Our assessmentof thetraditionallateleafanalyses inJuly/Augustfollowsthewell-known
international standards (Table 5).

EARLY FRUIT ANALYSIS
An additional method to target the nutrient supply, especially so as to improve internal fruit quality,
is early fruit analysis.We have been using it since 1986 for a bitter pit prediction program. Also in
this case we rely on anetwork of orchards withdifferentvarieties. For 12 years we have been
taking fruit samples for analyses at the beginning of July, when the fruitlets have reached an average
weight of 70 g. The calcium and potassium levels in the fruit supply useful information about the
danger of bitter pit and other physiological diseases in the fall.

If the potassium/calcium ratio in the fruit projected forward to the fall remains under 30, there is no
danger to the internal quality of the fruits. In thiscase we advise proceeding with the usual measures.
As soon as the index rises above 30-35, we issue a warning. In the summer of 1998 the situation
was extremely critical with a K/Ca ratio of 37. We never had reached such a dangerous value since
the introduction of this method. In this situation the Advisory Service recommended a series of
measures against bitter pit.

Measures recommended in case of an increased risk of bitter pit are:
•increased number of calcium applications
•summer pruning
•reduced irrigation
•ground cover under the trees

Before the 1998 harvest we noticed fruits with bitter pit symptoms on susceptible varieties like
Jonagold or Braeburn and on trees bearing light crops. During storage, bitter pit damage increased
further and reached an average of 8-10%. On Golden Delicious and Braeburn we recorded peaks
of30%. The bitter pit prediction model proved effective. However, if the conditionsare veryfavorable
for bitter pit incidence, even intensive calcium sprays can only reduce the damage, but they can
work no miracles.

NITROGEN
Nitrogen affects all the important stages in the life and production cycle: e.g., shoot growth, yields
and fruit quality. Therefore the handling of nitrogen fertilizers (rates, time,type of fertilizer) is a
very delicate matter which requires a lot of experience, know-how and observation. The correct
determination of the nitrogen requirements is rendered more complicated by some factors which
are difficult to assess such as the amount of nitrogen leaching and the mineralization rate.

Under our soil and weather conditions the level of available nitrogen, N mineralized (N-min), is
likely to be low in spring. Along with the soil temperature the N-min content rises, peaks in June/
July and remains very high until October. It is not until the soil cools down in the fall that the N-
min values drop (Figure 4).

The nitrogen need of the trees shows a different curve. It reaches its peak in the spring (bloom until
end of first stage of shoot growth) and flattens in the course of the summer until fall.

What can we do in practice in order to counterbalance these contrary developments in the soil and
the trees?
1.In order to restock the nitrogen reserves after harvest, urea 30-40 kg/ha (26.7-35.7 lbs/acre)
is sprayed. This is doneespeciallyin orchards with aheavy cropanda slightnitrogen
deficiency.
2.If required, nitrogen is applied in pre-bloom.
3.If the nitrogen uptake is disturbed by low soil temperatures below 5ºC (41ºF) and frost, we
recommend supportive urea sprays 5-7 kg/ha (4.3-6 lbs/acre) in the spring around bloom.
4.In the summer and before harvest the nitrogen and potassium supply frequently exceeds the
requirements (due to the mineralization and breakdown of the grassmulch).If this becomes
a problem (too vigorous growth,too large fruits, physiological disorders in the fruits) two
measures are advisable:1) a reduction of irrigation (by up to 50% of the evapotranspiration)
and 2) a ground cover in the tree row.

In spite of all the information we possesson the nitrogen balance in fruit tree growing, the orchardists
are still confronted with the basic question: How much available nitrogen is contained in the soil
and how much should they apply in spring? Some years ago we introduced a valuable method, the
N-min-analysis, which helps us answer these questions.

For the N-min-analysis we use a chilled soil sample to determine the available nitrogen (NO+
3
NH ) in a 0-40 cm (0-16 inches) deep soil layer. The best time to do this is 2-3 weeks before

4bloom, prior to fertilization. Based on the N-min values we have worked out a nitrogen
application program which has proven successful (Table 6).

This method allows a precise adjustment of N input at a critical time, that is, in spring before
bloom. This analysis costs the orchardist only US$12.50.Lately we have also applied a colorimetrical
field method, using the sticks (nitrate test) of the Merck Company. This seems to be an interesting
and fast method.

From the data on the N losses through the crop, the N-balance in the orchard soils, the trials and the
N-min examinations we can deduce that in a normal bearing orchard the trees require 30-50 kg/ha
N (26.7-44.6 lbs/acre) every year before bloom. Sandy soils which are low in humus require more
nitrogen (up to 80-100 kg/ha) (71.4-89 lbs/acre).

Very fertile soils with a deep subsoil frequently do not need an additional nitrogen application.

POTASSIUM
The key element potassium regulates water absorption, internal and external fruit quality, especially
fruitsize, tasteand flavorand finallytheincidenceofphysiologicaldisorders.Theuptakeof
potassium by the plant has a peculiarity which must be kept in mind when fertilizing.

The potassium level in the soil and, still more, the humidity of the soil influence the K-uptake very
strongly. This renders correct potassium management in the orchard more difficult since numerous
and well-distributed rainfalls in spring and summer may result in an undesirably high potassium
uptake.

Potassium diffuses easily into the leaf and fruit tissue and excessive supply leads to leaf spots and
leaf drop on Golden Delicious and Gala as well as to physiological disorders like bitter pit, internal
breakdown and storage problems. Therefore we advise using potassium fertilizers with caution.

If the potassium level in the soil is within the optimum range, only the losses through the crop
should be compensated, that is, 60-100 kg/ha K O (53-89 lbs/acre). For light crops the lower rate is
2advisable, for heavy crops the higher one. After the increased potassium uptake in the last years we
now recommend splitting the potassium input. Before bloom only half the annual amount should
be applied. If fruit set proves to be good or very good, the remainder should be applied.

CALCIUM
The key element calcium is decisive for the internal stability and health of the fruit. We know that
in the South Tyrol the calcium level in the soil does not play a very important part. This element
spreads very unevenly within the plant. The shoots and leaveshave a high sink potential for calcium
and easily absorb thecalciumcontained in the sap. Thefruits absorb calcium,especially in the
early stages, as long as they themselves assimilate. Later they absorb very little calcium.

We recommend calcium applications to the soil at regular intervals, in order to
•keep the pH value within the desired slightly acid range (pH 6-7)
•compensate the losses through leaching
•maintain the healthy soil texture, especially the stability of the crumbs and the soil aeration

With pH values ranging from pH 5.5-6.5 and a low calcium level we recommend an application of
approximately 1,000-1,500 kg/ha (0.4-0.6 MT/acre) calcium carbonate, if necessary also dolomite,
every two years.

MAGNESIUM, MANGANESE, BORON
Magnesium and manganese are the key elements for good leaf quality. Under our conditions even
a slight deficit can result in poor leaf development in spring, leaves turn pale green while the veins
remain dark green, leaf drop and thus a reduced photosynthesis.

An adequate magnesium concentration in the soil seems to be important. Therefore, even if the soil
analysis indicates an optimum supply, we recommend an annual application of 20-30 kg/ha MgO
(17.8-26.7 lbs/acre). Difficult soil conditions (cold soil, waterlogging, unfavorable pH) can reduce
the magnesium and manganese uptake. In such cases we recommend foliar sprays with these two
elements.

Ourlightly textured sandy soilsare often low in boron and thereforeit isthe most critical trace
element in our fertilization programs.Boron is important to ensure
•adequate growth of the pollen tube which is crucial for a good pollination
•sufficient shoot growth
•suitable calcium deposit in the fruits
•smooth skin of the fruits

It is our primary aim in mineral nutrition to keep the tree healthy and to promote the nutrient uptake
through the roots.