Opportunities and Challenges to Implementing Non …...-40 -20 0 20 40 60 80 100 ractice Moving from Fall to Spring N Application Sidedress N Application Reduce N rate to MRTN* Nitrification

Department of Agricultural and Biosystems Engineering

Opportunities and Challenges to Implementing Non-Point Source Nutrient

Reduction Practices

Matthew HelmersDirector, Iowa Nutrient Research Center

Dean’s Professor, College of Ag. & Life Sciences Professor, Dept. of Ag. and Biosystems Eng.

Iowa State University

Department of Agricultural and Biosystems Engineering

Mississippi River System

Gulf of Mexico Hypoxia Goals

Hypoxia Action Plan Goal: Reduce the size of the zone to 5,000 km2

by 2015

EPA-SAB Recommendations: Reduce Total Riverine Nitrogen and Phosphorus Loads by 45%

Historic Changes

Soil Nitrate Production vs. Crop Nitrate Uptake

In the shaded areas, the soil produces nitrate, but there is no crop to use it. As a result,

some nitrate is lost to waterways.

March February

Rate of soil nitrate

production from

native soil organic

matter

Rate of corn or

soybean nitrate uptake

The majority of nitrate used by corn and soybean comes from soil nitrate production.

Corn gets the difference from fertilizer while soybean gets

the difference from legume fixation of atmospheric nitrogen.

Slide from M. Castellano - ISU

What Can We Do to Reach

These Goals?

Phosphorus Practice Performance

(Field to Stream Reduction)

Estimate Total Phosphorus Load Reduction (%)

0 20 40 60 80 100

Ph

osp

ho

rus R

ed

uctio

n P

ractice No phosphorus until STP drops to optimal level

No-till (70% residue) vs. conventional tillage (30% residue)

Cover Crops (Rye)

Perennial - Land retirement

Pasture

Buffers

Terraces

Error bars show standard deviation of practice performance

Nitrate-N Practice Performance

Estimate Nitrate-N Concentration Reduction (%)

-40 -20 0 20 40 60 80 100

Nitra

te-N

Re

du

ctio

n P

ractice

Moving from Fall to Spring N Application

Sidedress N Application

Reduce N rate to MRTN*

Nitrification Inhibitor

Cover Crop

Extended Rotations

Perennial Energy Crops

Pasture and Land Retirement

Controlled Drainage**

Shallow Drainage**

Wetlands

Bioreactors

Saturated Buffers**

*MRTN - Maximum Return to Nitrogen Application Rate from Corn Nitrogen Rate Calculator (http://cnrc.agron.iastate.edu/)** Load reduction Error bars show standard deviation of practice performance

Nitrate

Response to

Nitrogen

Estimated Nitrogen Application Rate –

Manure + Fertilizer (2008 Estimates)Rate on

CB

Rate on

CC

MLRA lb N/ac lb N/ac

102C 182 232

103 154 204

104 144 194

105 131 181

107A 184 234

107B 139 189

108C 163 213

108D 120 170

109 142 192

115C 146 196

Iowa Total 151 201

Nitrogen Application Rate Example

Existing Conditions – N Rate MRTN – N Rate

Soil Nitrate Production vs. Crop Nitrate Uptake

Addition of a Cover Crop

March February

Rate of soil nitrate

production from

native soil organic

matter

Rate of corn or

soybean nitrate uptake

Cover crops can use nitrate when corn and beans are not growing, thus reducing the

asynchrony between soil nitrate production and crop

nitrate uptake.

Cover crop

nitrate use

Cover crop

nitrate use

In the shaded areas, the soil produces nitrate, but there is no crop to use it. As a result,

some nitrate is lost to waterways.

Slide from M. Castellano - ISU

Winter Cereal Rye Cover Crops

Ames Gilmore City

Impacts of Cover Crops on Nitrate-N Load in

Drainage Water – Gilmore City

36% Reduction

34% Reduction

NWRF Drainage NERF Drainage

COBS

SERF Drainage

Replicated subsurface drainage plots to evaluate performance of various in-field management practices

Gilmore City DRF

Impact of Land Management

Drainage water management

From Christianson and Helmers, 2011

Illustration by John Petersen

(www.petersenart.com)

Subsurface Drainage Bioreactor

Saturated buffers

Corn

Soybean

1 km

Targeted Wetland Restoration

DD Tile

There is considerable interest in using wetlands to intercept and

reduce nitrogen loads in tile drained landscapes.

Nitrate Removal Wetland

Hydrologic and nutrient loading rates are

major drivers of wetland performance.

Wetlands occupying only 1% of landscape can reduce long term average nitrate loads about 52%.

From: W.G. Crumpton

Drainage water recycling

Science-based Trials of Row-crops

Integrated with Prairie Strips

www.prairiestrips.org

Photo: Jasper Co., Matt Helmers• Watershed-based scientific monitoring

• Comparing prairie strip treatments to 100% corn-soy crop control

Science-based Trials of Row-crops

Integrated with Prairie Strips

www.prairiestrips.org

Strategically adding ~10% prairie to crop fields:

• 44% reduction in water runoff

• 95% reduction in soil loss

• 90% reduction in P runoff

• 84% reduction in N runoff

• 70% reduction in subsurface NO3-N concentrations (not tiled)

• Potentially improves beneficial insects and wildlife

• Doesn’t reduce per acre yields

• Doesn’t create a weed problem

• Cheaper than installing terraces; cost comparable to cover

crops

Source: Data collected between 2007-2014 at Neal Smith National Wildlife Refuge

Imag

es: J

ose

Gu

tier

rez

These flumes measure surface water movement and soil, nitrogen and phosphorus export from the STRIPS experiment sites at the Neal Smith National Wildlife Refuge. Compare the transport of these resources from: 1) a 100% no-till, corn crop field, 2) a 90% corn crop field treated with a 10% prairie strip, and 3) a 100% prairie. These pictures were all taken after the same 4” rain event in June, 2008.

1 2 3

Phosphorus Loss in Runoff (2007-2012)

Zhou et al., 2014

>90% Reduction in TP export from watersheds with prairie filter strips

Nitrate-N Concentrations in Groundwater at the Footslope of Each Watershed

Example: Combination Scenarios that Achieve N and P Goal From Non-Point Sources

From Iowa Nutrient Reduction Strategy: Goals for Nonpoint Sources is 41% reduction on

Nitrogen and 29% reduction on Phosphorus

Nitrate-N

Reduction

Phosphorus

Reduction

Initial

Investment

Total Equal

Annualized

Cost

Statewide

Average EAC

Costs

Practice/Scenario% (from

baseline)

% (from

baseline)(million $)

(million

$/yr)($/acre)

MRTN Rate, 60% Acreage with

Cover Crop, 27% of ag land treated

with wetland and 60% of drained land

has bioreactor

42 30 3,218 756 36

MRTN Rate, 95% of acreage in

Cover Crops, 34% of ag land in

heavily tile drained land treated with

wetland, and 5% land retirement

42 50 1,222 1,214 58

Level of Implementation Needed for

one Nitrate-N Reduction Scenario

To Reach our Goals

• WE NEED IT ALL!!

– N Management

– Cropping practices/landuse

– Edge-of-Field Practices

Potential Impacts of Pursuing

These Strategies?• Economic Evaluation of Governor

Bradstad’sWater Quality Initiative

(https://governor.iowa.gov/sites/default/file

s/documents/ISU%20CARD%20Economic

%20Evaluation.pdf)

Projected Annual Costs for NCS1NCS1 Mil of Ac Estimated

N Tons

Reduced

(1000)

Initial

Investment

($/ac

Treated)

Initial

Investment

($Million)

Equal

Annual

Cost ($/ac)

Equal

Annual

Cost

($Million)

Nitrogen

Optimized

18.9 25 -2 -38

Cover

Crops: 60%

12.6 47 25 315

Wetlands:

27 of Ag

Land

7.7 42 316 2427 10 80

Bioreactors:

60% of

drained

land

5.9 33 133 790 8 50

Total 3217 407

Per Acre 19

Projected Annual Benefits for NCS1NCS1 Source Low ($Million) High ($Million)

Reduced Soil

Erosion

Wetland 40 72

Cover Crops 22 32

Recreation/Wildlife

Wetland 3 7

Water Based

Recreation

5 22

Residential

Amenity

17 35

Drinking Water

Purification

0 13

Total 87 183

Average 135

Total Economic Impact of NCS1

Direct Total

Total Economic Impact Under NCS1

Output ($) 445,000,000 691,000,241

Value Added ($) 155,202,063 296,359,597

Labor Income ($) 173,429,609 250,678,858

Employment 1149 2801

$445 million in spending would create $691 million in total economic activity

What is the Payoff?

• Improved local water

• Protection of our soil resources

• Employment opportunities to implement

these practices

• More diverse landscape

Summary

• To reach the goals will take broad

implementation of multiple practices

• Are there opportunities to implement practices

that enhance or protect long-term value of the

land?

• Are there rural economic benefits?

Discussion

[email protected]

Twitter: @ISUAgWaterMgmt

Website: http://agwatermgmt.ae.iastate.edu/

Department of Agricultural and Biosystems Engineering