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1.
Wind erosion is a major contributor to desertification in the Sahel. Although three effective countermeasures for wind erosion (i.e. ridging, mulching with post-harvest crop residue, and windbreaks) have been proposed, they are not practical for Sahelian farmers. Therefore, we designed a new land management practice, termed the “Fallow Band System,” which can be used for both controlling wind erosion and improving soil fertility and crop production. This method does not impose additional expense and labor requirements on Sahelian farmers who are economically challenged and have limited manpower. The objective of this study was to evaluate the effects of this system on wind-erosion control and soil-fertility improvement. We conducted field experiments at the International Crops Research Institute for the Semi-Arid Tropics West and Central Africa and showed that (i) a fallow band can capture 74% of wind-blown soil particles and 58% of wind-blown coarse organic matter, which suggests that it can effectively control wind erosion, (ii) the amount of soil nutrients available for crops in a former fallow band was increased by the decomposition of trapped soil materials containing considerable amounts of nutrients, and (iii) the amount of soil water available for crops in a former fallow band was increased by the trapped wind-blown soil materials through improvement of rainwater infiltration into surface soil. These results lead to the conclusion that the “Fallow Band System” can be useful for preventing desertification and improving soil fertility in the Sahel, West Africa.  相似文献   

2.
Under the harsh conditions prevailing in the West African Sahel, farmers must deal with a range of environmental and socio-economic issues that constrain agriculture. Although scientific evidence indicates that wind erosion is potentially a major land degradation process, little is known about the Sahelian farmer's perception of the relative importance of wind erosion as a constraint to agricultural production. A village-level survey was therefore undertaken to assess farmers' views about the relative importance of perceived constraints to agricultural production in 41 villages across Niger. During the interviews, the communities' views were also recorded regarding the causes and consequences of wind erosion as well as known wind erosion control measures. Wind erosion ranked eighth overall and was listed by male farmers among the top 10 constraints in 54 per cent of the villages. It was perceived by male farmers to be a moderate to high constraint in 39 per cent of the villages but was not considered important by female farmers. Wind erosion ranked third among environmental constraints, behind drought and soil fertility. Wind erosion related health problems were generally of more concern than crop damage or loss of topsoil by wind erosion. Deforestation, removal of crop residue and land-clearing practices were identified by farmers as major contributors to soil losses by wind. To address this issue, at least 10 different low-cost technologies are currently being implemented by farmers, including leaving crop residue in the field, mulching and natural regeneration of vegetation. The survey results indicate that farmers are well aware of the overriding importance of their management practices, as opposed to climatic factors, on the current extent of wind erosion. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

3.
基于粒度对比法的坝上农田风蚀与粉尘释放量估算   总被引:4,自引:4,他引:4  
为了计算当前年内的农田风蚀量,该研究利用农田耕作层土壤粒度组成较均一,风蚀使表层可蚀性颗粒减少,不可蚀颗粒含量相对增加这一特点,通过比较一个风蚀季结束后,农田耕作层表层与下层可蚀性颗粒与不可蚀颗粒相对含量的变化,提出了一种估算当前年内土壤风蚀量和粉尘释放量的方法,并给出了风蚀量与粉尘释放量的计算公式。利用此方法对河北坝上地区主要农田类型土壤风蚀量和粉尘释放量进行计算。计算结果表明,2013年研究区农田风蚀量为960~5700 g/(m2·a),平均为2852.14 g/(m2·a),平均风蚀深度为0.21 cm/a,从强度上划分属于重度风蚀。农田平均粉尘释放量为768.16 g/(m2·a),约占农田平均风蚀量的29.00%。粉尘释放量与风蚀量之间有显著的线性相关关系,翻耕耙平地的风蚀量和粉尘释放量显著大于留茬地。该方法的估算结果与前人采用其他方法得到的结果以及实地观测得到的结果基本吻合。  相似文献   

4.
The contribution of local knowledge to ecological sciences has not been fully exploited: there is still a gap between the recognition of farmers' knowledge as valid and an effective use of such knowledge in activities aimed at sustainable development. This study explores the use of farmers' indicators of erosion for developing a rapid tool for water erosion assessment at field level in the West Usambara Mountains (Tanzania). Two extensive field surveys were conducted in the research area concurrently. One survey consisted of applying an established erosion assessment method, the Assessment of Current Erosion Damage (ACED). According to the erosion features observed, fields were classified into five erosion classes, from very slightly eroded to very severely eroded. The second survey consisted of recording the type and number of indicators of erosion listed by farmers and present in the fields. The number of farmers' indicators per field increased with erosion intensity, from less than four in slightly eroded fields to more than eight in severely eroded fields. All farmers' indicators were positively correlated to the ACED erosion assessment classes. However, two groups of farmers' indicators could be distinguished in terms of erosion assessment: strong indicators, which were observed in more than 70% of cases in severely eroded fields, and weak indicators, which were observed more frequently in slightly and moderately eroded fields. Weak indicators appeared to be indicative of other land degradation phenomena, such as chemical fertility decline. Strong indicators and number of indicators were used to create a field erosion assessment tool in the form of a classification tree. The tree was built using one half of the field survey data and validated using the other half. The tree consisted of a hierarchical sequence of questions. Presence of rills and number of farmers' indicators were the most important factors of the tree. The validation yielded a highly significant Spearman's rho correlation coefficient (0.81). The contingency table showed that more than 80% of very severely eroded fields were correctly classified, whereas most misclassification occurred among slightly and moderately eroded fields. Farmers include land degradation phenomena and soil fertility decline in their definition of soil erosion. Soil and water conservation planning should address this broader farmers' perception by including, e.g., soil fertility improvements beside soil conservation. The distinction between strong and weak indicators of erosion is important in recommending the right intervention in the right spot, e.g., by counteracting soil erosion where strong indicators are present and by improving chemical fertility where weak indicators are present. The classification tree is of empirical nature and may need adaptation before being applied to other areas. The proposed methodology can be easily replicated and showed a high potential to provide extensionists with a field tool for erosion assessment. The classification tree was a successful example of integrating different types of knowledge for enhancing the co-operation between stakeholders involved in the erosion-control activities.  相似文献   

5.
The principal objective of this investigation was to quantify erosion rates for five agricultural fields in three separate study areas in Saskatchewan. The radionuclide tracer caesium-137 (137Cs) was used to quantify net erosion and net deposition within the landscape over a 30-year period. Uneroded (native) sites were used to establish the mean background level of 137Cs in each of the study areas. The assumption being that agricultural sites with 137Cs areal activities greater than the native site were subject to deposition, and sites with 137Cs less than the native control site were subject to erosion. A linear proportionality model was used to convert the loss or gain of 137Cs to net soil erosion or deposition. Results have indicated that accelerated (anthropogenic) erosion has been commonplace on arable land in Saskatchewan, even on near-level fields (< 1.3 degrees). The net integrated sediment output from the five agricultural fields ranged from — 0.6 t th−1 y−1 to — 6.8 t ha−1 y−1 (where negative values represent erosion). What is more alarming is that between 40 and 75 per cent of all sites sampled within individual fields had erosion rates in excess of the generally accepted rate of soil formation (1.0 t ha−1 y−1). Also, in one highly eroded field (Crystal Springs medium sloping site) 65 per cent of the sites sampled exceeded the upper tolerable erosion rate of 11.0 t ha−1 y−1. These results indicate significant degradation of the non-renewable soil resource has occurred over the past 30 years and is still presently active. Land degradation by accelerated erosion would result in reductions in effective rooting depth, soil moisture holding capacity, essential nutrient stores, and would adversely effect the physical structure of the topsoil. The major reason for accelerated erosion on arable land in Saskatchewan is the practice of summer fallowing, where the field is left in a ‘bare’ state and repeatedly tilled every second or third year. During a fallow period, or prior to crop emergence during a cropping year, fields are subject to wind and water erosion. On near-level fields wind would be the dominant transport agent, while on sloping fields inter-rill and rill erosion would be the primary forces of erosion. It is suggested that the appropriate conservation farming response would be to increase application of surface mulches and possibly to decrease the frequency of summer fallowing. Without such efforts long-term sustainable agricultural production in the Prairies of Canada is considered to be a tenuous land use practice.  相似文献   

6.
A survey was carried out in 136 farm‐households from seven villages in 1995 and 1996 to analyse the traditional fallow cultivation system in Niger. Farmers were asked to give information about land use on their fields, focusing on cropping and fallow periods as well as on cultivation changes compared to the past. In addition, they were interviewed about their management strategies to maintain or improve soil fertility. Millet‐based systems clearly dominate at all sites, either in pure form or intercropped with cowpea, groundnut, sorghum or roselle. At present, almost half of all farmers cultivate their fields on average up to 5 years until it is left fallow. About one‐third use their fields permanently. Most farmers use short fallow periods of 1 to 5 years. Moreover, there was a decrease in the cropping area left fallow, and the fallow period also decreased steadily in the past years. In the mid‐1970s the average fallow period was about 8 years, decreasing to 2.5 years in 1996. The actual fallow periods are too short to allow sufficient positive effects on soil fertility and farmers are aware of this problem. Consequently, farmers employ different fertilization techniques which aim at maintaining or restoring the soil nutrient pool of the fields while providing physical protection against wind and water erosion. Most farmers use animal manure to improve soil fertility and apply mulch from different sources, millet stalks and branches, for soil regeneration. Few farmers employ other strategies such as mineral fertilizer or planting pits. The farmers try to optimize the use of internal and external resources resulting in a mixture of different fertilization and soil protection methods. Internal resources play by far the most important role. Due to the generally limited resource availability farmers concentrate their management efforts on certain areas within each field or on selected fields only. This means a decreased crop production for the individual household and a higher risk of soil degradation because of soil mining or increased erosion risk on the field area where soil fertility management cannot be practised. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

7.
This paper investigates farmers' perceptions of soil erosion and how it affects crop yields, land values, and private conservation investments in India's semiarid tropics. It is based on three types of data: (1) a survey of farmers in three study villages; (2) a plot survey by a professional soil surveyor in the same villages; and (3) experimental and simulated data from nearby research stations with similar conditions. Farmers' perceptions of erosion are compared to the surveyor's using kappa, a statistical measure of interrater agreement. Perceived erosion–yield relationships are estimated econometrically and compared to experimental and simulated data. Effects on land values and conservation investments are estimated econometrically. Findings suggest that farmers are keenly aware of rill erosion but less aware of sheet erosion; kappa values ranging from 0 to 0·28 suggest low agreement with the soil surveyor. They anticipate annual yield losses of 5·8–11 per cent due to rill erosion; these figures are reasonably consistent with those from nearby research stations. They anticipate yield increases of 3·8–14·5 per cent due to installation of soil conservation bunds, largely because they can harvest soil from up the slope and capture organic matter. Perceived erosion has some effect on land values and soil conservation investments, but other factors such as irrigation and soil type have a much greater effect. These findings suggest that promoting soil conservation requires capitalizing on farmers' interest in short‐term gains, such as from water and nutrient management. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

8.
改进粒度对比法估算单次农田风蚀量   总被引:4,自引:1,他引:3  
为了定量估算单次大风蚀事件的土壤风蚀量,该研究采用改进的粒度对比法对2014年春季一次大风蚀事件的农田风蚀量进行了估算。结果表明,在这次风蚀事件中,研究区农田风蚀量在0.35×106~4.11×106 kg/km2之间,平均为1.30×106 kg/km2,平均风蚀厚度0.9 mm。各采样点的风蚀量存在较大差距,翻耕耙平地的风蚀量显著大于莜麦留茬地,是莜麦留茬地风蚀量的2.85倍。这次风蚀事件使研究区2014年农田风蚀量增加了1倍,可见大风蚀事件对农田风蚀量的影响较大,一次风蚀事件产生的风蚀量可能超过多次小风蚀事件的总和。改进后的粒度对比法具有多方面的优势,取样厚度稍有变化,不可风蚀颗粒物的粒径取值范围稍有变化,都不会对公式计算结果造成显著影响。该方法方便快捷,操作简单,适用于地面平坦、不可风蚀物含量较高的农田上大风蚀事件风蚀量的估算。该研究在区域农田土壤风蚀评价和风蚀模型验证方面具有较好的应用前景。  相似文献   

9.
Data and information about farmers' perceptions of soil degradation were collected using household survey, focus group discussion and field observations. The results indicate that farmers in the Sidama zone of southern Ethiopia are able to identify soil erosion and fertility loss indicators, take a holistic view of soil degradation and have a broad knowledge of the reasons for soil degradation. They perceive soil degradation mainly by reduced yields, soil changing in appearance and becoming stoney or coarse. The most frequently mentioned soil erosion indicator was soil becoming coarse and stony, followed by rill formation, dissection of fields and gullies and topsoil removal. The most important perceived indicator of soil fertility loss was reduced crop yield, followed by poor crop performance and yellowing of the crop. Farmers also have knowledge of solutions; however, participation in soil conservation activities is minimal because of the immediate threat of food insecurity. Any programme designed to address soil degradation in the region will have to be cognisant of farmers' knowledge and holistic view of soil degradation, and be integrated with aid measures to guarantee food security. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

10.
The following study was conducted to determine smallholders' land use management practices and agricultural indicators of soil quality within farmers' fields in Chuka and Gachoka divisions in Kenya's Central Highlands. Data on cropping practices and soil indicators were collected from farmers through face‐to‐face interviews and field examinations. Farmers characterised their fields into high and low fertility plots, after which soils were geo‐referenced and sampled at surface depth (0–20 cm) for subsequent physical and chemical analyses. Farmers' indicators for distinguishing productive and non‐productive fields included crop yield, crop performance and weed species. Soils that were characterised as fertile, had significantly higher chemical characteristics than the fields that were of poor quality. Fertile soils had significantly higher pH, total organic carbon, exchangeable cations and available nitrogen. Factor analysis identified four main factors that explained 76 per cent of the total variance in soil quality. The factors were connected with farmers' soil assessment indicators and main soil processes that influenced soil quality in Central Kenya. Soil fertility and crop management practices that were investigated indicated that farmers understood and consequently utilised spatial heterogeneity and temporal variability in soil quality status within their farms to maintain and enhance agricultural productivity. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

11.
Is conservation tillage suitable for organic farming? A review   总被引:3,自引:1,他引:3  
Conservation tillage covers a range of tillage practices, mostly non‐inversion, which aim to conserve soil moisture and reduce soil erosion by leaving more than one‐third of the soil surface covered by crop residues. Organic farmers are encouraged to adopt conservation tillage to preserve soil quality and fertility and to prevent soil degradation – mainly erosion and compaction. The potential advantages of conservation tillage in organic farming are reduced erosion, greater macroporosity in the soil surface due to larger number of earthworms, more microbial activity and carbon storage, less run‐off and leaching of nutrients, reduced fuel use and faster tillage. The disadvantages of conservation tillage in organic farming are greater pressure from grass weeds, less suitable than ploughing for poorly drained, unstable soils or high rainfall areas, restricted N availability and restricted crop choice. The success of conservation tillage in organic farming hinges on the choice of crop rotation to ensure weed and disease control and nitrogen availability. Rotation of tillage depth according to crop type, in conjunction with compaction control measures is also required. A high standard of management is required, tailored to local soil and site conditions. Innovative approaches for the application of conservation tillage, such as perennial mulches, mechanical control of cover crops, rotational tillage and controlled traffic, require further practical assessment.  相似文献   

12.
Choices in project approach affect the continuation of soil and water conservation (SWC) after project withdrawal, and thus the sustainability and cost effectiveness of the project. A SWC project was carried out in southern Mali between 1986 and 1998. Its features were the promotion of cheap and simple SWC measures, a participatory village extension approach with limited use of incentives, and the incorporation of the SWC programme in an existing Malian extension service. By 2000, farmers in half the 5000 villages in southern Mali had been trained in SWC. By 2002, erosion‐control measures had been installed in 94 per cent of the villages in southern Mali by 46 per cent of the farmers and in 15 per cent of the fields. Though external donor support has stopped, farmer adoption is steadily continuing and spreading to untargeted villages. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

13.
The loss of nutrients by wind erosion is generally attributed to losses by suspension, since suspension selectively removes the finest particles. However, because the main mass of sediment is moved by saltation during an event, the main mass of nutrients is also moved by saltation. Nutrient losses from one field during one wind erosion event can be as high as 73 per cent of the N and 100 per cent of the P needs for crop production. Vegetated areas have a higher dust deposition because of the filtering effect of the vegetation and the reduction of drag forces causing a higher deposition. This refutes the general assumption that deposition of suspended dust is homogeneous for a larger area. In the Sahel, two types of dust can be distinguished, the Harmattan dust is richer in nutrients and regarded as a real input of nutrients. The convectional storm dust has a nutrient content comparable with the nutrient content of the dust fraction of the topsoil and can't be regarded as input of nutrients. From research on nutrient losses by water erosion at the plot scale, it is concluded that nutrient erosion by water can cause serious losses of nutrients. But at the village scale, the losses are considerably smaller than at the plot scale. Measurement and subsequent nutrient budget analyses around the village Dangadé in Burkina Faso indicated that this area is especially vulnerable for wind erosion by saltation transport. This demonstrates that in the Sahelian environment, the effect of wind erosion at the village scale can't be ignored. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

14.
Using the simulation model described in Part I, this paper examines the impact of erosion on soil productivity, how the impact varies according to initial soil conditions and organic matter management and the economic cost of erosion measured as net present value. The reference crop is winter wheat grown in Chunhua in the southern Loess Plateau. Biomass yield is plotted over 100 years for four erosion scenarios represented by 0, 9, 27 and 47 per cent slopes, three initial soil conditions indicated by 0·5, 1 and 2 per cent organic matter, and two management levels determined by high or low levels of reincorporation of organic residues. Calculations of soil productive half‐life (time to half initial yield) and whole‐life (to equilibrial yield) are presented. The principal findings are that decline in soil productivity is caused by both erosion and insufficient return of organic matter. By increasing organic matter input, erosion damage is offset and soil productive life prolonged, but this is a costly strategy. If yield decline caused by erosion is isolated, erosion control is more important on a high organic matter input system. A maximum soil productive half‐life of 600 years is achieved with no erosion, high initial organic matter and return of organic residues; minimum half‐life of 10 years is with high erosion, low initial organic matter and little return of residues. In between, there are complicated interactions that significantly affect the economic cost of erosion and hence the decisions farmers make in investing in conservation practices. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

15.
In the Horqin Sandy Land of eastern Inner Mongolia in northern China, wind erosion in farmland is very common in a period from thawing of frozen surface soil in mid-March to sowing of crops in the end of April, largely because of dry and windy weather. However, little is known about the magnitude of wind erosion and associated nutrient losses due to erosion and the addition of nutrients by airborne dust deposition to farmlands during this period. A field experiment was conducted in an Entisol with sand origin under corn (Zea mays L.) production to investigate daily changes in wind speed and wind erosion intensity (as measured by soil transport rate) over a period from 20 March to 30 April 2001. We also measured daily rates of airborne dust deposition during the spring seasons with the high frequency of dust storm occurrence. The rates of soil transport by wind varied greatly from 13.2 to 1254.1 kg ha−1 per day, averaging 232.1 kg ha−1 per day, largely attributable to great variation between days in wind speed within the study period. The potential losses of nutrients through wind erosion were 0.26–24.95 kg ha−1 per day (averaging 4.62 kg ha−1 per day) in organic matter, 0.02–1.64 kg ha−1 per day (averaging 0.31 kg ha−1 per day) in nitrogen and 0.01–0.7 kg ha−1 per day (averaging 0.13 kg ha−1 per day) in phosphorus. The mean rates of airborne dust deposition ranged from 4.0 to 48.9 kg ha−1 per day, averaging 19.9 kg ha−1 per day, during the spring seasons. The potential addition of organic matter, nitrogen and phosphorus by dust input to the experimental field was, on average, 0.54, 0.04 and 0.02 kg ha−1 per day, respectively. Although the addition was a fraction of the losses due to erosion, nevertheless, dust input in the spring seasons is one of the major suppliers of soil nutrition. The fact that the addition of nutrients by dust is about 1/10 of the losses of soil nutrients through wind erosion suggests that developing and adopting more effective management practices to reduce soil erosion losses and to improve soil fertility are crucial to achieve a sustainable agricultural system in a fragile, semiarid sandy land environment.  相似文献   

16.
17.
In areas susceptible to erosion, there is the need for a comprehensive soil conservation programme so as to be able to prevent catastrophic soil erosion problems. The absence of such a programme in central eastern Nigeria, that has a total land area of 20 000 km2, necessitated the drawing up of a soil conservation strategy for the area. The aim was to provide information for better land-use planning and proper environmental and soil management. To achieve this, topographic, soil and landform maps of the area at the scale of 1:50 000 were used to delineate into slope land units, viz: 0–4 per cent, <4 per cent, drainage basins and headwaters. These slope units and estimated soil erosion hazard units using the revised universal soil loss equation (RUSLE) were employed to form a general purpose land classification based on the USDA land capability classification and FAO framework on land evaluation.The soil loss tolerance of the area falls between 1·16 and 1·30 Mg ha−1 yr−1, while the erosion hazard units are considered generally suitable for the various land utilization types, with a number of limitations the main ones being erosion and waterlogging. The soil conservation measures proposed involved the application of bioenvironmental processes in the area and appropriate watershed management. The techniques proposed are those based on low input technology, affordable by rural farmers. It is concluded that these soil conservation measures will be adequate for sustainable agricultural production in the area. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

18.
以内蒙古自治区武川县上秃乡保护性耕作农田地表土壤为研究对象,利用移动式风蚀风洞对麦茬深松农田地表进行土壤抗风蚀效果测试研究.研究结果表明,麦茬深松农田地表相对传统耕作地表可降低近地表风蚀土壤量,对土壤输沙影响显著.该研究可为防治农田土壤风蚀提供理论依据  相似文献   

19.
This paper describes the results of a survey on farmers' perceptions of the effect of woody natural vegetation on wind erosion. Sixty farmers were interviewed in three villages in northern Burkina Faso. The farmers mentioned that the presence of woody vegetation between the crops could benefit yield, but feared competition between the natural vegetation and the crop. Vegetation in a field was considered to increase deposition and decrease erosion on that field. The most important vegetative characteristics that affect wind erosion were, according to the farmers, vegetation's shape, porosity, flexibility and arrangement of the vegetation in the field. At present, most farmers do not apply this knowledge to the management of the natural woody vegetation on their fields. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

20.
农牧交错带土地利用类型对土壤风蚀的影响   总被引:2,自引:0,他引:2  
[目的]研究农牧交错带不同土地利用类型对土壤风蚀的影响,为干旱沙区土地资源的合理利用及经营耕作提供科学依据。[方法]通过气象资料和野外风蚀试验,分析该区不同土地利用方式下的土壤风蚀状况。[结果]不同土地利用类型对土壤风蚀的影响显著,在不同利用类型的人工草地中羊草地较苜蓿地减蚀效果显著,天然草地中滨草地减蚀效果优于蒿草地,人工草地较天然草地显著降低土壤风蚀量。农田用地中耕翻地土壤风蚀量最高,未留茬免耕玉米地较耕翻地风蚀量减少46.7%~48.6%;作物留茬地土壤减蚀效果显著,且留茬作物不同,减蚀效果差异明显,玉米留茬较耕翻地风蚀量减少了58.1%~63.5%,荞麦留茬较耕翻地减蚀率为50.5%~54.6%。在不同地形坡地中迎风坡风蚀量高于背风坡3.12~3.73倍。[结论]应在该地区适宜增加人工草地种植面积,减少冬春季节耕翻地面积,减少迎风坡土地的开垦利用,在冬春季节采取地表覆盖或者作物收获后留茬的保护措施,以降低土壤风蚀程度。  相似文献   

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