The soil is the home of many arthropods. Their jointed (arthros) legs (podos) are how they got their name. Arthropods are invertebrate animals, meaning they lack a backbone and rely on an exoskeleton for protection. Arthropods come in various sizes, from tiny to several inches long. Among them are arachnids like spiders and mites, insects like springtails, beetles, and ants, crustaceans like sowbugs, myriapods like centipedes and millipedes, and scorpions. There are numerous diverse arthropod species found in almost every soil. Several dozen species of arthropods exist in a square mile of soil used for row crops. A square mile of forest soil may support thousands of different species.
How do arthropods help us?
Although some arthropods that feed on plants can become pests, most of them contribute to the health of the soil and plants. Arthropods help us in the following ways:
Grind up the biological matter. Arthropods dig through coarse woody waste and shred plant leftovers, increasing the surface area vulnerable to microbial attack. A bacterium in leaf litter without a shredder would be like a human with a can but without a can opener; eating would be very difficult for them. Shredders significantly speed up the decomposition of waste matter. They go through decomposing plant matter in order to consume the bacteria and fungi that are present on their surface.
Stimulate the activity of microbes. Arthropods feed on bacteria and fungi, which encourages the growth of other fungi, such as mycorrhizae, and the breakdown of organic materials. The opposite outcome, a drop in bacterial and fungal populations, can happen if grazer populations become too dense. Predatory arthropods are crucial to regulate grazer populations and stopping them from overgrazing microorganisms.
Assist in the availability of nutrients to microbes. Soil bacteria can only go so far, and a rival is probably nearer to a valuable nutrient. Arthropods assist in the availability of nutrients to microbes by transporting germs on their exoskeletons and digestive tracts. Arthropods accelerate the breakdown of organic substances by mixing bacteria with their food.
Make mineral nutrients available to plants. Arthropods feed on minerals found in bacteria and fungi and excrete them in ways that plants can use.
Improve soil aggregation. Every soil particle in the top few inches of grassland and forest soil has passed through the digestive tract of countless soil flora. The soil is extensively mixed with organic matter and mucous each time an arthropod or earthworm eats it and then deposits it as fecal pellets. Fecal pellets are a source of highly concentrated nutrients that contain both organic and inorganic elements necessary for the growth of bacteria and fungi. Arthropod fecal pellets range from 1/10,000 to 1/10 of an inch (0.0025mm to 2.5mm) in size.
Burrow in the soil. Only a small number of arthropod species tunnel into the ground. However, in any soil community, burrowing arthropods and earthworms significantly impact how the overall fauna is composed through modifying habitat. Porosity, water infiltration rate, and bulk density are among the physical characteristics of soil that are altered by burrowing.
Encourage the succession of species. A bewildering assortment of natural bio-organic substances permeates the earth. Various bacteria, fungi, and other creatures with different enzymes must completely digest these substances. Only a limited portion of species—those able to utilize the resources at hand—are metabolically active at any given time. By consuming the dominating organisms and allowing weaker species to move in and take their place, soil arthropods promote the gradual decomposition of soil organic matter.
Eliminate pests. While some arthropods have the potential to function as pests, many other arthropods, which are found in all soils, compete with various root- and foliage-feeders. Some arthropods (the specialists) solely consume one particular variety of prey. Other arthropods (the generalists) consume a wide variety of prey, such as numerous kinds of centipedes, spiders, ground beetles, rove beetles, and mites. Generalist predators can control a range of pest outbreaks.
A population of predators is kept in check between pest outbreaks only if there is an ongoing supply of non-pest food for t to consume. This means that a balanced and diverse food web is necessary. Unfortunately, intensive land use, including monoculture, tillage, and pesticides, diminishes soil diversity. Predator populations plummet, and the likelihood of subsequent pest outbreaks rises as overall soil diversity falls.
What are the types of arthropods?
Arthropods can be classified as shredders, predators, herbivores, and fungus feeders based on their roles in soil. The majority of soil-dwelling arthropods consume worms, other insects, or fungi. Less common are root feeders and dead-plant shredders. Arthropods mix the soil and aerate it as they eat, control the number of other soil creatures in the area, and shred organic matter.
Shredders include many large arthropods frequently seen on the soil’s surface. Shredders consume bacteria and fungi on the surface of dead plant material as they chew it up. Millipedes, sowbugs, termites, certain mites, and roaches are the most common shredders. If insufficient dead plant matter is present, shredders can develop into agricultural pests by feeding on live roots.
Diplopods is another name for millipedes, which have two pairs of legs on each body segment. Although most millipedes are harmless to humans, they defend themselves from predators by emitting an unpleasant stink from their skunk glands.
Sowbugs are related to crabs and lobsters. They use their powerful mouthparts to tear apart leaf litter and plant debris.
Predators and micro predators can be specialists who exclusively pursue one type of prey or generalists who feed on various prey types. The predators are centipedes, spiders, ground beetles, scorpions, skunk spiders, pseudoscorpions, ants, and certain mites. Many predators, including parasitic wasps and beetles, have been bred for use as commercial bio-controls. These predators consume agricultural pests.
Walckenaera acuminata, a spider
This tiny, 1/8-inch-long spider hunts other soil arthropods at the soil’s surface. The top of the spider’s head projecting above it is where its eyes are located.
The wolf-spider is a lone hunter who roams the area. Until the young wolf-spiders are ready to hunt on their own, the mother leads them to the water and feeds them by regurgitating.
The pseudoscorpion resembles a young scorpion but without a tail. It creates silk from its mouth and venom from glands in its claws. It is found in croplands’ soil and leaf litter, grasslands, woods, and deserts. Some of them hitchhike beneath beetle wings.
Centipedes are long and thin and feed on earthworms and other creatures with soft skin as they move through soil crevices. Longer-legged centipede species are common in leaf litter and around houses.
Predatory mites feed on nematodes, springtails, other mites, and insect larvae. Its length is 1 millimeter or 1/25 of an inch.
The tiger beetle has strong mouthparts, making it a quick and lethal ground-surface predator. In agriculture, a wide variety of these beetle species are present.
Rugose harvesting ants
Rugose harvester ants are scavengers and not predators. In grasslands and deserts, where they burrow 10 feet under the ground, they consume dead insects and gather seeds. They have a sting that is a hundred times more potent than a fire ant.
Numerous root-feeding insects spend a significant portion of their lives under the soil, including cicadas, mole crickets, and anthomyiid flies (root maggots). Some herbivores, such as rootworms and symphylans, can become agricultural pests when they are present in great numbers and feed on the roots or other portions of plants.
The symphylan, a relative of the centipede, feeds on plant roots and, if other creatures do not restrain its population, can become a significant crop pest.
Most springtails, certain mites, and silverfish are arthropods that feed on fungus (and, to some extent, bacteria). They remove fungus and bacteria from root surfaces and eat them. Microbial grazing and nutrient release by these creatures account for a significant portion of the nutrients made accessible to plants.
Springtail, which is blind and pale in color, feeds on fungi and lives deep within the top layer of natural and agricultural soils worldwide.
Oribatid turtle mite
Of the micro-arthropods, oribatid turtle mites are among the most numerous. This millimeter-long species feeds on fungus.
Read more: Beneficial Animals on the Farm
Where do arthropods live?
Larger species typically forage on the soil’s surface and temporarily hide under foliage, plant debris, wood, or rocks. Many of these arthropods commute daily to forage inside herbaceous vegetation above or even high in the canopy of trees. The deeper soil strata are home to several creatures that can burrow.
With increasing soil depth, soil fauna’s variety and abundance drastically decline. The top three inches of soil are home to the vast majority of soil species. Most of these creatures have a limited range of motion. They are probably capable of “cryptobiosis,” a type of “suspended animation” that allows them to withstand conditions where other animals would perish due to temperature, moisture, or dryness fluctuations.
Below two inches of soil, fauna typically grows to a size of 1/250 to 1/10 of an inch. The majority of these species are colorless and blind. They can squeeze through tiny pore openings and along root channels. These subsurface soil dwellers are primarily concentrated in the rhizosphere (the soil immediately adjacent to roots).
Who lives in your soil?
You may quickly create a pitfall trap to capture large arthropods and a Berlese funnel to catch little arthropods if you want to learn more about the types of organisms that live in your soil.
To create a pitfall trap, put a pint- or quart-sized container (such as a yogurt cup) in the ground so that its rim is level with the soil surface. Create a canopy over the cup if desired to keep the weather out. To preserve the creatures and stop them from eating one another, pour 1/2 inch of non-hazardous antifreeze into the cup. Soil organisms should fall into the trap. Wait a week before taking the cup out of the ground.
To create a Berlese funnel, set a piece of 1/4-inch strong wire screen in the bottom of a funnel to support the soil. (Use a plastic soda bottle’s bottom to create a funnel.) Half-fill the funnel with soil and suspend it over a cup. As a preservative, add a small amount of antifreeze or ethyl alcohol to the bottom of the cup.
To force the organisms out of the soil and into the cup, hang a light bulb about 4 inches above the soil. To dry out the soil, leave the light bulb on for around three days. Then, add the alcohol to a small dish and inspect the organisms using a magnifying glass.
How abundant are arthropods?
The number of individual arthropods in a square yard of soil will range from 500 to 200,000, depending on the kind of soil, the plant community, and the management technique. Although ants and termites prevail in some circumstances, particularly in desert and tropical soils, springtails and mites are typically the most common soil dwellers.
In natural plant communities, those with few earthworms (such as conifer forests) have the highest concentration of arthropods. Natural communities with numerous earthworms (such as grassland soils) have the fewest arthropods. Earthworms outcompete arthropods, either by drastically altering their environment or consuming them.
Contrary to natural plant communities, arthropod numbers and variety increase as earthworm populations grow in pastures and farmlands. In agricultural soils, earthworms that burrow likely provide habitat space for arthropods.
Springtails are the most prevalent arthropod species in many agricultural and rangeland soils. There are frequently tens of thousands of them living in each square yard. It has been demonstrated that springtails are helpful to crop plants because they release nutrients and eat fungi that cause illnesses. Like most insects, springtails walk with three pairs of legs. The Springtails keep their tail snugly tucked under the belly while foraging. When a predator assaults a springtail, bodily fluid rushes into the base of the tail, causing the tail to slam down and launching the springtail up to a yard away– hence the name springtail.
Now we know diverse arthropod species play a crucial role on farms. Comprehensive information about arthropods and their effects on agriculture can contribute to crop productivity. In this article, we have tried to provide you with practical information regarding different species of arthropods and their significant effects on the soil.