Agriculture Reference
In-Depth Information
modern greenhouse it was found that the increase of dry matter production in the
semi-closed greenhouse was mainly explained by a higher CO
2
concentration when
compared to an open greenhouse. Similarly, Dannehl et al. (
2012
) showed that a
combined application of a high pressure fog system and CO
2
enrichment in a semi-
closed greenhouse were adequate to accelerate plant growth, increase the dry matter
in leaves, and promote the formation of fruit set per truss, as well as increase in the
maximum total yield by 20 % as well as fruit size. On the other hand, the occurrence
of blossom-end rot in tomato fruit was reduced when compared to those grown
under conventional climate conditions. Qian et al. (
2012
) concluded that the photo-
synthetic acclimation to elevated CO
2
concentrations depended on the source-sink
balance and a continuously high CO
2
concentration in a semi-closed greenhouse
does not cause feedback inhibition in high producing crops, because these plants
have sufficient sinks (fruits) to utilize extra assimilates.
Water Supply, Irrigation Management and Systems
and their Effect on Plant Growth and Development
General
Water is one of the most important factors influencing plant growth, productivity,
and quality and is the main component of plant cells and total fresh biomass content
of plants. Typical greenhouse grown vegetables such as tomatoes, cucumbers, pep-
pers, and lettuces may contain 90-96 % or even more water. For protected crops,
irrigation and its management have a special importance since natural precipitation
is excluded and if soilless culture systems (SCSs) are used, often the groundwater
sources are unavailable. Moreover, greenhouse plants are not exposed to drastic
changes of environmental conditions. For example, Huang and Snapp (
2004
) re-
ported a very consistent association between the incidence of shoulder check or rus-
seting of tomatoes grown in the open and precipitation events followed by periods
of hot, dry weather during rapid fruit expansion. In addition resultant fruit quality
was higher and the incidence of defects lower in fruit produced under plastic rain
covers than in open field-grown tomatoes.
Water supply is significantly higher in protected cultivation than in the open
field, mainly due to the intensity and quantity of year-round biomass production.
High temperatures, which can be reached in greenhouses during summer, may also
increase water demand. On the other hand, the requirements on water quality are
considerably higher. Generally, the majority of protected crops is warm-season spe-
cies that are sensitive to low temperatures. Therefore water temperature must be as
close as possible to the plant root temperature. Increased salinity in the irrigation
water is more likely to have a more negative impact than in the open field, over all
in a closed loop-system.
