Geoscience Reference
In-Depth Information
have been declining - from 57.7 to 36.4 kg/ha between 1979 and 1982 at Hurley in
Berkshire - and are likely to be reduced still further to overcome the undesirable ef-
fects of suphur dioxide on the environment. In the last few years, sulphur deficiency
has been found in grass for silage in Wales and south west England, and one case was
reported in barley in Wales during 1988. We may, therefore, have to supplement the
supply in the future.
T
ABLE 9
Minor nutrients needed by crop plants (from Davies, Eagle & Finney, 1982).
Deficiency situ-
ations
Element
Crops
Soil types
Conditions
cereals
poratoes
sugar-beet
sandy soils
lime-rich peats
Manganese
excess lime
sugar-beet
pears
Iron
chalk
excess lime
acid conditions
high organic mat-
ter
excess lime
light peats
heathland sands
humus-rich chalk
Copper
cereals
brasicas
beet, swede
excess lime
drought
Boron
sandy soils
Molybdenum cauliflower
rare in Britain
acid conditions
not a problem in Bri-
tain
Zinc
excess lime
Sodium, the cation of common salt, is only needed in large amounts by crops of
maritime origin such as mangolds, spinach and sugar-beet. Calcium is important for
keeping the soil 'sweet', i.e. in preventing soil acidity. Its use goes back to Roman
times but it is rarely in short supply as a nutrient. Most farm land in Great Britain still
supplies the 5-25 kg/ha of magnesium required by crops, though deficiencies are in-
creasingly common on lighter soils.
