Document Type : Research Paper
Authors
Department of Water Engineering and Management, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran
Abstract
Keywords
Main Subjects
Due to strategic location in the vicinity of the sea, Iran has a unique capacity to benefit from this great potential for development in different fields. The importance and necessity of utilizing the potential capacities of coastal areas has led to the marine-base development being considered at the highest levels of policy-making and planning, which can be reflected in this country's general policies and documents.
The shortage of freshwater resources in the country, in recent years, the attitudes of administrators and decision-makers have been directed towards developing agriculture on the coasts using seawater. In the field of agricultural development in coastal areas, various ideas have been developed in the world so far, one of the successful examples of which is the coastal greenhouse system. This system, by simulating the hydrological cycle and using the seawater desalination approach, enables the simultaneous production of crops and fresh water. In this regard, in the present study, by simulating the functional principles of the coastal greenhouse system, a physical modeling of a similar cultivation media was attempted with smart devices and equipment.
The main aim of this study is to evaluate the effect of high air relative humidity (more than 80%) on the crop water requirement and crop yield of Basil in greenhouses cultivation media and compare it with the corresponding values in controlled cultivation media with normal relative humidity, such as conventional greenhouse conditions.
The present study was conducted at the research greenhouse complex of the Faculty of Agriculture, Tarbiat Modares University. In this study, the cultivation conditions of the crop similar to the coastal greenhouse system were provided by increasing the air relative humidity to near saturation level using a vaporizer. This greenhouse was equipped with sensors to measure and control the air temperature and relative humidity parameters inside and outside the cultivation media connected to central data-logger devices and other precise measurement equipment. Measurement and recording of atmospheric data including air temperature and relative humidity were carried out continuously and regularly simultaneously in three separate environments including the coastal greenhouse cultivation media, the conventional greenhouse cultivation media, and the open field.
In the present study, the increasing and controlling of the air relative humidity in the coastal greenhouse physical model cultivation media was carried out using an ultrasonic vaporizer. One of the innovations of this research in simulating the atmospheric conditions of the coastal greenhouse cultivation media was the use of an ultrasonic vaporizer, because using of thermal vaporizer equipment to increase water vapor in the air also will affected the air temperature in the coastal greenhouse cultivation media. Since the main aim of this study was to investigate changes in crop water requirement and crop yield in a cultivation media with relative humidity close to saturation (above 80%), this ultrasonic vaporizer device made this aim possible without affecting the air temperature.
Basil is a moisture-loving plant and grows better with high relative humidity. The favorable adaptation of this plant to the climatic conditions of controlled environments is one of the reasons for choosing basil for the present study. This study period included a cultivation period from 27th October to 29th November 2025. The crop water requirement and the amount of water required for each pot were determined using the microlysimeter method, and the volume of irrigation water (the amount of soil moisture deficit to the field capacity limit) was measured and delivered to each one.
Also, to evaluate the crop yield of basil at the end of the cultivation period, some of the crop characteristics including plant height, dry weight, and fresh weight of the plant were measured and calculated in the conventional greenhouse and coastal greenhouse cultivation media.
According to the methodology of the study, crop cultivation was conducted in two controlled environments, including a conventional greenhouse and a coastal greenhouse cultivation media. The main principles of the coastal greenhouse system were to increase and control the air relative humidity in the crop cultivation media close to the saturation limit (above 80%) and compare it with the corresponding values in the conventional greenhouse cultivation media. Based on the recorded atmospheric parameters and the analysis of variance, the air temperature values in the two cultivation medias were approximately close to each other and no significant difference was observed between the values. While the average air relative humidity in the coastal greenhouse cultivation media was 84 percent, which was about 1.5 times the average air relative humidity in the conventional greenhouse cultivation media (56 percent), and the difference between the daily relative humidity values in these two cultivation medias was significant at the one percent level.
Based on the results, the crop yield by wet weight in the conventional and coastal greenhouse cultivation medias was measured as 15.98 and 15.83 and by dry weight was measured as 1.62 and 1.53 grams, respectively.
The measurement of daily crop water requirement of Basil using the microlysimeter method during the study period of this research. The average daily crop water requirement of Basil during the crop cultivation period was 1.33 mm in the coastal greenhouse cultivation media and 2.58 mm in the conventional greenhouse cultivation media. The highest and lowest daily crop water requirement of Basil during the crop cultivation period were 1.40 and 1.28 mm in the coastal greenhouse cultivation media and 2.80 and 2.32 mm in the conventional greenhouse cultivation media, respectively. In addition, the total crop water requirement of Basil during the crop cultivation period was 45.20 mm in the coastal greenhouse cultivation media and 87.66 mm in the conventional greenhouse cultivation media.
Based on the results, in the present study, by increasing and controlling the air relative humidity in the crop cultivation media (average 84%), the average daily crop water requirement of Basil decreased compared to the conventional greenhouse cultivation media.
In field of crop yield, no significant difference was observed in the cultivation media in terms of plant fresh and dry weight index, and changes in crop water requirements did not lead to significant differences in crop yield. It was concluded that the average daily crop water requirement of Basil during the crop cultivation period in the coastal greenhouse cultivation media decreased by about 48.5% compared to the conventional greenhouse cultivation media. In other words, it can be said that increasing the air relative humidity in the crop cultivation media by 1.5 times resulted in reducing the crop water requirement of Basil in the coastal greenhouse cultivation media to half the value of this parameter in the conventional greenhouse cultivation media. Accordingly, the efficiency of this system in reducing the crop water requirement was evaluated as very significant.
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
All authors contributed equally to the conceptualization of the article and writing of the original and subsequent drafts.
This declaration does not apply to the use of basic tools for checking grammar, spelling, references, etc. If there is nothing to disclose, there is no need to add a statement.
All data of this study are available upon request from the authors.
The authors would like to thank all participants in the present study.
The authors thank all participants in this study.
The authors would like to thank anonymous referees for their constructive comments.
The authors would like to thank anonymous reviewers for their valuable suggestions in manuscript revision.
The authors avoided data fabrication, falsification, and plagiarism, and any form of misconduct.
The authors declare no conflict of interest.
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