title: Water and soil management across agricultural land use and climatic gradient of Mt. Kilimanjaro
Creators: name: Kimaro, Jerome Gadi
Publisher: name: University of Bayreuth
Year: 2022
Subjects: subject: agroecosystem
subject: farmers
subject: land-use
subject: water
subject: soil
subject: 550

description: Mountainous agroecosystems are critically important for agricultural production. However, they are increasingly degraded due to human-induced disturbances such as soil erosion, nutrients loss, deforestation, and water loss. Fertile soils and water resources are scarce resources and strongly competed for among farmers to meet their production targets. In consideration of increased human food demands, and rapid land-use conversion, the conservation of mountain agroecosystems deserves special attention to guarantee a sustainable and long-term ecosystem services provision. The objective of this thesis is to analyse the management of soil and agricultural water use in the southern slopes of Mt. Kilimanjaro, with respect to different farming systems and along an elevational gradient. A total of four related studies were conducted: our first two studies analyse the distribution and discharge of irrigation canals and management of agricultural water in the agroecosystem. The third study examines available local knowledge on soil erosion and compares the extent of soil erosion under different farming systems. Finally, the fourth study assesses differences in soil properties under different farming systems and along an elevational gradient in the mountain agroecosystem. To analyse the discharge patterns of traditional irrigation systems, we monitored water flows in canals in eleven locations at different altitudes and during the dry and wet seasons. Canal water levels were recorded times a day, i.e., in the morning, afternoon, and evening for the duration of eight months. Potential causes responsible for canal flow fluctuations, such as irregular cleaning and blockage, were also recorded. It found that canals’ discharge was nearly twice in the lower compared to the upper elevation zone. The median daily discharges equalled 12.6 l/s, 9.5 l/s, and 7.0 l/s in the lower, mid, and upper areas, respectively. Discharge was also higher during the dry compared to wet seasons. In some villages, canals have changed their annual discharge patterns from perennial to seasonal. An even distribution of canal water among users was not possible due to topographical attributes, in particular terrain ruggedness and slope. Excessive water losses were attributed to excessive water leakage. To analyse the local knowledge about soil erosion management and indicators of soil erosion, a socio-economic survey through Focus Group Discussions (FGDs) was conducted. We found that the majority of local farmers were well-informed about erosion control methods and indicators of soil erosion. However, challenges, such as low income and lack of land ownership, limit their effective participation in sustainable soil management. To analyse patterns of soil erosion, six erosion traps were installed under maize and agroforestry systems. Rainfall, run-off, and sediment losses were monitored during the heavy rainy seasons. Land cover change within crop units employed analysis of Google Earth Pro images. The run off was nearly twice in the lower compared to upper elevation zones under both maize and agroforestry. Run-off decreased significantly in the mid and upper compared to the lower elevation zones (-21.2 l and -17.8 l, respectively). Also, a run-off was significantly higher under maize compared to agroforestry (13.4 l). Sediment loss was three times higher in the lower compared to the upper elevations, and seven times higher under maize compared to agroforestry. Sediment loss decreased slightly between the mid and upper elevation zones (-31.5 g and -31.3 g, respectively), and increased under maize (13.4 g) compared to agroforestry. Rainfall was positively correlated with surface run-off, and the difference was significant between the two farming systems. Farm vegetation was different between the two farming systems: under agroforestry, perennial vegetation cover dominated, with a higher proportion in the upper and midelevation zone. Seasonal vegetation cover was dominant under the maize system in the lower elevation zone. Fodder patches and settlement areas indicated only a small proportion under both farming systems. We suggest that current patterns of farm vegetation cover contribute strongly to patterns of surface run-off and sediment loss in the study area. To analyse differences in soil properties, 24 sampling plots were established across different elevational gradients and farming systems It was found that sand content increased, clay content and bulk density decreased with increasing elevation. Soil C and N contents were slightly lower in maize compared to agroforestry, but not soil P. Soil C and N contents increased in the upper compared to the lower elevation zones, while P decreased. The content of cations from CEC showed a heterogeneous picture, the largest difference was that soil Ca and Mg were lower in the upper elevation zones. It was found that spatial variation in soil properties is influenced by both management and hereditary conditions of the soil within the ecosystem. Soil properties are combined in different proportions along an elevational gradient and under different farming systems, which impact soil functions and community well-being differently from one location of the agroecosystem to another. We conclude that the consequences of the current management of agricultural water and soil vary at a spatial scale, thus requiring solutions that are location-specific and prioritized differently. Therefore, farming systems transition in mountainous agroecosystem requires acknowledging the contribution of different knowledge disciplines and reinforcement of multi-stakeholders efforts.