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Journal ArticleDOI

Measurement and estimation of transpiration of a soilless rose crop and application to irrigation management

01 Sep 2003-Iss: 614, pp 625-630

About: The article was published on 2003-09-01 and is currently open access. It has received 13 citation(s) till now. The article focuses on the topic(s): Deficit irrigation & Irrigation management.

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This paper must be cited as:
[Suay, R., Martínez, P.F., Roca, D., Martinez, M., Herrero, J.M., Ramos, C. (2003). Measurement
and estimation of transpiration of a soilless rose crop and application to irrigation management.
Proceedings of the Sixth International Symposium on Protected Cultivation in Mild Winter Climate:
Product and Process Innovation, Vols 1 and 2, (614), 625-630.]
The final publication is available at
Copyright [ISHS]

R. Suay
, P.F. Martínez
, D. Roca
, J.M. Herrero
, C. Ramos
Instituto Valenciano de Investigaciones Agrarias (IVIA). Apdo. Oficial. 46113 Moncada,
Valencia, Spain. (rsuay, pfmarti, droca)
Dept. Ingeniería de Sistemas y Automática. Universidad Politécnica de Valencia. Apdo.
de Correos 22012 Valencia, Spain. (juaherdu,
Additional index words: hydroponic culture, modelling, leaf area index, closed system.
Drained nutrient solution of soilless culture crops in many countries, is
rejected to waste, producing undesirable polluting effects and reducing the water
and fertilizer use effciency of the cropping system.
Current irrigation practices in protected soilless culture, are based either on
fixed interval scheduling, corrected by means of EC monitoring in drainage or
substrate extract, or on crop transpiration estimations by means of solar radiation
Closed soilless culture systems help to improve water and fertilizer use
efficiency, but irrigation management needs to be optimized, and properly operated
in relation to crop requirements, and needed proportions of air and water in the
A study has been carried out, where the transpiration of a heated rose crop,
conducted by the shoot bending system, is continuously measured by means of an
electronic balance, and estimations are calculated with a simplified Penman-
Monteith equation, adjusted by weekly LAI estimations, as well as outside solar
radiation and inside water vapour saturation deficit recordings.
Based on these transpiration estimations, an irrigation strategy has been
tested and compared to current irrigation practices used in commercial holdings.
1. Introduction
During recent years, a number of authors are paying attention to the improvement
of irrigation of protected crops. The control equipment for irrigation has improved
considerably, but growers of the mediterranean regions are mostly managing irrigation on
the basis of empirical criteria and rules. Fixed volumes of water supply at regular time
intervals, or a partial use of solar radiation integration, is the most common way of
automatic irrigation. Microclimate in mild winter greenhouses can be a strong source of
water stress for crops and the risk is increased by the fact that soilless culture has very
much increased, and substrate physical properties of low water retention force the grower
to look for a reliable automatic system based on optimum decision criteria. Otherwise
either the crop can be under water stress danger or the system can be working on the basis
of extra expenses of water and fertilisers.
More or less complex models of transpiration based on the Penman-Monteith
equation (Monteith, 1973) have been proposed and validated under different conditions
(Bailey et al., 1993; Gonzalez, 1995; Lorenzo et al., 1998; Medrano et al., 2001). A

simplified version (Stanghellini, 1987; Boulard and Jemaa, 1993; Baille et al., 1994a;
Medrano, 1999) that takes into account both, solar radiation and air saturation deficit as
variables could be very useful for the implementation of irrigation algorithms in a soilless
culture system.
The present paper aims at adjusting and validating a simple model of crop
transpiration for a rose soilless crop. A model-based algorithm has been integrated in a
control system, and has been tested for the complete management of crop irrigation needs,
in order to check the real possibilities and degree of reliability for practical applications
2. Materials and methods
A soilless rose crop (cv. Dallas) is grown in an acrylic covered greenhouse of 250
. Heating is supplied for a minimum of 16 ºC, by means of air forced aerotherms, and
humidity is kept at 50 % minimum with a high pressure fog system. Two 30 plants units,
located at the central position of the greenhouse, are grown in a NFT type system, where
transpiration is measured at short time intervals (15 seconds), by means of an electronic
balance (resolution ± 0.1 g). Nine hundred plants grown in a perlite hydroponic system
complete the rest of the greenhouse. All plants are grown following the local standard
commercial technics, using the stem bending technique and all-year-round production.
Short time soilless rose crop transpiration has been recorded and compared with a
simplified transpiration model during a winter cropping period from November to
February. A simplified transpiration model based on the simplified Penman-Monteith
equation has been derived:
E = crop transpiration rate (g m
G = outside solar radiation, w m
VPD = inside air vapour pressure deficit, kPa
k = radiation extinction coefficient, 0.64
A,B = equation parameters (A dimensionless, B g m
This simplified model considers that the transpiration is mainly explained by two
components or terms: a radiative part (directly related to the radiation G absorbed by the
crop) and an advective part (directly related to the inside greenhouse vapour pressure
deficit). The advective term has shown to be really important, especially in winter nights
when heating is working on with no radiation or in cloudy days.
In order to implement a real-time irrigation management, short time (15 seconds)
estimations of crop transpiration have been used. A and B coefficients have been
calculated by statistical identification (multi-parameter lineal regression or multiple
regression model) for transpiration versus radiation and vapour pressure deficit real-time
records. Taking into account that commercial greenhouses may have an outside weather
station and an inside psychrometer, the models obtained by both, outside and inside solar
radiation have been compared, finding that there is no difference in the fitting of their
prediction (R
= 0.92 for both). Thus, the model with the outside solar radiation has been
adopted. Leaf area index has been estimated weekly. Leaf area is composed by two terms,
the arched shoots part, considered as constant for the term of a month, and the flowering
shoots part. The arched shoots part has been measured monthly (4 plants samplings) and

the flowering shoots part has been estimated on a weekly basis, as a linear function of the
length of the shoots, entered as input to the transpiration model. In the period considered,
LAI has varied between 2.12 and 2.51 and the flowering shoots part has represented from
22 % to 27 % of the total LAI. The following relation for the leaf area of the flowering
shoots has been obtained:
LA shoots (cm
)= 22.272 * L (cm) – 468.548 (R
= 0.85, n=67),
L= flowering shoots length
It has also been found that only 11 shoots are needed to estimate the leaf area of
the flowering shoots, with an error less than 5 %, but usually some more have been used.
The radiation extinction coefficient (k) has been considered constant throughout
the period and equal to 0.64 (Stanghellini, 1987).
Results and discussion
Transpiration Flux in Relation to the Microclimate
When transpiration (E) is considered in relation to values of outside solar radiation
(figure 1) between 100 and 400 wm
, a positive correlation is observed, with lower
scattering than in the range of 400 to 600 wm
. Estimation of E when solar radiation is
very low or cero is improved if the saturation deficit of air is considered, particularly
when required time intervals are short (Jolliet and Bailey, 1992; González, 1995). The
scattered values of transpiration for radiation values higher than 400 wm
, could be
associated to stomatal conductance variations in response to VPD changes, depending on
fog system capacity.
Transpiration Model
The fitting of estimated and measured values of transpiration is shown in (figure
2) and is quite good all along the measured transpiration flux, which range is fairly wide,
between 20 and 230 g/m
.h (5 and 58 g/plt.h). Some degree of underestimation is
observed for the higher transpiration values, and an overestimation for the lower values,
though very acceptably fitted in the measured range. Similar or bigger deviations are
reported by Baille et al. (1994b) for a number of pot plants.
A very good prediction is obtained in the 24 h cycle when the course of the
measured crop transpiration values is compared to the estimated one for Autumn and
Winter (figure 3). The observed deviations betweeen the two sets of values, correspond to
model underestimations in the hours when the flux is maximum. Also an overestimation
is shown along the morning hours and, again, underestimation towards the sunset.
In general terms the prediction is considered good. The model works on a real
time basis, and performs with a high level of accuracy the reactions of the transpiration
flux to the climatic variations, solar radiation and VPD, during the day and the night. In
the night hours, when forced air heating equipment is not working during longer intervals,
due to milder temperatures, and measured crop transpiration flux is showing wider
oscillations, the model has been able to perform this evolution. These conditions can be
distinguished from the ones when aerotherms have been working more continuously, due
to lower temperature levels (figure 4). Also during the night there is a very good
behaviour of the estimated transpiration in relation to the course of VPD. Transpiration
values follow in real time the evolution of VPD, which oscillates depending on air forced
heating equipment on and offs (figure 4). A small anticipation of some minutes is
obtained for the model in relation to the measured crop transpiration. For instance, on a
sunny day, the quantity of supplied water has been about 1000 litres versus 2280 l

supplied by means of the time scheduling policy. This difference is much more important
when a cloudy day is considered, with only 520 l watering with the algorithm control.
Predictive Control of Water Supply
When the algorithm based on the studied transpiration model, has been
implemented and tested for the irrigation scheduling of the rose soilless crop on perlite, a
good performance has been obtained in the different conditions along Autumn and
Winter. Two different insolation days are shown (figure 5). Watering is supplied at
variable intervals, when the estimated transpiration integral reaches the set value. During
the night the crop transpiration rate and integral are estimated by the model, and the
required waterings are supplied to the crop. Measured crop transpiration all along the
night hours is significant, particularly due to force air heating, ranging from 24% in a
clear day to some 46% for an overcast day. Jolliet and Bailey (1992) report on some 22%
the night transpiration fraction of the 24 hours period, for young tomato plants, under
heated greenhouse, and Medrano (1999) obtained 10 to 20% for cucumber in Spain, in a
cold greenhouse in Autumn. Figure 5 shows a good fitting of the model in the short time
intervals, for two very different solar radiation days in Winter.
Water supply can be very well adapted, in this way, to actual plant requirements
all the time. Estimations made by the model have been very acceptable, at the practical
level, for irrigation control, in soilless growing systems that have a high level of fragility
due to the very low buffer capacity for water and minerals.
This work has been partially supported by projects 1FD97.0974.C0201 and
SC00.093 of the Ministry of Science and Technology and INIA. Contributions of J.Cerdá,
C.Arnal, A.Tomás, B.Hueso and A.Gallego are recognised.
Bailey, B. Montero J.I. Biel C. Wilkinson D.J. Anton A. Jolliet O. 1993. Transpiration of
Ficus Benjamina. Comparison of measurements with predictions of the Penman-
Monteith model and a simplified version. Ag. For. Met. 65: 229-243
Baille M. Baille A. Delmon D. 1994a. Microclimate and transpiration of greenhouse rose
crops. Agric. For. Meteo. 71: 83-97
Baille M. Baille A. Laury J.C. 1994b. A simplified model for predicting evapo-
transpiration rate of nine ornamental species vs. climate factors and leaf area. Sci.
Hort. 59:217-232.
Boulard T., Jemaa R. 1993. Greenhouse tomato crop transpiration model application to
irrigation control. Acta Hort. 335: 381-387.
González M.M. 1995. Estudio y modelización de intercambios gaseosos en cultivo de
rosas bajo invernadero. Tesis doctoral, Univ. Pol. Valencia, Spain, 192 pp.
Jolliet O., Bailey B.J. 1992. The effect of climate on tomato transpiration in greenhouse:
measurements and models comparison. Agr. For. Met., 58:43-63.
Lorenzo P., Medrano E., Sanchez M.C., 1998. Greenhouse crop transpiration. An
implement to soilless irrigation management. Acta Hort. 458: 113-119.
Medrano E. 1999. Gestión del riego en cultivo de pepino en sustrato: Evaluación de la
transpiración durante la ontogenia. Tesis Doc. Univ. Polit. Madrid. 216 pp.
Medrano E., Lorenzo P., Sanchez M.C. 2001. Evaluation of a greenhouse crop
transpiration model with cucumber under high radiation conditions. Acta Hort. 559:

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TL;DR: A statistical model based on the “multiple stepwise regression” technique and based on 26 stems collected at different developmental stages explained 95% of the LA variance and can save time, effort, and resources in determining cut rose stem LA, enhancing its application in research and production contexts.
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Cites background or methods from "Measurement and estimation of trans..."

  • ...[19], the estimation of stem LA in cut roses of the cv....


  • ...[19], although a lower number of observations were used....


  • ...[19] study, the model developed in our study considered successive measurements of the LA of all erect stems of one plant through its crop cycle, enabling accommodation of a range of different development stages, which increases its potential applicability....


  • ...The limitations also extend to the architecture of the plant, with some models being developed using material exclusively from erect stems, disregarding samples resulting from the bending of weak stems of the plant [1,19]....


  • ...Several models are currently available for rose crop to determine the area of individual leaves [1,17,18], leaflets [5], and stems [19] using allometric measures such as the length and width of leaves or leaflets, the number of leaflets, or the height of the stem....


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Journal ArticleDOI
01 Mar 1974-Physics Today
Abstract: PREFACE TO THE SECOND EDITION LIST OF SYMBOLS 1. SCOPE OF ENVIRONMENTAL PHYSICS 2. GAS LAWS Pressure, volume and temperature Specific heats Lapse rate Water and water vapour Other gases 3. TRANSPORT LAWS General transfer equation Molecular transfer processes Diffusion coefficients Radiation laws 4. RADIATION ENVIRONMENT Solar radiation Terrestrial radiation Net radiation 5. MICROCLIMATOLOGY OF RADIATION (i) Interception Direct solar radiation Diffuse radiation Radiation in crop canopies 6. MICROCLIMATOLOGY OF RADIATION (ii) Absorption and reflection Radiative properties of natural materials Net radiation 7. MOMENTUM TRANSFER Boundary layers Wind profiles and drag on uniform surfaces Lodging and windthrow 8. HEAT TRANSFER Convection Non-dimensional groups Measurements of convection Conduction Insulation of animals 9. MASS TRANSFER (i) Gases and water vapour Non-dimensional groups Measurement of mass transfer Ventilation Mass transfer through pores Coats and clothing 10.MASS TRANSFER (ii) Particles Steady motion 11.STEADY STATE HEAT BALANCE (i) Water surfaces and vegetation Heat balance equation Heat balance of thermometers Heat balance of surfaces Developments from the Penman Equation 12.STEADY STATE HEAT BALANCE (ii) Animals Heat balance components The thermo-neutral diagram Specification of the environment Case studies 13.TRANSIENT HEAT BALANCE Time constant General cases Heat flow in soil 14.CROP MICROMETEOROLOGY (i) Profiles and fluxes Profiles Profile equations and stability Measurement of flux above the canopy 15.CROP MICROMETEOROLOGY (ii) Interpretation of measurements Resistance analogues Case studies: Water vapour and transpiration Carbon dioxide and growth Sulphur dioxide and pollutant fluxes to crops Transport within canopies APPENDIX BIBLIOGRAPHY REFERENCES INDEX

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01 Jan 1987-
Abstract: In this book some physical aspects of greenhouse climate are analyzed to show the direct interrelation between microclimate and crop transpiration. The energy balance of a greenhouse crop is shown to provide a sound physical framework to quantify the impact of microclimate on transpiration and to identify the constraints set on climate management by the termodynamic behaviour of the canopy. Before the relationship among microclimate, canopy temperature and transpiration is rendered in mathematical terms, a good deal of experimental work is necessary to establish sub-models for the heat transfer of the foliage, for the radiative transfer within the canopy and for the canopy resistance to vapour transfer. The sub-models are merged in a combination-type equation to obtain the temperature of a greenhouse crop and its transpiration. The resulting estimates are shown to reproduce accurately the temperature and transpiration of a greenhouse tomato crop, as measured at time intervals of a few minutes. To illustrate the practical application of the model thus developed a number of examples are presented. In particular, it is shown that defining the transpiration rate as the criterion for the control of air humidity within a greenhouse would deliver a quantitative framework for that control. That would largely enhance the efficiency of the (expensive) procedures applied at present for the control of humidity in greenhouses.

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"Measurement and estimation of trans..." refers background in this paper

  • ...The radiation extinction coefficient (k) has been considered constant throughout the period and equal to 0.64 (Stanghellini, 1987)....


  • ...A simplified version (Stanghellini, 1987; Boulard and Jemaa, 1993; Baille et al., 1994a; Medrano, 1999) that takes into account both, solar radiation and air saturation deficit as variables could be very useful for the implementation of irrigation algorithms in a soilless culture system....


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Abstract: Recent studies have shown that, for greenhouse tomato crops, high levels of humidity and low levels of light depress transpiration and lead to yield losses. These adverse effects could be avoided by properly controlling the greenhouse climate. This work provides the basis for an effective control, by measuring the effect of climate (air speed, vapour pressure deficit, solar radiation and CO 2 ) on tomato transpiration and by assessing five transpiration models. The main results are as follows: transpiration rate increases linearly with solar radiation, air vapour pressure deficit and air speed; air temperature, CO 2 concentration and pipe temperature have no significant influence. For a young crop, an increase in solar radiation of 1 MJ m −2 day −1 resulted in an increase in transpiration of 0.09 mm day −1 ; an increase in vapour pressure deficit of 0.1 kPa (dehumidification of 4% relative humidity at 20°C) increased transpiration by only 0.013 mm day −1 . A forced air movement of 1 m s −1 increased transpiration by 0.13 mm day −1 . For a mature crop solar radiation had a slightly higher effect than for a young crop (an increase of 1 MJ m −2 increased transpiration by 0.14 mm day −1 ), but the vapour pressure deficit effect was much higher (a deficit of +0.1 kPa increased transpiration by 0.24 mm day −1 ) than for the young crop. Transpiration rates were comparable with most of the experimental results obtained by other researchers. However, large differences between the regression lines of some workers remain. This stresses the limitations of the experimental approach and the need for more general models, which once developed do not involve any adjustment of parameters. Five transpiration models have been checked against measurements. Models using constant values for the stomatal conductance had poor accuracy compared with the measurements (Chalabi −51%, Aikman +62%). A simplified Penman model gave good predictions on average (−2%), but with strong individual variations. Stanghellini's and Jolliet's models were the most accurate (+3% and −8% on average, respectively), and predicted both solar radiation and dehumidification effects well because they take into account the effect of vapour pressure deficit on stomatal conductance. In contrast, air temperature and CO 2 influences on stomatal conductance are not significant and do not need to be included in a tomato transpiration model.

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"Measurement and estimation of trans..." refers background in this paper

  • ...Estimation of E when solar radiation is very low or cero is improved if the saturation deficit of air is considered, particularly when required time intervals are short (Jolliet and Bailey, 1992; González, 1995)....


  • ...Jolliet and Bailey (1992) report on some 22% the night transpiration fraction of the 24 hours period, for young tomato plants, under heated greenhouse, and Medrano (1999) obtained 10 to 20% for cucumber in Spain, in a cold greenhouse in Autumn....


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Abstract: Measurements of evapotranspiration rate (E) for nine greenhouse ornamental species (Begonia, Cyclamen, Gardenia, Gloxinia, Hibiscus, Impatients, Pelargonium, Poinsettia and Schefflera) have been carried out concurrently with a survey of indoor climate (eg solar radiation, G, and vapour pressure deficit, D) and leaf area index (L) Correlations linking E to G, D and L are proposed, based on the formalism of the Penman-Monteith equation: E = Af1(L)G + Bf2(L)D Calculated short-term (hourly) evapotranspiration rates agree fairly well with measured rates The information contained in A and B coefficients was analyzed, showing that the species under study have quite different behaviour and sensitivity to G and D, relative to canopy water vapour exchanges From A and B, estimations of the average values for the leaf stomatal resistance, r1, and leaf aerodynamic resistance, ra, were derived and gave, for most of the species, plausible orders of magnitude for these two resistances

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Abstract: Measurements of microclimate and transpiration of two greenhouse crops of roses (grafted and ungrafted) grown in rockwool were carried out during late spring and summer periods of 1989 to 1992 in the South of France. Results show that the crops have relatively low rates of transpiration compared with the latent heat equivalent to the global radiation incident on the crop. Analysis of the results indicates that this can be attributed to several causes: (1) for both crops, (a) stomatal closure as a result of high levels of the saturation deficit when the misting system was not operating (a value of 1.5 kPa was found to be the critical value above which stomatal conductance of the crop falls significantly) and (b) high substrate temperature during the afternoon and poor aeration of the root system may also reduce water uptake by the roots; (2) for the ungrafted crop, the low leaf area index ( L ≈ 1) limits potential transpiration rate and also prevents cooling and humidification of the greenhouse air through a microclimatic ‘feedback effect’. The use of the Penman-Monteith formula, incorporating computed values of the surface resistance to water vapour transfer vs. global radiation and saturation deficit, gives a good prediction of the hourly transpiration rate. The results confirm the importance of adequate control of greenhouse saturation deficit and substrate temperature during summer conditions, especially when radiation load is high and canopy transpiration is not sufficient to cool and humidify the greenhouse environment.

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