Calcium
Calcium
has been identified as a major factor in facilitating
the uptake of other nutrients, particularly N and P,
as well as playing
a vital role in maintaining soil structure and plant physiology.
Soil
calcium levels have halved in the UK between the 1960's
and today, with many grassland and arable soils now being
deficient in available calcium as shown by Carrs Fertilisers
recent survey of soil calcium levels in the table below. |
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Almost
all of the soils sampled had calcium levels well below the optimum
of 1600 ppm (Index 2 - 3), with many as low as 600 ppm. The main
reasons for the decline in soil calcium are:
-
Reduction in lime applications since the removal of the lime subsidy
in 1976;
-
Change in emphasis from calcium ground limestone to magnesium
lime over the past twenty years;
-
Increase in anions such as nitrates and sulphates being leached
from the soil which often take calcium with them as the balancing
cation, e.g. for every 1 kg of nitrate N leached from the soil,
3 kgs of calcium are also lost.
Through
a series of experiments on both grassland and arable soils from
1987 - 1992, ADAS produced the following formula for calculating
the loss of calcium (measured as calcium carbonate, CaCO3) from
the soil:
e.g.
for a soil with a pH of 6.0, the estimated annual loss of calcium
carbonate from that soil would be:
(6.0
x 405) - 1790 = 640 kgs / ha CaCO3
Calcium (Ca) is 40% by weight of CaCO3 therefore the loss of calcium
from a soil of pH 6.0 is 640 x 40% = 256 kgs / ha.
By
analysing soil calcium levels and applying the above formula it
is possible to demonstrate to farmers the need for additional calcium.
'New Choice' contains available calcium to satisfy annual requirements.
NEXT:
New Choice Principles >>
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