The effect of nitrogen-fertilizer and optimal plant population on the profitability of maize plots in the Wami River sub-basin, Tanzania: A bio-economic simulation approach.

Maize (Zea mays L.) is the essential staple in sub-Saharan Africa (SSA) and Tanzania in particular; the crop accounts for over 30% of the food production, 20% of the agricultural gross domestic product (GDP) and over 75% of the cereal consumption. Maize is grown under a higher risk of failure due to the over-dependence rain-fed farming system resulting in low income and food insecurity among maize-based farmers. However, many practices, including conservation agriculture, soil and water conservation, resilient crop varieties, and soil fertility management, are suggested to increase cereal productivity in Tanzania. Improving planting density, and the use of fertilizers are the immediate options recommended by Tanzania's government. In this paper, we evaluate the economic feasibility of the improved planting density (optimized plant population) and N-fertilizer crop management practices on maize net returns in semi-arid and sub-humid agro-ecological zones in the Wami River sub-Basin, Tanzania. We introduce a bio-economic simulation model using Monte Carlo simulation procedures to evaluate the economic viability of risky crop management practices so that the decision-maker can make better management decisions. The study utilizes maize yield data sets from two biophysical cropping system models, namely the APSIM and DSSAT. A total of 83 plots for the semi-arid and 85 plots for the sub-humid agro-ecological zones consisted of this analysis. The crop management practices under study comprise the application of 40 kg N-fertilizer/ha and plant population of 3.3 plants/m2 . The study finds that the use of improved plant population had the lowest annual net return with fertilizer application fetching the highest return. The two crop models demonstrated a zero probability of negative net returns for farms using fertilizer rates of 40 kg N/ha except for DSSAT, which observed a small probability (0.4%) in the sub-humid area. The optimized plant population presented 16.4% to 26.6% probability of negatives net returns for semi-arid and 14.6% to 30.2% probability of negative net returns for sub-humid zones. The results suggest that the application of fertilizer practices reduces the risks associated with the mean returns, but increasing the plant population has a high probability of economic failure, particularly in the sub-humid zone. Maize sub-sector in Tanzania is projected to continue experiencing a significant decrease in yields and net returns, but there is a high chance that it will be better-off if proper alternatives are employed. Similar studies are needed to explore the potential of interventions highlighted in the ACRP for better decision-making.

Stakeholder-driven transformative adaptation is needed for climate-smart nutrition security in sub-Saharan Africa.

Improving nutrition security in sub-Saharan Africa under increasing climate risks and population growth requires a strong and contextualized evidence base. Yet, to date, few studies have assessed climate-smart agriculture and nutrition security simultaneously. Here we use an integrated assessment framework (iFEED) to explore stakeholder-driven scenarios of food system transformation towards climate-smart nutrition security in Malawi, South Africa, Tanzania and Zambia. iFEED translates climate-food-emissions modelling into policy-relevant information using model output implication statements. Results show that diversifying agricultural production towards more micronutrient-rich foods is necessary to achieve an adequate population-level nutrient supply by mid-century. Agricultural areas must expand unless unprecedented rapid yield improvements are achieved. While these transformations are challenging to accomplish and often associated with increased greenhouse gas emissions, the alternative for a nutrition-secure future is to rely increasingly on imports, which would outsource emissions and be economically and politically challenging given the large import increases required.

Rapid environmental flow assessment for sustainable water resource management in Tanzania's Lower Rufiji River Basin: A scoping review.

The use of Environmental flow (e-Flow) assessment is a widely adopted approach to facilitate informed decision-making concerning sustainable management and utilization of water resources in river systems. The Lower Rufiji River Basin faces various developmental pressures from several sectors, including hydropower, mining, agriculture, livestock, fishing, and tourism, necessitating effective management of the sub-catchment area to prevent significant environmental impacts. Consequently, it is essential to acquire a comprehensive comprehension of the catchment's attributes, encompassing both climatic and non-climatic factors. Supported by e-Flow batch analysis of the available data at Stiegler's Gorge using the global environmental flow calculator, a scoping review was conducted to determine the status of environmental flow in the lower Rufiji River basin. The findings suggest that, while there has been progress in understanding eFlow estimation, limited data and ecohydrological processes' poor comprehension still present challenges. Hydrological and holistic methodologies are commonly employed in Tanzania; however, uncertainties remain, raising questions concerning trust between decision-making tools and water resource utilization by the public. Climate variability influences e-Flow in the Rufiji River Basin, and the projections under various scenarios indicate an increased temperature, varying rainfall, and humidity levels. Further, the area has been identified as a vulnerable "hotspot" where communities face greater climate stressor risks. With the existing and planned developmental projects in the basin, including hydroelectric dams, mining, agriculture, livestock, and fisheries, it is critical to assess e-Flow in the Lower Rufiji River basin to ensure resource sustainability. Advocating for preserving a dynamic environmental flow regime in rivers is recommended, considering the Rufiji River Basin's habitat connectivity. The future research direction should be quantifying the contribution of base flow to the surface flow, and salinity dynamics in the Lower Rufiji River Basin, which can affect the Delta's biodiversity.