Introduction: Internet addiction among the youth has become a public health concern. It leads to impairments in several aspects of life. Previous studies identified individual and environmental risk factors for internet addiction. The effect of online activities on youth internet use behavior is not well investigated. This study assessed the prevalence of internet addiction and determined the roles of online activities for internet addiction among students in Bahir Dar University. Methods: Data were collected from 812 randomly selected undergraduate regular program students recruited from 10 departments. Participants completed a pre-tested structured questionnaire. Results: The results indicated that 35.2% of students were classified as being addicted to the internet. The four most important online activities students engaged on the internet are social networking (75.5%), entertainments (73.6%), academic works (72.5%), and online game (60.8%). Including online activity variables improved the explanation of internet addicted behavior over the individual and environmental attributes. Online activities explained 48.4% of the variance in internet addiction. Students who did not use the internet for social networking (AOR = .11; 95% CI: .06 - .21) and online game (AOR = .31; 95% CI: .21 - .46) were less likely to be internet addicted. Conclusions: Our findings revealed that more than one third of the participants were addicted internet users. Online activities better predict students’ addicted internet use behavior than individual and environmental attributes. Thus, university authorities and other concerned bodies need to be aware of the prevalence of IA and introduce regulatory mechanisms to limit the usage of potentially addictive online internet applications and promote responsible internet use behavior.

Intensification of rainfed agriculture in the Ethiopian highlands has resulted in soil degradation and hardpan formation, which has reduced rooting depth, decreased deep percolation, and increased direct runoff and sediment transport. The main objective of this study was to assess the potential impact of subsoiling on surface runoff, sediment loss, soil water content, infiltration rate, and maize yield. Three tillage treatments were replicated at five locations: (i) no tillage (zero tillage), (ii) conventional tillage (ox-driven Maresha plow, up to a depth of 15 cm), and (iii) manual deep ripping of the soil's restrictive layers down to a depth of 60 cm (deep till). Results show that the posttreatment bulk density and penetration resistance of deep tillage was significantly less than in the traditional tillage and zero-tillage systems. In addition, the posttreatment infiltration rate for deep tillage was significantly greater, which resulted in significantly smaller runoff and sedimentation rates compared to conventional tillage and zero tillage. Maize yields were improved by 6% under deep tillage compared to conventional tillage and by 29% compared to no tillage. Overall, our findings show that deep tillage can be effective in overcoming some of the detrimental effects of hardpans in degraded soils.

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<p>General knowledge based on the good agricultural soils in temperate climates is that no-till and conservation-till practices increase infiltration of the rainwater and decrease runoff and erosion.  Experiments in the semi-humid Ethiopian highlands do not often show the same benefits and in many cases no-till actually increases runoff above conventional and deep tillage. In contrast, for conservation-tillage with mulch at the surface, more of the water infiltrates and enhances plant growth</p><p>Reduced tillage systems increase infiltration through soil fauna that form soil macropores through which rainwater flows to the subsoil bypassing the soil matrix with limited conductivity. Most degraded soils (at least in the Ethiopian highlands) have a hardpan at shallow depths restricting downward movement of water. Runoff on conventionally tilled soils is caused by saturation excess when the perched water table in the plowed soil layer reaches the surface.  Thus, the amount of runoff is determined by the water free pore space in the surface layer.  Since this pore space is less under no-till, no-till has greater amounts of runoff than conventional till. </p><p>Under mulch tillage, organic matter is introduced at the surface and soil fauna becomes well-developed which will improve the soil structure and porosity of the soil.  This structure will be maintained because the mulch decreases the sediment concentration in the water and the pores will remain open. Under conventional tillage sediment concentrations are high and any pores formed will be filled up with sediment. Our expectation is that since organic matter under mixed farming is used to feed the cattle, widespread implementation of no-till and conservation tillage will be limited to areas with high value crops in which farmers can afford using organic matter as a mulch.</p>

The highlands serve as water towers for the blue water in the surrounding area, with often insufficient rainfall for rainfed crops. The population is growing in the highlands, changing the hydrology and blue and green water availability. One of the changes that affect the highlands of Ethiopia is the rapidly expanding areas of small patches of eucalyptus on farmers fields. This manuscript aims to sort through the limited available literature and develop a water balance model as a starting point to discuss how hydrology is affected by increased acreage of eucalyptus in the highlands. We find some evidence in the literature that patches of eucalyptus during the dry phase may withdraw water from the subsoil up to twice the rate of evapotranspiration when the soil water is not limited. Since saturation excess generates surface runoff in the subhumid and humid highlands, water withdrawn during the dry phase should be made up before the area with eucalyptus becomes hydraulically active. The amount of water that can be removed from storage by eucalyptus is greater in areas with a long dry monsoon phase than in temperate climates for the same increase in trees. We also found, as expected, that the eucalyptus water balance model, as developed in this paper, was not valid for areas in semi-arid and arid regions. Soil crusting and water repellency might induce infiltration excess runoff. A tentative implication is that since most blue water is produced in the areas with the highest rainfall, eucalyptus in subhumid and humid monsoon regions will affect the blue water supply downstream but not the plant available green water although shading will decrease yield in the immediate surroundings of the eucalyptus trees.