R2102: Plant nutrition and the root environment Flashcards
Exam syllabus notes for personal revision for RHS Level 2 exams. All information in answers is my own gathered by independent research across multiple resources and media. Feel free to study however I take no responsibility for any inaccurate information being provided.
(1.1) Describe the natural processes of soil formation:
weathering of parent rock: (PHYSICAL, chemical and
biological), addition of organic matter.
(NOTE: I have split this question up due to the amount of information contained in the answer. The term(s) highlighted in CAPITALS are the focus of the answers required for this individual flash card)
PHYSICAL: Physical breakdown of rock, AKA mechanical weathering.
FREEZE/THAW: The expansion and contractions of water freezing and thawing within cracks in the rock, gradually breaking down into smaller pieces.
EXFOLIATION: Breaks off layers of rock which causes expansion and breakage fractures due to pressures produced.
HEAT EXPANSION: Rocks expand when hot and contract when cooled, if temperature changes are rapid or extreme the rock fractures.
ABRASION: Solid particles carried by air, water or ice that gradually breaks down rock surfaces.
(1.1) Describe the natural processes of soil formation:
weathering of parent rock: (physical, CHEMICAL and
biological), addition of organic matter.
(NOTE: I have split this question up due to the amount of information contained in the answer. The term(s) highlighted in CAPITALS are the focus of the answers required for this individual flash card)
CHEMICAL WEATHERING: Breakdown of rocks, changing of parent rocks chemically and slowly, mineral particles are released for further breakdown.
CARBONATION: When carbon dioxide dissolves in water to form weak solution of carbonic acid. Reacts with lime in rocks to create calcium deposits (stalactites & stalagmites)
OXIDATION: Atmospheric oxygen fuses with metallic ions to produce oxides or hydroxides. Oxidation of some rocks helps breakdown others and creates rusty red colouration in iron rich soils.
HYDROLYSIS: Interaction between minerals and water that generates new minerals or dissolved compounds.
HYDRATION: When rocks absorb water and expand becoming vulnerable to physical weathering like freeze/thaw.
(1.1) Describe the natural processes of soil formation:
weathering of parent rock: (physical, chemical and
BIOLOGICAL), addition of ORGANIC MATTER.
(NOTE: I have split this question up due to the amount of information contained in the answer. The term(s) highlighted in CAPITALS are the focus of the answers required for this individual flash card)
BIOLOGICAL: Involves physiological activities of organisms and gradual accumilation of organic matter. These materials slowly mix with the minneral fraction to generate final mix of organic-mineral material that acts as the basis for soil production.
PLANTS & ANIMALS: Roots of plants widens cracks, burrowing/tunnelling animals mix soil/sediment/organic fractions which allows water to move in quicker and deeper thus increasing rate of weathering processes.
Describe the development of main horizons: organic layer, topsoil, subsoil, parent rock.
1: Bedrock begins to disintergrate
2: Organic materials facilitate disintergration
3: Horizons form
4: Developed soil supports thick vegetation
(from TOP to BOTTOM) ORGANIC LAYER (O): Layer of dead and decomposing matter on the surface. As it builds up it decomposes and is acted upon by detritivores, fungi and bacteria and becomes incorporated as humus into the top soil.
TOPSOIL (A): Uppermost horizon in soil and is the area where root growth is concentrated. Can vary in depth but a spades blade depth is considered good for successful plant growth. Chracterised by darker colour due to presence of incorporated organic matter through cultivation or natural decomposition.
SUBSOIL (B): Below topsoil and characterised by its mineralised and pale colour- lacks organnic matter.
Not suitable for plant growth though tap roots will penetrate it. Poor structure and lack of airspaces. Leeching of minerals from topsoil may also make it high in toxic elements.
PARENT ROCK (C): Underlying rock. In many cases will be the same as the mineral and rock particles in above layers but not always. Some soil is formed by rock fragments from elsewhere eg: brought by water or glaciers. The parent rock influences the nature and properties of the soil like texture and pH level.
(1.2) Compare and contrast the properties of topsoil
with subsoil: organic matter content (living and
dead organisms, humus), colour, pore space,
aeration, water content, nutrient content.
Suitability for plant growth.
TOPSOIL:
ORGANIC MATTER - High in living and dead organisms, humus, humus/clay complex present.
COLOUR - Dark due to organic matter. Rich brown from various mineral oxides and black from humus.
PORE SPACE - Good due to crumbly texture.
AERATION - High.
WATER CONTENT - High.
NUTRIENT CONTENT - High, affected by amount of organic matter with optimal pH.
PLANT SUITABILITY - High. Aerated, good water and mineral levels, loose to allow rooting with optimal aeration. Warm as closer to the surface.
SUBSOIL: ORGANIC MATTER - Low COLOUR - Pale/light. Lacks humus/organic matter. Spots of other colours like yellow/grey from built up minerals. PORE SPACE - Minimal, compacted AERATION - Low. WATER CONTENT - Low. NUTRIENT CONTENT - Low. PLANT SUITABILITY - Low. Often compacted with little aeration. Subsoil often anaerobic and waterlogged. Cooler as further below surface.
(1.3) Define the term ‘soil texture’.
Particle sizes of stones, sand, silt, clay (using Soil
Survey England and Wales classification).
Soil texture = PARTICLE SIZE. Relates to and is defined by the particle size using Soil Survey England and Wales classification. CLAY: <0.002mm SILT: 0.002-0.05mm SAND: 0.05-2.00mm STONES: 2.00mm+
(1.3) Describe the characteristics of the following soils:
sandy loam, silty loam and clay loam: feel (gritty,
silky, sticky/hard), nutrients, water retention,
temperature.
LOAM: Soil with a combination of sand, silt and clay. Most desirable as it incorporates advantages of all types.
SANDY LOAM: Grity to touch, high aeration, low water retention, warms rapidly, quick loss of nutrients.
SILTY LOAM: Silky and smooth to touch, more cohesion than sand but weak when wet, may become compacted, ow in nutrients, medium temperature.
CLAY LOAM: Sticky when wet, hard when dry, retains nutrients but has poor drainage, cool due to high moisture content.
(1.4) Define the term ‘soil structure’.
Soil structure = GROUPS/AIRSPACES OF PARTICLES (AGGREGATES). Refers to the manner in which individual particles are grouped together in the soil for example small crumbs or large clods. It’s the size and shampe of these groups (ped/aggregates) and the way theu are distributed and the pores between that defines the type of soil structure.
(1.4) Describe crumb structure and its influence on plant growth: crumb formation and destruction.
Optimal crumb structure often found in topsoils that have good balance of cly, silt and sand with high levels of organic matter.
In such soils the structure is open with optimal pore space for good soil fertility, water capacity and air content, all of which enable good root penetration.
Generally formed and improved by cultivation and incorporation of organic matter.
Can be disrupted and destroyed from over cultivation or compaction ehich often removes critical pore spaced that are essential for healthy plant growth.
(1.4) Describe the relation between pore space, air and water.
MACROPORES (large pores):
Well aerated but have low capacity for water storage. Low total porosity.
MICROPORES (small pores):
Hold large quantities of water and are often waterlogged. High total porosity.
Pore size is more important than total pore space. The balance between macropores (air and water movement) and micropores (water retention) are found in medium textured soils like loams.
(1.4 ) Describe saturation point, field capacity, available water content, permanent wilting point, soil moisture
deficit.
SATURATION POINT: When all pores are submerged and soil becomes waterlogged.
FIELD CAPACTIY: The surface tension forces of the soil particles is balanced with the forces of gravity
and soil is now holding the max amount of water against gravity. At field capacity there is a balance between air filled pores and water remaining surrounding soil particles.
AVAILABLE WATER CONTENT: The max amount of water held in soil that can be accesed by the plants. AWC is often descried as the amount of water between its field capacity and permenant wilting point.
PERMANENT WILTING POINT: When all available water has been used or lost in the soil the remaining water is tightly bound to the soil particles and is not available to plants. At this point the plant will wilt unless topped up by irrigation.
SOIL MOISTURE DEFICIT: The amount of water required to be added to get back to field capacity.
(1.4) Explain the importance of an appropriate balance between air
and water for the healthy growth of plants.
Water content of soil affect its formation (erosion and stability) and may not support plants if incorrectly maintained.
Soil is drained to allow airflow to roots.
Water is needed for photosynthesis, respiration and as a transport medium for nutrients.
Air is required for root growth, anearobic conditions as found in waterlogged soils can kill plants.
Too little water and plant may not recover from wilting.
(1.5) Describe cultivations, to include single and double digging, rotary cultivation, forking, raking,
consolidation; ‘no dig’ method; bed systems.
PRIMARY-
SINGLE DIGGING: Taking out a spit (spades depth) of soil and turning it over row by row. Spit is inverted so weeds are at the bottom.
Used to turn soil annually for new seasons planting. Mainly ued to remove perennial weeds, helps to reduce compaction and provides opportunity to incorporate organic matter, fertilisers and lime where necessary.
DOUBLE DIGGING: Single digging but soil below (second spit) is loosed with a fork and bulky organic matter incorporated.
Reduces compaction. Normally done on undug land or every 4-5 years on previously cultivated land.
ROTARY: For larger areas requiring cultivation a pwered rotavator may be used.Speedy but repeasted use may create a hard pan at blade depth where machine smears soil.
SECONDARY-
FORKING: May be promary when used with digging but alone generally refers to use of a fork to remove week growth or loosen soil surface.
CONSOLIDATION: Firming down of the ground prior to levelling and raking to drive out excess air. Done by heels of feet one way across area then at right angles.
RAKING: Levels the soil in preparation for sowing or planting and creates a suitable tilth.
‘NO DIG’: Layer of organic matter applied each year to undisturbed area in to which plants are placed. Avoids disturbance of balance of soil and organisms.
BED SYSTEMS: Planting in narrow bed accessible from both sides for weeding. Compation avoided as beds are not stepped on. Can also be constructed as raised beds.
(1.5) Describe how the
root environment benefits from the addition of organic and inorganic material
(grit/sand, lime).
ORGANIC MATERIAL: Helps to bring mineral soil particles into stable crumbs and improves aeration. Increases available water capacity.
Physical benefits: Stabilises structure, improves water holidng characteristics, lowers bulk density, dark colour my improve thermal properties.
Chemical benefits: Acts as a p buffer, complexes metals meventing toxicity.
Biological benefits: Sipplied energy to soil organisms, source and sinnk for nutrients, increasons microbial populations.
INORGANIC MATERIAL:
Sand/Grit: Adding to clay soils can help open up structure to improve drainage and aeration.
Lime: Ading to clay soils causes flocculation (clumping of soil) to improve its workability.
(1.5) Describe how to avoid and the removal of compaction (pans and surface ‘after capping’; mulching, green manure, timing of cultivation, ‘sub-soiling’).
To reduce/remove compaction:
MULCHING: Adding organic surface mulch absorbs pressure from foot traffic and protects bare soils from rain. Helps prevent caps forming.
GREEN MANURE: Crops that are not intended for harvest but act to retain nutrients and cover soil until planting season. Bare soil vulnerable to erosion and leaching from rain.
SUBSOILING: Using a subsoiler pulled trough soil will help break up and help alleviate compaction. can break up caps and pans.
TIMING OF CULTIVATION: Do not cultivate when soil it too wet (saturated, too dry or frozen.
Avoid walking on soil especially in wet conditions.
Practice reduced cultivation, no cultivation or bed systems.
Notes:
SOIL CAPPING: When aggregates breakdown from rain impact or wet conditions (slaking) and forms a crust on soil surface preventing new shoots emerging and blocks oxygen supply. Can be avoided with mulching and broken up with subsoiling.
SOIL PANS: Continuous hard layers within soil caused by ploughs and compressed soil below the the surface caused by rotavators. Can be broken uop by subsoiling.
(1.5) Describe how to manage soil water content: identify poor drainage (surface symptoms, soil colour, soil smell, indicator plants, surface run off).
Drainage aims to fill macropores with air but keep micropores saturated with water. Poor frainage means bot macro and micropores are saturated. Ensure soil has correct structure with adequate drainage and maintain correct irrigation practices.
Symptoms of poor drainage:
Standing water.
Surface run off.
Grey/blue-ish soil indicates waterlogging over long period of time.
Hydrogen sulphide produced in anaerobic breakdown of organic matter, soil will smell of rotten eggs.
Indicator plants such as sedges used to identify poor drainage.
(1.5) Identify causes of excess water (compaction, run
off e.g. patios, high water table).
Identify appropriate ways of dealing with excess
water (soakaway, french drain, raised bed,
appropriate planting).
CAUSES: Compaction in soil. Poor drainage. High levels of run off. High water table.
HOW TO DEAL WITH:
SOAKAWAYS: Where water moves down a trench into a deep excavation filled with course drainging material.
FRENCH DRAIN: A trench filled with hardcore.
RAISED BEDS: Water will move away down and through the beds.
PLANTING: Using plants tat will tolerate higher soil water levels.
(1.5) Identify appropriate irrigation methods (watering
can, hose, sprinkler, seep hose; time of day;
depth of wetting).
NO DETAIL OF DRAINAGE AND IRRIGATION
SYSTEMS ARE REQUIRED.
The amount of moisture soil recieves can be regulated by using correct irrigation methods.
WATERING CAN: Direct application of water to where it is needed as correct quantity.
SEEPHOSE: Water applied direct to soil surface minimising structural damage and maximum infiltratrion.
SPRINKLERS: Maximum and rapid application.
TIME OF DAY: Watering in the evening or at night when temperatures are cooler to minimise evaporation losses.
DEPTH OF WETTING: Soil is wetted to the dept required to replenish soil moisture reverves to minimise evaporation losses.
(2.1) Identify the key categories: dead and living
organic matter and humus.
Food for soil organisms, nutrient release and
recycling.
NO DETAILS OF NUTRIENT CYCLES
REQUIRED.
Describe the benefits of organic matter and influence on soil structure (living, dead
organisms, humus), water availability, workability,
colour.
DEAD: Remains of anything onve alive (plants or animals) falling to or present on soil surface. Provides a food source to organisms as they breakdown and decompose.
LIVING: Animals that inhabit soil surface or below. Includes larger herbivores like rabbits which feed on larger organic debris that then becomes accessible to small detritivores like earthworms. Residue of feeding becomes accessible to microbes, fungi and bacteria. Excretion from birds and animals contribute to plant nutrition in nitrogen cycle.
HUMUS: Ultimate decomposed matter that has reached a stable state once organic matter has been subjected to the above. So decomposed that original source is no longer recognisable.
Adding organic matter increases available water content (especailly in sandy soils), can warm soil by its darker colour and improve workability.
(2.2) Describe the characteristics of the following
materials: FARM YARD MANURE, garden compost,
mushroom compost, composted green waste, leaf
mould, chipped bark, composted straw, green
manure and crop debris.
Describe the appropriate uses for the above
materials, to include: mulching, soil improvement,
nutrient supply.
Describe the benefits and limitations of using the
above materials.
(NOTE: I have split this question up due to the amount of information contained in the answer. The term(s) highlighted in CAPITALS are the focus of the answers required for this individual flash card)
FYM: from cattle/sheep/horses/pigs. Best left to mature as amonia may cause scorch if to fresh.
USE:
Nutrient supply.
Soil improver,
BENEFITS:
Supplies nutrients.
Improves soil structure
Improves water retention.
LIMITATIONS:
Variable nutrient contents
Ammonia causes scorch when too fresh, needs to mature.
Difficult to handle when fresh
(2.2) Describe the characteristics of the following
materials: farm yard manure, GARDEN COMPOST,
mushroom compost, composted green waste, leaf
mould, chipped bark, composted straw, green
manure and crop debris.
Describe the appropriate uses for the above
materials, to include: mulching, soil improvement,
nutrient supply.
Describe the benefits and limitations of using the
above materials.
(NOTE: I have split this question up due to the amount of information contained in the answer. The term(s) highlighted in CAPITALS are the focus of the answers required for this individual flash card)
GARDEN COMPOST: Dark brown, crumbly texture. Made of decomposed plant material.
USE:
Mulch.
Supplies recycled nutrients.
BENEFITS:
Positive affect on soil structure if correctly made.
Sustainable as uses waste products.
LIMITATIONS:
Contains disease organisms, may contain weed seeds and pests.
Takes time to make.
Might have high salt levels.
(2.2) Describe the characteristics of the following
materials: farm yard manure, garden compost,
MUSHROOM COMPOST, composted green waste, leaf
mould, chipped bark, composted straw, green
manure and crop debris.
Describe the appropriate uses for the above
materials, to include: mulching, soil improvement,
nutrient supply.
Describe the benefits and limitations of using the
above materials.
(NOTE: I have split this question up due to the amount of information contained in the answer. The term(s) highlighted in CAPITALS are the focus of the answers required for this individual flash card)
MUSHROOM COMPOST: Spawned on FYM and can contain high chalk levels.
USE:
Soil improver.
Can raise pH.
BENEFITS:
Nutrient residues.
Organic soil improver.
Cheap.
LIMITATIONS:
Pesticide residues.
Excessively alkaline.
Potentially contains fugal diseases.
(2.2) Describe the characteristics of the following
materials: farm yard manure, garden compost,
mushroom compost, COMPOSTED GREEN WASTE, leaf
mould, chipped bark, composted straw, green
manure and crop debris.
Describe the appropriate uses for the above
materials, to include: mulching, soil improvement,
nutrient supply.
Describe the benefits and limitations of using the
above materials.
(NOTE: I have split this question up due to the amount of information contained in the answer. The term(s) highlighted in CAPITALS are the focus of the answers required for this individual flash card)
COMPOSTED GREEN WASTE: Contains anything not mechanically sorted at recycling centres. May contain minor plastic pieces.
USE:
Topsoil/mulch.
Increase aeration in soil structure due to particle size.
BENEFITS:
Available in bulk.
Recycled product.
High in humus builders.
LIMITATIONS:
Variable nutrient levels.
Can be too course.
Potential for fungal dideases.
(2.2) Describe the characteristics of the following
materials: farm yard manure, garden compost,
mushroom compost, composted green waste, LEAF MOULD, chipped bark, composted straw, green
manure and crop debris.
Describe the appropriate uses for the above
materials, to include: mulching, soil improvement,
nutrient supply.
Describe the benefits and limitations of using the
above materials.
(NOTE: I have split this question up due to the amount of information contained in the answer. The term(s) highlighted in CAPITALS are the focus of the answers required for this individual flash card)
LEAF MOULD: Fallen leaves form trees. Alkaline inititally but turns acidic in fermentation.
USES:
Mulch.
Seed sowing compost if well rotted.
Winter bare soil covering.
BENEFITS:
Humified.
Residues of pathogens and pests limited.
Clean and easy to handle.
LIMITATIONS: Contains little to no nutrients.
Sustainability implications (transporting/deforrestation)
Takes time to produce in bulk.
(2.2) Describe the characteristics of the following
materials: farm yard manure, garden compost,
mushroom compost, composted green waste, leaf
mould, CHIPPED BARK, composted straw, green
manure and crop debris.
Describe the appropriate uses for the above
materials, to include: mulching, soil improvement,
nutrient supply.
Describe the benefits and limitations of using the
above materials.
(NOTE: I have split this question up due to the amount of information contained in the answer. The term(s) highlighted in CAPITALS are the focus of the answers required for this individual flash card)
CHIPPED BARK: Made of wood chips, highly decorative.
USE:
Mulch.
Soil contiditioner.
Ornamental top soil.
BENEFITS:
Well aerated
Long lasting.
Weed free.
LIMITATIONS:
May contain toxins.
Dust levels when handled.
Nitrogen immobilisation (less N for plants).
(2.2) Describe the characteristics of the following
materials: farm yard manure, garden compost,
mushroom compost, composted green waste, leaf
mould, chipped bark, COMPOSTED STRAW, green
manure and crop debris.
Describe the appropriate uses for the above
materials, to include: mulching, soil improvement,
nutrient supply.
Describe the benefits and limitations of using the
above materials.
(NOTE: I have split this question up due to the amount of information contained in the answer. The term(s) highlighted in CAPITALS are the focus of the answers required for this individual flash card)
COMPOSTED STRAW: Made of straw and manure, cheap.
USE:
Mulch.
Soil improver.
BENEFITS:
High in humus builders.
Improves soil structure, water holding capabilitites and nutrient holding power.
Pest and disease free.
LIMITATIONS:
High in carbon, can cause nitrogen immobilisation.
Not suitable for small seeded crops or small transplants.
(2.2) Describe the characteristics of the following
materials: farm yard manure, garden compost,
mushroom compost, composted green waste, leaf
mould, chipped bark, composted straw, GREEN MANURE and crop debris.
Describe the appropriate uses for the above
materials, to include: mulching, soil improvement,
nutrient supply.
Describe the benefits and limitations of using the
above materials.
(NOTE: I have split this question up due to the amount of information contained in the answer. The term(s) highlighted in CAPITALS are the focus of the answers required for this individual flash card)
GREEN MANURE: Living mulch of plant crops not used for harvest.
USE:
Living mulch.
Weed control (competition for resources)
Soil protection.
BENEFITS:
Maintains or improves soil structure.
Protects soil from erosion
Prevents nutrient leaching.
LIMITATIONS:
Might include loss of gaseous nitrogen during breakdown.
(2.2) Describe the characteristics of the following
materials: farm yard manure, garden compost,
mushroom compost, composted green waste, leaf
mould, chipped bark, composted straw, green
manure and CROP BEBRIS.
Describe the appropriate uses for the above
materials, to include: mulching, soil improvement,
nutrient supply.
Describe the benefits and limitations of using the
above materials.
(NOTE: I have split this question up due to the amount of information contained in the answer. The term(s) highlighted in CAPITALS are the focus of the answers required for this individual flash card)
CROP DEBRIS: By product of crop production often left on soil surface after harvesting crop.
USE:
Mulch.
Nutrient supply.
BENEFITS:
No cost.
Incorporation into soil eliminates need for composting.
High in nitrogen.
LIMITATIONS:
Can contain pests and disease residues that can infect following crop.
Some plants are slow to breakdown.
Needs to be physically burried to enable fine tilth to be produced for next crop.
