One of the undeniable facts about soil is…the spaces between soil particles are as important as the particles themselves. This is where the Soil Food Web, the life of the soil, operates. In the gaps between soil particles.
Soil Structure arises from the physical properties—the sizes, shapes, and composition—of the soil particles, and the way the life in the soil arranges them.
Bacteria are omnipresent. They’re the most successful organisms on the planet, with enough diversity to sustain toeholds in even the most extreme conditions, from hyper-acidic mine runoff to ocean thermal vents. Soil—soil is easy, for bacteria, soil is a vacation in the Bahamas.
Bacteria are also sticky. They release glue-like (“colloidal”) substances so they can stick to their food source, and bind soil particles around them to hide from predators, forming microscopic clumps, or micro aggregates. The gaps between are called micro pores. The hyphae of soil fungi then thread their way through and around these micro aggregates, binding them into soil aggregates, or larger, variable clumps, with channels known as macro pores in between. Water, air, and roots pass through these channels.
Macro pores and micro pores work together to regulate water availability for plants. Excess rainfall drains through the macro pores into the subsoil, but the micro pores retain soil water that plants can later draw on.
Why is Soil So Important?
There are many different types of soil. The differences arise from the type of parent material, the weathering and sorting processes that produced it, the types and numbers of organisms that live in the soil, and the plant communities on the surface.
Soil is the basis of agriculture, and agriculture is the basis of civilization. Without agriculture, humans would never have been able to concentrate in towns and cities. Human populations would have remained small and nomadic.
That’s the big picture. Soil also performs some critical ecosystem services:
- it regulates water availability and quality. Permeable soils allow water to penetrate deep into the soil, instead of running off the surface and creating erosion problems. Soils act as filters to remove surface impurities in the process of recharging groundwater.
- Provides habitat for soil organisms that act as Nature’s recycling system. Soils harbor the organisms responsible for converting animal waste—and the bodies of dead animals—into plant-available nutrients that can cycle back through the ecosystem.
But why is soil so important for the gardener?
Let us count the ways. Soil provides:
- physical support for plants. Plant roots penetrate the soil and anchor the plant to support above-ground growth.
- mineral nutrients that support and sustain plant growth.
- water retention and sustained release of moisture to plant roots.
- aeration for plant roots. It’s one of the less obvious facts about soil, but roots—and the life that encrusts them—need to breathe, too.
- protection from toxins—soils ventilate gases, break down organic toxins, and suppress microorganisms that produce toxins.
And why is good soil so important for the Indiana gardener?
Job number one in improving Indiana’s infamous clay soil is to open up the pore structure to fix the drainage issues, so excess water can drain through, and air can penetrate deeper into the soil. The tiny, pancake-shaped particles of clay soils pack tightly, leaving little pore space. Clay soils drain poorly, and the air spaces between particles are often flooded or anoxic. Clay soils don’t breathe.
Most plants need air around their roots, not just water. Without air, roots sicken and die, while plant and soil pathogens thrive. Making annual additions of good garden compost or composted manure is one way of improving clay soil—the slow way. It will take 4-5 years, but it will eventually turn a clay soil into a nice clay loam.
Improving garden soil takes two things: lots of organic matter, and lots of elbow grease (or a tiller).
In clay soils, organic matter improves the pore structure of the soil, increases drainage, and increases soil biodiversity by allowing aerobic processes to take place deeper into the soil horizon. At the extremes—a sandy soil that drains too quickly and a clay soil that doesn’t drain—you have to fix the drainage issues first, or nothing good can happen. But even at the extremes, adding organic matter is still the best way to improve garden soil.
Adding Organic Matter to Your Soil
When improving garden soil with bulk soil amendments like Altum’s Soil Amendment (1 cubic foot bag) or Bower & Branch All-natural Elements Fertilizer, plan on adding a 3-4” layer to the soil surface, and mixing it into the soil before planting. The first year or two after starting a garden, you’ll want to lay down at least a 4” (10cm) layer, and cultivate it in. Many gardeners make the mistake of leaving soil amendments on the surface, instead of mixing them in. If it’s left on the surface, it’s not a soil amendment, it’s a Mulch. Mulches have their own benefits, but for improving garden soil, the particles have to be in contact with soil organisms, so mix them into the soil.
Warning: do not add coarse materials to clay soil without adding garden compost, composted manure, or other organic matter. If you add sand or fine gravel to clay without adding organic matter, you get concrete when it dries out.
For best results, we recommend all-natural soil amendment products we’ve researched and believe in, including Altum’s Soil Amendment or Bower & Branch All-natural Elements Fertilizer. And if you have any questions about how to use soil amendment, how much to use and the best way to incorporate it into your garden beds, stop into the garden center and ask any of our friendly growing experts, email us, call us or you can even live chat with us! Your success is ours.