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Modelling transpiration and growth in salinity-stressed tomato under different climatic conditions
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
Gilat Research Centre, Israel.
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
2006 (English)In: Ecological Modelling, ISSN 0304-3800, E-ISSN 1872-7026, Vol. 190, no 1-2, 15-40 p.Article in journal (Refereed) Published
Abstract [en]

Models aiming to simulate growth under salinity stress and varied climatic conditions must rely on accurate methods for predicting transpiration and photosynthesis. Traditionally, models have described salinity stress as a decrease in water uptake caused by a low osmotic potential in the soil; however, many physiological studies suggest that reduced plant growth observed under saline conditions could be caused by increased respiration. Explicit calculation of photosynthesis and respiration enables both approaches to be tested and compared in a simulation model. We used an integrated ecosystems model (the CoupModel) to simulate photosynthesis and transpiration over a range of salinities. The model was calibrated and tested on two sets of data (two different seasons) on saline water, drip-irrigated tomato from lysimeter trials in the Arava Valley, Israel. Yields for the spring season were significantly lower than during the first autumn season even though transpiration was higher. As a result, water use efficiency differed by a factor of two between seasons. The model was successful in capturing this large variation, which was caused primarily by high levels of radiation and vapour pressure deficits during spring. For autumn the salinity stress approach in which water uptake was reduced performed well, whereas during spring the increased respiration approach correlated better with measurements. The concept of water use efficiency was found to be a useful tool for interpreting the accumulated effects of climatic and environmental conditions on particular agricultural systems. An attempt to simulate tomatoes grown in production beds indicated that the model set-up was also able to describe conventional cropping systems

Place, publisher, year, edition, pages
2006. Vol. 190, no 1-2, 15-40 p.
Keyword [en]
drip-irrigation, WUE, photosynthesis modelling, ion toxicity, osmotic effect
National Category
Ecology
Identifiers
URN: urn:nbn:se:kth:diva-5133DOI: 10.1016/j.ecolmodel.2005.04.015ISI: 000233859500002Scopus ID: 2-s2.0-27844524536OAI: oai:DiVA.org:kth-5133DiVA: diva2:7919
Note
Uppdaterad från "Accepted" till published: 20101101. QC 20101101Available from: 2005-05-18 Created: 2005-05-18 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Irrigation with saline water using low-cost drip-irrigation systems in sub-Saharan Africa
Open this publication in new window or tab >>Irrigation with saline water using low-cost drip-irrigation systems in sub-Saharan Africa
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

In the scope of future population support, agricultural productivity, in particular in sub-Saharan Africa, has to increase drastically to meet the UN’s millennium development goals of eradicating extreme poverty and hunger by 2015. Water availability in the root-zone limits crop production in large parts of the developing world. As competition for fresh water increases, water of lower quality, for example saline or polluted water, is often used for irrigation. Low-cost drip systems are suitable for saline water irrigation because they effectuate a minimisation of salt accumulation, leaf burn and peaks in salt concentration. Nonetheless, all types of saline water irrigation contain the risk for causing soil salinisation. Thus, in order to achieve long-term sustainability of these systems, appropriate management strategies are needed. The choice of management practices may be influenced by local conditions such as climate, soil and irrigation water salinity. A litera-ture review showed that there is a potential for saline water irrigation in sub-Saharan Africa in water scarce areas. Low-cost drip irrigation with saline water (6 dS m-1) was successfully used to irrigate two consecutive crops of tomato in semi-arid South Africa. An integrated ecosystems model was developed to simulate long-term yield and salt accumulation in a drip-irrigated agricultural system for a range of salinities, climates and management techniques. Crop, salt and water balance data from two field experiments conducted in Israel and South Africa, respectively, were used to parameterise and test the model. Emphasis was placed on testing the usability of the model as a tool for evaluating the importance of certain plausible management options of low-cost, drip-irrigation systems. Therefore, particular focus was directed towards correctly describing soil salinity stress on plant growth and soil evaporation from a distributed (wetted and dry) surface. In addition, the model was developed to function for different climates without having to change any other parameters or variables except for the actual climatic data. Simulations were subsequently run over a 30-year period to study long-term yield and salt accumulation in the soil profile for two sites in South Africa, demonstrating the applicability of the model. Model simulations showed that high soil salinities reduced crop growth and thus increased both drainage and soil evaporation. Further, covering the soil with a plastic sheet led to a reduction of soil evaporation and a subsequent increase in both transpiration and drainage. Rainfall was crucial for the leaching of salts from the soil, and thus in regions with low levels of rainfall, a higher leaching fraction of supplied saline irrigation water has to compensate for the lack of rain. However, a high leaching fraction also causes large amounts of salt leaching, which could potentially pollute underlying groundwater and downstream ecosystems. This risk can be mitigated using mulching, which minimises non-productive water losses, thereby lowering irrigation water needs. The choice of irrigation water salinity, frequency of irrigation and soil coverage may differ between the farmer and the regional water manager due to different preferences. Furthermore, the study highlighted how environmental variables such as water use efficiency and radiation use efficiency can be used as indicators of system performance. Whereas the latter is first and foremost a general stress indicator, water use efficiency more precisely describes specific factors such as plant size, allocation patterns and evaporative demand, which will affect the exchange of carbon dioxide and water through the stomata.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. x, 26 p.
Series
Trita-LWR. PHD, ISSN 1650-8602 ; 1020
Keyword
Ecology, Water use efficiency; Radiation use efficiency, Management techniques, Modelling, Tomato, Ekologi
National Category
Ecology
Identifiers
urn:nbn:se:kth:diva-209 (URN)91-7178-063-7 (ISBN)
Public defence
2005-05-27, D3, Lindstedtsvägen 5, KTH, 10:00
Opponent
Supervisors
Note
QC 20101102Available from: 2005-05-18 Created: 2005-05-18 Last updated: 2010-11-02Bibliographically approved

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