Measurement and estimation of transpiration of a soilless rose crop and application to irrigation management
Summary (2 min read)
1. Introduction
- During recent years, a number of authors are paying attention to the improvement of irrigation of protected crops.
- 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.
- 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
- 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.
- 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 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.
- Leaf area index has been estimated weekly.
Results and discussion
- 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 -2 , could be associated to stomatal conductance variations in response to VPD changes, depending on fog system capacity.
Transpiration Model
- 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.
- Transpiration values follow in real time the evolution of VPD, which oscillates depending on air forced heating equipment on and offs .
- A small anticipation of some minutes is obtained for the model in relation to the measured crop transpiration.
- 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.
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Citations
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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....
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...[19], although a lower number of observations were used....
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...[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....
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...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]....
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...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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10 citations
Cites background from "Measurement and estimation of trans..."
...As far as water uptake is concerned, it has been mainly related to radiation, to VPD and to leaf area (Baille et al., 1994; Medrano, 1999; Suay et al., 2003), but also to air temperature (Medrano, 1999) and to nutrient solution temperature (Chapter 4....
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...In different studies (Baille et al., 1994; Medrano, 1999; Suay et al., 2003), water uptake models have been based in Penman-Monteith equation (Monteith and Unsworth, 2007) and have been related to radiation, to VPD and to leaf area....
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7 citations
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References
4,087 citations
296 citations
"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)....
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...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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175 citations
"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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103 citations
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Frequently Asked Questions (9)
Q2. How is the water supply kept at a minimum?
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.
Q3. How many shoots are needed to estimate the leaf area of a plant?
It has also been found that only 11 shoots are needed to estimate the leaf area ofthe flowering shoots, with an error less than 5 %, but usually some more have been used.
Q4. How long has the model been used to estimate the transpiration of a crop?
In order to implement a real-time irrigation management, short time (15 seconds)estimations of crop transpiration have been used.
Q5. How many litres of water was supplied on a sunny day?
For instance, on a sunny day, the quantity of supplied water has been about 1000 litres versus 2280 lsupplied by means of the time scheduling policy.
Q6. What is the method of irrigation for a rose?
All plants are grown following the local standard commercial technics, using the stem bending technique and all-year-round production.
Q7. What is the advective term for the flowering shoots?
VPDLAIGeE LAIk ∗∗Β+∗−∗Α= ∗−1the 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.
Q8. What is the way to control the transpiration of a tomato plant?
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.
Q9. What is the correlation between the radiation extinction coefficient and the temperature?
Results and discussionTranspiration 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 -2 , a positive correlation is observed, with lower scattering than in the range of 400 to 600 wm -2 .