Agriculture Reference
In-Depth Information
Mineral nutrition
Introduction
Aspects of nutrient uptake by roots and of mineral nutrition in relation
to vegetative growth and fruiting have been discussed in earlier chapters.
Fruit mineral content in relation to storage and eating quality was con-
sidered in Chapter
and calcium uptake, transport and effects on cell
structure and metabolism were discussed in particular detail because of its
dominant role with respect to fruit firmness and the incidence of some pre-
and post-harvest physiological disorders. In the present chapter more gen-
eral aspects of the uptake, transport and redistribution of nutrients are dealt
with.
Nutrient requirements
A first approximation of the necessary supply of major elements for apple
and pear tree growth is obtained by measurement of the mineral con-
tent of well-grown and productive trees. Relevant figures from Washington
State, USA are given in Table
. These are for an old-style orchard at
maturity, with a similar cropping level but most probably more vegetative
dry matter than many modern orchards on dwarfing rootstocks. Most of
the nutrients removed from the soil and not returned to it are in the fruits
so the need to replace nutrients is largely a function of crop yield. Where
yields are much higher, e.g. in South Africa and, especially, New Zealand
the replacement needs will be much greater. Losses by leaching can be ap-
preciable under conditions of high rainfall or irrigation on appropriate soil
types. Haynes and Goh (
.
%
of the amount of nitrogen supplied in the irrigation water or as fertilizer
in New Zealand, and exceeded irrigation and fertilizer inputs of Ca and
Mg. The amount of N lost by drainage depends on irrigation level and the
) estimated that leaching losses were about
