hosphorus losses from cropland · source: s. cooke grca central western eastern eastern basin p...

Does what we do Really matter out

HERE THERE?

PHOSPHORUS LOSSES FROM CROPLAND

Merrin Macrae (PhD), University of Waterloo Chris Van Esbroeck (MSc), MVCA Kevin McKague (MSc), OMAFRA

Tile Drain

Work Fields

Apply Fertilizer

Grow Crops

Nuisance Algal Blooms

Intake Fouling

Reduced Oxygen

Mycrocystis toxin

Lake Erie, 2009. T. Archer NOAA

February 2014

IJC LEEP REPORT

Lake Erie, 2009. T. Archer NOAA

Some History • In ‘70s, serious eutrophication due to excess P loadings

• Mid-80s, loads cut in ½ (mainly sewage upgrades and reduced P in detergents) – much improved!

• Early 2000’s, symptoms of excess P appear again

• 2011 - 5000 km2 algal bloom (3X any previous)

• Today rural/urban runoff (non-point) is dominant source of P load to lake (>50%)

• Bulk of loading occurs during snowmelt and heavy rains

Report’s Objective To provide advice to help restore the lake’s ecosystem by reducing nutrient loads

BREAKDOWN OF P LOAD BY MAJOR SOURCE

Source: Ohio EPA, April 2010 (Ohio Lake Erie Phosphorus Task Force Final Report)

WHERE IS THE PHOSPHORUS COMING FROM?

Source: Ohio EPA, April 2010 (Ohio Lake Erie Phosphorus Task Force Final Report)

By Major Lake Erie Basin

By Major Jurisdiction

BREAKDOWN OF TRIBUTARY PHOSPHORUS LOAD FROM ONTARIO

Source: S. Cooke GRCA

Central

Western

Eastern

Eastern Basin

P loading by major L. Erie Basin

~ 10,000 T/yr

~ 1200 to 1500 T/yr enters Lake Erie from Lake Huron, Lake St. Clair via Detroit River. (Outlets for the Maitland, Ausable, St. Clair and Thames rivers and Lake Huron shoreline)

HOW IS NPS P LOADING ESTIMATED? Runoff (L/year) X P Concentration (mg/L) = P Load (mg or kg or T)

=

“Forms” of Phosphorus Total Phosphorus (TP) TP = PP + TDP

Inorganic P Organic P

Soluble Reactive P (SRP) Total Dissolved P (TDP)

Particulate P (PP)

(SUP) SUP = Soluble Unreactive Phosphorus TDP = SRP + SUP

Source: Baker and Richards – Heidelberg University

OTHER COMPLICATING FACTORS AFFECTING LAKE ERIE PHOSPHORUS

The near-shore phosphorus shunt: • Nearshore [P] high • Off-shore [P] low (below target) Yet [P] in Niagara River (leaving Lake) is high. Suspected Cause – zebra mussels along the nearshore. (voracious filter feeders, releasing bioavailable P) TP Loadings from tributaries help further feed the nearshore mussels enhancing the problem.

Source: T. Howell MOECC

WHAT IS THE ESTIMATED P LOADING CONTRIBUTION FROM ONTARIO CROPLAND?

NPS P is estimated to be 60% of the total P loading. Assume from Lake Erie studies that 10% of the total NPS P loading to lake Erie originates from Ontario Cropland. Therefore NPS P loading form Ontario Cropland is 0.1 *0.6* 10000 T/yr = 600 T/yr (600,000 kg/yr)

Consider Ontario croplands draining to Lake Erie or Lake St. Clair only (see below).

Source: Env Canada, 2014 Region/Watershed Area (km2) Cropland (%) Cropland Area (ha)

Grand River CA 6965 71 494515

Longpoint CA 2900 78 226200

Kettle CA 520 79 41080

Catfish CA 490 80 39200

Thames River WS 5820 82 477240

Lake Erie N. Shore 737 82 60434

St Clair CA/Sydenham 4100 86 352600

Essex CA 1631 79 128849

TOTAL: 23163 1820118

Estimated Net NPS P from Ontario (kg/year) 600,000

Average TP Load from Cropland (kg/ha/year) 0.33

MOVING UP ONTO THE LAND:

OBSERVING P LOSS AT THE FIELD EDGE

At each on-farm field site, the following is observed: • Weather (rain, temperature, ET, soil moisture) • Overland flow • Tile Flow • Dissolved and total P in the overland and tile flow • Field activities and timing (tillage, fertilizer

application, manure application, planting, harvesting , cover crops, etc.)

Edge-of-Field P loss Monitoring Sites are: • Located in the Lake Erie/South Lake

Huron drainage basins • Considered “well managed” fields

(reduced tillage, follow NMP, relatively low soil P levels)

• Monitored over the entire year (all seasons)

GENERAL DESCRIPTION OF FIELD SITES

Characteristic Maitland Site Thames Site Essex Site

Watershed Area (ha) - Surface - Tile

8.14 7.77

7.79 8.66

(free drainage) 6.7 7.4

Land Slope (%) 0.5-3.5 (uniform) 0.5-3 (hummocky) 0-0.5 (~ level)

Soil Name (texture) Perth/Listowel (SiL) Thorndale/Embro (SiL) Brookston (C)

Soil P test (ppm) 10 16 13

Total P (top 6”) (kg/ha) 1670 1837 1750 (est.)

Tile Drain - Depth (m) - Spacing (m)

~0.9 13.9

~0.9 9.1

0.7

10.7

Rotation Cg-Sb-WWcc Cg-Sb-WW Sb-WW

Tillage “No-till” rotational “No-till” rotational Fall chisel/plow

FIELD INSTRUMENTATION For Monitoring Hydrology and Phosphorus Loss

Monitoring is: • Long-term • Event-based • Year-around • Throughout crop

rotation

Maitland Field Site

Surface watershed boundary

Tile watershed boundary

Field edge monitoring point

On-site climate station

GENERAL FIELD OBSERVATIONS - PRECIPITATION

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

GENERAL FIELD OBSERVATIONS -TOTAL RUNOFF

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

3. Inter-annual Variability in Seasonal Runoff (Surface + Tile)

WHY EMPHASIZE OBSERVING FIELD

HYDROLOGY?

Hydrology Drives Phosphorus Losses

• No runoff (more infiltration and ET) = no P loss

Cropping Activities Interact with a Field’s Natural Hydrologic Cycle

• The method and timing of various field activities relative to the hydrologic cycle influences P loss.

0

2

4

6

8

10

0

0.05

0.1

0.15

Tile

flo

w (

L/s)

DR

P (

mg

/L)

Dec 8 Dec 4 Nov 30

COMMON FIELD ACTIVITIES AND THEIR EFFECT ON P LOSS

The effect of the following common field activities are being observed:

Tillage (Cultivation Method) Tile Drainage

Nutrient Application (Form and Timing)

Crop Type/Cover Crop

Extent of subsurface tile drainage in vicinity of Lake Erie

Surface watershed boundary

Tile watershed boundary

Field edge monitoring point

On-site climate station

Example Field Monitoring Site

Tile Drainage Effects on Hydrology and

Water Quality

SURFACE VS. SUBSURFACE TILE DRAINAGE

It is Important to Make the Distinction!

Surface Drainage Subsurface Drainage

Catchbasins and surface inlets direct surface runoff underground • Can reduce downstream erosion BUT • Can increase hydrologic connectivity

of land to stream

• Only functions if soils in vicinity of tile are:

- Saturated OR - Macropore flow • Good infiltration of water into soil

profile improves their usefulness

May have similar water quality as surface runoff

Tile Drainage Effects on Runoff (Maitland Site Example)

(1574 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)


Surface Runoff by Season

2013 2014

Tile Runoff by Season

Annual Runoff (547 mm )

Surface Tile

(186 mm )

486

60

16

170

2014 (1039 mm precipitation)

Tile Drainage Effects on Runoff (Essex Site Example)

Annual Runoff

Surface Tile

34

132

(166 mm )

RELATIVE CONTRIBUTION OF TILE AND SURFACE RUNOFF

TO ANNUAL P LOAD (MAITLAND SITE: MAY 2012 – APR 2013)

General Conclusions Despite tile runoff contributing to the majority of the total runoff leaving a field: • Surface runoff contained the majority of DRP • Surface = Tile for TP contribution Therefore, surface runoff is a very important pathway for annual P loss . • Erosion control • Improving soil infiltration capacity (to reduce

runoff) are still key steps to reducing P loss from fields

Surface Tile

Source: C. Van Esbroeck – Draft 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)

General Conclusions Similar (although less pronounced) to observations at the Maitland Site. Surface runoff, despite small fraction to total runoff, is a significant P contributor. Therefore, surface runoff is a very important pathway for annual P loss and • Erosion control • Improving soil infiltration capacity (to

reduce runoff) are still key practices for reducing P loss from fields


P CONCENTRATIONS IN TILE AND SURFACE

RUNOFF

(a) DRP

(b) TP

Why is surface runoff P loss significant despite small fraction of total runoff? P concentrations in surface runoff are much higher than in tile drain runoff (i.e. Load = Concentration X Flow)

BUT

Soil type may be a significant factor (note emerging data from Essex)

0.00

0.05

0.10

0.15

0.20

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


Cropping Rotation Tillage Soil Type STP

Discharge (mm)

DRP Load (kg/ha)

DRP (mg/L)

C-S-W Rotational silt loam 25 187.9 0.056 0.019

C-S-W Rotational silt loam 20-25 164.8 0.112 0.074

C-S No-till >25 yrs

silt loam to silty clay 25-40 27.3 0.048 0.232

C-S No-till >20 yrs clay loam 30 360.8 0.539 0.150

C-S-W Rotational clay

35 360.4 0.505 0.140

C-S Rotational silt loam to

clay 50-60 213.4 0.316 0.138

Data from Ohio sites courtesy of Dr. Kevin King, USDA-ARS, Columbus, Ohio

EFFECT OF SOIL TYPE ON P LOSS

TILLAGE EFFECT ON P LOSS

Background US studies are suggesting that adoption of no-till practices has resulted in rise in DRP in runoff (due to stratification, surface application of P, greater infiltration) Ontario Findings (plot site near St Marys (Thames watershed))

Source: G. Opolko - Draft Thesis

[P] (mg/L) in tiles under different tillage systems. RT = 3” disk till 1 in 3 yrs; DT = annual disk & chisel plow to 7”

NUTRIENT APPLICATION TIMING AND PLACEMENT

EFFECTS ON P LOSS (MAITLAND SITE) Fertilizer

P applied


NUTRIENT APPLICATION TIMING AND PLACEMENT

EFFECTS ON P LOSS (THAMES SITE)

Manure P applied

Source: C. Van Esbroeck –Thesis

Observed Trend Towards Larger Fields and Less Crop Diversity

1955

CROP/COVER EFFECTS ON P LOSS (MAITLAND WATERSHED EXAMPLE)


1978



2006


WATER QUALITY AND QUANTITY EFFECTS OF WASCOBS

(MODELLED ESTIMATE)

QUANTITY: Avg. Annual Streamflow: No WASCoBS: 0.260 cms

Existing 18 (2011): 0.242 cms Existing 18 + Future 14: 0.224 cms

-15.0

-10.0

-5.0

0.0

5.0

10.0

15.0

Sed PP DRP TP TN

% C

ha

ng

e i

n L

oa

din

g

No WASCoBs Existing 18 + 14 New

QUALITY:

Note: Relative to existing (2011) conditions (i.e. 18 WASCoBs )

Lack of Crop Diversity across Ontario

CROP/COVER EFFECTS ON P LOSS

Sample Map form Southern Ontario Fields that Grew only Corn or

Soybeans 2011 – 2013

Can Cover Crops help offset this lack of diversity?

Added Potential Benefits from cover crops for Controlling P Loss: • If left overwinter, protects soil during

vulnerable period from erosion • Helps improve soil infiltration (= less

runoff) • Improved soil structure/roots • Increased ET potential

Cover Crop Erosion Control (P loss) Benefits (Chatham-Kent Example)


Visual Observations (erosion)

Field with Over-Winter Cover Crop Field Without Cover Crop

Cover Crop Erosion Control (P loss) Benefits (Chatham-Kent Example)


Visual Observations (Soil Water/Structure)

Field with Over-Winter Cover Crop Field Without Cover Crop

SUMMARY We recognize:

• Just a small loss can have a big impact downstream

• Conversely, if small improvements were made, significant benefits may be seen.

• Hydrology drives P loss process. Water moves both overland and through tiles. Overland runoff is most concentrated (DRP and TP)

• Soil type likely plays a role – clays most susceptible

• The period for greatest P losses from cropland is during the NON-GROWING season.

• P applied is most vulnerable to loss soon after it is applied and especially if applied and left on surface

SUMMARY What Can We Do/Try?

• Don’t aim for a high soil test P. (Soil test – know what you have)

• Protect the soil from erosion, and encourage infiltration (esp. during non-growing season) (Cover crops, Crop Residue)

• Apply P in the spring not the fall, and preferably incorporate

• Consider increasing your crop diversity, not your tile drain spacing (Diversify - Include winter wheat , cover crops, forages)

• Make it more difficult for water to flow off your fields. (Strips, or buffers and, if needed, waterways or WASCoBs (in concentrated flow areas)

hosphorus losses from cropland · source: s. cooke grca central western eastern eastern basin p...

Documents