Trace elements in the soil - Soil Essentials: Managing Your Farm's Primary Asset - page 46

What do they cost?
Bagged phosphatic fertiliser with trace elements adds about 10% to 20% to the
cost of the plain fertiliser, depending on the trace element required. Horticultural
mixes may not cost much more than the standard fertiliser.
Foliar fertilisers are expensive per litre, but less is needed because the plant can
rapidly absorb nearly all that is applied, so the effective cost per gram of trace
element per hectare is less. Note, however, that in hot weather they can cause leaf
scorch if applied during the heat of the day. If trace elements are lacking in the soil,
it is good business sense to apply them, because a relatively small outlay can often
give spectacular returns (Figure 15).

OPTIMUM

Deficient Level Toxic Level

Unit of trace elements
RATE DETERMINED FROM SOIL TESTS

Figure 15 Effect of trace element availability on yields. ( Soil Sense C-08)