中国生态农业学报(中英文)

Scientific contributions and achievements of Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences over the last 40 years

HU Chunsheng

2018, 26(10): 1423-1428. doi: 10.13930/j.cnki.cjea.180797

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This paper summarized the scientific contributions and achievements, social impacts of Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences. For the last 40 years, the center has been seeking the way for agricultural modernization in China. The ecological agriculture model was developed and demonstrated in the 1980s. The resource-saving agriculture model focused on water saving was developed and disseminated in the 1990s. The intelligent agriculture and green agriculture model was developed and demonstrated in the early 2000s. Overall, the theories of agro-ecosystem managements for water-saving irrigation, nitrogen cycling, mitigation of non-point sources pollution, forest ecological engineer, saline soil reclamation, nutrients flow of food chain and molecular breeding have been developed during the last 40 years. Several large-scale agricultural demonstration projects, as "Bohai Granary" building project, by combination of government, farmers, extension technicians and researchers were organized and conducted, which greatly promoted the regional agricultural development.

Changes of research hotspots and trend of Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences based on bibliometric analysis

LI Rong'e, FENG Xuezan, XIE Zhixia, MA Baozhen

2018, 26(10): 1429-1442. doi: 10.13930/j.cnki.cjea.180736

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Published scientific papers included in China National Knowledge Infrastructure (CNKI) and the core collection of Web of Science (WoS) of Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese academy of Sciences (CARR) since 1978, when CARR was launched, were bibliometrically analyzed to reveal the changes in research hotspots and trends of CARR since its' establishment. The CNKI and WoS searching results showed 2 052 papers of researches conducted by CARR since 1978, of which 1 467 papers were in Chinese and included in CNKI, and 585 papers were in English and included in WoS. Annual published Chinese papers number increased and peaked in 2005, and then kept at around 50 though slightly decreased. Papers in English were mainly published after 2002 and increased quickly with annual increase rate of 26.85% from 2003 to 2017. There were 118 papers in Chinese and 44 papers in English cited more than 50 in CNKI and WoS, respectively. And Chinese papers were published in 235 journals, and English papers in 237 journals. The average impact factors of the Chinese journals and English journals publishing top 10 papers were 1.022 and 3.411, respectively. The papers were mainly supported by the Program of Knowledge Innovation of Chinese Academy of Sciences, National Natural Science Foundation of China, National Basic Research Program of China (973 Program), National High-tech R&D Program of China (863 Program) and National Key Technologies R&D Program of China. The international cooperation of CARR increased yearly, and there were 73 international cooperation funds supporting the researches of CARR, such as International Cooperation Project of Chinese Academy of Sciences, Fund of Australia International Agricultural Research Center, National Study Abroad Fund of China, European Community Fund. The institutions collaborating with CARR to publish scientific papers were mainly from Hebei Province, Beijing City, Shandong Province and Shanxi Province, while the international institutions were mainly from USA, Japan, Netherland, Australia, Denmark, Pakistan. Co-occurrence analysis of keywords of published papers based on CiteSpace showed that the keywords in the first ten years since CARR establishment were less with weak interconnection. After that, the research keywords increased and peaked around 2000. The interconnections among keywords were increasingly close. The studied crops were wheat and maize, the areas concentrated in the North China Plain. Under the climate change background, the research works of CARR now are mainly focusing on crop cultivation, breeding and molecular biology; water resources and water-saving agriculture; carbon and nitrogen recycle of agroecosystem; reclamation of salt soil land, and utilization of halophyte and salt water resources. In summary, CARR have formed its' special research area and made remarkable research achievements.

Advances in clarification of the driving forces of water shortage in Haihe River Catchment

YANG Yonghui, REN Dandan, YANG Yanmin, TIAN Fei, HU Yukun, HAN Shumin

2018, 26(10): 1443-1453. doi: 10.13930/j.cnki.cjea.180658

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Including Beijing, Tianjin, Hebei and three surrounding provinces, Haihe River Catchment is facing an increasing shortage of water resources. This paper summarized our research progress on the driving mechanisms of water resources change including reasons for runoff changes, spatial variations and temporal changes of agricultural water use, and outflow of virtual water through external food supply. Firstly, by using the sequential Mann-Kendall to determine the abrupt changes in eight sub-catchments of Haihe River Catchment and traditional Mann-Kendall test for the period 1960-1999 to identify the basic trend of precipitation and runoff, it was confirmed that runoff reduction started since 1970s, and generally became statistically significant from 1978 to 1985. Through correlation comparisons for precipitation and runoff for the periods prior to and after abrupt runoff changes, human activity, rather than climatic change, was identified as the main driving factor of runoff changes. By using SWAT model, it was concluded that human influence on agricultural water demand contributed to 76% of runoff decline at the beginning of the China's rural reform. Secondly, through crop modeling, crop water demand calculation by crop coefficient and ET, and remote sensing methods, spatial and temporal distribution of agricultural water demand in the Haihe Plain were quantified. Changes of agricultural water demand were evaluated. This in turn laid the basis for surface water reallocation following the completion of the South-to-North Water Transfer (SNWT) project. By comparing agricultural water consumption, groundwater level change, and water supply from the SNWT canal, it was estimated that there could be a relative balance of water demand and supply in the piedmont plain with the designed water supply from SNWT upon strong limitation on further water-consumption increase especially for newly developed landscapes such as lakes, rivers, wetland, water consuming woodland, and etc. In the coast plain, water shortage would remain for the long-term, meanwhile more water supply together with brackish water use was to be developed. While agriculture placed the greatest demand on water resources, reducing the cultivation of water-consuming crops might be the most effective way to reduce agricultural water use. However, taking food demand into consideration, sustaining the balance between regional water and food security was a growing challenge. To solve such problem, we studied NEXUS or interlinkage among land use, water consumption, food production (Land-Water-Food NEXUS) in Beijing-Tianjin-Hebei Region. Virtual water flow embedded in food transfer was evaluated. According to our estimation, nearly 9×10⁹ m³ virtual water and 2×10⁶ hectares cropland were currently used for producing 1.2×10⁷ tons maize for external food supply, which highly resulted in the locally developing water shortage. Controlling food production and virtual water outflow shall be a suitable and very necessary way to alleviate the pressure of water shortage facing the quick developing strategies of Beijing-Tianjin-Hebei Region and the newly lunched Xiong'an New District.

Water use and water-saving irrigation in typical farmlands in the North China Plain

ZHANG Xiying

2018, 26(10): 1454-1464. doi: 10.13930/j.cnki.cjea.180636

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This paper summarized the researches of Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences on water-saving irrigation for winter wheat and summer maize at the Luancheng Agro-Ecosystem Experimental Station, Chinese Academy of Sciences, a typical farming area in the North China Plain (NCP). The results from long-term field studies showed that for the period from 1980 to 2017, yield of winter wheat was increased by 55.7% and that of summer maize by 59.7% under fully irrigated conditions. Water consumption (ET) of winter wheat was increased from 400 mm to 465 mm, ET of summer maize was relative stable at about 375 mm. Annual ET was increased from 777.0 mm in the 1980s to 834.4 mm in the 2010s. The annual irrigation water demand was averagely around 300 mm. Therefore, it was necessary to reduce irrigation water use to conserve local groundwater resources. Under limited irrigation, one irrigation of winter wheat at jointing stage significantly increased vegetative and root growth of this crop, which was beneficial for the efficient use of soil water at later stages of crop growth. Under this critical stage irrigation schedule, annual ET was reduced by 165.2 mm, while grain production remained stable at relative higher level. Results also showed that by reducing irrigation amount per application and increasing irrigation frequency under limited irrigation, the combined effects of interaction of crop root, soil water and soil nutrient at the topsoil layer could increase water availability to the crop and thereby increase grain production and water use efficiency. A minimum irrigation (MI) schedule was developed for more serious water shortage regions, which was to maintain good soil moisture conditions at the time of sowing and no other irrigation being applied during the other growth periods. As compared with full irrigation, yield was reduced by 28%, but irrigation water use was reduced up to 69%, reduction in ET was by 43% and water use efficiency increased by 13%. Annual ET was reduced to 560 mm and annual irrigation water use was reduced to 120 mm. Significant reduction in irrigation water use was achieved as compared with the full irrigation schedule. As compared with the reduction in cropping intensity (RCI) measure (changing annual double cropping of winter wheat and summer maize to three crops every two years), MI schedule could fully use the rainfall resources and reduce soil evaporation consumption during fallow period under RCI. Yield of winter wheat and summer maize for MI under double cropping system was 5.5%-12.0% higher than that for RCI, with annual ET of 10%-13% less. Based on results from the long-term field experiment, the implementation of water-saving irrigation schedule such as MI and critical irrigation scheduling significantly reduced irrigation water use and at the same time maintained stable grain production. Therefore, water-saving irrigation schedule under double cropping of winter wheat and summer maize was recommended as one of the important measures for solving the problem in groundwater overdraft in the NCP.

Physio-ecological regulating mechanisms for highly efficient water use of crops

DONG Baodi, LIU Huiling, WANG Yakai, QIAO Yunzhou, ZHANG Mingming, YANG Hong, JIN Lele, LIU Mengyu

2018, 26(10): 1465-1475. doi: 10.13930/j.cnki.cjea.180687

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The North China Plain (NCP) is a severe water shortage region and one of the important grain crop production bases in China. With the rapid rise of China's national economy, the water shortage of agriculture production has acutely increased. To reduce the exploitation of groundwater and resolves problems in agricultural water resources, a series of water-saving measures have been proposed and developed. However, improving crop water use efficiency has been among the most basic requirements to this goal. This paper therefore reviewed four aspects of research progresses of improving crop water use efficiency. They included the varieties difference in high water use, response difference of crops at different growth stages to water, regulation of stomatal conductance on excessive transpiration of crop leaves, differences in physio-ecological strategies of different drought-resistant corps to water stress. On this base, three integrated cultivation techniques were advanced according to our research results. The first was adjustment of planting structure to improve annual water use efficiency of crops. To gain this goal, it was important to establish rational planting structures and rotation patterns based on difference in water consumption characterizes, yield and economic efficiency of crops/varieties. In the high-yield region of the piedmont of Mountain Taihang, the pattern of three-cropping in two years of winter wheat-summer millet/spring sweet potato was a planting structure with high yield-and economic-water use efficiencies. The second cultivation technique was activation and broadening of sowing date thresholds via increase seeding rate and mulching to increase rainwater use efficiency. In our research, grain yield of winter wheat was not significantly different regarding sowing date-before December or in early October under intensive seeding and soil-coated film mulching in the Bohai Lowland Plain. The third aspect was improving crop water use efficiency in rain-fed fields by coating soils with film mulch. The pattern of subsoil plastic film mulch dual used by winter wheat and summer maize significantly inhibited soil evaporation and salt accumulation, increased seed emergence rate, promoted aboveground biomass and increased grain yield and water use efficiency of two crops in dry lands. In the Bohai Lowland Plain, this cropping pattern made use of rainwater and slight saline water. Grain yield of winter wheat-summer maize was up to 15 910-16 966 kg·hm^-2, which represented an increase of 10.52%-41.44% over that under no mulching. In the future, disruptive innovations such as new quantitative standards for high crop water use efficiency and utilization of unconventional water resources can lead to significant breakthroughs in agricultural water saving.

Spatial distribution characteristics of nitrate in shallow groundwater of the agricultural area of the North China Plain

WANG Shiqin, ZHENG Wenbo, KONG Xiaole

2018, 26(10): 1476-1482. doi: 10.13930/j.cnki.cjea.180639

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Nitrate contamination of groundwater in the North China Plain had attracted much attention. However, the characteristics and degree of nitrate contamination of groundwater on large scale were not uniform due to the effect of different factors such as landscape type, land-use, soil structure, and aquifer hydrogeology. This paper comprehensively summarized some studies on the status of nitrate pollution in groundwater in the North China Plain. It also included our results on nitrate concentration in shallow groundwater in agricultural areas in the North China Plain in recent years. It was found that nitrate pollution in shallow groundwater existed in three typical landscape types, including headwater area (hilly areas of Taihang Mountain), piedmont plain and lowland plain. The headwater area had different land-use and good soil and aquifer permeability and therefore required much attention in terms of controlling nitrogen input. There was also the need for researches on how climate change affected hydrological process and nitrogen transport in the region. The piedmont plain had high agricultural production, with deep groundwater depth and thick saturated zone. Relatively high nitrate concentration in the piedmont plain was not only related to point source, wastewater leakage and wastewater irrigation, but also to over application of fertilizer in the farmland. The impact of over application of fertilizer on groundwater, the flow path and the potential threat on shallow groundwater quality were very important for future researches. The leaching rate of nitrate was lowered due to the fine sediment of soil in the lowland area. However, groundwater was at high risk of nitrate contamination because of the shallow groundwater depth. There was therefore the need for correct assessment of potential risks of nitrate pollution of groundwater based on surface water, soil and groundwater interactions.

Microcosmic and macroscopic researches on high-water use efficiency agriculture

ZHANG Zhengbin, XU Ping

2018, 26(10): 1483-1493. doi: 10.13930/j.cnki.cjea.180431

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Since 2001, we aimed at the research of water-saving agriculture and water, food and ecological security in the North China Plain. Thus we conducted high-water use efficiency agriculture through interdisciplinary micro-and macro-research. In microscopic research which was successively carried out for wheat water-saving cultivar and breeding, wheat physiological and genetic control for water use efficiency, related gene cloning and function and transgenic technology were investigated. Also marker-assisted selection breeding research, recent technologies such as molecular design breeding and gene editing for water using efficiency were also conducted. Seven wheat varieties were selected, two of which were examined at the national level. Representative works like "wheat genetics", which was the foundation for physiological genetic breeding of drought and water-saving in crops won two second prizes of the National Science and Technology Progress Award. With respect to macro research, we carried out researches on high-water efficiency agriculture in dry land, water resources and food security, wheat adaption to climate change, green agriculture to increase grain yield and efficiency. We put forward the construction of Huanghuai South Second Granary and more than thirty important consulting reports adopted by the national and local governments and leaders. The Second Granary engineering science and technology innovation became the four innovation projects of the Ministry of Science and Technology of China in 2017, and the major breakthrough project of Chinese Academy of Sciences in the 13^th Five-Year Science and Technology Plan. Representative works included research and development of high-water agriculture of dry-land in China; water resources, food security and modern agriculture development in China; crop response to climate change, efficient utilization of water resources and food security and coordinated of green agriculture development in China; development strategy and practice of the Second Granary in China. In the micro and macro aspects, our researches promoted detailed development of high-water efficient agriculture in China, and became a special subject area in Chinese Academy of Sciences for water-saving agriculture in North China.

Nutrient flow and management in the food chain in China

MA Lin, MA Wenqi, ZHANG Fusuo, BAI Zhaohai, HOU Yong

2018, 26(10): 1494-1500. doi: 10.13930/j.cnki.cjea.180668

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In order to explore food security, high resources use efficiency and environmental friendly pathway for the coordinated and green developed agriculture in the food production and food consumption system, we constructed the "soil-crop-livestock-family-environment" ("food chain system" in short) research system. Using the material flow and metabolism theories, a nutrient flow model had been developed, and was used to evaluate the nutrient flow and control mechanisms of food chain system. After more than ten years systematic studies, the research team obtained the following main results:(1) Develop the pyramid framework for nutrient flow of the food chain, and the food chain nutrient flow model. By analyzing nutrients behavior in the "Soil-Crop-Livestock-Household-Environment" system, we found that the nutrient flow from "Soil-Crop-Livestock" to "Household" sector was in the shape of pyramid. The shape of pyramid determined the productivity, nutrient efficiency and environmental effects of the food chain system. The "Household" consumption at the top of pyramid was the driving force of nutrient flow in the whole food system, meanwhile, determined the nutrient efficiency of whole system. "Soil-Crop-Livestock" was located at the bottom of pyramid, supporting the "Household" consumption sector at the top. It determined the total nutrients flux and acted as the core of nutrients management. Based on this, the NUFER (NUtrient flows in Food chains, Environment and Resources use) was developed, the parameter set was build and quantification of nitrogen (N) and phosphorus (P) flows, use efficiencies and environmental emissions at the national and regional scales had been done. (2) Spatial and temporal analysis of N and P flows, use efficiencies and environmental costs in the food chain system. We quantified the spatial and temporal characteristics of N and P flows, efficiencies and environmental emissions in crop and animal production sector, and the whole food chain in China. We identified the contribution of nutrient losses form soil-crop system, livestock and human consumption. We also developed the concept of food N (P) cost and found that the resource and environmental costs of food production and consumption in China had increased rapidly, far exceeding the developed countries. (3) Identifying the driving forces of nutrient flow in the food chain and the options to improve nutrient efficiency and reduce environmental losses. The key sector that determined nutrient efficiency had been identified. Urbanization, diet changes and development of livestock production were the main driving forces of the accelerated nutrient flow in food chain system. We also explained the effects and mechanisms of increasing imports of food and feed, optimizing dietary and improving the nutrient management in agriculture production on improving food chain systems. We also found that the coupling of crop and livestock production, improving utilization of livestock manure was the key to reducing chemical fertilizer use and environmental losses, and was also the key for achieving green development of agriculture and sustainable food systems.

Nitrogen processes and related environmental effects on agro-ecosystem in the North China Plain

HU Chunsheng, ZHANG Yuming, QIN Shuping, WANG Yuying, LI Xiaoxin, DONG Wenxu

2018, 26(10): 1501-1514. doi: 10.13930/j.cnki.cjea.180633

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The North China Plain is one of the most important bases for grain production. In the present agricultural production, farmers apply excessive fertilizer for high yield. Therefore, fertilizer use efficiency has become very low and environmental pollution as a result of it has also become more and more serious. The sustainable development of local agricultural economy and ecological environment has been greatly threatened. This paper reported our research findings on nitrogen processes in agro-ecosystems based on long-term (since 1978) fertilizer field experiment in Luancheng Agro-Ecosystem Experimental Station of Chinese Academy of Sciences. Nitrogen processes and the related environmental effects on the agro-ecosystem in the North China Plain were analyzed. This included nitrogen transformation characteristics in soil-plant systems, nitrogen fluxes and their transformation mechanisms, comprehensive nitrogen management and regulation, etc. Eight long-term field experiments related to nitrogen addition to the soil were conducted since 1978. Based on the field experiments, improvements in soil fertility, high production and high efficiency, recycled nutrient applications, agro-ecological processes and response mechanisms and feedback to climate change were studied. The research methods for nitrogen processes were fairly improved and innovated. Based on in situ observation system of soil denitrification in high nitrogen background concentrations, the mechanisms of soil denitrification in indoor incubations, total quantity of nitrogen removal in situ denitrification and production compositions were also studied and quantified. Meanwhile, system errors of denitrification rate measured by acetylene inhibition method were quantified. Furthermore, soil gas determination techniques in deep soil profile were established. Therefore, the mechanisms of N₂O production/consumption at the soil-atmosphere interface were expanded into the deep soil profile. The depth-dependent contribution of N₂O flux in the soil profile to soil surface gas exchange was quantified based on studies on N₂O production mechanisms, diffusion and reduction processes in the subsoil. The state of nitrogen balance in agro-ecosystem in the region was estimated based on studies on nitrogen conversion mechanisms, nitrogen fluxes and the related environmental effects. Different ways of nitrogen loss in agro-ecosystem were compared and the prefer approaches for controlling nitrogen loss and increasing fertilizer use efficiency put forward.

Carbon processes and environmental effects on agro-ecosystem in the North China Plain

HU Chunsheng, WANG Yuying, DONG Wenxu, ZHANG Yuming, LI Xiaoxin, CHEN Suying

2018, 26(10): 1515-1520. doi: 10.13930/j.cnki.cjea.180617

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The mechanisms of agro-carbon cycle in climate change (experimental warming) and management practices (nitrogen application, straw returning and tillage patterns, etc.) were summarized based on studies during the last 25 years in winter wheat and summer maize double cropping system in the North China Plain in this paper. Three long-term field experiments of carbon cycle were conducted since 2001, including tillage experiment, organic carbon cycle experiment and experimental warming field. Meanwhile, four methodologies for monitoring system performance of carbon processes were established, including isolation tank-alkali absorption method, static chamber-gas chromatography method, eddy covariance observation system and concentration gradient-based method. The carbon budget for input and output was quantified and carbon sequestration via nitrogen addition reassessed in winter wheat and summer maize rotation cropland in the North China Plain. The net ecosystem exchange of CO₂ was partitioned into gross primary production (GPP) and total ecosystem respiration (TER). Meanwhile, net primary productivity (NPP) and soil respiration (SR) were determined to compute autotrophic and heterotrophic respirations. The net carbon budget was calculated seasonally based on NPP and considering carbon input through crop residues and carbon output through grain harvest. We found that winter-wheat system was a carbon sink of 90 g(C)·m^-2, whereas summer maize system was a carbon source of 167 g(C)·m^-2. Thus the double cropping system behaved as a carbon source of 77 g(C)·m^-2 at annual scale, corresponding to an annual average loss rate of nearly 1% in topsoil organic carbon stock during 2003-2008. Our study provided evidence that carbon was lost in intensive wheat-maize double cropping system in the North China Plain at the rate of 77 g(C)·m^-2·a^-1, when harvest removals were considered even though crop residue carbon was input into the soil since 30 years ago. Meanwhile, we found that although nitrogen application in calcareous soil significantly increased soil organic carbon pool in the 0-100 cm, it decreased soil inorganic carbon accumulation in the 0-60 profile. The results of further studies on environmental effects of carbon showed that warming and nitrogen fertilization significantly decreased CH₄ uptake, but had no significant effect on total cumulative soil CO₂ flux. The lack of significant effects of warming on soil respiration had resulted from:1) warming-induced soil drying offsetting the effects of soil temperature increase on carbon emission; 2) adaption of soil respiration to increased temperature. In the soil profile, it was found that nitrogen application had no significant effect on production and fluxes of CH₄ and CO₂. Based on simultaneous measurements of soil surface emissions (static chamber-based method) and of subsurface flux (concentration gradient-based method), we highlighted that the topsoil (0-40 cm) played a critical role in CO₂ production and CH₄ consumption in unfertilized maize-based farmland in the North China Plain.

Reclamation and utilization of saline soils in water-scarce regions of Bohai Sea

LIU Xiaojing

2018, 26(10): 1521-1527. doi: 10.13930/j.cnki.cjea.180725

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Freshwater scarcity is one of the main constraints to the reclamation of saline soils. Research and demonstration studies on the reclamation and utilization of saline soils in water-scarce regions of Bohai Sea started since 1982 in Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences. The experiments had included regulation of shallow groundwater table via well-water irrigation and rainwater recharge, soil salt leaching via saline water irrigation, root-zone soil desalination via agronomic methods and utilization of halophytes. The major achievements were as follows:1) the regulating levels of shallow groundwater table were determined and the patterns of management by well-water irrigation and rainwater leaching to control soil salinization in lowland plains established. Through well-water irrigation, the critical level of shallow groundwater table was kept at >2-3 m during the dry season to reduce soil evaporation and control soil salinization. This was further reduced to 4-6 m before the rains to enhance rainwater recharge and in turn leaching of soil salts and dilution of saline groundwater. Next the groundwater table was kept at >0.5-1.0 m during the rains again to assure healthy crop growth. After the implementation of this method in Changzhuang Town (Nanpi County in Hebei Province) for the period 1983-1988, soil salt content decreased from 3.86 g·kg^-1 to 1.36 g·kg^-1, and the area of saline Chao soil and saline groundwater dropped by 76.2% and 42.8%, respectively. 2) The separation process of saline water and freshwater by melting saline ice and its infiltration into saline soil were revealed and the method of reclamation of coastal saline soils by freezing saline water in winter invented. Lab experiments showed that saline ice was desalinized efficiently by melting, which produced about 60% low salinity (< 4 g·L^-1) water from melting saline ice (< 15 g·L^-1). Also the infiltration of saline ice melt-water reduced surface soil salt content. Field experiments indicated that by freezing saline water (< 15 g·L^-1) irrigation in winter (< -5℃) combined with plastic film or straw mulching and rainwater leaching improved coastal saline soil. The soil salt content in 0-20 cm was less than 3.0 g·kg^-1 during the growing season under freezing saline water irrigation, while it exceeded 10 g·kg^-1 under control (no irrigation) treatment. 3) Trough coupling of the dynamics of soil salt and water, climate and plant growth, the agronomic patterns of soil salinization control in the root zone was established via ridging, mulching and straw incorporation into the deep soil layer. In monsoon climate regions, there was soil salinization in spring due to low rainfall and high evaporation, and then soil desalinized in summer due to high rainfall. Seed germination and seedling growth were the salt-sensitive stages, which usually occurred in spring. Therefore, it was important to create low salinity in the root zone for health growth of plant in spring. In order to desalinize the root zone soil, field ridging in spring and straw incorporation in autumn were studied. The results showed that field ridging, combined with plastic film and straw mulching, reduced soil salinity to 2.0 g·kg^-1 and straw incorporation into deep soil layer controlled the soil salinity in spring at < 3 g·kg^-1. 4) The adaptive mechanisms of halophytes to saline soils were explored and the pattern of efficient utilization of saline resources established. For the utilization of saline soils and saline water, salt tolerant plants and halophytes were collected and screened. The effects of salt stress, combined with those of water and nutrient application, on seed germination and plant growth were studied. The results showed that seed germination required low salinity, moderate salinity alleviated drought stress on seed germination and seedling growth, NO played a very important role in the regulation of salt tolerance of seedlings derived from dimorphic seeds of Centralasiatica atriplex, and N application increased the growth of halophytes under salt stress, etc. Based on the characteristics of salt tolerance of different plants, the method of growing plants in saline soils was established. This included land plowing, holing cultivation, fertilizer application, frozen saline water irrigation, mulching, etc. The application of the above results has supported crop production and ecological rehabilitation of saline soils in water-scarce regions of Bohai Sea.

Regulations of salt and water of saline-alkali soil: A review

SUN Hongyong, LIU Xiaojing, ZHANG Xiying

2018, 26(10): 1528-1536. doi: 10.13930/j.cnki.cjea.180607

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The safety utilization of saline water resources guarantees sustainable development of agricultural production in the Low Plain near the Bohai Sea. Focusing on water shortage and soil salinity, a series studies were conducted on reclamation of saline soils and regulation of water and salt transportation in the farmlands at Nanpi Eco-Agricultural Experimental Station of Chinese Academy of Sciences, where is a typical site of saline and water deficit regions in the North China Plain. This paper reviewed the study results of the development process for reclamation of saline soil and regulation of water and salt transfer in the farmland. Before the 1980s, most works in the region focused on reduction of flood risk through building of irrigation and drainage canals. In the 1980s, researches focused on optimal shallow groundwater regulation, saline soil utilization and water-saving technologies in the farmland with the aim of resolving actual agricultural production problems in saline soil areas. The researchers proposed threshold values for shallow groundwater table with no secondary salinization and developed irrigation scheme for winter wheat. In the 1990s, researches on the mechanisms and technologies of saline water irrigation were carried out to improve winter wheat grain yield and reduce fresh water utilization in the region. The threshold salinity for saline water irrigation was improved from 3 g·L^-1 to 5 g·L^-1. Meanwhile, researchers explained the reasons for the threshold value increase. In recent 10 years, the mechanisms and technological modes of multiple water resources utilization (precipitation collection, safe shallow saline water utilization, reasonable water transfer and water saving) in the farmland was analyzed. The modes included salt tolerant cultivars planting, soil salt transformation technologies, optimal irrigation schedule and organic manure reduction of salt accumulation. According to water quantity and quality, the optimal irrigation schedule was developed based on the available water resources. This included sufficient irrigation before winter, drought resistant irrigation in spring and emergency irrigation after maize sowing. On the basis of previous studies, an integrated technological mode for multiple water resources was developed. Meanwhile, the "Bohai Granary Demonstration Project of Science and Technology" was implemented, which had significant social, economic and ecological benefits. In future, research work will mainly focus on synergetic promotion of crop quality, quantity, resource use efficiency and green agriculture development based on available water and soil resources and the requirements of the local people. These works provided theoretical and technological basis for sustainable development of localized agriculture in the region.

Conservation tillage technology for water-deficit areas in the North China Plain

HU Chunsheng, CHEN Suying, DONG Wenxu

2018, 26(10): 1537-1545. doi: 10.13930/j.cnki.cjea.180615

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Abstract:
The intensive exploitation of groundwater for farmland irrigation has led to the decline of groundwater level and the development of eco-environmental problems in the North China Plain (NCP). In order to establish water saving, high yield, carbon sequestration and conservation tillage integration technology system in NCP, a long-term conservation tillage experimental platform was established from Oct. 2001 in the Luancheng Agro-Ecosystem Experiment Station, Chinese Academy of Sciences, which included six treatments, CK (deep plowing and wheat row seeding without maize straw return), CT (deep plowing and wheat row seeding with smashed maize straw incorporation), TR (rotary tillage and wheat row seeding with smashed maize straw incorporation), NT1 (non-tillage and wheat furrow seeding with maize straw incorporation), NT2 (non-tillage and wheat furrow seeding with smashed maize straw incorporation) and NT3 (non-tillage and wheat row seeding with maize straw mulching). Studies on conservation tillage theory and key technologies of winter wheat-summer maize double cropping system integrated with agricultural machinery were conducted at the platform. The agronomic water-saving conservation tillage techniques of high yield systems were widely demonstrated in NCP. The results showed that 1) conservation tillage had obvious effects on carbon sequestration, emission reduction, water saving and soil quality improvement. Long-term conservation tillage induced soil nutrient accumulation at the soil surface. Also C, N, P, K and organic matter contents were higher in the 0-5 cm soil layer than in the 5-10 cm soil layer. Soil organic carbon (SOC) stratification ratio under RT and NT1, NT2 and NT3 treatments was in the range of 1.74-2.04, which was significantly higher than that of CK and CT (1.37-1.45). After 9 years of conservation tillage, soil carbon sequestrations (0-30 cm) were 840 kg·hm^-2·a^-1, 780 kg·hm^-2·a^-1 and 600 kg·hm^-2·a^-1 under NT2, RT and CT treatments, respectively. Then after 14 years of conservation tillage, soil carbon sequestrations were respectively 540 kg·hm^-2·a^-1, 720 kg·hm^-2·a^-1 and 710 kg·hm^-2·a^-1. Long-term non-tillage reduced soil disturbance and consequently decreased the mineralization rate of soil carbon. Soil carbon was mainly fixed in organic carbon particles of soil aggregates. The fixed carbon first changed into readily decomposable organic carbon and then slowly turned into stable carbon. Calculations of global warming potential under different tillage systems showed that farmland ecosystems under non-tillage with straw return served as carbon sink, with annual carbon retention of 947-1 070 kg(C)·hm^-2 after subtracting directly or indirectly carbon emitted equivalent. Other treatments were carbon resource, with CK, CT and RT treatments annually discharging equivalent carbon of 3 364 kg(C)·hm^-2, 989 kg(C)·hm^-2 and 343 kg(C)·hm^-2 respectively into the atmosphere. The mechanism of soil microbial diversity under conservation tillage was as follows:conservation tillage significantly improved the diversity indexes of soil fungi communities, bacteria communities, ammonia-oxidizing bacteria communities and denitrifying micro-organism communities with nirK gene. However, it had little effect on the diversity index of ammonia-oxidized bacteria communities and denitrifying micro-organisms communities with nirS gene. Conservation tillage showed significant water-saving effect, which resulted from improvements in soil structure, water-reservoir porosity and saturated hydraulic conductivity. Straw mulching also effectively reduced soil evaporation. 2) Non-tillage plus straw mulching with minimum soil evaporation model was established in winter-wheat/summer-maize double cropping system area. The unit of 4JS-2 straw combing press machine and 2BMF-6 non-tillage sowing machine with zero evaporation were developed, which reduced the operating rate by 45.2% and operation cost by 33.3%, compared with 2BMF-6/12 non-tillage sowing machine currently promoted. 3) A new soil rotation tillage model of deep plowing and deep sub-soiling every 3 years in non-tillage soil was established and integrated with water-saving, high-yielding and protective tillage technology system. A series of technical regulations of Hebei local standards in terms of conservation tillage of winter wheat/summer maize double cropping system were suggested. Cooperated with the Agricultural Bureau and Agricultural Machinery Bureau of Hebei Province, we demonstrated and promoted conservation tillage technologies in Hebei Province with remarkable social and ecological benefits. The main results won the first prize of Hebei Science and Technology Progress Award in 2013.

Practice and prospect of ecological restoration and water conservation for the rocky mountain areas in North China

CAO Jiansheng, ZHANG Wanjun, YANG Hui, HAO Xiaohua, LIU Xiuping, WANG Hehui

2018, 26(10): 1546-1554. doi: 10.13930/j.cnki.cjea.180663

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Abstract:
The construction of ecological civilization and the protection of ecological environment are inevitable requirements of harmonious coexistence between man and nature. It is the basis of the realistic needs for realizing sustainable development of the economy and society for better ecological environment and beautification of China. In view of the severe degradation of the ecosystem, low environmental bearing capacity, weak infrastructure, poor natural conditions and resources, and poverty issues in the Taihang Mountain region, the Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences began (in the 1980s) a series of study on ecological restoration and sustainable development in low and hilly regions on the central region of the eastern slope of Taihang Mountain. Through 30 years of research, a relatively complete ecological restoration and management system for the rocky mountain areas in northern China has been established. This has provided experiences and demonstration for the construction of ecological civilization and protection of ecological environment in the mountain area. It has also helped the poor by fostering sustainable socioeconomic development. From the review and prospect of researches in the past 30 years, the paper summarized and discussed the practice and prospect of ecological restoration and water conservation in rocky mountain areas. The construction of forestry eco-engineering in the Taihang Mountain has mainly experienced three stages in the past 30 years. The initial stage was the determination of approaches and technical theories of ecosystem restoration in degraded mountain areas during the period from 1986 to 1996. There was also forestry eco-engineering that focused mainly on soil and water enrichment. The second stage was the study of key factors affecting the restoration and reconstruction of degraded mountain ecosystems and effective techniques and measurements of problem solutions during the period from 1997 to 2007. Specifically, in the runoff forestry research, a formula for calculating the distance between two soil and water enrichment projects in the Taihang Mountain was established. In terms of precipitation transformation and water transfer, the characteristics of seepage flow in shallow weathered and fractured rock masses and its response to the process of vegetation water consumption were determined. And the basic recharge path of precipitation-soil water-crack water in the binary structure of rock-soil, and the transfer regulations of preferential flows in interface of rock and soil and in crack nets were clarified. For regulating and utilizing precipitation resource, a new material for biological rainwater collection and the corresponding method for its' utilization were developed. The third stage was the exploration and development of mountain ecological industry and regional sustainable development since 2008. The technology for water-storage capacity of economic forest soil, afforestation techniques for difficult sites in rocky mountain areas, controlling techniques of ecological belts in economic forests, sound industrial development techniques for engineering zone in Beijing-Tianjin Aeolian Source, and undergrowth and circular economy, eco-tourism and other ecological industrialization technology systems had also been developed. Based on current researches, the future researches will be expanded to mountain regions in the upper reaches of Xiong'an New District, where has a high population density with frequent anthropological activities. The researches will mainly focus on the followings:a) integration of ecological environment and climate change monitoring in mountain, water, forest, lake and grass regions, including land greening, landscape construction, water conservation, soil erosion control and pollution prevention; b) investigation on succession processes and main driving factors from mountain shrub ecosystem to forest ecosystem under modern disturbance conditions; c) exploring the formation mechanism of flood and drought disaster in mountain regions, the regulation of precipitation resources and conservation of water resources; d) establishment of mountain ecological economic system by using industrial ecology with the ecological industrialization as the main focus. The findings will provide the scientific basis and technical support for building stable structures, well-functioning ecological environment support systems for Beijing-Tianjin-Hebei Area. It also provides scientific references for water conservation and management of production, ecological functions of mountain ecosystems.

Safe utilization of farmland contaminated with heavy metals in China: Progress and outlook

YANG Shushen, SUN Yanqin, ZHENG Xin, LI Xiaofang

2018, 26(10): 1555-1572. doi: 10.13930/j.cnki.cjea.180573

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Abstract:
Farmland heavy metal pollution is now a serious problem in China. Food heavy metal contents in some agricultural regions exceed the national limits and threaten human health and the development of economy and society. Meanwhile, farmland resources are very limited in China. Therefore, farmland heavy metal pollution needs to be resolved urgently. Among available remediation tools, the physical or chemical ones are costly and are not suitable for the slightly/moderately contaminated farmland at a large scale. The phytoextraction method is cost-effective and environmentally friendly, but requires a long time. Overall, techniques aiming at heavy metal removal have limitations in solving heavy metal pollution in farmland. Safe utilization is to produce safe agricultural products, without removing the heavy metal content in soil purposefully. Safe utilization of heavy metal contaminated farmland is preferable for China at this stage. Cultivation of low-accumulation crops is an important option for the safe utilization scheme. A number of low-accumulation cultivars of grain crops and vegetables have been screened out in China. Genetic engineering has potential in breeding of low-metal-accumulation crops. Soil additives such as clay minerals, organic wastes and biochar can inhibit heavy metal uptake of crops by immobilization of heavy metals in soil, via ion-exchange, precipitation, etc. However, use of soil additives may impact soil qualities by changing soil structure, loss of nutrition and secondary pollution. Some microorganisms showing strongly resistant to heavy metals have already been used to inhibit the heavy metal uptake of crops. Genetically modified microbes possessing stronger immobilization ability should be paid more attention. Furthermore, agronomic strategies including fertilization, water management, and intercropping can transform the heavy metal forms in soil and influence the heavy metal uptake by crops. However, the crop yield and quality like nutrient content can also be influenced by the safe utilization measures. Efforts should be made to get a balance between low accumulation of heavy metals and crop yield and qualities. In the future, researches may focus on the integration of various remediation techniques for the large-scale field implementation.

Advances in research on floral meristem determinacy mechanisms in plants

ZHANG Ke, GUO Xinxin, LIU Xigang, GUO Lin

2018, 26(10): 1573-1584. doi: 10.13930/j.cnki.cjea.180653

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Abstract:
In higher plants, plant tissues and organs are generated from meristems. Shoot apical meristem (SAM) gives rise to all of the aboveground parts for the entire life of plant through continuous production of new organ primordial, including floral meristem (FM) which finally develops as flowers. Floral development is based on the balance between FM meristem maintenance and termination. At the initial stage, floral stem cells proliferate and produce defined number of floral organs based on the "ABC model" rules. At this stage, FM activity is maintained mainly by CLV (CLAVATA)-WUSCHEL (WUS) feedback loop. WUS encodes a homeodomain containing protein. It promotes stem cell marker gene CLV3 expression when WUS expression is low. It also inhibits CLV3 expression when WUS expression is high. Thus FM activity is maintained and can promote initiation of floral organs. However, after two carpels primordia initiation, FM activity is terminated in a process called FM determinacy. FM determinacy is a dynamic and multi-step process in which WUS plays a central role. WUS expression is regulated by many transcription factors related to floral organ identity[AGAMOUS (AG), APETALA2 (AP2) and SUPERMAN], environmental signals (light, temperature, etc.), plant hormones (auxin, cytokinin, gibberellin, etc.) and epigenetic-related factors (histone modification, chromatin remodeling, non-coding RNA, DNA methylation, etc.). Using model plant Arabidopsis, our study noted that AG terminates FM maintenance by directly repressing WUS through chromatin higher structure (chromatin loop), formed by AG and one of Polycomb Group components TERMINAL FLOWER2/LIKE HETEROCHROMATIN PROTEIN1 (TFL2/LHP1); binding to WUS5'-TSS (transcription start site) and WUS3'-CRE (cis-regulatory element). DNA TOPOISOMERASE 1 (TOP1α) inhibited WUS expression by modulating WUS nucleosome density to inhibit DNA accessibility, which also participated in the progress. AUXIN RESPONSE FACTOR3 (ARF3) induced by auxin regulated FM determinacy by repressing cytokinin biosynthesis[inhibiting cytokinin synthesis genes ISOPENTENYLTRANSFERASE (IPTs) and LONELY GUY (LOGs)] and signaling[inhibiting cytokinin receptor gene ARABIDOPSIS HISTIDINE KINASE4 (AHK4)], which clarified how auxin and cytokinin integrated to regulate FM activity; FAR-RED ELONGATED HYPOCOTYL 3(FHY3) activated SEPALLATA2, but inhibited CLAVATA3 to regulate meristem determinacy and maintenance, which shed light on how light affected meristem activity. As 3D (3-dimentional) genome organization technology developed, the importance of the impact of chromatin structure on gene expression was realized and more techniques were developed and improved. Using the newly reported methods, FM determinacy mechanism required further in-depth studies. What was more was that since plant FM determinacy was regulated precisely and accurately, any defects in FM determinacy affected seed development. Exploitation of FM determinacy mechanism had the potential to importantly contribute to agricultural production, which was helpful for ensuring reproductive success, seed development and yield of agricultural crops (maize, tomato, etc.). In this review, we gave a short introduction on floral organ identity in Arabidopsis thaliana and the mechanism of meristem maintenance and differentiation. Then we mainly focused on FM determinacy, including some recent studies by our group. Finally, we advanced the application of fundamental studies in crop yields and further prospects for research.

Advances in signal transduction of PAMP-triggered immunity in plants

YANG Jun, LYU Dongping

2018, 26(10): 1585-1592. doi: 10.13930/j.cnki.cjea.180533

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Abstract:
Plant disease is one of the most important factors adversely affecting agricultural production. The resistance of plants to pathogens depends on the plant innate immunity system. The study on plant innate immunity will provide insight into the breeding of disease-resistant crops. Plant innate immunity is composed of two intertwined layers:PTI (PAMP-triggered immunity) and ETI (effector-triggered immunity). In recent years, a series of significance progress has been made in the study of PTI, which is triggered by PAMPs (pathogen-associated molecular patterns). Upon the perception of PAMPs by the cell surface-localized receptors, the immune signaling is transduced through receptor-like cytoplasmic kinase (RLCK) BIK1 (Botrytis-induced kinase 1), MAPK (mitogen-activated protein kinase) cascade, and CDPKs (calcium-dependent protein kinase), resulting in ROS (reactive oxygen species) burst, stomata closure, and expression of immune-related genes, which limit the colonization of infectious pathogens. Importantly, the innate immunity is regulated at different levels to ensure the optimal intensity and duration of immune responses. In this paper, we reviewed the advances in the molecular mechanisms and signal transduction of PTI in recent years, including the discoveries of FLS2 and other immune receptors, the functions of diverse components of innate immunity signal transduction pathway, the transcription factors involved in innate immunity, the regulation of immune signaling, and the application of innate immunity in the disease-resistance breeding. We also discussed future perspectives, and we thought that the studies on innate immunity signaling in crops and crop-fungi patho-system should be given the highest priority. Furthermore, the combination of the theories of plant innate immunity with the gene editing technologies would definitely provide new opportunities for crop disease-resistance breeding.

Application of high-throughput DNA sequencing in microbial ecology

WANG Xinzhen, WANG Fenghua, SUN Ruibo, LIU Binbin

2018, 26(10): 1593-1600. doi: 10.13930/j.cnki.cjea.180695

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Abstract:
Microorganisms play essential roles in natural and artificial ecosystems. However, only a small portion of microorganisms can be cultured and isolated in most ecosystems, which greatly limits our understanding of microbial community composition, ecological function and their potential applications. The novel molecular techniques, especially high-throughput sequencing, have provided advantages for further exploring the diversity, composition and ecological functions of microbial community. High-throughput sequencing is a culture-independent technology capable of deep, rapid and accurate detection of genetic information. With the update of the high-throughput sequencing technology, the sequencing throughput, read length and accuracy have been dramatically improved, and the cost has greatly declined. During the past decade, high-throughput sequencing technology has been rapidly applied in the microbial ecological studies with various types of samples such as soil, water and gut microbial communities. Amplicon and metagenomic sequencing are most widely used strategies for environmental samples. Amplicon sequencing refers to sequencing the PCR products of target gene fragments amplified with specifically designed primers. The 16S rRNA gene of prokaryotes and the 18S rRNA and ITS genes of eukaryotes are most commonly used marker genes to conduct microbial taxonomic analysis. In addition, functional genes such as nirK, nirS and nosZ genes of denitrifying bacteria, amoA gene of ammonia-oxidizing bacteria, and ureC gene of urea hydrolytic bacteria are frequently adopted to study the diversity of functional microorganisms. In metagenomics, sequencing is performed on the genomic DNA directly extracted from environmental samples therefore avoiding the bias from PCR. Theoretically this method can provide a representation of all genomes in the sample and can be used for fully exploring the genetic diversity, functional potentials and metabolic pathways of both cultured and uncultured microorganisms. Metagenomic sequencing technology has been applied in the field of medical diagnosis, human health, biological energy, environmental restoration and agricultural ecology, etc. and has provided us new insights into taxonomic diversity, ecological function, evolutionary succession and interaction in the complex microflora. The application of metagenomic sequencing technology to the field of virology is referred as viral metagenomics. Viruses are not only related to various diseases of crop, animal and human, but also indispensable in the natural ecosystems, and play an important role in regulating host diversity and community succession, mediating gene transfer between microbes, and promoting global biogeochemical cycles. Viral metagenomics has recently gained momentum in application in the field of environmental science to reveal the genetic diversity, explore the novel species of viruses, and investigate their interactions with environmental factors.

2018 Vol. 26, No. 10