Crop and Soil Management Issues Related to

Forage Cation Levels

J.B. Peters, K.A. Kelling,

Soil Science Department

University of Wisconsin - Madison

Influence of pH on Alfalfa,

Marshfield 2000

Treatments

• Four K20 levels – 0, 100, 200, 400 lbs K2O/a/year*

• Target pH levels– Marshfield: six levels – 4.8 - 7.3– Spooner: five levels – 4.7 - 6.7– Hancock: eight levels – 4.5 - 7.0

* Applied after first cutting

Average Tissue P Levels

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

Tis

sue

P %

Marshfield Spooner Hancock

0 lb/a K2O100 lb/a K2O200 lb/a K2O400 lb/a K2O

Average Tissue K Levels

0

0.5

1

1.5

2

2.5

3

3.5

Tis

sue

K %

Marshfield Spooner Hancock

0 lb/a K2O100 lb/a K2O200 lb/a K2O400 lb/a K2O

3rd cut, 1999

Average Tissue Ca Levels

0

0.2

0.4

0.6

0.8

1

1.2

Tis

sue

Ca

%

Marshfield Spooner Hancock

0 lb/a K2O100 lb/a K2O200 lb/a K2O400 lb/a K2O

Average Tissue Mg Levels

0

0.1

0.2

0.3

0.4

0.5

0.6

Tis

sue

Mg

%

Marshfield Spooner Hancock

0 lb/a K2O100 lb/a K2O200 lb/a K2O400 lb/a K2O

Effect of crushed wallboard and gypsum fertilizer on soil Ca and K

levels. Arlington, WI.1

Ca (ppm) Exchangeable K (ppm)

Treatment 1995 1997 1995 1997

Control 1875 1650 341 285

4 t/acre WB 2075 1913 388 284

16 t/acre WB 3313 3125 330 213

50 lb S/acre gypsum 1900 1700 320 240

LSD.05 415 526 NS 48gypsum = 65 lbs Ca/acre WB = 320 lbs Ca / ton1 Treatments applied ppi, Spring 1995.

Effect of crushed wallboard and gypsum fertilizer on alfalfa tissue

cation levels. Arlington, WI, 1995.1st Cut

Treatment K Ca Mg---------- % ----------

Control 4.31 1.53 0.504 t/acre WB 4.38 1.66 0.4816 t/acre WB 3.46 1.55 0.4650 lb S/acre gypsum 3.70 1.55 0.41

Pr > F 0.12 0.83 0.17gypsum = 65 lbs Ca/acre WB = 320 lbs Ca / ton

Effect of crushed wallboard and gypsum fertilizer on soil Ca and K

levels. Lancaster, WI.1

Ca (ppm) Exchangeable K (ppm)

Treatment 1995 1997 1995 1997

Control 1450 1325 138 196

4 t/acre WB 1613 1462 106 175

16 t/acre WB 2075 2225 99 151

50 lb S/acre gypsum 1438 1400 105 176

LSD.05 184 289 NS NSgypsum = 65 lbs Ca/acre WB = 320 lbs Ca / ton1 Treatments applied ppi, Spring 1995.

Effect of crushed wallboard and gypsum fertilizer on alfalfa tissue

cation levels. Lancaster, WI, 1995.1st Cut

Treatment K Ca Mg---------- % ----------

Control 4.16 1.39 0.394 t/acre WB 4.32 1.52 0.4216 t/acre WB 3.90 1.49 0.4150 lb S/acre gypsum 3.82 1.44 0.39

Pr > F 0.34 0.01 0.47gypsum = 65 lbs Ca/acre WB = 320 lbs Ca / ton

Effect of crushed wallboard and gypsum fertilizer on soil Ca and K

levels. Spooner, WI.1

Ca (ppm) Exchangeable K (ppm)

Treatment 1995 1997 1995 1997

Control 888 788 171 235

4 t/acre WB 1150 938 144 269

16 t/acre WB 2512 1563 141 213

50 lb S/acre gypsum 936 800 156 223

LSD.05 601 191 23 NSgypsum = 65 lbs Ca/acre WB = 320 lbs Ca / ton1 Treatments applied ppi, Spring 1995.

Effect of crushed wallboard and gypsum fertilizer on alfalfa tissue cation levels. Spooner, WI, 1996.

1st CutTreatment K Ca Mg

---------- % ----------Control 3.77 1.29 0.284 t/acre WB 3.57 1.37 0.2216 t/acre WB 3.49 1.45 0.1950 lb S/acre gypsum 3.57 1.27 0.28

Pr > F 0.11 0.01 0.01gypsum = 65 lbs Ca/acre WB = 320 lbs Ca / ton

1000 2400 Wavelength (nanometers)

Ref

lect

ance

Light absorption

NIRS Concepts

Diagnostics of Forage K

K --- Cl H N -- C

2

NIRS Physics

Inorganic (Salt) Organic (Protein)

Nutrient R SEC

CP .96 .79ADF .92 1.6NDF .93 2.3

UIP .87 1.5SOLCP .81 4.4CA .81 .18

ADF-CP .77 .24NDF-CP .72 .71P .58 .04K .54 .45MG .50 .05ASH ? ?LIGNIN ? ?

2

?NIR

UN

PL

UG

GE

DForages

Fair

Good

Wet chemistry mineral analysis compared to NIR estimation. 3rd

cut, Hancock, 1999.

Regression Equation R2

PNIR = 0.22 + (0.255)(PWET) 0.19

KNIR = 0.98 + (0.579)(KWET) 0.58

CaNIR = 0.55 + (0.891)(CaWET) 0.79

MgNIR = 0.16 + (0.349)(MgWET) 0.41

Wet chemistry mineral analysis compared to NIR estimation. 3rd

cut, Marshfield, 1999.

Regression Equation R2

PNIR = 0.29 + (0.056)(PWET) 0.01

KNIR = 1.46 + (0.335)(KWET) 0.60

CaNIR = 0.57 + (0.884)(CaWET) 0.67

MgNIR = 0.21 + (0.325)(MgWET) 0.68

Wet chemistry mineral analysis compared to NIR estimation. 3rd

cut, Spooner, 1999.

Regression Equation R2

PNIR = 0.26 + (0.068)(PWET) 0.01

KNIR = 1.07 + (0.581)(KWET) 0.36

CaNIR = 0.88 + (0.506)(CaWET) 0.59

MgNIR = 0.16 + (0.457)(MgWET) 0.53

Using NIRS in Forage TestingGeneral Recommendations

General Nutrients

DM yes Lignin limitedCP yes Ash limitedADF yes Ca limitedNDF yes P noStarch yes K noFat yes Mg noBypass CP yes MiroMin noSoluble CP limitedADF-CP limitedNDF-CP limited

Summary

Liming these acid soils was essential to optimize DM production, irregardless of K

• As soil K increased, tissue K increased and tissue Ca and Mg tended to decrease

• Annual applications of K resulted in a buildup of soil K and a decrease in soil test Ca and Mg

Summary, cont.

• As soil Ca increased, tissue K levels tended to decrease and tissue Ca tended to increase, especially on the lighter textured soil at Spooner

• Large applications of Ca resulted in a buildup of soil Ca and a decrease in soil test K

Summary, cont.

• Keeping soil test K levels in the optimum range appears to be the best strategy for keeping tissue K levels in acceptable ranges for use as dairy feed