The Food Web is Complex – From Microorganisms to People
There is no beginning and no end to the Food Web. Just as there is no waste. From the microscopic organisms in your soil to your dinner table, there is a continuum of eaters and eaten. On your farm, do you have any gaps in that continuum? How can you tell if you have the proper microorganisms?
This is an indication of the soil health of your field…
The Robins have lined up in formation and are walking your fields eating bugs and pulling earthworms out of their burrows. We’ve all seen this, and it looks like a well-rehearsed military drill, but are you seeing those Robins in your fields? If not, you may be lacking some tenants.
An Indicator of a Full House
There are many tenants we can’t see, but an indication they are there is that Robin formation. The favorite food of Robins is earthworms, and earthworms will only live in healthy soil. Your farm ecosystem can only be healthy if you have microorganisms, arthropods, flying insects, birds, and a few larger mammals.
Earthworms are detritivores, they consume decomposing plant and animal matter. In their quest for food, they create tunnels that help air and water permeate the soil. Abandoned tunnels are useful for plant roots because worms line their tunnels with partially decomposed plant material and castings that together are what we call humus.
But Earthworms Aren’t Your Only TenantsIn fact, there are far fewer earthworms in your soil than almost all other soil critters. Microorganisms such as fungi, bacteria, and protozoa make up the majority of your tenants. According to Alan Burges, in a gram of fine garden soil there are:
- 2,500 million bacteria
- 700,000 million actinomycetes (ray fungi)
- 400,000 million fungi
- 50,000 million algae
- 50,000 million protozoa
The Microorganisms That Occupy Your SoilMicroorganisms exist in soil as a community. That community is stronger and healthier when your soil is humus-rich. That means that humic and fulvic acids are the underpinning of your community. Humic acid can only be found naturally in undisturbed soil, so the chances are very good you may need to add humic acid to balance your soil. But acids aren’t all that is in your soil. Let’s look at some of your other tenants.
The Bacteria Family
Most bacteria are beneficial and desired tenants. Bacteria fall into three functional groups: decomposers, mutualists, and pathogens. Let’s look at how these function in your soil.
These bacteria consume simple sugars such as root exudates and fresh plant litter. Some decomposing bacteria even break down pesticides and pollutants in the soil.
These bacteria form partnerships with plants. They are especially concentrated in the rhizosphere, next to and in the roots of plants. They bring plants nutrients in exchange for root exudates from the plant. They may also help the plant fix nitrogen from the air.
This is actually a small part of the overall bacterial community living in the soil. If your soil is in balance, the other types of bacteria, as well as fungi and protozoa, will keep these under control.
The other large community living in your soil is the fungi. Like bacteria, there are many different species of fungi. Some you may never see, and some you know as mushrooms.
The Fungi Family
Fungi convert hard-to-digest organic matter. Fungi are also important for disease suppression, water dynamics, and nutrient recycling. For the sake of simplicity, let’s divide them into three different functional groups.
They decompose the rougher, more dense decaying matter. If you roll over a log in the woods, you will find white or pale-yellow fungal hyphae (strands) decomposing the wood. They convert lignin and cellulose into smaller molecules and organic acids, such as humic acid.
These are fungi that form relationships with plants. These relationships are necessary for the health of 80 to 90 % of plants. There are numerous types of mutualists, and most of them are specialized. Some form relationships with trees, some with the exterior of root cells, and some enter root cells. Mycorrhizae fungi grow on the exterior of the root cells and are often found in crops that are grasses, row crops, or vegetables. They extend the zone of nutrient availability far beyond the plant’s roots by weaving their hyphae (strands) between soil particles, roots, and rocks foraging for soil nutrients.
Just as there are a few bad apples in the bacteria family, there also are a number of fungi that can cause harm to your crops. These are usually well-known by farmers as Verticillium, Pythium, and Rhizoctonia.
Most fungi help control disease and even trap and parasitize disease-causing nematodes. Some species of fungi are used as biocontrols.
Another microorganism family that calls your soil home is the nematodes.
The Nematode Family
There are an incredible variety of nematodes. Most farmers think of nematodes as destructive, but in a balanced soil, the beneficial nematodes will take care of their pathogenic cousins.
Nematodes in the soil can be compared to cattle on pasture. They graze on just about everything: bacteria, fungi, protozoa, and even other nematodes. They either eat the organism whole or scrape away at it until they can get to the prey’s internal body parts. Nematodes help keep the whole system in balance.
Another microorganism in the soil, that may be eaten by a nematode, is protozoa.
Protozoa regulate bacteria populations. They also emit excess nitrogen to soil because the bacteria they eat has too high a carbon/nitrogen ratio for them. They expel excess nitrogen in the form of ammonium which is taken up by other soil microorganisms and plant roots. Protozoa also feed on pathogens, so they help suppress disease.
All this talk about microorganisms can get a bit weary. What about the tenants on your farm you can see? They are there only because the microorganisms are in balance. Even some visible tenants take quite an effort to see. Earthworms are a prime example.
And there are some tenants you wish you didn’t have, but they’re all critical to a happy functioning community. Let’s take a look at insects because even wasps have their benefits.
Do You Have Room for Insects on Your Farm?
The insect world is a fascinating place. There are so many different species of insects, and almost all of them are beneficial. There are some, like aphids, cabbage and tomato worms, and flea beetles that you probably don’t want hanging around your farm except…
The Wasp Family
We very seldom think of wasps without pulling out the bug spray whenever we see a nest. But think of all the benefits before you spray again.
- Paper wasps eat caterpillars, earworms, beetles, and flies. Yes, they will sting you, but only if you threaten their paper nest.
- The Braconid wasp lays its eggs in the larvae of pest insects such as caterpillars, earworms, and whiteflies. It is extremely small, so you will not see it, but if you find a caterpillar with white eggs on its back, don’t destroy it, those are Braconid pupa. That caterpillar won’t eat anything more and, in a few weeks, it will be a crusty shell on your plant stem.
If the wasp nest is near your door or you are allergic to wasp stings, then you might have to eradicate them. But usually, they go about their business collecting nectar, pollen, and pollinating your crops.
Let’s take a side trip here and look at how your crop is pollinated. Wasps do pollinate your crops, but they are far outnumbered by all the different sizes and shapes of bees.
The Bee Family
Bees are a major pollinator of crops and the flowers in your yard. The honeybee we are familiar with was imported from Europe and, although we can harvest homey for our breakfast toast, it is not the most effective pollinator. There are 4400 species of native bees in North America, and most of them are 2-3 times more efficient pollinators than honeybees. They are also more plentiful and not as prone to disease as honeybees.
The Spider Family
There are 3,400 different species of spiders in North America. Only 3 of these are poisonous, and they are all great at catching insects (including wasps). Some spiders spin webs, some don’t – but the commonality among all spiders is that they get rid of insect pests for you. They also serve as a favorite food for many birds and amphibians. Why kill a spider if you don’t have to? If your farm is home to many different spider species, then your insect problems are being taken care of.
The Lady Bugs (Lady Beetles)
Such a nice neighbor. Not only is this insect pretty, but one ladybug larva can eat 25 aphids a day, and the adult ladybug can eat as many as 60 aphids in a day, far more than her body weight.
The adult lacewing has green translucent wings. The lacewing larvae are the real hunters. They can devour up to 200 aphids in their 3-week larval stage. They are called “aphid lions” for a good reason. When you are walking your fields checking for pest insect eggs be sure to know what eggs you’re destroying. Lacewing eggs have a silk–like thread that attaches them to a leaf, and they may be individual eggs or clusters.
The Tachinid Flies
These flies look like a common housefly, only larger. They are parasitic flies and lay their eggs on numerous soft-bodied insect pest larvae. They either lay their eggs on the larva or on a leaf that is being eaten by the pest. When the pest eats the leaf section with the eggs, they hatch inside the pest and eat their way out.
The Praying Mantis
The praying mantis egg sac winters on the stem of a perennial plant or a shrub. When it hatches in the spring there will be up to 300 new baby praying mantids. But they have many predators so only about one/fifth of them will survive. Praying mantis will eat anything, even grasshoppers and crickets, also any beneficial insects or other praying mantis that crosses their path. But they are voracious eaters and will take care of insect problems in no time.
Having insect partners on your farm means you have to maintain or create habitat for them. On a no-till or strip-till farm, you can create buffers of native wildflowers and grasses that give both beneficial insects and birds a home. Although you may lose some farmland to buffers you will gain profitability. Gill et al. conducted a study on beneficial insects and buffer strips. Their conclusion was:
Giving beneficial insects a home on your farm means you have to consider your insecticide protocol. Consider how much you could save in time, farm soil compaction, fuel costs, and soil health if you let insects work for you.
Can Insects Get Out of Control?
Relying on Mother Nature and the natural food web is key. In other words, birds would be the natural insect control system. Insects are all that bluebirds, swallows, woodpeckers, nuthatches, and purple martins eat. And not only birds eat insects, but a single bat can eat 1,000 insects in an evening. If it’s a nursing mother, it can eat as many as 4,000 insects.
According to the USGS: By eating insects, bats save U.S. agriculture billions of dollars per year in pest control. Some studies have estimated that service to be worth over $3.7 billion per year, and possibly as much as $53 billion.(3)
But it’s not only insects that ravage your crops. Raccoons, woodchucks, squirrels (if you have a nut orchard) and deer are all problems. You have tenants that you almost never see who prey on these pests.
The Raptor and the Fox
Mice, voles, and opossums can all destroy field crops. But wherever there is prey there are predators. We’ve all heard the hoot of an owl, but we rarely see one. Many nocturnal predators do a lot of work on a farm. Owls, on average, can eat up to 12 mice in an evening. The fox is also a welcome resident on your farm, although timid and adept at avoiding humans. According to the Woodland Trust in the UK, “foxes have a really diverse diet. They are expert hunters, catching rabbits, rodents, birds, frogs, and earthworms as well as eating carrion. But they aren’t carnivorous – they are actually omnivores as they dine on berries and fruit too.”(4).
Your farm may also be home to hawks and numerous barn cats. As predators, they hang around your farm because there is prey. Put out the welcome mat.
Your farm ecosystem is home to a wide range of tenants, from the microscopic to mammals. Your farm ecosystem also includes you and your family. When you eat from your fields, then compost waste – both from your meal and the crop residue– you create a closed-loop. Spreading that compost full of organic matter on your fields replenishes your soil with energy. As that food is consumed by the microbiology in your soil and cycled to your crops, the cycle of eater and eaten continues.