The study was conducted to evaluate greenhouse performance under various locations and different orientation.
The absolute differences were lower (-0.03 kg.m²/day /row) in Canada (A) and higher in Holland (D)- 0.06 kg/m²/day/row.
There seems to be a link between the pattern of the difference and orientation of greenhouses. Minor changes were observed in Canada - 2ᵒ orientation and larger fluctuations in Holland: - 110ᵒ and 65ᵒ orientation.
In some cases the pattern of these differences is not identical in the beginning and the late part of the growing season.
The present study does not provide scientific explanation to this phenomenon.
However, this phenomenon may provide an interesting opportunity to improve the yield by managing the trellising strategy. Timing and duration of lowering the trellising should be studied systematically.
Preliminary observations, conducted in 2013 aimed at improving rows performance by lowering the two sides of the rows separately. It is expected that the grower will be able to manage and adjust the trellising strategy according to the daily growth pattern and radiation.
Introduction
Light penetration to a greenhouse is a complex process, in which sun angles, greenhouse location, greenhouse orientation and type of cover, play an important role in the processes.The sun's angle varies throughout the year and the relationship between direct solar radiation and radiation inside greenhouse varies throughout the year.
Differences in photosynthesis were found between two sides of the rows in citrus. It was explained by the difference in photosynthesis efficiency between morning and afternoon, which can be caused by photo inhibition effect or Hysteresis.
Light interception by plants depends mainly on the plant's Leaf Area Index (LAI): At an LAI of 3, an indeterminate crop theoretically intercepts about 90% of the incident light.
The spatial arrangement of plants in the greenhouse is important. It determines the amount of light that reaches the top of the plants and may also affect the quality of light to the lower parts of the plants.
Previous observations in Holland using the “plant growth analysis“ system, showed that growth rate between two side of the rows was different and its intensity was different throughout the year.
The common trellised technology practiced in modern cultivation in greenhouse tomatoes varied from a height of 2.5m to 3.5 m. Differences of trellising height between the two sides of the row indicate that it is possible to improve uniform performance between the rows.
This study will present differences in growth rate between sides of rows in four locations and discuss the practical aspects of improving the yield.
Materials and methods
Fresh weight of an individual stem was weighed continuously along the growing season, using weighing units developed especially for this purpose.Data are transmitted every 20 minutes by radio to the computer and then to the server to process data using software that was developed especially for this purpose. Processed data are transmitted to the grower via the Internet website on the following day. Climate and irrigation data are collected from the grower's climate and irrigation control system. Data are expressed as growth rate in units of fresh weight gr./stem or gr./day/m².
Monitoring and measurements were performed in 4 tomatoes greenhouses in the following locations. Latitude and Greenhouse orientation are specified in table no.1.
Table no 1.
Varieties and plant population were different in the various locations
A.Canada – Variety Torrero 3 stems /m²
B.Holland – Variety Grodena 3 stems /m²
C.Holland – Variety Capricia 3.9 stems/m²
D.Holland – Variety Capricia 3.3. stems/m²
100 weighing units were placed in each location, where 50 units were connected to the east side of the row and 50 to the west side. Data were collected throughout the growing season of 2014. In C. Holland data were collected in 2013 .
Results and discussion
Differences in growth rate were observed between the east and the west side of the rows in the 4 locations (Figure No. 1)However, the pattern, timing and period of this phenomenon varied among the locations, resulting in differences between the locations.
The biggest difference were observed in location D (Holland 65ᵒ ), while the lowest difference was observed in A (Canada 2ᵒ)
The daily differences between the rows were calculated and expressed in kg/day/m² along the year (Figure No. 2)
The pattern of the differences between row sides varied along the year in the four locations. In addition, the absolute differences are different between the locations.
The absolute differences were lower -0.03 kg/m² in Canada (A) and higher in Holland (D)- 0.06 kg/m² . Values in Holland ( B,&C) varied between 0 to 0.3 kg/m².
There seems to be a relationship between the fluctuations phenomenon and the greenhouses orientation. Minor phenomenon changes were observed in Canada (A) 2ᵒ, orientation and larger fluctuations in Holland, mainly in (C) 110ᵒ and (D) 65ᵒ.
The differences in growth between the rows are illustrated by presenting the accumulated values of the differences between the rows throughout the growing period (Figure No. 3).
The pattern of accumulation differs between the various locations.
In Canada (A, 2ᵒ) - it seems that there are differences in the nature of the changes between the beginning of the season and the following stages.
In the Netherlands - with a slight change of orientation compared to the North (B, 15ᵒ), there are also differences between the beginning of the season and it’s following stages.
When the orientation of greenhouses is clearly different from the North (C, 110ᵒ & D 65ᵒ) the accumulation curve shows the same pattern at the beginning of the season and it’s following stages, with a break between the two parts of the season.
Table 2 shows the absolute yield of the rows, as well as the calculation of the differences between the rows.
In addition, a calculation was conducted to present differences between the rows that are greater than + 0.005 kg/m² or less than -0.005 kg/m². This calculation took into account differences in the course of the season, when one line was lower than the other on a certain date and then this row became inferior to the second row.
The above phenomenon is also expressed in Figure No. 4:
There seems to be a large difference between locations, in the range of higher than +0.005 or less than -0.005.
This phenomenon is more pronounced in locations where greenhouse orientation is significantly different than North – South ( compare D&C to A&B).
Discussion
It appears that differences in growth rates between row sides in this study are a consistent pattern of the phenomenon.The differences between east and the west can be explained by differences in photosynthesis efficiency between morning and afternoon. This phenomenon was quoted in several crops.
However, the present study does not provide any scientific explanation to the phenomenon observed in this study: The difference and pattern between the two sides of rows in the beginning of the season and in the late stage of the season is unclear.
It is logical to assume that several factors are involved in this phenomenon, including light intensity, plant development status, plant density, varieties and more. It would be interesting to study the effect of defused light on this issue.
It was clear that greenhouse orientation is linked with this phenomenon, but more research is required to elaborate this subject.
Preliminary observations were conducted for the purpose of improving rows performance by separately lowering the two sides of the rows (Star growers 2013).
This was accompanied by improved light penetration toward the top of the opposite rows and better performance.
Since the accumulated differences between rows varied between 3 to 7 kg/m, it can be estimated that there is an economical potential to minimize the gap between rows by improving light penetration to the shaded row.
This can be done by separately lowering the two rows: Timing and length of lowering should be studied systematically by following on-line the daily growth rate of the two rows .This will enable the grower to manage the process in a controlled manner.
For further information:
Paskal Technologies
Dr Menachem Dinar, Agronomist
Email: [email protected]
or
Elie Adania, Marketing Director
Email: [email protected]
www.paskal-tech.com