soil amendments on northern plains - agvise laboratories · soil amendments on northern plains...
TRANSCRIPT
Soil Amendments on
Northern Plains
• Many soils in Northern Plains have high pH
(>7.3) and high salinity (salts)
• Farmers know these issues may reduce yields
and are always looking for the “easy button” to
“fix” these issues.
• Some people tell farmers a couple hundred
pounds of soil amendments can “fix” these
issues
• Elemental sulfur and gypsum are often
mentioned in these claims.
Soil Amendments
to reduce Soil pH
• If you could lower a soil pH from 8.0 to about
7.0 and keep it there, the availability of
nutrients, like phosphorus, will increase.
• Reducing pH (along with carbonates) may
also reduce IDC in soybeans.
• Will a couple hundred pounds of elemental
sulfur or gypsum lower soil pH?
Soil pH – Availability of Nutrients
Lowering soil pH may increase nutrient availability. (Soils
with free calcium carbonate have pH around 7.5 - 8.2.)
AGVISE – Soil Amendment
Project 2005-2017
• 10,000 lb/a Elemental Sulfur
Can 10,000 lb Elemental S
Lower Soil pH?
2S + 3O2 + 2H2O
Sulfur + Oxygen + Water Sulfuric Acid
Elemental sulfur must be mixed with moist, warm aerated
soil with bacteria (Thiobacillus) for this reaction to occur. The
hydrogen (H+) from the sulfuric acid lowers pH. If soil
contains carbonates (pH higher than 7.3), it will require very
high rates of sulfur to change pH permanently.
2H2SO4
H+ H+
Does Elemental Sulfur Lower Soil pH?
8.0
7.57.6 7.6 7.6
7.77.8 7.8 7.8 7.8
7.77.8 7.8 7.8
6
6.5
7
7.5
8
8.5
9
4-05 9-05 9-06 10-07 9-08 09-09 08-10 11-11 10-12 10-13 10-14 10-15 10-16 10-17
So
il p
H
Soil (CCE) Carbonate level is 1.5%, loam soil texture
10,000 lb/a elemental Sulfur tilled into soil April-2005
YES, but rate must be high and change may not be permanent
pH range with highest available P
70%
81%75%
50%
40%
61%
71%
85%
89%
41%
57%43%
76% 86%
84%81%
64%72%
% Soil samples with carbonate greater than 1.0%
Fall 2017 samples
(0-6” samples)
MB
ND
SDMN
88%
63%20%
73%
98%
75%
58%
39%
34%
54%
For most soils in this region, it is impossible to lower pH because carbonate will
neutralize acid.
• Reduced by 0.5 pH unit in first year, then
increased to near original pH.
• Calcium carbonate in soil was not completely
neutralized by elemental sulfur, so pH change
was not permanent and went back up.
• Since 10,000 lb of elemental S was not
enough to lower pH in 12 years, maybe we
will increase rate to 100,000 lb elemental S
next time!
• Couple hundred pounds won’t do it!!!
Effect of 10,000 lb Elemental
Sulfur on Soil pH
Farmers would like to lower
Salinity too! Can Elemental Sulfur
do that? (Soybeans would benefit)
Soybean tolerance to salinity (EC 1:1 method)
(NDSU, 2016).
1.71.9
2.11.8
2 2.3 2.4 2.3 2.32.1
2.3 2.22.4 2.5
0
0.5
1
1.5
2
2.5
3
3.5
4
4-05 9-05 9-06 10-07 09-08 09-09 08-10 11-11 10-12 10-13 10-14 10-15 10-16 10-17
mm
ho
s/c
m (
rou
tin
e 1
:1 s
alt
test)
Sulfur 10000
Does 10,000 lb/a Elemental
Sulfur Reduce Soluble Salts?
No – Salinity has gone up!
Effect of 10,000 lb Elemental
Sulfur on Salinity
• Salinity increased over time.
• Elemental sulfur reacted with calcium
carbonate (CaCO3) in soil to form gypsum
(CaSO4), which caused the salinity to
increase to about 2.2 mmhos/cm (conductivity
of saturated gypsum solution).
• Elemental S did not lower salinity in 12 years.
Salinity actually increased as we expected.
• Elemental S will not reduce salinity (salts).
AGVISE – Soil Amendment
Project 2005-2017
• 5,000 Gypsum
CaSO4
Does 5000 lb/a Gypsum (CaSO4)
Decrease Soil pH?
8.07.8 7.8 7.9 7.8 7.8 7.9 7.9 7.9 8.0 7.9 7.9 8.0
7.8
6
6.5
7
7.5
8
8.5
9
4-05 9-06 9-08 08-10 10-12 10-14 10-16
So
il p
H
5000 lb/a Gypsum tilled into top 6” of soil - April 2005
Loam Soil texture, Carbonate level (CCE) = 1.5%, poorly drained
No – pH has not changed!
Gypsum slowly dissolves
No chemical reaction to
change pH (No H+)
CaSO4•2H2O Ca2+ + SO42- + 2H2O
Gypsum calcium + sulfate + water
No H+ produced when gypsum slowly dissociates
into calcium and sulfate ions in the soil solution.
If no hydrogen (acid) is created, the soil pH
should not change!
Can Gypsum Lower Soluble Salts?
1.11.3
1.7
1.21.4
1.61.9
1.3 1.4
0.8
1.2 1.10.8
1.5
0
0.5
1
1.5
2
2.5
3
3.5
4
4-05 9-05 9-06 10-07 9-08 09-09 08-10 08-11 10-12 10-13 10-14 10-15 10-16 10-17
Sali
nit
y m
mh
os/c
m (
1:1
)
5000 lb/a Gypsum tilled into soil 4-26-2005
No! – Salinity has gone up and down with
normal variation based on precipitation
Effect of 5,000 lb Gypsum
on Salinity• Salinity varied over time corresponding to wet
and dry years, showing the role of water
movement on changing salinity level from
year to year.
• Gypsum is a slowly soluble salt that dissolves
in the soil solution. It dissociates into ions
which actually increase soil salinity.
• Gypsum did not lower the salinity in 12 years.
• Gypsum is not a useful amendment for
lowering soil salinity. Yet, it can be useful for
soils with high sodium.
• Apply more P fertilizer in bands
• Apply higher rates of P fertilizer
• Building P soil test levels is not easy in high
pH soils, but it is much less expensive than
trying to reduce the soil pH
• For IDC – (high pH soils with carbonates)
– IDC varieties, wide rows, Fe-EDDHA
What are viable alternatives?
Soil Amendments can’t
economically lower soil pH?
• Include more high water use crops in
rotation to lower the water table
– Corn, sunflower, alfalfa
• Keep something growing all season
– Cover crops, perennial grasses
• Improve surface drainage
• Tile drainage
What are viable alternatives?
Soil Amendments can’t
economically reduce salinity?
Tile drainage “can” lower salinity(along with crop rotations that use much water)
0
0.5
1
1.5
2
2.5
3
3.5
4
02 03 04 05 06 07 08 09 10 11 12 13 15 16 16 2017
Site 2 Site 5
Solu
ble
Sal
ts (
e.c.
mm
ho
s/cm
1:1
met
ho
d)
AGVISE Tile drainage Demo Project 2002-2017
Soil amendment “Myths” are here to stay!
Human nature is to look for the “easy button”
Lowering soil pH and salinity will
never be easy or inexpensive!
Beware promises of products saying this will be easy!
Demo project 2018
Liming very acid no-till fields
• Cooperators and sites needed
• Long-term no-till (10 plus years)
• Low pH topsoil (less than 6.0)
• Low pH subsoil (less than 6.5)
We will be applying lime and tracking effect of lime
through the topsoil over time. Incremental
sampling 0-2”, 2-4”, 4-6” testing pH and nutrients
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