Assessment of salt-affected soil in selected rice irrigation schemes in Tanzania: understanding salt types for optimizing management approaches

Salt-affected soils have serious implications for agricultural land quality and productivity, leading to a reduction in the net cultivable area available for food production. This issue has emerged as one of the foremost global challenges in recent years, impacting both food security and environmental sustainability. This research focuses on soil characterizations conducted in three irrigation schemes to understand the types, distribution, and nature of salt-affected soils. Auger observations served as the basic methodology for soil unit delineation in this study. Twelve representative soil pits with a depth of more than 160 cm were described, and undisturbed and disturbed samples were collected and analyzed for physical and chemical properties. The schemes were characterized by low levels of available phosphorus, organic carbon, and total nitrogen, as well as variations in exchangeable bases. Furthermore, 37.5% of the analyzed horizons highlighted the presence of salt-affected soils. Sodium was the predominant cation, followed by magnesium, potassium, and calcium. Likewise, HCO3− was the dominant anion, followed by Cl− and SO42−. The results of this study reveal the existence of two types of salt-affected soil. Uturo irrigation scheme had sodic soils, while the Ndungu irrigation scheme had saline-sodic soils. Additionally, both sodic and saline-sodic soils have been discovered in the Mawala irrigation scheme. The root cause of this challenge is inherent soil conditions, exacerbated by inadequate drainage infrastructure. Therefore, measures such as the application of gypsum followed by salt leaching, improving soil drainage by incorporating organic matter, improving drainage infrastructure, and using rice-tolerant varieties are recommended to mitigate salt stress and improve soil fertility. It is imperative to establish a robust framework for continuous monitoring and regular assessment of soil health to enable timely interventions and informed decisions for sustainable agricultural management

Floods stress in lowland rice production: experiences of rice farmers in Kilombero and Lower-Rufiji floodplains, Tanzania

The resilience of rice production to floods is a crucial aspect of agricultural development in flood-prone regions. However, little is known about the farming practices and challenges of rice farmers in two river basins in Tanzania: Lower-Rufiji and Kilombero, where rice is the main crop grown. This study aimed to investigate the experiences of farmers in these two rice-growing floodplains regarding the impact of floods on lowland rice production and farmer livelihoods, and the strategies they use to cope with floods. The study used a mixed-methods approach that involved household surveys, key informant interviews, and transect walks to collect data from 180 rice farmers and 14 experts and community leaders. The data analysis revealed that floods were the dominant stressor affecting rice production, occurring mostly during the long rainy season and experienced by all farmers in both locations. Floods not only caused significant crop losses, especially in Lower-Rufiji where farmers reported losing between 75 and 100% of their yield in cases of extreme floods, but also made it difficult to establish and manage crops, leading to crop land abandonment. Floods also affected the livelihoods of rice farmers by forcing them to abandon, rent, or sell their farms. Coexistence of floods with other biotic and abiotic stresses such as crop diseases and droughts also limited the use of short maturing high yielding rice varieties. Farmers have adopted on-farm strategies such as adjusting planting schedules, using different varieties of rice, changing to other crops or activities after the floods to cope with floods, but these practices face numerous challenges. The study recommends the development of early warning systems, breeding for flood-tolerant rice varieties, introgression of tolerance traits to multiple stresses and improving crop establishment methods to enhance the resilience of farmers to floods and other extreme climate events

Insights into landforms and soils for explaining plague hosts-vectors interaction in Western Usambara Mountains, Tanzania

PhD. ThesisWestern Usambara Mountains in Lushoto District, Tanzania, are highly populated owing to favourable climatic conditions for production of both cash and food crops such as coffee, tea, maize, beans, potatoes and assorted fruits and vegetables. Some areas in the district are also potential as tourist destinations. However, clusters of villages in the district are reported to be hot-spots of plague recurrence that has caused deaths of thousands of people. Plague outbreaks in some villages of Lushoto District show a high frequency (on average, more than 1 year out of three) while other villages, very nearby (0.05) on burrow port orientation. The results showed that both soil depth and temperature encouraged burrow use in the high plague frequency landscape (p<0.05). Soil depth, dry soil consistence and subsoil relative humidity (RH (%) within 30 cm depth) significantly (p<0.05) could explain the burrow abundance in the medium plague frequency landscape. The use of burrows depended on the resistance of burrow to collapse, a characteristics which is dependent on the compaction of topsoil. However, dry subsoil consistence discouraged burrowing. Subsoil dry consistence had a significant (p<0.05) negative influence on burrow portal orientation in the medium plague frequency area, something attributed to compaction of the soils. It is concluded that soil physical and soil microclimate in the high plague frequency landscape encourage burrowing, a phenomenon correlating with the reported human plague contact risks. The information obtained from this study could be applied for surveillance, monitoring and control of rodent populations.Landscape-ecological Clarification of Bubonic Plague Distribution and Outbreaks in the Western Usambara Mountains, Tanzania (LEPUS) via VLIR own initiative projec

Insights into landforms and soils for explaining plague hosts-vectors interaction in Western Usambara Mountains, Tanzania

PhD. ThesisWestern Usambara Mountains in Lushoto District, Tanzania, are highly populated owing to favourable climatic conditions for production of both cash and food crops such as coffee, tea, maize, beans, potatoes and assorted fruits and vegetables. Some areas in the district are also potential as tourist destinations. However, clusters of villages in the district are reported to be hot-spots of plague recurrence that has caused deaths of thousands of people. Plague outbreaks in some villages of Lushoto District show a high frequency (on average, more than 1 year out of three) while other villages, very nearby (0.05) on burrow port orientation. The results showed that both soil depth and temperature encouraged burrow use in the high plague frequency landscape (p<0.05). Soil depth, dry soil consistence and subsoil relative humidity (RH (%) within 30 cm depth) significantly (p<0.05) could explain the burrow abundance in the medium plague frequency landscape. The use of burrows depended on the resistance of burrow to collapse, a characteristics which is dependent on the compaction of topsoil. However, dry subsoil consistence discouraged burrowing. Subsoil dry consistence had a significant (p<0.05) negative influence on burrow portal orientation in the medium plague frequency area, something attributed to compaction of the soils. It is concluded that soil physical and soil microclimate in the high plague frequency landscape encourage burrowing, a phenomenon correlating with the reported human plague contact risks. The information obtained from this study could be applied for surveillance, monitoring and control of rodent populations.Landscape-ecological Clarification of Bubonic Plague Distribution and Outbreaks in the Western Usambara Mountains, Tanzania (LEPUS) via VLIR own initiative projec

Assessment of salt-affected soil in selected rice irrigation schemes in Tanzania: understanding salt types for optimizing management approaches

Journal articleSalt-affected soils have serious implications for agricultural land quality and productivity, leading to a reduction in the net cultivable area available for food production. This issue has emerged as one of the foremost global challenges in recent years, impacting both food security and environmental sustainability. This research focuses on soil characterizations conducted in three irrigation schemes to understand the types, distribution, and nature of salt-affected soils. Auger observations served as the basic methodology for soil unit delineation in this study. Twelve representative soil pits with a depth of more than 160 cm were described, and undisturbed and disturbed samples were collected and analyzed for physical and chemical properties. The schemes were characterized by low levels of available phosphorus, organic carbon, and total nitrogen, as well as variations in exchangeable bases. Furthermore, 37.5% of the analyzed horizons highlighted the presence of salt-affected soils. Sodium was the predominant cation, followed by magnesium, potassium, and calcium. Likewise, HCO3− was the dominant anion, followed by Cl− and SO42−. The results of this study reveal the existence of two types of salt-affected soil. Uturo irrigation scheme had sodic soils, while the Ndungu irrigation scheme had saline-sodic soils. Additionally, both sodic and saline-sodic soils have been discovered in the Mawala irrigation scheme. The root cause of this challenge is inherent soil conditions, exacerbated by inadequate drainage infrastructure. Therefore, measures such as the application of gypsum followed by salt leaching, improving soil drainage by incorporating organic matter, improving drainage infrastructure, and using rice-tolerant varieties are recommended to mitigate salt stress and improve soil fertility. It is imperative to establish a robust framework for continuous monitoring and regular assessment of soil health to enable timely interventions and informed decisions for sustainable agricultural management.Climate Smart Africa Rice Project, Grant No.19-03-KU

Predicting small mammal and flea abundance using landform and soil properties in a plague endemic area in Lushoto District, Tanzania

Small mammals particularly rodents, are considered the primary natural hosts of plague. Literature suggests that plague persistence in natural foci has a root cause in soils. The objective of this study was to investigate the relationship between on the one hand landforms and associated soil properties, and on the other hand small mammals and fleas in West Usambara Mountains in Tanzania, a plague endemic area. Standard field survey methods coupled with Geographical Information System (GIS) technique were used to examine landform and soils characteristics. Soil samples were analysed in the laboratory for physico-chemical properties. Small mammals were trapped on pre-established landform positions and identified to genus/species level. Fleas were removed from the trapped small mammals and counted. Exploration of landform and soil data was done using ArcGIS Toolbox functions and descriptive statistical analysis. The relationships between landforms, soils, small mammals and fleas were established by generalised linear regression model (GLM) operated in R statistics software. Results show that landforms and soils influence the abundance of small mammals and fleas and their spatial distribution. The abundance of small mammals and fleas increased with increase in elevation. Small mammal species richness also increases with elevation. A landform-soil model shows that available phosphorus, slope aspect and elevation were statistically significant predictors explaining richness and abundance of small mammals. Fleas’ abundance and spatial distribution were influenced by hill-shade, available phosphorus and base saturation. The study suggests that landforms and soils have a strong influence on the richness and evenness of small mammals and their fleas’ abundance hence could be used to explain plague dynamics in the area

Predicting small mammal and flea abundance using landform and soil properties in a plague endemic area in Lushoto District, Tanzania

Small mammals particularly rodents, are considered the primary natural hosts of plague. Literature suggests that plague persistence in natural foci has a root cause in soils. The objective of this study was to investigate the relationship between on the one hand landforms and associated soil properties, and on the other hand small mammals and fleas in West Usambara Mountains in Tanzania, a plague endemic area. Standard field survey methods coupled with Geographical Information System (GIS) technique were used to examine landform and soils characteristics. Soil samples were analysed in the laboratory for physico-chemical properties. Small mammals were trapped on pre-established landform positions and identified to genus/species level. Fleas were removed from the trapped small mammals and counted. Exploration of landform and soil data was done using ArcGIS Toolbox functions and descriptive statistical analysis. The relationships between landforms, soils, small mammals and fleas were established by generalised linear regression model (GLM) operated in R statistics software. Results show that landforms and soils influence the abundance of small mammals and fleas and their spatial distribution. The abundance of small mammals and fleas increased with increase in elevation. Small mammal species richness also increases with elevation. A landform-soil model shows that available phosphorus, slope aspect and elevation were statistically significant predictors explaining richness and abundance of small mammals. Fleas’ abundance and spatial distribution were influenced by hill-shade, available phosphorus and base saturation. The study suggests that landforms and soils have a strong influence on the richness and evenness of small mammals and their fleas’ abundance hence could be used to explain plague dynamics in the area