Managing Soil Fertility: Targets to maximise...
Transcript of Managing Soil Fertility: Targets to maximise...
Managing Soil Fertility:
Targets to maximise production
Dr David P. Wall Teagasc, Johnstown Castle, Co Wexford
David Wall_Soil Fertility Management_IDIA 2017 2
Outline
Soil fertility trends on dairy farms
5 Steps to soil fertility management
• Soil Testing
• Soil pH and Lime
• Determine P & K requirements
• Best use of Organic manures
• Apply a balanced fertilizer programed
Soil Fertility and Productivity Targets
David Wall_Soil Fertility Management_IDIA 2017 3
National Soil Fertility trends
Soils Data Base maintained at Teagasc
Johnstown Castle
2015
~ 36,000 samples submitted through Teagasc for soil analysis
Samples submitted for analysis from each county in Ireland
Dairy: National soil pH trend
n = 113,606 soil samples (average 12,622 samples/annum) Wall et al. 2015
Pro
po
rtio
n o
f so
il sa
mp
les
in e
ach
Ind
ex
27% 22% 19% 25% 23% 20%
14% 19% 20%
28% 28% 29%
29% 26% 26%
26% 25% 24%
19% 20% 20%
21% 19% 21%
22% 20% 19%
13% 15% 15%
13% 15% 17%
19% 17% 17%
14% 16% 17% 12% 17% 16% 18% 18% 19%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
20
07
20
08
20
09
20
10
20
11
20
12
20
13
20
14
20
15
>6.5 6.2-6.5 5.9-6.2 5.5-5.9 <5.5
David Wall_Soil Fertility Management_IDIA 2017 5
0
500
1000
1500
20001
97
01
97
11
97
21
97
31
97
41
97
51
97
61
97
71
97
81
97
91
98
01
98
11
98
21
98
31
98
41
98
51
98
61
98
71
98
81
98
91
99
01
99
11
99
21
99
31
99
41
99
51
99
61
99
71
99
81
99
92
00
02
00
12
00
22
00
32
00
42
00
52
00
62
00
72
00
82
00
92
01
02
01
12
01
22
01
32
01
4To
nn
ag
e o
f L
ime (
'000 t
/yr)
Year
Lime usage 1970 -2014
David Wall_Soil Fertility Management_IDIA 2017 6
Phosphorus fertility
declining high status soils
Low proportion of soils at target index
Large proportion with sub-optimum P
Potassium fertility
Majority soils with sub-optium K
Steady decline in soil K fertility
over last decade
Soil P & K fertility status and trends
David Wall_Soil Fertility Management_IDIA 2017 7
N, P and K use between 1990 and 2011 relative to 1990 (N= 379,000 kg ,P= 65,000 kg , K=158,000 kg)
N
K
P
High fertilizer N allowance and most restrictive P allowance in Europe
P = 20,000 kg
K = 52,000 kg
David Wall_Soil Fertility Management_IDIA 2017 8
All farms ~153,500 soil samples
9 10 11 11 19 22
29 25 25 28
32%
26 24 23 24
27 28
29
27 27 29
28% 28 31 30 29
27
27
23
25 25
23 23%
36 35 37 36 28
22 19
23 23 19 17%
0
10
20
30
40
50
60
70
80
90
100
2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
Perc
en
tag
e o
f sam
ple
s i
n e
ach
P i
nd
ex
Index 4(High)
Index 3(Optimum)
Index 2(Low)
Index 1(V.Low)
Reducing soil P loss
risk
Soil P Fertility trends – Dairy
Lower N fertiliser
and slurry nutrient
efficiency
David Wall_Soil Fertility Management_IDIA 2017 9
Soils with Optimum Soil Fertility
Optimum 10%
90%
Good Overall Fertility : Soil pH > 6.2; Soil P and K Index ≥ 3
David Wall_Soil Fertility Management_IDIA 2017 10
What quantities of nutrients are
required? Nutrient off-take from the grazing platform
Milk (18,000 litres/ha)
+ 3Cows & Calves LW/ha
110 kg N
20 kg P
31 kg K
5 kg S
Nutrients required
For 12 t DM/ha
50 kg
EC Fertiliser
?
Losses (N, S, K , P)
Lock-up(P, N, S,
K)
David Wall_Soil Fertility Management_IDIA 2017 11
What quantities of nutrients are
required?
Losses (N, S, K , P)
Lock-up(P, N, S,
K)
50 kg
EC Fertiliser
N – 250 kg/ha
P – 25 kg/ha
K – 45 kg/ha
S – 20 kg/ha
Highly Stocked Grazing
Block
Typical Maintenance
David Wall_Soil Fertility Management_IDIA 2017 12
Steps to Soil Fertility Management
Index Description
1 Very Low
2 Low
3 Target
4 High
David Wall_Soil Fertility Management_IDIA 2017 13
Soil Testing – Cost / Benefit
~ 10% of soils are optimised for P, K & lime
• If no soil test and assume Index 3, then you are likely to be wrong in 90% of fields !!
Cost
• Consider relative to fertilizer cost?
» 1 sample = 4 ha for 5 years @ €25
» €1.25 /ha/yr (50c per acre)
» 1 kg of P = €2 !!!
= € 300-500 / tonne ???
N P K Fertilizer
David Wall_Soil Fertility Management_IDIA 2017 14
Soil testing – Why & How ?
How ?
• Sample Area
• Minimum 20 cores per sample
• Full 10 cm depth
When ?
• Late Autumn / Early Spring ideal
» Results ready for fertiliser planning for the coming year
David Wall_Soil Fertility Management_IDIA 2017 15
Steps to Soil Fertility Management
David Wall_Soil Fertility Management_IDIA 2017 16
Soil pH and Liming
Optimum pH for grassland = 6.2 - 6.3 » Maximum nutrient release from soils
» Soil biological activity
67 % of grassland soil < 6.2
Response to fertiliser N, P and K on acid soils ????
6.5 4.5 7.0 5.0 7.5 5.5 6.0
P
N
K
• Soil P reserve less
available
• Fertilisers less
available
David Wall_Soil Fertility Management_IDIA 2017 17
Effect of soil pH on P Availability
` 3 4 5 6 7 8 9 Soil pH
Acidic Soils Alkaline Soils
Ph
osp
ho
rus F
ixati
on
High
Med
Low
Fixation by
Iron &
Aluminium
Fixation
by
Calcium
Plant
Available
P
D.P. Wall, 2015
David Wall_Soil Fertility Management_IDIA 2017 18
Effect of P and Lime of soil P availability
Sheil, Wall & Lalor,
2015, FAI
Wall, D.P. et al. Teagasc, Soil Fertility Conference, 2015
David Wall_Soil Fertility Management_IDIA 2017 19
Average response across 2 sites
Effect of P and Lime of grass yield
Average soil pH: 5.2 6.4 5.2 6.4
D.P. Wall et al., 2015
Wall, D.P. et al. Teagasc, Soil Fertility Conference, 2015
David Wall_Soil Fertility Management_IDIA 2017 20
Lime in grassland
1 ha
Up to 250-625 kg/ha/yr of lime in
drainage
100 kg
=
180-220
kg lime
N
fertiliser
Offtake 1 bullock
25 kg of Lime
1000 litres milk
3 kg of Lime
5 t/ha silage DM
75 kg of Lime
Grassland Example
150 kg/ha N – 300 kg
10,000 litres milk – 30 kg
Lime loss in drainage – 250-625 kg
Total lime required –
580 – 955 kg/ha/yr
1-2 ton/acre every 5 years
David Wall_Soil Fertility Management_IDIA 2017 21
Lime requirements
Advice is to apply lime in a 3-5 year cycle
• Grassland typically requires between 0.5 - 1 t/ha/yr
• Target soil pH: Mineral soils 6.3, Peat soil 5.5
Exceptions
• High Mo soils and grassland don’t exceed pH 6.2
» Lime requirements reduced by 5 t/ha
• Where advice is > 7.5 t/ha
» Split application
» 7.5 t/ha now
» Remainder after 2 years
» Precaution to reduce risk of trace element problems
David Wall_Soil Fertility Management_IDIA 2017 22
Steps to Soil Fertility Management
Index Description
1 Very Low
2 Low
3 Target
4 High
David Wall_Soil Fertility Management_IDIA 2017 23
Interpreting soil test results - P & K
Convert test result into soil Index (P & K grassland index below)
Target = All soils in Index 3 for P and K !
• Only ~ 25% at present
Soil Index Description Soil test P
(mg L-1)
Soil test K
(mg L-1)
1 Very low 0 – 3.0 0 – 50
2 Low 3.1 – 5.0 51 – 100
3 Medium 5.1 – 8.0 101 – 150
4 High ≥ 8.1 ≥ 151
Soil Index Description Soil test P
(mg L-1)
Soil test K
(mg L-1)
1 Very low 0 – 3.0 0 – 50
2 Low 3.1 – 5.0 51 – 100
3 Medium 5.1 – 8.0 101 – 150
4 High ≥ 8.1 ≥ 151
David Wall_Soil Fertility Management_IDIA 2017 24
Maintenance P and K advice Grazed Swards Silage Swards
Stocking Rate (kg/ha Org N) Soil P
Index < 130 131-170 171-210 >210 Cut Once
Cut
Twice
1 30 34 39 43 +20 +30
2 20 24 29 33 +20 +30
3 10 14 19 23 +20 +30
4 0 0 0 0 0 0
Grazed Swards Silage Swards
Stocking Rate (kg/ha Org N) Soil K
Index < 130 131-170 171-210 >210 Cut Once
Cut
Twice
1 85 90 95 100 +120 +155
2 55 60 65 70 +120 +155
3 25 30 35 40 +120 +155
4 0 0 0 0 0 0
David Wall_Soil Fertility Management_IDIA 2017 25
Soil P and K build up - Grassland
P K
Index 2
10 kg/ha
(8 units/acre)
30 kg/ha
(24 units/acre)
Index 1
20 kg/ha
(16 units/acre)
60 kg/ha
(48 units/acre)
16% P
25 kg
16% P
50 kg
Muriate
50% K
25 kg
Muriate
50% K
50 kg
Apply build up +
maintenance in
Index 1 and 2
Apply for 5 years
or until soil test
shows increase
David Wall_Soil Fertility Management_IDIA 2017 26
Steps to Soil Fertility Management
27 Lalor et al. 2013. IFS Conference, Cambridge. 6-7 Dec, 2012.
Contribution to Slurry Value
Cattle Slurry
N
12%
P
19%
K
69%
Majority of the value is in P
and K
• Aim to get best use of both P
and K in slurry
• Timing or method
» No effect on P and K
» Big effect on N
David Wall_Soil Fertility Management_IDIA 2017 28
Slurry Value 1000 gallons = ??
50 kg
N P K
4 - 0.7 - 5
50 kg
N P K
6 - 5 - 38
50 kg
N P K
3 - 5 - 38
Soiled Water
All Year
Cattle Slurry (Splash plate)
Spring Summer
50 kg
N P K
19 - 7 - 20
Pig Slurry
Trailing Shoe
+ 3 units N
/ 1000 gallons
In spring or
summer
50 kg
N P K
3 - 2.5 - 12
FYM (1 ton)
5 / 1000 gals 24 / 1000 gals 26 / 1000 gals
28 / 1000 gals 10 / ton
Beware of
Average Values
Highly Variable
David Wall_Soil Fertility Management_IDIA 2017 29
Decisions with slurry
1. Where to spread
» P & K requirements
» Target fields with:
low soil P and K
High requirements (e.g. silage)
2. When to spread
» Maximise N availability
» Weather as important as
season, but spring generally
best
» Trailing shoe / band spreader
will also increase N value
David Wall_Soil Fertility Management_IDIA 2017 30
Steps to Soil Fertility Management
David Wall_Soil Fertility Management_IDIA 2017 31
Nutrient Balance – What is the Weakest
Link ?
Nutrient in shortest supply limits determines yield
• Especially true with P and K
Fertilizer Planning
• Soil tests & Cropping
• Slurry & fertilizers
» Straight K
» N-P products
» N-K products
» Sulphur and micro nutrients
N P K Fertilizer
N P Fertilizer
K Fertilizer
David Wall_Soil Fertility Management_IDIA 2017 32
Cost of lost production at Index 1 & 2
Example
• Dairy – 2 cows / ha
• Maintenance advice (grazing: Index 3 ) = 13 kg/ha P & 35 kg/ha K
• Cost of maintenance P & K = €60 /ha/yr
Production loss in Index 1 vs. Index 3
• Approximately 2.0 t/ha/yr of grass DM (range 1-5 t/ha)
• Worth ~ €360 /ha/yr
Additional P and K for build up = 20 kg/ha P & 60 kg/ha K
• Additional Cost = €90 /ha/yr until soil P / K increases
• Long-term investment – benefits of increasing to Index 3
• Return on Investment 4:1 (€ grass production : € soil fertility)
Soil pH needs to be
right as well !
David Wall_Soil Fertility Management_IDIA 2017 33
Urea or Stabilised Urea
Why look at it now?
Cost & yield Urea-N costs less
than CAN-N: 26%
less (CSO, 2014)
Is there a yield
penalty?
Internationally urea
is more available
than CAN
GHG • Ag. approx. 1/3
national emissions
• Committed to reduce by 20% by 2020
• N addition causes N2O loss
• Smart solutions?
Ammonia (NH3)
• Ag. accounts for c. 98.5% of national emissions
• Committed to reduce by 30% by 2030
• Urea looses NH3!
Nitrogen fertiliser selection
David Wall_Soil Fertility Management_IDIA 2017 34
Nitrogen fertiliser selection
David Wall_Soil Fertility Management_IDIA 2017 35
Soil Fertility Management Targets Have soil analysis for whole farm
Soil pH between 6 and 6.5 in all fields
• Note: target pH 5.5 for peat soils
P and K Index 3 in all fields
• Index 4 is a resource Exploit it
• Index 1 & 2 should be increased to Index 3
Optimise slurry first – then top up with fertilizer as required
Nutrient inputs in proper balance
• Fertilizer planning is key
• Increase farm sustainability with N fertiliser source selection