Symptoms of Copper deficiency may not be as easy to identify as those for the other essential elements. Copper does not move in the plant so deficiencies appear first in younger growth.
Chlorosis or yellowing develops, starting on the leaf edges. The leaf tip wither and droop and turn from yellow to grey and die on grain crops. The leaves curl and twist and fail to unroll. 'Die back' occurs in tree crops.
Functions in plant:
Necessary in chlorophyll formation; is involved in photosynthesis and in seed formation. Is a part of certain essential enzymes. Acts as a catalyst in certain carbohydrate and protein building reactions.
Mobility in plant: Relatively immobile.
Influence of soil pH: Copper availability goes down as the pH goes up from 5.0-8.0. Low copper is also prevalent in high organic, very acid soils (peats and mucks).
Factors affecting level: pH, organic matter, soils with low organic matter with low pH's (below 4.7) will precipitate copper.
Level in soil: Available copper may be 1-200 kg per hectare.
Adequate level in plant: Soybeans 10 ppm. Cotton 11 ppm. Grape 5-50 ppm. Lemon 20-200 ppm.
Plough down heavy amounts (25-100 kg per ha) of copper sulphate. Or apply 0.25-1.0 kg per hectare in fertilizer. Or foliar spray with chelated copper product.
Small grains (cotton and soybeans are moderate).
Plants vary widely in their response to Cu. The stage of growth exhibiting the greatest need for copper is in the early stages- before flowering. Copper can be toxic at quite low levels, probably by depressing iron uptake.