1. Does the soil have good structure and tilth?
Do this test when the soil is neither too wet or too dry. When you make these assessments, be sure to note how much time has passed since the last tillage operation. Dig a hole 6 to 10 inches deep. Separate an intact section about the size of a soup can and break it apart with your fingers. Determine whether the soil is cloddy, powdery, or granular. Ideally, your soil should be made up of differently sized crumbs that will hold their shape under slight pressure. Crumbs, or aggregates, as soil scientists call them, that break apart only with difficulty mean your soil is too hard.
Why are soil structure and tilth important?
Soils with ample pore space and an even distribution of large and small pores are well aerated, have a good water-holding capacity and infiltration rates, and are easy for roots to grow through. Stable crumb aggregates preserve pore space in soils by preventing the clogging of pores with loose particles.
2. Is the soil free of compacted layers?
Plunge a wire flag vertically into the soil at different locations. Mark the depth at which the wire bends. The sooner it bends, the more compacted the soil. A foot or more of easily penetrable soil is ideal.
Why is compaction important?
Compacted soil inhibits root growth and water availability, and keeps earthworms and other vital soil fauna from circulating freely.
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3. Is the soil worked easily?
You may have already learned about your soil’s workability the last time you got the garden ready for planting. If tilling or digging the soil produces cloddy or platelike clumps, the workability is low. Farmers measure workability by monitoring how much tractor fuel they use; you can simply judge the effort necessary to prepare beds for planting.
Why is workability important?
How easily a seedbed is prepared can indicate whether a soil is workable and therefore in good condition. Good workability means that water infiltration and soil structure are in a desirable state.
4. Is the soil full of living organisms?
Measure the animal life in your soil by digging down at least 6 inches and peering intently into the hole for 4 minutes. Tick off the number and species of each organism observed, such as centipedes, ground beetles, and spiders. Because most soil organisms spurn daylight, gently probe the soil to unearth the more shy residents. If you count less than 10, your soil does not have enough active players in the food chain.
Why are soil organisms important?
A thriving population of diverse fungi, bacteria, insects, and invertebrates is one of the most visible signs of soil quality. The more that creeps and crawls under your garden, the less opportunity there is for pests and disease. Each level of soil life does its part to break down plant residue and make more nutrients available for plant growth.
5. Are earthworms abundant in the soil?
When the soil is not too dry or wet, examine the soil surface for earthworm casts and/or burrows. Then dig out 6 inches of soil and count the number of earthworms squirming on the shovel. Three worms are good; five are better. The absence of worms means the soil does not have enough of the organic matter they feed on. An exception: If you live in the South-west, don’t waste your time looking, even if the soil displays other conditions of soil quality. “Earthworm activity is less likely in the desert,” says the University of Arizona’s Walworth. “Worms don’t like hot soil.”
Why are earthworms important?
Not only do earthworms aerate the soil, but their casts infuse the soil with enzymes, bacteria, organic matter, and plant nutrients. They also increase water infiltration and secrete compounds that bind soil particles together for better tilth.
Read more on Benefits of Earthworm to your Soil
6. Is plant residue present and decomposing?
If you’ve grown a cover crop, dig down 6 inches 1 month after turning it into the soil and then look for plant matter. The range of organic material is important to notice here. The presence of recognisable plant parts, as well as plant fibres and darkly coloured humus, indicates an ideal rate of decomposition.
Why is residue decomposition important?
Residue decomposition must take place for the soil to maintain its organic matter content. Organic matter is important to soil quality because it increases the soil’s ability to supply essential plant nutrients. Soil organic matter helps maintain good soil structure. The activities of soil organisms create air and water passageways that improve soil structure. Rapid organic residue decomposition shows that a thriving biological community lives in the soil. When the organic residue is present, it increases infiltration and water storage. In this way, the potential for erosion by water runoff is reduced.
7. Do crops/weeds appear healthy and vigorous?
Start this test during the active growing season and look for healthy plant colour and size that’s relatively uniform. Overall health and development must be judged for what’s considered normal for your region. One caveat: If you planted late or during a drought, or suffered a pest infestation, results of this test may be unreliable.
Why is plant vigour important?
Plant vigour indicates soil with good structure and tilth, a well-regulated water supply, and a diverse population of organisms. It’s the best sign of effective soil management you’ll have above ground.
8. Do plant roots grow well?
Use a shovel or hand trowel to dig gently around a selected plant, preferably a weed you won’t miss. Once you’ve reached root depth, pull an annual plant up and check the extent of root development, searching for fine strands with a white healthy appearance. Brown, mushy roots indicate serious drainage problems and a poor outlook for this year’s harvest. Stunted roots might also indicate disease or the presence of root-gnawing pests.
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Why is root growth important?
Roots have the most immediate connection with and reliance on soil quality. Without air, water, biological activity, and crumbly soil to grow in, roots can’t do their job.
9. Does water infiltrate quickly?
Take an empty coffee can with the bottom removed and push it into the soil until just 3 inches remain above the surface. Fill the can with water, marking the water height, and then time how long it takes for the water to be absorbed into the soil. Repeat this several times until the rate of absorption slows and your times become consistent. Anything slower than 1/2 to 1 inch per hour is an indication of compacted soil.
Why is water infiltration important?
Good infiltration gets water to plants where they need it, at their roots, prevents runoff and erosion, and lets air move more efficiently into soil pores.
10. Is water available for plant growth?
Wait for a soaking rain; then record how long until plants start to show signs of thirst. Results will vary widely by region. The basic lesson is that if plants require more frequent watering than typical for your region, your soil is probably the culprit.
Why is water availability important?
Soil structure and organic matter are soil quality factors that determine the ability of soil to retain water between rains or irrigations. Good water availability in soil is another sign that soil structure and organic matter are in a desirable state.
This post is based on the Willamette Valley Soil Quality Card Guide.
Reference: 10 easy soil tests (www.rodalesorganiclife.com)