Production Practices and Quality Assessment of Food Crops. Vol. 1

70 M. Génard and F. Lescourret
5.2.4. Technical operations
SIMTECK includes four technical operations: planting scheme and choice of pollenisers,
winter pruning, fruit thinning, and irrigation. The block design comprises
the choice of cultivars, male-to-female arrangement and planting ratio, and distances
between rows and between plants within a row. Winter pruning consists in selecting
the number of replacement canes to be left on the vine, and the number of buds
to be left on the cane. Thinning takes place at the flower bud stage. The current
practice consists in, first, eliminating the aberrant shaped (flat and fan shaped) flower
buds. If the remaining flower load is judged too important, lateral flowers, which
are always small and have little commercial value (Antognozzi et al., 1991), can
be removed till a satisfying flower load is reached. Another technical choice
addressed for example by Lahav et al. (1989) concerns the time of thinning, which
can take place at the flower bud stage, or just after fruit set when the visual control
is easier. Various irrigation tactics can be tested, for example supplying a fixed
amount of water and triggering irrigation when the accumulated plant water demand
just exceeds a given threshold; or supplying at a fixed frequency an amount of water
corresponding to the plant water demand accumulated since the last irrigation.
5.2.5. Effect of technical operations according to SIMTECK
The plot simulated comprised six rows and 36 plants per row on a regular scheme
with planting distances equal to 6 m between rows and to 4 m within the row
(Figure 10). Males of the Tomuri cultivar were found at every third position in every
third row, yielding a planting ratio of 1:8.
5.2.5.1. Planting options, pruning, thinning and irrigation
Simulated planting schemes included that of the reference plot and a quincunx
scheme with identical male to female planting ratio (Figure 10). Fruit size distribution
according to the different planting schemes was similar (Figure 11a).
Accordingly, yields were close to each other (17.2 vs. 16.8 tonnes/ha). Different
planting spacings (5 or 7 m planting distance between rows) resulted in contrasted
fruit size distribution (Figure 11b) and yields (24.4 for the shorter vs. 13.1 tonnes/ha
for the larger distance).
According to the simulations, Tomuri plants seemed to be less efficient than Matua
plants, because of fertility differences, as shown by fruit size distribution (Figure
11c) and resulting yields (17.2 vs. 19.5 tonnes/ha). The more severe the pruning,
the lower the number of fruit per vine. Due to the limiting effect of vine crop load
on fruit growth, fruit size distribution was right-shifted in the case of severe pruning
(Figure 11d), but the difference was slight and the corresponding yield was
dramatically lower owing to the small number of fruits (11.5 vs. 25.2 tonnes/ha in
the case of light pruning). Thinning simulations were performed at bud stage either
with the aberrant shaped flowers removed, or the aberrant shaped and the whole
set of lateral flowers. The number of fruits per vine was slightly lower when the
lateral flowers had been removed (Figure 11e). In this case, fruit size was slightly
favoured, due to the fact that vine load had decreased, but also that fruits with