Tools for Phosphorus Management

Andrew SharpleyWater to Worth: Spreading Science and

SolutionsDenver, CO; April 1 – 5, 2013

History risk assessment

Revision of the NRCS 590 Nutrient Management Standard & P Indices

Its use & misuse for P management

BMPs and their assessment

The way forward

Today’s presentation

ARS Land Grant

National P locations

• National P Research Project outcomes Standardized methods for rainfall – runoff

studies

Established relationships between STP and runoff

Integrated into P Indices

Incorporated into NMP process

•Success partly due to Group effort – Land Grant & ARS

Flexibility to adapt to State needs

Learning from the past

..it was mobile

Arkansas

Illinois

Virginia

New York

Outreach

Soil P & runoff P

Dissolved

P

mg L-1

Mehlich-3 P, mg kg-

1

FD-36 watershed - PA

1

0

2

3

0 200 400 600 800

R2 = 0.86

Crop response

200 mg L-1

Change point

P loss affected by many factors177

14444

4620

1

<1

97

55

DP

8

DP78

92

0

Tony Buda, ARS, PA

Soil P – ppmP added – kg P/ha/yrRunoff – litersP loss – kg P/ha/yr

HighsourceHigh

source

Hightransport

Hightransport

Critical Source AreaCritical Source Area

Led to the 80/20

rule:

80% of P comes

from 20% of land

area

Risk assessment used by most states for nutrient management

planning (CPS 590)

Factors in P Index

• Runoff potential

• Erosion potential

• Leaching potential

• Proximity to stream

TransportSource• Soil P content

• Added P• Rate, method,

timing of fertilizer & manure

• Manure P solubility

1

0

2

3

P index value for the site0 50 100 150 200

R2=0.80

75 kg P/ha TSP

112 kg P/ha poultry litter

150 kg P/ha poultry manure

Runoff P,

g/ha

Very high

High

Med

Low

Testing the P Index

Soil P, mg/kg

P loss is controlled by many factors

• Disparity among Indices across the country Varied with soils, topography, & state

priorities

• Often, not leading to a decline in STP nor improvement in water quality Legacy effects

• Perceived as farmer friendly

• The P Index was never meant to be the solution to P management issues

Where was the breakdown

P loss kg ha-1

AL AR GA MS NC TN TX

0.5 Low Low Low Low Low High Med.

2.7 Med. High High Low LowV.

HighHigh

4.0 Low High Med. Low LowV.

highHigh

5.8 LowV.

highV.

highLow Med.

V. high

High

10.9 LowV.

highV.

highLow Med.

V. high

High

23.7 LowV.

highV.

highLow High

V. high

High

Southern P Indices

Osmond et al., 2012

• Appropriately account for major sources & processes determining P loss & rank risk of loss for any given site

• Directionally and magnitudinally correct

• Interpretations based on assigned risk are equivalent across state borders, given similar site & water resource conditions

• Where inadequacies exist, the causes can be identified & addressed

P Indices should …

• At a minimum this should include Site runoff, management, climate,

water quality Event, planning / rotation period &

annual loss Natural rainfall

• Network of sites and data exchange being developed – Kleinman et al.

• MANAGE – Daren Harmel

Database development

• Select appropriate model APEX, APLE, DrainMod

Locally calibrated (within state)

Event, planning / rotation period & annual loss

• Model & Index must estimate P loss & simulate P mobilization & transport over same time scales

Model use

Farm gateBMPsDietary P mgt. &

use of enzymes enhances nutrient

absorption & reduces excretionManure

additivescan reduce P

solubility & NH3 loss

Manure treatmentSolid-liquid separation,

struvite, zeolite

Struvite

Subsurface injectionreduces P runoff & N

volatilization

Soil & manure testing

to tailor rates of P to apply

Source BMPs4 R’sAppropriate rate, method timing, &

placementof P can increase crop

uptake & decrease runoff loss

Rotational grazingreduces P runoff & N

leached

Stream bank

fencingDecreases P deposition in

streams

Transport BMPs

Conservation tillage

reduces P runoff

Riparian buffers

trap particulate nutrients

Cover cropsreduces P runoff

BMP Credit

Diversion 5%

Terrace 10%

Pond 20%

Fenced Pond 30%

Filter Strip 20%

Fenced Filter Strip 30%

Grassed waterway 10%

BMP effectiveness

BMPCredi

t

Fencing 30%

Riparian Forest Buffer 20%

Fenced Riparian Forest Buffer 35%

Riparian Herbaceous Cover 20%

Fenced Riparian Herbaceous Cover

30%

Field Borders 10%

BMP effectiveness

-100 1000

Effect on total P loss, %

Decreased loss Increased loss

Manure mgt. system (14)

Nutrient mgt. plan (14)

Stream fencing (3)

Vegetated buffers (34)

Dinnes et al., 2004 & Gitau, 2005

BMP effectiveness

-40%

-15%

Farm pond (12)

-50%

-28%

-65%

AR Water Resources Center, 2012

Dissolved P

Total P

2000 0.224 0.377

2003 0.148 0.244

2011 0.070 0.130

Mean annual concentration, ppm

River P @ HWY 59

Maumee River watershed

Sandusky River

watershed

MICHIGAN

Lake ErieLake Erie

OHIO

Lessons from Lake Erie Basin

Trends in P – Maumee River

Annual flow-weighted total P, ppm

1975 1985 1995 2005

0.8

0.6

0.4

0

0.2

50% decrease

Dave Baker & Peter Richards, OH

Adoption of mulch and no-till soybeans, %

1975 1985 1995 2005

0.12

0.09

0.06

0

0.03

Annual flow-weighted dissolved P, ppm

75% decrease

80

60

40

20

Trends in P – Maumee River

1975 1985 1995 2005

0.12

0.09

0.06

0

0.03

Adaptive management may have reduced nutrient loss Incorporation of fertilizer

and manure

Winter cover crops

Spring fertilization

Trends in P – Maumee River

• Spring workload is huge with more time-sensitive tasks

• Fertilizer usually costs more in spring

• Less soil compaction on frozen ground

But the reality is …….

• Researchers need to step back and look at the big picture

The bottom line

Thank you

Questions ??