Financial cost–benefit analysis of bench terraces in Rwanda

Bench terracing has received considerable attention from soil and water conservation (SWC) programmes involved in soil erosion control in Rwanda. It is questioned, however, whether enough attention is paid to the suitability of the soils and to the eventual financial profitability. Terraces may reduce soil erosion and increase production but they should also provide sufficient financial gains at farm level. A plot level financial cost–benefit analysis was undertaken to examine under which social and economic conditions bench terraces are financially viable in Northern and Southern Rwanda. Farmers' estimates of respective costs and potato yields from plots with subsidized and un‐subsidized bench terraces, progressive terraces and plots with no terraces at all were obtained for the analysis. Costs of labour and manure were found to be the most influential for the profitability of bench and progressive terraces. While the cost–benefit analysis, using market prices, showed that bench terraces would be hardly profitable, an analysis with opportunity costs for labour and manure indicated that bench terraces and even more progressive terraces can be financially profitable. Extra measures and incentives may be required to facilitate use of labour and access to manure, as now achieved with the one cow per family policy. This paper suggests that further studies should be undertaken to determine costs and benefits of bench terraces beyond private perspective in Rwanda. Copyright © 2010 John Wiley & Sons, Ltd.     

Cost‐benefit analysis of bench terraces,a case study in Peru

Soil and water conservation measures like bench terraces can reduce erosion in highland crop production. A cost‐benefit analysis for 11 cases of bench terraces was undertaken on the basis of both measured data and data obtained from farmers. It showed that the profitability of bench terraces was lower than believed by farmers. Whether terracing was financially attractive to a farmer, depended on his personal opportunity cost of labour. For most farmers an opportunity cost of labour below the market wage could be justified, as they had only temporarily off‐farm work. Considering these opportunity costs, the labour input in bench terracing was in most cases worthwhile. The costs and benefits of bench terraces were both much higher than the value of external project incentives. The incentives barely influenced the profitability of the bench terraces. Copyright © 2004 John Wiley & Sons, Ltd.     

Participatory soil and water conservation planning using an erosion mapping tool in the central highlands of Kenya

Despite several approaches that aimed at mobilising East African farmers to embrace soil and water conservation (SWC) activities, farmers hardly responded since they were seldom involved in the planning of SWC activities. Two tools that employ farmers' participation were developed and applied at Gikuuri catchment in Kenya. The first tool involved farmers to map soil erosion using their own indicators and determine the soil erosion status at catchment scale. This formed the basis upon which they undertook to plan for SWC measures at catchment scale. Farmers also predicted crop yield losses based on the soil erosion status. Farmers widely approved the soil erosion status map since their own indicators and perceptions were used. The second tool provided cash flow trends for a variety of SWC activities and farmer situations. Farmers can use land with a high, moderate or low erosion status and often have rather different socio‐economic settings. The net benefits over 5 yr for bench terraces, fanya juu terraces and grass strips were illustrated to assist farmers in making informed decisions on SWC adoption. The two tools increased awareness on the need for collective actions among farmers and showed fields that cause run‐on on downslope fields. The improved awareness of erosion problems and the related financial consequences increased farmers' willingness to share the investment costs for cut‐off drains. Copyright © 2007 John Wiley & Sons, Ltd.     

Soil erosion and participatory remediation strategy for bench terraces in northern Thailand

This study was carried out in Pang Prarachatan village, which is located in Chiang Rai province of northern Thailand. The farmers in this village construct bench terraces to reduce soil erosion and increase plant productivity. However, severe soil erosion occurs frequently on the bare bench terraces. This study investigates the impact of bench terracing on soil erosion. The use of weeds and plant residues to control soil and nutrient losses were also investigated using model slope plots and an artificial rainfall system. Finally, the knowledge gained from this study was transferred to the farmers through a workshop in the village, and their acceptance of the results was evaluated by means of a questionnaire. The severity of soil erosion is thought to vary according to the structure of the bench terrace and the ground cover conditions. Rills are the primary form of erosion on bare bench terraces. In addition, some rills develop into gullies that can run from the upper terrace down to the lower terrace. Nevertheless, rills and gullies are rarely found on weed-covered terraces. Moreover, the results of an erosion experiment using model slope plots and artificial rainfall systems showed that plots covered with weeds and plant residues had much less surface runoff and soil and nutrient losses than bare soil. The amounts of nitrogen and phosphorus absorbed by weeds were 4.7 and 2.3 times smaller than the nitrogen and phosphorus losses due to soil erosion, respectively. The results of the field surveys and model slope experiment were announced to the farmers through participatory workshop in August 2003. The first questionnaire, conducted just after the workshop, clearly showed that around 90% of the farmers agreed to cover their slopes with weeds and plant residues so long as it did not affect soil fertility and plant growth. However, the second questionnaire, conducted in January 2004, showed that only 29% of farmers were covering the bench terraces or non-terraced slopes in their farmlands with weeds and plant residues. Therefore, participatory activities should continue to be held regularly in order to ensure greater acceptance and practice of soil conservation on the part of the farmers.     

Parameterization of the Effect of Bench Terraces on Runoff and Sediment Yield by Swat Modeling in a Small Semi‐arid Watershed in Northern Tunisia

In Tunisia, soil and water conservation interventions are among the most practicable strategies to prevent and mitigate rainwater losses through surface runoff and consequential erosion of fertile soils. In this study, a small and terraced agricultural catchment (Sbaihia) was used as an experimental site to analyze and parameterize the effects of bench terraces on water and sediment yield using the Soil and Water Assessment Tool. Model calibration and validation was performed, taking advantage from high‐quality daily runoff data from 1994 to 2000 and a high‐resolution bathymetric survey of the hill lake at the watershed outlet. Soil and Water Assessment Tool indicated that the local terraces, established on approximately 50% of the watershed area, reduced surface runoff by around 19% and sediment yield by around 22%, decelerating the siltation of the hill lake. Targeted model calibration delivered concise parameter set describing bench terrace impacts on runoff (Soil Conservation Service curve number method) and sediment yield (Modified Universal Soil Loss Equation) crucial for outscaling of soil and water conservation impacts and suitable watershed management. Copyright © 2016 John Wiley & Sons, Ltd.     

广东北江第四纪沉积物发育土壤的矿物特性

本文分析了粤北武水、北江、横石水和连江各级阶地及河漫滩上各时代沉积物发育土壤的粘粒矿物和原生矿物。结果表明,不同河流流经地区不同,物质来源不同,其矿物组成有别;同一河段,形成于早更新世的三级阶地(T₃)上的土壤矿物组成与形成较晚的各级阶地差异甚大,这是母质来源和风化成土条件不同所致;二级阶地(T₂)、一级阶地(T₁)及河漫滩(T₀)上的土壤矿物相似,只是风化程度有异,随着阶地升高,形成年代愈老,富铝化程度愈强烈;但各级阶地之间差异程度不均等,T₂至T₁之间变幅大,T₁至T₀之间差异较少,这是时间因素和古气候波动性叠加所致。     

Nutrient losses from rain‐fed bench terraced cultivation systems in high rainfall areas of the mid‐hills of Nepal

Between the elevations of 1000 and 2000 m in the mid‐hills of Nepal, over 12 million people subsist on land‐holdings of less than 0·5 ha. These farmers have limited access to commercial inputs such as fertilisers and are reliant on organic manures for soil fertility maintenance. Participatory research was conducted with farmers on bari land (upper slope rain‐fed crop terraces) in the hill community of Landruk (bench terraces 0–5° slope, 3000–3500 mm annual rainfall, which aimed to develop soil and water management interventions that controlled erosion without resulting in high leaching, and so were effective in minimising total nutrient losses. Interventions tested were the control of water movement through diversion of run‐on and planting fodder grasses on terrace risers on bench terraces. The interventions were effective in reducing soil loss from the bari land in comparison with existing farmer practices, but no effect was observed on nutrient losses in solution form through runoff and leaching. Losses of NO₃‐N in leachate ranged from 17·3 to 99·7 kg ha⁻¹ yr⁻¹, but only 0·7 to 5·6 kg ha⁻¹ yr⁻¹ in runoff. The overall nutrient balance suggests that the system is not sustainable. Fertility is heavily dependent on livestock inputs and if the current trends of declining livestock numbers due to labour constraints continue, further losses in productivity can be expected. However, farmers are interested in interventions that tie ecosystem services with productivity enhancement and farmers' priorities should be used as entry points for promoting interventions that are system compatible and harness niche opportunities. Copyright © 2007 John Wiley & Sons, Ltd.     

Determinants for adoption of physical soil and water conservation measures by smallholder farmers in Ethiopia

Adoption rates of soil and water conservation measures remain below the expected levels in Ethiopia despite the considerable investments in reducing land degradation and improving soil fertility. This constitutes one of the key research agendas in the country. This paper underscores the need for investigating the factors hindering or facilitating the adoption of soil and water conservation measures. The study results presented in this paper are based on cross-section data collected from 408 households in eastern Ethiopia, including field observations of 790 plots selected using a multi-stage sampling procedure. A multivariate probit model was employed to analyse the determinants of adoption of three soil and water conservation measures (stone bund, soil bund, and bench terracing) at the plot level. The study findings reveal that household, socioeconomic, and institution characteristics were the key factors that influenced the adoption of soil bund, stone bund, and bench terracing conservation measures. Furthermore, there was a significant correlation among the three soil and water conservation measures, indicating that the adoption of these measures is interrelated. In particular, the results show that there was a positive correlation between stone bunds and soil bunds. However, the correlations between bench terracing and stone bunds as well as bench terracing and soil bunds were negative (implying substitutability). These results imply that the Government and other relevant organizations that are responsible for reducing land degradation in order to increase agricultural production should support the establishment and strengthening of local institutions to facilitate the adoption of soil and water conservation measures.     

More people,more erosion? Land use,soil erosion and soil productivity in Murang'a district,Kenya

Intensification of land use can become a threat to agricultural sustainability if they lead to increased soil erosion. This study examines land‐use changes, soil and water conservation, soil erosion and soil productivity in the Highlands of Kenya. In addition, it examines farmers' perception of livelihood changes. Land‐use changes were determined from interpretations of aerial photographs taken in 1960 and 1996. Additional information on land use, soil and water conservation and livelihood changes were obtained from discussions and interviews with farmers, as well as from field verifications of the most recent aerial photographs. Soil samples were analysed and soil erosion assessed according to the PLUS classification scheme. The results indicate that substantial changes in land use, such as introduction of coffee and high‐yielding maize, and fragmentation of land holdings have taken place. Less land was conserved in 1996 as compared to 1960. Moreover, SWC practices have changed from fanya chini terraces and shifting cultivation to bench terraces and permanent cultivation. Rates of soil nutrients (organic C, N and K) and maize‐yield levels decreased significantly with increasing erosion. Farmers' perception of livelihood changes was differentiated according to farmers' off‐farm resource 60 per cent of the farmers depended on income from the land and thought livelihoods were better in the 1960s. It is concluded that more efforts to decrease soil erosion and investments in land and labour are necessary to sustain soil productivity and hence secure rural livelihoods. Copyright © 2000 John Wiley & Sons, Ltd.     

Phosphorus removal from secondary-treated wastewater using overland flow

The removal of total phosphorus from secondary effluent by overland flow was studied using five terraces constructed 91 m in length and 140 or 70 m in width. Three methods of wastewater application were tested on the terraces including sprinkler, fan nozzle, and gated pipe. In addition, three different application rates were used. Samples of applied wastewater, runoff collected at points along the terraces, effluent from each terrace, and soils were analyzed for total phosphorus over a ten-month period. Hydraulic application rate had a significant effect on the removal of total phosphorus; the removal efficiency was inversely proportional to the hydraulic application rate. However, the method of application did not have an effect on phosphorus removal. An increase in phosphorus was observed in terrace soil samples; the increase was attributed to adsorption and precipitation.     

不同代际传递方式对稻农有机肥施用意愿的影响

在我国以“家庭关系”为核心的传统农耕文化大背景下,稻农对有机肥的施用意愿是否受家庭内部代际传递因素的影响?既有研究尚未给出相应的证据。鉴于此,利用在湖北省实地调查获得的563份有效微观数据,运用二元Logistic模型,重点分析了互动性代际传递与示范性代际传递对稻农有机肥施用意愿的影响。研究发现：1）样本农户中,52.93%的稻农愿意施用有机肥;2）互动性传递程度每提升1个层次,稻农愿意施用有机肥的概率会下降10.10%,而示范型传递程度每提升1个层次,稻农愿意施用有机肥的概率会提升20.64%;同时,示范性传递对稻农有机肥施用意愿的影响会随互动性传递影响程度的下降而显著增强;3）互动性传递、示范型传递及其交互项是影响中青年组稻农对有机肥施用意愿的重要因子,而老年组稻农对有机肥的施用意愿主要受交互项的影响;4）稻农对有机肥的施用意愿还受土壤肥力、教育水平、农业年收入、风险感知、政策满意度的影响。因此,要正确引导父代采用相关绿色农业技术的正向示范效应,弱化父代务农经验对稻农的消极影响;适当加大教育投入,发展低风险绿色农业技术,充分发挥政府在技术支持中的引领作用,进而促进有机肥等绿色农业技术的推广应用。     

梯田蓄水效益估算方法探讨

[目的]综合考虑梯田土壤性质、梯田形态及降雨雨型的差异,构建梯田蓄水保水效益的估算方法及框架。[方法]运用土壤水库计算模型与入渗模型,探讨蓄满产流和超渗产流模式下梯田土壤水分的预测方法;基于Richards方程,分析不同田坎边界的土壤水分入渗二维分异。在此基础上,进一步对前峰型、均匀型、后峰型、阶梯型4种降雨雨型下产生的单一产流模式或2种产流模式均存在时土壤水分运动进行情景分析。[结果](1)提出梯田蓄水效益分布式估算方法,计算单个梯田田块土壤最大蓄水容量(W_M);(2)对不同田坎类型的梯田而言,浆砌石坎梯田防侧渗效果最好,土坎梯田防侧渗效果最差,且孔隙大、密度小、修筑时间短的新土坎梯田比修筑时间长的土坎梯田在发生侧渗时损失水分更多;(3)得出不同雨型下蓄满产流的临界时间(t)。[结论]该估算方法可大幅度降低对野外设施、设备的依赖程度,降低投入成本,借助野外调查采样,基于模型模拟估算梯田蓄水效益。此外,该方法可根据单个梯田田块蓄水效益分布式计算数据,在区域尺度上估算梯田蓄水保水效益,以期为不同区域梯田的蓄水效益估算提供参考。     

梯田地形形态特征及其综合数字分类研究

梯田地形具有独特的平面和剖面形态特征,而现有梯田地形分类无法准确反映梯田地形的平面形态特征,导致其难以满足未来构建梯田地形数值模拟模型的需求.以黄土高原旱梯田地形为切入点,对梯田地形的总体特征、平面和剖面形态特征及几何量测特征进行深入研究,提出了基于梯田平面形态特征的梯田地形分类,并在结合现有梯田地形分类的基础上,构建出梯田地形综合数字分类.与传统梯田地形分类相比,该分类综合考虑梯田的总体特征和平面及剖面形态,能更好地反映梯田独特的形态特征和几何量测特征.研究结果为未来构建梯田地形数值模拟模型奠定了坚实基础,对于探讨利用DEM实现梯田地形的有效数字表达与分析具有重要理论意义.     

RUNOFF AND SEDIMENT FROM ORCHARD TERRACES IN SOUTHEASTERN CHINA

The severity of soil erosion is considered to vary according to the structure of the bench terrace and the ground cover conditions. Erosion losses were investigated in a field experiment based on 20 m × 5 m erosion plots on a 21 per cent slope in Southern China. Five plots were established for the present study. Rainfall, runoff and sediment yield from plots were recorded for 5 years (2001–2005) and which five different types of terraces on sloping red soil were compared. The results show that the planting of grass on the riser is the most important factor affecting runoff and sediment yield, the next most important factor was the construction of a bund built on the edge of the terrace. Although the terrace bed slope (slope < 5 degrees) does not significantly affect the runoff, it does benefit the soil. A terrace combined with vegetation measures is effective in controlling runoff and soil erosion. Among various terraces, the level terrace (i.e. grass planted on the riser and bunds built on the edge of a bench terrace) is apparently the most beneficial for soil conservation purposes, indicating that this type is an excellent choice for conserving soil and water resources in sloping red soil in Southeastern China. Copyright © 2012 John Wiley & Sons, Ltd.     

Impacts of farmland size and benefit expectations on the utilization of straw resources: Evidence from crop straw incorporation in China

Promoting the technique of crop straw incorporation holds great significance for soil fertility and the green development of agriculture, and the participation of farmers is crucial for the adoption of this technique. Crop straw incorporation has been carried out and promoted in China for more than 30 years, but the adoption rate among farmers remains relatively low. Based on micro survey data on farmers in Jiangsu Province, China, this study quantitatively examines the effects of farmland size and benefit expectations on farmers' willingness to incorporate crop straw (hereinafter referred to as FWIS) by using an ordered logit (ologit) model. The results show that there are significant differences in the willingness to incorporate crop straw among farmers with different farmland sizes; farmers with larger farmland sizes are less willing to adopt crop straw incorporation than those with small-scale farmland. Benefit expectations significantly affect FWIS. Yield expectations are the key factor in improving FWIS. Cost and soil quality expectations are also important factors that affect FWIS. Plot size affects FWIS more than farmland size. A larger plot size is associated with stronger FWIS. To improve farmers' expectations of crop straw incorporation, the government should increase the use of micro-incentive policies for farmers and enterprises that provide social services for crop straw incorporation. Promoting the circulation and integration of adjacent farmland, appropriately expanding plot size and reducing the cost of crop straw incorporation will help promote FWIS.     

The interaction of volcanic activity in quaternary times upon the evolution of the Alcantara and Simeto rivers, Mount Etna, Sicily

The interaction between volcanic and alluvial sequences is described for the Alcantara and Simeto Valleys, Mount Etna, Sicily. This study provides valuable information on the stratigraphy for prehistoric lavas exposed on the lower western flanks of the volcano. Eight orders of terrace are recognised in the Simeto Valley. The Basal Tholeiitic Volcanics, the oldest exposed lavas of Etna, are associated with Terrace 7 of the Simeto which is correlated with either the pre-Rianian (Nomentanan erosive phase), or the early Rianian Stage of the Pleistocene. The earliest evidence of Trachybasaltic volcanism in the Simeto catchment occurs in Terrace 4 which is considered to be of Late Maspinian age. The oldest known volcanics in the north western part of the volcano are related to Terrace 3 which is dated at around 20000 BP. The alluvial deposits of these terraces provide a valuable sequence of Italian Quaternary sediments dating back over the last 300000 years. The nature of these deposits is described and the probable conditions of their deposition considered. The terraces in the upper part of the Alcantara are quite different in their mode of formation from the lava-capped cut and fill terraces of the Simeto Valley. The current upper course of the Alcantara River is considered to be quite youthful (Versilian) in age and the terraces are bench features formed as the river cut down through the lava sequence.     

Soil and phosphorus redistribution along a steep tea plantation in the Feitsui reservoir catchment of northern Taiwan

Abstract

Feitsui reservoir, the major water supply of Taipei city, has shown declining water quality in recent years. The reservoir is located in an area famous for tea cultivation, and the question arises as to whether the hillside tea plantations have contributed to increased sediment and nutrient discharge into the reservoir. In this study, soil and phosphorus redistribution were examined along a steep tea plantation in the reservoir's catchment and the provenance of reservoir sediment was assessed. Fallout radionuclides were used as soil erosion/deposition tracers and as markers of sediment sources. Continuous fertilizer application has raised (inorganic) phosphorus levels in the studied tea plantation. The plantation's narrow bench terraces trap eroded material and slow down soil and nutrient translocation. Nevertheless, eroded soil and phosphorus have accumulated on a vegetated toeslope below the tea plantation. The reservoir sediment contained significant amounts of inorganic phosphorus and cesium-137, and application of a mixing model resulted in a surface soil contribution of approximately 30%. This points towards tea plantations as possible sediment and pollutant sources and underlines the necessity of soil conservation strategies, such as the maintenance of vegetated riparian buffer zones. However, other sources, such as landslide debris and urban wastewaters, cannot be entirely ruled out. Further research is needed to better characterize the catchment's soils and sediments and to improve sediment fingerprinting efforts. Potential point and non-point pollution sources need to be examined in detail to better understand how phosphorus enters the reservoir.     

Behaviour of smallholder farmers towards adoption of conservation agriculture in Zimbabwe

Conservation agriculture is critical to sustainably increasing agricultural productivity, enhancing climate resilience and food security. Much research on adoption of conservation agriculture has focused on its agronomic benefits, but little attention has been paid to the contribution of the behaviour of farmers over its adoption. To close this gap, a study was carried out to investigate the behaviour of smallholder farmers towards the adoption of conservation agriculture in Chivi, Murehwa and Mutoko districts, Zimbabwe. Data were collected through a pre‐tested questionnaire administered to 360 farmers, selected through a multi‐stage sampling process. This method was triangulated through focus group discussions, key informant interviews and personal observations. Data were analysed using percentages, means and inferential statistics. The results show that, although fewer than 10% of the respondents had received any formal training in agriculture, more than 80% of them relied on it for their major source of income. The respondents had high levels of knowledge on the social, environmental and economic benefits of conservation agriculture. However, the majority of the non‐adopters had an indifferent perception towards conservation agriculture. The knowledge and perception of the farmers was explained by age, gender, education and experience with conservation agriculture. Results also show a weak but significant correlation between knowledge and perception (R_s = 0.306, p < 0.05), knowledge and adoption (R_s = 0.484, p < 0.05) but a strong and significant correlation between perception and adoption (R_s = 0.808, p < 0.05). Addressing perception gaps is key to enhance adoption of conservation agriculture.     

FARMERS' KNOWLEDGE AND PERCEPTION OF AGRICULTURAL WETLAND MANAGEMENT IN RWANDA

Most of Rwanda's wetlands are being reclaimed under government schemes with the aim of growing rice as the main crop. In the present study, information on farmers' knowledge and perceptions of agricultural wetland management was collected in Cyabayaga and Rugeramigozi wetlands. The two wetlands were selected as representatives for typical reclaimed wetland agriculture in Rwanda. They provide contrasts in both environmental and social terms. Three tools were used to investigate farmers' knowledge and perception of agricultural wetland management: (i) household survey; (ii) focus group discussions; and (iii) transect walk. The major constraints identified by farmers in the two wetlands were water shortage and lack of availability of improved seeds and high prices of fertilisers. The primary benefits from wetlands for farmers are income generation in Cyabayaga and food security in Rugeramigozi. The most commonly reported concern about the wetlands in the Cyabayaga and Rugerameragozi was that they are a source of malaria. Rice is an important crop in both wetlands, whereas farmers in Cyabahaga wish to continue cultivating rice, Rugeramigozi farmers prefer to grow rice only after it has been tested for its adaptability. Farmers have sufficient knowledge on the causes and the potential solutions to overcome most constraints. They know that soil suitability is closely related to relief. They classify soils by a number of criteria and choose crops accordingly. Any programme designed to address wetland management in the region will have to take account of farmers' knowledge and adopt a holistic view of wetland management. Copyright © 2011 John Wiley & Sons, Ltd.