Cereals Lecture Week 7 2024 Crop Nutrition Part 1 P and K Flashcards
What are the major elements in cereal crops? (4)
N, P, K, S
What are the minor elements in cereal crops? (4)
Zn, Cu, Mn, Mg B
Factors in Crop Production that all feed into yield quality:
Rotation
Climatic
factors
Soil
factors
Nutrient
supply
Husbandry
Variety
Disease,
Pest,
Weed
control
Growth
Regulation
Harvest
Technique
Post-
harvest
handling
In modern
intensive crop
production
systems the main
source of key
nutrients for crop
growth is from…
soluble synthetic
fertilisers
Crop Nutrition
1-Whats the aim in crop production:
2- Is crops nutrient value all the same or does it differ?
1* the aim in crop production is to have the
key nutrients availiable to the crop that
will optimise production and at the same
time will not cause pollution
2* crops will differ in their nutrient
requirements e.g. high P requirement for
root crops
1- The two biggest sources of GHG
from agriculture are :
3- Together what % do they make up of global GHG emissions?
1- The release of
N20 from soils
2- The release of
Methane from livestock and manure
3- 5%
In crop production what is
the most important part of the
carbon footprint?
Nitrogen fertiliser
% of GHG emissions in
Crop Production
2 Main segments:
1-Fertiliser-
Induced
Emissions 33%
2-Fertiliser
Production 50%
Tillage farms emitted how much
tonne/farm GHG equivalent in
2017 but only what% of this was
from crop production?
125 tonne/farm
23%
What% of the Ammonia emitted on
tillage farms was from non-
tillage activity (cattle)
83%
N Use Efficiency on tillage
farms was what%
70%
P Use Efficiency was what% on
tillage farms
91%
Example of Carbon Footprints in Crops
Based on per tonne of production
1- Highest - lowest of 3
W Oilseed Rape (500 kg CO2e/t)
Winter Wheat (300 kg CO2e/t)
Sp Malting Barley (220 kg CO2e/t)
Fate Of Applied Fertiliser N in Cereals
4 things can happen:
N immobilised
into the Soil
OM%
31%
Denitrification
4%
Leaching
6%
Crop Uptake
59%
Up to what% of the applied fertiliser N is not taken up by the
cereal crop in the year of application
40%
Major Elements (4)
Nitrogen - N
Phosporus - P
Potassium - K
Sulphur - S
Minor Elements (6)
Zinc Zn
Copper Cu
Manganese Mn Magnesium Mg
Boron B
Sodium Na
Sulphur – ‘major’ / minor nutrient:
- When is it applied?
- how much kg/ha?
-What does it have a role as?
– An important element and routinely applied in recent decades
– 5-10 (20) kg/ha
– Also a role as a foliar applied nutrient to reduce fungal disease
Managanse
- What is its requirment linked to?
-High PH soils have…
-What happens in Oats?
-requirement is linked to soil pH
– High Ph soils have higher Mn reqt, also varies with crop
– ‘grey speck’ in Oats
Zinc
-Whats it linked to?
-What sort of resonse does it get from foliar Zn application?
– linked to soil type and also soil Zn levels
– High yield response to foliar Zn application when a severe deficiency
Copper
What is it most noticeable in?
High soil OM/Peat soils
Magnesium
-Whats it linked to?
-When can there be a deficiency?
-What crop is most prone?
- linked to weather conditions
– Transient deficiency in dry spring weather
– Barley most prone , also late-season benefits (Epson salts)
P and K fertilisation
-Whats the index system based on?
-What’s the aim of crop production?
-Is there recent evidence of some sort of leaching?
1-* The index system based on soil testing, nutrient balance calculations
2-* the aim in crop production is to have P and K
availiable to the crop that will optimise
production and at the same time will not cause
pollution
3-* there is recent evidence of P leaching from soils
– from very light free draining soils
– on soils which have been artificially (tile)
drained
1- What does soil testing give the results of?
2- What are the P and K indexes correlated to?
3- In the soil test, the water and readily soluble reserves are measured using what?
4- In Ireland, what test do we use?
In Britain what test do they use?
1* In soil testing as well as giving the soil test
result in mg/kg the result for each nutrient is
shown using an index on a scale of 1 to 4
2* the P and K index’s are correlated with crop
response
3* in the soil test the water- and readily-soluble
reserves are measured using extraction process
4– in Ireland Teagasc use Morgans P and K tests
– in Britain Olsens P and exchangable K tests
P and K fertilisation
The Index System (1-4)
P index for 1,2,3,4
1- 0-3
2- 3.1-6
3- 6.1-10
4- Above 10
mg/l
P and K fertilisation
The Index System (1-4)
K index for 1,2,3,4
1- 0-50
2- 51-100
3- 101-150
4- above 150
mg/l
P and K fertilisation
What the Index levels indicate:
Index 1
Index 2
Index 3
Index 4
- Index 1. - nutrient response definite
- Index 2. - nutrient response likely
- Index 3. - nutrient response unlikely except for
root crops but maintenance dressing should be
used - Index 4. - nutrient levels adequate,
maintenance dressings not necessary at present
except for root crops
Management of P and K use in
practice - using nutrient balances:
1- What is the nutrient balance?
2- Is it easy or hard to determine the N balance?
3- What can be done so that fertilization can be carried out over a rotation?
1* the nutrient balance is simply the amount of
the nutrient applied minus the amount which is
removed in the crop at harvest
2* the nutrient balance is easily determined
provided fertiliser applications are known and
the harvest crop yields are known
3* data can be built up so that the fertilisation can
be carried out over a rotation i.e. as a schedule
What% of the P is in the grain : straw removal is not impt
What % of more of the K can be in the straw at harvest
85%
50%
P (kg/ha) recommended for
Cereals (Wheat and Barley)
based on the index system Teagasc
Soil Index
1
2
3
4
Straw Ploughed in or burned
Soil Index
1- 35
2- 30
3- 20
4- nil
P (kg/ha) recommended for
Cereals (Wheat and Barley)
based on the index system Teagasc
Soil Index
1
2
3
4
Straw removed
Soil Index
1- 45
2- 35
3- 25
4-0
K (kg/ha) recommended for
Cereals (Wheat and Barley)
based on the index system Teagasc
Soil index
1
2
3
4
Straw Ploughed in or burned
Soil index
1- 65- 75
2- 50-65
3- 35-50
4- nil
K (kg/ha) recommended for
Cereals (Wheat and Barley)
based on the index system Teagasc
Soil index
1
2
3
4
Straw Removed
Soil index
1- 110-140
2- 100-125
3- 85-110
4- 0
P Experiment Conclusions:
1- What does P’s recommendation depend on?
2- What other factors are important?
3- What evidence do we have in terms of levels?
4- What would be useful if developed?
1* P recommendations should not depend on soil
indices alone
2* Other factors such as soil type are important - this
suggests that there is a critical P level below which
crop yields are impaired but that this level varies
with the soil type
3* there is evidence that these critical levels vary for
wheat and barley
4* development of a foliar P test would be useful but it
is difficult to establish optimum levels for different
stages of growth
K : Rothamsted Long Term Experiments
1- a soil which had received no K for 90 years was still
capable of yielding *** of winter wheat
2- this yield was only what% less than that on a soil which
had received K for each year in this period
3- K fertilisation practices overtime are in practical terms
dictated by what?
4- Is there clear scope for managing K fertilisation
practices to minimise costs without sacrificing yield in
cereals
1* a soil which had received no K for 90 years was still
capable of yielding 9.2 t/ha of winter wheat
2* this yield was only 15% less than that on a soil which
had received K for each year in this period
3* K fertilisation practices overtime are in practical terms
dictated by the cropping sequence, high levels need to
be maintained for root crops
4* there is clear scope for managing K fertilisation
practices to minimise costs without sacraficing yield in
cereals
