The Monterey Garden Club

ABOUT SOIL

MOIST AND WELL-DRAINED SOIL

Exactly what does that mean?

Good drainage is essential for most plants, which don’t grow well in soggy soil. Although water and the nutrients dissolved in it are necessary for roots, oxygen is also essential. Waterlogged soils don’t allow roots to receive enough oxygen. On the other hand, soils that drain too quickly (ie sandy soils) don’t allow roots time to absorb enough water and nutrients to fuel plant growth.

So - the ideal soil is one that holds moisture long enough that roots can absorb

what they need, but not so long that they suffocate from lack of air.

This is what is meant by moist but well-drained soil.

Garden soils are composed of 4 kinds of particles:

• sand
• silt
• clay 
•  humus

The best garden loams are crumbly and finely textured, and are made up of:

• 10% humus - Humus is a collection of particles of decayed plant matter - & acts as a food to beneficial microorganisms --Humus improves drainage by increasing soil porosity AND Humus returns nitrogen, potassium, phosphorous and trace elements to soil
• 20-30% clay - Clay promotes water retention, & helps roots absorb water and trace elements from soil  AND Clay particles pack tightly together, making soil dense and heavy - drain slowly and may become waterlogged and compacted adding organic matter (humus) to clay soils lightens their texture and improves their drainage
• 60-70% sand and silt - Sand promotes drainage and the incorporation of air into the soil AND Silt particles are smaller than sand particles but larger than clay particles

To put it simply: fertility is determined by

the amount of organic matter and nutrients a soil contains.

Rich soils are high in both organic matter and nutrients -

• nitrogen
•  phosphorus
•  potassium -
•  and contain trace elements (such as iron and boron.)

Fertile soils team with microscopic and insect life and worms, contain an abundance of humus (which serves as a source of food for them) and have a texture that supports both incorporation of air and retention of enough water to help plants take in nourishment.

Soils of average fertility are fine for most plants. (Soils of less-than-average fertility are even preferred by some types of plants: for example, the flavor of some herbs is intensified when grown in poor soil, because poor soil causes the leaves to produce more of the volatile oils that give them their taste and scent.)

Most plants are tolerant of a range of pH. Many thrive in a slightly acid to neutral range of 6.0-7.0.  Your soil test kit will tell you what the pH is in your soils.

• pH of 7.0 is considered neutral
• pH below 7.0 indicate acid soils
• pH above 7.0 indicate alkaline soils

The pH affects the availability of nutrients and trace elements to plant roots.

When soil pH is too strongly acidic or alkaline, the trace elements and nutrients assume forms that are not soluble in water.

Changes in pH also affect the viability and activity of soil microorganisms.

It is foolish to try to adjust the pH to any great extent -

but some changes to adjust pH can be made:

• To raise the pH of a too-acid soil, add lime.

(Alkaline soils are usually found only in arid and semiarid regions of the U.S.)

• Composted oak leaves, peat moss, epsom salts and sulphur can all used to lower pH)

(Organic soil amendments can adjust pH, build better soil structure, and add nutrients)

• Ground limestone, added to heavy clay soil, improves soil texture by

                 causing the tiny particles to clump together, thus lightening the dense texture.

                 It is also used to raise ph of the acid soils.

• Dolomitic lime: especially good because it contains magnesium - which plants need and many soils lack.
• Peat Moss: partially decomposed plant remains - good source of organic matter

           & enhances the ability of light soils to hold water. Generally acidic: good soil

          amendment for acid-loving plants such as azaleas.  Absorbs many times its weight

          in water. When it dries out, can form a hard crust and act as a wick, drawing moisture

          from the soil - so do NOT use peat moss as a mulch.

• Compost: decayed remains of many different life-forms. Its nutrient value depends on what went into it - but any properly made compost is excellent for improving soil structure and adding organic matter.     Make your compost with garden refuse, food scraps, soil, and some animal products such as eggshells and manure. (NOT meat scraps)
• Animal manures - add organic matter, nitrogen, phosphorus and potassium, as well as trace elements. Composted manures are best: fresh manure, especially chicken, can burn plant roots. Horse and cow manures are generally considered to be the best. Pet manures (dog, cats) should not be used.
• Bonemeal - made from steamed, ground animal bones - excellent source of phosphorus, and adds some nitrogen.
• Rock phosphate - powdered rock that supplies phosphorous slowly over an extended period of time. Till it into the soil with compost or manure.
• Greensand - a mineral compound of iron, potassium and silica deposited eons ago in ancient seabeds. Good source of potassium, and some trace elements.
• Granite dust - by-product of the building industry - potassium released slowly - best tilled into soil like rock phosphate.
• Wood ashes - supply potassium and smaller amounts of phosphate: determined by the type of wood. The nutrients are very soluble - but the ashes raise the soil pH - should be used with care.

Generally defined as full sun, partial shade or shade.

• FULL SUN - means that the plants receive at least 6 hours of direct, unobstructed sun each day.
• PARTIAL SHADE - sun will give plants 2-6 hours of sun, with light shade the rest of the day.
• DEEP SHADE - plants receive no direct sunlight at all; few plants can grow in such conditions.

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