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The study compares the effects of: timer ('Timer') and soil moisture sensor-controlled irrigation on soilless lettuce; two volumetric water content (Θ) thresholds for irrigation (0.30 ('Θ = 0.3') and 0.40 m3/m3 ('Θ = 0.4')). The most nutrient solution (NS) was applied in 'Timer' where the lowest water use efficiency was observed, with 17 and 42% less NS used in 'Θ = 0.4' and 'Θ = 0.3', respectively. Irrigation volumes followed the plant water needs in the sensor-controlled treatments, with little or no leaching, while 18% of leaching was recorded in 'Timer'. Plants in 'Timer' and 'Θ = 0.4' had higher fresh weights (24%) and leaf area (13%) than plants in 'Θ = 0.3'. Similar dry weight was observed among treatments but percentage of dry matter was 20% higher in 'Θ = 0.3'. Gas exchanges and leaf tissues chemical composition were similar in all treatments, but nitrate concentration was lower in the 'Θ = 0.3' plants. Precision sensor-controlled irrigation based on Θ measurements is an effective tool to increase the overall water use efficiency and to improve the quality of soilless-grown lettuce by acting on the substrate moisture level. © 2016, Czech Academy of Agricultural Sciences. All rights reserved.
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Timer versus moisture sensor-based irrigation control
of soilless lettuce: Effects on yield, quality and water
use efficiency
F.F. M1, M.W.  I2, A. P1
1Institute of Sciences of Food Production, National Research Council, Bari, Italy
2Department of Horticulture, University of Georgia, Athens (GA), USA
M F.F.,  I M.W., P A. (2016): Timer versus moisture sensor-based irrigation control
of soilless lettuce: Effects on yield, quality and water use efficiency. Hort. Sci. (Prague), 43: 67–75.
e study compares the effects of: timer (‘Timer’) and soil moisture sensor-controlled irrigation on soilless lettuce;
two volumetric water content (Θ) thresholds for irrigation (0.30 (‘Θ = 0.3’) and 0.40 m3/m3 (‘Θ = 0.4’)). e most nutri-
ent solution (NS) was applied in ‘Timer’ where the lowest water use efficiency was observed, with 17 and 42% less NS
used in ‘Θ = 0.4’ and ‘Θ = 0.3’, respectively. Irrigation volumes followed the plant water needs in the sensor-controlled
treatments, with little or no leaching, while 18% of leaching was recorded in ‘Timer’. Plants in ‘Timer’ and ‘Θ = 0.4’ had
higher fresh weights (24%) and leaf area (13%) than plants in ‘Θ = 0.3’. Similar dry weight was observed among treat-
ments but percentage of dry matter was 20% higher in ‘Θ = 0.3’. Gas exchanges and leaf tissues chemical composition
were similar in all treatments, but nitrate concentration was lower in the ‘Θ = 0.3’ plants. Precision sensor-controlled
irrigation based on Θ measurements is an effective tool to increase the overall water use efficiency and to improve the
quality of soilless-grown lettuce by acting on the substrate moisture level.
Keywords: Lactuca sativa L. var. capitata; greenhouse; volumetric water content; leaching; easily available water
Minimally processed or fresh-cut leaf y vegetables,
such as lettuce (Lactuca sativa L.), have been gain-
ing importance in the worldwide vegetable market.
Leafy lettuce was traditionally cultivated in soil, but
recently soilless cultivation techniques have been
considered. ere can be large differences between
soil and soilless systems in terms of inputs, size, lo-
cation, environmental conditions and productivity
(S et al. 2012). Although greenhouse soilless
cultivation could be impaired in some regions of
the world by the generally high capital investments
and energy requirements, greenhouse production
of leafy vegetables using soilless culture permits
precise control of plant nutrition, and allows for
more efficient water and nutrient use and higher
sanitary quality than conventional, soil-based cul-
ture. Soilless culture can also simplify post-harvest
handling and waste-water treatment (V
et al. 2008; F at al. 2009; M et al.
2011). Several recent studies focused on the effects
of nutrient solution (NS) mineral composition on
lettuce yield and quality in soilless cultivation sys-
tems (F et al. 2009; S et al. 2011).
However, there is a general lack of information on
Supported by project “Efficient Irrigation Management Tools for Agricultural Cultivations and Urban Landscapes” (IRMA) –
European Territorial Cooperation Programmes (ETCP), Greece-Italy 2007–2013.
Hort. Sci. (Prague) Vol. 43, 2016 (2): 67–75
doi: 10.17221/312/2014-HORTSCI
the influence of irrigation management on soilless
lettuce yield and quality.
Irrigation management directly affects crop per-
formance, and efficient irrigation practices can lead
to qualitative and quantitative improvements in veg-
etable production (D et al. 2010). Efficient irri-
gation management also contributes to the sustain-
able use of water. Increasing competition for water
resources (J, V   2005) has raised consumer
and government interest in the environmental im-
pact of food production. As a result of the increasing
pressure on limited water resources, member states
of the European Union implemented the Water
Framework Directive, which aims to assure the good
ecological status of all water bodies (A
2000). Since agriculture is an important source of
nonpoint source water pollution, it may be neces-
sary to adopt agricultural practices which minimize
the release of pollutants to meet societal goals and
satisfy government regulations (B et al.
2010). For the greenhouse industry, this means that
irrigation management will become increasingly
important, since excessive irrigation results in low
water use efficiency, leaching, and runoff of water,
fertilizer, and other agrochemicals.
Irrigation management using timers or the visual
assessment of plants and substrate is generally in-
efficient (N et al. 2007). An alternative ap-
proach is to monitor the water status of the soil
or substrate and make objective irrigation deci-
sions based on real-time measurements (J
2007). Soilless substrates generally hold most of
the water in a matric potential range from –1 to
–10 kPa, with matric potentials of –1 to –5 kPa
accounting for easily available water (EAW) and
water occurring between –5 and –10 kPa be-
ing considered “water buffering capacity” (WBC)
( B, V 1972; A 1998). Knowl-
edge of water availability in the growing media
can be used to determine appropriate thresholds
for automated irrigation. Still, little work has been
done to correlate the commonly defined EAW or
WBC with plant growth (A et al. 2010).
Irrigation has been automated using water ten-
sion measurements for decades (S, W
2011), but few growers currently do so, because
even ’’micro’’- tensiometers are bulky and require
frequent maintenance and refilling. Tensiometers
can easily become dislodged from the substrate,
breaking capillarity and leading to faulty readings
( I et al. 2013). Substrate volumetric wa-
ter content (Θ) has recently become a more feasible
parameter for determining substrate water status
and automating irrigation due to the development
of low-cost sensors (J 2007; N, 
I 2006). By using media-specific water re-
tention curves, it is possible to correlate substrate
Θ with matric potential, and use Θ to determine
thresholds for precision irrigation.
is study compares the effects of timer- and soil
moisture sensor-controlled irrigation on the water
use, yield and quality of lettuce grown in soilless
substrate. It also compares two different Θ thresh-
olds, which were determined based on the substrate
EAW. It was hypothesized that using Θ thresholds
to control irrigation would reduce water use, with-
out affecting lettuce yield and quality.
Plant material and growing conditions. e
experiment was carried out in a greenhouse at the
experimental farm ‘‘La Noria’’ of the Institute of
Sciences of Food Production (CNR - ISPA) in Mola
di Bari (Southern Italy). Seedlings of Lactuca sativa
L. var. capitata cv. Mortarella d’Inverno (S.A.I.S.
Sementi, Cesena, Italy) were obtained from a com-
mercial nursery and transplanted into 5 l plastic
containers (one plant per container) filled with a
soilless substrate (peat-perlite, 1:1 v/v). e sub-
strate was saturated with water before transplant-
ing. Initial substrate solution electrical conductiv-
ity (EC) was 0.8 dS/m as measured with an in situ
EC sensor (WET sensor; Delta T Devices, Burwell,
U.K.). After transplanting, the seedlings were wa-
tered with a nutrient solution (NS) prepared with
pre-collected rain water and containing 8mM
N-NO3, 2mM N-NH4, 5.1mM K, 1.6mM P, 1.2mM
Mg, 2.5mM Ca, 2.8mM S, with micronutrients ap-
plied according to J et al. (1957). e NS
had an EC of 1.5 dS/m and a pH of 6.0. All plants
were well-watered using the NS for 8 days after
transplanting (DAT) to allow the seedlings to es-
tablish. e experiment was terminated at 50 DAT,
when plants reached the commercial size typical
for the cultivar. Mean temperature and relative
humidity inside the greenhouse were 15.6°C and
84.7%, respectively. e mean daily light integral
was 7.84 mol/m2/d during the experiment.
Determination of substrate EAW and irriga-
tion thresholds. Substrate volumetric water con-
Vol. 43, 2016 (2): 67–75 Hort. Sci. (Prague)
doi: 10.17221/312/2014-HORTSCI
tent at –5 kPa (water potential limit for EAW) was
measured using a sand-box (Eijkelkamp Agrisearch
Equipment, Giesbeek, e Netherlands) in accord-
ance with the European Standards EN 13041:1999
(Soil improvers and growing media – Determina-
tion of physical properties – Dry bulk density, air
volume, shrinkage value and total pore space). e
substrate was equilibrated in water, transferred into
tubes made of two overlapping PVC rings (100 ±
1mm diameter and 50 ± 1 mm height each), and
saturated with water for 48 hours. e PVC tubes
with substrate were then moved to the sandbox and
kept at a pressure of –5 kPa at room temperature
until they reached a constant weight. e PVC rings
were removed from the sandbox and separated, af-
ter which the substrate from the lower rings was
weighed and dried at 105°C to a constant weight.
Based on these measurements, it was determined
that the Θ value limit of the EAW was 0.38 m3/m3
for this substrate. Two irrigation thresholds were
chosen accordingly in order to control substrate
Θ at slightly above (0.40 m3/m3) and well below
(0.30m3/m3) the EAW limit.
Treatments and experimental design. e
treatments were: (i) timer-controlled irrigation
(‘Timer’); (ii) irrigation controlled with soil mois-
ture sensors with a Θ thresholds of 0.40 m3/m3
(above the threshold for EAW) (‘Θ = 0.4’), and (iii)
irrigation controlled with soil moisture sensors
with a Θ threshold of 0.30 m3/m3 (value lower than
the EAW limit) (‘Θ = 0.3’). Plants were arranged
in a randomized complete block design with three
replications. e experimental unit was a set of two
plants and containers (subsamples), with one of the
two used to monitor Θ and control irrigation, for a
total of 18 plants used in this experiment (3 treat-
ments × 3 replications × 2 subsamples).
e control system used to irrigate based on Θ
thresholds was similar to that described by N-
 and  I (2006). EC-5 sensors were
used rather than EC-10 sensors (Decagon De-
vices, Pullman, USA), because EC-5 sensors are
less sensitive to substrate electrical conductivity
(EC) and temperature (N et al. 2007). One
sensor was inserted at a ≈ 45° angle into the sub-
strate in each of the 9 measured containers. Sensor
voltage output was measured every 20 min using
a CR1000 datalogger (Campbell Scientific, Logan,
USA) which converted voltage measurements to
Θ using a substrate-specific calibration equation
(Θ = voltage × 3.3007 – 0.2555, r2 = 0.99, 2,500mV
sensor excitation voltage). Each replication of the
‘Θ = 0.3’ and ‘Θ = 0.4’ treatments had a dedicat-
ed pump (Shott 12.10/1400; Shott International,
Cittadella, Italy) and EC-5 sensor. Whenever the
measured Θ dropped below the threshold value
(0.30 or 0.40m3/m3), the datalogger sent a signal to
a relay driver (SDM16AC/DC controller; Campbell
Scientific, Logan, USA) which turned on the pump
to irrigate the 2 containers for 3 minutes. Wa-
ter was allowed to equilibrate in the substrate for
17min before the next measurement and potential
irrigation event. Pumps were submerged in a 500 l
tank filled with NS, and delivered 30 ml/min (90 ml
of NS/irrigation event) to each container through
two pressure-compensated emitters. In the ‘Timer’
treatment, Θ was measured but not used for irriga-
tion control. ese plants were irrigated once daily
(90 ml NS) for 26 DAT and twice a day (180 ml NS)
thereafter using a single submerged pump for the
3replications. is irrigation frequency maintained
a leaching fraction of approximately 20%. Leachate
from each container in all treatments was collected
in buckets, and the volume was measured weekly.
Measurements, calculations and statistical
analysis. e data logger stored the Θ readings from
all sensors every 20 min, the average of the sensor
readings for each measured container every hour,
and the daily number of irrigation events for each
replication of the sensor-controlled treatments.
Daily and total irrigation volumes were calculated
based on the number of irrigations recorded and
the known volume per irrigation event. Leaf chlo-
rophyll content was measured non-destructively us-
ing a handheld leaf chlorophyll meter (SPAD-502;
Minolta, Ramsey, USA) at 42 DAT. Measurements
were taken on ten well-expanded young leaves per
plant, and the averages were recorded for each plant.
Leaf net CO2 assimilation rate (An), stomatal con-
ductance to water vapour (gsw) and transpiration (T)
were measured at 40 DAT using a portable photo-
synthesis system (LI-6400; LI-COR Biosciences,
Lincoln, USA) which provided a photosynthetic
photon flux (PPF) of 1,000 µmol/m2s and a CO2
concentration of 400 µmol/mol. Measured leaves
were allowed to adjust to the measurement condi-
tions for at least 20 min before the values were re-
corded. Plants were harvested, and substrate EC in
each container was measured using a WET sensor
at 50 DAT. e number of leaves was recorded and
the shoot fresh weight of each plant was determined.
Total leaf area was measured using a leaf area me-
Hort. Sci. (Prague) Vol. 43, 2016 (2): 67–75
doi: 10.17221/312/2014-HORTSCI
ter (Li-3100; LI-COR Biosciences, Lincoln, USA).
e leaves and stems of each plant were dried in a
thermo-ventilated oven at 65°C until they reached a
constant weight. Percent dry matter was calculated
as [(dry weight/fresh weight) × 100]. Water use ef-
ficiency (WUE) was calculated as a function of the
applied irrigation water (WUEa = total dry weight
of shoots/irrigation volume applied) and irrigation
water without leaching [WUEr = total dry weight of
shoots/(irrigation volume applied – leachate)]. In-
stantaneous WUE (WUEi) was calculated from the
leaf gas exchange measurements (WUEi = An/T).
Dried leaves were finely ground through a mill
(IKA; Labortechnik, Staufen, Germany) with a
1.0 mm sieve. Leaf nutrient concentrations were
determined using ion chromatography (Dionex
DX120; Dionex Corporation, Sunnyvale, USA)
and a conductivity detector with the IonPackAG14
pre-column and the IonPack AS14 separation col-
umn for anions, and IonPack CG12A pre-column
and IonPack CS12A separation column for cati-
ons. Inorganic anions were measured using 0.5 g of
ground leaf tissue with 50 ml solution containing
3.5mM sodium-carbonate and 1.0mM sodium-bi-
carbonate. Inorganic cations were measured using
1 g of ground leaf tissue, ashed in a muffle furnace
at 550°C and digested with 20 ml 1M HCl in boiling
water for 30 min (E et al. 1996).
Data were subjected to ANOVA using the general
linear model procedure (SAS Institute, Cary, USA);
means were separated by LSD test with P ≤ 0.05
considered to be statistically significant.
Substrate water content, irrigation volume
and water use efficiency, substrate EC
Substrate Θ was different in the three treatments. In
the ‘Timer’ treatment, Θ was higher than 0.45 m3/m3
for the most of the growing cycle and dropped
below this value only during the last part of the
cycle (Fig. 1). e sensor-controlled system gen-
erally maintained Θ close to the irrigation thresh-
olds despite increases in plant size. e average Θ
measured by sensors was 0.461 ± 0.011, 0.412 ±
0.007 and 0.320 ± 0.009 m3/m3 (mean ± sd) in the
‘Timer’, ‘‘Θ = 0.4’’ and ‘‘Θ = 0.3’’ treatments, respec-
tively (for the two sensor controlled treatments, the
reported Θ values are calculated starting from the
beginning of irrigation controlled by the automat-
ed system, after Θ dropped for the first time below
the respective irrigation threshold). e ‘Θ = 0.3’
treatment resulted in greater Θ fluctuations than
did the ‘Θ = 0.4’ treatment (Fig. 1). is is consist-
ent with previous findings (N,  I
2006;  I et al. 2010) and may be because
the hydraulic conductivity of peat-based substrates
decreases at lower water contents (N et al.
2005), resulting in slower water movement, less
uniform water distribution, and increased Θ vari-
ability. It took an average of 9 d for the substrate
of the ‘Θ = 0.4’ treatments to reach the irrigation
threshold (0.40m3/m3) and 23 days for the ‘Θ = 0.3’
treatments to reach the 0.30 m3/m3 threshold.
e most irrigation water was applied in the ‘Tim-
er’ treatment, with 17% less NS used in the ‘Θ = 0.4’
treatment, and 42% less in the ‘Θ = 0.3’ treatment
(Table 1). Approximately 18% of applied NS leached
out from the containers when the timer was used
for irrigation control, while little or no leaching
occurred in the sensor-controlled treatments (Ta-
ble1). Irrigation volumes fluctuated daily in the sen-
sor-controlled treatments due to variability in plant
water consumption and the corresponding changes
in the rate of substrate water depletion (Fig.2). Sen-
sor-controlled irrigation reduces the amount of NS
applied and effectively eliminates leaching. Using Θ
to automate irrigation ensures that NS is provided to
the plant only when water is lost from the substrate
due to plant consumption or evaporation. Limit-
ing the duration and volume of irrigation events
based on container size and substrate water reten-
Fig. 1. Average volumetric water content (Θ) readings
of soil moisture sensors in pots irrigated with a timer or
with an automatic irrigation system based on Θ threshold
(0.30 for ‘Θ = 0.3’ and 0.40 m3/m3 for ‘Θ = 0.4’) measured
by substrate moisture sensors
10 20 30 40 50
Days after transplant
Timer Θ = 0.4 Θ = 0.3
Vol. 43, 2016 (2): 67–75 Hort. Sci. (Prague)
doi: 10.17221/312/2014-HORTSCI
tion properties maximizes the efficiency of sensor-
controlled irrigation systems. Leaching from soilless
substrates can generally be minimized by reducing
the duration of each irrigation event, thereby ap-
plying less water at one time (Y et al. 1997;
B,  I 2008). In our experiment, the
leaching fraction in the ‘Timer’ treatment was lower
than is typical for soilless production systems, since
it is common in substrate systems to apply 30–50%
more water than is used by the crop (K
2001), suggesting that the water saving obtained us-
ing moisture sensors could even be higher in com-
mercial growing conditions.
Water use efficiency calculated based on the ap-
plied irrigation water is a measure of whole system
(irrigation and cultivation system combined) ef-
ficiency, which takes into account both the actual
plant water use and the water lost through leach-
ing. In the ‘Timer’ treatment, WUEa was the low-
est because of the large volume of NS that was ap-
plied, and WUEa was the highest in the ‘Θ = 0.3’
treatment, which used the least NS (Table 1). e
substantial leaching that generally occurs with tim-
er-based irrigation decreases its WUEa. Reducing
leaching during production by growing plants at
the optimal substrate water content and growing
species with high water-use efficiency have been
recognized as crucial approaches to efficient wa-
ter use (N,  I 2008). e water use
efficiency of the plants can be estimated from the
biomass and the amount of NS that was retained
by the substrate (i.e., NS applied – leached). e
‘Θ = 0.3’ treatment resulted in the highest WUEr,
and there was no difference in WUEr between the
‘Timer’ and ‘Θ = 0.4’ treatments (Table 1).
However, when calculating water use efficiency,
it is also important to account for the change in the
amount of water present in the substrate over the
course of the growing cycle. e Θ did not change
much in the ‘Timer’ and ‘Θ = 0.4’ treatments, but
decreased from 0.48 to 0.30 m3/m3 (approximately
900 ml/container) in the ‘Θ = 0.3’ treatment. Tak-
ing into account this additional amount of water
used by the plants in the ‘Θ=0.3’ treatment reduces
the WUEr to approximately 3.1 g/l, similar to that
in the other treatments.
Table 1. Applied nutrient solution (NS), volume of leachate, water use efficiency (WUE), and substrate electrical
conductivity (EC) in soilless cultivation of lettuce where irrigation management was performed with a timer or with
an automatic irrigation system based on Θ threshold (0.30 for ‘Θ = 0.3’ and 0.40 m3/m3 for ‘Θ = 0.4’) measured by
substrate moisture sensors
Treatment Applied NS (ml/plant) Leachate (ml/plant) WUEa
2 (g/l) WUEr
3 (g/l) Substrate EC (dS/m)
Timer 5,310a 933a2.36c2.86b1.1b
Θ = 0.4 4,410b 59b2.95b2.99b1.1b
Θ = 0.3 3,060c 0b4.02a4.02a1.4a
Significance1*** *** *** ** ***
1mean separation within columns by LSD0.05; **, *** – significant at P ≤ 0.01 and P ≤ 0.001, respectively; 2calculated as a
function of the applied irrigation water; 3calculated as a function of the irrigation water retained in the substrate; within
columns, values followed by the same letters are not significantly different
Fig. 2. Daily irrigation volume
for lettuce plants irrigated with
a timer or with an automatic
irrigation system based on Θ
threshold (0.30 for ‘Θ=0.3’ and
0.40 m3/m3 for ‘Θ=0.4’) meas-
ured by substrate moisture
10 20 30 40 50
Days after transplant
Timer Θ = 0.4 Θ = 0.3
Daily irrigation volume
Days after transplant
Timer Θ=0.4 Θ=0.3
Hort. Sci. (Prague) Vol. 43, 2016 (2): 67–75
doi: 10.17221/312/2014-HORTSCI
Electrical conductivity was slightly higher in the
‘Θ = 0.3’ treatment (Table 1), likely because of the
absence of leaching and accumulation of fertilizer
salts. Similar results were observed by B
and  I (2008). High substrate EC may
negatively affect plant growth by imposing osmotic
stress. is is a potential problem that should be
taken into account when using sensor-controlled
irrigation, especially with salt-sensitive species or
low quality (high EC) irrigation water.
Plant growth, photosynthetic activity
and tissue analysis
At the end of the growing cycle, plants had a
similar number of leaves in all treatments, but the
plants irrigated at the lowest Θ showed, on aver-
age, a 11.7% decrease in leaf area (Table 2). Plants
in the ‘Timer’ and ‘Θ = 0.4’ treatments had higher
fresh weights (24%) than plants irrigated at the
lowest Θ threshold (Table 2). No differences in dry
weight were observed among treatments. us, the
irrigation treatments had little or no effect on bio-
mass production, and differences in fresh weight
resulted from differences in plant water content.
Percent dry matter was 20% higher in the ‘Θ = 0.3’
treatment than in the treatments with higher fresh
weights. In minimally-processed greens, a high
dry matter percentage is desirable because low dry
matter content can decrease shelf life (M
et al. 2011). Our results suggest that precision irri-
gation can be used to increase dry matter content,
thereby improving the quality of lettuce in soilless
cultivation. e ‘Θ = 0.3’ plants irrigated at the low-
est Θ, showed, on average, an 11.7% decrease in leaf
area (Table 2). Reduced water availability leads to
decreased leaf size because even mild drought can
reduce the turgor needed for cell expansion during
leaf development (B 1970). Water availability
in soilless substrates is reduced rapidly when Θ ap-
proaches a substrate-specific threshold (W
2008) and the ‘Θ = 0.3’ treatment apparently im-
posed enough of drought stress to reduce leaf elon-
gation. e reduced leaf area in this experiment
was consistent with the lower tissue water con-
tent observed in the ‘Θ = 0.3’ treatment, in which
Θ was maintained below the generally recognized
limit for EAW in soilless substrates ( B,
V 1972; A 1998). However, no visual
symptoms of water stress were observed in any of
the plants, indicating that the drought stress in the
Θ=0.3’ treatment was not severe. is was consist-
ent with the lack of an effect on shoot biomass.
Leaf chlorophyll content, net CO2 assimilation
rate, stomatal conductance and leaf transpiration
were similar in all treatments (Table 3). Since gas
exchange parameters were similar, WUEi was also
similar for all treatments. However, WUEa was
higher in the sensor-controlled treatments (Table
1). Leaf gas exchange measurements are limited to
a particular leaf and specific time, and may not ac-
curately represent long-term or whole-plant pro-
cesses. When calculated using leaf gas exchange
measurements, WUE is not always consistent with
the final WUE based on biomass and yield (G
et al. 2012; T et al. 2012; W et al. 2013).
In this study, it was demonstrated that, although
WUEi was unaffected, the overall water use effi-
ciency (WUEa) of an irrigation system can be im-
proved by adopting sensor-control.
Leaf tissue chemical composition was not affect-
ed by the treatments, with the exception of nitrate
concentration, which was lowest in the ‘‘Θ = 0.3’
treatment (Table 4). is may be because less NS,
and thus less nitrate, was applied in the ‘Θ = 0.3’
Table 2. Leaf area and number, total fresh and dry weight, and total dry matter of lettuce plants grown in soilless
conditions and with irrigation management performed with a timer or with an automatic irrigation system based on
Θ threshold (0.30 m3/m3 for ‘Θ = 0.3’ and 0.40 m3/m3 for ‘Θ = 0.4’) measured by substrate moisture sensors
Treatment Leaf area
Leaf number
per plant
Total fresh weight
Total dry weight
Dry matter
Timer 3,914a36 273.3a12.5 4.58b
Θ = 0.4 3,889a33 267.0a13.0 4.87b
Θ = 0.3 3,446b33 217.1b12.3 5.67a
Significance1*ns *ns **
1mean separation within columns by LSD0.05; ns, *, ** – non-significant or significant at P ≤ 0.05 and
P ≤ 0.01, respectively; within columns, values followed by the same letters are not significantly different
Vol. 43, 2016 (2): 67–75 Hort. Sci. (Prague)
doi: 10.17221/312/2014-HORTSCI
treatment (Table 1). Moreover, a strong negative
correlation between nitrate and dry matter content
has been demonstrated in butterhead lettuce culti-
vars (R et al. 1987), similar to our findings.
is relationship between nitrate and dry matter
content is explained by the fact that a high dry mat-
ter content is normally associated with high organic
solutes in the cell vacuole (R, B-Z-
 1989), thus reducing the plant accumulation
of nitrates to compensate for a lower concentration
of organic solutes (R 1993). However, none
of the plants showed any visual symptom of nitro-
gen deficiency and leaf chlorophyll readings were
similar in all treatments, suggesting that nutritional
needs were met in all treatments. High nitrate con-
centrations in leafy greens can be a health hazard,
and in some cases (i.e., European countries), regu-
lations limit the acceptable nitrate concentration
of vegetables. Precision irrigation could be used
to improve lettuce quality by reducing leaf nitrate
Potential economic impact
Sensor-controlled irrigation can have a positive
economic impact on greenhouses through a variety
of ways: reducing water cost, less energy required to
pump water, labour savings resulting from automa-
tion, improved crop quality and/or shorter produc-
tion cycles. Some of these potential benefits will differ
based on locations, since the cost of water, energy, and
labour varies. In one case study in the South-eastern
United States, it was shown that precision irrigation
using wireless sensor networks increased annualized
profits of the production of Gardenia jasminoides
by 156% (L et al. 2013). is increase
in profits resulted largely from better growth and a
shorter production cycle, and to a lesser extent from a
reduction in plants lost due to damage by root patho-
gens. No similar economic analysis has yet been con-
ducted for lettuce production.
A survey of US greenhouse and nursery growers
showed widespread interest in adoption of wireless
sensor networks for sensor-controlled irrigation.
L et al. (2015) suggested that the ini-
tial adoption rate of wireless sensor networks may
be high, based on the expected cost of such sys-
tems and the growers’ willingness to pay for them.
Whether this holds true in other parts of the world
is not yet clear.
In conclusion, sensor-controlled irrigation with
a set-point above the EAW limit (‘Θ = 0.4’ treat-
ment) had similar plant fresh weight and quality
as timer-controlled irrigation, but used less irriga-
tion volume. Maintaining a substrate moisture lev-
Table 3. Chlorophyll content, net CO2 assimilation rate (An), stomatal conductance to water vapour (gsw), leaf tran-
spiration (T) and instantaneous water use efficiency (An/T, WUEi) of lettuce plants grown in soilless conditions and
with irrigation management performed with a timer or with an automatic irrigation system based on Θ threshold
(0.30 m3/m3 for ‘Θ = 0.3’ and 0.40 m3/m3 for ‘Θ = 0.4’) measured by substrate moisture sensors
Treatment Chlorophyll content
(SPAD units)
Timer 33.9 18.8 0.94 4.74 3.98
Θ = 0.4 33.6 18.8 0.81 4.80 3.94
Θ = 0.3 34.5 19.4 0.78 4.46 4.40
Significance1ns ns ns ns ns
1mean separation within columns by LSD0.05; ns – non-significant
Table 4. NO3, K, Mg and Ca content (g/kg dry weight) in
leaf tissues of lettuce plants grown in soilless conditions
and with irrigation management performed with a timer
or with an automatic irrigation system based on Θ thresh-
old (0.30 for ‘Θ = 0.3’ and 0.40 m3/m3 for ‘Θ = 0.4’) meas-
ured by substrate moisture sensors
Treatment NO3KMg Ca
Timer 55.0a89.2 5.6 13.4
Θ = 0.4 49.5a90.9 5.1 11.0
Θ = 0.3 33.4b74.8 5.7 13.7
Significance1*** ns ns ns
1mean separation within columns by LSD0.05; ns, *** – non-
significant and significant at P ≤ 0.001, respectively; within
columns, values followed by the same letters are not sig-
nificantly different
Hort. Sci. (Prague) Vol. 43, 2016 (2): 67–75
doi: 10.17221/312/2014-HORTSCI
el slightly below the conventionally defined EAW
(‘Θ = 0.3’ treatment) range reduced the water con-
tent and nitrate concentration of lettuce grown in
soilless substrate but did not reduce overall biomass
production. Sensor-controlled irrigation resulted
in higher overall water and nutrient use efficiency
than timer-controlled irrigation. Precision irrigation
based on Θ measurements eliminated leaching while
improving the quality of soilless-grown lettuce.
We thank Gerolmina Florio and Nicola Gentile
for their technical assistance and Geoffrey Weaver
for editing this manuscript.
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Received for publication November 19, 2014
Accepted after corrections September 7, 2015
Corresponding author:
Dr. A P, Institute of Sciences of Food Production, National Research Council, Via G. Amendola, 122/O,
70126 Bari, Italy; e-mail:
Hort. Sci. (Prague) Vol. 43, 2016 (2): 67–75
doi: 10.17221/312/2014-HORTSCI
... Sensor-based irrigation management has been recently applied to different vegetable soilless crops: important water saving, increased WUE and almost no leaching are reported with moisture sensor-based compared to timer-based irrigation in lettuce [8,9] and rocket [10]; substrate water content and electrical conductivity (EC) probes were used on coir grown tomato, resulting in on-demand irrigation with better control of leaching compared to timer use [11]; leaching was reduced to optimal target values for efficient irrigation in free-drain soilless culture (i.e., <10−15%) in the case of greenhouse basil irrigated based on dielectric sensors [12]. ...
... Beside impacting on water consumption and crop performance in terms of yield, irrigation management can also affect quality parameters of vegetables. It has been demonstrated that the application of sensor-based controlled water stress conditions influenced positively quality parameters of lettuce [8] and tomato [13]. However, under-irrigation generally results in reduced crop yield and quality [14]; therefore, when irrigation is managed in such a way as to reduce water supply compared to common practice, water saving should anyhow guarantee the maintenance of high quality standards. ...
... and SENSOR_0.25 automatic irrigations stopped at the set-points differentiation moment and started again after 3 and 5 days, respectively, when the final irrigation set-point was reached for the first time ( Figure 2). Similar VWC trends were observed in a comparison study between timer-and sensor-based irrigation of soilless lettuce [8]. ...
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Real-time monitoring of substrate parameters in the root-zone through dielectric sensors is considered a promising and feasible approach for precision irrigation and fertilization management of greenhouse soilless vegetable crops. This research investigates the effects of timer-based (TIMER) compared with dielectric sensor-based irrigation management with different irrigation set-points [SENSOR_0.35, SENSOR_0.30 and SENSOR_0.25, corresponding to substrate volumetric water contents (VWC) of 0.35, 0.30 and 0.25 m3 m−3, respectively] on water use, crop performance, plant growth and physiology, product quality and post-harvest parameters of soilless green bean (Phaseolus vulgaris L., cv Maestrale). In SENSOR treatments, an automatic system managed irrigation in order to maintain substrate moisture constantly close to the specific irrigation set-point. The highest water amount was used in TIMER treatment, with a water saving of roughly 36%, 41% and 47% in SENSOR_0.35, SENSOR_0.30 and SENSOR_0.25, respectively. In TIMER, the leaching rate was ≈31% of the total water consumption, while little leaching (<10%) was observed in SENSOR treatments. TIMER and SENSOR_0.35 resulted in similar plant growth and yield, while irrigation set-points corresponding to lower VWC values (SENSOR_0.30 and SENSOR_0.25) resulted in inadequate water availability conditions and impaired the crop performance. The study confirms that rational sensor-based irrigation allows to save water without compromising anyhow the product quality. In SENSOR irrigation management, in fact, especially in the case of optimal water availability conditions, it was possible to obtain high quality pods, with fully satisfactory characteristics during storage at 7 °C for 15 days.
... A abordagem que utiliza o acompanhamento do status hídrico do solo torna a decisão de irrigar mais eficiente, pois se relaciona à disponibilidade hídrica às plantas e pode ser sustentada em medições realizadas em tempo real (MONTESANO; VAN IERSEL;PARENTE, 2016). Atualmente, existem diversos controladores de irrigação no mercado que regulam o conteúdo de água no solo a partir de medições realizadas por sensores. ...
... A abordagem que utiliza o acompanhamento do status hídrico do solo torna a decisão de irrigar mais eficiente, pois se relaciona à disponibilidade hídrica às plantas e pode ser sustentada em medições realizadas em tempo real (MONTESANO; VAN IERSEL;PARENTE, 2016). Atualmente, existem diversos controladores de irrigação no mercado que regulam o conteúdo de água no solo a partir de medições realizadas por sensores. ...
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TENSIÔMETROS ELETRÔNICOS INTEGRADOS A PLACA MICROCONTROLADORA ARDUINO NO MANEJO DA IRRIGAÇÃO DE ALFACE EM DIFERENTES POTENCIAIS MATRICIAIS CRÍTICOS E TIPOS DE SOLO RODRIGO MOURA PEREIRA1; DELVIO SANDRI1 E GERVÁSIO FERNANDO ALVES RIOS1 1Faculdade de Agronomia e Medicina Veterinária, Universidade de Brasília, Campus Universitário Darcy Ribeiro, S/N, CEP: 70910-900, Brasília, DF, Brasil,,, 1 RESUMO O uso racional da água na irrigação é fundamental para a conservação dos recursos hídricos. Nesse sentido, sistemas de automação de irrigação baseados na variação do potencial matricial do solo podem ser empregados como ferramenta para o uso eficiente da água em sistemas irrigados. Objetivou-se avaliar respostas da alface, cv. Wanda, submetida à potenciais matriciais críticos de irrigação controlados por tensiômetros eletrônicos. Os tensiômetros foram integrados a uma placa microcontroladora Arduino para controle da automação de irrigação. Adotou-se o delineamento experimental em blocos completos casualizados com quatro repetições, tendo como potenciais matriciais críticos -15, -20, -25 e -30 kPa em Latossolo Vermelho Amarelo e -10, -15, -20 e -25 kPa em Neossolo Regolítico. Aos 33 dias após o transplantio, foram obtidos parâmetros fenométricos da alface, índice Falker de clorofila e a Eficiência do Uso da Água (EUA). O sistema de automação monitorou e registrou os potenciais ao longo do ciclo da alface, acionou e interrompeu a irrigação de acordo com os potenciais críticos adotados. Os potenciais matriciais apresentaram variações médias em relação aos valores críticos para acionamento e interrupção da irrigação entre 1,45% e 5,50% no Latossolo Vermelho Amarelo e entre 2,90% e 15,50% no Neossolo Regolítico, respectivamente. A adoção de potenciais críticos abaixo de -15 kPa em Neossolo reduz significativamente a frequência de irrigação. O maior peso de matéria fresca foi obtido no potencial matricial de -10 kPa em Neosolo Regolítico e a maior EUA foi obtida na irrigação acionada no potencial de -15 kPa em Latossolo Vermelho Amarelo. Keywords: tensão de água no solo, automação, irrigação de precisão. PEREIRA, R. M.; SANDRI, D.; RIOS, G. F. A. ELECTRONIC TENSIOMETERS INTEGRATED WITH ARDUINO MICROCONTROLLER IN IRRIGATION MANAGEMENT OF LETTUCE SUBMITTED TO DIFFERENT CRITICAL MATRIC POTENTIALS AND SOIL TYPES 2 ABSTRACT The rational use of water in irrigation is fundamental for the conservation of water resources. Irrigation automation based on the variation of the soil matrix potential can be used as a tool for the efficient water use in irrigation. This study aimed to evaluate lettuce, cv Wanda responses to soil water potentials for irrigation controlled by electronic tensiometers. The tensiometers were integrated with an Arduino microcontroller to control an irrigation automation system. A randomized complete block design with four replications was adopted, with critical potentials of -15, -20, -25, and -30 kPa in Red Yellow Latosol and -10, -15, -20, and -25 kPa in Regolitic Neossol. At 33 days after transplanting, lettuce phenometric parameters, chlorophyll Falker index, and water use efficiency (EUA) were obtained. The automation system monitored and recorded the potentials throughout the lettuce cycle and triggered and stopped the irrigation according to the critical potentials adopted. The soil water potentials showed average variations to the critical values for starting and stopping irrigation between 1.45% and 5.50% in the Oxisol and between 2.90% and 15.50% in the Regolitic Neossol respectively. The adoption of critical potentials above -15 kPa in Neossolo significantly reduces the frequency of irrigation. The highest fresh matter weight was obtained at the matrix potential of -10 kPa in Regolitc Neossol and the highest EUA was obtained in -15 kPa in the Red Yellow Latosol. Keywords: soil water tension, automation, precision irrigation
... Malaysia which has equatorial climate receives 12-13 daylight hours and has high humidity (70%-90%) thus watering is generally done 2 times a day in the early morning and late evening. Montesano et al. (2016) studied the implementation of timer-based irrigation against moisture sensor-based irrigation which resulted in timer-based irrigation having less water efficiency compared to moisture-based irrigation. In Malaysia, an irrigation timer costs around RM50 -RM100 per piece and the required quantity depends on the number of available water-taps in the plantation area. ...
... Moisture sensors can be operated using soil resistivity measurements, tensiometers, infrared moisture balance measurements and dielectric techniques (Munoth et al., 2016). A study by Montesano et al., (2016) shows that different volumetric water content treatment will result in decrease in leaf area even though the products have the same final dry weight which shows that a precise set point of the sensors need to be determined in order to produce a high-quality product. Amiri et al., (2021) conducted a study to determine the appropriate location of the tensiometers in agriculture which recommended the tensiometers to be installed at a distance of 5-20 cm horizontal to the plant and 10-20 cm depth from soil surface. ...
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Community farming is an initiative set out by the Malaysian Government to help the low-income group in reducing their household expenditure thus increasing the income of the members. The farm is cultivated in a designated land area near the residence by the community members. Although a fully automated system is available for mass plantation and agriculture industry, the same implementation in community farming is limited since community farming is relatively new and meant for sustenance rather than profit. In Malaysia recently, irrigation efficiency is approximated at 40% to 50% and becomes a challenge to water resource sustainability. It is crucial to study the feasibility of upgrading the community farming to make it more standalone, automated and easier to be cared for by the community members. The objective of this paper is to present a review on the Rainwater Harvesting System (RWHS) sustainability and automated irrigation method suitable for implementation in community farms. This paper further highlights the importance of introducing automated systems in community farms to benefit and improve the economy and social aspects of low-income group earners. The result shows the adoption of RWHS for irrigation purposes in various countries gives positive impacts on sustainability. The study also shows that various methods have been implemented in the agriculture industry in terms of irrigation including timer based, sensor based and plant based in combination with controllers such as Arduino or PIC microcontroller. Sensor based presented a precise watering system which takes into account parameters such as soil moisture, temperature, humidity and overwatering. Malaysia with high annual rainfall and installation of automated irrigation with rainwater harvesting will improve community farms which are generally located in urban areas without natural water resources. The notable contribution of this paper is highlighting the importance of improving community farms in terms of technological advancement with the implementation of automated irrigation and rainwater harvest integration. This will provide a sustainable solution for community farms in Malaysia.
... Least processed or fresh-cut leaf vegetables, such as lettuce (Lactuca sativa L.), come into prominence in world vegetable market (Montesano et al. 2016). Lettuce is among the most widely consumed vegetables worldwide (Coelho et al. 2005). ...
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This study was conducted in Meram town of Konya province under unheated greenhouse conditions in 2019 autumn (September–November) and 2020 spring (February–April) growing periods. Davidole (Lactuva sativa L. var. longifolia) curly lettuce cultivar was used as the plant material of the present study. Experiments were conducted in randomized blocks design with three replications. Irrigation levels were arranged by applying certain percentage of 4‑day cumulative evaporations from Class‑A pan (60%, 80%, 100% and 120%) and effects of irrigation treatments on yield, yield components and water use efficiencies of lettuce plants were investigated. Crop water consumptions in S60, S80, S100 and S120 treatments were respectively measured as 136.2, 149.6, 163 and 168.4 mm in 2019 and as 110.6, 123.8, 136 and 146.2 mm in 2020. In terms of commercial head weights, in 2019, the lowest value (623 g) was obtained from S60 treatment and the greatest (1130.8 g) from S120 treatment; in 2020, the lowest (900.8 g) from S60 and the greatest (1177.8 g) from S100 treatments. Water use efficiency (WUE) values varied between 38.12–55.96 kg m⁻³ in 2019 and between 61.65–75.24 kg m⁻³ in 2020. Irrigation water use efficiency (IWUE) values varied between 43.19–56.19 kg m⁻³ in 2019 and between 60.82–81.85 kg m⁻³ in 2020. Lettuce yield-response factor (ky) was calculated as 2.26 for 2019 and 0.69 for 2020. For lettuce cultivation under unheated greenhouse conditions of Konya province, S100 treatment could be recommended for autumn (September–November) productions and S80 treatment for spring (February–April) productions.
... In the experiment, however, all cultivars responded similarly to the set conditions in all monitored growth parameters. However, each crop needs a specific optimal composition, electric conductivity values and nutrient solution pH, which affects fruit quality as well as the benefits of gradual harvests, as shown in studies on the benefits of growing tomatoes, peppers and lettuce in a greenhouse using technologies without substrate and hydroponics (Tzortzakis and Economakis 2008, Montesano et al. 2016, Amalfitano et al. 2017. Similarly, Buckseth et al. (2016) and Rykaczewska (2016) stated that optimisation of aeroponics technology is still necessary for specific environmental conditions and individual potato cultivars. ...
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Aeroponics would appear to have a number of potential attributes to make potato production more efficient. In a 3-year experiment, from 2019 to 2021, potatoes were grown in aeroponic units using two nutrient solutions as well as in a conventional polycarbonate greenhouse in a substrate. Potato cultivars Adéla, Zuza and Ornella were used in all experiment years. No statistically significant effect of nutrient solution or potato cultivar on the number and weight of tubers was found in the trial. However, the advantages of aeroponics over conventional technology were statistically proven. The number of tubers per plant in aeroponic units ranged from 2.4 (2019, cv. Adéla) to 41.0 (2021, cv. Zuza), while in the greenhouse, they ranged from 3.9 (2019, cv. Adéla) up to 12.6 (2021, cv. Adéla). The average weight of tubers in aeroponic units ranged between 2.0 g and 9.9 g per plant (2 to 10 successive harvests), and in the greenhouse, 22.7 g to 41.9 g per plant (single harvest). The influence of cultivar on the average weight of tubers within individual cultivation technology variants was statistically proven only for polycarbonate greenhouse: only one harvest after the end vegetation.
... van-Iersel et al. (2009) used soil moisture probes to open and close solenoid valves based on the amount of water in the substrate. Precision sensor-controlled irrigation based on volumetric moisture content measurements is an effective tool for increasing overall WUE and improving the quality of soilless-grown lettuce by acting on the substrate moisture level ( Montesano et al. 2016). Automation adoption is minimal, however, because tension-based irrigation necessitates frequent maintenance and refilling. ...
Overexploitation of limited freshwater resources has resulted from the increasing food demand and faster economic development in India and the world as well. Changes in climatic conditions and contamination of freshwater bodies have made freshwater resources scarce. When compared to domestic and industrial use, agriculture becomes the leading sector in terms of water footprint (WF). Reducing WF in agriculture is a more difficult task, particularly with irrigated crops, and it becomes a critical component of water management, especially in moisture‐stressed or drought‐prone areas. India has the highest freshwater demand for agriculture in the world, accounting for 91% of total water use, versus 4% for industry and 5% for domestic use. However, Water scarcity has emerged as the most significant constraint to crop production, particularly in arid and semi‐arid agro‐ecologies. Water supply per capita in India has decreased from 5177 m 3 in 1951 to 1441 m 3 in 2015 and is projected to decrease further to 1174 m 3 by 2050. As a result, since India is a water‐stressed nation, it requires innovative agricultural practices and policies to significantly reduce WF. In comparison to other crops, cereal crop production needed more than half of the total available water for agriculture. This increase in WF in cereals may be due to higher evapotranspiration demands combined with higher‐yielding efficiency. In this context, a well‐designed precision water management system is critical for maintaining cereal, commercial crop, and horticultural crop production while improving product quality. To reduce WFs, the precise use of usable water supplies is important. Precision water management, which includes the judicious use of water through sensors and micro‐irrigation strategies, is essential for ensuring the long‐term sustainability of water supplies. It also means that high‐quality water is applied precisely at the right time, in the right place, and at the right stage of crop development, but uniformly across the chosen area. Sensor‐based micro‐irrigation techniques such as drip irrigation, subsurface drip irrigation, sprinkler irrigation, image irrigation, and tissue irrigation may be used to achieve precision. Low‐cost agronomic practices such as scheduling irrigation, conservation agriculture, alternative wetting and drying, direct‐seeded rice (DSR), and mulching are examples of precision irrigation management. As a result, having a comprehensive understanding of WFs in crop production will help to resolve issues such as climate change, overuse of freshwater resources, and so on. As a result, this article precisely and sustainably explains the fundamentals of WFs and water resource management.
... ial to match water requirements to the water supply while responding to solar radiation levels.PID Smart irrigation mobile robot performed as expected with forward and circular motions.Open fieldTime-based The system can supply water continuously for the plants at a particular time.Improved weight and quality of lettuce, less irrigation water used.Montesano et al. (2016) Open field Fuzzy logic Fuzzy logic can solve uncertainties and non-linearities of an irrigation system and establish a control model for high-precision irrigation.Neural network models with one hidden layer with four neurons for sugar beet and five neurons for wine grape provided excellent predictions of well-watered canopy temperature. ...
The demand for freshwater resources has increased in recent times and has been exacerbated by escalating global population and increasing drought indices in the world’s agricultural zones. Irrigated agriculture is inevitably a wasteful water user that has deprived other sectors of the scarce resource. Improving water use efficiency in irrigated agriculture is therefore crucial for sustainable agricultural production to thrive. There is potential to improve water use efficiency through smart irrigation systems, especially with the advent of wireless communication technologies, monitoring systems, and advanced control strategies for optimal irrigation scheduling. This paper reviews state-of-the-art smart monitoring and irrigation control strategies that have been used in recent years for irrigation scheduling. From the literature review, closed-loop irrigation control strategies are efficient than open-loop systems which do not cater for uncertainties. It is argued that combining soil-based, plant, and weather-based monitoring methods in a modelling environment with model predictive control can significantly improve water use efficiency. This review shall help researchers and farmers to choose the best irrigation monitoring and control strategy to improve irrigation scheduling in open field agricultural systems.
... Subsequently, by bringing pH me and θ into the compensation model, the adjusted pH value can be figured out. It should be noticed that most soil water content sensors are designed to measure volumetric water content (VWC) of soil [38]- [40], which should be converted to MWC (θ m = θ v * ρ −1 d , θ m : mass water content, θ v : volumetric water content; ρ d : dry density of substrate). ...
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pH of soilless culture substrate is an important and frequently measured property in facility agriculture. Compared with laboratory analysis, pH direct measurement (pH-DM) involving the direct insertion of a pH sensor into soil or substrates, is rapid, efficient, and inexpensive. This method requires a reliable pH sensor and exhibits a significant measuring error of 0.8 to 1.1. In this study, all-solid-stated pH sensors were fabricated on alumina substrate through magnetron sputtering. Substrates containing mixed peat and vermiculite were prepared to examine the effects of mass water content (MWC) and mixture ratio on the pH-DM method. Statistical analysis of the measured pH values demonstrated that MWC and mass ratio of peat ( $\boldsymbol {\eta }_{{peat}}$ ) evidently influenced pH-DM. Specifically, in the unsaturated substrate, the errors of pH-DM were highly and negatively correlated with MWC but positively correlated with $\boldsymbol {\eta }_{{peat}}$ . The measured pH values also exhibited wide dispersion in the substrates with high $\boldsymbol {\eta }_{{peat}}$ or extremely low MWC. Furthermore, a two-factor compensation model was established and evaluated. The compensation results indicated that the maximum error with pH-DM method decreased from −1.63 to −0.66 pH unit, and the fluctuation coefficient of pH-DM decreased from 0.796 to 0.264. The influence rules of MWC and $\boldsymbol {\eta }_{{peat}}$ on errors in the pH-DM method, as well as the proposed compensation model, are useful in improving the accuracy and robustness of pH-DM and can contribute to rapid and efficient pH measurements in soilless culture substrate.
... Some plants in all treatments experienced some tip burn on the outer leaves. Average water use efficiency in WBT2 based on dry weight (4.22g/L) is similar to the best WUE (4.02g/L) in hydroponic lettuce (Montesano et al., 2016). However, WUE based on wet weight (85.1 -123.6g/L) is much greater than WUE for wicking bed lettuce in Semananda et al. ...
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Wicking beds are planting containers that have a reservoir of water in the lower portion providing moisture to plants using capillary action. The scientific literature has findings from a few studies that wicking beds have a higher yield and greater water use efficiency than top watered containers but no research has been found about the effects of different materials in the reservoir layer. This study investigated the capillary rise, water holding capabilities and performance in wicking bed reservoirs of several materials. Capillary rise of water in various materials was measured in Perspex tubes. Crusher dust had the greatest capillary rise, followed by sand, fine perlite and a cocopeat/compost/sand mix. Gravel and scoria had poor capillary rise. Wicking beds were constructed with four reservoir treatments – cocopeat mix, sand, gravel and WaterUps® with medium grade perlite as the wicking medium. A cocopeat/compost/sand mix was used as the growing medium for each reservoir treatment. A commercial potting mix was also used with a sand reservoir. Three replicates of each treatment were performed. Two crops were grown sequentially: spinach then butterhead lettuce. For the spinach crop, the cocopeat and sand/cocopeat beds grew the greatest plant weight followed by WaterUps®, gravel, and sand/potting mix. Soil moisture at 150mm depth was lowest in gravel, followed by WaterUps®, sand/cocopeat, cocopeat and sand/potting mix. For growing lettuce, the wicking material in the WaterUps® was changed to sand. There was no significant difference in the weight of lettuce grown in any of the treatments. Soil moisture at 150mm depth remained reasonably constant throughout the growing period for WaterUps® and cocopeat. Gravel and sand/potting mix dried the most. The potting mix remained wettest of all treatments at 200mm depth but was driest at 100 and 50mm depths indicating that it had poor capillary rise capabilities. This study found the reservoir material has an effect on the soil moisture and plant growth in wicking beds. Although often used, gravel appears a poor choice since it results in the driest growing medium. The reservoirs with cocopeat mix and sand delivered better soil moisture and plant growth. WaterUps® with sand as the wicking material also delivered a high level of soil moisture.
... Greenhouse soilless production can boost intensive cropping systems with impressive efficiency on water and nutrients use, and very high product yield and quality [28]. Both sensor-based irrigation management [29][30][31] and the rational application of fertilizers [32,33] have been identified as promising approaches in combining high product quality with sustainable use of resources in greenhouse soilless vegetables production. ...
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Computer Vision Systems (CVS) represent a contactless and non-destructive tool to evaluate and monitor the quality of fruits and vegetables. This research paper proposes an innovative CVS, using a Random Forest model to automatically select the relevant features for classification, thereby avoiding their choice through a cumbersome and error-prone work of human designers. Moreover, three color correction techniques were evaluated and compared, in terms of classification performance to identify the best solution to provide consistent color measurements. The proposed CVS was applied to fresh-cut rocket, produced under greenhouse soilless cultivation conditions differing for the irrigation management strategy and the fertilization level. The first aim of this study was to objectively estimate the quality levels (QL) occurring during storage. The second aim was to non-destructively, and in a contactless manner, identify the cultivation approach using the digital images of the obtained product. The proposed CVS achieved an accuracy of about 95% in QL assessment and about 65–70% in the discrimination of the cultivation approach.
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Moisture characteristic curves (MCC) relate the water content in a substrate to the matric potential at a given tension or height. These curves are useful for comparing the water-holding characteristics of two or more soils or soilless substrates. Most techniques for developing MCC are not well suited for measuring low tensions (0 to 100 cm H2O) in coarse substrates used in container nursery production such as those composed of bark. The objectives of this research were to compare an inexpensive modified long column method with an established method for creating low-tension MCCs and then to determine the best model for describing MCCs of bark-based soilless substrates. Three substrates composed of douglas fir (Pseudotsuga menziesii) bark alone or mixed with either peatmoss or pumice were used to compare models. Both methods described differences among the three substrates, although MCC for each method differed within a substrate type. A four-parameter log-logistic function was determined to be the simplest and most explanatory model for describing MCC of bark-based substrates.
A fundamental way to schedule irrigation is through the monitoring and management of soil water tension (SWT). Soil water tension is the force necessary for plant roots to extract water from the soil. With the invention of tensiometers, SWT measurements have been used to schedule irrigation. There are different types of field instruments used to measure SWT, either directly or indirectly. Precise irrigation scheduling by SWT criteria is a powerful method to optimize plant performance. Specific SWT criteria for irrigation scheduling have been developed to optimize the production and quality of vegetable crops, field crops, trees, shrubs, and nursery crops. This review discusses known SWT criteria for irrigation scheduling that vary from 2 to 800 kPa depending on the crop species, plant product to be optimized, environmental conditions, and irrigation system. By using the ideal SWT and adjusting irrigation duration and amount, it is possible to simultaneously achieve high productivity and meet environmental stewardship goals for water use and reduced leaching.
Maintaining medium pH and nutrient concentrations at levels acceptable for growth are important for producing vigorous transplants in the shortest time. Medium chemical properties, such as cation-exchange capacity, aeration, liming materials, preplant fertilizer, irrigation-water sources, water-soluble fertilizers, and plant species, interact to affect medium pH and nutrient management. However, these chemical properties do not affect medium pH or the nutrient supply simultaneously or with equal intensity. The objective of this review is to consider key chemical properties of container media and their affects on pH and nutrient management initially and over time.
Improvements in sensor technology coupled with advances in knowledge about plant physiology have made it feasible to use real-time substrate volumetric water content sensors to accurately determine irrigation timing and application rates in soilless substrates in greenhouse and container production environments. Sensor-based irrigation uses up-front investments in equipment and system calibration in return for subsequent reductions in irrigation water use and associated costs of energy and labor, spending on fertilizer, and disease losses. It can also accelerate production time. We present formulas for assessing profitability when benefits and costs are separated in time and apply those formulas using data from an experiment on production of gardenia [Gardenia augusta 'MADGA 1' (Heaven ScentTM)]. Sensor-controlled irrigation cuts production time and crop losses by more than half. Annualized profit under the wireless sensor system was over 1.5 more than under the nursery's standard practice, with the bulk of the increase in profit due to the reduction in production time. These results indicate that controlling irrigation using wireless sensor systems is likely to increase profitability substantially, even if efficiency gains are not as high as those achieved under experimental conditions.
Cet article introduit les approches pour un controle automatique des alimentations en eau et en elements nutritifs pour les cultures sous serre. Le concept traditionnel d'irrigation et de fertilisation excedentaires entre en conflit avec les aspects environnementaux. Cependant, les demandes d'eau et d'elements nutritifs des plantes doivent etre satisfaits par les apports. La strategie utilisee generalement est basee sur l'emploi de solutions nutritives standard et de frequentes analyses de la concentration de la solution nutritive dans l'environnement des racines. Une amelioration de cette strategie est esperee en utilisant un systeme de retroaction, qui prend en compte des mesures sensibles de la concentration ionique de l'eau de drainage, ou un systeme de reaction anticipee dans lequel les besoins en eau en elements nutritifs sont prevus a parti de modeles de croissance et de transpiration. Ces approches sont pour la plupart d'entre elles, developpees sur un plant theorique et sont encore loin des applications pratiques. Les strategies actuelles sont dirigees vers la synchronisation des prelevements et des apports, mais les strategies futures devront controler le fonctionnement des plantes.
Major horticultural crops in Florida are vegetables, small fruit, melons, and tree fruit crops. Approximately half of the agricultural area and nearly all of the horticultural crop land is irrigated. Irrigation systems include low-volume micro-irrigation, sprinkler systems, and subsurface irrigation. The present review was divided into two papers, in which the first part focuses on vegetable crop irrigation and the second part focuses on fruit tree crop irrigation. This first part also provides an overview of irrigation methods used in Florida. Factors affecting irrigation efficiency and uniformity such as design and maintenance are discussed. A wide range of soil moisture sensors (e.g., tensiometers, granular matrix, and capacitance) are currently being used in the state for soil moisture monitoring. Current examples of scheduling tools and automated control systems being used on selected crops in Florida are provided. Research data on the effect of irrigation scheduling and fertigation on nutrient movement, particularly nitrate, are reviewed. Concluding this review is a discussion of potential for adoption of irrigation scheduling and control systems for vegetable crops by Florida growers and future research priorities.
All media are composed of three phases: solid, aqueous, and gaseous. This chapter discusses the physical characteristics of these three phases separately and in combination. The physical properties of soilless media comprise bulk density, particle size distribution, porosity, and pore distribution. Following this, the study describeswater content and water potential in soilless media as another physical characteristic. Water content or wetness of a porous medium is the volume or mass of water occupying space within the pores. Water potential is the potential energy of water per unit volume relative to pure water in reference conditions. Water potential quantifies the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure, or matrix effects such as surface tension. Subsequently, the study explains water movement in soilless media. Water is transported through the growing medium into the roots and plant xylem towards the plant canopy where it eventually transpires into the atmosphere. The continuous uptake of water is essential for the growth and survival of plants. Finally, it provides an understanding of solute transport and gas transport in soilless media. The movement and fate of solutes in soil are affected by a large number of physical, chemical, and microbiological processes, and the understanding of gas transport in growing media is important for the evaluation of soil aeration or movement of oxygen from the atmosphere to the medium.
Water scarcity is likely to increase in the coming years, making improvements in irrigation efficiency increasingly important. An emerging technology that promises to increase irrigation efficiency substantially is a wireless irrigation sensor network that uploads sensor data into irrigation management software, creating an integrated system that allows real-time monitoring and control of moisture status that has been shown in experimental settings to reduce irrigation costs, lower plant loss rates, shorten production times, decrease pesticide application, and increase yield, quality, and profit. We use an original survey to investigate likely initial acceptance, ceiling adoption rates, and profitability of this new sensor network technology in the nursery and greenhouse industry. We find that adoption rates for a base system and demand for expansion components are decreasing in price, as expected. The price elasticity of the probability of adoption suggests that sensor networks are likely to diffuse at a rate somewhat greater than that of drip irrigation. Adoption rates for a base system and demand for expansion components are increasing in specialization in ornamental production: Growers earning greater shares of revenue from greenhouse and nursery operations are willing to pay more for a base system and are willing to purchase larger numbers of expansion components at any given price. We estimate that growers who are willing to purchase a sensor network expect investment in this technology to generate significant profit, consistent with findings from experimental studies. This article is protected by copyright. All rights reserved.