Soils & Growing Media

Level II Agricultural Business OperationsHorticulture

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Soil Science

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Soil is made up of 3 main mineral components

1. Sand2. Silt3. Clay

Proportion of each determines soil type 12 different soil types/textures

Soil Science

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Sand is gritty and breaks up if rolled into a ball

Silt is smooth, silky or floury

Clay is sticky when wet, shiny when smeared and holds shape

Soil Science

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Soil Science

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Soil is a valuable source often overlooked.

Amount of nutrients depends on soil type, rainfall, previous management and previous crop ◦ GAP – Good Agricultural Practice

How do you find out what’s in soil? Soil sampling Soil analysis

Soil Science

Sample every 4-5 years for permanent crops Vegetable crops every 2-3 years Yearly in glasshouse

Always sample a new or just rented field

Ideally October – February◦ after previous crop has been harvested◦ NOT following lime or fertiliser application

Starting Point - Sample soils

Walk a “W” or “S” pattern through field

25 cores per sample (avoiding greenery)

Send to laboratory for analysis

Starting Point - Sample soils

Useful equipment◦ Soil auger (can also use a spade)◦ Bucket ◦ Sealable plastic bag◦ Permanent pen

Depth for collection depends on root zone◦ Apples – 6” auger, collect under tree canopy◦ Vegetables

90cm (36”) from Jan – Spring for Soil Nutrient Supply 60cm (24”) in autumn 30cm (12”) for shallow rooted veg

Starting Point - Sample soils

Major nutrients in soil

Nitrogen (N) – most important for plant growth

Phosphorus (P) Potassium (K) – often

referred to as Potash

◦ Others important are Sulphur (S), Magnesium (Mg) and Calcium (Ca)

What are you looking for?

N P K

Soil texture

May affect ◦ Soil structure◦ Water availability

and retention◦ Cultivation methods◦ Nutrient retention◦ Cropping potential

Organic Matter

Separate element to soil test◦ Must be requested◦ Can affect how/what

nutrients are availalbe

◦ Can affect plant protection products

What are you looking for?

Understanding a soil analysis

Understanding a soil analysis

Understanding a soil analysis

1. pH

2. Lime requirement

3. Phosphorus index

4. Potassium index

5. Magnesium index

Soil Analysis

Understanding a soil analysis

A measure of soil acidity or alkalinity pH scale from 0 – 14

pH 7.0 is neutral Less than pH 7.0 is acidic Greater than pH 7.0 is alkaline

Soil pH

ACIDIC NEUT-RAL

ALKALINE

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Soil pH Typical soil pH in Horticulture ranges from:

Acidic Neutral Alkaline

5 6 7 8

Most VegetablesMost Cut Flowers6.5

Brassica Vegetables7.5

Strawberries in soil5.8

Apples 6.0-6.5

Soil pH determines nutrient availability for the plant!

Soil pH

Lime

Understanding a soil analysis

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Liming increases fertiliser performance - % available to plant

Soil Acidity N P K

pH 5.0 (Very Strong acidic) 53% 34% 52%

pH 5.5 (Strongly acidic) 77% 48% 77%

pH 6.0 (medium acidic) 89% 52% 100%

Liming increases the availability of soil nutrients.

Your fertiliser is more efficient if soil pH is at optimum level.

Conditions the soil Improves the availability of major nutrients

Nitrogen, Phosphorus, Potassium, Sulphur, Calcium & Magnesium

Encourages micro-organisms in soil Break down organic matter releasing N

Can help suppress some diseases (Club root)

What does lime do?

Increases earthworm activity Improves texture

Improves soil structure

What does lime do?

Assume Field 9 is 3 acres (area).How many tonnes/acre of lime is required in field 9?

Field area x lime requirement/acre

3 acres x 5.00 ton/acre =

Assume Field 9 is 3 acres.How many tonnes/acre of lime is required in field 9?

Field area x lime requirement/acre

3 acres x 5.00 ton/acre = 15 ton/acre

Granulated lime

Pink lime

Potassic lime

Company specific products

Types of lime used in Horticulture

Understanding a soil analysis

Index 0 – 5 or 6◦ 0 – 2 = soil needs larger quantities of nutrient◦ 3 = generally good index, though some nutrients

may be needed◦ 4 and above = generally do not require additional

feeding Phosphate – form of phosphorus that is

taken up by the plant (P2O5) Aids photosynthesis Good for blooming and root growth

Phosphorus (P)

Understanding a soil analysis

Index 0 – 5 or 6◦ 0 – 2 = soil needs larger quantities of nutrient◦ 3 = generally good index, though some nutrients

may be needed◦ 4 and above = little to no additional feeding

Potash – form of potassium that is taken up by the plant (K2O)

Aids photosynthesis Improves fruit quality

Potassium (K)

Valuable source of nutrients Sample every 2-4 years Use analysis to determine the

amount of nutrients in the soil The higher the soil nutrient reserves

(Index), the lower the need for additional nutrients

Soils - Review

Growing media

The substance in which plants grow Soil Composts Soil-less or loam-less composts

Consider container culture: Growing media must provide

Physical characteristics Balance between water and air Biological factors Chemical factors

What is growing media?

Stability Provide anchorage so that plant can root and be held

securely in the container

Structure and texture Enough air spaces between particles so that water

and air can be held in the medium but also move through medium.

Water level for consistent growth

Physical traits of growing media

Air filled porosity: the number and size of pores (spaces) held between the particles of growing media.

Air filled porosity controls Water drainage through the growing media Availability of water to the plant(s)

Balance of air and water

Biological organisms (aka microbes) are present in growing media – even sterilised media

Promote helpful microbes through feeding Deter harmful microbes by controlling moisture

Chemical properties are the nutrients in growing media

Know the nutrients available Supplement with fertiliser if needed

Fertiliser requirements will vary for plant type and growing medium

Biological and Chemical properties

Organic growing media – derived from plants◦ Peat◦ Wood-based◦ Coir (coconut fibre)◦ Green waste compost

Types of growing media

Inorganic growing media – derived from minerals

Perlite Vermiculite Sand Grit Rockwool

Types of growing media

Traditionally used as the main growing media for container grown crops.

Excellent water holding capacity pH

Acidic Low nutrient value, so fertilisers are usually

added

Reduced use of peat will affect horticulture in future

Peat

http://www.bordnamonahorticulture.ie/professional/visit-bog

How peat is harvested

Mainly used in a mixture with peat to reduce the amount of peat

Composted bark, woodfibre, wood/paper waste or sawdust

Improves drainage

Low pH

Wood-based media

Derived from the outer husk of coconuts

Used on its own in soft fruit production (in bags or containers) and in propagation

Uniform particle size giving good water-holding capacity

Does not hold nutrients well – supplementary liquid feeding required.

Coir

Many local authorities and some private companies produce green waste compost

High (but variable) nutrient content

High pH

Usually mixed with other growing media or used to add organic matter to soil

Green waste compost

Most often used as additives to other organic growing media

Some can be used on their own in specific cultural situations

Hydroponics

Mineral growing media (Inorganic)

Perlite◦ Alumino-silicate◦ Chemically inert◦ Light weight◦ Porous material

Increase water uptake

Vermiculite◦ Derived from mica◦ Can help balance

nutrients◦ Very light weight◦ Often used to cover

seeds in propagation

Mineral growing media

Sand◦ Use sharp sand◦ Used to improve

drainage in other media 1:1 peat/sand mix –

seed germination 3:1 peat/sand mix –

growing on

Grit◦ Crushed rock◦ Larger particles than

sand◦ Mostly used for

alpine plants in the growing medium or as top dressing

Mineral growing media

Ideally, contact a reliable supplier◦ Companies spend ££ to develop good mixes for

specific crops – take advantage!

Standard mixes include◦ Cuttings◦ Germinating seedlings◦ Potting

Bedding Tree & Shrub Ericaceous (for acid loving plants)

Mixing growing media

Lily compost

Strawberry compost

Ericaceous compost

And more...

Crop specific growing media

What is it?

Rotating or changing the type of crop in one field on a regular basis

Purpose is to◦ Allow soil nutrients to replenish / avoid deficiency◦ Avoid build up of disease in soil◦ Avoid build up of pest population in soil

Crop rotation

What horticulture crops benefit from crop rotation?

Any soil grown crop◦ Vegetables◦ Soft fruit (soil grown)◦ Cut flowers (soil grown)

Why not container grown?

Crop rotation

Crop rotation Orchards can be affected over the very long

term

Removing an old orchard Soil will benefit from green manure or grass ley One year Ploughed back in before replanting new orchard

Puts organic matter back into soil Adds nutrients to soil

Crop rotation - Veg

Home field

Year 1 Potato or

grass

Year 2 Leeks

Year 3 Legume / fertility

Year 4 Brassica

Year 5 carrot or parsnip

Growing media Many options Crop dependant

Crop rotation Most important to soil grown crops with annual

harvest Also beneficial in longer term / more permanent

crops Prevents pest and disease build up Prevents extreme nutrient deficiency

Review

AssessmentLearning Outcome 7 – Describe the growth

stages of a crop group