Search

Pesticides have contributed significantly to increases in food production over the last few decades. In the European Union (EU), nearly 500 active substances have been approved for use as pesticides. The EU has one of the highest pesticide use in the world, with 374 000 tons being sold annually. Around 90% of pesticide sales can be linked to the agricultural sector. The pesticides used in agriculture, also known as Plant Protection Products (PPP), are applied to soil to prevent or combat the growth of undesired plants that compete with crops for resources, or to crops to combat organisms that can cause damage and reduce crop yields. There are several benefits associated with pesticides, the main ones relate to increasing yields, improving food security, and positively impacting the regional and national economies. On the other hand, intensive and widespread use of pesticides raises serious environmental and human health concerns. This is because substantial amounts of the pesticides applied in agriculture are released into the environment during or after application, and several pesticides (and/or their degradation products) are toxic to non-target-species, persistent in the environment, and accumulate through food chains. The high frequency of reports, increased diversity, and severity of negative effects of some pesticides raise serious concerns about the protection level of the current pesticide regulatory systems. The EU has the strictest system in the world but even it has shortcomings. The main problems relate to the low representativity of pre-approval risk assessments, the effective applicability of precautionary principles, and the limited post-approval monitoring of pesticide risks.Chapter 2 focuses on the limited post-approval monitoring data point, more specifically in soil, a compartment where pesticide data is particularly scarce and fragmented. We analysed the occurrence and levels of 76 pesticide residues in 317 agricultural topsoil samples from the

In the 1960s, the agricultural “Green Revolution” brough new technologies and heavy mechanisation to the fields. These technologies brought rapid answers to increase the crop yields and improve food security. Among these technologies we found pesticide and plastic mulch applications. Since then the scientific community and the general public became worried of the long term consequences of these short term solutions. Indeed plastic mulch and pesticides leave debris which accumulate in the soil and are potentially harmful to divers organisms. With this PhD thesis we try to encompass the threat posed by plastic mulch and pesticide residues in agriculture. The research was organised in seven different chapters described below.Chapter 1: In introduction we presented the diverse benefices of pesticide and plastic use in agriculture. The many services they provide explained why they are use abundantly worldwide. However both plastic and pesticides have the potential to accumulate in the soil. We narrowed down the focus to plastic mulch as it is used abundantly worldwide and is recognize as an important source of plastic debris. We presented three different plastic types: Low density Polyethylene (LDPE), Pro-oxidant Additive Containing (PAC) and biodegradable (BIO) mulches. Finally, we presented the threats posed by plastic and pesticide residues and the need for more research. We elaborated six main questions that are addressed in the following five research chapters.Chapter 2: The objective of this field assessment was to measure plastic and pesticide residues in agricultural soils and their effects on the soil microbiome. For this, we sampled soil from 18 parcels from 6 vegetable farms in Southeast Spain. The farms were under either organic or conventional management, where plastic mulch had been used for > 25 years. We measured the macro and micro light density plastic debris content, the pesticide residue levels, and a range of physiochemical properties. We also carrie

Plastic debris originating from mulching films has made a significant contribution to agricultural microplastic pollution.  However, the accumulation of plastic residues and the occurrence of microplastics in agricultural fields are missing. Biodegradable were introduced to agricultural systems due to its biodegradability. However, fully biodegradation under in-situ conditions have rarely been observed. Instead, biodegradable materials tend to break down into small bio-plastic fragments and microplastics. Worryingly, the ecological effects of LDPE and biodegradable microplastics in soil-plant systems remains largely unknown. For this reason, this PhD thesis aims to fill some knowledge gaps concerning the effects of plastic mulching and microplastic pollution on terrestrial ecosystems. To achieve this, a field observation, and a net house mesocosm experiment were carried out.In Chapter 2, a field observation was conducted in Northwestern China. We selected two regions with a long history of plastic mulching use but with two different farming systems. The first study region (S1) was characterized by small scale farmlands and low intensity machinery use. The second study region (S2) was characterized by large scale farmlands and high intensity machinery use. Plastic residues were collected from the top 0-30 cm of soil. Our results showed that in S1, fields with 6-8 years continuous plastic mulching accumulated significantly higher amounts of macroplastics than fields with 30 years intermittent plastic mulching. In S1, macroplastics in the 10–50 cm2 size category accounted for over 40% of the collected macroplastics, followed by macroplastics from 2–10 cm2 which accounted for over 30%. In S2, the collected macroplastics were mainly from the size category 0.25–2 cm2 (40.6%) and 2–10 cm2 (41.1%). Comparing the two study regions, macroplastics were more fragmented in S2 than in S1. This result was in line with the occurrence of microplastics in the two study regions.

Plastics serve as versatile and malleable matrices that manufactures can easily manipulate in an effort to develop new technologies to benefit society. These new technologies allow manufacturers to produce products that customers can use either a single time or for more than 50 years. Due to its great versatility, industries across all sectors use plastic at some point during the production process or include plastic in the final products. This great versatility comes with a high demand and use of plastic. This produces a complex scenario with regards to plastic disposal. According to the best educated guess, nearly 24 million tonnes of plastics that were improperly disposed of ended up in terrestrial ecosystems in 2010 alone. Since then, human demand for plastics and plastic consumption have steadily risen and increased to roughly 4 times what they were in 2010 (they reached 51.2 million tonnes in 2018). The implication reads: pollution and the transfer of plastics to ecosystems have worsened over the last 10 years.Large plastic chunks threaten the environment mainly through direct ingestion by wildlife. Smaller plastics measuring less than 0.5cm threaten the environment not only by their inherent toxicity but also by transporting other pollutants as they themselves move through the soil to other sites. Scientists named these smaller plastic pieces microplastics. Because microplastics constitute a potential threat to soil biota and water or wind might spread them through the environment by transporting them off-site, researchers have finally started to study the occurrence of microplastics in soils. Although researchers have gathered evidence on the occurrence of microplastics in soils as well as the effects that high concentrations might have on soil biota, a few methodological problems have hampered the proposal of new mitigation measures.To date, researchers have failed to articulate and standardize a reliable soil test to identify different plastic polymers and

My PhD thesis evaluates chemical pesticides that are used in agriculture to protect crops from pests and diseases. The thesis presents a perspective of pesticide use among Nepalese farmers and pesticide retailers. Furthermore, the thesis identifies pesticide residues in Nepalese vegetables and their soils and assesses health and environmental risk.A study was carried out in the Gaidahawa Rural Municipality of Rupandehi district, Nepal. The objectives were (i) to estimate pesticide use in vegetables and identify the factors affecting the safety behaviour of farmers and pesticide retailers on pesticide use and handling; (ii) to assess the dietary risk to humans from pesticides in vegetable crops that were exposed to the highest doses of pesticides in the field; (iii) to identify the human health risks from non-dietary intake of pesticides present in agricultural soils; and (iv) to investigate the ecological risk of pesticides detected in soils from both IPM and conventional fields. The objectives have been addressed in four separate interconnected studies in Chapters 2-5.Chapter 2 of this thesis aimed to examine pesticide use in a rural area of Nepal. We looked at pesticide use on vegetable crops and identified factors affecting the safety behaviour of farmers and pesticide retailers. Farmers perceived that pesticides posed low threats to humans and ecosystems. Due to the perceived lower threats from pesticides, farmers perceived that the use of personal protective equipment (PPE) had low benefits and high barriers such as unavailability and discomfort while using. Likewise, for retailers, perceived threat and cues to action affected their safety behaviour. Farmers applied the highest amount of organophosphate insecticides and carbamate fungicides on eggplants, chillies and tomatoes. The illegal import of chemical pesticides (including banned pesticides) in and around the border areas in Nepal is running rampant. Most farmers perceived pesticides as a “medicine” and n

Current farm systems rely on the use of Plant Protection Products (PPP) to secure high productivity and control threats to the quality of the crops. However, PPP use may have considerable impacts on human health and the environment. A study protocol is presented aiming to determine the occurrence and levels of PPP residues in plants (crops), animals (livestock), humans and other non-target species (ecosystem representatives) for exposure modelling and impact assessment. To achieve this, we designed a cross-sectional study to compare conventional and organic farm systems across Europe. Environmental and biological samples were/are being/will be collected during the 2021 growing season, at 10 case study sites in Europe covering a range of climate zones and crops. An additional study site in Argentina will inform the impact of PPP use on growing soybean which is an important European protein-source in animal feed. We will study the impact of PPP mixtures using an integrated risk assessment methodology. The fate of PPP in environmental media (soil, water and air) and in the homes of farmers will be monitored. This will be complemented by biomonitoring to estimate PPP uptake by humans and farm animals (cow, goat, sheep and chicken), and by collection of samples from non-target species (earthworms, fish, aquatic and terrestrial macroinvertebrates, bats, and farm cats). We will use data on PPP residues in environmental and biological matrices to estimate exposures by modelling. These exposure estimates together with health and toxicity data will be used to predict the impact of PPP use on environment, plant, animal and human health. The outcome of this study will then be integrated with socio-economic information leading to an overall assessment used to identify transition pathways towards more sustainable plant protection and inform decision makers, practitioners and other stakeholders regarding farming practices and land use policy.

The herbicide glyphosate interferes with the shikimate pathway in plants and in major groups of microorganisms impeding the production of aromatic amino acids. Glyphosate application on plants results in a slow death, accelerated by reduced resistance to root pathogens. Extensive glyphosate use has resulted in increasing residues in soil and waterways. Although direct glyphosate effects on animals are limited, major concerns have arisen about indirect harmful side effects. In this paper, we focus on indirect effects of sublethal concentrations of glyphosate on plant, animal and human health due to shifts in microbial community compositions in successive habitats. Research results of glyphosate effects on microbial communities in soil, rhizosphere and animal guts have been contradictory due to the different integration levels studied. Most glyphosate studies have tested short-term treatment effects on microbial biomass or general community composition at higher taxonomic levels in soil, rhizosphere or animal intestinal tracts, and found little effect. More detailed studies showed reductions in specific genera or species as well as biological processes after glyphosate application. Plant growth promoting rhizobacteria and beneficial intestinal bacteria often are negatively affected, while pathogenic bacteria and fungi are enhanced. Such shifts in microbial community composition have been implicated in enhanced susceptibility of plants to Fusarium and Rhizoctonia, of birds and mammals to toxic Clostridium and Salmonella species, and of bees to Serratia and Deformed Wing Virus. In animals and humans, glyphosate exposure and concentrations in urine have been associated with intestinal diseases and neurological as well as endocrine problems, but cause-effect relationships need to be determined in more detail. Nevertheless, outbreaks of several animal and plant diseases have been related to glyphosate accumulation in the environment. Long-term glyphosate effects have been

Plastic residues could accumulate in soils as a consequence of using plastic mulching, which results in a serious environmental concern for agroecosystems. As an alternative, biodegradable plastic films stand as promising products to minimize plastic debris accumulation and reduce soil pollution. However, the effects of residues from traditional and biodegradable plastic films on the soil-plant system are not well studied. In this study, we used a controlled pot experiment to investigate the effects of macro- and micro- sized residues of low-density polyethylene and biodegradable plastic mulch films on the rhizosphere bacterial communities, rhizosphere volatile profiles and soil chemical properties. Interestingly, we identified significant effects of biodegradable plastic residues on the rhizosphere bacterial communities and on the blend of volatiles emitted in the rhizosphere. For example, in treatments with biodegradable plastics, bacteria genera like Bacillus and Variovorax were present in higher relative abundances and volatile compounds like dodecanal were exclusively produced in treatment with biodegradable microplastics. Furthermore, significant differences in soil pH, electrical conductivity and C:N ratio were observed across treatments. Our study provides evidence for both biotic and abiotic impacts of plastic residues on the soil-plant system, suggesting the urgent need for more research examining their environmental impacts on agroecosystems.

Due to the widely use of plastic mulch in agriculture, plastic residues in the soil are threatening soil quality. In this thesis, we assessed the effects of macro and micro sized plastic residues from polyethylene and biodegradable plastic mulch films on the soil-plant system, by investigating their effects on plant growth, rhizosphere microflora, soil physicochemical properties and soil functions.Overall, this thesis provided experimental evidence that plastic mulch film residues affected physical, chemical and biological processes in the soil-plant system. Despite the lack of knowledge, it is clear with the incipient evidence that both macroplastics and microplastics derived from LDPE and biodegradable plastic mulch films could be detrimental to agricultural productivity, soil biodiversity and soil biogeochemical cycles. Moreover, the insights developed during this PhD research are a valuable contribution to a framework for the systematic analysis of the effects of microplastics on the soil-plant system and a holistic approach to study interrelated physical, chemical and biological processes in the agroecosystem.

Floods are considered to be one of the most destructive natural hazards on Earth. Apart from precipitation as the main driving factor for flood occurrence, there is increased recognition that human activities also largely influence the occurrence and impacts of floods. The Wei River Basin in China has suffered from floods for decades due to its monsoon climate with intensive summer rainfall. With the rapid development of the economy and population growth, land use and the water cycle have been altered due to the demands for resources redistribution. Consequently, the Wei River Basis is under pressure from both climate and anthropogenic changes. This thesis aims to bring a comprehensive understanding of the factors causing flood occurrence in the basin and propose an integrated management tool for flood analysis under the complex environment in the Wei River Basin. Chapter 1 describes the general factors and processes leading to flood occurrence with respect to meteorological, biophysical and anthropogenic aspects. Chapter 2 starts with the introduction of a framework approach for understanding these factors and their importance regarding contribution to flood occurrence in the Wei River Basin, and then presents the results of our application of this approach. The framework approach uses a set of methods to answer the questions why, where, when, and how flooding occurs and includes Conditional Inference Tree (CIT), cross correlation and double mass curves analyses. The results revealed that the dam construction period was the most important factor (why), and the Western upstream regions of the Wei River contributed the most to the flooding of the downstream floodplain (where). The effect of the periods of dam construction on the time lag change (when) and the precipitation-discharge relationship (how) were also analysed by the cross-correlation analysis and double mass curves analysis, respectively. Being able to bring both numeric and non-numeric factors into the an

Plastic residues have become a serious environmental problem in the regions with intensive use of plastic mulching. Even though plastic mulch is widely used, the effects of macro- and micro- plastic residues on the soil-plant system and the agroecosystem are largely unknown. In this study, low density polyethylene and one type of starch-based biodegradable plastic mulch film were selected and used as examples of macro- and micro- sized plastic residues. A pot experiment was performed in a climate chamber to determine what effect mixing 1% concentration of residues of these plastics with sandy soil would have on wheat growth in the presence and absence of earthworms. The results showed that macro- and micro- plastic residues affected both above-ground and below-ground parts of the wheat plant during both vegetative and reproductive growth. The type of plastic mulch films used had a strong effect on wheat growth with the biodegradable plastic mulch showing stronger negative effects as compared to polyethylene. The presence of earthworms had an overall positive effect on the wheat growth and chiefly alleviated the impairments made by plastic residues.

Low-density polyethylene (LDPE) is the most abundant source of microplastic pollution worldwide. A recent study found that LDPE decay was increased and the size of the plastic was decreased after passing through the gut of the earthworm Lumbricus terrestris (Oligochaeta). Here, we investigated the involvement of earthworm gut bacteria in the microplastic decay. The bacteria isolated from the earthworm's gut were Gram-positive, belonging to phylum Actinobacteria and Firmicutes. These bacteria were used in a short-term microcosm experiment performed with gamma-sterilized soil with or without LDPE microplastics (MP). We observed that the LDPE-MP particle size was significantly reduced in the presence of bacteria. In addition, the volatile profiles of the treatments were compared and clear differences were detected. Several volatile compounds such as octadecane, eicosane, docosane and tricosane were measured only in the treatments containing both bacteria and LDPE-MP, indicating that these long-chain alkanes are byproducts of bacterial LDPE-MP decay.

Glyphosate is the most used herbicide in agricultural lands worldwide, with more than 825 000 tons sold globally in 2014. Such great use is mostly a result of the introduction of glyphosate-resistant (GR) crops in 1996 by Monsanto company. Loess soils, on the other hand, are amongst the most productive and fertile soils and, consequently, are intensively used for agriculture and to grow GR crops. Consequently, they are heavily subject to the application of glyphosate-based herbicides every year. Despite being the most used pesticide worldwide, the environmental fate of glyphosate and its main metabolite aminomethylphosphonic acid (AMPA) is still not well understood. Therefore, this PhD thesis aims at better understanding the environmental fate of glyphosate and AMPA in the loess soil environment. Special focus is given to: 1) the decay kinetics of glyphosate and the formation and decay kinetics of AMPA; and 2) the off-site transport of glyphosate and AMPA associated to the particle-bound phase, as a result of wind and water erosion. These processes were studied under laboratory and field conditions. The field study was performed in agribusiness fields of the loess Pampas of Argentina. The results of this PhD thesis have shown that: 1) the decay of glyphosate and AMPA in loess soils is mostly a microbiological process and is fastest under warm and moist soil conditions and slowest under cold and dry soil conditions; 2) AMPA persists longer in loess soil than glyphosate, and tends to accumulate; 3) the type of decay kinetics followed by glyphosate in loess soils is mostly temperature dependent, but abrupt soil moisture changes from dry to moist also play a role; 4) glyphosate degradation into AMPA was extremely variable (5-100%) amongst different temperature conditions and between laboratory and field conditions; 5) glyphosate and AMPA contents are highest in eroded soil particles <10 µm (PM10) and, consequently, their long-range off-site transport risk with wind eros

Nanomaterials are materials with particle sizes ranging from 1 to 100 nm in at least one dimension and have properties that are different from their bulk material. Engineered nanomaterials (ENMs) are a promising field of study for science and engineering since it offers many prospects for new products. Silver nanoparticles (AgNPs) have the widest range of applications due to their antimicrobial, catalytic, optical, electronic and magnetic properties. The increasing production of AgNPs will, without a doubt, lead to the emission of these materials to the environment. AgNPs can enter the soil from different pathways. Their available concentration in soil is expected to be low which makes their detection beyond the ability of many current measuring techniques. Moreover, extracting AgNPs from soil samples is a troublesome process due to the difficulties posed by the soil matrix and the high adsorption affinity between soil particles and AgNPs. The possible risks and impacts of AgNPs on soils and plants have been confirmed by many studies. However, knowledge about the transport mechanisms of AgNPs through soil and over soil surfaces as a result of leaching, runoff and erosion is still limited. These soil processes can facilitate AgNP migration to deeper soil layers and downhill areas and to ground and surface water systems. This thesis presents results for AgNP detection in soil as well as measurements and modelling results of its fate and transport. In chapter 2, this thesis describes the development and validation of an extraction method for AgNP quantification and particle size determination in soil samples. The developed method is simple and fast thus reducing analysing time and costs. AgNPs recoveries were calculated by comparing AgNP concentration measured in the soil samples to the initial (spiked) AgNPs concentration. Two AgNP-spiking suspensions were prepared with concentrations of 0.5 and 5 (mg L-1) using commercially obtained 60 and 100 nm stock suspensions. T, Dit proefschrift presenteert resultaten van een nieuwe methode voor de detectie van AgNP’s in de bodem, evenals metingen van stromingsprocessen en modellering van het transport van AgNP’s (zilver nanodeeltjes) door en over de bodem.

The Government of Rwanda would like to improve farming livelihood through the sustainable production of high quality coffee. This would be a win-win situation because improving farming livelihoods also provides increased export earnings. In order to fulfil this, the Government of Rwanda needs to design and support policies which sustain this growth. This can be achieved through an improvement programme of soil fertility and reduction of soil erosion, among other strategies. The programme should identify suitable areas for Arabica coffee production and assess sustainable land management technologies to improve soil fertility and reduce soil erosion to create conditions for optimizing production of high quality coffee. This PhD project contributes to those objectives. Experimental field measurements were conducted to assess the effects of mulch application on improving soil properties and reducing soil erosion, thus positively impacting yields. Assessments were made for three agro-ecological zones of Rwanda, namely the highlands, the central plateau and the shores of Lake Kivu. The thesis covers a GIS Spatial analysis of coffee production systems at national level (chapters 2 and 3); at system and farm levels. It assessed the effects of best practices on soil erosion and soil fertility (chapters 4 and 5); and then it recommended best upscaling practices for a country level (chapters 3, 4, 5 and 6). Chapter 2 also reviewed coffee growing conditions, systems and soil management practices in Rwanda. Data showed that growing conditions are confined to an altitude range of 1,400 - 1,900 m a.s.l., an annual rainfall regime of 1,500 - 1,600 mm, a temperature class of 18 – 22 °C, and an average sunlight amount of 2,000 - 2,400 hours per year. Coffee is mainly grown along the shores of Lake Kivu, on the plateau in the central part of Rwanda, and in the Mayaga region located in the Southern-East part of the country. In these areas, coffee is mainly cultivated on moderate slopes

1.1 Why study wildfire? A massive wildfire ripped through a section of Portugal on Sunday, June 18, 2017 killing more than 60 people and injuring hundreds more (CNN.com). In addition to the tragic loss of life, the damage and impacts of this and other fires reach far beyond the obvious loss of vegetation. Every year, around 45,000 forest fires break out in southern Europe, burning around half a million hectares of forests (Moreira et al., 2011). In Portugal, between 1980 and 2010, an average of 110,000 hectares burned every year (Stoof et al., 2015; Giglio et al., 2010; FAO, 2007; Giglio et al., 2006). Fires in Portugal are often one of the major reasons contributing to forest disruption and renovation (Cerdà and Robichaud, 2009). Besides the obvious loss of forests and the socioeconomic consequences, fires can create smoke pollution, release greenhouse gases, and damage ecosystems (NASA). Fires can also increase surface temperatures and soil hydrophobicity as well as impact nutrient cycling (Richards et al. 2012). The increased frequency and severity of fires over the past few decades have considerable negative ecological consequences in terms of soil erosion, decreasing soil fertility (Stoof et al., 2015; Cerdà and Robichaud, 2009; Certini, 2005) and forest productivity. The effects of one single forest fire on runoff and soil erosion are well known, especially in terms of overland flow and soil loss until the vegetation recovers (Shakesby, 2011). However, the effects of repeated fires and their impacts on maritime pine plantations, which are widespread in Portugal, have received less attention (Malkisnon et al., 2011). Correct identification of the areas sensitive to fire, in addition to better knowledge and understanding of the impacts of wildfires on plant-water-soil interactions, and the application of proper restoration methods will help to better manage the effects of fires in order to decrease the susceptibility of these areas to repeated fires. Compared to

Approval for glyphosate-based herbicides in the European Union (EU) is under intense debate due to concern about their effects on the environment and human health. The occurrence of glyphosate residues in European water bodies is rather well documented whereas only few, fragmented and outdated information is available for European soils. We provide the first large-scale assessment of distribution (occurrence and concentrations) of glyphosate and its main metabolite aminomethylphosphonic acid (AMPA) in EU agricultural topsoils, and estimate their potential spreading by wind and water erosion. Glyphosate and/or AMPA were present in 45% of the topsoils collected, originating from eleven countries and six crop systems, with a maximum concentration of 2 mg kg− 1. Several glyphosate and AMPA hotspots were identified across the EU. Soil loss rates (obtained from recently derived European maps) were used to estimate the potential export of glyphosate and AMPA by wind and water erosion. The estimated exports, result of a conceptually simple model, clearly indicate that particulate transport can contribute to human and environmental exposure to herbicide residues. Residue threshold values in soils are urgently needed to define potential risks for soil health and off site effects related to export by wind and water erosion.

Sampling and analysis or visual examination of soil to assess its status and use potential is widely practiced from plot to national scales. However, the choice of relevant soil attributes and interpretation of measurements are not straightforward, because of the complexity and site-specificity of soils, legacy effects of previous land use, and trade-offs between ecosystem services. Here we review soil quality and related concepts, in terms of definition, assessment approaches, and indicator selection and interpretation. We identify the most frequently used soil quality indicators under agricultural land use. We find that explicit evaluation of soil quality with respect to specific soil threats, soil functions and ecosystem services has rarely been implemented, and few approaches provide clear interpretation schemes of measured indicator values. This limits their adoption by land managers as well as policy. We also consider novel indicators that address currently neglected though important soil properties and processes, and we list the crucial steps in the development of a soil quality assessment procedure that is scientifically sound and supports management and policy decisions that account for the multi-functionality of soil. This requires the involvement of the pertinent actors, stakeholders and end-users to a much larger degree than practiced to date.

The study was conducted in the semi-arid northern Ethiopia aimed at selecting appropriate water harvesting techniques (WHTs) for implementation. A plot-scale experiment was set up, in the Gule catchment, on a farmland to monitor the effect of in-situ WHTs such as tied ridges and straw mulch mainly on event-based runoff, soil-moisture, and soil and nutrient losses. The off-site effect of WHTs such as check dams and percolation ponds on catchment-scale event-based runoff and sediment yield was also monitored in the Gule catchment (~12 km2) and Misbar sub-catchment (~2.4 km2), northern Ethiopia. First, a decision support approach was developed to aid the selection of WHTs in arid and semi-arid areas. The decision support approach was validated with a case study for WHTs in the upper Geba watershed in northern Ethiopia. Using the decision support methodology, eight potential WHTs were pre-selected for implementation in the watershed. Next, using suitability indicators for WHTs and a GIS-based multi-criteria analysis, suitable areas were identified for three of these WHTs, namely check dams, percolation ponds and bench terraces and suitability maps were generated. The multi-criteria analysis was validated by comparing the predicted suitable areas with the already existing locations of WHTs in the watershed. The result was that 90% of the existing check dams and 93% of the percolation ponds in the upper Geba watershed were correctly identified by the approach. The field study showed runoff reduction by WHTs from farmland between 40 to 88% and soil loss between 60 to 90%. Nutrient loss reduction from farmland by WHTs also ranged between 52 and 86%. Soil-moisture also improved due to the use of the in-situ WHTs. Model-based simulation at the Gule and Misbar outlets using LISEM showed that the current WHTs applied in the catchment are able to decrease event-based runoff by 41 and 45%, respectively. Similarly, sediment yield was reduced at both the Gule outlet and Misbar sub

Land degradation, mainly due to soil erosion and nutrient losses, is a global problem for sustainable agriculture. Farmlands in the Ethiopianhighlands are susceptible to water erosion because of steep slopes and extensive cultivation. A field experiment was conducted in the Gulesub-watershed in northern Ethiopia to assess the efficacy of in situ water harvesting techniques in reducing soil and nutrient losses. Theresearch was carried out on a sandy clay loam soil under semi-arid conditions. Soil erosion and nutrient losses were monitored during therainy season (June to September) in 2013 and 2014. Five treatments with tied ridges, wheat-straw mulch and effective microorganisms, aloneor in combination, and an untreated control were tested. Combined tied ridges and straw mulch, with and without effective microorganisms,significantly reduced average soil loss over the two rainy seasons by 82 and 90% respectively compared with the control. Tied ridges alonereduced average soil loss by 60%. Straw mulch with and without effective microorganisms decreased average soil loss by 81 and 85%respectively. Combined tied ridges and straw mulch significantly decreased average total nitrogen and total phosphorus losses by 82 and83% respectively. Average nutrient losses were also significantly decreased by tied ridges (59% for nitrogen, 52% for phosphorus) and strawmulch (63% for nitrogen, 68% for phosphorus). Our results indicated that in situ water harvesting techniques can effectively reduce soil andnutrient losses from farmland and were more efficient when the techniques were combined