Agriculture Reference
In-Depth Information
Fig. 10.9.
Relationship between the number of terminal shoots on 2-year-old
'Sensation' and 'Kent' trees and number of fruit retained. 'Sensation'
y
= 0.98
x
+
12.8,
r
2
= 0.86***, 'Kent'
y
= 0.18
x
+ 11.8,
r
2
= 0.31* (after Oosthuyse and Jacobs,
1995).
an application of 4 kg/tree in February-March provides 0.6 kg each of N
and K. A second application immediately after harvest of 6 kg/tree provides
0.9 kg each of N and K, for a total of 1.5 kg each of N and K for the year. N
and K at these levels are reported to enhance total yields, external colour and
sugar content, while N in excess of 1.8 kg can produce unfavourable ef ects
on external colour and fl esh fi rmness (Young and Koo, 1974). When leaf N
levels are greater than 1.5%, reduced fruit size is expected, with an increased
incidence of 'soft nose' and soft brown rot and an increase in the number of
days to ripen. Critical levels for various nutrients in mango leaves have been
developed (see Table 4.3).
Flowering synchronization and induction
Ethephon, an ethylene-releasing compound, increases fl owering and fruiting
in 'of ' years in biennial-bearing trees. In the past, to produce fl oral induction,
Philippine farmers used smudging by burning rice straw close to the trees, with
the smoke having a stimulating ef ect on mango fl owering. This was possibly
due to the ethylene gas in the smoke. In the last two decades more sophisticated
approaches have been developed and are being used commercially.
In the subtropics, fl owering depends on the cool winter temperatures (Fig.
10.4a) and fl owering is enhanced by water stress. In cool winters, the plants
will fl ower profusely (Fig. 10.8a). For young plants, this profuse fl owering
can limit plant growth and the ability to achieve the desired tree size, so the
