Cereals Lecture Week 7 2024 Crop Nutrition Part 1 P and K

Question 1

What are the major elements in cereal crops? (4)

Answer 1

N, P, K, S

Question 2

What are the minor elements in cereal crops? (4)

Answer 2

Zn, Cu, Mn, Mg B

Question 3

Factors in Crop Production that all feed into yield quality:

Answer 3

Rotation

Climatic
factors

Soil
factors

Nutrient
supply

Husbandry

Variety

Disease,

Pest,

Weed

control

Growth
Regulation

Harvest
Technique

Post-
harvest
handling

Question 4

In modern
intensive crop
production
systems the main
source of key
nutrients for crop
growth is from…

Answer 4

soluble synthetic
fertilisers

Question 5

Crop Nutrition

1-Whats the aim in crop production:

2- Is crops nutrient value all the same or does it differ?

Answer 5

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

Question 6

1- The two biggest sources of GHG
from agriculture are :

3- Together what % do they make up of global GHG emissions?

Answer 6

1- The release of
N20 from soils

2- The release of
Methane from livestock and manure

3- 5%

Question 7

In crop production what is
the most important part of the
carbon footprint?

Answer 7

Nitrogen fertiliser

Question 8

% of GHG emissions in
Crop Production
2 Main segments:

Answer 8

1-Fertiliser-
Induced
Emissions 33%

2-Fertiliser
Production 50%

Question 9

Tillage farms emitted how much
tonne/farm GHG equivalent in
2017 but only what% of this was
from crop production?

Answer 9

125 tonne/farm

23%

Question 10

What% of the Ammonia emitted on
tillage farms was from non-
tillage activity (cattle)

Answer 10

83%

Question 11

N Use Efficiency on tillage
farms was what%

Answer 11

70%

Question 12

P Use Efficiency was what% on
tillage farms

Answer 12

91%

Question 13

Example of Carbon Footprints in Crops
Based on per tonne of production

1- Highest - lowest of 3

Answer 13

W Oilseed Rape (500 kg CO2e/t)

Winter Wheat (300 kg CO2e/t)

Sp Malting Barley (220 kg CO2e/t)

Question 14

Fate Of Applied Fertiliser N in Cereals
4 things can happen:

Answer 14

N immobilised
into the Soil
OM%
31%

Denitrification
4%

Leaching
6%

Crop Uptake
59%

Question 15

Up to what% of the applied fertiliser N is not taken up by the
cereal crop in the year of application

Answer 15

40%

Question 16

Major Elements (4)

Answer 16

Nitrogen - N
Phosporus - P
Potassium - K
Sulphur - S

Question 17

Minor Elements (6)

Answer 17

Zinc Zn
Copper Cu
Manganese Mn Magnesium Mg
Boron B
Sodium Na

Question 18

Sulphur – ‘major’ / minor nutrient:

• When is it applied?
• how much kg/ha?

-What does it have a role as?

Answer 18

– 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

Question 19

Managanse

• What is its requirment linked to?

-High PH soils have…

-What happens in Oats?

Answer 19

-requirement is linked to soil pH

– High Ph soils have higher Mn reqt, also varies with crop

– ‘grey speck’ in Oats

Question 20

Zinc

-Whats it linked to?

-What sort of resonse does it get from foliar Zn application?

Answer 20

– linked to soil type and also soil Zn levels

– High yield response to foliar Zn application when a severe deficiency

Question 21

Copper

What is it most noticeable in?

Answer 21

High soil OM/Peat soils

Question 22

Magnesium

-Whats it linked to?

-When can there be a deficiency?

-What crop is most prone?

Answer 22

• linked to weather conditions

– Transient deficiency in dry spring weather

– Barley most prone , also late-season benefits (Epson salts)

Question 23

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?

Answer 23

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

Question 24

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?

Answer 24

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

Question 25

P and K fertilisation
The Index System (1-4)

P index for 1,2,3,4

Answer 25

1- 0-3

2- 3.1-6

3- 6.1-10

4- Above 10

mg/l

Question 26

P and K fertilisation
The Index System (1-4)

K index for 1,2,3,4

Answer 26

1- 0-50

2- 51-100

3- 101-150

4- above 150

mg/l

Question 27

P and K fertilisation
What the Index levels indicate:

Index 1

Index 2

Index 3

Index 4

Answer 27

• 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

Question 28

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?

Answer 28

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

Question 29

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

Answer 29

85%

50%

Question 30

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

Answer 30

Soil Index

1- 35

2- 30

3- 20

4- nil

Question 31

P (kg/ha) recommended for
Cereals (Wheat and Barley)
based on the index system Teagasc

Soil Index

1

2

3

4

Straw removed

Answer 31

Soil Index

1- 45

2- 35

3- 25

4-0

Question 32

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

Answer 32

Soil index

1- 65- 75

2- 50-65

3- 35-50

4- nil

Question 33

K (kg/ha) recommended for
Cereals (Wheat and Barley)
based on the index system Teagasc

Soil index

1

2

3

4

Straw Removed

Answer 33

Soil index

1- 110-140

2- 100-125

3- 85-110

4- 0

Question 34

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?

Answer 34

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

Question 35

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

Answer 35

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