Agriculture Reference
In-Depth Information
soil reservoir as the growing season progresses. Regulated deficit irrigation is a re-
gime which purposely stresses the trees or vines at specific growth stages which are
known to be least sensitive to water deficits outside these periods the trees are given
full deficit replacement irrigation. Partial root drying is where there is alternate wet-
ting and drying of either side of the crop row (Davies et al.
2000
,
2005
; Kang and
Zhang
2004
; Bravado 2005).
The efficacy of water saving irrigation systems as compared with overhead sprin-
kler methods has been demonstrated for example by Bowen et al. (
2012
). They in-
vestigated the effects of converting from overhead sprinkler to drip irrigation on the
growth, leaf gas exchange, and fruit production of Merlot grapevines. The frequency
of irrigation was 50 % higher using drip compared with sprinkler systems but 64 %
less water was applied. Water-use efficiency as measured by transpiration was great-
er under drip than sprinkler irrigation and input water use efficiency averaged 2.5
times higher under drip irrigation over the 4 years. A further advantage of low level
or below ground drip systems is that they can be used for the application of fertilis-
ers. This reduces the quantities of fertiliser especially nitrogen that are required while
increasing the efficiency of its use by plant roots (Granados et al.
2013
; Ashraf et
al.
2012
). Further efficiencies in crop production may be gained by combining drip
and low level irrigation with the application of mulches. This combination enhanced
the growth, irrigation water use efficiency (IWUE), fruit yield, and quality of straw-
berry plants (Kumar and Dey
2012
). In general these techniques have been most
successfully applied so far with deciduous and evergreen fruit trees, vines and some
soft fruit. Experiments with field vegetables and particularly potato crops have been
less successful. Probably this reflects the shallow root systems and higher sensitivity
to drought stress in these crops. Potato tuber yields and quality were substantially
reduced by water deficits even when these were applied only briefly (Lynch et al.
1995
; Shock and Feibert
2002
; Liu et al.
2006
). By contrast the application of water
restriction husbandry in ornamentals could provide benefits. This has the potential
for reducing excessive growth in woody plants such as
Cornus
and
Forsythia
spp
(Cameron et al.
2004
,
2006
). In this research water consumption was halved. Further
financial benefits accrued from more compact growth and less need for pruning.
Horticulture is responding to reductions in the availability of water which is a
key resource by the innovative application of basic science. Understandings of the
physiological mechanisms which govern water flow from the soil into roots, through
the stem tissues into leaves and out via stomata in the evapotranspiration stream
provide a sound scientific platform from which new and imaginative husbandries
can arise. These are turned into practical realities by engineering new equipment.
The Value of Horticultural Science
Over the past 25 years horticulture has demonstrated amazing robustness and capac-
ities for trading in a global market with the very minimum of government support or
even interest. Comprehensive evaluations of the value of horticultural research are
