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1.
The increasing problem of landlessness in Ethiopia has put pressure on regional governments to redistribute land. In 1997 and 1998, a major land redistribution was undertaken in the Amhara Region, reducing landlessness where implemented. While the impacts of such redistributions have been hotly debated, little empirical evidence exists concerning the actual impacts of redistribution. We find that land redistribution in the Amhara Region has had a positive impact on land productivity, by increasing access to land for farmers who are more interested or able to use purchased inputs such as fertilizer and herbicides. Our results, however, do not show much effect of the recent land redistribution or expectations of future redistribution on land improvement and management. Thus, to the extent that investments in land improvement are necessary for conservation purposes, it appears that policy change to stop land redistributions is unlikely to have a substantial impact on reducing land degradation. Credit and extension programmes and improving land rental markets, however, present better strategies for improving land management in this region of Ethiopia. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

2.
Land use in a 208 ha representative catchment in the Tigray Highlands, Dogu'a Tembien district in Northern Ethiopia was studied in relation to soil geography. Typical soils are Vertisols, Vertic Cambisols, Cumulic Regosols, Calcaric Regosols and Phaeozems. Patterns of land use vary greatly within the catchment and results from χ2‐tests showed strong associations (p < 0·001) between soil type and land use and crop production system. There is a strong association between cropland and colluvium high in basaltic content because the most fertile soils, such as Vertisols and Vertic Cambisols, have developed on this material. Preference is for autochthonous soils on in situ parent material, irrespective of the rock type, to be put under rangeland. Land use by smallholders in Dogu'a Tembien appears to be the result primarily of the interaction between environmental and social factors. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

3.
The highlands of Ethiopia suffer much from environmental degradation. Funded by the European Union, an interdisciplinary team carried out research using geographical information and remote sensing technology to analyse degradation and to provide support for rehabilitation planning. The degradation was analysed on a subregional scale, using 25×25 metre grids, which was an innovative and challenging aspect of the research and did justice to the high spatial variability of the area. The universal soil loss equation (USLE) was employed to assess the potential and actual erosion risk. The factors for the erosion models were derived from the basic data using expert rules. The research illustrates how a geographical information system (GIS) can play an important role in supporting rehabilitation planning at both the farm and the subregional levels. The results show the locations where rehabilitation is most urgently needed. From the results, it can be concluded that different processes are of importance at different scale levels. At the farm level, attention should be paid to the erosion protection measures used by the farmer. However, on a higher scale, factors such as the presence of towns, accessibility of the area and the presence of malaria play a role. Further research is required to study and model the influence of these factors on the environment. © 1998 John Wiley & Sons, Ltd.  相似文献   

4.
Little is known on the hydrological behavior of the volcanic ash soils, which are characterized by extremely high porosities and hydraulic conductivities. In this study the occurrence and hydrological effects of water repellency were investigated at a plot scale for different types of land use and volcanic soils in Mexican volcanic highlands from Michoacan, Mexico: [1] fir, pine and oak mixed forest soils developed from lavas, [2] soils developed from volcanic ashes and pyroclastic sediments under sparse fir, pine and oak forest and shrubland, [3] pine and oak forested soils developed from lavas and pyroclastic sediments, and [4] bare soils on recent ash sediments in plain surfaces. Soil water repellency was assessed using the water drop penetration time test and rainfall simulations were performed on circular plots (50 cm in diameter) during 30 min and at an intensity of 90 mm h− 1 in order to study the hydrological response of each area. The return period for storms with a similar intensity in the area is 10 years. The shape and depth of the wetting front after simulated rainfall was also analyzed. Soil water repellency showed a high variability among the different studied zones. Organic matter content, soil texture and acidity were the most important factors for developing hydrophobicity. A wide range of soil water repellency classes (hydrophilic to severely water-repellent soils) has been found in soils under dense fir, pine and oak mixed forests or shrubland, while inexistent or slight water repellency has been observed in soils under sparse forest or at bare ash-covered areas. At a plot scale, marked differences in the hydrological behavior of the studied land use and soil zones were observed after the rainfall simulations. Soil water repellency contributes to fast ponding and runoff generation during the first stages of rainstorms. Runoff was enhanced in water-repellent forested soils (average runoff coefficients between 15.7 and 19.9%), in contrast to hydrophilic or slightly water-repellent soils, where runoff rates were lower (between 1.0 and 11.7%). Shallow and irregular wetting fronts were observed at water-repellent zones, reducing the soil water storage capacity. The implications of soil water repellency in soil hydrology and erosion risk in the area shed light on the soil hydrology of the studied ecosystems, and can contribute to develop better management policies.  相似文献   

5.
为高效利用天然降水资源, 提高自然降水水分利用效率, 在山西临汾采用随机区组设计方法研究了田间微集雨种植方式及其播种行距对小麦产量及水分利用效率的影响.结果表明: 集雨产流带覆盖面积与种植带面积比例为1:1.5和1:1的种植方式平均产量均较对照(露地种植)显著增产, 1:1.5、1:1和露地种植的播种行距分别以11.3 cm、15 cm和15 cm具有较好的增产效应; 1:1.5和1:1种植方式在拔节期的个体生物学性状株高、单株分蘖和单株绿叶数优于露地栽培; 1:1.5、1:1和露地栽培的水分利用效率分别为19.8 kg·mm-1·hm-2、17.4 kg·mm-1·hm-2、14.3 kg·mm-1·hm-2.该项研究同时明确了不同田间微集雨种植方式在各生育时段的土壤水分变化动态特征.  相似文献   

6.
不同模拟雨量下微集水种植对农田水肥利用效率的影响   总被引:4,自引:4,他引:4  
为了探索微集水种植的增产机理及其适宜的雨量范围,通过大田模拟降雨试验,在2006-2007年研究了作物生长期间不同降雨量下微集水种植玉米对农田水肥利用效率的影响。结果表明,在230~440 mm雨量下,微集水种植玉米可提高其籽粒产量及水肥利用效率,2006年籽粒产量、农田水分利用效率(WUE)以及氮、磷和钾养分利用效率(NUEN、NUEP和NUEK)在230 mm雨量下较对照分别提高了75.4%、73.3%、56.0%、44.4%和106.8%,340 mm雨量下分别提高了36.7%、40.2%、22.8%、18.1%和35.5%,440 mm雨量下与平作相比差异不明显;2007年籽粒产量、WUE、NUEN、NUEP和NUEK在230 mm雨量下较对照分别提高了82.8%、77.4%、64.0%、52.2%和123.9%,340 mm雨量下分别提高了43.4%、43.1%、30.4%、21.8%和41.2%;440 mm雨量下籽粒产量、WUE和NUEN分别提高了11.2%、9.5%和10.1%。由此可知,在玉米全生育期降雨量230~440 mm范围内,通过微集水种植可以增加籽粒产量,提高农田水肥利用效率,尤其在雨量较低时,提高水肥利用效率及增产效果尤为明显。  相似文献   

7.
不同土地利用模式与管理实践下的土地经济效益响应   总被引:1,自引:0,他引:1  
农户土地利用要素投入具体表现在土地利用模式与管理实践的差异。不同的土地模式与管理实践不仅是农户对局地自然、社会、经济条件及土地政策的响应,而且还是诱发土地质量变化最直接的外部诱因。该研究以重庆市万洲区万洲居仙试验区作为研究区,选取5种土地利用模式及与之相应的土地管理实践,获取576个0~20 cm表层土壤样品,分析不同土地利用模式下土壤性质变化及其经济效益的响应。结果表明,2003-2005年,试验区紫色土的土壤肥力总体上有所上升,但不同土地利用模式对其贡献程度不一,其顺序为:粮、经、菜间、套土地利用模式(CEV)>菜、经、菜间、套土地利用模式(VEV)>果、粮、菜间、套土地利用模式(FCV)>粮、豆、粮间、套土地利用模式(CBC)>单一土地利用模式(MONO);土地经济系数对土壤性质响应明显,其变化方向较一致,土壤保肥供肥能力越强,其土地经济系数越大;菜、经、菜间、套土地利用模式(VEV)更适合于试验区,是农户选择的最优土地利用模式。  相似文献   

8.
African medicinal plant species are increasingly threatened by overexploitation and habitat loss, but little is known about the conservation status and ecology of many medicinal species. Mondia whitei (Apocynaceae, formerly Asclepiadaceae), a medicinal liana found in Sub-Saharan Africa, has been subject to intensive harvesting and habitat loss. We surveyed M. whitei in Kakamega Forest, the largest of three remnant Kenyan forests known to contain the species. In 174 100 m2 plots, we quantified the status of M. whitei and investigated its relationships with land use, disturbance and harvesting. With average adult densities of 101 plants/ha, M. whitei is not locally rare in Kakamega. However, the absence of flowers and fruits, together with a spatial disconnect between adults and juveniles, suggests that sexual regeneration is patchy or infrequent. Comparing among habitat types, we found that plants were most abundant in regenerating indigenous forest managed by the Forest Department, which permits some extractive uses. Conversely, plants were largest in indigenous forest managed by the Kenya Wildlife Service, which prohibits extractive uses. Most anthropogenic disturbances were not associated with M. whitei, but plant occurrence and density were higher along paths used by livestock than along other types of paths. Larger individuals appeared to be preferentially harvested, but adult plants were more likely to occur in harvested plots than un-harvested plots. This work emphasizes that restrictions on disturbance and extractive use do not automatically promote medicinal plant conservation. Moreover, harvesting may have important genetic and demographic consequences that are overlooked by studies focused on numerical losses.  相似文献   

9.
Abstract

Improvement of agricultural water use efficiency is of major concern with drought problems being one of the most important factors limiting grain production worldwide. Effective management of water for crop production in water-scarce areas requires efficient approaches. Increasing crop water use efficiency and drought tolerance by genetic improvement and physiological regulation may be a means to achieve efficient and effective use of water. A limited water supply inhibits the photosynthesis of plants, causes changes of chlorophyll contents and components and damage to photosynthetic apparatus. It also inhibits photochemical activities and decreases the activities of enzymes in plants. Water stress is one of the important factors inhibiting the growth and photosynthetic abilities of plants through disturbing the balance between the production of reactive oxygen species and the antioxidant defence, causing accumulation of reactive oxygen species which induce oxidative stress to proteins, membrane lipids and other cellular components. A number of approaches are being used to enhance water use efficiency and to minimize the detrimental effect of water stress in crop plants. Proper plant nutrition is a good strategy to enhance water use efficiency and productivity in crop plants. Plant nutrients play a very important role in enhancing water use efficiency under limited water supply. In this paper we discuss the possible effective techniques to improve water use efficiency and some macronutrients (nitrogen, phosphorus, potassium, calcium and magnesium), micronutrients (zinc, boron, iron, manganese, molybdenum and chloride), and silicon (a beneficial nutrient) in detail to show how these nutrients play their role in enhancing water use efficiency in crop plant.  相似文献   

10.
A total of 42 sampling sites were selected in the riverine network of the upper Han River basin (approximately 95, 200 km2) of China. Over the time period of 2005–2006, 252 water samples were collected and analyzed for physico-chemical variables in order to investigate their spatio-temporal variability in particular the relationship with land use and land cover. Analysis of variance (ANOVA) indicated significant spatial variability in pH, EC, TDS, turbidity, SPM, ORP and nitrogen across the basin. Meanwhile, nitrogen, ORP, IMn and turbidity generally displayed higher values in the rainy season. Correlation analysis and regression analysis indicated that water temperature, IMn, and nitrogen were significantly related to vegetated coverage, and subwatersheds with higher vegetation cover had relative lower turbidity, SPM, IMn, nutrients and TDS. Bare lands had significant influence on nitrogen concentration in the riverine network, implying its large geologic sources in the basin. Percentage of urban area was the predictor for pH and DP, while agricultural land for SPM and IMn. The research could provide critical information in sustainable land use practice for water resource conservation for the basin.  相似文献   

11.
低丘红壤区农林间作系统水分利用竞争性评价   总被引:1,自引:0,他引:1  
赵英  张斌 《土壤》2012,44(4):671-679
农林复合系统由于其复杂的物种配置、下垫面差异及土壤水力学性质的空间变异,可能影响土壤水分运动及水量平衡,并决定物种间水分竞争性。本文研究了南方低丘红壤区花生南酸枣农林复合系统中土壤水分的时空动态、土壤水流通量和方向的二维变化;结合土壤水量平衡,评价了农林复合系统组分间的土壤水分竞争关系。研究结果表明:农林复合系统能够利用50~100 cm土层土壤水分,对干旱有一定缓冲作用;但在季节性干旱土壤水分期向树行运动,说明南酸枣与花生间作系统也存在着水分竞争,竞争同树龄和空间距离有关。花生的种植减小了地表径流却加剧了土壤的流失。农林复合系统改变了土壤水量平衡,复合后系统蒸散量提高5%~12%,而净渗漏量及土壤水分贮存量减小。农林复合系统减小了30~100 cm土壤水分运动通量,引起土壤水分运动方向变化,影响了作物水分利用体系,需在设计优化管理水资源的农林复合模式时充分考虑这些因素。  相似文献   

12.
以旱地品种"西峰20"和"晋麦47"、水旱兼用型品种"石家庄8 号"、高水肥地品种"石4185"和"科农9204"5 个冬小麦品种为材料, 通过田间不同灌溉处理试验研究了不同抗旱类型冬小麦品种收获指数和群体水分利用效率对产量水分利用效率的影响差异。结果表明: 不同抗旱类型的小麦在不同灌溉处理下, 产量水分利用效率(WUEy)以及变化趋势存在显著差异。旱地冬小麦品种WUEy 和收获指数(HI)显著低于水地品种和水旱兼用型品种。不同品种间WUEy 最大相差42.01%, HI 相差25.91%。HI 和群体水分利用效率(WUEbm)与WUEy 呈显著正相关关系。株高与HI 呈显著负相关关系(R2=0.574)。在不灌溉条件下, 品种间WUEy 差异源自HI 的差异; 而在补充灌溉条件下, 品种间WUEy 的差异源自WUEbmHI 的共同作用。说明不同抗旱类型的小麦对不同灌溉处理的响应方式和适应策略不同。旱地品种在干旱胁迫条件下, 主要靠增加WUEbm 来提高WUEy; 而水地品种和水旱兼用型品种在补充灌溉中凭借较高的WUEbmHI 共同作用提高WUEy。  相似文献   

13.
生态集约化养分管理对春玉米产量和氮素利用率的影响   总被引:4,自引:0,他引:4  
通过两年田间试验,研究了吉林玉米带不同氮素管理措施对春玉米产量、氮素吸收、氮素平衡状况以及经济效益的影响。两年的结果表明:与农民习惯施肥(FP)相比,生态集约化养分管理措施(EI)在减少氮肥用量28%的情况下,并未影响作物的产量和氮素吸收,而其氮素回收率,农学效率,偏生产力和经济效益却分别提高了48.1%、56.9%、43.8%和11.0%; 第一年不施氮肥第二年补施氮肥不会影响第二年春玉米产量和氮肥利用率。在氮素输出项中,EI处理两季作物氮素总表观损失仅为97 kg/hm2,而FP处理高达226 kg/hm2。因此,在考虑高产的基础上兼顾保护环境的要求,基于氮肥农学效率、作物目标产量和作物施肥反应的生态集约化养分管理措施是一种较为理想的氮素管理措施。  相似文献   

14.
The combined effects of erosive rains, steep slopes and human land use have caused severe land degradation in the Ethiopian Highlands for several thousand years, but since the 1970s, however, land rehabilitation programmes have been established to try to reverse deterioration. In order to characterize and quantify the transformations in the north Ethiopian Highlands, a study was carried out over 8884 km2 of the Tigray Highlands of northern Ethiopia. Using Landsat Multispectral Scanner and later Thematic Mapper imagery (1972, 1984/1986 and 2000), historical terrestrial photographs (1974–1975) and fieldwork (2008), we prepared land use and cover maps. For assessing the use of the historical terrestrial photographs, Landsat images from 1972 were classified using two different methods, namely conventional change detection (image differencing) and ground truthing (using the historical photographs of 1974–1975). Results show that the use of terrestrial photographs is promising, as the classification accuracy based on this method (Kappa coefficient 0·54) is better than the classification accuracy of the method based on image differencing (Kappa coefficient 0·46). Major land use and cover changes indicate the following: (1) a gradual but significant decline in bare ground (32 per cent in 1972 to 8 per cent in 2000); (2) a significant increase of bushland (25 to 43 per cent) and total forest area (including eucalypt plantations, 2·6 to 6·3 per cent); and (3) creation of numerous lakes and ponds. The dominant change trajectory (27 per cent of the study area) indicates a gradual or recent vegetation increase. These changes can be linked to the population growth and the introduction of land rehabilitation initiatives, complemented by growing awareness of land holders. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

15.
Infiltration capacity is an important variable for understanding and predicting a range of soil processes. This study investigated for different slope positions the effects of forest conversion to cultivation and grazing on soil infiltration capacity. Infiltration capacity was measured in the field in each land use type using a double‐ring infiltrometer. A total of 108 soil samples (3 slope positions × 3 land use types × 4 soil profiles × 3 soil depths) were collected to determine the variables that affect infiltration capacity viz. particle size distribution, organic carbon content, dry bulk density and soil moisture content. The results showed that in the cultivated and grazed land compared with forest, infiltration capacity and soil moisture content were 70 and 45% smaller respectively, and dry bulk density was 13–20% larger. Changes in soil structure caused by surface soil compaction because of tillage and animal trampling coupled with a smaller soil organic carbon content, are likely to be the principal factors causing the decline in infiltration capacity and soil moisture content after conversion of forest to cultivation and grazing.  相似文献   

16.
垄覆膜集雨对苜蓿草地土壤水分动态及利用效率的影响   总被引:2,自引:1,他引:2  
我国西北黄土高原干旱半干旱区年降雨稀少和土壤水分周期性亏缺, 导致人工草地生产力低下、水分利用效率低。本试验在旱作条件下, 将垄覆膜集雨措施应用于紫花苜蓿种植, 研究了沟垄宽比和覆膜方式对2 年龄苜蓿草地土壤水分动态及水分利用效率的影响。结果表明: 垄覆膜集雨在集雨前期(4 月中旬至6 月上旬)显著提高0~20 cm 土层土壤含水量, 在集雨中后期(6 月中旬至9 月下旬)显著提高0~120 cm 土层平均含水量,越冬期增加土壤水分入渗能力, 提高20~120 cm 土层平均含水量; 且垄覆膜处理的集雨效率高于土垄处理。随着生育时期的延伸, 垄覆膜处理0~120 cm 土壤平均贮水量呈先降后升的趋势, 土垄处理0~120 cm 土壤平均贮水量呈由高到低的趋势; 在苜蓿生长后期垄覆膜处理的蓄墒能力显著高于土垄处理。垄覆膜处理的平均水分利用效率为34.91 kg·mm-1·hm-2, 为对照(平作, CK)的2.25 倍, 土垄处理的平均水分利用效率为28.47kg·mm-1·hm-2, 为CK 的1.83 倍, 垄覆膜相对土垄处理平均水分利用效率提高22.62%; 垄覆膜处理以沟垄宽比为60 cm∶60 cm 和60 cm∶75 cm 的水分利用效率最高。  相似文献   

17.
18.
The NSW Soil Knowledge Network (SKN) is a small group of senior ex‐government soil scientists concerned that more needs to be done to improve soil management and stem land degradation with on‐ground extension and training workshops. Widespread attendance and positive feedback from SKN training courses and workshops indicate their extension success and confirm a strong demand for practical independent soil management advice aided by government‐based databases to enhance on‐site workshops. We argue that effective soil knowledge transfer requires interaction and discussion between soil scientists and land managers. This can bridge the gap between data and useful knowledge about soil and land management. The workshop format, where specific soil management issues of specific interest, such as soil acidity, nutrient management or soil sodicity, are discussed between land managers and soil scientists, has been a useful approach. A major concern is that soil scientists with knowledge and practical experience are getting older and fewer in number but few replacements are being appointed in private or government agencies. Also, despite soil electronic data and information being freely available, many land managers and advisors have difficulties accessing and translating soil data into relevant land management decisions. Dialogue with SKN members helps solve this problem because of their hands‐on and face‐to‐face approach with their audiences. The combination of data with effective soil knowledge transfer is successfully exhibited at SKN workshops for advisory groups and the ‘pits and kits’ field days as shown in the paper.  相似文献   

19.
为探究保护性耕作与施肥对渭北旱地春玉米田土壤耗水量和水分利用效率的影响,达到高效生产的目的。于2013—2015年在渭北旱塬实施了春玉米耕作与施肥田间试验,共设置6种耕作与施肥处理:翻耕+低肥(A1)、免耕+高肥(A2)、深松+平衡施肥(A3)、翻耕+无肥(B1)、免耕+无肥(B2)和深松+无肥(B3),测定了春玉米休闲期与生育时期0~200 cm土层土壤蓄水量和收获时籽粒产量。结果表明:1)保护性耕作能显著提高旱地玉米田土壤蓄水保墒能力。与传统翻耕处理B1相比,休闲期,B2和B3播前土壤蓄水量分别提高23.39 mm和27.73 mm(P0.05);耕作处理区,B2和B3全生育期土壤蓄水量平均提高13.41 mm和15.70 mm;耕作施肥处理区,A2、A3土壤蓄水量较A1分别提高13.15 mm、19.54 mm。2)平衡施肥能有效提高玉米全生育期平均土壤蓄水量,与不施肥处理相比,全生育期土壤蓄水量平均提高6.79 mm(P0.05)。3)保护性耕作与施肥能提高玉米籽粒产量与水分利用效率。耕作无肥处理区,与B1比较,B3处理产量提高212~576 kg×hm~(-2),水分利用效率提高0.83~2.21 kg×hm~(-2)×mm~(-1);耕作施肥处理区,A3产量与水分利用效率提高最为显著,产量较A1提高659~1 495 kg×hm~(-2),水分利用效率提高0.65~3.82 kg×hm~(-2)×mm~(-1)(P0.05)。3种施肥方式下以氮、磷、钾平衡施肥产量与水分利用效率提高幅度最大。4)对耗水量与产量进行相关性分析发现,抽雄—灌浆生育阶段土壤耗水量与产量呈显著正相关,保护性耕作提高玉米生长初期土壤蓄水保墒能力,提高春玉米抽雄—灌浆期土壤水分,增加作物生长关键时期对水分的利用效率,利于玉米籽粒产量的提高。因此在渭北旱地春玉米田,深松与平衡施肥组合能提高春玉米产量与水分利用效率,是该地区玉米高效生产较为适宜的种植模式。  相似文献   

20.
冬小麦是华北平原的主要作物,其生长受气候等环境因子和品种、管理措施等因素的共同影响。为了研究气候×基因型×水分管理互作对河北平原冬小麦产量及水分利用效率(WUE)的影响,以‘科农2009’‘藁优2018’和‘师栾02-1’3个该区域主栽冬小麦品种为材料,于2018—2019年沿北纬38°带,选择河北平原冬小麦主产区的4个典型试验站点(衡水、南皮、栾城、南大港)进行了不同水分管理(雨养、灌溉)的大田试验。结果表明:在灌溉条件下,衡水、南皮、栾城和南大港的小麦产量分别为6 316.7kg·hm~(-2)、5 204.1kg·hm~(-2)、4 356.5kg·hm~(-2)和2 597.7 kg·hm~(-2), WUE分别为1.62 kg·m~(-3)、1.72 kg·m~(-3)、1.36 kg·m~(-3)和1.08 kg·m~(-3);在雨养条件下,南皮、栾城、衡水和南大港的小麦产量分别为2 644.4kg·hm~(-2)、2 602.8kg·hm~(-2)、2 422.3kg·hm~(-2)影响1 784.3kg·hm~(-2),WUE分别为1.13kg·m~(-3)、1.10 kg·m~(-3)、1.18 kg·m~(-3)和1.01 kg·m~(-3)。统计分析表明,穗数是影响产量的最主要因素,气候×水分管理互作对产量和WUE均有极显著影响(P0.01),气候×基因型×水分管理互作对WUE有显著影响(P0.05);水分是影响产量和WUE的最重要因素。综合产量、耗水和WUE分析,在降水量偏少的年份,南皮在4个试验站点中冬小麦耗水量较少、WUE最高、产量较高。分蘖能力强的小麦品种是适宜该区域种植的潜力品种类型。  相似文献   

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