Plant Nutrition

Jump to each topic by clicking on the relevant box below

What are terrestrial plants?

What are epiphytes and lithophytes?

What is soil texture? The proportion of sand, silt, clay and organic matter in the soil.

What is soil structure? The way that soil particles (sand, silt, clay and organic matter) fit together in the soil. This creates a mix of solid spaces (soil particles) and voids that hold water or air.

What is soil pH? Soil pH is the acidity, neutral status, or alkalinity of soil

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Each number relates to a specific word, so if you think (1)________ is 'bananas' then if (1)________ appears later on in the passage, 'bananas' is the missing word.

Soil is composed of four types of particles: (1) sa________, (2) si________, (3)________ and (4)________ ________:

(1) sa________ is the largest particle, between 0.006 and (5)_____mm in diameter. They are largely made of (6)________ and do not retain (7)________. Soils with a high proportion of (1) sa________ are therefore (7)________ poor.
(2) si________ particles are mid-size, between (8)________ and 0.006mm diameter.
(3)________ particles are the smallest inorganic part of soil, with particles less than (8)________mm. (3)________ particles have the capacity to retain (7)________ and therefore soils with a high proportion of (3)________ particles are generally (7)________ rich.
(4)________ ________ is derived from decomposing plant and animal matter, which breaks down into (9)________ particles. These are even smaller than (3)________ particles and have similar (7)________ holding properties.

Soil is composed of four types of particles: (1) sand, (2) silt, (3) clay and (4) organic matter:

(1) Sand is the largest particle, between 0.006 and (5) 2mm in diameter. They are largely made of (6) silica and do not retain (7) nutrients. Soils with a high proportion of (1) sand are therefore (7) nutrient poor.
(2) Silt particles are mid-size, between (8) 0.002mm and 0.006mm diameter.
(3) Clay particles are the smallest inorganic part of soil, with particles less than (8) 0.002mm. (3) Clay particles have the capacity to retain (7) nutrients and therefore soils with a high proportion of (3) clay particles are generally (7) nutrient rich.
(4) Organic matter is derived from decomposing plant and animal matter, which breaks down into (9) humus particles. These are even smaller than (3) clay particles and have similar (7) nutrient holding properties.

Hint: the missing words in a random order clay, 2, nutrient(s), humus, sand, organic matter, 0.002mm, silt, silica

Extra Hint: (1) sand

Extra Hint: (2) silt

Extra Hint: (3) clay

Extra Hint: (4) organic matter

Extra Hint: (5) 2

Extra Hint: (6) silica

Extra Hint: (7) nutrients

Extra Hint: (8) 0.002

Extra Hint: (9) humus

A

B

C

D

The pie chart represents proportions in an ideal soil. What do letters A - D stand for? A: mineral particles (sand/silt/clay) B and C: water and air (either way around as each should equal 25%) D: organic matter

What is a loam soil? A loam soil has a balance of sand/silt/clay particles, plus organic matter, where no one particle type dominates. This contrasts, for example, to a soil high in sand particles (a sandy soil) or a soil high in clay particles (a clay soil).

What is field capacity? Field capacity is the amount of water a soil can hold once excess water has drained away due to gravity. Soils reach field capacity some hours after sufficient rainfall.

A soil texture test assesses the properties of a soil sample by manipulating it by hand.

Match the description (A, B or C) to the dominant soil particle (1 or 2) as it would feel in a soil texture test:

1. Sand

2. Clay

(one answer is used twice)

A. Sticky with a soapy feel when rubbed between fingers

B. Gritty

C. Can be manipulated into a ring without cracks

Click to reveal answers: A - 2 B - 1 C - 2

Mark the statements about each soil type as true or false:

Sandy soil:

Good water retention
Moderate nutrient retention
Well aerated
Resists compaction
Remains warm in autumn
Slow to warm in spring
Described as a 'heavy' soil

Sandy soil answers: 1: False 2: False (poor nutrient retention) 3: True 4: True 5: False (cools quickly) 6: False (warms quickly) 7: False ('light' soil)

Silt soil:

Good water retention
Poor nutrient retention
Very low air content
Compacts easily
Cools very rapidly in autumn
Very slow to warm in spring
Associated with hilltops

Silt soil answers: 1: True 2: False (high nutrient retention) 3: False (moderate air content) 4: True 5: False (moderate rate of cooling) 6: False (moderate rate of warming) 7: False (associated with floodplains and river deltas)

Clay soil:

Good water retention
High retention of nutrients
Well aerated
Resists compaction
Slow to cool in autumn
Quick to warm in spring
Described as a 'heavy' soil

Clay soil answers: 1: True 2: True 3: False (air spaces are limited; many pores usually filled with water at field capacity) 4: False (compacts easily) 5: True 6: False (slow to warm or cool) 7: true

Loam soil:

Poor water retention
High retention of nutrients
Well aerated
Compacts easily
Moderate autumn cooling
Rapid spring warming
Always found over sandstone bedrock

Loam soil answers: 1: False (high water retention) 2: True 3: True 4: True (due to the clay and silt content loam soils can compact relatively easily) 5: True 6: False (moderate spring warming) 7: False (sandstone bedrock weathers to a sandy soil texture)

What are the soil horizons A - D, below?

A

B

C

D

Click to reveal A - D A: Organic horizon B: Topsoil C: Subsoil D: Bedrock/parent material

Match each statement to the relevant soil horizon:

Low organic matter and humus content
Where the majority of soil organisms are found
Where leaf litter and other plant debris can be found
Darker in colour than the layer below it due to a higher humus content
Weathers over time and partly or wholly responsible for the soil texture above
Usually has a balance of water and air spaces
Lower oxygen content with fewer roots
Where most roots are found

Click to reveal answers 1. Subsoil 2. Topsoil 3. Organic horizon 4. Topsoil 5. Bedrock/parent material 6. Topsoil 7. Subsoil 8. Topsoil

Click to reveal answers A - 6 B - 7 C - 11 D - 2 E - 13 F - 5 G - 10 H - 1 I - 3 J - 8 K - 12 L - 4 M - 9

When nutrients are washed down the soil profile and eventually move to other areas, such as watercourses.
The smallest pore size holding water that's hygroscopic, meaning it's unavailable to plant roots.
When soil is compressed and larger pores collapse, reducing air and available water holding capacity.
Soil water that can be absorbed by plant roots, typically found in mesopores
Rain or irrigation water that flows off the soil surface, potentially causing soil erosion
The gaseous content of soil at field capacity, or of growing media in containers after irrigation water has drained due to gravity
The largest pore size which is typically air filled at field capacity
When the crumb structure at the soil surface is compressed and collapses, creating a compacted layer which impedes air and water infiltration
A measure of the water needed to bring a soil back to field capacity
When water drains into the soil and moves down the soil profile, as happens during rainfall or irrigation
Medium soil pores that hold available water or air; these are desirable in soils to maximise root health
When all the soil pores are filled with water, excluding air from soil pores
The aggregation of sand, silt and clay particles with organic matter to form small units that interlock in the soil. Water drains freely between these units, whilst water is held in the pore spaces within the unit

Match the word(s) to the definition:

A. Air filled porosity (AFP)

B. Macropore

C. Mesopore

D. Micropore

E. Soil crumb

F. Runoff

G. Infiltration

H. Leaching

I. Compaction

J. Soil capping

K. Saturated soil

L. Available soil water

M. Soil moisture deficit

What is primary cultivation?

Describe the impact of primary cultivation on the soil

Primary cultivation breaks up topsoil. This destroys its structure, damages roots, fungi and other soil organisms, including earthworms.

The soil becomes highly aerated with increased oxygen content. If moisture is present and temperature is suitable, this can result in a higher rate of soil organic matter breakdown. This releases carbon dioxide into the air, contributing to global warming. Reduced humus content depletes the soil's capacity to retain water and nutrients, ultimately reducing root health.

Primary cultivation is useful for breaking up compacted soils and as a method of quickly incorporating a high volume of organic matter into the soil (such as compost or well rotted farmyard manure). It can also be useful for removing perennial weed roots and rhizomes from the soil.

What is a mulch?

Name five types of mulch, including at least one organic material and one inorganic material

What is humification?

Explain the impact of the following on humification:

a. Primary cultivation

b. Organic mulches

a. Primary cultivation:

This practice reduces and can reverse humification of soil. This is due to the higher oxygen content of soil following primary cultivation, which increases the potential rate of aerobic respiration in decomposers such as bacteria and fungi that complete the breakdown of humus particles. If organic matter is incorporated during primary cultivation the loss of soil humus is mitigated.

b. Organic mulches:

These increase the organic horizon and supply decomposers and detritivores with a greater food source. As earthworms and other organisms work this organic matter into the soil and decompose it, more humus particles are produced. These accumulate in the soil at a higher rate than they're broken down, resulting in greater humification of soil.

Explain the impact of saturated (waterlogged) soil on root health

Saturated soil lacks air, and therefore oxygen. This means there is no oxygen available for roots' aerobic respiration. Therefore roots can only undertake anaerobic respiration, which has a low energy yield. Less energy means root growth is inhibited as meristematic areas have a slower rate of cell division. Active transport of minerals into roots is also reduced because there is less energy available.

Toxic ethanol, a byproduct of anaerobic respiration, accumulates. This damages and eventually kills root cells, leading to death of plant roots.

How can poor soil management lead to increased saturation (waterlogging) of soil?

Soil that is compacted due to activities such as high foot traffic or machinery has fewer macropores and mesopores, and more micropores. The reduction in overall pore size means there are fewer larger pore sizes, which hold air at field capacity, and a higher proportion of smaller pore sizes, which hold water at field capacity. Therefore soil that has been allowed to become and remain compacted will saturate more easily.
High clay content soils that experiences a loss of soil humus due to primary cultivation and insufficient organic matter inputs (e.g. lack of organic mulch) will saturate more easily. This is because reduced soil humus results in reduced crumb structure in the soil. This means the soil becomes more homogenous, without the multitude of drainage routes between soil crumbs. The overall effect is a proportional increase of smaller soil pores with fewer larger spaces that hold air at field capacity. Therefore clay soils with a low organic matter content will saturate more easily.

Name each type of drainage pattern in the diagrams (A - C) below:

A

B

C

Click to reveal answers A - grid system B - herringbone system C - fan system

The drainage patterns above can be installed with piped drainage.

Complete the labels (1 - 4) on the cross-sectional diagram of a piped drain, below:

1

2

3

4

Click to reveal answers 1. Topsoil 2. Landscape fabric/geotextile 3. Gravel/hardcore/aggregate 4. Perforated pipe

Compare French drains with piped drainage

What is a suitable range of fall gradients for drainage? 1:40 - 1:100

What is a soakaway? A large pit (2m or more deep) predominantly filled with coarse hardcore. It is often installed as an end point for piped drainage. Water fills the soakaway after rainfall and drains deep into the soil. Soakaways are lined with landscape fabric and covered with topsoil.

How far must a soakaway be from a building or road? At least 5m from a building or road (and 2.5m from a property boundary)

What nutrients do plants obtain from air and water? Air: carbon Water: hydrogen and oxygen

What are mineral nutrients? Mineral nutrients are obtained from soil (or other growing media)

What is the difference between macronutrients & micronutrients? Macronutrients are needed in relatively larger amounts when plants are in growth, whereas micronutrients are needed in smaller amounts

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Name the macronutrients and micronutrients obtained from soil:

Macronutrient

Micronutrient

Click to reveal answers Nitrogen Phosphorous Potassium Magnesium Calcium Sulphur

Click to reveal answers Iron Boron Manganese Molybdenum (there are more but these are the only ones listed at RHS level 2)

Essential part of the chlorophyll molecule and important in enzyme activity
Needed for protein formation and essential for oil production
Required for the release of energy in a plant and forms part of the DNA molecule. Often coined 'the root maker'
Integral to the formation of chlorophyll which gives leaves their green colour. Often coined 'the leaf maker'
Required for cell wall formation within plant tissues and provides structural integrity to cell membranes
Promotes flower and fruit formation. Integral to the opening and closing of stomata. Important for plant hardiness to cold and drought resilience. Often coined 'the flower and fruit maker'

Click to reveal answers 1: Magnesium 2: Sulphur 3: Phosphorous 4: Nitrogen 5: Calcium 6: Potassium

Name which macronutrient's role in a plant matches each of the descriptions below:

State one source for each macronutrient:

Nitrogen - Nitrogen fixing bacteria fix atmospheric nitrogen (from the soil's air spaces) into nitrate or ammonia, which can be absorbed by roots. - Lightning converts nitrogen gas into nitrate which is washed into the soil by rain. - Horticulturalists and farmers apply nitrogen or ammonia fertilisers to the soil

Phosphorous - Usually present in sufficient amounts in soils, other than highly acidic soils or those low in organic matter. - Can be applied to the soil via phosphate-rich fertilisers such as superphosphate, rock phosphate, bonemeal or manure.

Potassium - Naturally becomes available to plants as soil clay particles weather. - Present in sulphate of potash or potassium fertilisers. - Present in powdered rock (e.g. powdered granite), and in wood ash

Magnesium - Naturally released from rock weathering and decomposition of organic matter. - Epsom salts contain magnesium. They can be dissolved into irrigation water or scattered onto the soil and watered in. - Dolomite limestone scattered onto the soil contains magnesium.

Calcium - Usually abundant in soils, though might be lacking in sandy soil that's experienced leaching. - Present in manure, bonemeal or seaweed fertilisers. - Present in calcium nitrate fertiliser.

Sulphur - Usually abundant in soil, though might be lacking in sandy soil that's experienced leaching. - Present in fertilisers such as manure; seaweed; blood, fish and bone - Magnesium sulphate and sulphate of potash fertiliser

Needed for cell division in meristems and cell growth, as well as being a component of cell walls. It's also involved in the transport of carbohydrates and proteins in a plant.
Involved in the production of chlorophyll and has a role in a plant's enzyme processes.
A constituent of chlorophyll and required for respiration.
Important for absorption of potassium and essential for the fixing of nitrogen in legume root nodules

Click to reveal answers 1: Boron 2: Manganese 3: Iron 4: Molybdenum

Name which micronutrient's role in a plant matches each of the descriptions below:

State one source for each micronutrient:

Boron - Usually present in sufficient quantities in most soils. - Compounds of boron are present in many synthetic fertilisers. - Present in small amounts in manure and other organic fertilisers.

Iron - Usually present in sufficient quantities in most soils but becomes less available in high pH soils - Manure; blood, fish and bone; bonemeal and seaweed fertiliser all contain iron - Iron chelate and sulphate of iron fertilisers both contain iron

Manganese - Usually present in sufficient quantities in most soils, but in high pH soils it becomes less available. - Organic fertilisers such as seaweed based products or blood, fish and bone contain manganese. - Manure contains manganese. - Manganese sulphate fertiliser.

Molybdenum - Usually present in sufficient quantities in most soils. - Found in organic fertilisers such as blood, fish and bone or seaweed fertiliser. - Present in manure.

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Garden plants require fertiliser to ensure healthy growth
Plants suitable for growing in clay soils do not need fertiliser
Sandy soil is low in nutrients so plants will need fertilising
If 'right plant, right place' is practiced, fertiliser is unnecessary
Fertiliser is often used to increase the rate of plant growth
If a shrub is heavily pruned it will need fertilising to support regrowth
Too much fertiliser can lead to rapid but weak growth
Fruiting plants need high potassium fertiliser to bear fruit

True or false?

Click to reveal answers 1: False 2: True 3: False (plants suitable for sandy soils do not need fertiliser; annual mulching helps to supply nutrition) 4: True 5: True 6: False (in healthy soil that's mulched annually fertiliser is never necessary as long as plants are suitable for the soil type) 7: True (rapid, weak growth is more susceptible to pest and pathogen attack) 8: False (healthy, mulched soil has ample potassium for healthy fruiting as long as the plants are suitable for the soil type)

At RHS level 2 the carbon, nitrogen and phosphorous cycles need to be understood at an introductory level:

(Note: this means that details and extra processes are missing. This is just an introduction to these complex cycles)

What process matches 1 - 4 (the same process might match to different numbers) 1. Photosynthesis 2. Respiration 3. Respiration 4. Consuming/eating 5. Respiration

The Carbon Cycle:

Carbon dioxide in the atmosphere

Plants

2

1

3

5

Animals

Decomposers, fungi, and bacteria

Dead organisms and waste

4

In what chemical reaction does carbon enter the food chain?
What source of energy is required for carbon to enter the food chain?
How does carbon enter the atmosphere from living organisms?
Name the substance that forms a long term carbon store in most soils
What happens to dead organic matter in waterlogged soil conditions, such as in bogs?

1. In what chemical reaction does carbon enter the food chain?

Photosynthesis

2. What source of energy is required for carbon to enter the food chain?

Light

3. How does carbon enter the atmosphere from living organisms?

Carbon dioxide is released as a byproduct of aerobic respiration

4. Name the substance that forms a long term carbon store in most soils

Humus

5. What happens to dead organic matter in waterlogged soil conditions, such as in bogs?

Organic matter cannot fully decompose in waterlogged soils due to a lack of oxygen. It partially decomposes and forms peat.

3

Nitrogen fixing soil bacteria

The Nitrogen Cycle:

Nitrogen gas in the atmosphere

Nitrifying soil bacteria

Dead organic matter

Plants

1

2

6

5

4

What substance, process or organism matches to 1 - 6? 1. Ammonium 2. Nitrate 3. Lightning converting nitrogen into nitrate, which is washed into soil by rain 4. Nitrogen fixing bacteria in legume root nodules 5. Denitrifying bacteria 6. Ammonium produced by decomposers

How is nitrogen used plants?
Name the process by which nitrates enter root hair cells
What general process happens to dead organic matter that returns nutrients like nitrogen to the soil?
Why do legumes have an advantage on sandy soil over most non-legume plants?
State the advantages and disadvantages of summer thunderstorms to outdoor vegetable growers

1. How is nitrogen used plants?

Nitrogen is used in the formation of proteins in plants. This includes enzymes, which are involved in chemical reactions. Pigments such as chlorophyll, which is integral to photosynthesis, are also made of protein.

2. Name the process by which nitrates enter root hair cells

Nitrates are taken into root hair cells via active transport.

3. What general process happens to dead organic matter that returns nutrients like nitrogen to the soil?

Decomposition by organisms like bacteria and fungi returns nitrogen and other nutrients to the soil

4. Why do legumes have an advantage on sandy soil over most non-legume plants?

Legumes have root nodules that contain symbiotic nitrogen fixing bacteria. This means legumes have a sufficient nitrogen supply in sandy soils, which are low in nitrogen. This gives them a competitive advantage over other plants because they will not experience nitrogen deficiency.

5. State the advantages and disadvantages of summer thunderstorms to outdoor vegetable growers

Lightning during thunderstorms converts nitrogen into nitrates, which wash into the soil in rain. Unlike nitrogen gas, nitrates can be absorbed by plants through their root hair cells. Therefore thunderstorms increase the availability of nitrates in the soil, benefitting plant growth.

Whilst heavy rain can replenish soil water in summer thunderstorms, heavy rain likely to result in runoff causing soil erosion. This removes topsoil, which is essential for healthy plant growth.

3

Soil

Plants

Incorporation into sedimentary rocks

Dead organisms and waste

The Phosphorous Cycle:

Phosphate in bedrock beneath soil

1

2

What three different processes match 1 - 3? 1. Weathering 2. Leaching (phosphates enter water courses and eventually the ocean) 3. Uplift of rocks containing phosphorous

Name the process by which phosphorous enter root hair cells
How does phosphorous (and all mineral nutrients) move from the roots to above ground parts?
Name two general types of decomposers that return phosphorous to the soil from dead organic matter
Why is phosphorous essential to healthy plant growth?

1. Name the process by which phosphorous enter root hair cells

Active transport

2. How does phosphorous (and all mineral nutrients) move from the roots to above ground parts?

As a dissolved mineral in water that moves within the xylem

3. Name two general types of decomposers that return phosphorous to the soil from dead organic matter

Bacteria and fungi

4. Why is phosphorous essential to healthy plant growth?

Phosphorous is an essential part of the DNA molecule. It's also needed for the release of energy in a plant.

How are the following three nutrients artifically added by growers to increase plant growth?

Carbon Only in glasshouses or other protected structures. Carbon dioxide gas can be added to the atmosphere within growing spaces to increase its concentration and therefore availability to plants. This is not undertaken outdoors as the carbon dioxide would quickly dissipate into the atmosphere.

Nitrogen - The Haber-Bosh process is used at industrial scale to convert atmospheric nitrogen to ammonia. Other processes are used to convert the ammonia into nitrates. - Fertilisers are produced using these products. - These can be added as a granular application to soil or growing media, or dissolved into water and applied via irrigation (called fertigation)

Phosphorous - Rock rich in phosphorous are mined and phosphorous is extracted for use in fertiliser. - Fertiliser containing phosphorous can be added as a granular application to soil or growing media, or dissolved into water and applied via irrigation (called fertigation)

Mineralisation of organic matter and rocks:

What is mineralisation of organic matter?

State the conditions that maximise the rate of mineralisation of organic matter

What is mineralisation of rocks?

State the conditions that maximise the rate of mineralisation of rocks

Each number relates to a specific word, so if you think (1)________ is 'bananas' then if (1)________ appears later on in the passage, 'bananas' is the missing word.

The Rhizosphere:

The rhizosphere is a narrow area around a plant's (1)________ where soil microorganisms like (2) b________ and f________ interact with (1)________ to exchange substances, for example (3)________ obtained by soil microorganisms are exchanged for (4)________. As (4)________ are produced in the leaves as the useful product of (5)________, healthy plants with a high rate of (5)________ produce more (4)________. As a result they have a more active rhizosphere. (4)________ are translocated in a plant's (6)________, which flows through vessels called (7)________. Plants that are suffering from pests or (8)________ have a reduced ability to translocate (4)________ to the (1)________. Therefore they have a less healthy rhizosphere and a lower uptake of (3)________. This can lead to (9) n________ d________.

The Rhizosphere:

The rhizosphere is a narrow area around a plant's (1) roots where soil microorganisms like (2) bacteria and fungi interact with (1) roots to exchange substances, for example (3) minerals/nutrients obtained by soil microorganisms are exchanged for (4) carbohydrates/sugars. As (4) carbohydrates/sugars are produced in the leaves as the useful product of (5) photosynthesis, healthy plants with a high rate of (5) photosynthesis produce more (4) carbohydrates/sugars. As a result they have a more active rhizosphere. (4) carbohydrates/sugars are translocated in a plant's (6) sap, which flows through vessels called (7) phloem. Plants that are suffering from pests or (8) pathogens have a reduced ability to translocate (4) carbohydrates/sugars to the (1) roots. Therefore they have a less healthy rhizosphere and a lower uptake of (3) minerals/nutrients. This can lead to (9) nutrient deficiencies.

Hint: the missing words in a random order pathogens, carbohydrates/sugars, roots, nutrient deficiencies, fungi, photosynthesis, sap, bacteria, phloem

Extra Hint: (1) roots

Extra Hint: (2) bacteria and fungi

Extra Hint: (3) nutrients

Extra Hint: (4) carbohydrates/sugars

Extra Hint: (5) photosynthesis

Extra Hint: (6) sap

Extra Hint: (7) phloem

Extra Hint: (8) pathogens

Extra Hint: (9) nutrient deficiencies

What is the impact of synthetic fertilisers on the rhizosphere?

Synthetic fertilisers supply nutrients to plant roots in available forms, meaning root hair cells can undertake immediate uptake via active transport. This means they do not have to exchange carbohydrates for mineral nutrients as they do in the rhizosphere. Therefore microorganisms in the rhizosphere have reduced symbiotic interactions with roots. Symbiotic microorganisms become less abundant in the rhizosphere, reducing its biodiversity. This means plants become more reliant on synthetic fertiliser inputs. If a synthetic fertiliser is not complete (meaning it lacks one or more nutrient), plants risk becoming nutrient deficient.

How can nutrients be supplied to plants in a way that sustains rhizosphere health?

Fostering and maintaining a high level of soil biodiversity is essential for rhizosphere health. Soil inputs, such as organic matter via mulch, ensure a continuous food source for soil microorganisms and detritivores such as earthworms. As soil microorganisms in the rhizosphere break down and mineralise organic matter, mineral nutrients can be exchanged with plant roots for carbohydrates. This sustains rhizosphere health and maintains nutrition to roots.

In some situations additional nutrition is required. Organic fertilisers, such as seaweed extract or bonemeal, need to be broken down by soil microorganisms in order for mineral nutrients to be released. Organic fertilisers interact with microorganisms in the rhizosphere, preserving rhizosphere health.

This shrub is growing in multipurpose compost in a container.

What will happen to the concentration of available plant nutrients over time?
How can persistent heavy irrigation affect the nutrient content of the compost?
The grower has noticed many of the older leaves are turning yellow. What is happening inside the plant to cause the leaves to yellow?
The plant's growth has also slowed down through the growing season. What kind of fertiliser would most quickly restore the plant's growth rate ? Give a reason for your answer.
What are the sustainability considerations of using the kind of fertiliser named in your answer to Q4?

1. What will happen to the concentration of available plant nutrients over time?

Their concentration will decrease

2. How can persistent heavy irrigation affect the nutrient content of the compost?

Nutrients can be leached from the compost and lost from the container in water draining from the container's basal drainage holes. This will decrease the nutrient content of the compost.

3. The grower has noticed many of the older leaves are turning yellow. What is happening inside the plant to cause the leaves to yellow?

Due to nutrient deficiency the plant is translocating nutrients from the older leaves into younger growth, causing chlorosis of older leaves.

4. The plant's growth has also slowed down through the growing season. What kind of fertiliser would most quickly restore the plant's growth rate ? Give a reason for your answer.

A synthetic, complete fertiliser will provide the plant with all the nutrients it needs in immediately available forms, meaning the nutrients can be actively transported into root hair cells and used in plant growth.

5. What are the sustainability considerations of using the kind of fertiliser named in your answer to Q4?

Synthetic fertilisers have a high carbon footprint of manufacture and transport. If over applied in combination with excessive irrigation they can contribute to eutrophication of water bodies, which is harmful to biodiversity.

A fertiliser has 2:1:2 on the label. What do these numbers mean? This is the ratio of N : P : K in the fertiliser. N = nitrogen, P = phosphorous, K = potassium

What is a straight fertiliser? A fertiliser that contains only one type of nutrient

What might a 2:1:1 fertiliser be advertised for use on? Lawns or other promotion of leafy growth, e.g. for lettuce. (Higher nitrogen content promotes leafy growth)

What is a compound fertiliser? A fertiliser that contains more than one type of nutrient

What might a 4:3:8 fertiliser be advertised for use on? Flowering and fruiting plants such as roses, strawberries, raspberries, etc. (High potassium content promotes flowering and fruiting)

What is an organic fertiliser? Fertiliser: a concentrated source of plant nutrients Organic: derived from once-living source(s)

State three ways that fertilisers can be applied

Top dressing: fertiliser is incorporated into the soil surface, e.g. by scattering on and lightly forking in.
Base dressing: fertiliser is scattered onto the soil at the base of a planting pit before the plant is placed.
Incorporation into growing media, e.g. by mixing fertiliser into potting mix prior to potting up plants.
Fertigation/liquid feeding: soluble fertiliser is dissolved into water which is used to irrigate plants.
Foliar feed: soluble fertiliser is dissolved into water and sprayed over plant leaves.

What is fertiliser tea (aka compost tea)?

Plants such as comfrey are harvested and placed in water. Over time they ferment and produce a concentrate liquid. This can be diluted and watered into soil where plants are growing.

Wormeries can also be used. These use tiger worms to digest kitchen waste and other organic material. Liquid drains to the bottom of the wormery and is drained via a tap, providing a concentrate that can be diluted and used to irrigate plants.

What are typical symptoms of excess fertilisation of a plant?

1. What is biochar?

2. Describe its use in horticulture

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How are pH and nutrients linked?
State an ideal pH for most plants
What is an ericaceous plant?
What nutrient are ericaceous plants unable to obtain sufficient quantities of in the wrong soil pH?
How does a low pH affect potential soil life?

1. How are pH and nutrients linked?

pH affects the availability of different nutrients to plant roots, with some nutrients becoming more available or less available as pH changes.

2. State an ideal pH for most plants

pH 6.5

3. What is an ericaceous plant?

A plant that requires acidic soil, e.g. pH 5 - 6, for healthy growth.

3. What nutrient are ericaceous plants unable to obtain sufficient quantities of in the wrong soil pH?

Iron

4. How does a low pH affect potential soil life?

As soils become more acidic they become increasingly hostile to a range of soil life, including detritivores such as earthworms. In general, the more acidic a soil's pH, the lower the soil's biodiversity.

What type of bed rock results in an alkaline soil? Limestone or chalk

How can a soil's pH be determined? - Soil samples can be tested for their pH. Samples should be taken in a W formation across the site. Samples should be from at least 10cm below the surface. - Samples can be sent to labs for detailed analysis, or - Home pH kits can be purchased. These use universal indicator or litmus paper to indicate pH via a colour change.

What type of soil has the highest resistance to pH change? Clay soils have the greatest capacity to resist a change in pH. (This is due to their high buffering capacity)

Answers: 1. False 2. True 3. False - limestone is basic (alkaline) and will raise pH 4. True - powder has a higher surface area than the same mass of chips, meaning it has a more rapid influence on soil pH 5. True - pine needs are acidic 6. False - vinegar is highly acidic and will damage or kill roots 7. True 8. False - required PPE includes gloves, coveralls, goggles, dust mask 9. True 10. False - alkalinity from the chalk bedrock will always eventually neutralise acidity in the soil above, with alkaline soil pH returning

True/False:

Soil pH cannot be raised
Lowering the soil pH will increase its acidity
Adding dolomite limestone will lower soil pH
Ground limestone is faster acting in changing soil pH than limestone chips
A mulch of composted pine needles is an acidifying influence on soil
Watering ericaceous plants with vinegar will create suitably acidic soil conditions
Flowers of sulphur is used to lower soil pH
The only recommended PPE for applying flowers of sulphur is gloves
It's easier to raise soil pH than lower it
Soils on chalk bedrock can have their pH permanently lowered if sulphur chips are dug into the soil

A traditional allotment grower applies lime to part of their plot every year in accordance with their crop rotation. Why are they doing this?
How might the integration of 'best practice' change this grower's standard procedure in the application of lime?

1. A traditional allotment grower applies lime to part of their plot every year in accordance with their crop rotation. Why are they doing this?

The grower is liming the area where they will grow brassicas. This is to prevent club root disease from affecting the brassica crops. Club root cannot survive in alkaline soil. Lime is alkaline and raises the soil pH

2. How might the integration of 'best practice' change this grower's standard procedure in the application of lime?

Best practice will require a more evidence-based approach. The grower should test their soil with samples taken in a W formation across the intended brassica growing area, each sample from at least 10cm deep. If the soil is alkaline then lime does not need to be applied If the soil is not alkaline then the amount of lime added should be carefully calibrated to respond to the pH change needed and the soil type (reflecting the buffering capacity of the soil).

Name three ericaceous plants

Challenging:

A traditional allotment grower increasingly finds their brassicas have a hollow stem as pictured. They have decided to apply a greater amount of lime to their brassica growing area next year in order to prevent this.

Do you agree with their decision?

- If you think they are correct, explain why more lime would prevent this issue

- If you think they are incorrect, explain what they should do instead to successfully rectify the issue

Hollow stem in brassicas is due to boron deficiency. The grower would apply lime, which creates alkaline soil conditions, to prevent club root. By making the soil alkaline nutrient availability will change. If they applied too much lime, creating highly alkaline conditions, boron becomes less available to roots. This will result in boron deficiency. Therefore the grower should assess their soil's pH before applying lime, and only apply enough lime to ensure the soil is lightly alkaline, e.g. no higher than pH 7.5 (but above pH 7).

If it's not pH related the boron deficiency could otherwise be due to a low-nutrient soil, such as if they're growing brassicas on sandy soils. In this case they should apply an organic fertiliser containing boron to boost soil fertility in the short term. To improve the soil in the long term they should mulch their soil annually with organic matter to improve nutrient content and nutrient retention.

Up

What is growing media? Any substance used to grow plants in a container. Typically it is formulated with one or more ingredients.

What is compost? Compost is derived from decayed organic matter. It is usually fairly uniform with a loose, crumbly texture and is dark in colour.

What growing media is used in hydroponics? An inorganic growing media such as LECA or rock wool

A. Seed and cutting compost

B. Multi-purpose compost

C. Ericaceous compost

D. Loam-based compost

Answers: A: 5, 6 B: 3, 8 C: 1, 7 D: 2, 4

Ideal for growing plants that require growing media with a pH below 6.
Best used to grow plants in containers for long periods; it does not break down over time, allowing a long term healthy root environment
Can be used for growing on plants, sowing seeds, mulching beds and borders and other uses.
Contains a mix of sand, silt, clay and organic matter in a ratio e.g. 8:8:4:1, respectively
Contains a high proportion of freely draining material such as perlite, e.g. 1:1 compost:perlite
Ideal for rooting cuttings or sowing seeds into
Can be loam based or loam-less, but will always have an acidic ingredient such as elemental sulphur; typically moisture retentive
Usually formulated from 100% decomposed plant material and has a relatively uniform texture, though this varies depending on the manufacturer.

Each compost matches two of the statements:

One for its general formulation

One for a potential use

(e.g. B could match to 2 and 5)

State one property of each bulk constituent that could be added to a growing media formulation:

Composted bracken - Acidic - High in nitrogen and potassium - Can improve aeration and water retention

Grit - Improves drainage of a growing media formulation - Heavy, adding weight to the formulation

Rockwool - Excellent water retention within cubes - High air filled porosity between cubes - Poor nutrient holding capacity - Lightweight when dry but heavy when saturated (Usually only used in hydroponics or for growing specialist plants such as some types of orchids)

Coir - High water holding capacity - Good nutrient retention - Lightly acidic

Loam - High water holding capacity - High nutrient retention - Heavy, adding weight to containers - Good drainage and air filled porosity

Sand - Coarse sand improves drainage and aeration of growing media - Fine sand can reduce aeration and increase water holding capacity - Does not aid nutrient retention - Heavy, adding weight to containers

Composted organic matter - High water retention - High nutrient retention - Variable texture depending on the source organic matter

Perlite - Improves drainage in growing media - Lightweight, reducing the weight per volume of growing media - Does not aid water retention

Vermiculite - Lightweight - Improves water retention - Improves nutrient retention

Why is aquatic growing media free from organic matter or lightweight inorganic ingredients?

State a growing media formulation for succulents

Describe three properties of growing media suitable for epiphytic orchids

State a growing media formulation for epiphytic orchids