Wild and domesticated animals can harbor a pathogenic Escherichia colt strain designated as O157:H7. Potential health problems could occur if strain O157:H7 is a more robust survivor in defecated waste than commonly used indicator bacteria. A laboratory study was conducted to assess E. colt O157:H7 survival relative to a nonpathogenie E. colt strain in two soils with different physical and chemical characteristics. Bacteria in the inoculated soils were enumerated on a weekly basis for 8 wk using a most probable number (MPN) technique. First-order decay models were used to describe bacteria mortality in the soils. Decay series were described slightly better by a two-stage function than by a single-stage function. Strain O157:H7 exhibited similar mortality patterns to the nonpathogenic E. colt in the same soil environment. Both E. ¢oli strains bad greater mortality rates in Pope silt loam (coarse-loamy, mixed, active, mesic Fluventic Dystrudept) than Zanesville silt loam (fine-silty, mixed, active, mesic Oxyaquic Fragiudalf). Differences in available soil water probably were the overriding factor in E. colt survival. Escherichia colt O157:H7 survival could be modeled in the same way as nonpathogenic E. colt and appears to have a slightly higher mortality rate.

Climate information and agro-advisory services are crucial in helping smallholder farmers and pastoralists in East Africa manage climate-related risks and adapt to climate change. However, significant gaps exist in provision of climate information that effectively addresses the needs of farmers and pastoralists. Most farmers and pastoralists, therefore, rely on indigenous knowledge (IK), where local indicators and experiences are used to observe and forecast weather conditions. While IK-based forecasting is inbuilt and established in many communities in East Africa, coordinated research and systematic documentation of IK for weather forecasting, including accuracy and reliability of IK is largely lacking. This paper documents and synthesizes existing IK for weather forecasting in East Africa using case studies from Ethiopia, Tanzania, and Uganda. The results show that farmers and pastoralists use a combination of meteorological, biological, and astrological indicators to forecast local weather conditions. IK weather forecasting is, therefore, crucial in supporting efforts to improve access to climate information in East Africa, especially in resource-poor and vulnerable communities. The paper draws valuable lessons on how farmers and pastoralists in East Africa use IK weather forecasts for making crop and livestock production decisions and demonstrates that the trust and willingness to apply scientific forecasts by farmers and pastoralists is likely to increase when integrated with IK. Therefore, a systematic documentation of IK, and a framework for integrating IK and scientific weather forecasting from national meteorological agencies can improve accuracy, uptake, and use of weather forecasts.

Soil organic carbon (SOC) is a potential soil fertility indicator for regulating nitrogen application in tropical farming systems. However, there are limited studies that have discussed SOC thresholds above or below which crop production could be diminished, or at which no or high response to nitrogen (N) application can be realized. This review explores the drivers of SOC concentration relevant for the establishment of thresholds. We further evaluate existing SOC thresholds for provoking no yield response or significant response to added N fertilizer. Key drivers for SOC concentration relevant in establishing thresholds are mainly climate, topography, texture, and land use management. Soil organic carbon threshold for sustaining soil quality is widely suggested to be about 2% below which deterioration may occur. For added N fertilizer management, specific SOC thresholds seem quite complex and are only valid after assuming other factors are non-limiting. In some soils, SOC levels as low as 0.5% result in fertilizer responses and soils as high as 2% SOC also respond to small N doses. Minimum SOC thresholds can be identified for a given soil type, but maximum thresholds depend on crop N requirements, crop N use efficiency and amount of N applied. However, there seem to exist critical total SOC ranges that could be targeted for optimal indigenous N supply and integrative soil functional benefits. These can be targeted as minimum levels in soil fertility restoration. In all, it is still difficult to establish a single minimum or maximum SOC threshold value that can be universally or regionally accepted.

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