1. How long does it take for lime to work?
Since water is required for
lime to react with the soil, effects of a lime application will be slower in a
dry soil. It often takes a year or more before a response can be measured even under
perfect conditions. However, a response may be observed within weeks of the
application when soil pH is extremely low. It is important to apply lime
immediately after the growing season or crop removal to allow lime to react,
correcting soil pH before the next growing season.
The reactivity time also
depends on the type of lime used. Liming materials differ widely in their
neutralizing powers due to variations in the percentage of calcium and/or
magnesium. Usually, liming materials with a high calcium carbonate equivalent
(CCE) tend to neutralize soil acidity faster than those with a low CCE.
The coarseness of the liming material will also influence how fast the lime
will react. In other words, the finer the liming material, the greater the surface
area, resulting in faster reactivity.
2.
How little or how much lime can be applied at one time?
The amount of lime needed
depends on the type of crop being grown.
If growing continuous wheat or
bermudagrass, it is only necessary to raise the soil pH above 5.5. Therefore,
one-half ton or 25 percent of the soil test deficiency amount required to raise
the soil pH to 6.8 is recommended. If growing legumes, the soil pH needs to be
raised to 6.8. If surface applying lime, apply no more than two and one-half
tons per acre per year. Up to four tons per acre may be applied if the lime is
worked into the soil. In situations where soil pH is extremely low and a large
amount of lime is recommended, it may be a good idea to spread the cost over
two to three years by annually applying one-third or half of the lime needed.
3.
Should lime be worked into the soil or placed on the surface?
Whenever possible, tillage
should be used as a tool to incorporate lime into the soil. When lime is worked
into the soil, a larger portion of its surface area is exposed to the soil
allowing for faster reactivity.
Lime applied on the soil
surface does not react as fast as lime incorporated by tillage, but what other
option is there in perennial pasture systems? Surface-applied lime moves into the
soil at a slow rate.
It is similar to non-mobile
nutrients in its movement in the soil. However, there are a few crops that have
roots that feed close to the soil surface, such as bermudagrass and alfalfa. It
has been documented that correcting pH in the top two to three inches of the
soil has a positive effect on forage production. Even though it is best to
incorporate lime whenever possible, it is still important to surface-apply lime
to correct the soil acidity problem in established pastureland and no-till
cropping systems.
4.
Does liming have an effect on herbicide activity?
There are several herbicide
families that are soil pH dependent. For example, low soil pH levels may reduce
the activity or residual time of triazine (atrazine, Sencor) and sulfonylurea
(Peak) herbicides. High soil pH levels (>6.8) tend to increase herbicide
activity that increases the risk of crop injury and/or carryover potential.
5.
What effect do different tillage systems have on soil pH?
All lime calculations are
based on neutralizing the acidity in the top six inches of soil. As a result,
different tillage systems affect soil acidity. A conventional tillage system
involves several tillage passes over the field prior to planting. If the
subsoil is calcareous, deep tillage may mix enough subsoil into the top six
inches to maintain soil pH at the surface. Conventional tillage systems allow
the opportunity to thoroughly mix applied lime prior to the next growing
season. A conservation tillage system is not as aggressive as conventional.
Fewer tillage passes may be implemented prior to planting, leaving greater than
30 percent crop residue on the soil surface. As a result, there is a limited
amount of soil mixing. It is critical to closely monitor soil pH in no-till
systems since most lime and dry fertilizer is surface-applied. Over time, the
top inch of soil may become extremely acidic due to the surface application of
fertilizer. However, soil surface pH can also become too high if a large amount
of lime is applied at one time and left on the soil surface. It is best to
apply small amounts of lime more frequently to maintain soil pH in a no-till
system.
6.
Are dolomitic sources of lime better than calcitic?
In general, soils in Oklahoma
and north Texas are not deficient in magnesium. Therefore, the use of dolomitic
lime to increase soil magnesium levels is not important. Dolomitic lime may be
recommended in pastures that have a history of grass tetany to raise forage
magnesium levels. Both calcitic and dolomitic lime sources work well in raising
soil pH. In our region, it is more important to look at the cost effectiveness
rather than the source.
7.
What are the advantages and disadvantages of liquid lime verses dry lime?
Liquid lime is a formulation
of approximately 50 percent high quality dry Ag lime (usually greater than 90
percent) and 50 percent H2O. It has the advantage of providing
better uniformity of spread over the field in comparison to dry lime. There are
three main disadvantages of liquid lime. First, there are normally higher
operational costs since you must haul both water and lime across the field.
Secondly, under-liming is more likely to occur with liquid lime due to spread
rate. Finally, more frequent lime applications are often needed since liquid
lime reacts quicker than a dry lime source, but the rate may not be high enough
to correct all the reserve acidity. One must be very careful of the rate at
which liquid lime is applied. It is appealing to the producer because of its
fast reaction time and uniformity advantages.
It is important to know how
much active ingredient or neutralizing power that you are paying for.
8.
What is the cost effectiveness of liquid lime products versus agricultural lime?
To make a decision about the
cost effectiveness of these two products, one must compare both the total
neutralizing power/unit weight of each and the cost/unit weight of each. This
area can quickly become rather complicated.
If you have any questions in
comparing the cost of liquid and dry lime, we would be more than glad to
provide assistance.
9.
Why is the difference in soil pH and buffer pH on the soil test report?
pH is an unbuffered measure of
the hydrogen ion concentration in the soil (active acidity) whereas buffer pH
is a measurement of total soil acidity (active + reserve acidity). Soils with
low buffering capacities (low cation exchange capacity or CEC) usually have
less total acidity than soils with a high CEC if the pH is the same. Therefore,
it takes less lime to correct the total acidity in a soil with a low CEC. The
buffer pH on the soil test report is used to calculate how much lime is needed
to correct both the active and reserve acidity. When soil pH is 6.5 or greater,
the buffer index will not be reported on the soil test report due to its
irrelevance.
10.
How often should I apply lime?
The answer to this question
depends on a variety of considerations. A soil with a low CEC does not require
a lot of lime to correct soil pH, but may need to be limed frequently. A soil
with a high CEC requires a large amount of lime to initially correct pH, but it
may be several years before another lime application is needed due to its high
buffering capacity. The level of production also dictates how often lime will
be needed. As fertilizer is applied to enhance forage or crop production, the
removal of essential plant nutrients from the soil also increases. As a result,
lime may be needed more frequently to replenish removed nutrients. For example,
the rate of nutrient removal from a pasture being hayed is much greater than a pasture
being grazed. Therefore, the hay field may need to be limed more often.
by
Jeff Ball
1. How long does it take for lime to work?
Since water is required for
lime to react with the soil, effects of a lime application will be slower in a
dry soil. It often takes a year or more before a response can be measured even under
perfect conditions. However, a response may be observed within weeks of the
application when soil pH is extremely low. It is important to apply lime
immediately after the growing season or crop removal to allow lime to react,
correcting soil pH before the next growing season.
The reactivity time also
depends on the type of lime used. Liming materials differ widely in their
neutralizing powers due to variations in the percentage of calcium and/or
magnesium. Usually, liming materials with a high calcium carbonate equivalent
(CCE) tend to neutralize soil acidity faster than those with a low CCE.
The coarseness of the liming material will also influence how fast the lime
will react. In other words, the finer the liming material, the greater the surface
area, resulting in faster reactivity.
2.
How little or how much lime can be applied at one time?
The amount of lime needed
depends on the type of crop being grown.
If growing continuous wheat or
bermudagrass, it is only necessary to raise the soil pH above 5.5. Therefore,
one-half ton or 25 percent of the soil test deficiency amount required to raise
the soil pH to 6.8 is recommended. If growing legumes, the soil pH needs to be
raised to 6.8. If surface applying lime, apply no more than two and one-half
tons per acre per year. Up to four tons per acre may be applied if the lime is
worked into the soil. In situations where soil pH is extremely low and a large
amount of lime is recommended, it may be a good idea to spread the cost over
two to three years by annually applying one-third or half of the lime needed.
3.
Should lime be worked into the soil or placed on the surface?
Whenever possible, tillage
should be used as a tool to incorporate lime into the soil. When lime is worked
into the soil, a larger portion of its surface area is exposed to the soil
allowing for faster reactivity.
Lime applied on the soil
surface does not react as fast as lime incorporated by tillage, but what other
option is there in perennial pasture systems? Surface-applied lime moves into the
soil at a slow rate.
It is similar to non-mobile
nutrients in its movement in the soil. However, there are a few crops that have
roots that feed close to the soil surface, such as bermudagrass and alfalfa. It
has been documented that correcting pH in the top two to three inches of the
soil has a positive effect on forage production. Even though it is best to
incorporate lime whenever possible, it is still important to surface-apply lime
to correct the soil acidity problem in established pastureland and no-till
cropping systems.
4.
Does liming have an effect on herbicide activity?
There are several herbicide
families that are soil pH dependent. For example, low soil pH levels may reduce
the activity or residual time of triazine (atrazine, Sencor) and sulfonylurea
(Peak) herbicides. High soil pH levels (>6.8) tend to increase herbicide
activity that increases the risk of crop injury and/or carryover potential.
5.
What effect do different tillage systems have on soil pH?
All lime calculations are
based on neutralizing the acidity in the top six inches of soil. As a result,
different tillage systems affect soil acidity. A conventional tillage system
involves several tillage passes over the field prior to planting. If the
subsoil is calcareous, deep tillage may mix enough subsoil into the top six
inches to maintain soil pH at the surface. Conventional tillage systems allow
the opportunity to thoroughly mix applied lime prior to the next growing
season. A conservation tillage system is not as aggressive as conventional.
Fewer tillage passes may be implemented prior to planting, leaving greater than
30 percent crop residue on the soil surface. As a result, there is a limited
amount of soil mixing. It is critical to closely monitor soil pH in no-till
systems since most lime and dry fertilizer is surface-applied. Over time, the
top inch of soil may become extremely acidic due to the surface application of
fertilizer. However, soil surface pH can also become too high if a large amount
of lime is applied at one time and left on the soil surface. It is best to
apply small amounts of lime more frequently to maintain soil pH in a no-till
system.
6.
Are dolomitic sources of lime better than calcitic?
In general, soils in Oklahoma
and north Texas are not deficient in magnesium. Therefore, the use of dolomitic
lime to increase soil magnesium levels is not important. Dolomitic lime may be
recommended in pastures that have a history of grass tetany to raise forage
magnesium levels. Both calcitic and dolomitic lime sources work well in raising
soil pH. In our region, it is more important to look at the cost effectiveness
rather than the source.
7.
What are the advantages and disadvantages of liquid lime verses dry lime?
Liquid lime is a formulation
of approximately 50 percent high quality dry Ag lime (usually greater than 90
percent) and 50 percent H2O. It has the advantage of providing
better uniformity of spread over the field in comparison to dry lime. There are
three main disadvantages of liquid lime. First, there are normally higher
operational costs since you must haul both water and lime across the field.
Secondly, under-liming is more likely to occur with liquid lime due to spread
rate. Finally, more frequent lime applications are often needed since liquid
lime reacts quicker than a dry lime source, but the rate may not be high enough
to correct all the reserve acidity. One must be very careful of the rate at
which liquid lime is applied. It is appealing to the producer because of its
fast reaction time and uniformity advantages.
It is important to know how
much active ingredient or neutralizing power that you are paying for.
8.
What is the cost effectiveness of liquid lime products versus agricultural lime?
To make a decision about the
cost effectiveness of these two products, one must compare both the total
neutralizing power/unit weight of each and the cost/unit weight of each. This
area can quickly become rather complicated.
If you have any questions in
comparing the cost of liquid and dry lime, we would be more than glad to
provide assistance.
9.
Why is the difference in soil pH and buffer pH on the soil test report?
pH is an unbuffered measure of
the hydrogen ion concentration in the soil (active acidity) whereas buffer pH
is a measurement of total soil acidity (active + reserve acidity). Soils with
low buffering capacities (low cation exchange capacity or CEC) usually have
less total acidity than soils with a high CEC if the pH is the same. Therefore,
it takes less lime to correct the total acidity in a soil with a low CEC. The
buffer pH on the soil test report is used to calculate how much lime is needed
to correct both the active and reserve acidity. When soil pH is 6.5 or greater,
the buffer index will not be reported on the soil test report due to its
irrelevance.
10.
How often should I apply lime?
The answer to this question
depends on a variety of considerations. A soil with a low CEC does not require
a lot of lime to correct soil pH, but may need to be limed frequently. A soil
with a high CEC requires a large amount of lime to initially correct pH, but it
may be several years before another lime application is needed due to its high
buffering capacity. The level of production also dictates how often lime will
be needed. As fertilizer is applied to enhance forage or crop production, the
removal of essential plant nutrients from the soil also increases. As a result,
lime may be needed more frequently to replenish removed nutrients. For example,
the rate of nutrient removal from a pasture being hayed is much greater than a pasture
being grazed. Therefore, the hay field may need to be limed more often.
by
Jeff Ball
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