Evaluation of Nutrient Use Efficiency Using County and Hydrologic Unit Nutrient Budgets for U.S. Cropland and Soil Test Summaries

Paul E. Fixen, Quentin Rund, Ryan Williams, Tom W. Bruulsema, Clifford R. Snyder, T. Scott Murrell, and Harold F. Reetz Jr.

IPNI and PAQ Interactive

ASA-CSSA-SSSA International Annual MeetingNovember 3, 2009

Contemporary issues with potential to impact cropland nutrient budgets

Manure composition changes due to distillers grains

Climate change induced shifts in cropping patterns,

yields, soil processes

Changes in crop species due to

bioenergy

Application of bioash

Changes in plant parts harvested due to bioenergy

Major changes in fertilizer costs or

crop prices

Genetic changes that alter crop

yields and NUE

Government policy

NuGIS objectives and methodology• Generate maps down to the county and watershed level for:

– N, P and K

– Nutrients in harvested crops, nutrients from excreted and recoverable manure, fertilizer applied, nutrient budgets, and removal to use ratios

– Ag Census years, every 5 yrs from 1987-2007.

• Data sources:– Nutrients in harvested crops

• Crop production (3-yr average i.e. 2007=2006-2008): USDA-NASS

• Nutrient removal coefficients: IPNI (Murrell, 2005)

– Manure nutrients

• Livestock numbers: USDA-Ag Census

• Estimates of excretion and recoverability: USDA-NRCS (Kellogg, others)

– Fertilizer applied

• State: AAPFCO

• County: AAPFCO when available; when not available, state total partitioned to counties using Ag Census fertilizer and lime expenditures.

• Geospatial techniques used to migrate county data to 8-digit hydrologic units, then aggregated to watershed regions targeted by the SPARROW model

Fertilizer consumption in the U.S., 1950-2009

0

2

4

6

8

10

12

14

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

Fert

ilize

r con

sum

ptio

n, m

illio

n to

ns

N

P2O5

K2O

**

*

*Preliminary estimates for 2008 & 2009 provided by Vroomen (TFI), 10/09/2009.

Ag Census Years

y = 0.00576x - 7.05

y = -0.0191x + 39.06

y = -0.0801x + 158.64-3

-2

-1

0

1

2

3

4

5

6

1985 1990 1995 2000 2005 2010

Mill

ion

shor

t to

ns

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1985 1990 1995 2000 2005 2010

Rem

oval

to u

se ra

tio

Nutrient budget trends in the U.S. (Fertilizer use + recoverable manure + N fixation* vs removal by crops)

N

P2O5

K2O

*N fixation assumed to be equivalent to the N removed in the harvest of alfalfa, soybeans, and peanuts.

N

P2O5

K2O

K-2007 U.S. 481.30

Removal = Use

Use>Removal

Removal>Use

1.11.0

1.2

0.83.1

1.1

K removal exceeds use but soil levels are generally v. high

K removal exceeds use by 10-20% in western Corn Belt

0.9

0.8

K use is about twice removal in Southeast

Estimated K Fertilizer Sales

Estimated P Fertilizer Sales

Use of Census data to estimate county nutrient use fixes the N:P2O5:K2O ratio for the state … a problem where regional soil fertility differences exist.

0.76 – 0.89

0.61-0.73 0.49-0.51

US = 0.80N

0.92

0.35

P-2007

1.31.6 1.2

1.1

1.2

0.9

U.S. 480.92

P removal exceeds use in much of the

Corn Belt

1.0

1.2

0.5

0.7

0.9

1.1

1.3

1.5

1.7

1985 1990 1995 2000 2005 2010

Rem

oval

to u

se ra

tioP removal to use ratios for the “I” states

IA

IL

INIAIL IN

253633

253629

Median Bray P, ppm2001 2005

P budgets for Iowa, Illinois, and Indiana per acre planted to principal crops

IA IL INlb P2O5/A*

Fertilizer applied (2007) + 30 29 33Recoverable manure (2007) + 12 3 8Crop removal (avg of 06/07/08) - 53 52 48Balance = -11 -20 -7

*Based on avg of 2006-2008 acreage.

Typical Bray1 or Mehlich 3 decline, ppm: 0.6 1.1 0.4If continued for 5 years: 3.0 5.5 2.0

P budget uncertainties

• Removal coefficient for corn grain– Grain P concentrations are known to vary considerably

– NuGIS uses the average of published Northcentral univ. values

– Sensitivity analysis for IL in 2007

Source Value, lb P2O5/bu Resulting Rem/Use

NuGIS: 0.38 1.60

Feedstuffs 2008 Table: 0.34 1.49

Western Corn Belt res samples: 0.26 1.27

• P removed by crops from subsoils … not sampled

• P contributed from soil organic matter … not measured by tests

• P lost in erosion

Inputs and outputs of N & P by managed pathways.

Vitousek et al. (Science, 2009).

Removal to use ratio (partial nutrient balance or recovery by balance method)

1.640.948.4 0.88 0.61 0.42

Nutrient balances by region (kg/ha/yr)

Western Kenya (low input

corn-based)

North China (wheat/corndouble crop)

Midwest U.S. (corn/soy-

bean)

Inputs and outputs N P N P N P

Fertilizer 7 8 588 92 93 14

Biological N fixation 62

Total agronomic inputs 7 8 588 92 155 14

Removal in grain and/or beans 23 4 361 39 145 23

Removal in other harvested products 36 3

Total agronomic outputs 59 7 361 39 145 23

Agronomic inputs minus harvest removals -52 +1 +227 +53 +10 -9

1.600.97Illinois, NuGIS:

K-1987 K-2007

Elimination of most of the K surpluses.

Changes in Corn Belt P and K Budgets Removal/Use

P-1987 P-2007

From P deficits and surpluses to mostly deficits.

Summary• Nutrient budgets are important to farmers and to society as

indicators of sustainability.

• Weaknesses exist in our current capacity to accurately evaluate nutrient budgets at appropriate resolution:

– Crop nutrient removal coefficients

– Census data for specific nutrient use expenditures

– AAPFCO county level fertilizer sales data.

• Crop nutrient removal is increasing faster than nutrient use nationally and in some key production areas.

• Most of the Corn Belt appears to be mining soil P and many areas appear also to be mining soil K

– P and K use efficiency, expressed as partial nutrient balance, appears unsustainably high

– Intensive monitoring of soil fertility is a critical BMP.