Soil

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Course 1 · Chapter 2 · Soil: Texture, Structure, pH and Organic Matter

Good soil does most of a gardener's work. It holds water and air, supplies nutrients and gives roots something to grip. This chapter covers what soil is made of, how texture and structure differ, what pH means, why organic matter matters so much, and how to run a few simple tests on your own plot. Chapter 3 then covers how to improve and feed it.

What Soil Is Made Of

Garden soil is a mix of mineral particles (sand, silt and clay), decaying organic matter, water, air and a huge number of living organisms such as worms, fungi and bacteria. The mineral part gives the soil its texture; the way those particles clump together gives it its structure.

Texture: Sand, Silt and Clay

Type	Feel	Drains	Holds nutrients	Warms in spring
Sandy	Gritty, falls apart	Very fast	Poorly	Quickly
Silty	Smooth, soapy	Moderately	Fairly well	Moderately
Clay	Sticky, rolls into a ribbon	Slowly	Well	Slowly
Loam	Crumbly, holds shape lightly	Well	Well	Reasonably

Loam, a balanced mix, is the gardener's ideal, but few plots are perfect. You cannot change texture much in practice; you improve a sandy or clay soil mainly by adding organic matter.

Do not dig wet clay Walking on or digging clay when it is waterlogged squeezes out the air and can leave it hard as brick when it dries. Wait until it crumbles rather than smears.

Structure

Structure is how the particles join into small crumbs with gaps between them. Good structure gives both air and water space, so roots can breathe and drink. Compaction (from foot traffic, heavy machinery or digging when wet) destroys it. Organic matter and the activity of worms build it back up.

Good structure

Crumbly, dark, with visible worms and fine roots. Water soaks in without pooling.

Poor structure

Hard clods, a crust on top, or puddles that linger after rain. Roots stay shallow.

pH: Acid or Alkaline

pH measures acidity on a scale where 7 is neutral, lower numbers are acid and higher are alkaline. Most vegetables grow best in slightly acid to neutral soil, roughly pH 6.0 to 7.0 (check). Outside that range some nutrients become hard for roots to take up.

pH	Description	Typical response
Below 5.5	Strongly acid	Most vegetables struggle; lime is often added (check)
6.0 to 7.0	Slightly acid to neutral	Suits most vegetables
Above 7.5	Alkaline	Some nutrients locked up; brassicas cope better (check)

Test before you treat Do not add lime or sulphur on a guess. A cheap kit from a garden shop will tell you where you stand first. Potatoes, for instance, are often said to prefer slightly acid soil, so liming is not always wanted (check).

Organic Matter

Organic matter is the dark, crumbly material left when plants and animals decay. It is the single most useful thing you can add to almost any soil: it opens up clay, helps sand hold water, feeds soil life and releases nutrients slowly. Sources include garden compost, well-rotted manure and leaf mould, covered in Chapter 3.

A Simple Soil Test

You can learn a lot about your plot without equipment.

# 1. The squeeze test (moist, not wet, soil)
Take a handful, squeeze it, then open your hand.
  falls apart at once      -> sandy
  holds, then crumbles     -> loam
  stays in a sticky lump   -> clay

# 2. The jar test (sand, silt and clay layers)
Fill a jar one third with soil, add water to near the top
and a squirt of washing-up liquid. Shake well, then leave.
  sand settles first (about a minute)
  silt next (a few hours)
  clay last (a day or more)
  measure each layer -> rough percentages

# 3. The drainage test
Dig a hole about 30 cm deep, fill with water, let it drain,
fill again and time the second draining.
  under an hour or so   -> drains freely
  many hours remaining  -> poor drainage

Record what you find Add a short soil entry to your notebook from Chapter 1: texture, rough pH, drainage and any compacted patches. It tells you what to do in Chapter 3. The timings and depth in the tests above are rules of thumb from general practice (check).

Raised Beds and Bought Soil

If the ground is very poor, a raised bed filled with bought topsoil mixed with compost is a reasonable shortcut. Buy from a reputable supplier, since cheap topsoil can contain stones, weed seeds or little goodness. Even in raised beds, soil life and organic matter still need topping up every year.

Not Yet Verified, and Sources

Source. Written from general knowledge of gardening; no specific source was read. Nothing is quoted from a text.
Marked (check). The pH ranges, liming advice, potato preference and the test timings. Verify against local advice or the instructions on a soil test kit.

Exercises

Exercise 1

Do the squeeze test on soil from three places in your plot or from a bag of compost or topsoil. Record what you feel, which texture each is closest to, and what that means for drainage and nutrients.

→ Solution

Exercise 2

Run the jar test on one soil sample and work out rough percentages of sand, silt and clay from the layers. Say which texture you have and which one habit (such as adding organic matter) would help most.

→ Solution

Exercise 3

Write a one-page soil record for your chosen growing spot: texture, structure, drainage result, pH (from a kit, or planned) and what that suggests for your three first crops from Chapter 1.

→ Solution

Quick Reference

Texture: sand, silt, clay, or loam (a balance)
Structure: crumbs with air and water gaps; protect it from compaction
pH: about 6.0 to 7.0 suits most vegetables (check)
Organic matter: improves every soil type
Tests: squeeze, jar, drainage, pH kit
Never: dig or tread on waterlogged soil

Coming next Chapter 3 covers compost heaps, manure, mulch and fertilisers: how to feed the soil and the plants.