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Soil Carbon, Nitrogen and Phosphorus Contents along a Gradient of Agricultural Intensity in the Kilombero Valley, Tanzania
Stockholm University, Faculty of Science, Department of Physical Geography.
Stockholm University, Faculty of Science, Department of Physical Geography. University of Dar es Salaam, Tanzania.
Stockholm University, Faculty of Science, Department of Physical Geography. Ohio State University, USA.
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Number of Authors: 82020 (English)In: Land, E-ISSN 2073-445X, Vol. 9, no 4, article id 121Article in journal (Refereed) Published
Abstract [en]

The preservation of soils which provide many important services to society is a pressing global issue. This is particularly the case in countries like Tanzania, which will experience rapid population growth over coming decades. The country is also currently experiencing rapid land-use change and increasing intensification of its agricultural systems to ensure sufficient food production. However, little is known regarding what the long term effects of this land use change will be, especially concerning soil quality. Therefore, we assessed the effect of irrigation and fertilization in agricultural systems, going from low intensity smallholder to high intensity commercial production, on soil organic carbon (SOC), total nitrogen (TN), and total phosphorous (TP) concentrations and stocks. Soil sampling was conducted within Kilombero Plantations Ltd. (KPL), a high intensity commercial farm located in Kilombero, Tanzania, and also on surrounding smallholder farms, capturing a gradient of agricultural intensity. We found that irrigation had a positive effect on SOC concentrations and stocks while fertilization had a negative effect. Rain-fed non-fertilized production had no effect on soil properties when compared to native vegetation. No difference was found in concentrations of TN or TP across the intensity gradient. However, TN stocks were significantly larger in the surface soils (0-30 cm) of the most intensive production system when compared to native vegetation and smallholder production.

Place, publisher, year, edition, pages
2020. Vol. 9, no 4, article id 121
Keywords [en]
soil organic carbon, agricultural intensity, nitrogen, phosphorous, irrigation, fertilization
National Category
Social and Economic Geography
Identifiers
URN: urn:nbn:se:su:diva-182896DOI: 10.3390/land9040121ISI: 000533901100006OAI: oai:DiVA.org:su-182896DiVA, id: diva2:1450680
Available from: 2020-07-01 Created: 2020-07-01 Last updated: 2023-02-06Bibliographically 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, JohnAlavaisha, EdmondLyon, Steve W.Lindborg, ReginaManzoni, Stefano

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