Why more Why more midwestmidwest K problems in K problems in 2003? (And what can I do?)2003? (And what can I do?)

Paul Fixen and T. Scott MurrellPaul Fixen and T. Scott MurrellPotash & Phosphate InstitutePotash & Phosphate Institute

Some possibilities to be discussed

• K application vs crop removal

• Soil test K levels and trends

• Factors influencing soil test K measurement and interpretation

K fertilizer consumption in WI

200

250

300

350

400

450

1975 1980 1985 1990 1995 2000 2005

K 20,

100

0 sh

ort

ton

s .

Percent of total area planted that is in a corn-soybean rotation

47

35

18

69

84

3172 70 40

3122

Padgitt et al., 2000

Historical corn and soybean acreage in WI

0

500

1000

1500

2000

2500

3000

3500

4000

1850 1875 1900 1925 1950 1975 2000 2025

Year

Har

vest

ed a

cres

, x10

00

Corn

Soybean

NASS, 2003

Historical K removal by corn/soybean rotation in WI

0

20

40

60

80

100

120

1920 1940 1960 1980 2000 2020

End of soybean year in corn/soybean rotation

To

tal K

rem

ove

d b

y ro

tati

on

, lb

K2O

/A

NASS, 2003; PPI, 2003

Percent of major field crop area where hay or pasture was a previous crop

4

3

2

5

3

22 2 3

312

Padgitt et al., 2000

Historical alfalfa and corn silage acreage

0

500

1000

1500

2000

2500

3000

3500

1900 1925 1950 1975 2000 2025

Year

Har

vest

ed a

cres

, x10

00

Alfalfa

Corn silage

NASS, 2003

Historical K removal by forage crops in WI

0

50

100

150

200

250

1900 1920 1940 1960 1980 2000 2020

Year

K r

emo

val,

lb K

2O/A

/Yr

Alfalfa

Corn silage

NASS, 2003; PPI, 2003

Wisconsin K Removal by Major Crops

PPI/PPIC/FAR 2002

Alfalfa47%

Corn (grain)15%

Corn (silage)13%

Soybeans11%

Other hay6%

Other8%

Wisconsin partial K budget

PPI/PPIC/FAR 2002

0.94Ratio: R / (F + M)

1.30Ratio: R / F

50.0Balance: (F + M) – R

-172.0Balance: F – R

222Recoverable manure (M)

567Applied fertilizer (F)

739.0Crop removal (R)

Million lb K2O

What can I do? Check K budgets.

• Calculations can be

• Done by hand

• Performed in a spreadsheet

• Performed by PKalc

• Calculator that facilitates balance calculations

• Minimizes calculation errors

www.farmresearch.comwww.ppi-ppic.org

Use a recent soil test to evaluate budgets

Low soil test, andlevels are expectedto decline further

Low soil test, butlevels are expectedto increase

High soil test, butlevels are expectedto decline

High soil test, andlevels are expectedto increase further

tota

l ap

plie

d –

tota

l rem

ove

d

0

+

-0

Difference from target soil test level(Actual soil test level – target soil test level)

+-

Combs and Peters

% o

f sa

mpl

es

Distribution of soil K levels in WI

Wisconsin has the highestWisconsin has the highestfrequency of soils below 160 frequency of soils below 160 ppm ppm in the central Corn Belt in the central Corn Belt MN

OHINIL

IA

WIMI

MO

KY

7077

56715662

54

56

51MN

OHINIL

IA

WIMI

MO

KY

7077

56715662

54

56

51

Central Corn Belt soils testing <160 ppm, %

2001

How soil test levels change depends on many factors

-44281505137264Superior cl

-12388442345138Spencer sil

-644447036361Plainfield s

-413095238914275Miami sil

-263494715810969Carrington sil

-11376421336146Antigo sil

(%)---- (ppm) ----(%)----(ppm) ----

ChangeDryMoistChangeDryMoistSoil type

1080 lb K2O/ANot fertilized

Exchangeable K

Attoe, 1947 (WI)

Laboratory drying temperature can affect soil test K differently for various soils

4357

107

137

47

70

152 151

6075

183198

0

50

100

150

200

250

Marshall Kenyon Mahaska Nicollet andWebsterSoil series

Incr

ease

in e

xtra

cted

K o

ver

a fie

ld m

oist

sam

ple,

per

cent

Dryingtemperature

Air

104 F

122 F

Mallarino et al., 2003 (IA)

Soil clay mineralogy can impact K variability

• Montmorillonite clays

• Fix K under reducing (wet) conditions

• Soil test levels may decrease

• Illite clays

• Release K under reducing (wet) conditions

• Soil test levels may increase

Stucki, 1996 (IL)

Response to K may depend upon soil series

40

50

60

70

80

90

100

110

25 50 75 100 125 150 175 200 225 250 275 300 325

Soil test K, ppm

Rel

ativ

e co

rn g

rain

yie

ld, p

erce

nt

VL L O H VH

Soil seriesCanisteo, Colo, Ely,Nicollet, Tama,Webster. All withlow subsoil K andpoor permeability.

Many others

Mallarino et al., 2003 (IA)

Previously used categories

VL L O H VH New categories

Depth and location of cores impacts variability

No-till field with 10-yr historyTama silt loam

No-till field with 10-yr historyTama silt loamRobbins and Voss, 1991 (IA)

440 580330

440

160

330

440

37 in.37 in.

0

10

Dep

th (i

n.)

1606

8 in.160 – 580 ppm

4 in.330 – 580 ppm

Core number impacts variability

Soil test P category upper limit (ppm)

Fre

qu

ency

(50

to

tal)

0 2

1720

73 1

0

5

10

15

20

25

30

35

40

5 cores per sample

0 0

8

34

8

0 00

5

10

15

20

25

30

35

40

10 20 30 40 50 60 70

20 cores per sample

True average

What can I do? Monitor K status of crops and record metadata.• Watch for visual symptoms of K

deficiency

• Test plant tissue

• Plants with and without visual deficiency symptoms

• Consult “Using Plant Analysis as a Diagnostic Tool”, Kelling et al.

• Test soils properly and consistently

• Note soil moisture conditions at sampling

• Record soil series, landscape position, past cropping history, and nutrient applications

Strive for improved K management

• K management may require more vigilance

• Consider making more intensive K measurements part of an initiative at the retail outlet or consulting business

• Let farmers know there is uncertainty in soil test K data and provide options

• Tissue testing

• Establishing monitoring areas for soil test K under different moisture conditions, soil series, and fertilization practices

• Share findings during meetings to create awareness of your efforts and any results