Assessing Nitrogen Use Efficiency On-Farm

University of California- DavisDepartment of Land, Air, and Water Resources

Dr. Rob MikkelsenDirector, Western Region, North America Program

May 2009

IPNI Mission“to develop and promote scientific information about the responsible

management of plant nutrition for the benefit of the human family.”

Dr. Rob MikkelsenWestern RegionMerced, CArmikkelsen@ipni.net

What is driving fertilizer demand?

• Population growth• Change in diets due to increasing household incomes

in developing countries…incomes above $16,000 per yr will rise from 352 mil in 2000 to 2.1 billion by 2030 (World Bank)

• Critically low ending stocks … global food crisis

• Supply and demand for grain and oilseeds … crop prices

• Lack of adequate production capacities

• Energy costs – heat, fuel and shipping

• Weak U.S. dollar

Food demand to double by 2050

World demand for food

0

2

4

6

8

10

1950 1960 1970 1980 1990 2000 2010 2020 2030 2040 2050

Population, billions

0.00

0.10

0.20

0.30

0.40

0.50

0.60

1961 1966 1971 1976 1981 1986 1991 1996 2001

Arable land per capita, ha

• “…food production has to increase 50% by 2013 and double in 30 years…”

– (Source: Global Challenges for Humanity, 2008 State of the Future, Millennium Project)

Source: FAO Source: FAO

Anhydrous Ammonia

H2O

CH4

O2 N2

NH3

Urea Synthesis . . . Step One

NH3

CO2

NH3

Carbamate

- +

Urea Synthesis . . . Step Two

Carbamate

- +

Urea

H2O

Why Improve Nitrogen Use Efficiency?

• Economics• Environmental impacts

– Nitrate in drinking water– Eutrophication & hypoxia – Biodiversity loss – Smog and PM2.5 from ammonia emission– Ozone depletion – N2O – Greenhouse gases – N2O and CO2

EPA INC Draft Recommends -Reduce Nr Loss to Environment by 25%

• Decrease livestock-derived ammonia emissions to approximately 80% of 1990

• Decrease excess flows of Nr into streams, rivers, and coastal systems by approx. 20%

• Increase crop output while reducing total Nr up to 20% of applied artificial Nr.

• High priority for a targeted construction grants program under the CWA (i.e wetlands)

From DRAFT report Nov. 15, 2008

Definitions of NUE

• Partial Factor Productivity (PFP)– Grain harvested per unit of N applied– 40-80 units of grain per unit of N

• Agronomic Efficiency (AEN)– Increase in grain harvested per unit of N applied– 10-30 units of grain per unit of N

• Partial nutrient balance (PNB)– N removed in grain as % of N applied– Often 80% or more

• Apparent Recovery Efficiency (REN)– Increase in N taken up into plant as % of N applied– 30-50% typical; 50-80% with BMPs

NUE Term Calculation Reported Examples

PFP - Partial factor productivity

Y/F 40 to 80 units of cereal grain per unit of N

AE - Agronomic Efficiency

(Y-Y0)/F 10 to 30 units of cereal grain per unit of N

PNB - Partial nutrient balance (removal to use ratio)

UH/F 0 to > 1.0 - depends on native soil fertility and fertility maintenance objectives<1 in nutrient deficient systems (fertility improvement)

>1 in nutrient surplus systems (under replacement)

Slightly less than 1 to 1 (system sustainability)

RE – Recovery efficiency of applied nutrient

(U-U0)/F 0.1 to 0.3 - proportion of P input recovered first year

0.5 to 0.9 - proportion of P input recovered by crops in long-term cropping systems

0.3 to 0.5 - N recovery in cereals-typical

0.5 to 0.8 - N recovery in cereals- best management

F-amt. nutrient applied, Y- yield of harvested portion with applied nutrient, Y0- yield of harvested portion with no applied nutrient, UH –nutrient content of harvested portion of crop, U –total nutrient uptake in aboveground biomass with nutrient applied, U0 –total nutrient uptake in aboveground biomass with no nutrient applied

Nebraska; Dobermann & Cassman, 2004

RE: Apparent Crop Recovery Efficiency

kg increase in N uptakeperkg N applied

strongly influenced by management, synchrony, climate…

Nebraska; Dobermann & Cassman, 2004

PE: Physiological Efficiency

kg yield increase perkg increase in N uptake from fertilizer

IE: Internal Utilization Efficiency

kg yieldperkg N uptake

PE- ability to transform fertilizer nutrients into grain

IE- ability to transform all sourcesinto grain

Nebraska; Dobermann & Cassman, 2004

AE: Agronomic Efficiency

kg yield increaseperkg N applied

PFP: Partial Factor Productivity

kg harvested productperkg N applied

AE- reflects efficiency of plantusing each additional unit of N

PFP- most important for farmers

Example – Irrigated Corn

N rate, lb/A

Yield,bu/A

PFP, lb/lb

AE,lb/lb

PNB, % RE, %

Net return to N, $/A

0 120 - - - - -

90 143 89 14 100 36 45120 147 69 13 78 33 47150 149 56 11 64 30 43

NUE: optimize versus maximize

Calculated from Shapiro and Wortmann, 2006. Agron. J. 98:529–535

N rates applied to corn in the UShave been relatively stable for 3 decades

lbs

of g

rain

per

lb o

f N

As a result…Yield per unit of N has increased over the last 30 years

Some farmers consistently harvest more than75 lbs of grain for each lb of N applied

Partial Factor Productivity (PFP) Trend for N Fertilizer Use on Corn, USA

Data source: USDA-NASS-ERS

Why Improve Nitrogen Use Efficiency?

• Economics• Environmental impacts

– Nitrate in drinking water– Eutrophication & hypoxia – Biodiversity loss – Smog and PM2.5 from ammonia emission– Ozone depletion – N2O – Greenhouse gases – N2O and CO2

Fertilizer and Optimum Soil Fertility Stretch Moisture

The “Myth” of N Fertilization for Soil C Sequestration- CONTROVERSIAL(Khan, et al. 2007. J Environ Qual. 36:1821-1832.)

• Fertilizing at N rates higher than optimum for yield is unlikely to increase soil C

• Many long-term studies show soil C is higher with optimal compared to zero N

Adapted from Paustian et al., 1992 Schulten and Schnitzer,1997

New Hybrids prolong N Uptake

Tollenaar, et al., 1997

Genetics

A new hybrid yields more with less N, compared to one popular 20 years ago. Mean of 4 years’ data from Illinois (Below, 2007).

GM Genetics?

A “triple-stack” Bt-rootworm hybrid responds differently than one with a single herbicide resistance trait (2006 data; Below, 2007).

single triple

MERN, lb/A 86 132

Yield, bu/A 172 226

PFP, bu/lb 2.0 1.7

AE, bu/lb 0.8 0.6

PNB, % 151 128

RE, % 87 69

http://www.fertilizer.org/ifa/publicat/PDF/2005_ag_frankfurt_lammel_slides.pdf

Weather often regulates crop productivity more than nutrient input rates in high productivity systems

60

80

100

120

140

160

180

200

0 20 40 60 80 100 120 140 160 180 200

N rate, lb/A

with Pwithout P

Effect of N and P on Corn Yield

Schlegel, Dhuyvetter, and Havlin, 1996J. Produc. Agric. 9:130 year average

N rate at max yield:with P = 167 lb/Awithout P = 161

P increased N use efficiency instead of greatly increasing N fertilizer demand

0

50

100

150

200

0 40 80 120 160 200

N rate, lb/A

Soil

NO

3-N

in u

pper

10

ft, lb

/A

with Pwithout P

P Reduces Residual Soil Nitrate and Potential for Nitrate Leaching

At optimum N rate P reduced residual nitrate by 66%

Schlegel, Dhuyvetter, and Havlin, 1996J. Produc. Agric. 9:130 year average

Deliberate nutrient shortages…

…like taking thespark plugs from the engine of a car

Ending Poverty Requires Fertilizer…

Summary

• Nitrogen use efficiency & effectiveness should be measured, managed and optimized applying ecological principles to intensify cropping systems

• Improve NUE with BMPs, genetics, enhanced-efficiency products, & managing for weather.

• Practices that improve NUE need on-farm research and validation

www.ipni.net

Nitrogen Efficiency in Global Animal Production

Van der Hoek. 1998. Environ Poll. 102:127-132

Nitrogen Efficiency in Global Animal Production:

Nitrogen essential for milk, eggs, wool, meat…

~ 2/3 of protein intake provided by grass

~ 1/3 of protein intake provided by feed

Global N efficiency in animal production is about 10%

(Efficiency defined as N in animal products per N input)

K. Van der Hoek. Environ. Poll. 102:127.

The “4R” strategy

Efficient fertilizer Management

Right Source atRight RateRight TimeRight Place

For the crop, field or field zone, and nutrient

Scientific Principles for Fertilizer BMPs – Source

• Ensure a balanced supply of essential nutrients.• Supply plant-available forms.• Suit soil physical and chemical properties.• Recognize:

– synergisms among nutrient elements and sources;– blend compatibility;– associated nutritive or non-nutritive elements.

Enhanced efficiency Fertilizers

1. Synthetic organic compounds containing Nurea-formaldehydes, IBDU, triazines, etc.

2. Physical coating or barrier around soluble N fertilizerSCU, PCU, etc.

3. Stabilized materialsnitrification and urease inhibitors

Block activity of Nitrosomonas bacteria (NH4+ NO2

-)

Scientific Principles for Fertilizer BMPs – Rate

• Assess:– Soil nutrient supply;– All available nutrient sources;– Plant demand.

• Predict fertilizer use efficiency.

Scientific Principles for Fertilizer BMPs – Timing

• Match timing of crop uptake.• Assess dynamics of soil nutrient supply.• Recognize timing of weather factors influencing nutrient

loss. • Evaluate logistics of field operations.

Scientific Principles for Fertilizer BMPs – Placement

• Recognize root-soil dynamics.• Manage spatial variability.• Avoid detrimental effects on plant roots, leaves and

seedlings. • Limit potential off-field transport of nutrients.

Key Principles: Right Place

• Recognize root-soil dynamics.• Manage spatial variability.• Limit potential off-field transport of nutrients.

www.ipni.net

Thank You