influence of aeration implements, amendment and soil taxa on phosphorus losses in grasslands d.h....
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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 position
Toeslope FootslopeBackslope Shoulder
Cu
mu
lati
ve P
Lo
ss (
kg P
ha-
1 )
0
1
2
3
Cu
mu
lati
ve R
un
off
(m
m)
0
5
10
15
20
25
a
a
a
a a aa
aa
a a
a
a
aa
aa
a
a a
a
b
b
5
30
10
510
30
Shoulder
Backslope
Footslope
Toeslope
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 3
r2 = 0.91n = 56
DRP 6 = 0.29* + 1.47 DRP 3
r2 = 0.75n = 19
DRP Loss Plot 3 - not aerated (kg P ha-1)
Before AerationAfter Aeration
Runoff 2 = 1.40 + 1.92* Runoff 1
r2 = 0.90n = 37
Runoff 2 = 3.00 + 1.14* Runoff 1
r2 = 0.75
n = 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 -
ae
rate
d (
kg P
ha
-1)
0.0
0.5
1.0
1.5
2.0
DRP 5 = -0.02 + 0.59 DRP 4
r2 = 0.92n = 53
DRP 5 = -0.02 + 0.64 DRP 4
r2 = 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 -
ae
rate
d (
kg P
ha
-1)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
DRP 2 = 0.06 + 3.13* DRP 1
r2 = 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 -
ae
rate
d (
kg P
ha
-1)
0
1
2
3
Before AerationAfter Aeration
a)
Before
After
AfterBefore
DRP6 = 0.29** + 1.47 DRP 3
r2 = 0.75n = 19
DRP6 = 0.03** + 1.40 DRP 3
r2 = 0.91n = 56
Plot 6
Elevation (m)
153.0153.5154.0154.5155.0155.5156.0
Dep
th (
cm)
0
20
40
60
80
100
120
140
Bt StartsRedox Features StartBC Starts
Bt = Redox
Plot 5
Dep
th (
cm)
0
20
40
60
80
100
120
140
Plot 2
Elevation (m)
153.0153.5154.0154.5155.0155.5156.0
Dep
th (
cm)
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 applied
None 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
b
abb
†
b. PostCmpct
NS
NS
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 (k
g P
ha-
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
Me
hlic
h I
So
il 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
Tot
al S
uspe
nded
Sol
ids
(kg
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 ManureT
otal
Sus
pend
ed S
olid
s (k
g 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
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