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Exploring potentials and constraints of low-cost drip irrigation with saline water in sub-Saharan Africa
KTH, Superseded Departments, Land and Water Resources Engineering.
International Water Management Institute.
2004 (English)In: Physics and Chemistry of the Earth, ISSN 1474-7065, E-ISSN 1873-5193, Vol. 29, no 15-18, 1035-1042 p.Article in journal (Refereed) Published
Abstract [en]

Irrigation with saline water could provide an interesting opportunity to meet increasing food demands without competing with other pressing needs for fresh water such as domestic and industrial water use in water scarce regions. In sub-Saharan Africa, saline groundwater could be a plentiful and under-utilised resource; however, there is a lack of data to confirm this assumption. Saline water is deliberately and successfully used for irrigation of field and garden crops in several countries. The water saving characteristics and the distribution patterns of water in the soil under drip irrigation make this water application technique suitable for use in combination with saline water. Low-cost drip irrigation has already been successfully implemented in sub-Saharan Africa. It is suggested that low-cost drip irrigation with saline groundwater for the cultivation of horticultural crops can be a feasible option under conditions of water shortage, and has the potential to contribute to improved and sustainable crop production for smallholder farmers.

Place, publisher, year, edition, pages
2004. Vol. 29, no 15-18, 1035-1042 p.
Keyword [en]
saline water, drip irrigation, sub-Saharan Africa, South Africa, small-scale farmers, horticultural crops
National Category
Ecology
Identifiers
URN: urn:nbn:se:kth:diva-5131DOI: 10.1016/j.pce.2004.08.004ISI: 000224928800003Scopus ID: 2-s2.0-5144235523OAI: oai:DiVA.org:kth-5131DiVA: diva2:7917
Note
QC 20101101. 4th WaterNet/Warfsa Symposium. Gaborone, BOTSWANA. OCT 15-17, 2003 Available 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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