This document discusses managing pasture ecosystems by considering the interactions between plants, animals, soil organisms, and nutrient cycles that are often invisible. As pasture managers, we harvest solar energy through plants and convert it to food and fiber through grazing animals, while maintaining nutrient cycling and soil health. A diverse community of soil organisms like bacteria, fungi, protozoa, nematodes, arthropods, and earthworms cycle nutrients, aerate soil, hold water and support plant growth. Management aims to maintain this below-ground ecosystem through practices like maintaining soil organic matter, nutrient recycling, and grazing management. Understanding the soil food web allows for better holistic management of pasturelands.

1. Pasture Ecology - Managing
Things That We Cannot See.
Ed Rayburn
Extension Specialist
West Virginia University
erayburn@wvu.edu

2. Pasture-Based Livestock Producers
• In business harvesting solar energy.
• Converting solar energy into food and fiber
products for people.
• Manage
– plants to optimize harvest of solar energy,
– animals to transfer that energy into livestock products,
– cycling of mineral nutrients in the landscape
– to make business socially, economically, and
environmentally sustainable.
• Are pasture ecosystem managers.

3. Energy Flow and Nutrient Cycles

4. Generalized Nutrient Cycle

5. Soil Organic Matter
• Plant residues (dead plant material, course OM)
• Active organic matter (rapid decomposition)
• Slow organic matter (slow decomposition)
• Passive organic matter (stable OM)

6. Citizens of the Soil Community
• Plant roots and root nodules
• Earthworms
• Slugs and snails
• Nematodes
• Woodlice
• Spiders and Mites
• Centipedes and Millipedes
• Spring tails
• Beetles
• Ants and Termites
• Bacteria and Actinomycetes
• Protozoa
• Fungus

7. Soil Citizens Provide Community Services
• Nitrogen fixation
• Nutrient cycling
– shredders
– decomposers
– predators
• Soil structure and aeration
– water infiltration, holding capacity
• Soil moisture affects microbial activity
• Each has an optimum environment
• Redundancy of functional species with different optima
• Each has a niches
• All participate in the soil food web

10. Photos From
NRCS Soil Biology Web Site
http://soils.usda.gov/sqi/concepts/
soil_biology/biology.html

11. Earthworms (3 niches)

12. Earthworms

15. Arthropods (Insects and Relatives)

17. Dung Beetles (3 niches)
Dung Beetles of Central and Eastern North Carolina Cattle Pastures
http://www.cals.ncsu.edu/entomology/guidetoncdungbeetles.pdf

18. http://www.cals.ncsu.edu/entomology/guidetoncdungbeetles.pdf

19. Slugs and Snails
• Primary consumers
• Shredders
• Predators
http://www.backyardnature.net/snail_sl.htm

20. Bacteria
• Decomposers
– immobilize nutrients in cells
– make energy and nutrients available
• Mutualists partner with plants
– nitrogen-fixing bacteria
• Pathogens
• Chemoautotrophs
– obtains energy from nitrogen, sulfur, iron
or hydrogen not carbon compounds

21. Bacteria Services
• Nutrient cycling
– decomposition
– hold nutrients
• Disease suppression
– compete with disease-causing organisms below and above ground
• Water movement
– substances bind soil particles into stable aggregates
– water infiltration
– water-holding capacity
• Symbiotic bacteria with legumes
– convert nitrogen from air to form plant can use
• Nitrifying bacteria
– change ammonium (NH4+) to nitrite (NO2-) then to nitrate (NO3-)
• Denitrifying bacteria
– convert nitrate to nitrogen (N2) or nitrous oxide (N2O) gas
• Actinomycetes
– decompose hard-to-decompose compounds, chitin and cellulose

22. Protozoa Help With Nutrient Cycling By
Feeding on Bacteria

23. Protozoa Come in Three Forms,
Amoeba, Flagellates, Ciliates

24. Free-Living Nematodes (4-types)
• Bacterial-feeders consume bacteria.
• Fungal-feeders puncture cell wall of fungi and
suck out the internal contents.
• Predatory eat other nematodes and protozoa.
• Omnivores eat a variety of organisms or may
have a different diet at each life stage.
• (Root-feeding nematodes are plant parasites,
and are not free-living in the soil)

25. Nematodes
• Fungal-feeding • Bacterial-feeding

26. Fungi
• Decompose OM
• Glomalin secretion
develops soil structure
• Extract nutrients
• Hold nutrients

27. Fungi Help Plants Extract Nutrients
From Soil

28. Arbuscular Mycorrhizal Fungus (AM)

29. Ectomycorrhizae Important To Trees

30. Basic Nutrient Cycling
• Plant, bacteria and fungus
– extract N from air or soil
– extract macro and micro minerals from soil
• Plant consumed by herbivore or dies
• Herbivores deposit manure and urine
• Shredders break large material into small bits
• Bacteria consume rapidly degraded CHOs (sugars etc.)
• Bacteria consume less degradable CHOs (fiber)
• Fungi and actinomycetes consume even less degradable
CHOs (fiber and lignin)
• Macro and micro minerals released for plants
• Organic forms of P and micro minerals more available to
plants

33. Community Interactions
• Legume, bacteria
• Legume, bacteria, and grass
• Legume, bacteria, fungus, and grass

34. N Transfer From Legume (Clover & Bacteria) to
Grass In a New Seeding.
25
20
Ryegrass w/
Ryegrass CP%
15
ladino clover
Ryegrass w/o
ladino clover
10
5
0
1-Feb 2-Apr 1-Jun 31-Jul 29-Sep 28-Nov 27-Jan

35. Transfers Between Legumes, Grasses, and Soil
By Way of Mycorrhizae.

36. Community Interactions
• Bacteria and nematodes
• Bacteria, mites, and nematodes

37. Interactions
• Nematodes eat bacteria
• Mites eat nematode
• Nematodes eat fungus
• Fungi eat nematodes

38. Healthy Soil Ecology Balance of
• Food supply (organic matter with
adequate macro- and micro mineral
nutrients)
• Physical environment above and below
ground (cover and habitat at all scales)
• Healthy consumers, omnivores, predators,
and predators of predators (diversity)
• Chemical environment (soil oxygen, pH,
fertility)
• Thermal and moisture environment

39. Management Needed to Help the
System (a)
• Soil pH 6.0-7.0 depending on the legume
• Adequate not excessive soil P and K
• Inoculate legume seed with proper bacteria
• Manage nutrients on the farm
– (recycle manure, urine, and organic residues)
• Proper grazing management
– timing and intensity suitable for the forage mixture
• Proper fall grazing
– develop tillers in grasses and stolons of white clovers
– reduce adult clover root curculio activity

40. Management Needed to Help the
System (b)
• Rest pastures to get cover for night
crawlers
• Legumes for livestock and earthworms
– they prefer legumes over grasses
• Fly control friendly to dung beetles
• Weed control friendly to legumes and soil
micro organisms
• Co-graze livestock
– convert “weeds” to animal feed and manure

41. Take Home
• Above ground we manage plants with animals to capture
solar energy, convert it into marketable livestock
products, cycle nutrients so that our pasture system can
be sustainable.
• This management influences soil organic matter to feed
macro- and microorganisms in the soil.
• This affects the soil’s physical condition, availability of
macro- and micronutrients and soil moisture to plants.
• Understanding how management affects the soil
community assists us in our management of the entire
pasture ecosystem.

42. NRCS Soil Biology
Web Site
http://soils.usda.gov/sqi/concepts/
soil_biology/biology.html

43. Dung Beetles
Dung Beetles of Central and Eastern North Carolina Cattle Pastures
http://www.cals.ncsu.edu/entomology/guidetoncdungbeetles.pdf

44. • http://www.soilfoodweb.com/