表土剥离对土地整治项目收益的影响研究

为了揭示表土剥离对土地整治项目收益的不同影响，作者采用采样分析、调查问卷、地统计分析、空间分析等方法对这种影响进行了分析。研究表明，表土剥离是土地整治工程必不可少的一步。通过土壤质量空间分布和作物投入一产出值比较分析，土地整治可有敬减少农业生产成本，而表土剥离可最大限度地保护土壤表层，通过追肥和田间管理，在2—3年时间可基本恢复耕地肥力。     

PREDICTIVE ASSESSMENT OF SEVERITY OF AGRICULTURAL DROUGHTS BASED ON AGRO-CLIMATIC FACTORS1

ABSTRACT: Past historical evidence indicates that droughts have had great impacts on human life. Drought (or scarcity of water) is assessed based on two key factors, namely, the estimated water demand, and the expected water supply. The formulation of these key factors for a region largely depends on the agro-climatic and economic conditions. Consideration of one such key factor is the relationship between the crop yield and water deficit in the assessment and prediction of agricultural droughts. The varying nature of this relationship from crop to crop adds to the complexity of agricultural drought analysis. To overcome this difficulty in analyzing agricultural droughts of a region, it is adequate to consider and place emphasis on a single crop (i.e., an index crop) grown homogeneously over the major area of the region. From one year to another year, the pattern of water requirement during the growing season of an index crop is rather stationary, and the water supply in arid and semi-arid area is mainly from seasonal random precipitation. In a region, grain yield of the index crop and, in turn, assessment of the severity of drought can reasonably be predicted as a function of the time of crop sowing and the distribution of rainfall, provided that temporal and spatial effects of other contributing factors (crop variety, soil fertility status, crop disease, pest control, cultivation practices etc.) on grain yield are considered to be uniformly distributed (i.e., stable). A predictive method of assessing agricultural droughts in an arid area of western India is presented. The major crop (Pearl Millet) of this region is grown from. July through September. The formulation of the proposed predictive method inherently implies that the grain yield of the main crop is a reliable indicator of agricultural drought. In the development of this predictive relationship (i.e., a regression type model) a number of potential yet simple variables affecting the grain yield in the region were investigated. The soil moisture index, although generally considered significant compared to the simple variables, has been found to account for insignificant variation in the grain yield. Results of our investigations suggest that it would be advisable to exclude the soil moisture index variable from the model. The proposed regression model can be used in the prediction of grain yield of the main crop several months ahead of crop harvesting operations and, in turn, the assessment of agricultural drought severity as mild, moderate, or severe. Such an assessment is expected to be helpful to planners for arranging appropriate measures to effectively combat agricultural drought situations.     

Farmland damage and its impact on the overlapped areas of cropland and coal resources in the eastern plains of China

The subsidence caused by coal mining in areas where cropland and coal resources overlap in the eastern plains of China with high ground water levels has caused large amounts of water to collect in cropland, significant damage to cropland, and a sharp contradiction between people and land distribution within this region. Systematic analysis and calculation were conducted on these areas by using GIS spatial overlay analysis technology, subsidence and occupied cropland estimation models, and crop yield reduction prediction model to reveal the overlapped characteristics and extent of farmland damage, as well as to evaluate the effects of farmland damage to grain yield, farmland landscape, agricultural population, and dynamical equilibrium of the total cultivated land. Results showed that the overlapped areas of cropland and coal resources on the eastern plains of China occupied an area covering 1.33 × 10⁵ km², which accounted for 31.93% of the total cropland area. In 2020, the accumulative total area of destroyed cropland reached 3.83 × 10³ km², thus reducing grain yield by 9.63 × 10⁸ kg, and increasing the number of landless farmers to 1.91 × 10⁶. Furthermore, the quality and production capacity of cultivated land decreased, farmland landscape patterns changed, land patterns and structures were adjusted, the dynamical equilibrium of the total cultivated land was difficult to guarantee, and social instability increased in coal mining subsidence areas. These findings provided a scientific basis for relevant government departments to enact countermeasures for the coordinative production of coal and grain.     

我国粮食生产的耕地资源环境效应特征与代价分析

我国粮食产量逐年增长,但伴随形成的水土资源消耗和耕地环境负荷令人担忧。本文综述了近年来我国粮食生产的耕地资源环境效应基本情况,总体结论是化肥、农药、地膜等农业投入品过量使用所带来的环境负荷日趋严重。同时,对休耕模式和粮食主功能区调整这两项国家战略政策的资源消耗与环境效应进行了重点分析,建议逐步扩大在水资源超采区、重金属污染区、生态退化区等典型区域的休耕面积,积极谨慎地评估主功能区调整形成的潜在资源消耗缓解与环境效益提升作用。提出:改变以牺牲耕地资源环境为代价换取粮食持续增长、建立以资源环境效应评估为平衡点的粮食供需模式的时机已成熟,粮食生产的耕地资源环境效应,应纳入国家粮食战略安全保障整体计划中。     

基于农户视角的粮食主产县耕地健康评价与诊断--以湖南省湘阴县为例

耕地健康关乎国家粮食安全。依据PSR理论模型构建耕地健康评价指标体系,利用湖南省岳阳市湘阴县农户调查数据,运用层次分析法、TOPSIS法和障碍度模型评价了该县耕地健康状况并诊断其障碍因子。结果表明:湘阴县耕地健康综合指数为0.488,耕地健康等级为中度亚健康;耕地健康压力指数、状态指数和响应指数依次分别为0.597、0.526和0.418;轮作休耕、种植绿肥、单位播种面积有机肥施用量、粮食单产、耕作层厚度、单位播种面积化肥施用量、灌溉保证率是制约湘阴县耕地健康的主要障碍因子。     

Analysis of livelihood security: a case study in the Kali-Khola watershed of Nepal

This paper examines household livelihoods in highland and lowland communities of the Kali-Khola agricultural watershed in western Nepal on the basis of economic, ecological and social security indicators. Significant differences were found in soil fertility status, pests and diseases management, risk and uncertainties, use of agrochemicals and access to social services. No remarkable variations were found in crop diversification, annual agricultural income and food sufficiency. However, uncertainty and risk in agricultural production is relatively low in highland communities. The findings reveal that agriculture production alone is not a viable livelihood option for agricultural watershed communities in Nepal. The households growing crops with hired labour have relatively sustainable livelihoods in Nepal's agricultural watersheds. Insufficient agricultural land, insufficient working manpower within a family, and lack of access to ecological agricultural services are prime factors in being livelihood insecure in agricultural watershed communities. Therefore, long-term policies and plans need to be developed for the empowerment of local farmers and to support rural livelihoods with adaptable and flexible income-generating strategies, resilient resource management institutions and enhancement of knowledge, skills and social capital.     

耕地细碎化对粮食产量的影响——以河南省焦作市为例

利用河南省焦作市263个农户的实地调查数据，详细分析了耕地细碎化和耕地规模对粮食产量的影响。研究表明：①耕地细碎化导致粮食产量下降，增加农户的耕地总面积或者扩大地块面积则有助于提高粮食产量；②粮食产量受地形条件和土质的影响较大，受耕地细碎化的影响相对较小；③焦作地区农户的耕地规模普遍较小，平原区和河滩区的粮食产量受耕地细碎化的影响不显著，丘陵区耕地细碎化对粮食产量呈负面影响，因此建议降低耕地细碎化。     

Challenging established narratives on soil erosion and shifting cultivation in Laos

The official environmental discourse in Laos describes a “chain of degradation” stretching from upland shifting cultivation, increased runoff and soil erosion to the siltation of wetlands and reservoirs. This perspective has had wide‐ranging impacts on rural development policy which, in the uplands, has long favoured forest conservation over agriculture. Integrating soil erosion and water sediment data with local perceptions of land degradation in an upland village of northern Laos, this study tests the validity of the official environmental discourse. Biophysical measurements made in a small agricultural catchment indicate a significant correlation between the spatial extent of cultivation and soil erosion rates. However, sediment yields recorded at the outlet of the catchment highlight relatively low levels of off‐site sediment exportation. Furthermore, farmers' perceptions suggest that local land degradation issues and crop yield declines could be less related to soil erosion than to agricultural land shortage, increased weed competition, and fertility losses resulting from the intensification of shifting cultivation. The study concludes that a better understanding and management of land degradation issues can be achieved by developing more inclusive and scientifically‐informed approaches to environmental perceptions and narratives.     

Effects of Land Management Change on Spatial Variability of Organic Matter and Nutrients in Paddy Field: A Case Study of Pinghu,China

The Household Responsibility System initiated in the late 1970s in China has brought a profound change to its rural economy. The shift from the collective farming system to individual family farms has changed land management. The change, including fertilization and crop systems, may have significant effects on soil quality and agro-environmental sustainability. However, very little research is being carried out on the impact of reformed land tenure systems on the spatial variability of soil nutrients. In this study, geostatistics was applied to analyze changes in the spatial variability of soil organic matter and nutrients in paddy fields in Pinghu County, China after 20 years of land management change. In 1984 and 2002, 617 and 131 locations were selected, respectively, for collecting surface soil samples to analyze soil organic matter (SOM), total nitrogen (TN), available phosphorus (AP), and available potassium (AK). From 1984 to 2002, variability of the SOM and TN changed from strongly to moderately spatial-dependent, and the variability of AP remained weakly dependent on space, but that of the AK changed from moderately to weakly spatial-dependent. That the trend of the variability of four soil properties in 2002 became weaker than that in 1984 showed that the extrinsic factors (soil management practices, such as fertilization) weakened the effect by intrinsic factors (soil formation factors, such as soil parent materials) owing to a long period of land management change. The temporal geographic maps of the SOM and nutrients spatial distributions suggested that the concentrations of the SOM and nutrients had been changed to different extents during the period. Significant increase in AP and decrease in AK were noted. The changes were likely due to the imbalance between N, P, and K fertilizers and increased grain yield.     

Expansion of the MANAGE Database with Forest and Drainage Studies

The “Measured Annual Nutrient loads from AGricultural Environments” (MANAGE) database was published in 2006 to expand an early 1980s compilation of nutrient export (load) data from cultivated and pasture/range land at the field or farm scale. Then in 2008, MANAGE was updated with 15 additional studies, and nitrogen (N) and phosphorus (P) concentrations in runoff were added. Since then, MANAGE has undergone significant expansion adding N and P water quality along with relevant management and site characteristic data from: (1) 30 runoff studies from forested land uses, (2) 91 drainage water quality studies from drained land, and (3) 12 additional runoff studies from cultivated and pasture/range land uses. In this expansion, an application timing category was added to the existing fertilizer data categories (rate, placement, formulation) to facilitate analysis of 4R Nutrient Stewardship, which emphasizes right fertilizer source, rate, time, and place. In addition, crop yield and N and P uptake data were added, although this information was only available for 21 and 7% of studies, respectively. Inclusion of these additional data from cultivated, pasture/range, and forest land uses as well as artificially drained agricultural land should facilitate expanded spatial analyses and improved understanding of regional differences, management practice effectiveness, and impacts of land use conversions and management techniques. The current version is available at www.ars.usda.gov/spa/manage-nutrient .     

PREPLANTING SOIL MOISTURE USING PASSIVE MICROWAVE SENSORS1

ABSTRACT: Accurate assessment of preplanting soil moisture conditions is necessary for good agricultural management, and can have a significant influence on crop yield in the Texas Panhandle region. The Texas High Plains Underground Water Conservation District invests considerable time and money in developing a soil moisture deficit map each year in the hopes of achieving optimal use of irrigation water. Microwave sensors are responsive to surface soil moisture and, if used in this application, can provide timely and detailed information on root zone soil moisture. For this reason, an experiment was conducted in 1984 to evaluate the potential of aircraft-mounted passive microwave sensors. Microwave radiometer data were collected over a 2700 km² area near Lubbock, Texas, with a processed resolution of 0.32 km². These data were ground registered and converted to estimates of soil moisture using an appropriate model and land cover and soil texture information. Analyses indicate that the system provides an efficient means for mapping variations in soil moisture over large areas.     

基于农用地分等成果的产能核算——以湖南、河南、黑龙江为例

研究目的:分析农用地质量与粮食生产能力之间的关系。研究方法:主要应用样点的标准粮产量与土地利用等别指数进行回归分析,根据回归分析所得的线性关系推算出3省的粮食总产量。研究结论:通过农用地分等成果进行产能核算具有一定的科学性,可在已经进行农用地分等的省份进行推广应用。     

论我国耕地保护与粮食安全

耕地资源关系到国家经济发展、社会稳定和粮食安全。对我国而言，经济飞速增长，人地矛盾十分突出，每寸土地都显得弥足珍贵。在收集我国1997-2005年耕地面积变化的资料，并作相关分析的基础上，研究得出我国耕地资源呈现不断减少的趋势，其中生态退耕和非农建设用地占用耕地是其变化的主要原因。耕地资源的减少引起了粮食总产量和单产量的变化，而耕地复种指数也是影响耕地产量的主要原因之一。在此基础上分析了耕地保护和粮食安全的内在关系，并提出适合我国的耕地资源可持续利用与粮食安全的措施。     

Using soil moisture and spatial yield patterns to identify subsurface flow pathways

Subsurface soil water dynamics can influence crop growth and the fate of surface-applied fertilizers and pesticides. Recently, a method was proposed using only ground-penetrating radar (GPR) and digital elevation maps (DEMs) to identify locations where subsurface water converged into discrete pathways. For this study, the GPR protocol for identifying horizontal subsurface flow pathways was extended to a 3.2-ha field, uncertainty is discussed, and soil moisture and yield patterns are presented as confirming evidence of the extent of the subsurface flow pathways. Observed soil water contents supported the existence of discrete preferential funnel flow processes occurring near the GPR-identified preferential flow pathways. Soil moisture also played a critical role in the formation of corn (Zea mays L.) grain yield patterns with yield spatial patterns being similar for mild and severe drought conditions. A buffer zone protocol was introduced that allowed the impact of subsurface flow pathways on corn grain yield to be quantified. Results indicate that when a GPR-identified subsurface clay layer was within 2 m of the soil surface, there was a beneficial impact on yield during a drought year. Furthermore, the buffer zone analysis demonstrated that corn grain yields decreased as the horizontal distance from the GPR-identified subsurface flow pathways increased during a drought year. Averaged real-time soil moisture contents at 0.1 m also decreased with increasing distance from the GPR-identified flow pathways. This research suggests that subsurface flow pathways exist and influence soil moisture and corn grain yield patterns.     

中国区域粮食生产与消费中的虚拟耕地平衡研究

从不同尺度分析了我国2008年粮食生产、消费中的虚拟耕地含量及虚拟耕地平衡空间分布规律.主要结论为:①2008年粮食生产虚拟耕地北方比南方多32396.8×107m2,人均粮食生产虚拟耕地量北方远远高于全国平均水平和南方,因粮食生产形成较为典型的虚拟耕地“北土南调”现象.②2008年粮食消费虚拟耕地北方比南方多6851.62×107m2.③从粮食生产与消费的虚拟耕地平衡空间分布规律来看,2008年虚拟耕地调出区全部位于我国北方地区,集中分布在两大地带:一是由黑龙江、吉林、内蒙古、新疆、宁夏5省(区)组成的我国北方边境沿线地带,二是由河南、安徽组成的中部区;调入区则集中在由东部沿海地区、中部省份和西部内陆省份组成的环状地带.     

Enhancing the Ability of a Soil Moisture‐based Index for Agricultural Drought Monitoring by Incorporating Root Distribution

Agricultural drought differs from meteorological, hydrological, and socioeconomic drought, being closely related to soil water availability in the root zone, specifically for crop and crop growth stage. In previous studies, several soil moisture indices (e.g., the soil moisture index, soil water deficit index) based on soil water availability have been developed for agricultural drought monitoring. However, when developing these indices, it was generally assumed that soil water availability to crops was equal throughout the root zone, and the effects of root distribution and crop growth stage on soil water uptake were ignored. This article aims to incorporate root distribution into a soil moisture‐based index and to evaluate the performance of the improved soil moisture index for agricultural drought monitoring. The Huang‐Huai‐Hai Plain of China was used as the study area. Overall, soil moisture indices were significantly correlated with the crop moisture index (CMI), and the improved root‐weighted soil moisture index (RSMI) was more closely related to the CMI than averaged soil moisture indices. The RSMI correctly identified most of the observed drought events and performed well in the detection of drought levels. Furthermore, the RSMI had a better performance than averaged soil moisture indices when compared to crop yield. In conclusion, soil moisture indices could improve agricultural drought monitoring by incorporating root distribution.     

Spatial Analysis of Soil Salinity and Soil Structural Stability in a Semiarid Region of New South Wales,Australia

Salt-affected soils are a major threat to agriculture especially in the semiarid regions of the world. The effective management of these soils requires adequate understanding of not only how water and, hence, solutes are transported within the soil, but also how soil salinity and sodicity spatially interact to determine soil structural breakdown. For sustainable agricultural production, information on quantitative soil quality, such as salinity, is required for effective land management and environmental planning. In this study, quantitative methods for mapping indicators of soil structural stability, namely salinity and sodicity, were developed to assess the effect of these primary indicators on soil structural breakdown. The current levels of soil salinity, as measured by electrical conductivity (EC) of the soil/water suspension, soil sodicity, represented by exchangeable sodium percentage (ESP), and aggregate stability, were assessed. Remote sensing, geographical information system (GIS), and geostatistical techniques-primarily regression-kriging and indicator-kriging-were used to spatially predict the soil sodicity and salinity. The patterns of salinity (EC) and sodicity (ESP > 5%) were identified. The effect of land use on these soil quality indicators was found to be minimal. Co-spatial patterns were elucidated between sodic soils (defined by ESP > 5%) and highly probable mechanically dispersive soils predicted from indicator-kriging of ASWAT scores. It was established that the incorporation of EC with ESP into an objective index, called electrolyte stability index (ESI = ESP/EC), gave a good indication of soil dispersion, although the threshold ESI value below which effective structural breakdown might occur is 0.025, which is twice as small as the expected 0.05. The discrepancies between ESI and ASWAT scores suggest that other soil factors than salinity and sodicity are affecting soil structural breakdown. This calls for further investigation. The study provides valuable information in the form of risk zones of soil structural breakdown for land management. These zones, with a probability of mechanical soil dispersion of >0.70, require immediate management attention with greater monitoring and amelioration techniques, particularly gypsum or lime application and/or altered cultivation techniques.     

Factors affecting the spatial pattern of nitrate contamination in shallow groundwater

The elevated level of nitrate in groundwater is a serious problem in Korean agricultural areas. To control and manage groundwater quality, the characterization of groundwater contamination and identification of the factors affecting the nitrate concentration of groundwater are significant. The characterization of groundwater contamination at a hydrologically complex agricultural site in Yupori, Chuncheon (Korea) was undertaken by analyzing the hydrochemical data of groundwater within a statistical framework. Multivariate statistical tools such as cluster analyses and Tobit regression were applied to investigate the spatial variation of nitrate contamination and to analyze the factors affecting the NO3-N concentration in a shallow groundwater system. The groundwater groups from the cluster analysis were consistent with the land use pattern of the study area. The clustered group of a gentle-slope area with lower elevations showed higher NO3-N contamination of groundwater than groups on a hillside with higher elevations. Tobit regression results indicated that the agricultural activity in the vegetable fields and barns were the major factors affecting the elevated NO3-N concentration while the land slopes and elevations were negatively correlated with the NO3-N concentration. This shows that topographic characteristics such as land slopes and elevations should be considered to evaluate the land use impact on shallow groundwater quality.     

Basic principles of agroecology and sustainable agriculture

In the final analysis, sustainable agriculture must derive from applied ecology, especially the principle of the regulation of the abundance and distribution of species (and, secondarily, their activities) in space and time. Interspecific competition in natural ecosystems has its counterparts in agriculture, designed to divert greater amounts of energy, nutrients, and water into crops. Whereas natural ecosystems select for a diversity of species in communities, recent agriculture has minimized diversity in favour of vulnerable monocultures. Such systems show intrinsically less stability and resilience to perturbations. Some kinds of crop rotation resemble ecological succession in that one crop prepares the land for successive crop production. Such rotations enhance soil organic processes such as decomposition and material cycling, build a nutrient capital to sustain later crop growth, and reduce the intensity of pest buildup. Species in natural communities occur at discrete points along the r-K continuum of reproductive maturity. Clearing forested land for agriculture, rotational burning practices, and replacing perennial grassland communities by cereal monocultures moves the agricultural community towards the r extreme. Plant breeders select for varieties which yield at an earlier age and lower plant biomass, effectively moving a variety towards the r type. Features of more natural landscapes, such as hedgerows, may act as physical and biological adjuncts to agricultural production. They should exist as networks in agricultural lands to be most effective. Soil is of major importance in agroecosystems, and maintaining, deliberately, its vitality and resilience to agricultural perturbations is the very basis of sustainable land use.