Agriculture Reference
In-Depth Information
(or in a so called one-crop-per-year). However, in areas with hot summers, usually a
two-crops-per-year production strategy is applied. In some regions, a single-cluster
strategy or five-crops-per-year is used as well (Logendra et al.
2001
).
The prevalent system practiced on greenhouse cucumbers is V-training or the
umbrella system which involves removal of all emerging flowers and laterals up
to the 8-9th node (approx. lowest 60 cm of the main stem). Thereafter, just one
fruit per lateral is allowed for the next 60 cm of the main stem. One fruit and one
lateral are allowed to grow from each leaf axis on the rest of the main stem. After
the main stem reaches the wire, the growing point is pinched out allowing an extra
2 or 3 leaves above the wire. Afterwards, the two strongest laterals from the top of
the plant are allowed to grow over the wire and then to hang down. The next steps
differ depending on plant variations described by Papadopoulos (
1994
). In addition,
the author recommends the control of fruit numbers due to selective fruit thinning,
in order to avoid plant exhaustion and to improve fruit quality.
Similarly, pepper plants can be trellised to the Dutch “V” (a two-stem pruned)
system or to the “Spanish” (non-pruned plants) system. Jovicich et al. (
2004
) com-
pared the “V” with the “Spanish” trellis system and found no differences in total
marketable fruit yield. Labor requirements for the Spanish system were reduced
however by at least 75 % compared with the “V” trellis system.
Pruning
Pruning is a (manual) operation used to support training, with the aim of improv-
ing light relationships, equilibrating plant growth and development, providing
for a better control of diseases with consequences in minimizing yield losses,
and improving product quality. Pruning helps to facilitate cultural operations in
the greenhouse. Both vegetative (e.g. 'leaves' by tomato and cucumber, 'new
side shoots' by tomato and pepper, 'shoot apices' by tomato and cucumber) and
generative organs (e.g. 'flower removal' by roses, and 'fruit thinning' by toma-
toes) are pruned.
Navarrete and Jeannequin (
2000
) investigated the frequency of lateral shoot
pruning in greenhouse tomato crops, and found that the de-shooting frequency
affected both vegetative growth and yield and pruning time. When de-shooting
was performed every 21 days, the stem diameter and the number of fruits per m
2
was also reduced, leading to a significantly lower yield in comparison with a 7
day deshooting cycle. Moreover, the tomato harvest was delayed, presumably
due to dry matter partitioning and better light interception due to the pruning
process.
Plants, such as roses, possess high plasticity, rapid and dynamical acclimation
in response to changes in incident sunlight established by pruning (Calatayud et al.
2007
). Similarly, roses showed a higher maximum efficiency of photosystem II
(PSII) in dark-adapted leaves, a higher actual quantum yield and a higher propor-
tion of open PSII reaction centers when pruned. They also showed lower non-pho-
