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Floods, soil and food – Interactions between water management and rice production within An Giang province, Vietnam
Stockholm University, Faculty of Science, Department of Physical Geography.ORCID iD: 0000-0002-8016-814X
Stockholm University, Faculty of Science, Department of Physical Geography.ORCID iD: 0000-0002-3527-0241
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2021 (English)In: Agriculture, Ecosystems & Environment, ISSN 0167-8809, E-ISSN 1873-2305, Vol. 320, article id 107589Article in journal (Refereed) Published
Abstract [en]

Rapid intensification of Vietnamese rice production has had a positive effect on the nation's food production and economy. However, the sustainability of intensive rice production is increasingly being questioned within Vietnam, particularly in major agricultural provinces such as An Giang. The construction of high dykes within this province, which allow for complete regulation of water onto rice fields, has enabled farmers to grow up to three rice crops per year. However, the profitability of producing three crops is rapidly decreasing as farmers increase their use of chemical fertilizer inputs and pesticides. Increased fertilizer inputs are partly used to replace natural flood-borne, nutrient-rich sediment inputs that have been inhibited by the dykes, but farmers believe that despite this, soil health within the dyke system is degrading. However, the effects of the dykes on soil properties have not been tested. Therefore, a sampling campaign was conducted to assess differences in soil properties caused by the construction of dykes. The results show that, under present fertilization practices, although dykes may inhibit flood-borne sediments, this does not lead to a systematic reduction in nutrients that typically limit rice growth within areas producing three crops per year. Concentrations of total nitrogen, available phosphorous, and both total and available potassium, and pH were higher in the surface layer of soils of three crop areas when compared to two crop areas. This suggests that yield declines may be caused by other factors related to the construction of dykes and the use of chemical inputs, and that care should be taken when attempting to maintain crop yields. Attempting to compensate for yield declines by increasing fertilizer inputs may ultimately have negative effects on yields.

Place, publisher, year, edition, pages
2021. Vol. 320, article id 107589
Keywords [en]
An Giang, Rice, Intensification, Soil properties, Soil nutrients, Water management
National Category
Agricultural Science
Research subject
Physical Geography
Identifiers
URN: urn:nbn:se:su:diva-195512DOI: 10.1016/j.agee.2021.107589ISI: 000691679600003OAI: oai:DiVA.org:su-195512DiVA, id: diva2:1586400
Funder
Swedish Research Council, 2016-06313Available from: 2021-08-19 Created: 2021-08-19 Last updated: 2022-08-20Bibliographically approved
In thesis
1. Sustainable agriculture: From global challenges to local land management
Open this publication in new window or tab >>Sustainable agriculture: From global challenges to local land management
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Despite the success of agriculture management practices in increasing the availability of food needed to meet the requirements of the expanding global population, there are increasing demands placed on the resources on which the sector depends. Opportunities for the development of agricultural systems are constrained by increasing competition, from other sectors, for shared resources. In tackling this constraint, agricultural management solutions are often narrowly focused on problems related to single resources. But this single focus may lead to unintended trade-offs. To make sound management decisions, there is a need to better understand trade-offs which may occur from resource use efficiency solutions implemented in the agricultural sector. With a particular focus on soil and water resources, the aim of this thesis was to investigate trade-offs that occur, when meeting demands placed on agriculture systems, if management solutions are narrowly focused. Broadly, we hypothesize that approaches to land management that take a more holistic view of agricultural systems being part of an ecosystem mosaic should be adopted to ensure sustainability. A global assessment of potential land requirements shows that national level production of sufficiently nutritious food may be constrained by land availability, such that allocation of land to nutritious crop production might come at the cost of lost land for other crops or uses. This constraint will be the most prevalent in African states. In further studies, we focused on the management of water resources, which are becoming particularly limiting for crops that have high water demands, such as rice. Through a meta-analysis of paired plot experiments, which assessed the effect of water saving irrigation in rice production, and soil sampling within An Giang, a major rice producing province of Vietnam, we examined the effect of water management practices on soil properties. The meta-analysis finds that significant reductions in soil organic carbon, and potentially organic matter bound nutrients, have been observed when water efficient practices replace continual flood irrigation. This suggests that, although yield reductions may not be seen in the short term, water saving irrigation may, over time, lead to reductions in soil fertility and yields. Within An Giang province, there are concerns regarding the loss of flood-borne, nutrient rich, sediments in fields where the annual flood waters have been completely regulated. However, we find that this complete regulation does not result in reduced soil nutrient properties when compared to areas where floods are only partially regulated. The effect of different land management practices on soil properties were further explored within the Kilombero Valley, Tanzania. Comparing farming practices along a gradient of intensity, we found contrasting effects of irrigation and fertilization, with irrigation increasing soil organic carbon and fertilization reducing soil organic carbon. Overall, the results of this thesis highlight the importance of looking beyond meeting short term needs, which can have negative long term consequences. The success of land management practices implemented now do not, necessarily, equate to their continued success in the future. As demands placed on agriculture are going to increase, the long term trade-offs which may occur from present practices must be at the forefront of agricultural management.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography, Stockholm University, 2021. p. 38
Series
Dissertations in Physical Geography, ISSN 2003-2358 ; 16
Keywords
agriculture, irrigation, nutrients, soil properties, water management, fertilisation
National Category
Soil Science Agricultural Science Physical Geography
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-195742 (URN)978-91-7911-554-8 (ISBN)978-91-7911-555-5 (ISBN)
Public defence
2021-10-08, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14 and online via Zoom, https://stockholmuniversity.zoom.us/j/66045807129, Stockholm, 14:00 (English)
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Available from: 2021-09-15 Created: 2021-08-25 Last updated: 2022-02-25Bibliographically approved

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Livsey, JohnScaini, AnnaBerg, HåkanManzoni, Stefano

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