Revisión del suelo

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A simple soil monitoring manual for landowners and homeowners. Paul Morris, Planet Healers.

Five tests, one afternoon a year, kitchen and shed tools. That's what this manual asks of you.

You can't see soil heal the way you see a tree grow. So you check it. Once a year, same spots, same season, and you write down what you find. After three or four years you'll know whether what you're doing on your land is working, and you'll have the photos and numbers to show your neighbours.

Every test here works for a homeowner with a backyard or a family with 40 hectares. No lab, no oven, no special meters. If you want to go deeper later, the last section points the way.

One rule above all the others: always compare against a reference spot. A number on its own tells you very little. A number next to the healthiest soil nearby tells you how far you have to go.

Companion guide: once you know what your soil needs, Living Soil in Seven Steps shows you how to build it.

What you need

Most of this is already in your kitchen or shed. Total cost if you buy it all new: the price of a decent lunch.

Before you dig anywhere near a house, road or fence line, check for buried cables and pipes. Most countries have a free locate service; call it.

Pick your spots and your season

You need at least three spots. Mark each one with a stake and save its location.

1. Reference spot. The healthiest soil you can find nearby that has been left alone the longest: an old fencerow, a patch of old forest, a cemetery edge, a neighbour's untouched corner. This is your target.
2. Restoration spot. Where you're doing the work: the new planting, the mulched bed, the pasture you've stopped mowing. Add one spot for each different kind of work you want to compare.
3. Problem spot. The worst ground you have: bare, packed, eroding. Or, if you've already started work, a spot that still looks like your land did before you began. This is your baseline.

Give each spot a short name you'll still understand in five years: "REF fencerow", "Swale 2", "Old parking".

On a bigger property, put two or three spots in each area instead of one. Soil changes a lot over a few metres, and more spots smooth that out.

When to test

Pick one window and stick to it every year. Soil shifts with the seasons, and testing in the same window keeps the weather from muddying the change you made.

• Seasonal tropics (a wet and a dry season): near the end of the rains, when the soil is moist but you can still walk on it.
• Temperate places: late spring, after the soil has warmed and before summer dries it out.
• Everywhere: wait two or three days after a good rain, so the soil is moist but not soaked. Write down how many days it's been since the last rain.

Test every year for at least five years. Year one is your starting line. Don't expect much change by year two; by year four or five, you'll see it.

Test 1: photo point and ground cover

Bare soil is the single clearest sign of trouble you can measure without digging. Rain hits it, seals it, and carries it away. This test takes 10 minutes and tells you how much of your ground is covered.

Photo point

1. Stand at your stake, facing the same direction every year. North is easiest to repeat. Write it down.
2. Hold the phone at chest height and take one wide photo of the area.
3. Take a second photo straight down at your feet, about 1 m of ground in frame.
4. Next year, stand on the same spot, face the same way, take the same two photos.

The pair of photos side by side, year after year, is often what convinces people. Don't skip it.

Ground cover count (step-point)

1. Walk a straight line through the area, starting at the stake.
2. Every step, look at the soil right at the tip of your boot. Ignore everything else.
3. Record one of four things: bare (soil you could pick up), rock, litter (dead leaves, mulch, sticks touching the ground) or plant (a living plant rooted there).
4. Take 100 steps. If your yard is small, walk back and forth until you reach 100.

Your counts are your percentages. 23 bare out of 100 steps is 23% bare.

What you want to see: bare going down every year, litter and plant going up. Your reference spot sets the target. In drylands some bare ground between plants is natural, so match your reference rather than chasing zero. Rock doesn't change; it's there so you don't count it as bare.

Test 2: spade test (look, smell, feel, count)

One block of soil tells you more than most lab reports, if you know how to read it. This test takes about 15 minutes per spot. Do your reference spot first so you know what good looks like on your land.

1. Dig about 1 m from your stake. Next year, dig on a different side so you never dig the same hole twice.
2. Cut a block about 20 cm wide and 20 cm deep. Lift it out whole and set it on a sack or tarp.
3. Look. Compare its colour to your reference block. Same darkness: score 2. A bit paler: 1. Much paler or grey: 0. Darker soil usually means more organic matter.
4. Smell. Sweet and earthy, like a forest after rain: good. Sour, or rotten eggs: the soil is short of air, often from waterlogging or packing. Write good or sour.
5. Feel. Break the block apart with your hands, gently. Mostly rounded crumbs, pea-sized and smaller: score 2. A mix of crumbs and hard clods: 1. Mostly hard, sharp-edged clods, or one solid lump: 0.
6. Roots. Look at the wall of the hole. How deep do roots go, in cm? Do they grow straight down, or turn sideways at a certain depth? Roots that bend flat usually hit a packed layer. Note the depth.
7. Count life. For 2 minutes, count every creature you see in the block: earthworms, beetles, larvae, centipedes, ants, spiders. Write the number of earthworms separately.
8. Topsoil depth. On the wall of the hole, measure from the surface down to where the dark layer turns lighter, in cm. If you hit rock first, write "rock at" and the depth.
9. Put the block back and fill the hole.

In dry country or in the dry season, earthworms go deep or go dormant. Zero earthworms in a dry month doesn't mean dead soil. Count everything that moves, and compare against your reference spot in the same week.

Test 3: slake test

This is the test people remember. Healthy soil is held together by roots, fungal threads and the sticky stuff soil life makes, so it holds its shape in water. Tired soil falls apart and turns the water to mud. That's exactly what happens to your bare ground in a heavy rain.

1. From each spot, pick up two or three clods about the size of a walnut from the top 5 cm. Keep each spot's clods in a labelled bag.
2. Let them dry out completely indoors for a day or two. Wet clods won't give a fair result.
3. Fill a clear jar with water. Hang the strainer or mesh in the top so the clod will sit just under the surface.
4. Lower one clod gently onto the mesh. Start the timer.
5. Watch for 5 minutes, then score it.

Run the reference clod and your problem-spot clod side by side in two jars. Film it on your phone. It makes the case for soil cover better than anything you could say.

Very sandy soils fall apart in water whatever you do. If your soil is mostly sand, the slake test tells you less; lean on the infiltration and spade tests instead.

Test 4: infiltration ring

How fast does rain get into your soil? Water that soaks in feeds plants for weeks. Water that runs off takes your topsoil with it. This test pours 2.5 cm of rain into a ring and times how long the soil takes to swallow it. Allow 20 to 40 minutes per spot.

1. Clip the plants inside a circle a bit bigger than your can, down to the soil. Leave the roots and litter alone.
2. Set the can on the ground, lay the board across it and tap it in with the hammer until about 7 cm is underground. Press soil against the outside of the rim so water can't leak out sideways.
3. Line the inside of the can with a plastic bag, pressed down onto the soil. This stops the water from scouring the surface when you pour.
4. Pour in the right amount of water (table below), then gently pull the bag out and start the timer.
5. Stop the timer when the surface just stops shining and no water is pooling. Write down the minutes.
6. Do it again straight away with the same amount of water. Write that time down too. The second time is the one to compare year to year, because the soil is now wet like it would be in a long rain.
7. If the water still hasn't gone after 60 minutes, stop and write ">60".

Any other size: water in mL = 1.96 × diameter × diameter (in cm).

To turn your time into a rainfall rate: rate in cm per hour = 150 ÷ minutes.

So 10 minutes means the soil takes in 15 cm of rain an hour. 50 minutes means 3 cm an hour. Compare each spot against your reference, and against itself last year. Faster is better.

Test 5: buried cotton test

Cotton is plant fibre. Living soil eats it. Bury a piece, dig it up two months later, and how much is gone tells you how busy your soil life is. Farmers in Canada and Switzerland have run this as a public campaign under the name "soil your undies", and yes, old cotton underwear works fine.

1. Cut pieces of plain white 100% cotton, about 15 × 20 cm, all from the same garment or roll. Keep a few spare pieces in a drawer for next year so the cloth is always the same.
2. Photograph each piece before burying it, next to a ruler.
3. Bury one piece at each spot, laid flat, about 10 cm deep. Leave a corner sticking up or tie on a string so you can find it.
4. Mark it with a stake. Write down the date.
5. Dig it up after 60 days. Lift it out with your hands, gently. Don't pull.
6. Rinse it lightly and lay it flat on a dark surface next to an unburied piece. Photograph both.
7. Estimate how much of the cloth is gone: under 25%, 25 to 50%, 50 to 75%, or over 75%.

Timing matters. Soil life slows right down in dry or cold soil. Bury the cloth 60 days before your yearly test day, so it spends those two months in the season when soil is alive and working, and you dig it up on test day.

If you have a kitchen scale that weighs to 0.01 g, the Tea Bag Index is a more exact version of the same idea. The method and current tea brand advice are at teatime4science.org.

Shallow, rocky and karst soils

Most soil manuals assume you can dig 50 cm. On limestone, volcanic rock, or old stripped hillsides, you often hit rock at 10. These tests still work with a few changes.

• Pick your spots in soil pockets. Choose places where you can get a spade in. Record roughly what share of the area is open rock, so a future reader knows the pocket isn't the whole picture.
• Topsoil depth becomes depth to rock. Write "rock at 12 cm". On thin soils this is the number that moves as litter breaks down into new soil, so it's worth tracking.
• Add a litter layer measurement. Push a ruler down through the dead leaves at your stake until it touches mineral soil or rock. Record the depth in cm. Where soil is forming on rock, a thickening litter layer is the first sign of progress.
• Smaller block, same size every year. If you can only lift a block 10 cm deep, use 10 cm every year.
• Infiltration ring: drive the can in as far as it will go, at least 3 cm, and pack wet soil hard around the outside so water can't escape under the rim. Write down the depth. If you can't get 3 cm, skip this test at that spot.

Ask the farmers who've worked your area longest what they call the soils. In Yucatán, Maya farmers have long named soils by colour, depth and stones, such as tzekel for the shallow, stony ground and k'ankab for red, deeper soil. Those names often draw finer lines than a soil map does. Use them in your spot names and notes.

Reading your results

Most soil problems have the same few causes, and the same few fixes: keep the ground covered, keep living roots in it, feed it from the top, and stop packing it down. Your results tell you which of those to push hardest. The how-to for each fix is in Living Soil in Seven Steps, and the last column points you to the step.

Change is slow, then visible. Year two often looks like year one. By year four, the slake jar, the infiltration time and the photos usually tell the story on their own.

If a spot gets worse, that's useful too. It means something you're doing, or something happening next door, needs a second look. Write down anything unusual each year: a fire, a flood, new goats, a drought, a neighbour's spraying.

Going further

The five tests above are enough to see whether your soil is getting better. If you want more, these are the ones worth the extra effort.

Species counts belong beside soil checks. Log what you see at each spot in TEND or iNaturalist through the year. More life above ground and more life below usually move together.

Record sheet

One column per spot. Print it, or log the same fields in TEND's Soil check.

Date: ________ Days since last good rain: ____ Weather today: ____________ Who tested: ____________