Happy Critters Healthy Soils

Mark Scarpitti, CCA State Agronomist, Ohio NRCS (740) 653-1500 ext 103 [email protected]

Bacteria

Are single cell organisms (and are therefore microscopic) • There are 100 MILLION to 1 BILLION bacteria in just 1 TEASPOON of soil!!!

What Bacteria Do

• They are decomposers, eating dead plant material and organisms' waste • The bacteria release nutrients Do you know what soil smells like? Actinomycetes, a unique type of bacteria, cause that smell, and it is a good sign of healthy soil.

Actually, people have been smelling soil for many, many years as a way to judge if the land is good for planting.

A Few Important Bacteria

Nitrogen-fixing bacteria form symbiotic associations with the roots of legumes • The plant supplies to the bacteria and the bacteria convert nitrogen (N2) from air into a form the plant can use. • When leaves or roots from the host plant decompose, nitrogen is released in the surrounding soil.

Nodules formed where Rhizobium bacteria infected soybean roots

A Few Important Bacteria

Denitrifying bacteria convert nitrate to nitrogen (N2) or nitrous oxide (N2O) gas Denitrifiers are anaerobic, meaning they are active where oxygen is absent, such as in saturated soils or inside soil aggregates Nitrogen loss can result in yellow looking corn plants

A Few Important Bacteria

Nitrifying bacteria change ammonium (NH4+) to nitrite (NO2-) then to nitrate (NO3-) – a preferred form of nitrogen for grasses and most row crops. Nitrate is leached more easily from the soil, so some farmers use nitrification inhibitors to reduce the activity of one type of nitrifying bacteria.

FUNGI

Fungi are organisms • They are not plants, nor are they animals • They group themselves into strings called hyphae The hyphae then form groups called mycelium. They are less than an 1/32 of an inch wide but can get as long as several meters.

The Good and Bad and the Fungi

They are helpful but can also be harmful

Fungi are helpful

• because they have the ability to break down nutrients that other organisms cannot • Fungi release them into the soil, and other organisms get to use them • Fungi can attach themselves to plant roots. Most plants grow much better when this happens.

• This is a good relationship called mycorriza

The Good and Bad and the Fungi

They are helpful but can also be harmful

Some Fungi can be harmful

• Fungi can get food by being parasites, attaching themselves to plants or other organisms, but offering nothing in return

A Few Important Fungi

Decomposers – saprophytic fungi – convert dead organic material into fungal biomass, carbon dioxide (CO2), and small molecules, such as organic acids. Like bacteria, fungi are important for immobilizing, or retaining, nutrients in the soil.

A Few Important Fungi

Many byproducts of fungi are organic acids:

• Humic-acid rich organic matter is resistant to degradation for hundreds of years Like bacteria, fungi are important for immobilizing, or retaining, nutrients in the soil.

A Few Important Fungi

Mutualists – the mycorrhizal fungi – colonize plant roots. In exchange for carbon from the plant, mycorrhizal fungi bring soil nutrients (phosphorus, nitrogen, micronutrients, and water) to the plant One major group of mycorrhizae, the ectomycorrhizae grow on the surface layers of the roots

MYCORRHIZAL FUNGI IN AGRICULTURE

Mycorrhiza: a symbiotic association between fungi and plant roots

• Fungi can serve as a bridge to bring nutrients to plant roots • Under dry conditions, fungi can bring moisture to the roots they colonize

MYCORRHIZAL FUNGI IN AGRICULTURE

Practices that affect the formation of mycorrhizae: • Mycorrhizal fungi will decline in fallowed fields • Mycorrhizal fungi will increase in fields planted to diverse crops or cover crops • Tillage drastically reduces fungi • Broad spectrum fungicides are toxic to mycorrhizal fungi • High levels of fertilizer reduces inoculation of roots

PROTOZOA

Protozoa are organisms that have only one cell, and are microscopic, but larger than bacteria They are grouped by the ways they move: • • • Amoebae use a psuedo (fake) foot Ciliates have cilia (short hair) and move very fast Flagellates have flagella (whips) and move very fast

PROTOZOA

Protozoa need:

• Bacteria to eat • And water in which to move So moisture determines which types of protozoa will be present and active.

Like bacteria, protozoa are particularly active in the rhizosphere next to roots

Cool Things About

PROTOZOA

Protozoa eat bacteria • • Bacteria have a C:N ratio of about 3:1 Protozoa have a C:N ratio of about 10:1 This means that protozoa do not need all the nitrogen they consume and so excrete nitrogen in a plant available form Bacteria Ingested by an Ameba

WHAT DO PROTOZOA DO?

Protozoa

• Mineralize nutrients • Regulate bacteria populations • Serve as a food source for other organisms • Help suppress disease by feeding on pathogens

NEMATODES

Worms typically 1/500 of an inch (50 µm) in diameter and 1/20 of an inch (1 mm) in length Most nematodes in the soil are not plant parasites. Beneficial nematodes help control disease and cycle nutrients.

Credit: Elaine R. Ingham, Oregon State University, Corvallis

NEMATODES

There are a few species responsible for plant diseases, but not much is known about the majority of nematodes that are beneficial This bacterial-feeding nematode, Elaphonema, has ornate lip structures that distinguish it from other nematodes. Bacterial-feeders release plant-available nitrogen when they consume bacteria.

Credit: Elaine R. Ingham, Oregon State University, Corvallis

WHAT DO NEMATODES DO?

Nutrient cycling:

Like protozoa, nematodes are important in mineralizing, or releasing, nutrients in plant available forms A predatory nematode consumes a smaller nematode.

Credit: Kathy Merrifield, Oregon State University, Corvallis.

Root Feeding Nematode:

WHAT DO NEMATODES DO?

•

Disease suppression:

Some nematodes cause disease • Others consume disease-causing organisms, such as root-feeding nematodes, or prevent their access to roots •

These may be potential biocontrol agents

WHAT DO NEMATODES DO?

Disperse microbes:

Nematodes help distribute bacteria and fungi through the soil by carrying live and dormant microbes on their surfaces and in their digestive systems.

ARTHROPODS

Arthropods are invertebrates - they have no backbone Rather they have a covering called an exoskeleton.

Sowbugs are relatives of crabs and lobsters. Their powerful mouth-parts are used to fragment plant residue and leaf litter.

Credit: Gerhard Eisenbeis and

Wilfried Wichard. 1987. Atlas on the Biology of Soil Arthropods.

Springer-Verlag, New York. P. 111.

WHAT DO ARTHROPODS DO?

Although the plant feeders can become pests, most arthropods perform beneficial functions in the soil plant system

WHAT DO ARTHROPODS DO?

•

Shred organic material

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Stimulate microbial activity

•

Mineralize plant nutrients

ARTHROPODS IN AGRICULTURE Control pests:

Some arthropods can be damaging to crop yields, but many others eat various root- and foliage-feeders Tillage and insecticide application have enormous effects on non- target species in the food web Intense land use (especially monoculture, tillage, and pesticides) depletes soil diversity As total soil diversity declines, predator populations drop sharply and harmful populations can reproduce exponentially

EARTHWORMS

Of all the members of the soil food web, earthworms need the least introduction Their presence is usually an indicator of a healthy system

Earthworms mix the soil

As they consume organic matter and mineral particles, earthworms excrete casts, a type of soil aggregate.

EARTHWORMS IN AGRICULTURE

Earthworm cocoons

One or two worms will hatch from a cocoon after several weeks. L. terrestris cocoons are about a quarter inch long.

Credit: Clive A. Edwards, The Ohio State University, Columbus

Decomposers

Earthworm pulled plant residue into burrow

EARTHWORMS IN AGRICULTURE

Increase infiltration.

Earthworms enhance porosity as they move through the soil. Some species make permanent burrows deep into the soil.

Bury and shred plant residue

Earthworms eat residue, digest and excrete rich organic matter

Conclusions

• A healthy soil will contain an abundant, diverse population of soil organisms • A diverse healthy population of soil organisms can self regulate and is sustainable

Conclusions

The best tools we have to nurture an abundant, diverse population of soil organisms • No Tillage Cropping Systems (when you till, you kill) • A diverse Conservation Crop Rotation and/or use of diverse Cover Crop mixes • Maintaining a living root year round through the use of a diverse Conservation Crop Rotation and/or use of diverse Cover Crop mixes