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Hou S.,China Agricultural University | Huang Y.,China Agricultural University | Huang Y.,Key Laboratory of Arable Land Conservation North China | Shen C.,China Agricultural University | And 3 more authors.
Nongye Jixie Xuebao/Transactions of the Chinese Society for Agricultural Machinery

Zero-tension lysimeters (ZTL) have been widely applied to monitor soil solution flux and solute transport through soil layers in the vadose zone to the ground water under various conditions in research areas, such as the comprehensive utilization of agricultural water and soil resources as well as soil and water environment conservations. A capillary barrier that can cause flow divergence around the system will be created between undisturbed soil and ZTL as the ZTLs are installed in the field. Meanwhile, the water can overcome the capillary barrier and enter into ZTL only when the soil water is saturated above the contact plane of soil and ZTL. Thus, the efficiency of adopting ZTL for water collection decreases correspondingly. To improve the collection efficiency of ZTL, divergence barrier was added to ZTL (ZTLd), and the factors that can affect the collection efficiency of ZTL were examined, such as soil hydraulic property, soil texture, irrigation rate, initial soil water content and height of divergence barrier, and HYDRUS model was adopted. By measuring soil water flux from seepage face in a two-dimensional model and comparing it with applied flux in a one-dimensional model at the same depth, the collection efficiency was obtained. Three soil textures including sandy loam, loam and silt were considered, and the values of van Genuchten model parameters for test soils were not changed in HYDRUS model. Moreover, irrigation rates ranged from 100 mm to 1000 mm, and height of divergence barrier ranged from 0 cm to 70 cm. Two initial soil water contents (i.e. 0.15 and 0.35 cm3/cm3) and two soil evaporation rates (i.e. 0.2 and 0.5 cm/d) were adopted. According to the results, the collection efficiency of ZTL without divergence barrier (ZTL0) was low due to lateral diversion of water above the seepage face. As for the ZTL0 under 1000 mm irrigation rates, the collection efficiencies were 0~11%, 5%~13% and 6%~12% in the sandy loam, loam and silt soil, respectively. Due to the fact that more water was accumulated above the seepage face, the measured soil water flux increased as the divergence barrier was installed. However, the height of divergence barrier was reduced with the increase of irrigation rates as well as the decrease of water holding ability of soil and soil evaporation rates. When the height of divergence barrier was less than 20 cm and irrigation rate reached 1000 mm under the condition of 0.35 cm3/cm3 initial soil water content and 0.2 cm/d soil evaporation rate, the collection efficiency of ZTLd was increased to 50%. Thus, coarse-textured soils, divergence barrier, low soil evaporation rate and high irrigation rates were preferred so as to measure water flux rate accurately by ZTLd. High initial soil water content (0.35 cm3/cm3) would lead to low collection efficiency of ZTLd in sandy loam, and collection efficiency of ZTL at a certain burial depth might not be suitable for other depths. According to the assumption of the study, all simulations were based on homogeneous soil without consideration of preferential flow, thus there was no effect of size on the collection efficiency. In conclusion, the results of this research can exert significance to the improvement of ZTL. ©, 2015, Chinese Society of Agricultural Machinery. All right reserved. Source

Wang B.,China Agricultural University | Wang B.,Key Laboratory of Agricultural Land Quality | Li H.,Beijing Academy of Agriculture and Forestry Sciences | Sun D.,China Agricultural University | Sun D.,Key Laboratory of Agricultural Land Quality
International Journal of Environmental Research and Public Health

The regional management of trace elements in soils requires understanding the interaction between the natural system and human socio-economic activities. In this study, a social-ecological patterns of heavy metals (SEPHM) approach was proposed to identify the heavy metal concentration patterns and processes in different ecoregions of Beijing (China) based on a self-organizing map (SOM). Potential ecological risk index (RI) values of Cr, Ni, Zn, Hg, Cu, As, Cd and Pb were calculated for 1, 018 surface soil samples. These data were averaged in accordance with 253 communities and/or towns, and compared with demographic, agriculture structure, geomorphology, climate, land use/cover, and soil-forming parent material to discover the SEPHM. Multivariate statistical techniques were further applied to interpret the control factors of each SEPHM. SOM application clustered the 253 towns into nine groups on the map size of 12 × 7 plane (quantization error 1.809; topographic error, 0.0079). The distribution characteristics and Spearman rank correlation coefficients of RIs were strongly associated with the population density, vegetation index, industrial and mining land percent and road density. The RIs were relatively high in which towns in a highly urbanized area with large human population density exist, while low RIs occurred in mountainous and high vegetation cover areas. The resulting dataset identifies the SEPHM of Beijing and links the apparent results of RIs to driving factors, thus serving as an excellent data source to inform policy makers for legislative and land management actions. © 2014 by the authors; licensee MDPI, Basel, Switzerland. Source

Xue J.,Land Consolidation and Rehabilitation Center | Xue J.,China Agricultural University | Xue J.,Key Laboratory of Agricultural Land Quality | Han J.,Geological Publishing House | And 5 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering

As the material basis for the development of modern agriculture, well-facilitated capital farmland is the key to ensuring food safety in China By improving the comprehensive productivity of cultivated land and agricultural production conditions, the construction of well-facilitated capital farmland and its effective management and efficient utilization has great significance for food security and the development of modern agriculture. Taking Fujin city of Heilongjiang Province as an example, the paper conducted a study on the well-facilitated capital farmland construction sequence. The main conclusions of the study were as follows: It introduces the Four Quadrant model by a feasibility and spatial stability analysis on a well-facilitated capital farmland construction sequence. It comprehensively determined a well-facilitated capital farmland construction sequence combined with the construction scale and goal orientation. Evaluation of the construction feasibility is mainly used to reflect the feasibility of a well-facilitated capital farmland construction sequence. The evaluation index was selected from three aspects including natural quality, engineering construction, and economic society. It mainly included thickness of effective soil, field area, and the later maintenance funding levels. Spatial stability evaluation is mainly used to reflect the spatial stability after well-facilitated capital farmland is constructed. It selected the distance to the county seat, the distance to the township, the distance to the main roads, the distance to potential geological hazards, population density, local finance income, and other indicators from three aspects including location, ecology, and the construction land expansion force. The cultivated land to be evaluated was divided into three levels including high feasibility, medium feasibility, and low-grade feasibility based on the well-facilitated capital farmland construction feasibility evaluation model. The area of the highly feasible region was 13.18×104hm2 (22.69% of the total evaluation area), it was mainly in the state farms especially in the Qixing Farm and the Daxing Farm. The moderate feasible area was 22.72×104 hm2 (39.13% of the total evaluation area). It was distributed in the state farm and local government areas and the area was equal. It was mainly distributed in the Daxing Farm and the Qixing Farm of the state farms and Jinshan town of the local government; The low feasible area was 22.18×104hm2 (38.18% of the total evaluation area), all are located in the local government's area except for a little distribution in Qianjin Farm. On the issue of space stability, the area of highly stability, area of moderate stability, and area of low stability of well-facilitated capital farmland construction in Fujin City was 7.58×104hm2, 27.73×104hm2 and 22.77×104hm2. It occupied respectively 13.06%, 47.73%, and 39.21% of the evaluation area. Highly stable areas were mainly distributed in the farm on the east of Fujin city; moderate stability areas were mainly distributed in the local towns in the south and west of Fujin city; and low stability areas were mainly distributed in the township in the western northern and central areas of Fujin city. The unstable areas were mainly distributed in the Songhua River, Sanhuanpao Nature Reserve, and some important areas of the rivers and city construction expansion area. It was coupled to the feasibility and spatial stability of well-facilitated capital farmland construction by the Four Quadrant model. It determined the well-facilitated capital farmland construction sequence based on the goal orientation of spatial stability priority. Qixing Farm, Hongwei Farm, Qianjin Farm, and Qinglongshan Farm are priority areas of well-facilitated capital farmland construction. Source

Yu X.,University of Science and Technology of China | Yu X.,Key Laboratory of Agricultural Land Quality | Wu K.,University of Science and Technology of China | Wu K.,Key Laboratory of Agricultural Land Quality | And 8 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering

Modern agriculture is the foundation of national economic and social development, and because of its close correlations with nature, the landscape ecological security of modern agricultural region plays an important role in China's ecological reconstruction. The concept of landscape ecological security (LSES) can be described in both special and general ways. Based on the special definition, LSES is evaluated by the level of natural or human disturbance and the vulnerability of each landscape type in typical model. In this model, the level of disturbance is basically measured by landscape pattern indexes such as landscape fragmentation, isolation, dominance and diversity. The vulnerability of each type of landscape is mostly decided by expert experiences. Thus, the disadvantage of typical LSES evaluation model is that it cannot evaluate the ecological effects of the change of landscape types. Based on the general definition of LSES, some studies introduce P-S-R model on LSES evaluation. The advantage of P-S-R model is that it offers a wider range of index options. However, some of these indexes are based on economic and social statistic data, and they are limited by time and spatial scale of statistics. For these reasons, we built a landscape pattern security index (LSPS) based on the traditional LSES model to evaluate the disturbance of nature or human on landscape pattern and the vulnerability of landscape types. Ecological quality index (EQ) was introduced as a supplement to evaluate the effects of the disturbance on the health and service function of ecosystem. With this method, the LSES change of modern agricultural region during last 30 years was analyzed by a case study on the state-owned Youyi farm in the Sanjiang plain, and the four phases of Landsat TM/OLI images in the year of 1984, 1995, 2004 and 2014 were the main data sources. The major land use/cover types of study area were reclassified into seven classes including construction land, dry land and paddy field (arable land), grass land, water area, natural wetland and forest. Results showed that during the last 30 years, the intense arable land exploitation had resulted in an obvious land use and cover change, which had led to a series of positive or negative ecological consequences. The proportion of arable land area had increased from 54.61% to 76.58%, and natural wetland had declined from 22.24% to 1.60%. By an analysis on land use change matrix, the major type of land use/cover change during the whole period was a conversion from the natural wetland to the dry land, and finally to the paddy field. The time variation trend of LSES in the study area was obviously regular, and the value of LSES in the year of 1984, 1995, 2004 and 2014 were 0.65, 0.57, 0.55 and 0.60 respectively. From 1984 to 1995, the regional LSES showed a decline trend. Because of the implementation of land consolidation, which had basically restored the regional landscape fragmentation, the descent rate of LSES from 1995 to 2004 had slowed down. However, natural wetland loss caused by massive cultivated land expansion still led to a decline of LSES. From 2004 to 2014, more than half of dry land had converted into paddy field during the implementation of land consolidation project. Therefore, the increasing coverage of artificial wetland had, to some extent, restored the loss of ecosystem service value caused by the diminishing natural wetland. During the whole study period, the spatial autocorrelations of LSES were significantly (P<0.05) clustered. The value of Moran's I increased from 0.5548 of 1984 to 0.5851 of 1995, and declined to 0.2564 of 2014. The descent trend of Moran's I during the lasts 20 years might be caused by the continuous implementation of land consolidation which had changed the original structure of landscape ecosystem, and the unstable of newly formed pattern of LSES. The result of local autocorrelation of LSES showed that the area percentage of H-H and L-L kept declining, and the area percentage of no significance kept increasing during the last 30 years. This might attribute to the land use/cover change caused by modern agriculture development that had brought negative effects on the landscape ecosystem, and land consolidation that also had restored the fragmented landscape pattern and damaged ecosystem service function. Thus, in order to realize the sustainable development of modern agriculture, the future land consolidation should reinforce the multiple objectives of improving the quality of arable land as well as ensuring the regional ecological security. Verified by the empirical study, the method we proposed can be used to accurately analyze the succession trends of landscape ecosystem caused by natural or human disturbance at both overall and local levels, and the method has a broad applicability on landscape ecological security evaluation in other regions. © 2016, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved. Source

Zhao X.,China Agricultural University | Zhao X.,Key Laboratory of Agricultural Land Quality | Zhang F.,China Agricultural University | Zhang F.,Key Laboratory of Agricultural Land Quality | And 2 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering

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. © 2016, Chinese Society of Agricultural Engineering. All right reserved. Source

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