1. Soil pH and SMP Buffer pH methodologies a.Time for SMP buffer to set in soil-water slurry b....
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Transcript of 1. Soil pH and SMP Buffer pH methodologies a.Time for SMP buffer to set in soil-water slurry b....
1. Soil pH and SMP Buffer pH methodologies
a. Time for SMP buffer to set in soil-water slurry
b. Conditions on LabFit for soil pH and Sikora buffer pH
2. Laboratory survey on pH and lime recommendations
prepared for SERA-6 conferenceJune 4-5, 2007
F.J. SikoraUniversity of Kentucky
Soil pH and buffer pH methodology:water and SMP/Sikora buffer reaction time
with soil and a laboratory survey
Variations in methods for determining 1:1 soil:water pH
Reference pub
Quantity of soil
Stirring (or mixing) time after adding
water
Standing time before determining
pH
Stirring during/before pH measurement
SPAC, Inc. 4.25 cm3, 5 g, or 10 cm3
Stir for 5 sec 10 min stir during pH measurement
Southern 10 cm3 Mix for 5 sec 30 min stir soil suspension by swirling the cup slightly just
prior to reading pH
Northeastern Scoop 5 cm3 or weigh 5 g
Stir vigorously for 15 sec
30 min place electrodes in the slurry, swirl carefully and
read pH immediately
North Central
4.25 cm3
(5 g scoop)Stir
vigorously for 5 sec
10 min place electrodes in the slurry, swirl carefully and
read pH immediately
Western 5 0.1 g Stir thoroughly for 5 sec
15 min place electrodes in the slurry, swirl carefully and
read pH immediately
Variations in SMP methods for determining buffer pH
Reference pub
Quantity of soilVolume of buffer added to soil pH
slurry and shaking time
Oscillations/minStanding time
before determining
pH
SPAC, Inc. 4.25 cm3 or 5 g 10 mL buffer, shake for 10 min
(or 15 min)
>180 30 min (or 15 min)
Southern
Northeastern Scoop 5 cm3 or weigh 5 g
10 mL buffer, shake for 10 min
(or 15 min)
250 30 min (or 15 min)
North Central 4.25 cm3
(5 g scoop)10 mL buffer, shake
for 10 min (or 15 min)
250 30 min (or 15 min)
Western 5 0.1 g 10 mL buffer, stir every 5 minutes for
20 min
20 min
Mclean, Eckert, Reddy, and Trierweiler. 1978. An improved SMP soil lime requirement method incorporating double-buffer and quick-test features. SSSAJ 42:311-316.
excerpt from
1975 North Central publicationon soil test methods.
Lexington Quality Control Sample 4108
6.3
6.4
6.5
6.6
6.7
6.8
6.9
7.0
0 50 100 150 200 250 300 350 400 450 500 550
Days after Jan 1, 2005
Bu
ffer
pH
- 2 s
- 3 s
+ 3 s
+ 2 s
SMP buffer
mean
Sikora buffer
stirring time for buffer in soil
time buffer set in soil prior to measurement
LabFit method with Sikora buffer
0.33 min.±0.11
37 min.±4
1.5 hrsfor 3 trays(n=120)
Method for adding water to soil
Each sample stirred with stir rod and let set for 30 min.
y = 0.9613x + 0.1576
R2 = 0.9763
4
5
6
7
8
9
10
4 5 6 7 8 9 10
water pH, old way
water
pH,
new
inst
r
5,10
y = 1.0486x - 0.4033
R2 = 0.9607
5
5.5
6
6.5
7
7.5
8
5 5.5 6 6.5 7 7.5 8
SMP buffer pH, old way
KY b
uffer
pH,
new
inst
r
5,10
Sik
ora
Buf
fer
pH,
LabF
it in
stru
men
t
Soi
l pH
, La
bFit
inst
rum
ent
Soil pH, NAPT median SMP Buffer pH, NAPT median
Soil pH Buffer pH
1:1 line
regression line
y = 0.8927x + 0.6065
R2 = 0.9647
4
5
6
7
8
9
10
4 5 6 7 8 9 10
water pH, old way
water
pH,
new
instr
5,10 tray swilred
y = 0.9613x + 0.1576
R2 = 0.9763
4
5
6
7
8
9
10
4 5 6 7 8 9 10
water pH, old way
water
pH,
new
inst
r
5,10
Soi
l pH
, La
bFit
inst
rum
ent
Soi
l pH
, La
bFit
inst
rum
ent
Soil pH, NAPT median Soil pH, NAPT median
Each sample stirred with stir rod for 5 sec and let set for 30 min.
Tray swirled for 5 sec. and let set for 30 min.
1:1 line
regression line
Soil pH
A Mid-Atlantic Soil Testing and Plant Analysis Work Group survey on methods for
soil pH, buffer pH and lime recommendations
Objectives are to assess:
1. variation in lab methods being used.
2. effect of method variation on intra- and interlaboratory error.
3. variation in how lime recommendations are made.
& SERA6
0
0.05
0.1
0.15
0.2
0.25
9811
3
9812
3
9910
9
9911
9
_001
09
_001
19
_011
09
_011
19
2002
109
2002
119
2003
109
2003
119
2004
109
2004
119
2005
009
2005
019
2006
009
2006
019
Soil pH MAD values in the NAPT program
SMP Buffer pH MAD values in the NAPT program
0
0.05
0.1
0.15
0.2
0.25
9811
3
9812
3
9910
9
9911
9
_001
09
_001
19
_011
09
_011
19
2002
109
2002
119
2003
109
2003
119
2004
109
2004
119
2005
009
2005
019
2006
009
2006
019
y = -0.837 x + 7.00
r 2 = 0.658
y = -0.803x + 6.347
R2 = 0.691
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
5 5.5 6 6.5 7 7.5 8
SMP buffer pH
Co
eff
icie
nt
of
Va
ria
tio
n (
%)
y = -0.1749x + 2.6093
R2 = 0.1805
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4 5 6 7 8 9 10
water pH
Co
eff
icie
nt
of
Va
ria
tio
n (
%)
Variations in methods for Mehlich III extractable nutrients
Reference pub
Quantity of soil Volume of Mehlich III Mixing time and method
SPAC, Inc. 5 cm3 50 mL 5 min on reciprocating shaker
Southern 2.5 cm3 25 mL 5 min on reciprocating shaker
Northeastern Scoop 2.5 cm3
or 2.5 g(references orig. method on 10:1
ratio based on vol.)
25 mL 5 min on reciprocating shaker
at 200 epm
North Central
1.7 cm3
(2 g scoop)20 mL 5 min on shaker at
200 or more epm between 24 to 27oC
Western 2 0.05 g 20 mL 5 min on reciprocating shaker