Agriculture Reference
In-Depth Information
Estimated annual utilization (kg ha
−
) of major nutrients by a mature apple
orchard (cv. 'Delicious') with yields of
Table
.
tha
−
.
NP
K a
g
Removed in fruit including seeds
.
.
.
.
.
In framework of trees including roots
.
.
.
..
Total (A)
=
Net uptake
. .
. .
.
Leaf-fall
.
.
.
. .
Dropping blossoms and fruitlets
including thinning of fruits
.
.
.
.
.
Prunings
.
.
.
.
.
=
Total (B)
Return to soil
.
.
.
.
.
Total (A
+
B)
=
Gross uptake
.
.
.
.
.
From Greenham (
), summarized from Batjer
et al.
(
). Reproduced with
permission.
presence or absence of grass on the orchard floor (Stevenson and Neilsen,
).
The net uptake of K is almost twice that of N and many times as high as that
of P and Mg. A remarkably similar balance of uptake is shown by Japanese
pear (
Pyrus serotina
Rehder). Buwalda and Meekings (
) found the nutrient
content of deciduous parts (fruits and leaves) to be equivalent to
kg N,
kg Mg per hectare, and considered that these figures
would be exceeded in commercial orchards which have
kg P,
kg K and
% higher yields
than the experimental one. These figures for nutrient removal are very much
lower than those, for example, of cereals and vegetable crops. Greenham (
-
)
quotes N, P and K removal, in kg ha
−
,of
,
and
for wheat and
,
for carrots, respectively.
The annual requirement for fertilizer application depends on total require-
ments and on the natural supply from the soil, both of which are variables.
Estimation of the balance of these is made almost impossible by the com-
plexity of the factors involved (Klein and Weinbaum,
and
). Soil analysis
pre-planting and at regular intervals is very important in order to identify
potential needs and problems but changes in soil nutrients do not, in gen-
eral, provide a guide for fertilizer practice. This is especially so because of
the difficulty in determining the effective tree rooting zones, the importance
of carry-over of nutrient reserves in the tree from one year to the next and
the importance of the supply of nutrients to specific organs rather than gross
uptake. Leaf and fruit nutrient concentrations have, however, been found to
reflect nutrient status and requirements. Desirable levels established empiri-
cally are summarized in Table
.
. These figures are based on much original
