Thesis (DScAgric)--University of Stellenbosch, 1958. / OBJECTIVE.
High economic production has ever been the aim and aspiration
of the agriculturist and no less that of the fruit farmer. In
striving towards this aim the latter has for a long time been at
a disadvantage with regard to control of his nutritional programme.
Even on naturally fertile soil, the question continually arises as
to what the correct fertilizer treatment should be to maintain high
productivity and how such a decision can be arrived at. A satisfactory
answer to these questions could have been obtained from
fertilizer trials if it was not such a difficult matter, in view
of the extensive and long-term nature of such trials with fruit
trees, to establish a sufficient number for each fruit species on
different soil types and under different climatic conditions.
Efforts to find a new approach to the problem have turned
attention to the plant itself and its chemical make-up as affording
the best index of its nutritional requirements. Intensive work in
this direction has resulted in the evolution of a new tool in
agriculture, the technique of diagnostic leaf analysis or 1Toliar
diagnosis" as originally proposed by Lagatu and Maume in France
and Thomas in u.s.A. A review of the literature is presented
indicating the prodigous amount of research which has been applied
to studies of the relationship between plant response and nutrient
supply in terms of plant composition. Agriculturists have been
quick to recognize the potentialities of leaf analysis as a practical
guide in nutritional problems and advisory services based
on foliar analysis have already been established for certain crops
overseas.
The experimental basis for formulating such a scheme for
deciduous fruit in the Western Cape Province is provided by the
factual evidence presented in this thesis.THE TECHNIQUE.
The technique of diagnostic leaf analysis comprises sampling
of leaves, preparation of sample for analysis and the analysis
itself followed by interpretation of the analytical results by
comparison with previously determined nutritional standards.
Numerous factors were found to influence the final composition
of the leaf sample as determined by analysis, such that strict
adherence to a standardized procedure through all phases of
sampling and preparation of leaf samples for analysis is required
to eliminate or reduce errors likely to cause misleading interpretations.
Experimental data are presented suggesting how the
leaf sample should be selected on a tree and how it should be
handled, cleaned, dried, ground and stored to reduce sampling and
other errors.
The final procedure as adopted eliminates most of the potential
sources of experimental error but two unavoidable sources of
e~ror remain to be accounted for, that due to tree variation and
seasonal effect. The variation in leaf composition from tree to
tree was found to be very considerable, so that aampling from a
large enough group of trees (6 to 10) to reduce the error involved
is essential in order to obtain leaf data which correctly reflects
the nutrient status of the portion of the orchard concerned.
Secondly, on the grounds of marked consistency found in different
fruit species as to seasonal and year to year variation in mineral
nutrient concentration, correction factors have been formulated
and are suggested as a means of overcoming these sources of error. THEORETICAL BASIS.
A diagnosis of the nutrient status in terms of the analytical
results as finally determined is obtained by comparison of the data
with previously established leaf composition standards of reference
and by correct interpretation of the deviations from these standards. The theoretical basis for setting up these index values is
discussed. The criterion used is based on the concept of Optimum
Values which aaequately integrates the known relationships between
plant response and nutrient supply in terms of internal nutrient
concentration. A modification of this concept is proposed to the
effect that for maximum growth and yield there exists an optimum
range of nutrient concentrations with upper and lower limits for
each of the functional elements, and that within this range the
interrelationship between the individual nutrient elements is also
optimal.
Since no local fertilize~ trials with deciduous fruit trees
are available and only one for grapes, data from highly productive
plants in commercial orchards and vineyards were used to determine
the upper and lower limits of the "optimum range", on the following
premise. If leaf analysis data are available from a sufficient
number of high performance orchards in different localities representing
a wide range of nutrient supply and environment, the
highest and lowest values obtained may be considered to represent
a close approximation of the limits of the range required for
optimum performance. It is contended that index values obtained
in this way must be of practical value in assessing the nutrient
status of fruit trees. It is further postulated that the lower
limits for the micro-nutrients and even for magnesium may be
justifiably adjusted according to the concentration levels associated
with symptom expression.
INDEX VALUES.
The necessary data for determining standards of leaf composition
were obtained from leaf analysis surveys of orchards and
vineyards and from a grape fertilizer experiment in the Western
Cape Province. Visual symptoms of prevailing nutritional disorders
are described (supplemented by photographic illustrations)
and their relation to leaf composition indicated. Tentative index values have been determined on the basis indicated for each
fruit species, apple, pear, peach, apricot, plum, prune and grapes.
These nutritional levels comprise upper and lower limits for the
nutrients N, P, K, Ca, Mg 1 Mn 1 Fe and Cu, as well as the upper
limits for B and Na.
DIAGNOSTIC INTERPRETATIONS.
Assessment of the nutrient status in terms of these index
values suggests that many orchards and vineyards in the Western
Cape Province, particularly prune, apricot and grapes, are suffering
from malnutrition in some form and are likely to show a marked
response to nutritional treatment as suggested by foliar diagnosis.
The use of diagnostic leaf analysis constitutes an important
advance in dealing with orohard problems in that an immediate
decision is possible regarding nutrient status and related aspects
such as selection of suitable sites for fertilizer trials and
adjustment of the fertilizer programme. / AFRIKAANSE OPSOMMING: geen opsomming
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/49547 |
| Date | 12 1900 |
| Creators | Beyers, Ewald |
| Contributors | De V. Malherbe, I., Stellenbosch University. Faculty of AgriSciences. Dept. of Horticulture. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 259 p. : ill. |
| Rights | Stellenbosch University |
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