Page 456 - Biosystems Engineering

430 Cha pte r F i f tee n

Here, we present the results of experiments in which the storage
ability of apple cultivars is compared after hand thinning or chemical
thinning of fruitlets with NAA, CPPU, BA, and urea or with a mix-
ture of urea and NAA.
The experiments were carried as thinning was achieved with the
following preparations:

• Urea (in the form normally used as fertilizer), containing
45 percent a. i. (CH N O)
4 2
• α-Naphthylacetic acid (NAA), as the preparation Pomonit
R-10 containing 10 percent a. i. (potassium salt of NAA,
Organika, Poland)
• Mixture of potassium salt of NAA [(80 g /1 L) with urea
(30 g/1 L)] in a form of the preparation Pommit Ekstra 110 SL
(Varichem, Zabia Wola, Poland)
• Forchlorfenuron (CPPU) as the preparation Sitofex EC 1 percent
(AlzChem Trostberg Gmbh, CHEMIEPARK TROSTBERG,
Trostberg, Germany)
• Benzyladenine (BA) as the preparation Paturyl 100 SL con-
taining 10 percent a. i. (BA) (Reanal Finechemical Co., Buda-
pest, Hungary)

Experiment 1 was done with 9-year-old trees Gala cultivar grafted
onto M26 rootstock. Thinning was done with urea in the concentra-
tions from 0.75 percent up to 6 percent on two occasions: during petal
fall and just after flowering, or with the mixtures of urea (in concen-
trations of 0.45 percent to 1.5 percent) plus NAA (in concentrations
of 15 to 25 mg/L) just after flowering. Part of the trees was sprayed
with NAA alone in concentrations of 25 or 40 mg/L also just after
flowering. The other trees were sprayed with CPPU at 20 mg/L on
two occasions: just after flowering or 2 weeks later.
Experiment 2 was set up on 8-year-old apple trees of Lobo culti-
var grafted onto M26. For thinning, urea was used in concentrations
of 2 and 4 percent, respectively, during petal fall or just after flower-
ing. The mixtures of urea (0.45 and 1.5 percent) with NAA (15, 20, or
25 mg/L) were applied just after flowering but NAA alone (40 mg/L)
and CPPU at 2.5, 5, or 10 mg/L were used at the end of petal fall and
2 weeks after blooming.
Experiments 3 to 6 were done on the following trees, respectively:
12-year-old trees cultivar Gala/M26, 9-year-old trees cultivar Lobo/
M26, and 12-year-old trees cultivar Gloster/M26. The trees were
sprayed just after flowering with NAA at 25 to 40 mg/L or with BA at
50 to 100 mg/L when the fruitlets attained diameters of 10 to 12 mm.
In all experiments, unthinned and hand-thinned trees (just after
June drop, as is commonly done in commercial orchards) were the
controls. Results relating the influence of thinning on crop load and