influence of aeration implements, amendment and soil taxa on phosphorus losses in grasslands

INFLUENCE OF AERATION IMPLEMENTS, AMENDMENT AND SOIL TAXA ON PHOSPHORUS LOSSES IN GRASSLANDS

D.H. Franklin, D.M. Butler and M.L. Cabrera

Introduction Attenuation of rainfall within the solum may

help: Extend forage productivity during droughty periods Retard flooding during periods of heavy rainfall Move nutrients and contaminants into soil to be

better utilized, transformed or sequestered

Animal manures can be An environmental hazard An economic resource for added N, P, K, Ca and C

Introduction Following surface application of broiler litter

mechanical aeration may be able to increase infiltration and improve soil/nutrient contact time and thereby retain more resources in the soil

Objectives Review three studies, 2 small plot

studies and one field-scale paired watershed study

Determine impact of aeration of runoff volume and P losses in runoff

Mixed fescue-bermudagrass grasslands

Methods – Three studies Mechanical aeration in mixed fescue-

bermudagrass [tall fescue (Festuca arundinacea Schreb.)/bermudagrass (Cynodon dactylon L.)] grasslands

P amendments Broiler litter, dairy slurry, mineral

Soil taxa varied among studies (hydrologic properties)

Hutchins et al. (2007)

Rainfall Simulation – Slit Aeration, 2-m2 Plots Altavista (fine-loamy, mixed, semiactive, thermic Aquic Hapludults)

Spike

TreatmentsNutient - B = Broiler Litter; T Triple Super PhosphateAeration - X = Control (none); S = Spike

Natural Rainfall – Scale 0.8-ha FieldsMultiple Soil taxa, Broiler litter

Treatments Aeration - With &

Without Paired Watersheds

(before and after) Fields 2, 5, 6 were

aeratedCecil (fine,kaolinitic, thermic Typic Kanhapludults), Altavista (fine-loamy, mixed, semiactive, thermic Aquic Hapludults), Helena (fine, mixed, semiactive, thermic Aquic Hapludults), and Sedgefield (fine, mixed, active, thermic, Aquultic Hapludalfs)

Rainfall Simulation - Scale 2 m2 Plots Cecil (fine, kaolinitic, thermic Typic Kanhapludults)

Treatments Nutient O = Control (none); B = Broiler Litter; D =

Dairy Slurry Aeration X = Control; N = No-till (disk); S = Spike;

C = CoreCore

No-till

Results Rainfall Simulation – Slit Aeration, 2 m2 Plots Altavista (fine-loamy, Aquic Hapludults)

Aerated Plots, fertilized with broiler litter attenuated more rainfall

Aeration alone did not affect cumulative mass losses of TKP, DRP, TKN, or NH4-N

Time (min runoff)

Results Rainfall Simulation – Slit Aeration, 2-m2 Plots Altavista (fine-loamy, Aquic Hapludults)

Footslope position attenuated twice as much runoff and Cumulative P

Landscape positionToeslope FootslopeBackslope Shoulder

Cum

ulat

ive

P Lo

ss (k

g P

ha-1

)

0

1

2

3

Cum

ulat

ive

Run

off (

mm

)

0

5

10

15

20

25

a

a

a

a a aa

aa

a a

aa

aa a

a

a

a a

a

b

b

5

30

10

510

30

ShoulderBackslope

FootslopeToeslope

Results Natural Rainfall – Slit Aeration, 0.8-ha Fields

Effect of aeration On Runoff volume varied

Well-drained soil aeration reduced runoff

Poorly-drained soil aeration increased runoff

Results Natural Rainfall – Slit Aeration, 0.8-ha Fields

Effect of aeration On DRP Loss VariedTKP similar to DRP

Well-drained soil aeration reduced P loss

Poorly-drained soil aeration increased P loss

DRP 6 = 0.03* + 1.40 DRP 3r2 = 0.91n = 56

DRP 6 = 0.29* + 1.47 DRP 3r2 = 0.75n = 19

DRP Loss Plot 3 - not aerated (kg P ha-1)

Before AerationAfter Aeration

Runoff 2 = 1.40 + 1.92* Runoff 1r2 = 0.90n = 37

Runoff 2 = 3.00 + 1.14* Runoff 1r2 = 0.75n = 9

DRP Loss Plot 4 - not aerated (kg P ha-1)

DRP Loss Plot 1 - not aerated (kg P ha-1)

0.0 0.5 1.0 1.5 2.0 2.5 3.0DR

P L

oss

Plo

t 5 -

aera

ted

(kg

P h

a-1)

0.0

0.5

1.0

1.5

2.0

DRP 5 = -0.02 + 0.59 DRP 4r2 = 0.92n = 53

DRP 5 = -0.02 + 0.64 DRP 4r2 = 0.94n = 19

b)

c)

Before

After

Before

After

0.0 0.2 0.4 0.6 0.8 1.0DR

P L

oss

Plo

t 2 -

aera

ted

(kg

P h

a-1)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

DRP 2 = 0.06 + 3.13* DRP 1r2 = 0.86n = 38

DRP 2 = 0.13 + 2.02* DRP 1

r2 = 0.79n = 21

0.0 0.5 1.0 1.5 2.0DR

P L

oss

Plo

t 6 -

aera

ted

(kg

P h

a-1)

0

1

2

3

Before AerationAfter Aeration

a)

Before

After

AfterBefore

DRP6 = 0.29** + 1.47 DRP 3r2 = 0.75n = 19

DRP6 = 0.03** + 1.40 DRP 3r2 = 0.91n = 56

Plot 6

Elevation (m)

153.0153.5154.0154.5155.0155.5156.0

Dep

th (c

m)

0

20

40

60

80

100

120

140

Bt StartsRedox Features StartBC Starts

Bt = Redox

Plot 5D

epth

(cm

)

0

20

40

60

80

100

120

140

Plot 2

Elevation (m)

153.0153.5154.0154.5155.0155.5156.0

Dep

th (c

m)

0

20

40

60

80

100

120

140

Results Natural Rainfall – Slit aeration, 0.8-ha Fields

Poorly-drained soils on which aeration exacerbated runoff and P losses had shallower: redoxomorphic features

Bt and Bc horizons

Line colors indicate: Black, depth Bt begins; Red, redox features begin; and green, BC begins

Results Rainfall Simulation – Slit, core and no-till Aeration, 2 m2 Plots, Cecil (fine, kaolinitic Typic Kanhapludults)

Core aeration reduced runoff volume when broiler litter was appliedNone of the mechanical aeration treatments tested reduced runoff when either dairy slurry or no amendments were applied

Time (min runoff)

Runoff volume

Broiler Litter Dairy Slurry No Manure

Run

off V

olum

e (%

of a

pplie

d ra

infa

ll)

0

10

20

30

40

50

60

Core Disk Slit No Aeration

a

bab

b

†

b. PostCmpct

NSNS

Results Rainfall Simulation – Slit, core and no-till Aeration, 2-m2 Plots, Cecil

Core aeration was most effective in reducing P losses in runoff for all P fractions measured

Core No-till Disk Slit None

P e

xpor

t (kg

P h

a-1 )

0

1

2

3

4TKP** TDP** DRP** TBAP** DBAP**

69%

64% 77

%52

%

78%

72% 81

%60

%

91%

82%

84%

63%

90%

82%

79%

63%

Broiler litter, PreCmpct

b† a a ac b ab ac b ab ab a a ab a a a

Results Rainfall Simulation – Slit, core and no-till Aeration, 2-m2 Plots, Cecil

Soils were compacted to simulate cattle grazing

Again core aeration tended to out perform other mechanical aeration treatments on the well-drained Cecil soil

P Export

Core No-till Disk Slit None

P e

xpor

t (kg

P h

a-1 )

0.0

0.5

1.0

1.5

2.0

2.5

3.0Broiler litter, After Compaction

b† a ab aba ab abb

TKP‡ DRP†

SoiL P

Continued P adsorption and relatively low levels of soil P suggest that soil still has further capacity to adsorb P

Broiler Litter Dairy Slurry No Manure

Meh

lich

I Soi

l P (m

g P

kg-1

)

0

10

20

30

40

50

60

70

Baseline PreCmpct PostCmpct

b

b

a

b

c

a

NS

Total suspended sediments

Broiler Litter Dairy Slurry No Manure

Tota

l Sus

pend

ed S

olid

s (k

g ha

-1)

0

50

100

150

200

250

300

Core Disk Slit No Aeration

a

bb

b

†

a. PreCmpctNS

NS

Broiler Litter Dairy Slurry No ManureTo

tal S

uspe

nded

Sol

ids

(kg

ha-1

)

0

50

100

150

200

250

300

Core Disk Slit No Aeration

a bab b

†

b. PostCmpct

NS NS

Conclusions Results varied depending on soils and drainage

class Small Plot Studies

Aerated Plots, fertilized with broiler litter attenuated more rainfall

Footslope position attenuated more rainfall than the shoulder, backslope or toeslope

Core aeration reduced TKP (46%) and DRP ( 62%) from plots fertilized with broiler litter

Core aeration lost significantly less dissolved P fractions (TDP and DRP) than no aeration, slit or no-till aeration

Conclusions Results varied depending on soils

and drainage class

Field Scale Study On fields with well-drained soils, aeration

reduced DRP losses (35%) Aeration exacerbated runoff and P losses in

poorly-drained soils