acidity and availability of nutrients
 

hello,
1. i know that calcium is *unAvailable* in acidic environments and
wonder whether or what other plant nutrients are affected by pH
2. if i was using acidic tap water (with vinegar) in fairly neutral pH
soil, are the nutrients permanently bound by the acidity or would they
become available once hitting the neutral soil
(the water WAS ~ pH 5 perhaps less)
thanks in advance!

acidity and availability of nutrients
 

Tanya wrote in message ...
hello,
1. i know that calcium is *unAvailable* in acidic environments and
wonder whether or what other plant nutrients are affected by pH
2. if i was using acidic tap water (with vinegar) in fairly neutral pH
soil, are the nutrients permanently bound by the acidity or would they
become available once hitting the neutral soil
(the water WAS ~ pH 5 perhaps less)
thanks in advance!

Tanya,
Yes, a lot of nutrients are affected by pH. At low pH calcium,
magnesium, potassium etc. will all be decreased, while some toxic
elements like aluminium will increase.
Soil is very dynamic, and if you change the pH elemental availability
will change. However, if you keep pouring vinegar (ie acid rain!) onto
soil you will leach out a lot of the positive ions permanently and
replace them with hydrogen ions, and they will go into the drainage
water.
It all gets rather complex chemistry!
Best Wishes,
Martin

Dr Martin J. Hodson,
Principal Lecturer in Environmental Biology,
School of Biological and Molecular Sciences,
Oxford Brookes University,
Gipsy Lane, Headington,
Oxford, OX3 0BP, UK

Tel.: ++44 (0)1865 483954
Fax: ++44 (0)1865 483242
Email:
Web: http://www.hodsons.org/MartinHodson/

acidity and availability of nutrients
 

Low pH means there is a higher concentration of hydrogen ions (H+)
than at higher pH. Calcium is present in neutral to acid soils mainly
as calcium ion (Ca++). At soil pH 8.3 and above, soils also contain
solid calcium carbonate. In neutral to acid soils, most Ca++ is held
by negative charges on soil minerals and organic particles. The
negative charges that hold positively charged ions is termed the CEC
or cation exchange capacity. Potassium ions (K+) and magnesium ions
(Mg++) are also held mainly on the CEC. At soil pH declines, hydrogen
ions (H+) displace Ca++, Mg++ and K+ from the negative sites into the
soil solution. This is termed cation exchange. The Ca++, Mg++ and K+
are then usually leached out of the rootzone.

Soil pH is usually raised by adding limestone or calcium carbonate
(CaCO3). The Ca++ displaces H+ from the cation exchange sites. Two H+
combine with CO3-- to form H2CO3 or carbonic acid. The carbonic acid
breaks apart to form CO2 and H2O so the H+ are neutralized. Liming is
also done using dolomitic limestone which contains MgCO3 and CaCO3, so
supplies magnesium and calcium.

Using acidic tapwater may take a long time to lower the pH of a
neutral soil (pH of 7). Clay soils especially are well-buffered
against pH changes.

The availability of all mineral nutrients are affected by soil pH, but
they are not all affected the same way. For example, iron, zinc,
copper and manganese availability are usually greater in acid soils
than in neutral and basic soils. For these mineral nutrients, pH is
mainly affecting solubility. The solubility of iron (Fe+++) increases
1,000 times for each decrease of one pH unit.

For nitrogen, pH mainly affects bacterial growth. Most soil nitrogen
is in organic matter. Soil bacteria are adversely affected by low pH.
At low pH, bacteria decompose less organic matter, which means less
nitrogen is made available to plants.


Reference

Graph of soil pH and nutrient availablity:
http://www.extension.umn.edu/distrib...s/1731-03.html




Tanya wrote in message ...
hello,
1. i know that calcium is *unAvailable* in acidic environments and
wonder whether or what other plant nutrients are affected by pH
2. if i was using acidic tap water (with vinegar) in fairly neutral pH
soil, are the nutrients permanently bound by the acidity or would they
become available once hitting the neutral soil
(the water WAS ~ pH 5 perhaps less)
thanks in advance!

acidity and availability of nutrients
 

Martin Hodson wrote:

Tanya wrote in message ...
hello,
1. i know that calcium is *unAvailable* in acidic environments and
wonder whether or what other plant nutrients are affected by pH
2. if i was using acidic tap water (with vinegar) in fairly neutral pH
soil, are the nutrients permanently bound by the acidity or would they
become available once hitting the neutral soil
(the water WAS ~ pH 5 perhaps less)
thanks in advance!

Tanya,
Yes, a lot of nutrients are affected by pH. At low pH calcium,
magnesium, potassium etc. will all be decreased, while some toxic
elements like aluminium will increase.
Soil is very dynamic, and if you change the pH elemental availability
will change. However, if you keep pouring vinegar (ie acid rain!) onto
soil you will leach out a lot of the positive ions permanently and
replace them with hydrogen ions, and they will go into the drainage
water.
It all gets rather complex chemistry!
Best Wishes,
Martin

Dr Martin J. Hodson,
Principal Lecturer in Environmental Biology,
School of Biological and Molecular Sciences,
Oxford Brookes University,
Gipsy Lane, Headington,
Oxford, OX3 0BP, UK

Tel.: ++44 (0)1865 483954
Fax: ++44 (0)1865 483242
Email:
Web: http://www.hodsons.org/MartinHodson/

hello,
i want to thank you VERY much for the reply!
fwiw, the plants that receivED (i've stopped) the vinegar-water *do* appear to have deficiencies
which resemble magnesium or calcium (or K+)
thanks again!
sincerely
Tanya

acidity and availability of nutrients
 

Hello,
thanks so much for the reply and Web site!
(the vinegar was not doing much if anything to the pH... i have since stopped)
again, greatly appreciate your response!
sincerely
Tanya

David Hershey wrote:

Low pH means there is a higher concentration of hydrogen ions (H+)
than at higher pH. Calcium is present in neutral to acid soils mainly
as calcium ion (Ca++). At soil pH 8.3 and above, soils also contain
solid calcium carbonate. In neutral to acid soils, most Ca++ is held
by negative charges on soil minerals and organic particles. The
negative charges that hold positively charged ions is termed the CEC
or cation exchange capacity. Potassium ions (K+) and magnesium ions
(Mg++) are also held mainly on the CEC. At soil pH declines, hydrogen
ions (H+) displace Ca++, Mg++ and K+ from the negative sites into the
soil solution. This is termed cation exchange. The Ca++, Mg++ and K+
are then usually leached out of the rootzone.

Soil pH is usually raised by adding limestone or calcium carbonate
(CaCO3). The Ca++ displaces H+ from the cation exchange sites. Two H+
combine with CO3-- to form H2CO3 or carbonic acid. The carbonic acid
breaks apart to form CO2 and H2O so the H+ are neutralized. Liming is
also done using dolomitic limestone which contains MgCO3 and CaCO3, so
supplies magnesium and calcium.

Using acidic tapwater may take a long time to lower the pH of a
neutral soil (pH of 7). Clay soils especially are well-buffered
against pH changes.

The availability of all mineral nutrients are affected by soil pH, but
they are not all affected the same way. For example, iron, zinc,
copper and manganese availability are usually greater in acid soils
than in neutral and basic soils. For these mineral nutrients, pH is
mainly affecting solubility. The solubility of iron (Fe+++) increases
1,000 times for each decrease of one pH unit.

For nitrogen, pH mainly affects bacterial growth. Most soil nitrogen
is in organic matter. Soil bacteria are adversely affected by low pH.
At low pH, bacteria decompose less organic matter, which means less
nitrogen is made available to plants.

Reference

Graph of soil pH and nutrient availablity:
http://www.extension.umn.edu/distrib...s/1731-03.html

Tanya wrote in message ...
hello,
1. i know that calcium is *unAvailable* in acidic environments and
wonder whether or what other plant nutrients are affected by pH
2. if i was using acidic tap water (with vinegar) in fairly neutral pH
soil, are the nutrients permanently bound by the acidity or would they
become available once hitting the neutral soil
(the water WAS ~ pH 5 perhaps less)
thanks in advance!