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Copyright of Advanced Engineering Science / Gongcheng Kexue Yu Jishu is the property of Advanced Engineering Science Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Boolean functions are cryptographic functions that have been widely used in the fields of cryptography, error correction coding, and spread spectrum communication. Finding good performance Boolean functions has always been one of the important issues in the field of cryptography. Based on the gravitational search algorithm, this paper designed a new algorithm for searching Boolean functions. This algorithm imitated the law of universal gravitation, used the mass points in n-dimensional space to represent the Boolean function, and used the cryptographic characteristics of the Boolean function as the target fitness function for searching. The experimental results show that by changing the newly designed target fitness function, a balanced Boolean can be directly generated that meets a variety of cryptographic indicators such as 1-order resilient, 1-order propagation, or high non-linearity, high algebraic number, and low auto correlation index function. Further more, this paper implemented a computer search algorithm that directly generated a 2-output balanced Boolean function. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper takes Gaobeidian City of Hebei Province as the research area. Based on the Landsat TM/OLI data from 1999 to 2001, 2007-2009 and 2015-2017, the CART decision tree classification method is used to extract the distribution of abandoned arable land in the study area. Finally, we analyze its spatial pattern change characteristics and influencing factors. The study draws the following conclusions: 1) Using CART decision tree classification method to interpret remote sensing images in Gaobeidian City and verify the accuracy. The result shows that: 1）the classification accuracy of 18-stage images are between 87.5% and 96.4%, which can meet the accuracy requirements of this study; 2) The type of abandoned arable land in Gaobeidian City is mainly seasonal abandonment. The area of abandoned arable land reached 21 888.42 hm2 in the spring of 2001, and the area of seasonal abandoned arable land and perennial abandoned arable land are gradually decreasing; 3) The analysis of landscape indicators including plaque number (NP), average plaque area (MPS), median plaque area (PSMD), plaque area standard deviation (PSSD), and average shape index (MSI) of the abandoned arable land shows that the main form of the abandonment of arable land has changed from large-scale centralized abandonment to small-scale decentralized abandonment; 4) The development of rural industry is the main driving factor leading to the abandonment of arable land. The result of the buffer analysis shows that the closer the industrial center is, the higher the comprehensive abandonment rate; The traffic conditions and farming radius also affect the abandonment of arable land to a certain extent, but in the flat plains region, its impact gradually weakened; 5) The gap in crop yields leads to seasonal differences in the cultivated land reclamation in Gaobeidian City. The long-term low net income per unit area of wheat is the main factor leading to the large-scale spring abandonment of arable land in Gaobeidian City, and the arable land transfer can effectively inhibit the abandonment of arable land. The results of rural survey show that the arable land transfer rate in the six surveyed villages shows a significant negative correlation with the change of the arable land abandonment rate. Due to the low resolution of remote sensing images used in this study, the interpretation accuracy may be affected. In addition, the selection time of remote sensing images is mainly based on the growth of spring wheat and summer maize, which do not take into account the late planting of summer stubble carrot and other crops in different growth periods. Although the sowing area of such crops is small, it may still cause errors in the interpretation of abandoned arable land. In order to solve the above problems, it is necessary to use Google high-resolution image for manual visual interpretation and correction, but this method will cost a lot of manpower and time. In future research, other remote sensing data sources with higher spatial resolution and richer spectral information can be considered for interpretation in order to solve these problems. The research results can provide reference for the study of abandoned arable land in other similar areas in China, and provide basis for the formulation of national food security and regional sustainable development policies. [ABSTRACT FROM AUTHOR]

At present, there are still a large number of poverty-stricken counties in the western part of China. Although the government has recently increased financial support for rural areas, and the policy guidelines have been steadily tilting toward rural areas, especially poor rural areas, rural poverty is still difficult to resolve. In order to reasonably determine the optimal layout direction of rural settlements in poor mountainous areas, and put forward some scientific guidance in the rural land remediation and new rural construction in mountainous areas, this paper took Xundian Hui and Yi Autonomous County, a former national poverty-stricken county that was out of poverty in 2018, as a research area, and used the methods of remote sensing interpretation, GIS analysis, landscape shape index model, buffer analysis, Kernel density estimation and Getis-Ord Gi* to study the evolution characteristics and influencing factors of rural settlements in Xundian County from 2001 to 2017 in terms of space, scale and form. The research results showed that: 1) During 2001-2017, there were some changes in the scale, density, shape and spatial distribution of rural settlements in Xundian County. The main changes were as follows: from 2001 to 2017, the overall scale of rural settlements had expanded significantly, the landscape shape tended to be regular, and the average patch size increased; the characteristics of rural settlements clustering in areas with superior terrain were becoming more and more obvious. The analysis results of kernel density and Getis-Ord Gi* showed that the spatial divergence characteristics of rural settlements patch scales were apparent, and the distribution patterns were gradually expanding from small-scale decentralization to large-scale clustering; 2) The natural geographical factors such as geological and topographical conditions were the basic factors that influencing the distribution pattern of rural settlements in mountainous areas. The basic pattern of spatial distribution of rural settlements in mountainous areas is the result of long-term adaptation to topographic and geomorphological conditions; 3) Socio-economic factors, location factors and policy factors were the important factors influencing the change of spatial distribution. As the urban-rural income gap increased, the rural population of Xundian County flew to urban areas, so rural settlements were more concentrated in urban areas; the results of the neighborhood analysis of towns and roads also indicated that rural settlements tended to be concentrated in the distribution of towns and roads. In addition, the precise poverty alleviation policy with relocation as the main means was another major factor leading to the concentration of rural settlements in the plain areas with superior terrain conditions. According to the study, for mountainous rural areas with scarce natural resources, the poverty alleviation in mountainous areas should rely mainly on industrial assistance rather than policy assistance in the future. The local government should focus on increasing the employment opportunities of farmers and improving the livelihood conditions of farmers. Only in this way can we really help the poor and achieve the rural revitalization. This study can provide a practical guidance for the poverty alleviation work in the rural areas of the southwestern frontiers with frequent geological disasters; also provide a scientific theoretical basis for the optimization of the spatial layout of rural settlements. [ABSTRACT FROM AUTHOR]

Desertification is the prominent eco-environmental problem in semi-arid and sandy land area. And land use is the main driving force of desertification. The development process of desertification has been primarily curbed in general but kept expanding in partial locations. At the circumstance, it is significantly beneficial for anti-desertification and ecological restoration to study the cultivated land use characteristics based on cultivated land particles in the semi-arid and sandy land area. Materials applied in this paper included Landsat-8 remote sensing images, land use/cover maps, atmospheric water vapour content, DEM and soil nutrient data. Split window method was used to calculate land surface temperature of cultivated land. And characteristics of land surface temperature of cultivated land and its causes were analyzed. The results showed that the range of land surface temperature of cultivated land was wide. The minimum and maximum of land surface temperature of cultivated land in row/path 030/120 remote sensing image were 294.03 K and 308.61 K. And those in row/path 030/119 remote sensing image were 291.43 K and 310.62 K. The temperature ranges whose cultivated land area accounting for more than 10% of the total cultivated land, included [297 K, 298 K], [298 K, 299 K], [299 K, 300 K], [300 K, 301 K], and [301 K, 302 K] in row/path 030/120 remote sensing image. And those were [300 K，301 K)、[301 K，302 K)、[302 K，303 K)、[303 K，304 K) in row/path 030/119 remote sensing image. The spatial variation of precipitation resulted in a large spatial variation of crop growth condition in Horqin Left Back Banner, which resulted in a large range of land surface temperature of cultivated land. As to the temperature difference of cultivated land particles, land surface temperature range of cultivated land particles in row/path 030/120 remote sensing image was between 0 and 9.56 K and that in row/path 030/119 remote sensing image was between 0 and 10.32 K. This indicated that land surface temperature difference of cultivated land particle was large. Furthermore, the area of cultivated land particles with large land surface temperature difference took a large proportion. The areas of cultivated land particles with land surface temperature difference greater than 3 K in row/path 030/120 and 030/119 remote sensing images took percentages of 36.895% and 57.971% respectively. The areas of cultivated land particles with land surface temperature difference greater than 4 K in row/path 030/120 and 030/119 remote sensing images took percentages of 16.841% and 41.571% respectively. This was attributed to the redistribution of precipitation along dune-interdune and the elevation difference of cultivated land particle. As to the land surface temperature at cultivated land particle margin, among 22107 cultivated land particles in row/path 030/120 remote sensing image, average land surface temperature at the marginal area of cultivated land was greater than that of the cultivated land particle in 13268 cultivated land particles. And among 1644 cultivated land particles in row/path 030/119 remote sensing image, average land surface temperature at the marginal area of cultivated land was greater than that of the cultivated land particle in 866 cultivated land particles. Both areas took percentages of 73.71% and 53.80% respectively in both cultivated land areas. And micro-topography, soil quality and management measures induced this phenomenon. According to the results above, we reckon that grid method should be adopted in cultivated land quality evaluation in semi-arid and sandy land area. Cultivated land at the margin of cultivated land particle should be de-farmed in order to anti-desertification and ecological restoration. [ABSTRACT FROM AUTHOR]

Agro-pastoral ecotone in northern China is fragile in ecology. Desertification is the prominent eco-environmental problem which is mainly induced by unreasonable land use in this area. In the background of ecological civilization construction in China, it is significant to study land suitability for cultivation in the agro-pastoral ecotone in northern China to prompt ecological protection and scientific utilization of land resource. Taking Horqin Left Back Banner as a case study, from the aspects of ecology, production and life, this paper constructed the evaluation index system to evaluate land suitability for cultivation. The results showed that the unsuitable cultivation area in cultivated land in Horqin Left Back Banner was 15996.87 hm2 accounting for 5.339% of total cultivated land area. Owing to ecological, production and living factors, the unsuitable cultivation area of cultivated land were 7 519.23, 9 337.23 and 6 039.99 hm2 and their proportions were 40.78%, 32.84% and 26.38%, respectively. There were 6 unsuitable cultivation types including ecology; production; ecology and production; ecology and life; production and life; ecology, production and life. We reckon that unsuitable cultivation land should be de-farmed firstly in Grain for Green Project. The grass land suitable for cultivation was 197 195.94 hm2 accounting for 32.18% in total grass land area. Namely, about a third of the grass land could be reclaimed into cultivated land in Horqin Left Back Banner. However, it was found that the proportion of high quality grass land suitable for cultivation was very small from perspectives of soil suitability and topographic conditions. From the perspective of soil suitability, the most suitable, the moderate suitable and the low suitable were 26 058.42, 34 347.78, 136 789.74 hm2, accounting for 13.214%, 17.418%, 69.367% of the total grass land suitable for cultivation, respectively. From the perspective of topography condition, when the micro topography index were [1.5, 1.6), [1.6, 1.7), [1.7, 1.8) and [1.8, 1.9) ,the grass land areas were 0.18, 0 2, 8.1 and 277.29 hm2, accounting for 0, 0, 0.004% and 0.141% of the total grass land area suitable for cultivation, respectively. However, when the micro topography index were [1.9, 2.0), [2.0, 2.1), [2.1, 2.2), the grass land area were 82 389.24, 112 996 and 1 525.05 hm2 respectively, accounting for 41.780%, 57.301% and 0.773% of the total grass land area suitable for cultivation. From two aspects of soil suitability and topography condition, the grass land area proportion of soil suitability for most grade and micro topographic index for [1.5, 1.9) was only 0.039% to the total grass land area suitable for cultivation. And the grass land area proportion of soil suitability for most and moderate grade and micro topographic index for [1.5, 1.9) was only 0.085% to the total grass land area suitable for cultivation. In order to avoid the destruction of ecological environment and the expansion of desertification caused by the reclamation of low quality grass land, it is suggested that priority should be given to the high quality reserved cultivated land resource in reclamation and the national coordination should be maintained in cultivated land balance across provincial region. [ABSTRACT FROM AUTHOR]

Recognizing the evolution and transformation progress of rural farmland under different terrain conditions is the basis of modernization management of agriculture, which will also help the targeted poverty alleviation in rural areas. Remote sensing and GIS (geographic information system) technology were used to analyze the farmland use in national-level poverty-stricken county of Horqin Left Wing Rear Banner in the flat area and Youyang County in the mountainous area. The analysis mainly focused on the variation of the quantity, quality, spatial distribution, configuration characteristic, distribution of topographic region and planting structure of farmland land from 2001 to 2015 when there is an enormous amount of migration from rural to urban areas. The results are as follows: 1) Compared with the mountainous county, the farmland per capita labor is more abundant in the plain county, but continuous expansion of farmland still occurs in the flat county while the shrink exists in the mountainous county. 2) The farmland quality of poverty-stricken county in the flat area is generally low and the inferior farmland changes obviously, by contrast, in the mountainous county, it is higher and the farmland of low and middle quality increases obviously. 3) The distribution of farmland in these 2 counties tended to cluster together; the farming radius in the flat county was expanding but it shrank in the mountainous county. The number of farmland patches and largest patch index increased in the flat county, while the number of farmland patches declined sharply and the largest patch index increased a little in the mountainous one. The mean patch size of farmland in the flat county was much larger than that in the mountainous county, but varying degrees were both increased. There was a raise of area-weighted patch fractal dimension of farmland in the flat county but a reduction in mountainous county. In the flat county, the low terrain niche range was the priority areas for development of farmland and there existed no significant change, while the middle-low terrain niche range was not the priority areas for development of farmland in the mountainous county. Meanwhile the advantage degree of farmland increased in the middle-low terrain niche range. 4) Generally, farmers in the flat counties prefer to plant food crops which are land-intensive agricultural products because of the man-earth relationship of wide land and few people, while commercial crops with greater weight are planted in mountainous county by contrast because of big population holding little tillable land. The results show that terrain and farmland resource are the critical factors influencing the difference of comparative advantage of regional production, which, to some extent, makes the pattern of farmland use and agricultural production various. Therefore, the investment and policy-making for agricultural modernization and targeted poverty alleviation must make the best use of the circumstances. The agricultural development mode in flat areas should change from extensive use of resources to protective utilization, so as to avoid the phenomenon of “land reclamation along with land desertification”, which causes the soil desertification and the farmland quality decline. The development of agriculture in mountainous areas must change the traditional agricultural production mode to improve agriculture multifunction for the more value of “land economic output per unit area” through technological reformation and marketization. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Water resource is the key factor affecting dry land maize growth in semi-arid and sandy land area. These areas are fragile in eco-environment and unreasonable land use has induced serious land desertification. So, it is significant to study crop growth status under different precipitations and to identify the unstable cultivated land for eco-environment rehabilitation in semi-arid and sandy land area. Taking Horqin Left Back Banner as a case study, firstly, this paper analyzed the precipitation types of maize growth period from 1980 to 2013 with precipitation data of Horqin Left Back Banner Weather Station. Secondly, dry land maize growth status was studied with the method of remote sensing technology and the crop production stability was analyzed. Thirdly, unstable cultivated land identification was performed according to dry land maize growth status under normal precipitation year and partially dry year. The results indicated that proportions of dry year, partially dry year, normal year, partially wet year, and wet year were 11.77%, 29.41%, 17.65%, 32.35%, and 8.82% respectively. The proportions of partially wet year and wet year, partially dry year and dry year were large. Precipitation fluctuation in maize growth period was dramatical in Horqin Left Back Banner. The sum of normalized difference vegetation index (NDVIsum) of cultivated land in partially dry year (2001), normal year (2013), and partially wet year (2008, 2012) were mostly distributed in [4，4.5), [4.5，5.5) and [4，5) respectively. There were big gaps in dry land maize growth condition in different precipitation types of maize growth period. In general, dry land maize growth status in partially dry year was worse than that under normal year. Precipitation in semi-arid and sandy land area could not meet the demand of dry land maize growth. And precipitation in partially dry year was less than normal year. These reasons made dry land maize growth in partially dry year worse than that under normal year. Dry land maize growth under normal year was better than that under partially wet year. Micro-terrain made the redistribution of precipitation and the cultivated land distributed at low terrain would be in waterlogging in much precipitation condition. So, dry land maize growth under partially wet year was worse than that under normal year. Dry land maize growth under partially dry year was worse than that under partially wet year. Area of cultivated land distributed on high terrain was larger than that on low terrain, and compared with the waterlogging, drought had a more wide effect on dry land maize growth. So, dry land maize growth under partially dry year was worse than that under partially wet year. According to the precipitation types and dry land maize growth status, crop production is unstable in semi-arid and sandy land area. Based on the difference of dry land maize growth under normal year and partially dry year, cultivated land was grouped into 4 types: extremely unstable cultivated land, unstable cultivated land, relatively stable cultivated land, and stable cultivated land. The areas of extremely unstable cultivated land and unstable cultivated land were 68.75 and 33918.75 hm2 respectively. By this study, the understanding of agricultural production in semi-arid and sandy land area has been deepened. Drainage facilities or water storage facilities should be constructed in low-lying area in semi-arid and sandy land area to avoid the effect of waterlogging on crop growth. Extremely unstable cultivated land and unstable cultivated land should be changed to achieve ecology restoration. [ABSTRACT FROM AUTHOR]

More and more people immigrated into metropolises, resulting in the increase of food consumption and waste production. Human waste contains a lot of nutrients, and above all, night soil is the most representative. If the night soil does not be treated well timely, it could bring some serious environmental problems within city, especially for the water environment. Taking the plain area in Beijing as the example, we focused on its land use change between 2004 and 2014 by the method of remote sensing; besides, we also estimated nutrient balance in farmlands due to the changes of population and land use; finally, we also researched the change of interface between urban construction land and outside environment by mean shape index. The results were as follows: 1) Compared with 2004, the increase of population and food consumption caused an increase of about 0.34×105 t nitrogen (N), phosphorus (P), and potassium (K) nutrients from human excrement in 2014, and there was a nutrient increment of 282.17 t in night soil sludge after water treatment; 2) Farmland had a strong capacity for nutrient absorption in Beijing, for instance, the grain crop field of winter wheat and spring maize could absorb 820 kg/hm2 per year, and the vegetable filed of rape could absorb 1148 kg/hm2 per year; the decreased farmland area resulted in an about 1.17×105 t loss of nutrient treatment capacity; 3) The decline of mean shape index from 1.48 to 1.37 demonstrated the shrink of construction land contacting boundary, which made the evacuation efficiency of metabolic flow decline. Urban nutrient surplus and resultant serious water pollution were mainly due to the increase of population, food consumption and human metabolites, as well as the decrease of farmland area, construction land contacting boundary extent, and resultant metabolites absorption capacity. According to statistics, there is still half of night soil sludge stacked or buried in suburb areas without harmless disposal, which increases the risk of regional water environment pollution. City is an open system, in terms of the circulation of matter and energy in city with external environment, we reckon that, compared with mononuclear mega-city, polycentric city with more farmland and forest land interlaced with construction land has a higher nutrient liquidity and ecological stability. Therefore, the multi-center urban structure can avoid the accumulation of nutrients in the city in the process of urban development, and it is worth learning from other cities. However, it is very hard to rebuild the urban construction of Beijing, and thus it is of importance to treat the nutrient within the urban area. In order to better treat the ever-increasing nutrient of human metabolites in the urban area, on the one hand, we suggest to recycle and reuse livestock manure and wasted water into farmlands instead of stacking or burying it, which can help to develop green agriculture; on the other hand, given the increase of forest land due to afforestation of city, the use of reclaimed water in green area irrigation can not only decompose the redundant nutrients, but also save water resource. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Natural Resources / Ziran Ziyuan Xuebao is the property of Journal of Natural Resources and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This research used the techniques of the remote sensing (RS) and geographic information system (GIS) to obtain the data of agricultural land use classifications by analyzing and interpreting the multi-spectrum remote sensing images, which were extracted from Landsat TM image in 2004 and Landsat OLI image in 2014. According to the situation of agricultural land use in Beijing plain, the agricultural land use were classified as the grain crop fields, vegetables cultivated in greenhouse, vegetables cultivated in the open fields and forest land. Then it analyzed spatial-temporal change characteristics of the agricultural land use in Beijing plain over the past decade (2004 to 2014) by combination of the quantitative geography model and geographic information system (GIS). The results showed that the grain crop fields were changed into forest land and greenhouse vegetable fields, which was the major trend. The area of grain crop fields changed into forest land was 969.97 km2 whose land use change intensity index was 71.11%, at the top of all kinds of land use change intensity indexes. The area of grain crop fields changed into greenhouse vegetable fields was 163.53 km2 during the past 10 years, whose land use change intensity index was 12.16%, and ranked at the second among all kinds of land use change intensity indexes. Meanwhile the agricultural land use change had spatial characteristic in Beijing plain over the past 10 years. The leading type of agricultural land use changes was that grain crop fields turned into forest land in the suburban area and the distant suburb plain of Beijing, where land use change intensity indexes of grain crop fields into forest land were 84.18% and 76.21%, respectively and higher than the other agricultural land use change intensity indexes obviously. The overwhelming urbanization was encroaching upon a lot of grain crop fields, which leaded the agricultural land use to concentrate on the forest land in the suburban districts. At the same time grain crop fields changed separately to forest land and greenhouse vegetable fields in the new urban area of Beijing, which prompted to the equalization of agricultural land use structure. The research area kept the specific spatial pattern of agricultural land use that the forest land was the leading classification in close proximity to the city center, the mixed classifications including grain crop fields, greenhouse vegetable fields and forest land were main structure in suburban area of Beijing plain and the combination type consisted of grain crop fields and forest land mainly appeared in the distant suburbs of Beijing plain. The spatial structure of the agricultural land use showed as a specific spatial pattern including 3 layer circles and had experienced some changes over the last decade. Firstly, the whole layer circles of agricultural land use had migrated outwards towards the suburbs with the rapid expansion of the central city over the time. Secondly, the spatial distributions of forest land in close proximity to city center and the vegetables cultivated in greenhouse in suburban areas of Beijing plain both had expanded outward due to the area of forest land and vegetables cultivated in greenhouse increased. Although grain crop fields and forest land were the main agricultural land use types in the distant suburbs of Beijing plain in 2004, whose proportion of grain crop fields and forest land had exchanged in 2014. Forest land had become the main type of agricultural land use in the distant suburb of Beijing plain instead of grain crop fields over the time. The study identified that the spatial structure and changes of 3 layer circles of the agricultural land use objectively reflect the different land rent, which drove the peasant household in different locations of suburbs to make different choices about the cultivation, operation and management of agricultural products. Specifically, the peasant households who lived in urban and suburban areas preferred vegetables to grain crops and preferred cultivating vegetables in greenhouse to cultivating vegetables in the open fields, because they hope to get more economic income by changing agricultural products and ways of operation and management. On the other hand, forest land which mainly provided ecological service function was closer to the city center than the grain crop fields which mainly provided production function, which meant the agricultural function had changed from production function mainly to productive and ecological functions. The research results provide a reference for the optimization of spatial distribution of agricultural land use in Beijing plain. [ABSTRACT FROM AUTHOR]

The construction of irrigation and water conservancy was initiated on the North China Plain in the 1950s, which played a significant role in the saline-alkali soil improvement and flood discharge. However, the phenomenon of filling agricultural drainage ditches has become common in the North China Plain since the 1990s. It is necessary to know the condition of filling agricultural drainage ditches and flood disasters related with this phenomenon. Nowadays, there are few researches to analyze the condition of filling agricultural drainage ditches. In order to enrich existing studies, this research took Cangxian County which was battered by flooding and soil salinization in lower plain area as a case study, and explored the condition of filling agricultural drainage ditch and the flood disaster. The changes of drainage ditch area and spatial variation were analyzed based on land use databases of Cangxian County in 1992 and 2010 using the method of GIS (geographic information system). Then, the condition of filling agricultural drainage ditch was investigated by means of the field research in Nan Gutun Village. This village was one of the most densely populated agriculture villages in Cangxian County. Interviewing with the village committee members and the villagers over 70 years old, we learned about the local agricultural production mode, the way of life, the changes of agricultural drainage ditch and its mechanisms from 1960s to now. Finally, we analyzed the risk of flood disasters from the aspects of precipitation trends, percentage of precipitation anomalies, underground water level, drought/flood frequency, relationship between soil water capacity and rainfall, and upland water condition. The results showed that from 1992 to 2010, the area of drainage ditches in Cangxian County reduced by 37.73%. Meanwhile, the proportion of drainage ditches in Cangxian County decreased by 2.03% and the farm ditches was the most serious in being filled. The results of flood disaster analysis showed that the annual precipitation had an obvious downtrend and the seasonal precipitation was evenly distributed. With the underground water level lowering at the average speed of 1-2 m/a, soil water supplement through soil capillarity was decreasing. This made the storage capacity of soil water enlarged before rainy season. Based on soil physics, 1 m water-free soil could contain approximately 140 mm precipitation, which played a significant role in slowing down the surface runoff. At the same time, the actual water flow in the upstream was decreasing. Moreover, China’s rapid urbanization and industrialization is accompanied by a continuous growth of water use, and upland water is mainly used for cities, which results in the decrease of upland water. In consideration of all condition, the risk of flood disasters was reducing according to the precipitation, soil water capacity and upland water. In other words, under the constant climate circumstances, the condition of filling agricultural drainage ditches did not increase the risk of flood in the majority of years. But we found in the field research that the risk of flooding increased after the heavy rain. Based on the results above, we suggest that the government should take terrain, underground water level and soil into consideration in the redesigning of drainage ditch systems, and attain the goal of maintaining high and stable yield of grain, farmland infrastructure protection and requisition-compensation balance of cultivated land through the scientific planning of water conservancy construction and land consolidation. [ABSTRACT FROM AUTHOR]