoa and other soil life so important for nutrient cycling.
- Releases important trace and growth nutrients by its pH-altering effect.
- Helps clover, which requires twice the calcium of grass. Abundant calcium is necessary for clover nodulation. No lime, little clover.
- Creates soil tilth and structure so that air and water can move more freely through soil by causing clay particles to stick together. Soil must be able to breathe to grow great grass.
- Allows pastures to hang on longer in a drought.
- Improves the palatability of grass and clover, makes the pasture softer for animals to graze, and lessens grass-pulling in new stands.
- Reportedly makes an animal more docile and content.
Source: Nation, Allan. 1995. Quality Pasture-Part II. Stockman Grass Farmer. January. p. 13. |
Soil tests, taken according to recommended procedures (consult
Extension), provide a basic analysis of plant nutrient levels in
a pasture. Fertilizer recommendations that accompany test results,
however, are typically based on the assumption that forages will
be harvested and removed from the area. In a grazing system this
is not necessarily so.
Supplementing the nutrient cycle with commercial fertilizers, compost,
or manure can increase both plant and animal production, which will,
in turn, increase soil organic matter. In the early years of a pasture
improvement plan, adding small amounts of fertilizer several times
during the growing season is a good way to increase the amount of
available forage. With good grazing management, more forage will
translate into more pounds of livestock as well as increased soil
organic matter.
To back up a fertilization program, forage samples can be taken
to see what effect the fertilizer has had. Strategic forage-tissue
testing can be done by taking samples between areas of poor and
good growth or by making before- and after-fertilizer comparisons.
County Extension agents or private consultants can explain how to
take a forage sample. Because samples are analyzed for the purpose
of ration balancing or to assess actual mineral content, it is necessary
to specify the latter to learn whether fertilizers are achieving
their purpose. More information on soils is available in the ATTRA
publications Pastures:
Sustainable Management, Alternative
Soil Testing Laboratories and Assessing
the Pasture Soil Resource.
Sole reliance on commercial fertilizer short-circuits the natural
mineral cycle. High fertilization coupled with frequent harvesting
of hay speeds organic matter decomposition and releases minerals
faster than plants growing on the site can absorb them. As a result,
nutrients are leached deeper into the soil, out of the reach of
plant roots, or they are lost to run off. The use of some commercial
fertilizer is always an option to be exercised when necessary. However,
continuing to look for ways to use natural systems to produce nutritious
forage and healthy animals, while lessening one's dependence on
purchased, non-renewable resources, is worthwhile.
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Conclusion
This publication has described the many paths travelled by pasture
nutrients. While some minerals leave the farm as animal products,
the majority move through a series of living beings in a continuous
cycle. Some nutrients escape to the air, some are lost to water
erosion, and some leach down past the reach of forage plant roots.
The grazier who understands these cycles and their interactions
can, by making smart daily decisions, retain more nutrients on site.
The health and growth of the grazing livestock depend on high-quality
pastures, which in turn spring from the soil "livestock"
in a balanced underground ecosystem. Soil organic matter and earthworm
numbers are simple indicators that producers can use to monitor
soil health. Good grazing management, based in part on a basic understanding
of grazing behavior, combined with a knowledge of how animals affect
the whole pasture system, contributes to lush pastures that livestock
need only to harvest. Then, with good marketing, profit is the natural
result!
For more in-depth discussion of the topics raised in this publication,
consult the companion ATTRA booklet, Nutrient
Cycling in Pastures. Some other good resources are listed
below.
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References
- Pimentel, David et al. 1995. Environmental
and economic costs of soil erosion and conservation benefits.
Science. Vol. 267, No. 24. p. 1117-1122.
- Stockdill, S.M.J. 1966. The effect
of earthworms on pastures. Proceedings: New Zealand Ecological
Society. Volume 13. p. 68-75.
- Gronvold, Jorn. 1987. Field experiment
on the ability of earthworms (Lumbrididae) to reduce the transmission
of infective larvae of Cooperia oncophora (Trichostrongylidae)
from cow pats to grass. Journal of Parasitology. Vol. 73, No.
6. p. 1133-1137.
- Stockdill, S.M.J. 1959. Earthworms
improve pasture growth. New Zealand Journal of Agriculture. March.
p. 227-233.
- Allison, F.E. 1968. Soil aggregation-some
facts and fallacies as seen by a microbiologist. Soil Science.
Vol. 106, No. 2. p. 136-143.
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Further Resources
Proceedings
Joost, Richard E. and Craig A. Roberts. 1996. Nutrient
Cycling in Forage Systems. Proceedings of a Symposium
held March 7-8, 1996, Columbia, MO. Potash and Phosphate Institute
and Foundation for Agronomic Research, Manhattan, KS. 243 p.
Anyone interested in pursuing this subject further should
obtain a copy of this book. It contains many bibliographic references.
Available for $15 ppd. from:
Potash and Phosphate Institute
772 22nd Ave. S.
Brooking, SD 57006
(605) 692-6280
Periodicals
These carry articles on practical aspects of grazing management,
including nutrient cycling.
The Forage Leader
American Forage and Grassland Council
P.O. Box 891
Georgetown, TX 78627
(800) 944-2342
Graze
P.O. Box 48
Belleville, WI 53508
(608) 455-3311
$30 for 1-year subscription (10 issues)
Hay and Forage Grower
Webb Division
Intertec Publishing Corp.
9800 Metcalf
Overland Park, KS 66212-2215
(800) 441-0294.
Pasture Prophet
Grazing Lands Technology Institute
Pasture Systems and Watershed Research Laboratory
Building 3702, Curtin Rd.
University Park, PA 16802-3702
The Stockman Grass
Farmer
282 Commerce Park Drive
Ridgeland, MS 39157
(601) 853-1861
(601) 853-8087 FAX.
(800) 748-9808
Electronic Listservs
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To subscribe send an e-mail to: graze-l@witt.ac.nz
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The Grazer's Edge
To subscribe send an e-mail to: grazersedge-subscribe@onelist.com
In the body of the e-mail type "subscribe grazersedge"
Web Sites
Soil Foodweb, Inc.
More detail on the underground soil ecosystem and its above-ground
interactions can be found on this website.
A Brief Overview of Nutrient Cycling in Pastures
By Alice E. Beetz
NCAT Agriculture Specialist
Richard Earles, Editor
Cole Loeffler, HTML Production
CT 221
Slot 221
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