Agriculture Reference
In-Depth Information
oped. These growing methods include systems without a solid medium, as well as
aggregate systems, in which inorganic or organic substrates are used (Gruda
2009
).
The distinction between soilless culture and other systems is sometimes blurred.
For instance, the growth and maintenance of indoor ornamental pot plants or the
outdoor production of hardy nursery plants in containers is considered soilless cul-
ture. On the other hand, the supply of nutrient solution to plant roots has become a
custom cultural practice for soil-grown greenhouse crops as well, similar to using
drip irrigation in outdoor horticulture.
Soilless cultural systems (SCS) offer significant advantages in comparison to
direct cultivation in soil. These include cultivation of protected crops independent
from soil characteristics. Therefore they exhibit a great degree of flexibility, even in
areas with poor or adverse growing conditions, such as poor soil structure or high
soil salinity. The main reason for using soilless culture however is the reduction of
soil-borne pathogens and the control over water and nutrient supplies. The majority
of nutrients used in such systems is soluble or in liquid form applied in a nutrient so-
lution. In soilless culture either a liquid or aggregate medium is used. Such produc-
tion systems and mainly the liquid method are called hydroponic systems as well,
whereas periodically spraying plants with a nutrient solution is called aeroponic.
The main characteristic of SCS is the restricted volume of a rooting medium in
comparison to soil-grown crops. The common issue in this system is the precise
amount and ratio of the desiderated nutrients. In case of liquid systems and the
use of inorganic substrates no interference of organic matter or cation exchange
capacity (CEC) in the soil is observed. There has been an improved product quality
however through more precise dosage of water and nutrients within closed systems
(Gruda
2009
). In Europe, Canada, and in the large horticultural industry complexes
in the U.S., 95 % of greenhouse tomatoes are produced in SCSs (Peet and Welles
2005
). Despite the considerable advantages of commercial soilless culture, there are
still some disadvantages, such as higher costs that are normally required for their
initial installation and increased technical skills that are needed to cope with its
installation and management (Savvas et al.
2013
).
Savvas et al. (
2013
) classified soilless culture and growing media systems into
water/hydroponic culture and/or deep water culture, float hydroponics, nutrient
film technique (NFT), deep flow technique, aeroponics, and substrate/aggregate
culture. Gruda et al. (
2013
) differentiated between inorganic and organic grow-
ing media, where inorganic growing media included rockwool (the most used
substrate in soilless culture), perlite, tuff, volcanic porous rock, expanded clay
granules, vermiculite, zeolite as well as some other synthetic materials, sand and
gravel. Organic growing media included peat, composts, bark, coir, and wood
fibers as well as other wood residuals. In addition, several peat substitute/alter-
native growing media have been introduced worldwide, due to an increased en-
vironmental awareness of consumers, the constant dismantling of ecologically
important peat bog areas and pervasive waste problems. Recently, biochar, a form
of charcoal which is manufactured from organic matter by heating in an anoxic
situation (pyrolysis), has been used in agriculture and introduced in horticulture
as a growing medium as well (Gruda
2012
; Gruda et al.
2013
). Each substrate
