Visualizing clogging up of soil pores in tropical degraded soils and their impact on green water productivity

Restrictive soil layers commonly known as hardpans restrict water and airflow in the soil profile and impede plant root growth below the plough depth. Preventing hardpans to form or ameliorate existing hardpans will allow plants root more deeply, increase water infiltration and reduce runoff, all resulting in greater amounts of water available for the crop (i.e. green water). However, there has been a lack of research on understanding the influence of transported disturbed soil particles (colloids) from the surface to the subsurface to form restrictive soil layers, which is a common occurrence in degraded soils. In this study, we investigated the effect of disturbed soil particles on clogging up of soil pores to form hardpans. Unsaturated sand column experiments were performed by applying 0.04 g/ml soil water solution in two sand textures. For each experiment, soil water solution infiltration process was visualized using a bright field microscope and soil particles remained in the sand column was quantified collecting and measuring leachate at the end of the experiment in the soil and water lab of Cornell University. Preliminary results show that accumulation of significant amount of soil particles occur in between sand particles and at air water interfaces, indicating the clogging of soil pores occurs as a result of disturbed fine soil particles transported from the soil surface to the subsurface

Arresting gully formation in the Ethiopian highlands

Over the past five decades, gullying has been widespread and has become more severe in the Ethiopian highlands. Only in very few cases, rehabilitation of gullies has been successful in Ethiopia due to the high costs. The objective of this paper is to introduce cost effective measures to arrest gully formation. The research was conducted in the Debre-Mewi watershed located at 30 km south of Bahir Dar, Ethiopia. Gullying started in the 1980s following the clearance of indigenous vegetation and intensive agricultural cultivation, leading to an increase of surface and subsurface runoff from the hillside to the valley bottoms. Gully erosion rates were 10–20 times the measured upland soil losses. Water levels, measured with piezometers, showed that in the actively eroding sections, the water table was in general above the gully bottom and below it in the stabilized sections. In order to develop effective gully stabilizing measures, we tested and then applied the BSTEM and CONCEPT models for their applicability for Ethiopian conditions where active gully formation has been occurring. We found that the model predicted the location of slips and slumps well with the observed groundwater depth and vegetation characteristics. The validated models indicated that any gully rehabilitation project should first stabilize the head cuts. This can be achieved by regrading these head cuts to slope of 40 degrees and armoring it with rock. Head cuts will otherwise move uphill in time and destroy any improvements. To stabilize side walls in areas with seeps, grass will be effective in shallow gullies, while deeper gullies require reshaping of the gullies walls, then planting the gully with grasses, eucalyptus or fruit trees that can be used for income generation. Only then there is an incentive for local farmers to maintain the structures

Seasonal surface drainage of sloping farmland : a review of its hydrogeomorphic impacts

The combination of runoff-generating areas (saturated soils) and overland flow concentration in features such as drainage ditches makes sloping farmland vulnerable to soil erosion. The establishment of drainage ditches aims at draining the excess of water from the farmland, particularly in areas where soils are saturated in the rainy season. The hydrogeomorphic impacts on the farmland itself and on downstream areas need however also to be studied. Off site, downstream problems comprise higher peak discharges, leading to gully initiation, an increase in sediment load, and flooding problems. On-site problems such as the development of the drainage ditches into (ephemeral) gullies are less documented, although they may be important, as illustrated in the Lake Tana Basin (Ethiopia). The similarities and interactions between ephemeral gully channels and drainage ditches have to be considered to better understand all effects of drainage. Drainage ditches are a potential source of conflict between farmers with different interests and power, as well as between upstream and downstream users. A case study on drainage ditches on sloping farmlands in the Lake Tana Basin showed that nine out of ten catchments had drainage densities by ditches ranging from 53 to 510 m ha−1. Drainage ditches were constructed with an average top width of 27 (±9) cm. A significant correlation was found between stone bund density (physical conservation structures) and ditch drainage density (R = −0·72), in line with the Ethiopian government's ban on drainage ditches in farmlands where stone bunds have been constructed

Gully cut- and- fill cycles as related to agromanagement : a historical curve number simulation in the Tigray Highlands

Gully cut-and-fill dynamics are often thought to be driven by climate and/or deforestation related to population pressure. However, in this case-study of nine representative catchments in the Northern Ethiopian Highlands, we find that neither climate changes nor deforestation can explain gully morphology changes over the twentieth century. Firstly, by using a Monte Carlo simulation to estimate historical catchment-wide curve numbers, we show that the landscape was already heavily degraded in the nineteenth and early twentieth century – a period with low population density. The mean catchment-wide curve number (> 80) one century ago was, under the regional climatic conditions, already resulting in considerable simulated historical runoff responses. Secondly, twentieth century land-cover and runoff coefficient changes were confronted with twentieth century changing gully morphologies. As the results show, large-scale land-cover changes and deforestation cannot explain the observed processes. The study therefore invokes interactions between authigenic factors, small-scale plot boundary changes, cropland management and sociopolitical forces to explain the gully cut processes. Finally, semi-structured interviews and sedistratigraphic analysis of three filled gullies confirm the dominant impact of (crop)land management (tillage, check dams in gullies and channel diversions) on gully cut-and-fill processes. Since agricultural land management – including land tenure and land distribution – has been commonly neglected in earlier related research, we argue therefore that it can be a very strong driver of twentieth century gully morphodynamics

Efl Teachers’ Practices And Challenges Of Teaching Reading The Case Of Grade 9 Students At Teppi Secondary And Preparatory School

The purpose of this study was to investigate teachers’ practices and challenges to teaching reading. The study was conducted in a sample of 4 teachers were selected purposefully and 64 students randomly selected in grade 9 students of Teppi secondary and preparatory school. In order to achieve these objective three sub-questions were designed. The first question focused how to EFL teachers practice teaching reading? The second question focus on challenges of teaching reading, and the last question focus on what strategies teachers’ used to support students of having reading problem. In order to understand the phenomenon in depth, qualitative approach was used with case study design. To collect the required data for the study, classroom observations, interviews and questionnaires were used as an instrument the gathered data indicated that most teachers used different reading strategies to practice teaching reading in the classroom. These includes, integrated reading strategies, read about, depending on the purpose of reading using scanning, skimming and intensive reading and giving reading comprehension activities were used. Even though there were good practices in teaching reading in the research school, there were challenges of teaching reading according this finding. These includes students’ over enrollment students’ back ground problem with regard to reading, un appropriate use of students centered method of teaching, lack of motivation lack of text books are major among the conditions. These make difficult for teachers to teach reading properly. This can be done through minimizing the enrollment rate of students in the class, using both teachers centered and students’ centered method appropriately, practicing students to read aloud, identifying and supporting students of having reading problems using phonics at tutorials program, motivate students to read, increase cooperative work of parents with school administrators and teachers to improve their learners’ educational performance in general and a reading particular. In additional giving trading for teachers especially on how and how often to use students’ centered method and how to implement teaching of phonics for students who lag behind in reading is the main concern of MOE as recommended in this study

Economic valuation on participatory gully rehabilitation in the Ethiopian highlands

The current severity of gully erosion is a major cause of increased sediment loads in rivers, but gully rehabilitation has proven to be challenging, with limited success. This paper describes gully rehabilitation efforts in the Ene-Chilala in the Blue Nile basin begun in early 2013, where low-cost gully rehabilitation has been effective with community participation. Initially farmers were reluctant to participate for religious reasons but with the aid of local priests and respected elders, community discussions and a visit to a rehabilitated gully, a consensus was reached to rehabilitate a 0.71-ha upland gully. The gully cut the foot path of 51 household head farmers; the time value cost of this gully erosion on local farmers by disrupting the foot path and enforce them to use an alternative road that increase their travel by 44 minutes was 33, 138 ETB y-1. The participatory rehabilitation measures consisted of regrading the gully head at 450, constructing low-cost check dams from locally available materials, and planting Pennisetumpurpureum grass and Sesbaniasesban. At the end of the first rainy season after implementation, 2300 tons of soil was conserved by the newly planted vegetation, compared with soil losses of 1900 and 1500 tons in two untreated, nearby gullies. In 2014, an additional 3300 tons of soil was conserved. The marginal rate of return on the gully rehabilitation investment was 2.5 based on the value of increased forage production alone. The success of this effort motivated farmers to voluntarily under take rehabilitation of five other gullies in the area

Biophysical landscape interactions: bridging disciplines and scale with connectivity

Landscape composition and land use impact the interactions between soil and vegetation. Differences in micro-behaviour, driven by the interplay of heterogeneous soil and vegetation dynamics, affect emergent characteristics across a landscape. Scaling approaches to understand the drivers of these emergent characteristics have been attempted, but the blueprint of interacting biophysical processes in landscapes is inherently messy and often still unknown. A complicating factor is single disciplinary focus in environmental sciences. Integrated knowledge is vital especially in view of future challenges posed by climate change, population growth, and soil threats. In this paper, we give examples of biophysical interactions that occur across various temporal and spatial scales and discuss how connectivity can be useful for bridging disciplines and scales to increase our understanding