how much phosphorus does it take to make lake erie green? · pdf filehow much phosphorus does...
Post on 06-Mar-2018
222 Views
Preview:
TRANSCRIPT
How much phosphorus does it take to make Lake Erie green? Dr. Ivan O’Halloran, Associate Professor, University of Guelph, Ridgetown Campus
Jake Munroe, Soil Fertility Specialist, OMAFRA
2
3
Overview
• What causes an algal bloom?
• Why is Lake Erie particularly vulnerable?
• How the situation has changed from blooms of the past
• Phosphorus movement off agricultural land
• Ontario research: phosphorus and water quality
• Top tips for keeping phosphorus on your land and out of the water
4
What Causes an Algal Bloom?
• All living organisms require phosphorus (P)
• P is commonly the least abundant macronutrient and the first to limit biological productivity
• Excess P in lakes can stimulate excessive growth of algae
• Warm temperatures and lots of sunlight provide optimal conditions
5
Dissolved P and Lake Erie
6 • Total P entering Lake Erie has decreased since 1970s • Amount of dissolved P entering Lake Erie is much
higher than what it was in mid-1990s
Some Important Terms
• Dissolved Reactive Phosphorus (DRP)
• The portion of dissolved phosphorus that is bio-available
• Soil Test Phosphorus (STP)
• Soil test level for crop available phosphorus
• Point Source (PS) vs. Non-Point Source (NPS)
7
Lake Erie Isn’t Alone
8
Lake Winnipeg
Lake Winnipeg
9
10
Caspian Sea
11
12
Why is Lake Erie Vulnerable?
• Of the Great Lakes, Lake Erie is the:
• Smallest in volume
• Shallowest
• Warmest
• Watershed has a high population concentration
• Western basin is particularly shallow
13
14
Shallow Western Basin
15
Priority Watersheds
16
Lake Erie’s Phosphorus History
NPS
17
Current Target 11,000 tonnes
Why Have Blooms Returned?
Higher Percentage of
Dissolved P
• Reasons are not understood
Changing Land Use
• Increased P discharges from urban and agricultural landscapes
Residual P
Re-suspension of P from stream and lake
sediments
Aquatic Invasive Species
• Changes to water clarity and nutrient flows caused by Zebra and Quagga Mussels
Changing Climate
• Increased frequency of severe storms
• Increased temperatures
• Longer growing seasons
Algal Blooms
18
Ontario’s Contribution
•But this is
based only on contribution to Lake Erie directly
19
By Major Jurisdiction
Source: Ohio EPA, April 2010 (Ohio Lake Erie Phosphorus Task Force Final Report)
20
Rough Estimates of Ontario’s Contribution • Lake Huron ~1000 T/yr
• Assume 50% from Ontario 500 T/yr
• Lake St. Clair - Detroit River ~ 1,000 T/yr (?)
• Detroit ~500 T/yr
• Thames River ~350 T/yr
• Rest of watershed ~150 T/yr
• ~ 25% land area of watershed is in Ontario so assume we have 25% of the P ~28 T/yr
• The green numbers total to 878 T/yr ~9.8% of the load
• Ontario’s total P loading around 15-18%
21
How much does this mean from the field • Assume all Ontario P load comes from Lake Erie –
Lake St. Clair watershed 1,820,118 ha farmland • Ontario owns ~ 16% or 1600 T/yr of total P load
• NPS is ~ 60% of total 1188 T/yr
• What % of the NPS comes from farmland? • 10% 119 T/year 0.065 kg/ha
• 30% 356 T/year 0.196 kg/ha
• 50% 594 T/year 0.326 kg/ha
• 75% 891 T/year 0.490 kg/ha
• 100% 1188 T/year 0.653 kg/ha
22
0.06 -0.6 lbs/acre
350 T/yr
What these losses mean based on land area
23
CANADA TP lbs/acre
US TP lbs/acre
Thames 0.57 Maumee 1.0
Grand 0.41 Sandusky 1.26
Ontario 0.60 Honey Creek
1.15
Cuyahoga 1.52
Grand 0.69 Assuming all
P comes from crop
land
“The FLAW of Averages”
24
Why does P go from here
25
to here?
Requirements for P Movement
• Source of P
• Manures, fertilizers, NASM, crop residues, soil…………
• Driver
• Water movement (hydrology)
• Source x Driver =
• When P moves
• How much P moves
• What forms of P moves 26
1. Seasonal Distribution of Precipitation 2. Year-to-Year Variability of Precipitation/Seasonal Distribution
2012
2013
2014
Winter JFM Spring AMJ Summer JAS Fall OND
196
457
351
463
258
160
224
303
171
838 mm
1574 mm
869 mm
186
272 240
195
399
273
125 195
116
122
321
174 236
68
217
631 mm
1130 mm
680 mm
345 345
243 133
1066 mm
Year Maitland Thames Essex
Hydrology - Precipitation
27
Hydrology – Runoff (Surface & Tile)
Year Maitland Thames Essex
2012
2013
2014
Winter JFM Spring AMJ Summer JAS Fall OND
148
222 183
68 75
25
43 67
14 50
167 mm
596 mm
391 mm
80 35
276
18
70 6
56
155
126
154
59
57
42 40
34
94 mm
547 mm
186 mm 166 mm
28
Tile Drainage Effects on Runoff (Maitland Site Example)
(1574 mm precipitation)
(869 mm precipitation)
Surface Runoff by Season
2013 2014
Tile Runoff by Season
Annual Runoff (596 mm )
Surface Tile
(391 mm )
472
125
145
246
Tile Drainage Effects on Runoff (Thames Site Example)
(1130 mm
precipitation)
(680 mm precipitation)
Surface Runoff by Season
2013 2014
Tile Runoff by Season
Annual Runoff (547 mm )
Surface Tile
(186 mm )
486
60
16
170
RELATIVE CONTRIBUTION OF TILE AND SURFACE RUNOFF
TO ANNUAL P LOAD (MAITLAND SITE: MAY 2012 – APR 2013)
General Conclusions Surface – not dominant pathway for water movement (~22%) but accounts for: 81% DRP loss 50% total P loss
Surface Tile
Source: C. Van Esbroeck – Thesis
Total Runoff 375 mm
DRP 0.096 kg /ha
TP 0.371 kg/ha
294
81
.018
.078
.185 .186
Surface Tile
Total Runoff 276 mm
DRP 0.028 kg /ha
TP 0.267 kg /ha
239
37
.017
.011
.077
.19
RELATIVE CONTRIBUTION OF TILE AND SURFACE RUNOFF
TO ANNUAL P LOAD (THAMES SITE MAY 2012 – APR 2013)
Source: C. Van Esbroeck – Thesis
General Conclusions Surface – ~ 13% of water movement and accounts for: ~ 39% DRP loss ~ 28% total P loss Tile can also be a significant pathway but lower P concentration than runoff
P CONCENTRATIONS IN TILE AND SURFACE
RUNOFF
(a) DRP
(b) TP
0.00
0.02
0.04
0.06
0.08
0.10
0.12
Maitland Thames Essex
mg
DR
P/L
0.00
0.05
0.10
0.15
0.20
Maitland Thames Essex
mg
TP/L
Tile Surface
Source: C. Van Esbroeck – Thesis
Surface Water Quality – 30 ppb or 0.03 mg/L total P
Sources – things you have some
control over
Soil test levels
Application of P
Placement and tillage
Timing
34
Agronomic Loss vs Environmental Impact
Assume -~ 2 ppm change in Soil Test P to change fertilizer P recommendation and this represents an agronomic significant amount
• Takes about 15-20 kg fertilizer P to increase soil test P by 1 ppm similar to decrease??
• so loss of 30-40 kg P/ha to maybe be a significant agronomic loss
• Assume - ~ 40 cm runoff/drainage water at 0.03 mg/L (Water Quality guidelines)
• 0.4 m x 10,000m2/ha x 1000 l/m3 x 0.03 mg/L = 0.12 kg /ha
Sources: Soil test P
Leaching DRP and
STP
Runoff DRP and
STP 36
P stratification in the soil crop residues & surface applications of P
Note: Soil test P differences would likely be greater if smaller depth increments used
Tillage and P Source
Placement (and timing)
Incorporated ↓ P at surface less
available for surface runoff
↑ erosion potential ?
through soil loss ??? likely depends upon degree of mixing and flow through soil
20 kg/ha P fall applied (~45 kg/ha or 41 lb/ac of P2O5)
Consequence of Fall Surface Applied P (by the numbers)
• Not Incorporated
– Most of P stays at surface
– Effective application rate is ????
• If stays in top 2.5 cm 6 x the rate
• Impact on soil test P
– maybe ↑ 6 – 30 ppm
20 kg/ha P fall applied (~45 kg/ha or 41 lb/ac of P2O5)
39
Leaching DRP and
STP
Runoff DRP and
STP (Wang 2010 thesis)
40
Applied P most available right
after application
Water movement: fall spring
periods
P transport: fall spring periods
41
Top Tips for P management
• 1) Apply P at the right time, in the right place
• 2) Promote good soil structure and improve water infiltration
• 3) Keep soil test in agronomic range
42
Apply P at the right time, in the right place
43
Apply P at the right time, in the right place
44
45
Promote soil structure and infiltration
Substantial surface runoff
Water infiltration No surface runoff
46
Promote soil structure and infiltration
Photo from T. Vollmershausen
47 0
20
40
60
80
100
120
0 10 20 30 40 50 60 70
ME
RP
(kg
P2O
5/h
a)
Soil Test P (ppm)
Band
Broadcast
Keep soil test in agronomic range
Putting It All Together
• Water quality issues in Lake Erie have a large economic impact
• Causes of algal blooms today are different than past
• Relatively small losses of P per field add up across the landscape
• Smart phosphorus management is win for both profitability and water quality
48
Thank You
Questions?
49
Jake Munroe jake.munroe@ontario.ca 519 271 9269 Stratford, Ontario
Dr. Ivan O’Halloran iohallor@uoguelph.ca
519 674 1500 ext. 63635 Ridgetown, Ontario
top related