| 1. |
- Alavaisha, Edmond, 1988-
(författare)
-
Agricultural expansion impacts on wetland ecosystem services from Kilombero Valley, Tanzania
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Land use change has major impact on the world’s wetland ecosystems and biodiversity. The motivation behind this change has been to increase agricultural production, often resulting in negative effects on water quality and soil fertility. Tanzania has carried out a large expansion and intensification of agriculture under the Kilimo kwanza (First agriculture) initiative which has triggered the need for better knowledge on land use change effects and associated ecosystem functioning. This thesis considers small-scale irrigation schemes to understand the effects of agriculture expansion and farming practices on nutrients, water quality and ecosystem services (ES) in Kilombero Valley, Tanzania. The study approach is multidisciplinary involving interviews, remote sensing, geographical information system techniques, and in-field soil and water ecological sampling. The major land use change in the valley during the last three decades was transformation from forest, bushland and grassland into cultivated land. The rate of change was faster adjacent to irrigation schemes and most changes occurred downstream irrigation canals, close to the floodplain. Irrigation and fertilization contributed to soil carbon and nitrogen accumulation in crop fields, which both declined in concentration with depth into the soil. However, such management practices and agricultural land expansion had impacts on several ES – especially water quality in streams. Streams surrounded mainly by cultivated land, as well as downstream areas, had lower water quality compared to streams with less settlement, more natural vegetation and upstream areas. Furthermore, when evaluated, macroinvertebrates indices were found to be a good indicator of water quality and a complement to chemical and physical water analysis. Irrigation farming produced more food compared to rainfed farming, and also other ES such as flood regulation, erosion control and several cultural services, depending on the river discharge. The thesis shows the importance to use irrigation/fertilization management to enhance soil fertility and preserve soil structure, but also the need for proper irrigation management to prevent flooding and erosion, conserve natural vegetation, and protect water quality. To enhance nature conservation, preserve biodiversity and secure future supply of ES in the valley, investment in irrigation infrastructures should be done at small-scale to mitigate the large-scale exploitation of Kilombero wetland.
|
|
| 2. |
- Alavaisha, Edmond, et al.
(författare)
-
Assessment of Water Quality Across Irrigation Schemes : A Case Study of Wetland Agriculture Impacts in Kilombero Valley, Tanzania
- 2019
-
Ingår i: Water. - : MDPI AG. - 2073-4441. ; 11:4
-
Tidskriftsartikel (refereegranskat)abstract
- Coupled change in land and water use due to increased farming intensity is a main factor affecting water quality and quantity, ecological functions and biodiversity globally. Prolonging growing seasons and increasing productivity in wetlands through irrigation have been targeted for increasing food security, particularly in developing countries. Nevertheless, irrigation and drainage have often been associated with degradation of water quality through increased agrochemical and fertiliser runoff and leaching at local scales. In this study, we investigated water quality in streams used for irrigation in a wetland area in Kilombero Valley, Tanzania. We measured physical-chemical water parameters and collected macroinvertebrates with different sensitivity to water quality across several small irrigation schemes covering various conditions. Turbidity, temperature, nitrate-N, and ammonium-N were significantly higher at sampling sites downstream of irrigation compared to upstream. Macroinvertebrate diversity, richness and average score per taxa (ASPT) were higher in general in sampling sites upstream of irrigation, with more sensitive macroinvertebrates decreasing in abundance downstream. There was a positive correlation between physical-chemical parameters and macroinvertebrate indices across the sites. We demonstrate that macroinvertebrate indices can be used as a quick assessment of water quality in response to irrigation schemes in small-scale farming systems of Tanzania. This in turn can allow us to track changes affecting wetland ecosystem function and biodiversity at higher trophic levels and across larger scales, thereby providing useful early warnings to help avoid widespread degradation under widespread agricultural intensification.
|
|
| 3. |
- Alavaisha, Edmond, et al.
(författare)
-
Different agricultural practices affect soil carbon, nitrogen and phosphorous in Kilombero -Tanzania
- 2019
-
Ingår i: Journal of Environmental Management. - : Elsevier BV. - 0301-4797 .- 1095-8630. ; 234, s. 159-166
-
Tidskriftsartikel (refereegranskat)abstract
- Converting natural and semi-natural vegetation to agriculture is currently the most significant land use change at global scale. This conversion leads to changes in soil nutrients and increased CO2 emissions. However, knowledge of how soil organic carbon and nutrients change under various farming management is still limited, especially for small scale farming systems. This study evaluated the effects of different farming systems on soil organic carbon (SOC), total nitrogen (TN) and total phosphorous (TP) in subsistence farming at Kilombero, Tanzania. We applied an in-situ experimental setup, comparing maize and rice farming with and without irrigation and difference in fertilizers, with replicated soil sampling at five soil depths to a depth of 60 cm. The results show that irrigation had a positive effect on profile-averaged concentrations of SOC and TN, while fertilization had a positive effect on TN. Higher concentrations and stocks of TN were found in maize field soils compered to rice fields. In the vertical profile, irrigation and fertilization had positive effects on concentrations of SOC and TN of top soil layers, and the interaction between irrigation and fertilization extended the effect to deeper soil layers. Our results indicate that moderate irrigation and fertilization can help to improve carbon storage and nutrient availability (TN) in small-scale farming soils in Africa.
|
|
| 4. |
|
|
| 5. |
- Alavaisha, Edmond, et al.
(författare)
-
Effects of Land Use Change Related to Small-Scale Irrigation Schemes in Kilombero Wetland, Tanzania
- 2021
-
Ingår i: Frontiers in Environmental Science. - : Frontiers Media SA. - 2296-665X. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Increasing agricultural land use intensity is one of the major land use/land cover (LULC) changes in wetland ecosystems. LULC changes have major impacts on the environment, livelihoods and nature conservation. In this study, we evaluate the impacts of investments in small-scale irrigation schemes on LULC in relation to regional development in Kilombero Valley, Tanzania. We used Remote Sensing (RS) and Geographical Information System (GIS) techniques together with interviews with Key Informants (KI) and Focus Group Discussion (FGD) with different stakeholders to assess the historical development of irrigation schemes and LULC change at local and regional scales over 3 decades. Overall, LULC differed over time and with spatial scale. The main transformation along irrigation schemes was from grassland and bushland into cultivated land. A similar pattern was also found at the regional valley scale, but here transformations from forest were more common. The rate of expansion of cultivated land was also higher where investments in irrigation infrastructure were made than in the wider valley landscape. While discussing the effects of irrigation and intensification on LULC in the valley, the KI and FGD participants expressed that local investments in intensification and smallholder irrigation may reduce pressure on natural land cover such as forest being transformed into cultivation. Such a pattern of spatially concentrated intensification of land use may provide an opportunity for nature conservation in the valley and likewise contribute positively to increased production and improve livelihoods of smallholder farmers.
|
|
| 6. |
|
|
| 7. |
- Alavaisha, Edmond, 1988-, et al.
(författare)
-
Supply and demand of ecosystem services among smallholder farmers in irrigated and rainfed farming, Kilombero, Tanzania
- 2022
-
Ingår i: Ecosystems and People. - : Informa UK Limited. - 2639-5908 .- 2639-5916. ; 18:1, s. 661-671
-
Tidskriftsartikel (refereegranskat)abstract
- A sufficient supply of ecosystem services (ESs) in agriculture provides the basis for human sustainable development. Intensified large-scale farming has changed wetland ecosystems extensively by reducing both the resilience and capacity to support production of many ESs. Small-scale farming may also affect the generation of ESs where the impact often reflects the differences in farming practices. This paper explores the supply and demand of the ESs between management practices, irrigated and rainfed, of smallholder farmers in Kilombero wetland, Tanzania. We conducted interviews involving 30 households and two focus groups with five discussants for each practice, rainfed and irrigation. Generally, we found that the need for ES, especially food, water and flood control, in both farming practices, were exceeding the capacity to supply. In general, irrigation farming compared to rainfed farming was associated with higher levels of food production, increasing flood regulation and erosion control. However, the ES delivery and need were not uniform depending on the river discharge. The differences in supply and demand of ESs between farming practices suggest that society would benefit from investing in irrigation and regulatory infrastructures to minimize flooding risk and to build up the ecosystem’s natural capacity to produce services. Such practical policy-relevant measures could balance the gap between supply and demand of ESs in smallholder farming systems in Tanzanian wetland.
|
|
| 8. |
- Livsey, John, et al.
(författare)
-
Soil Carbon, Nitrogen and Phosphorus Contents along a Gradient of Agricultural Intensity in the Kilombero Valley, Tanzania
- 2020
-
Ingår i: Land. - : MDPI AG. - 2073-445X. ; 9:4
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 9. |
- Mbande, Victor, 1985-, et al.
(författare)
-
Becoming a progressive farmer : Farmer-State and market interactions in improved smallholder irrigation in Kilombero valley, Tanzania
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Studies on irrigation development in Africa point to a large potential in smallholders’ irrigation. Nevertheless, policy efforts prioritise transformation through private (large-scale) capital rather than small-scale smallholder irrigation. Using a mixed-methods approach, this study contributes to the understanding of internal dynamics among smallholders in irrigation from four irrigating villages in Kilombero, Tanzania. We focus on public investments in village-level smallholder irrigation and show how the word ‘tija’, a local discourse of progressiveness, is widely used in the current efforts to commercialize rice production through irrigation, but also closely linked to emergence of the so called ‘progressive farmers’ as a desired development outcome of irrigation policy. Building on the literature on farmer-led irrigation development, we analyse a case of both farmer-led and state supported irrigation. The farmers initiated irrigation by digging unlined canals which attracted state supported investments in lining canals. Dynamics in irrigation were rooted in the ideas and practices of progressiveness and differentiatiation among smallholders. We conclude that, this study shows how state interventions can improve farmer-led initiatives as the state-market-smallholder interact. Aspirations for progressiveness were also embedded in the interaction as current market interventions and ongoing public investments in lining smallholders’ irrigation which preferred the entrepreneurial ‘progressive farmers’.
|
|
