R2102 3.1 – 3.3 Plant Nutrition Flashcards
Role of iron and signs of deficiency?
Involved with chlorophyll production
Symptoms:
Yellowing of leaves – younger ones first
Failure to flower and fruit
What is the standard way to reduce pH?
Sulphur, aluminum sulphate or sulphuric acid are fastest
What are the advantages of liming?
Raises pH and can make other nutrients available
Provides calcium
Encourages worm and bacteria population
Discourages some diseases such as clubroot in brassicas
Makes clay soils workable by flocculation (improved aeration, drainage)
Name 3 plants that prefer acid soils (calcifuges).
- Rhododendron*
- Camelia japonica*
- Pieris japonica*
Name 3 plants for neutral soils.
- Malus*
- Cucumis*
- Daucus*
Name 3 plants for alkaline soils (calcicoles).
- Clematis montana*
- Agapanthus africanus*
- Fagus sylvatica*
Which nutrient is most likely leached form soil and therefore needed to be replaced?
Nitrogen
What is meant by soluble fertiliser?
Give an example.
Dissolves immediately with water
Ammonium sulphate
Potassium chloride
Ammonium nitrate
Superphosphate
Triple superphosphate
What is meant by slow-release fertiliser?
Give an example.
- Doesn’t dissolve immediately with water but provides nutrients in soluble form over a long period of time
- Degrade slowly, usually under the influence of soil micro-organisms to release their nutrients
- Dependant on soil temperature
- Usually organic and include hoof & horn and bone meal
What is meant by a straight fertiliser?
Give an example.
- Supply one major nutrient.
- Usually used to provide different nutrients at different times of the year, or to correct particular nutrient deficiencies.
- Usually inorganic.
Ammonium nitrate (33-35% N)
Superphosphate (21% P)
What is meant by a compound fertiliser?
Give an example.
- They may be organic or inorganic, or contain both
- Supply two or more nutrients of N, P and K (N:P:K), e.g. 20-10-10
- Potassium nitrate (46%K, 14%N) supplied both K and N
- Growmore 7-7-7 supplies 7%N, 7%P, 7%K.
- K: potassium sulphate (50%K)
What is meant by a controlled-release fertiliser?
Give an example.
- Granules of inorganic fertilisers coated with a porous material, such as sulphur or synthetic resin, so release at right time for plant
- Water enters the granule and the fertilisers leach out into the surrounding soil. The warmer the soil, the faster the leaching; this corresponds to plant growth which is faster in warm weather. By varying the thickness of the coating granules can be designed to feed plants for different periods of time.
Osmocote
What is meant by base dressing and when would you apply it?
Fertiliser incorporated into soil
Dug in before sowing/planting
What is meant by top dressing and when would you apply it?
Added to surface of soil
When nutrients are needed after plants are established e.g lawns in autumn
What is meant by liquid feed and when would you apply it?
- Fertilisers dissolved and watered onto soils
- Applied to the soil or growing media, directed to the roots of plants
- A liquid feed of a compound fertiliser (e.g. Tomorite) may be applied to tomato plants growing in pots in a greenhouse, hanging baskets and pot plants
What is meant by foliar feed and when would you apply it?
- Application of fertiliser in a diluted form to the foliage of the plant
- Generally restricted to application of trace elements
- Works relatively quickly and can be used to correct nutrient deficiencies
- It is a wasteful method, as a lower percentage of the nutrients supplied actually enter the plant
- E.g. a foliar feed of Epsom salts may be applied to correct magnesium deficiency in the foliage of apple trees
Comparison of organic matter to fertilisers
OM bulky, F concentrated
OM low-nutrient content, F high
OM imprecise control, F precise control
OM slow effect, F quick effect except slow release
OM effective over long period, F effect may be quickly lost
OM improves soil structure, F no impact on soil structure
OM will contain pests and diseases, F no pests and diseases
Describe the construction of a compost heap.
(i) Accessibility of the site: positioned in a sheltered area away from wind, orientated away from heat e.g. south and west.
ii) Mixture of soft green (25–50%) and brown (woody) material
(iii) Avoid perennial weeds/seeds /diseased/cooked material
(iv) Material to be shredded to increase surface area
(v) Suitable materials include vegetable peelings, shredded prunings, herbaceous material etc.
vi) Constructed on bare soil, wooden sides, cover to keep excessive rain off, compost heap to be minimum size of 1m³, material to be layered inside the compost heap.
vii) Ensure that the compost heap does not dry out, water when required, turn the compost heap regularly by turning the outer edges into the centre to ensure that all the material can become hot
Name 2 organic fertilisers.
Fish, blood and bone
Bonemeal
Name 2 inorganic fertilisers.
Growmore:
Growmore has a ratio of 7:7:7 for these materials, but is actually 7% nitrogen, 3.1% phosphorus and 5.8% potassium, or 7:3.1:5.8. Therefore it is a high-nitrogen feed, rather than the ‘balanced’ fertiliser commonly assumed.
Ammonium sulphate:
For alkaline soils. The ammonium ion is released and forms a small amount of acid, lowering the pH balance of the soil, while contributing essential nitrogen for plant growth
What is meant by the term pH?
Expresses the amount of acidity or alkalinity in the soil in terms of hydrogen ions concentration. The more hydrogen ions the more acidic.
Why do plants need nitrogen?
- Vigorous vegetative growth and roots
- The dark green colour of plants (i.e. chlorophyll)
- Increases the plumpness of grains, the protein component of seeds and foliage and the succulence of crops such as lettuce
- Needed for proteins (make up the structural materials of all living matters) and enzymes (facilitate the vast array of biochemical reactions)
What are mobile nutrients?
Name them.
the transportability of substances within the plant
- nitrogen (N) in the form of nitrate
- phosphorus (P) in the form of phosphate
- potassium (K)
- magnesium (Mg)
- chlorine (Cl)
- zinc (Zn)
- molybdenum (Mo)
What are immobile nutrients?
not easily transportable within the plant
- calcium (Ca)
- sulphur (S)
- iron (Fe)
- boron (B)
- copper (Cu)
What are the symptoms of nitrogen deficiency?
- Chlorosis on older leaves first, generally beginning at the tip of the leaf progressing to the middle of the leaf
- Stunted appearance and thin, spindly stems
What are symptoms of too much nitrogen?
- ‘lodging’ with heavy rain and wind, where plants fall over due to excessive vegetative growth.
- May also delay plant maturity and cause plants to become more susceptible to disease and pests.
- Reduced flowers in ornamentals.
Why do plants need phosphorus?
- Plays a vital role in virtually every plant process that involves energy transfer. Essential to photosynthesis, nitrogen fixation, flowering, fruiting and maturation.
- Needed in meristematic tissue
- Root growth, esp at seedling stage
- Essential to seed formation and germination, this mineral is often found in large quantities in seed and fruit
- For creating ATP
What affects phosphorus availability?
- can be lost from the soil through erosion of soil particles and organic matter, and loss of soluble P in runoff from soils
- most soil phosphorous occurs as relatively insoluble minerals and organic matter in the soil
- the availability of these forms is very sensitive to soil pH
What are the symptoms of phosphorus deficiency?
• Stunted new growth
• Weak, poor root development
• Purple colouring, particularly in young plants; oldest leaves are affected first
Why do plants need potassium?
- Controls physiological processes: from photosynthesis, nitrogen fixation, starch formation, sugar translocation
- Osmotic regulator – critical in reducing water loss from leaf stomata and increasing uptake of water via the roots; controls water uptake and helps plants cope with environmental stresses such as drought, hardiness and disease
- Promotes flowering, fruiting and general hardiness
What are the symptoms of potassium deficiency?
- Yellow or purple (caused by a buildup of carbohydrates) leaf-tints with browning at the leaf edge
- Older leaves become scorched and curl before younger leaves
- Reduced shoot growth
- Poor flowering or fruiting, yields
- Shortages are more likely on light, sandy or chalky soils where potassium is easily washed away. Clay soils, by contrast, hold potassium within their structure.
What are main reasons why N, P and K needed?
Nitrogen:
- Healthy foliage
- Chlorophyll and ATP production
- Vegetative growth
Phosphorous:
- Development of flowers
- DNA/RNA synthesis
- Strong roots
Potassium:
- Hearty growth
- Synthesize proteins and carbohydrates
Why do plants need calcium?
- Integral part of plant cell walls – holds cell wall together after cell division
- Promotes proper plant-cell elongation and division (meristems) especially in root tips
- Protects cells against toxicities of other elements and diseases
Immobile
What are the symptoms of calcium deficiency?
• Localised tissue necrosis leads to stunted growth, die backorburns on leaves, curling of leaveswhich leads todeath of terminal buds and root tips
Immobile – so appears in growing parts/younger tissues –blossom end rot in melons & tomatoes (inadequate Ca for the cell walls of expanding fruits)
Why do plants need magnesium?
Symptoms of deficiency?
- Key component of chlorophyll, plays a critical role in photosynthesis
- Critical role in protein synthesis and activation of enzymes in energy metabolism
- For healthy leaves
Symptoms:
- Interveinal chlorosis on older leaves first
- Early leaf fall
- Common in tomatoes, apples, grape vines, raspberries, roses and rhododendrons
Why is pH 6.5 the most suitable pH for a wide range of plants in the UK?
Availability of nutrients is at its highest and soil organism activity is at its optimum at pH 6.5 to 6.8
E.g. Solanum tuberosum tolerates down to pH 4. 9 but celery needs to be above pH 6.3.
Vaccinium corybosum needs higher than pH 5.5. Ditto Rhododendron spp.
Why is pH important?
• Availability of nutrients to plants: at neutral pH nutrients can be exchanged between soil particles and soil water at a regular rate – making nutrients available to most plants; at higher or lower pH, nutrients can be ‘locked-up’ in soil particles, held in toxic amounts in the soil water or made so soluble that they are washed away. Each of these conditions will affect nutrient availability to plants and affect growth.
As a soil becomes progressively more alkaline, phosphorus and boron become insoluble; Fe, Zn, Cu and Mn become less available.
In acidic soils nutrients such as Ca, K, Mg and Cu become more soluble and are easily washed away. P and Mo become deficient, too, because they become insoluble. Al, Mn, Fe, Zn and H reach toxic levels.
- Activity of soil organisms: in acidic soils they become less active, slowing the rotting of organic matter resulting in fewer nutrients being released
- Soil structure: soils that have high CECs (clay) tend to have high concentrations of colloidal particles and a neutral to high pH
How does particle type affect CEC?
- Cat-ion Exchange Capacity affected by the amount of clay particles (-vely charged, hold on to nutrients tightly) vs sand (not so tightly bonded)
- Soils that have high CECs tend to have high concentrations of colloidal particles and a neutral to high pH
What is lime-induced chlorosis? How can you treat it?
- Occurs when ericaceous plants (calcifuges), such as camellias are grown in alkaline soil conditions
- Plants have difficulty absorbing iron and manganese from the soil if growing in an alkaline soil
- Symptoms appear as a yellowing of the leaves due to an iron and manganese deficiencies as a result of too much alkalinity
Treatment:
• Add chelated or sequestered fertilisers, which are organic compounds supplying iron and manganese in a form that the plant is able to take up
Benefits and limitations of lime?
Benefits:
- Raises pH and promotes the release of phosphorus and other nutrients needed for photosynthesis
- Promotes the activity of earthworms and nitrogen-fixing bacteria as well as the breakdown of organic material that releases N, P, sulphur
- Liming prevents the build-up of aluminum and manganese to toxic levels and corrects calcium and magnesium deficiencies
- Improves soil structure and less susceptible to compaction
- Can help reduce the acidity of run off which enters watercourses
Limitations:
- Can reduce the availability of Zn, Fe and boron if overused
- Requires regular applications
- Needs soil moisture to become active so timing of application is very important
- Liming products often unpleasant and difficult to handle
Benefits and limitations of sulphur?
Benefits:
- Will lower pH, eventually
- Can help reduce sodium levels
- Used by bacteria (as a source of energy) in the sulphur cycle. These bacteria make elemental sulphur available to plants as sulphates
Limitations:
- Takes many weeks/months to take effect
- Large quantities can affect phosphorous levels and repeated applications can lead to build up of aluminum
- Requires correct timing of application (not in winter and not when very wet) and when soil-moisture levels are adequate
- Sulphates can acidify soil water and this can run off into watercourses
Benefits and limitations of organic manure on pH?
- Most sources of organic matter are pH 6.5 to slightly alkaline and can help combat soil acidification (through buffering)
- Some organic matter can cause acidification such as composted needles, ericaceous compost
- FYM can mitigate against soil acidification
Examples of calcifuges?
- Camellia japonica*
- Rhododendron luteum*
- Vaccinium myrtillus*
- Erica tetralix*
- Pieris japonica*
- Hamamelis x intermedia*
Examples of alkaline plants?
- Buddleja davidii*
- Brassica oleracea*
- Dianthus barbatus*
- Acanthus mollis*
- Potentilla fruticosa*
- Scabiosa caucasia*
- Euonymus europaeus*
- Viburnum lantana*
Examples of neutral plants?
- Campanula trachelium*
- Potentilla fruticosa*
- Acanthus mollis*
How is nutrient availability affected by pH in soils?
pH of 6.5 needed for big 3 to all be available
Acidic soils:
- Al and Mn can become more available and more toxic to plants
- Ca, P and Mg are less available
Alkaline soils:
- Fe, Mn, P and most micronutrients become less available
State whether effect of these materials acid, neutral or alkaline?
Peat, Coir, Green manure, Composted bracken, Wood ash, Ammonium sulphate
Peat – Acidic
Coir – Neutral
Green manure – Acid
Composted bracken – Neutral
Wood ash – Alkaline
Ammonium sulphate – Acid
Example of base dressing?
Organic:
Hoof and horn (nutrient release slower than with blood, so good for organic crops) 70–270g/m2
Growmore
Bone meal
- 70–200g/m2 for long-standing and perennial plants
- Fairly slow acting and need to apply well in advance of planting
- Provides about 5% of N, 20–25% of P
Inorganic:
Ammonium sulphate
Example of a top dressing?
Organic:
Hoof and horn (nutrient release slower than with blood, so good for organic crops) – depends on how coarse; provides 7–15% of nitrogen (N) and lesser amounts of phosphorus (P) and other elements.
Dried blood 17–34g/m2 – faster acting (nutrients are released in the soil by bacterial action within 7–10 days); provides about 7–14% of N and lesser amounts of P.
Inorganic:
- Ammonium sulphate used as a top dressing at the rate of 17–34g/m2
- Superphophate (also as base dressing)
- Triple superphosphate (also base)
Benefits and limitations of organic fertilisers?
Benefits:
- Generally safe to use.
- An overdose does not generally cause a too highly concentrated soil solution.
- Provide a steady supply of nutrients of over a long period so provide long-standing and perennial crops with a supply of available plant foods throughout their period of growth.
- They do not react so readily with other other fertilisers.
Limitations:
- Some are slow acting and need to be applied well in advance of planting so that decomposition can occur and nutrients are available to plants.
- The amounts of nutrients may vary considerably.
What are the advantages of top dressing?
Helps reduce the need for frequent fertilizing
- Helps soil become richer in terms of organic matter
- Helps soil stay airy and light, fighting the natural tendency of soil to grow heavier over the years
- Enhances soil structure; soil that is well structured has superior water-retention properties and is a more fertile environment for plants
- When you add soil mix or compost, the ground grows more porous; this maximizes local gaseous exchanges that promote proper root growth
Examples of inorganic fertilisers?
Growmore
Miracle-Gro
Phostrogen
Sulphate of ammonia
Sulphate of potash
Superphosphate
Tomorite
What are the benefits and limitations of inorganic fertilisers?
Benefits:
- Precise amounts of nutrients can be supplied.
- As they are often more concentrated only small amounts need to be stored and supplied.
Limitations:
- Many react with other fertilisers so care requiring if combining them.
- The application of one inorganic fertiliser may cause a deficiency in another.
- Obvious environmental concerns so as run-off into watercourses of nitrates, sulphates and phosphates.
- Care required as N may be lost by volatilization if left on the soil surface.
Environmental issues?
- Excess fertilisers can be leached out from the soil by rainwater. This can then enter watercourses and cause algal blooms.
- The breakdown of the algae by microorganisms causes oxygen to be used up in the water and this causes aquatic species to die. Known as eutrophication and results in a decrease in biodiversity.
- Environmentally sensitive periods for application, e.g. , if a slow-release organic fertilizer is applied in late spring or early summer, a leguminous cover crop would need to be sown in the autumn to absorb excess nitrate being released
