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Application of non-thermal plasma technologies in soilless culture
EUVRIN2nd Workshop Fertilization & Irrigation
Bleiswijk, The Netherlands13-14 September 2018
1Daniele Massa, 1Burchi G., 1Cacini S., 1Cannazzaro S., 2Cursi L., 1Di Lonardo S., 2Gambineri F.1CREA Research Centre for Vegetables and Ornamentals, Council for Agricultural Research and Economics, Pescia, Italy
2Laboratori ARCHA srl, Pisa, Italy
Project co-financed from Tuscany POR FESR 2014-2020 Bando 2 – progetti di ricerca e sviluppo delle PMI; HT-HG High Tech –House Garden La coltivazione in serra del futuro: l’high tech al servizio dell’ortoflorovivaismo toscano
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Project HT-HG: High Tech-House Garden
• HT-HG is an Italian Regional project financed by European Community (POR-FESR 2014-20120
Tuscany Region, Italy)
• Main objectives:
• supporting private companies in developing technologies for applications in protected culture
• implementation of high-tech tools and cultivation systems in low-tech Mediterranean greenhouses
• increasing economic and environmental sustainability of the cultivation process trough improved crop
management and reduce input/output of agrochemical products
• Main technologies:
• proximal sensors
• climate monitoring (temperature, humidity, radiation, etc.)
• root zone moisture: FDR sensors
• water drainage (and/or recirculated): ISE sensors (NO3, Cl, Na), pH, EC, redox potential (ORP)
• optical sensors: multispectral cameras (in the range of VIS-NIR)
• non-thermal plasma technologies
• water treatment by bubbling treated air through the irrigation water
• air treatment directly in the greenhouse environment
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NTP devices: working principle
• The NTP causes gas ionization that can be generated in different gas mixture using different technologies:• microwaves
• atmospheric pressure plasma jet (APPJ)
• laser
• corona discharges
• dielectric barrier discharge (DBD)
• The gas is ionized by electric discharges due to the high potential difference between two electrodes (5-25 kV in DBD)
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NTP devices (DBD): working principle
High voltagesource
Air inlet
Air outlet
Reactor
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NTP devices: in the greenhouse
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NTP devices: possible advantages for applications in agriculture & soilless culture
• NTP-treated air is rich in reactive N (RNS) and O (ROS) species and O3 that cause oxidative damage to
organic molecules and then that can be used for disinfection (reduced BOD, microbial contamination)
• pathogen prevention
• maintenance of irrigation systems, lower risk for clogging, etc.
• when bubbled through irrigation water, NTP-treated air adds NO3 by fixation of atmospheric N as HNO3
causing acidification and addition of N
• plant nutrition
• maintenance of irrigation systems, lower risk for dripper clogging, etc.
• the presence of exogenous ROS and NO may have biostimulant activity on plants which acts the
production of secondary metabolites useful for improving plant resistance to pathogens and produce
quality
• increased TSS/°Brix
• increased polyphenols and other secondary metabolites
• shorter cultivation cycle
• …a solution for organic farming?
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NTP devices: possible advantages for applications in agriculture & soilless culture
Small reactor for laboratory tests
Treated air bubbling through water
pH
0 10 20 30 40 50 602.00
2.50
3.00
3.50
4.00
4.50
5.00
5.50
R2 = 0.92
HourspH
Nitrate concentration
0 10 20 30 40 50 60 700
1
2
3
4
R2 = 0.91
Hours
N-N
O3 (
mol m
-3)
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Many examples from the literature…but
The experimental greenhouses
Standard (basic equipment) side as a control High-tech side
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Preliminary experiments: materials and methods
• Basil (Ocimum basilicum L.) cv Tigullio grown in a phytotron
• 22/25 °C night/day, 75-80% RH, 1000 µmol m-2 s-1
• 1.5-L pots peat:perlite 50:50 v/v
• Four replicates and four plants per replicate
• Treatments:
• Control (CTR): plants irrigated with Hoagland’s solution (HS)
• NTP-R: as CTR but HS were NTP-treated just before irrigation (1
h/L treatment with air flux of 2 L/min)
• NTP-RC: as NTP-R plus NTP-treated (deionized) water sprayed on
canopy (50 ml/pt)
• Destructive analysis
• Biomass production and biometric parameters
• Leaf pigments, SPAD index and total phenols
• Organic N and nitrates content in leaves
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Results: plant growth
Shoot fresh weight
CTR NTP-R NTP-RC0
10
20
30
40
50
60
70
(g p
t-1)
Number of nodes
CTR NTP-R NTP-RC0
2
4
6
8
10
b a a
(n p
t-1)
Plant height
CTR NTP-R NTP-RC0
6
12
18
24
30
(cm
pt-1
)
Shoot dry weight (percentage)
CTR NTP-R NTP-RC0
3
6
9
12
15
b ab a
(g 1
00g
-1)
CTR NTP-R
CTR NTP-RC
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Results: tissue analysis (leaf pigments and phenols)
SPAD chlorophyll
CTR NTP-R NTP-RC0
10
20
30
40
50
60
70
SP
AD
index
Total chlorophyll (a+b)
CTR NTP-R NTP-RC0.0
0.6
1.2
1.8
2.4
3.0
(mg g
-1F
W)
Chlorophyll a/b ratio
CTR NTP-R NTP-RC0.0
0.6
1.2
1.8
2.4
3.0
b ab b
Carotenoids
CTR NTP-R NTP-RC0.0
0.1
0.2
0.3
0.4
(mg g
-1F
W)
Chl (a+b)/carotenoids
CTR NTP-R NTP-RC0
5
10
15
20
(mg g
-1F
W)
Total phenols
CTR NTP-R NTP-RC0
2
4
6
8
10
(A3
20 g
-1F
W)
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Results: tissue analysis (nitrogen)
• Conclusions
• NTP treatments had neither no negative effect on plant growth and biomass
accumulation nor phytotoxic effects on basil plants
• NTP treatments induced a significant reduction in the accumulation of nitrate in the
tested leafy vegetable with a parallel decrease in the total N content, which however
remained above the limits of sufficiency for this test species
• Shorter cultivation cycle?
Nitrates (NO3)
CTR NTP-R NTP-RC0
1000
2000
3000
4000
ab
b
(mg k
g-1
FW
)
Organic nitrogen
CTR NTP-R NTP-RC0
20
40
60
80
a ab
N (
g k
g-1
)
Total nitrogen
CTR NTP-R NTP-RC0
20
40
60
80
a ab
N (
g k
g-1
)
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Summing up
• NTP shows some potential benefits to support the
management of closed-loop (soilless) culture
• disinfection
• acidification of nutrient solution/root zone
• addition of nutrients
• biostimulation/produce quality
• Many questions under operational conditions
• dosage/scheduling?
• plant response?
• costs? installation/mantainance?
