Restoration of surface soil fertility of an eroded red soil in southern China

To ameliorate degraded red soils and restore their productivity, it is necessary to quantitatively assess the effects of different land uses on soil fertility. In this study, surface soil samples (0–20 cm) under different land uses were collected from an 18-year ameliorative experiment site of a eroded red soil in Lanxi county, Zhejiang province of southern China. The status of surface soil fertility was quantified with a ryegrass growth test in the greenhouse and by numerical analysis of twelve important fertility indexes. The soil fertility indexes were grouped into three major factors using a factor analysis, i.e., organic matter-nitrogen-structure, acidity and phosphate. By means of principal component analysis and cluster analysis of these fertility factors, the fertility of the eroded red soil as a function of land use patterns had the following decreased order: vegetable land>paddy field, cropping arable land and ryegrass land>tea garden>citrus garden>forestland>wasteland. The result suggested that organic matter, total N, available N, and water-stable aggregates were the main characteristics for fertility restoration of the eroded red soil. Soil fertility was most rapidly restored where the soil had been used as vegetable land, and least restored when left as wasteland. The results indicated that land use strongly affected the fertility restoration of eroded red soils because of its effect on the input of nutrients and energy, thus determining the speed and direction of soil fertility evolution.     

江南红色丘陵区的水土流失及其治理途径

长江中游地区水土流失日益加剧,尤以江南红色丘陵区最为严重,素有“江南红色沙漠”之称。产生流失的主要根源是对森林的过度采伐和不合理的农林耕作制度。其治理途径应是:以农村能源建设为出发点,以稳定粮食生产为基础,大力改造和开发利用现有林业用地、荒山荒坡和侵蚀劣地,增加林草植被,改善生态环境,促进农村经济发展。     

南方红壤侵蚀区土壤肥力质量与人为活动可达性的空间关系——以福建长汀县朱溪流域为例

人为活动可达性对土壤肥力质量具有重要影响.以南方红壤侵蚀区典型流域福建省长汀县朱溪流域为研究区,选取10个土壤肥力质量因子,基于“3S”技术并结合野外调查,对10个土壤肥力质量因子进行叠加,生成土壤肥力质量等级图;根据相对高度、DEM生成的坡度、SPOT影像提取的土地利用图、距居民点和交通用地的远近,创建人为活动可达性综合评价指数,整个研究区可达性由最难到达至最易到达可分为5级.结果表明:1)人为活动可达性从“中等”到“困难”到“很困难”,土壤肥力质量总体呈上升趋势,可达性难度逐渐增大导致开发利用难度增大,人为活动的干扰程度相对减少;2)在人为活动可达性“容易”和“很容易”2个级别,分布着所有的“很好”和大部分“好”2个土壤肥力质量级别,并与流域下游的耕地地类对应,同时“容易”和“很容易”2个级别所在区域自然条件较好,人类开发利用强度大,导致部分区域土壤肥力质量级别较低;3)人为活动可达性是土壤肥力质量的重要但不是唯一影响因素;4)今后相关研究应加强土壤肥力质量综合评价模型中人为活动的定量表达,从而深入解 释南方红壤侵蚀区人为活动与土壤肥力的复杂关系.     

不同肥力水平和利用历史的红壤磷脂脂肪酸图谱

Analysis of phospholipid fatty acids(PLFAs) was used to estimate the microbial community structures of eight Chinese red soils with different fertility levels and land use histories.The total amounts of PLFAs in the soils were significantly correltaed with soil organic carbon, total nitrogen,microbial biomass C and basal respiration,indicating that total PLFA was closely related to fertility and sustainbility in these highly weathered soils.Soils of the eroded wastelan were rich in Gram-positive species .When the eroded soils were planted with citrus trees,the soil microbial population had changed little in 4 years but took up to 8-12 yearss before it reached a significantly different population,Multivariate analysis of PLFAs demonstrated that land use history and plant cover type had a significant impact on microbial community structure.Howver,the difference of soil microbial community structure in the paddy field compared to other land uses was not larger than expected in this experiment.     

Water erosion assessment using farmers' indicators in the West Usambara Mountains, Tanzania

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.     

Soil fertility affected by land use history,relief position,and parent material under a tropical climate in NW-Vietnam

In Vietnam as much as half of the total land area is already degraded by soil erosion and nutrient depletion. In particular, degradation due to deforestation is increasingly affecting mountainous areas in north-western Vietnam. The necessity to safeguard the farmers' livelihoods requires sustainable resource management, which firstly requires a qualitative and quantitative evaluation of resources. The objectives of the present study were to (1) identify the dominant soil types and their vulnerability using elicitation of local soil knowledge, (2) characterise the physical and chemical properties of the soils and (3) link them to the relief position and land use in order to (4) initiate sustainable soil use based on recommendations deduced from objectives (1) to (3). These objectives were achieved also by the elicitation of local knowledge. The final aim of the study was to initiate sustainable soil use based on recommendations for sustainable land use scenarios. The Chieng Khoi commune in Son La province of northern Vietnam was chosen as representative for other erosion-prone Southeast Asian sloping areas. In a participatory approach, combining local and scientific knowledge, sixteen sites were selected, representative for distinct relief positions, parent material (sand stone and silt stone), land use history, and erosion hazard. Chemical (e.g. content of organic matter, nitrogen, cation exchange capacity, base saturation, and plant available phosphorous) and physical properties (e.g. air capacity, plant available water) were used to estimate soil fertility. The predominant reference soil groups in the study area are Alisols and Luvisols, with a high diversity in respect to soil fertility. These soils are locally named ‘red soil’ and ‘black soil’, respectively. Although the main physical processes are erosion and selective sedimentation, farmers tend to underestimate their impact and causes, whereas soil quality was well-evaluated. Soils with high fertility were found on less eroded upper parts of hills and at sites, where agricultural use started only recently. Once degraded by cultivation practices, soils derived from sandstone did not recover even after more than 50 years of fallow. As a result of unsustainable land use, soils on middle and lower slopes are often affected by severe soil erosion, whereas foot slope soils suffer from accumulation of eroded infertile subsoil material as well as stagnic conditions. This study showed that unsustainable land use at upslope landscape positions has a severe impact on downslope areas. The elicitation of local knowledge facilitated the identification of such hot spots, allowing the implementation of spatially targeted conservation measures.     

侵蚀红壤区不同水土保持措施的土壤改良效果研究

结合野外调查和室内分析,研究了侵蚀红壤区不同水土保持措施下坡地土壤pH值和养分含量的变化,分析了不同水土保持措施的土壤改良效果。研究结果表明,不同水土保持措施显著影响侵蚀红壤区坡地土壤pH值和有机质、全氮、碱解氮、全磷、速效磷的含量,但是对全钾和速效钾含量影响不显著。牧草和耕作措施可以显著提高土壤pH值和有机质、全氮、碱解氮、全磷、速效磷的含量,显著改善土壤肥力状况,梯田对土壤肥力状况影响不显著。研究区土壤肥力状况不受钾素限制,可以将土壤有机质作为衡量土壤肥力状况的简化指标。     

鲁中南山丘区耕地地力的遥感反演模型与应用

耕地地力是耕地生产能力的重要表征，地力的遥感快速准确反演是耕地资源利用管理的客观需求。该研究针对鲁中南山丘区，选择东平县和滕州市2个代表性县市，利用东平县的TM影像构建与筛选光谱指标，通过经典统计分析（一元线性回归、曲线回归、多元逐步线性回归）和机器学习（BP神经网络、极限学习机）方法构建与优选反演模型，进而在滕州市进行模型的验证和应用，同时对不同时相的反演模型进行了比较分析。结果表明：5类光谱指标与耕地地力综合指数均有显著的相关性，其中改进型光谱指数的r均大于0.684，能更好的反映耕地地力状况；最佳反演模型为经典统计分析方法中的IIG-MLSR 模型（Rv2=0.684，RMSE=5.674）和机器学习算法的IIG-BPNN模型（Rv2=0.746，RMSE=5.089）；模型在山丘区具有较好的普适性，地力反演与评价的结果具有相似的空间分布特征、相近的耕地面积比例和较高的空间契合度。其中2个最佳模型的高中低3级耕地的面积比例差普遍低于5.55%，空间契合度分别为84.50%和88.76%；模型动态反演分析结果显示，2007-2016年滕州市耕地地力不断提升，高级地由67.30%增加至80.72%；不同时相模型比较结果显示，多时相遥感反演耕地地力具备可行性，4月份冬小麦返青拔节期是反演的最佳时相，10月份裸土时相次之，8月份夏玉米时相最差。该研究提出了山丘区耕地地力快速定量遥感反演的有效方法，对完善遥感反演指标与模型，提高评价效率有参考价值。     

长武试区耕地生产潜力和人口容量估算

以长武农业生态试验区为例,采用地块为计算单元,探讨黄土高原沟壑区小区域范围内土地生产力估算。通过对各地块光、热、水、肥等生态因子对小麦、玉米两个主要作物产量效应分析,计算了试验区耕地生产潜力。并且结合试验区人口及人口消费资料,估算出试验区人口容量。     

Soil Fertility Characteristics and Organic Carbon Stock in Soils of Vegetable Gardens Compared with Surrounding Arable Land at the Center of the Urban and Industrial Area of Ruhr,Germany

Soil fertility is the basis for production of high green mass, which has numerous essential benefits in urban areas. This study aimed to investigate the soil fertility of urban land. This was done by comparing soils from a vegetable garden and its surrounding arable land. A local brickwork dump was included. The soils were Hortisols, slightly stagnogleyic Luvisols, and a Regosol from sandy loamy silt. The location of the study was in the center of one of the world’s largest urban, hard-coal mining and heavy industry areas, the Ruhr area in Germany. The investigations for identifying the characteristic features of the soil fertility involved determination of the profile horizons, texture, pH, bulk density, C/N ratio, content and stocks of organic carbon, total nitrogen, available phosphorus and potassium, and soil water by field capacity. As they are expected to become construction land, the sites were already in a derelict state. The results show that all three soil types had high fertility characteristics. However, the fertility of the garden soils was much greater than that of the local arable land. This was due to the strong and deep accumulation of organic carbon due to compost application. The available phosphorus and potassium contents and field capacity were also distinctly increased in the garden soils. The spatial distribution and distribution with depth of pH, bulk density, organic carbon, nitrogen, available phosphorus, and potassium were extremely heterogeneous among the individual garden soils. In contrast, in the arable land, they were uniform. The organic carbon accumulation in the dump was in the range of that of the garden soils, but the nutrient contents were lower. These results show that the diversity of properties of urban soils is much higher than that of arable soils. The dereliction of arable, garden, and dump soil and vegetation by bushes and trees also affect the soil properties. There should be greater awareness of the high fertility of urban soils, such as vegetable garden soils. Vegetable garden soils have a high potential for contributing to solving urban problems by producing high volumes of biomass and storing water. Therefore, it should be demanded that vegetable garden soils receive a high protection status, and they should not be used for the establishment of construction.