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    15 April 2014, Volume 16 Issue 2
    A Review on Effect of Climate Change on Grassland Ecosystem in China
    LIANG Yan1, Ganjurjav1, ZHANG Wei\|na1, GAO Qing\|zhu1*, DANJIU Luo\|bu2, XIRAO
    2014, 16(2):  1-8.  DOI: 10.13304/j.nykjdb.2014.130
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    This paper analyzed the characteristics of climate changes in major grassland areas of China during recent 50 years. It also elaborated the research findings about the effect of temperature and precipitation changes on main grassland ecological system in China. The paper summarized the effect of climate changes on the vegetation spatial and temporal pattern of major grassland areas in china. In the past 50 years, the temperature of grassland areas in China was generally rising, while the changes of precipitation had larger time and space differences. The majority research results indicated that the effect of temperature rise on plant phenology had a great uncertainty, and its effect on the net primary productivity (NPP) of grassland vegetation had regional differences. Temperature rise would accelerate the decomposition of carbon in soil, and reduce the plant species diversity. Meanwhile, precipitation increase would make the plant phenology period in advance, prolong its growing season, raise grassland NPP, and improve species richness. But the vegetation growth had a certain hysteresis to the variation of precipitation. Different combination of temperature and precipitation had different influences on the vegetation growth. Temperature rise and precipitation increase could increase grassland vegetation coverage. Generally speaking, climate change could promote the growth of vegetation in glassland areas in China. But in certain region, it might suppress vegetation growth. The paper suggested under future climate change condition to combine the macro and micro aspects, to systematically analyze the sensitivity and vulnerability of grassland ecosystem in China, and to strengthen the comprehensive study on grassland ecosystem, so as to reduce the uncertainty of research results.

    Accelerating the Development of Circulatory Agriculture and Improving Control of Agricultural Non\|point Source Pollution
    GENG Bing, LIU Xue, YE Jing, LI Hong\|na, ZHU Chang\|xiong*
    2014, 16(2):  9-13.  DOI: 10.13304/j.nykjdb.2014.160
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    With the rapid development of economic in China, non\|point source pollution has become a major contributor of environment pollution, especially the water environments. The prevention and control of agricultural non\|point source pollution have gained more and more attention from the government and scientists in China. This paper reviewed the current state of agricultural non\|point source pollution in China and the connotation of circulatory agriculture. It also summarized researches on technologies of circulatory agriculture construction, including pollution control technology for poultry and livestock farming industry, farmland and domestic waste water. Further more, the idea of construction circulatory agriculture with enterprise management mode was discussed too. Corresponding measures such as strengthen government guidance, construction of scientific and technological innovation system and agriculture circulation industrial clusters for promoting development of circulatory agriculture for the control of agricultural non\|point source pollution was put forward.

    Analysis of Soil Environmental Quality Status of Arable Land in China
    CHEN Yin\|jun, YANG Jun\|yan, FANG Lin\|na
    2014, 16(2):  14-18.  DOI: 10.13304/j.nykjdb.2014.075
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    The soil environmental quality of arable land in China tends to deteriorate, especially the soil pollution is increasingly prominent. The area of polluted soil is  obviously expanding. The soil pollution mainly comes from sewage irrigation, sedimentation of atmospheric pollutant, disorderly stacking of solid waste, household garbage, and improper agricultural production process. The soil pollution of arable land possess the characteristics of concealment, hysteresis, accumulation, governance hardship, and trend to polyphyly and complexity. This paper reviewed the soil pollution status quo of arable land in China and the main  sources of pollution. The paper also analyzed the main characteristics of soil pollusion of arable land. Before ending, the paper put forward several issues should be paid more   attention during developing and implimenting policy measures for controlling soil pollution of arable land so as    to provide references for the improvement of soil environment of arable land in China.

    Pollution of Chemical Pesticides on Environment and Suggestion for Prevention and Control Countermeasures
    BU Yuan\|qing1, KONG Yuan2, ZHI Yong1,3, WANG Jin\|yan1,4, SHAN Zheng\|jun1
    2014, 16(2):  19-25.  DOI: 10.13304/j.nykjdb.2014.129
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    China takes the first place in the world in using chemical pesticides, which have played an important role in ensuring food production. However, the use of chemical pesticides have brought environment pollution and ecological damage. This paper summarized the pollution characteristics in different environment medium (e.g. atmosphere, soil and water) and in crops and non\|target living creatures brought by pesticides usage, and analyzed the major factors of pesticide usage causing environmental pollution. Finally, this paper put forward some suggestions for environment pollution prevention measure of pesticides usage from different aspects, including definiting management responsibility, completing management system, upgrading monitoring ability, extending technology and researching remediation technology, so as to provide references for environment safety management of pesticides in China.

    Pollution and Control Measures of Aquaculture Environment
    WU Wei1,2, FAN Li\|min1,2
    2014, 16(2):  26-34.  DOI: 10.13304/j.nykjdb.2014.076
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    The current status of aquaculture environment pollution in China was analysed. The pollution sources and their impact on aquaculture and the surrounding aquatic environment were stated. Aquaculture environmental pollution can be caused by exogenous contamination and self\|pollution of the culture. The industrial pollution, the agricultural pollution and the domestic pollution were main sources of the extrogenous contaminations, while the sources of self\|pollution involved all the inputs and byproducts in the whole breeding process, including the fertilizers, the feeds, the fish medicines, the excrement of the culture species and the sediment. The paper introduced the in\|situ remediation and ex\|situ remediation technology which were commonly used in aquaculture environmental pollution control. On the basis of the analysis above, the control measures on aquaculture environment pollution was proposed in line with the China’s national conditions, to provide ideas for improving the aquatic products quality and for promoting the sustainable development of aquaculture.

    Advances of the Abiotic Stress\|related Genes in Cotton Stress Tolerance
    LEI Zhi, ZHOU Mei\|liang, WU Yan\|min*
    2014, 16(2):  35-43.  DOI: 10.13304/j.nykjdb.2013.418
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    Abiotic stresses are important factors that affect the growth and development of plant and crop yield. In order to alleviate their negative effects, the study tries to elucidate the material basis for cotton stress resistance and its physiological functions at the molecular level, and at the same time through genetic engineering to conduct stress related gene recombination, which has become a hot spot in cotton stress resistance study. This paper reviewed the mechanism of cotton resistance to abiotic stresses, and recent research progress in the osmoregulation related genes, functional protein genes and transcriptional factor related genes. The paper also outlined the gene resources exploited though genetic engineering, aiming at providing some thoughts and references for future studies on cotton stress resistance.

    Viral Elements and Host Factors Involved in Symptom
    Development of Plant Virus
    ZHANG Chao, GONG Qian-yuan, ZHANG Yong-qiang, LI Wei-min*
    2014, 16(2):  44-49.  DOI: 10.13304/j.nykjdb.2013.429
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    Plants usually display symptom such as mosaic, deformation, chlorosis or necrosis after virus infection. These symptoms will directly cause substantial losses in crop yield, and reduce crop quality in agriculture production. Therefore, the mechanism of plant virus disease symptom development has long been a concern by the people. This paper summarized the latest advances made in home and abroad during the recent years from virus and host  fields, respectively and particularly the identified virus components and the host factors involved in symptom development. On this basis, the paper also analyzed and discussed the molecular mechanisms of virus symptom development.

    Pathogenicity Division of Plasmopara viticola in Three Provinces
    BI Qiu\|yan, MA Zhi\|qiang*, ZHANG Xiao\|feng, WANG Wen\|qiao, HAN Xiu\|ying
    2014, 16(2):  50-58.  DOI: 10.13304/j.nykjdb.2013.322
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    11 strains of Plasmopara viticola were isolated from materials collected from Hebei, Henan and Shanxi Provinces. Their pathogenicity was investigated by inoculating on 8 selected grape cultivars. Comparing the leaf disc floating method with defoliation method, the latter one was more suitable for determining the pathogenicity of P. viticola. The pathogenicities of the tested strains were divided into 2 categories. The paper had provided a basis for pathogenicity division of P. viticola for other regions. At the same time, it provided a theoretical foundation for scientific control and reasonable layout of grape varieties.

    Functional Analysis of the Two\|component System dtrAB Genes in Response to High Temperature in Deinococcus radiodurans
    WANG Wen\|tao, HAO YAN\|hua, CHEN Ming, ZHANG Wei*
    2014, 16(2):  59-66.  DOI: 10.13304/j.nykjdb.2013.640
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    A putative two component system DtrA and DtrB encoded by DR_A0009 and DR_A0010 was found in D.radiodurans. DtrA contains the histidine kinase, HisKA_3 domain and HATPase_c domain, containing four transmembrane regions; DtrB relates to LuxR\|family, and contains response regulator domain and HTH domain. The two genes were organized into an operon. Construction of D. radiodurans R1 mutants deleted dtrAB gene(ΔdtrA and ΔdtrB)by means of Kan cassette insertion. We found that the phenotype and growth curves of the two mutants were more sensitive than the wild\|type R1 under high temperature(42℃), while there are no difference between the two mutants and the wild\|type R1 under optimal temperature(30℃). Using QRT\|PCR to analysis the relative expression of heat shock genes, the results showed that heat shock genes were down\|regulated in the two mutants. That indicated two system component system DtrA and DtrB plays an important role in heat resistance.

    Function and Action Mechanisms of Each Component in Inhibition and Regulation System in Pseudomonas
    GONG Pai, SHANG Li\|guo, ZHAN Yu\|hua, YAN Yong\|liang*, LIN Min
    2014, 16(2):  67-73.  DOI: 10.13304/j.nykjdb.2013.678
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    In the complex environment, microorganism select to use the perferred carbon source by carbon catabolite repression(CCR) and at the same time inhibit the non\|perferred carbon sources, so as to achieve the best growth and metabolism procedure. This phenomenon is widespread in bacteria, but there exist differences among different species. In Escherichia coli, CRP protein plays the core role, while in Pseudomonas, the CbrAB\|CrcZ\|Crc system is critical. Crc protein is a global regulator. CrcZ is a newly identified non\|coding regulatory RNA, whose expression is regulated by 2 component system CbrAB. The whole regulatory process is under complex and efficient control. Combining the related international recent progresses and our laboratory work, this paper introduced in detail the regulation mechanism of CCR by CbrAB\|CrcZ\|Crc regulation system in Pseudomonas, expected to improve our awareness about the regulatory mechanism of carbon metabolism and microorganisms adaptability to environment.

    Functional Studies of β-glucosidase Genes in
    Trichoderma reesei
    ZHOU Qing-xin1,2, DAI Bing-ye3, CHEN Lei-lei1, LIU Xiao-yong1, QIU Ji-ying1
    2014, 16(2):  74-78.  DOI: 10.13304/j.nykjdb.2013.423
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    Trichoderma reesei represents a model system to study the fungal cellulose degradation and produces profuse quantities of cellulase. The precise nature of true “inducer” and the regulation of cellulase formation by T. reesei is still insufficiently understood. The results of preliminary studies have shown the important role of β-glucosidase in the rapid induction of cellulase complex. The measurement results of Trichoderma reesei genome sequence indicates that 7 extracellular and intracellular β\|glucosidases exist. This paper reviews and analyzes the classification, structure characteristic, transcription discrepancy of β-glucosidase and its function in rapid induction of cellulase genes.

    Research Progress on Asparagus Planting and Harvesting Mechanization in the World
    XUE Zhong1,2, SONG De\|qing1*, LIU En\|ping3, GUO Xiang\|ming1, HUANG Zheng\|min
    2014, 16(2):  79-84.  DOI: 10.13304/j.nykjdb.2013.374
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    This paper introduced the research progress made in foreign countries on selective and non\|selective asparagus harvesting, planting, and ridging machines; and asparagus target recognition research, combined with the actual situations and asparagus planting situation of our country. The paper also put forward some suggestions. According to different regions situation in China, to research and develop small size green asparagus harvesting machine; introduce and develop middle size, non\|selective white asparagus harvesting machine can not only reduce the labor intensity of bamboo farmers, but also improve operation efficiency, and increase the local farmers’ income. This paper aimed at providing references for developing the mechanization of asparagus industry in China.

    Research and Prospect of Arsenic Source and its Regulation in Arable Land Soil
    ZENG Xi\|bai, SU Shi\|ming, WU Cui\|xia, WANG Ya\|nan
    2014, 16(2):  85-91.  DOI: 10.13304/j.nykjdb.2014.077
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    Arsenic hazard is severe serious to environment and human health. In recent years, arsenic is paid high concern as a toxic metallic element. This paper summarized the latest research results at home and abroad, deemed that there existed an obvious tendency of arsenic accumulation in arable land in China. The paper also analyzed the natural and anthropogenic sources of arsenic. Meanwhile, this paper systemetically introduced the related control measures adopted at present including the physics, chemistry, biology, and agronomy methods, from the angle of removing arsenic from arable land and reducing its effectiveness. Furthermore, this paper prospected the future research direction and hotspots.

    Progress on Copper Chemical Behavior in Rhizosphere and Non\|Rhizosphere Soil
    HUANG Guo\|yong, HU Hong\|qing*, LIU Yong\|hong, HUANG Qiao\|yun
    2014, 16(2):  92-99.  DOI: 10.13304/j.nykjdb.2013.438
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    Copper is an essential trace mineral for plants and animals, but excessive copper will seriously affect the growth of plants and animals. Recently, with the development of industry and agriculture, copper pollution in soil has become one of the important soil and environment problems. Studies on copper pollution have expanded to rhizosphere domains. Rhizosphere is a soil micro region where is significantly affected by plant root system and plant growth activities. Rhizosphere has great impact on the porphologic change and migration of heavy metal owing to its special physical, chemical and biological properties. Therefore, this paper summarized the research progress made on rhizosphere chemical behavior under the influence of rhizosphere pH and Eh, the root exudates, rhizosphere organic matter and microbial changes. And then, the future study should be further deepened either on single or multiple rhizosphere environment factors (pH, Eh, root exudates, rhizosphere organic matters, etc.) about its/their influence on the morphological changes of copper. This study provided guidance for assessing the risk of copper release in soil, and expounding the mechanism of copper contaminated soil chemistry and biological repairing mechanism as well.

    Difference Analysis of Neutral Aroma Component Contents in Flue\|cured Tobacco Groups with Different Taste Characteristic
    NIU Li\|li1, ZHANG Bao\|quan2, XU Zi\|cheng1*, GENG Zong\|ze3, HUANG Guang\|hua2
    2014, 16(2):  100-108.  DOI: 10.13304/j.nykjdb.2013.360
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    118 flue\|cured tobacco leaves were collected as samples from the main tobacco\|growing areas of China. The differences of neutral aroma component contents among different taste characteristic groups were studied by using variance analysis method and factor analysis method. The results indicated that ① the taste characteristic scores of flue\|cured tobacco leaves in China ranged from 8.50 to 13.60, with the mean of 11.09, and significant differences existed among different positions and flavor types; ② the contents of 13 neutral aroma components and 4 kinds of neutral aroma component classified by the sources of aroma matter showed significant or highly significant differences among different groups; ③ among the 3 groups, comprehensive factor scores ranked in order of high taste group>medium taste group >low taste group. In the high and medium taste groups, most of the samples had higher comprehensive factor scores, while it was opposite in the low taste group. The content of neutral aroma components could be used to provide a reference for evaluating the taste characteristic to a certain extent.

    Correlation Analysis Between Climatic Factor and Chemical Components of Flue\|cured Tobacco Leaves in Baoshan Yunnan Province
    WANG Yu\|jun1,2, ZHOU Ji\|heng1,2*, ZHANG Yi\|yang2, LI Qiang2, HU Zhi\|ming3, S
    2014, 16(2):  109-115.  DOI: 10.13304/j.nykjdb.2013.383
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    Taking the descriptive statistics, simple correlation and canonical correlation analysis as methods, this paper studied the relationship between major climatic factors and chemical compositions of flue\|cured tobacco in Baoshan. The result indicated that ① climate in Baoshan was suitable for planting high\|quality flue\|cured tobacco. ② the influences of climatic factors on tobacco leaf chemical composition were  in the following order: temperature>precipitation>sunshine; protein contents, ratio of potassium to chlorine, reducing sugar and total N were obviously affected by meteorological parameter, and the weather in July had the greatest impact on chemical compositions. ③ tobacco leaf protein contents showed a significant negative correlation with sunshine hours in September, mean precipitation in July and August, and mean temperature in May, June and July; Reducing sugar was significantly negative correlated with mean precipitation in May, mean monthly temperature, while significant positive correlation with mean precipitation in July. The total N showed a significant negative relationship with mean temperature in May, sunshine hours in September and mean precipitation in July and August. The correlation of potassium ratio to chlorine was significantly positive with mean temperature in August and September, and significantly negative with sunshine hours in July. The influences of temperature and precipitation on tobacco leaf chemical compositions were: reducing sugar > total N > protein, and total N >reducing sugar >protein, respectively.

    Current Status and Prospect of Evaluation on Clinical Effectiveness of Veterinary Herbal Medicine
    CUI Dong\|an, WANG Lei, WANG Xu\|rong, WANG Xiao\|wu, LI Jian\|xi*, YANG Zhi\|qi
    2014, 16(2):  116-116.  DOI: 10.13304/j.nykjdb.2013.579
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    The clinical therapeutic effect is the basis for the development of traditional Chinese veterinary medicine. However, it has not yet established an internationally recognized and formal system for effects evaluating. This paper evaluated the current status of the clinical effectiveness evaluation of veterinary herbal medicines, and analyzed the feasibility of  group differentiation under large scale farming conditions. According to the characteristics of clinical study on traditional Chinese veterinary medicine and research findings made in clinical epidemiology and evidence\|based medicine, this paper suggested a clinical effect evaluation model, which combinined the clinical practice of differential treatment with clinical randomized trial study based on group level, so as to form periodic chain of evidence for traditional Chinese veterinary medicine, and to effectively evaluate the clinical effects of traditional Chinese veterinary medicine, thus to provide technological support to facilitate the rapid development of Chinese veterinarian medicine.

    Effect of Different Comb and Feeding Selection on the Application of Honeybee Mini\|mating Hive
    LV Li\|ping1, LIU Zhi\|guang1*, GUO Hai\|kun1, DING Gui\|ling1, SHI Wei1,2*
    2014, 16(2):  122-126.  DOI: 10.13304/j.nykjdb.2013.424
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    Honeybee mini\|mating hive  could effectively reduce the quantity of mating bees, improve the queen mating success rate, save apiary space for mating, and increase queen bee breeding population. At present, the mini\|mating hive usage rate is low in our country, and there are some adaptation problems existing in application process. The comb frame type and feedstuff type are key issues in applying honeybee mini\|mating hive. Vacant comb frame is obviously superior than other types in the swarm swarming sex and during queen bee breeding time. During honey flow season, the colony development and queen bee breeding is obviously superior than other types. Therefore, the best use of mini\|mating hive is using the vacant comb frame during large honey flow season. Syrup and a small amount of pollen were fed during no\|honey flow season. This way would encourage the mating queen to lay eggs and the larvae to hatch. After fully understanding the application method of honeybee mini\|mating hive, the popularization and application of honeybee mini\|mating hive could be speeded up.

    Full\|length cDNA Cloning and Expression Analysis of catalase Gene from Sea Cucumber (Apostichopus japonicus)
    GAO Shan, ZHOU Zun\|chun*, DONG Ying, YANG Ai\|fu, CHEN Zhong, WANG Bai, GUAN Xi
    2014, 16(2):  127-134.  DOI: 10.13304/j.nykjdb.2013.442
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    Studying the function and mechanism of immune\|related genes can provide scientific reference for preventing and controlling diseases in sea cucumber (A. japonicus) culture. In this study, the full\|length cDNA of catalase gene from A. japonicus was cloned and characterized for the first time,which was 1 885 bp including a 76 bp 5′\|untranslated region (UTR), 1 503 bp ORF encoding 500 amino acids,and a 306 bp 3′\|UTR; and the predicted molecular weight was 56.56 kDa. The result of amino acid sequence alignment showed that 75% amino acid sequence identity to the Catalase of Hyriopsis cumingii and Strongylocentrotus purpuratus. The peroxisomal targeting signal PTS2, NADPH binding residues, and heme\|ligand binding signal sequences “RLFSYPDTH” were identified in the deduced amino acid sequence of Catalase from A. japonicus. Phylogenetic analysis suggested that the Catalase of A. japonicus was close to that of S. purpuratus in invertebrate cluster. Quantitative real\|time PCR analysis showed that catalase gene was expressed in all the tested tissues including body wall, feet, coelomocyte, respiratory tree, muscle, intestine, and the highest expression level was found in intestine. The expression of catalase mRNA was up\|regulated significantly in the coelomocytes at 4 h after LPS challenge. Those indicated that catalase gene was involved in the immune response to the bacteria challenge in A. japonicus.

    A Strain of Lignin\|degrading Bacterias Screening and Optimization of Enzyme\|producing Condition
    ZHANG Qing\|fang, YU Zong\|lian
    2014, 16(2):  143-148.  DOI: 10.13304/j.nykjdb.2013.444
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    Lignin is a common refractory material in the nature, which was abundant and complex, and concealed in crop straw and municipal solid waste. Some bacterial has the function of degrading lignin. This paper took deadwood and dead leaves as the sample, screened C\|9 strain by aniline blue plate method, which can degrade lignin and has a higher ability to produce enzymes, so as to attain the high efficient bacteria of lignin\|degrading, and provide reference for the study on lignin\|degrading by bacterial. It was identified as Arthrobacter sp. through microbial morphology and 16SrDNA. The optimization of enzyme\|producing condition for C\|9 strain was confirmed by the optimization of enzyme\|producing conditions: temperature 30~35℃, rotate speed 150 r/min, culture basis of pH 7~8, the optimal carbon source was starch, the optimal nitrogen source was peptone, and the amount of MnSO4 inducer was 0.8 mmol/L. Under the optimal condition, the lignin peroxidase yield of C\|9 strain was 74.62 U/mL, the manganese peroxidase yield of C\|9 strain was 58.61 U/mL, and the laccase activity was 68.92 U/mL.

    A Method to Generate Single\|stranded DNA Through SELEX Technology
    LIU Zhong\|cheng1, XIE Yao1, ZHANG Yan\|fen2, ZHAO Li\|jian1, LIU Li\|peng1, XIA
    2014, 16(2):  149-154.  DOI: 10.13304/j.nykjdb.2014.012
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    In order to establish a simple and effective method for preparing single\|stranded DNA in SELEX screening process, this study optimized the experimental conditions for preparing the streptavidin\|conjugated magnetic nanoparticles, decided the best time and saturation of symmetric PCR product binding with streptavidin\|conjugated magnetic nanoparticles, verified the influence of different NaOH concentration on desmolysis effect, and established the ssDNA preparation system applied to SELEX technology. The purity and recovery efficiency of ssDNA obtained by established method in this experiment and traditional asymmetric PCR method was compared using fluorescence and polyacrylamide gel electrophoresis. The result showed that under optimal experimental condition the method established in this experiment was significantly better than asymmetric PCR method.

    Studies on Low-Carbon Eco-agricultural Development
    Model in Yellow River Delta
    LI Ying,WANG Bao-hai*
    2014, 16(2):  155-159.  DOI: 10.13304/j.nykjdb.2013.377
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    Since entering into the 21st century, greenhouse gas emissions have led to the continued global warming. Low\|carbon environment protection has been raised on the agenda. The development of low\|carbon eco\|agriculture has become an effective way to solve China's agricultural resources exhaustion, to curb environment deterioration, and to achieve the sustainable development of China's agriculture. In 2009, the Yellow River Delta Efficient Ecological Economic Zone rose to the national strategy. Low-carbon agriculture has become the theme for the development of modern agriculture in the Yellow River Delta. This paper analyzed the necessity for the Yellow River Delta to develop Low-Carbon Eco-agriculture. Combining with the status quo of natural resources and environment in this area, and the requirement for developing Low\|Carbon agriculture, the paper put up 5 models suitable for the Yellow River Delta to develop Low-Carbon Eco-agriculture. At the same time, a series of suggestions were put forward based on these models.

    Measurement and Analysis on Contribution Rate of |Input Factors in Chinas Cotton Yield Increase
    QIAN Jing\|fei, LI Ning\|hui, GUO Jing\|li*
    2014, 16(2):  160-165.  DOI: 10.13304/j.nykjdb.2013.650
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    Cotton is an important strategic material related to national interest and peoples livelihood. Cotton yield is affected by many factors. Through analyzing various production factors contribution to cotton yield increase, the basic factors promoting cotton output growth were found out to provide theoretical reliance and policy support for ensuring the supply of cotton market. Based on 4 major factors affecting the cotton yield increase, i.e. land investment, material and capital investment, labor input, disaster. Using production function, this paper calculated the various factors production elasticity and rate of contribution on cotton yield increase. The results showed that technology advance played a vital role in cotton production, land investment was the first restriction factor affecting cotton yiel increase, labor force and dizaster were the negative factors for cotton output. Before ending, the paper puts forward some corresponding policy suggestions.

    Farmers Perception and Problems of Conservation Tillage Extension
    ZHANG Er\|peng| ZHAO Xin| WEI Yan\|hua| CHEN Fu| ZHANG Hai\|lin*
    2014, 16(2):  166-173.  DOI: 10.13304/j.nykjdb.2013.244
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    With the benefits of conserving water and soil,conservation tillage has become an important technology for sustainable agriculture. In order to understand farmers perception for conservation tillage during its adoption and extension process in North China Plain, and provide guidance for optimizing this technology, a face\|to\|face questionnaire survey in conservation tillage demonstration area of Henan province was conducted. The results indicated that the majority of farmers had accepted conservation tillage. No\|till with residue retention for maize has been widely adopted in this region. Due to its benefits in saving water and conserving soil, 83% of the farmers had positive attitude towards conservation tillage, while 74% of the total farmers received the technical guidance from the extension department and hoped to have some guidance for conservation tillage from relevant department. The majority of farmers considered the principal limiting factors for adoption of conservation tillage were high amounts of residues, increasing crop diseases and insect pests, and unstable crop yield. Combining farm machinery with agronomic techniques, strengthening government support, selecting superior cultivars, and improving matching technologies, etc. can surely promote the development and extension of conservation tillage.

    Analysis of Knowledge Evolution in Biological Breeding Field From 1995 to 2012
    HAO Xin\|ning, SUN Wei, ZHANG Xue\|fu*
    2014, 16(2):  174-181.  DOI: 10.13304/j.nykjdb.2013.281
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    Biological breeding science has experienced full speed development for over half a century, and the number of scientific and technical literature has increased rapidly. Through analyzing the knowledge development in subject areas, this paper provided the most up\|to\|date progress of varied discipines, detected research hot spots, and discovered the internal connection between knowledge and their integration, so as to forecast the tendency for future development of various disciplines. A knowledge evolution model was constructed based on various phenomena in knowledge evolution process. This model can automatically analyze the relationships, properties, change degree and changing trends between different time windows. Biological breeding documents published between 1995-2012 were selected, combined with co\|author in the network and country cooperation networks to analyze the knowledge evolution phenomena, displayed all results under different time windows, and preliminary confirmed the feasibility of time slice strategy on seeking knowledge evolution phenomenon.