中国生态农业学报(中英文)

Research prospects and progress on chilling injury of economic forest and fruit trees in South China

PING Xiaoyan, ZHOU Li

2018, 26(4): 467-479. doi: 10.13930/j.cnki.cjea.170725

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Abstract:
Chilling injury has posed severe threat to the environment and agroforestry in South China and it has gained considerable research attention in terms of species sensitivity and injury risk with the unfolding global climate change. To thoroughly understand the current status of chilling injury, this study summarized and reviewed progresses in chilling injury researches in South China using relevant literatures in recent ten years. The definition and types of chilling injury, differences between chilling injury and other common types of low-temperature injury, mechanism of chilling injury and its controlling factors, methods of identification and classification of chilling injury, critical temperature of chilling injury of different species in South China, elements and methods of risk assessment of chilling injury, specific defensive practices and appropriate management strategies after chilling injury were discussed in this review. There were the needs for future researches focusing on developing comprehensively standardized chilling injury index, transfer and quantitative expression of cold-resistant genes, dynamic and quantitative evaluation of regional chilling injury risk and risk assessment of chilling injury under global climate change. Also in the future researches, the following aspects should be pay more attention, i. e. accurate and quantifiable grading of chilling injury, early warning and risk assessment of chilling injury using remote sensing (RS) and geographic information system (GIS) techniques, integration of chilling injury mechanisms and field survey, and consideration of both biological characteristics of plant species and topographic variations. There was the potential for any such future researches to benefit the optimization of plant distribution pattern, accurate early warning for chilling injury and sustainable development of economic forest and fruit trees in South China.

The plant diversity of agro-landscapes in typical maize planting areas in the Northeast Plain, China-A case study of Changtu County

BIAN Zhenxing, LI Xiaolu, YU Miao

2018, 26(4): 480-492. doi: 10.13930/j.cnki.cjea.170955

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Non-cropped habitats in agricultural landscapes constitute an important landscape for biodiversity preservation. Such habitats in agro-ecosystems can support both food production and biodiversity. In order to explore the relationship between plant species diversity and heterogeneity of agricultural landscape, and furthermore, to probe the suitable proportion of non-cropped habitats in agricultural landscape, we investigated plant diversity in Changtu County in the Northeast Plain, China. A total of 20 sampling plots (1 km×1 km) were selected for area proportions 0-50% of non-cropped habitats, and were divided into five groups according to area proportion of non-cropped habitats, which were 0-10%, 10%-20%, 20%-30%, 30%-40% and 40%-50%. The plant species in non-cropped habitats were investigated using the Braun-Blanquet method. The surveyed non-cropped habitats included woodland, grassland, ditch, orchard and field road. The heterogeneity indexes of agricultural landscape with different proportions of non-cropper habitats were calculated. The results showed that plant species diversity and evenness of agricultural landscapes gradually increased initially and later decreased with increasing area proportion of non-cropped habitats. Peak plant species diversity and evenness were in landscapes with 20%-30% area of non-cropped habitats. Meanwhile, plant species richness gradually increased initially and decreased later when area proportion of non-cropped habitats was 0-40%. However, peak plant species richness was in agricultural landscape with 40%-50% area of non-cropped habitats. The Shannon diversity index, Shannon evenness index of agricultural landscape increased with increasing of area proportion of non-cropped habitats, while landscape contagion metrics showed contrary tendency, indicating that lower area proportion of non-cropped habitats induced higher landscape dominance. The plant species with highest important values in different non-cropped habitats was Gramineae plants, but the species were different. The order of dominant degree of dominant species was orchard, ditch, grassland, field road and woodland. Species diversity and evenness in orchard, grassland and ditch were significantly higher than those in woodland and field road. Species richness (from high to low) was grassland, woodland, ditch, orchard and field road. There were obvious variation in plant community diversity among orchards, grasslands and ditches. The correlation between landscape heterogeneity and species diversity decreased from grassland to orchard, ditch, field road and to woodland. Thus the optimum area proportion of non-cropped habitats was 20%-30% within agricultural landscapes in typical maize planting areas in the Northeast Plains, China. Woodland and ditch had a positive effect on species diversity and on maintenance and conservation of hygrophytes. Different non-cropped habitats disturbances resulted in different correlation coefficients between landscape heterogeneity and plant species diversity. Thus future research should concentrate on comprehensive analysis of various factors such as area proportion of non-cropped habitats and habitat disturbances that influenced biodiversity, ecosystem services and agricultural production.

Spatial distribution characteristics of fungal population in microbial fermentation bed for pig rearing

XIAO Rongfeng, LIU Bo, ZHU Yujing, RUAN Chuanqing, LIU Guohong, WANG Jieping

2018, 26(4): 493-504. doi: 10.13930/j.cnki.cjea.170904

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Pig rearing on microbial fermentation bed system is a new environmentally-friendly breeding method. Micro-organisms are critical for deodorization and decomposition of pig excrement. The aim of this study was to investigate the spatial distribution characteristics of fungal population in the litters of microbial fermentation bed at Fuqing Agriculture Modern Facilities Base, Fujian Academy of Agricultural Sciences, China. A total of 32 litter samples were collected in space and culturable fungi in each sample isolated and identified based on morphological characteristics and molecular identification. The spatial distribution characteristics of the fungal population in the fermentation bed were evaluated by analyzing spatial distribution frequency, spatial distribution index, diversity index and niche characteristics. This was critical for laying the needed basis for the management of pig fermentation beds, utilization of pig manure and control of pig diseases. From the study, a total of 18 fungal species were isolated from 32 samples, belonging to 10 different genera. The dominant genus was Aspergillus, which had 7 species. There were significant differences in the species and amount of fungi at different spatial samples. There were 1-4 species and 4.0×10²-5.8×10⁵ colonies·g^-1 of each species. Mucor racemosus and Penicillium citrinum had high frequency and population with a frequency distribution above 10. The amounts of Scopulariopsis brevicaulis, A. nidulans and A. candidus exceeded 2.0×10⁵ colonies·g^-1, belonging to the high population amount. Based on the results of the 6 spatial distribution indices and the Taylor power law test, the distribution of fungal population in fermentation beds had an aggregated distribution pattern. The results of population diversity index analysis for the 32 spatial samples showed that fungal population had obvious diversity, with aggregated and uneven distribution pattern in fermentation beds. Fungal population had higher richness, evenness and dominance in both 2-A and 3-D samples, which included species with higher frequency and population. This included M. racemosus, Cladosporium oxysporum and A. nidulans. However, fungal population had lower richness, evenness and dominance in both 1-A and 1-B samples that harbored more fungi with a frequency less than three times. This included A. candidus, S. brevicaulis and Geotrichum candidum. The analysis of the fungal population niche characteristics showed no positive correlation between niche breadth and overlap of the fungi. M. racemosus and C. oxysporum were the widest adaptability species, with ecological width of 7.60 and 5.18, respectively. However, the six fungal species (A. candidus, A. chevalieri, A. terreus, S. brevicaulis, F. equiseti and Chaetomium sp.) were the narrow adaptability species, with ecological width range of 1.00-1.10. For niche overlap, M. racemosus overlapped with 12 species, but C. oxysporum overlapped with only two species. In conclusion, fungal population had obvious community diversity in microbial fermentation bed system for pig rearing. The spatial distribution characteristics of fungi had aggrega-tion and uneven distribution pattern. M. racemosus and C. oxysporum were the dominant species, with a wide distribution and strong adaptability.

Study of ecological carrying capacity index based on three-dimension ecological footprint model-A case study of Hebei Province

SHEN Wendong, XU Hao

2018, 26(4): 505-515. doi: 10.13930/j.cnki.cjea.170643

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Hebei Province is in the north of North China Plain and surrounds two major cities (Beijing and Tianjin) with excellent geographical conditions. With the rapidly developments in economy, society and other fields, ecological environment has been faced with serious risk in Hebei Province, such as water shortage, water pollution, urban air pollution, marine pollution, forest destruction and land desertification. To ensure sustainable development, the effective management of natural assets from the perspective of eco-economy is critical. It is therefore significant to measure the gap between demand for natural resources and the actual available nature resources in Hebei Province. By extending the depth of footprint in Niccolucci's 3D ecological footprint model from ≥ 1 to ≥ 0 and using a unified 3D model framework to analyze ecological surplus state, a unification of resource flow and inventory occupancy was built for accounting human production and livelihood. From this, the ecological footprint, deficit surplus and depth of footprint were built for Hebei Province for the period 2002-2016. Then, the study determined the current land load level through calculating land pressure indexes by using the extended Niccolucci's 3D ecological footprint model. The land pressure indexes included agricultural products pressure index, water resource pressure index, carbon sink pressure index, construction pressure index and comprehensive land pressure index. The results showed:1) per capita ecological footprint of Hebei Province steadily increased in 2002-2016, but per capita productive ecological land area changed little. 2) The depth of ecological footprint of Hebei Province was huge, especially for waters areas and fossil fuel land. The consumption of natural resources due to production in Hebei Province was far greater than the flow of resources, causing high consumption of resources stock in Hebei Province. 3) Ecological deficit in Hebei Province was deep, which was 3.26 hm²·cap.^-1 in 2016. 4) The pressure indices of agricultural products, water resources, carbon sink and comprehensive land pressure index were all greater than 1, and except agricultural products pressure index, the values of other three pressure indexes were above 10, indicating that Hebei had serious land pressure. The livelihood and production activities of the residents were serious burden on ecological productivity of the land. The above results indicated that demand for resources in Hebei Province was greater than supply and that sustainable development was seriously hampered. To improve sustainable development level of Hebei Province, it was necessary to change economic development mode, adjust industrial structure, develop circular economy and improve resource utilization efficiency.

Coupling effect of alternate wetting and drying irrigation and nitrogen rate on organic acid in rice root secretion at heading stage

XU Guowei, LU Dake, WANG Hezheng, JIA Fujun, CHEN Mingcan

2018, 26(4): 516-525. doi: 10.13930/j.cnki.cjea.170803

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Soil water and nitrogen conditions are the principal factors that affect crop growth and formation. Clarifying effects of soil water and nitrogen conditions and their coupling on grain yield of rice (Oryza sativa L.) have significant implications for high production efficiency and yield. There is extensive domestic and foreign research on the interactions of soil water and fertilizer. Specific focus has been put on ground parameters such as crop growth development, dry shoot formation, physiological function, hormone change, nutrient absorption and utilization, water use efficiency, etc. However, there is less work on the characteristics of root secretion, including changes in organic acids in roots. Research on the relationship between organic acid content and nitrogen utilization and the related interactions is also inconsistent and therefore inconclusive. The purpose of this study was to investigate the performance of root secretion under different nitrogen and water regimes and analyze the effect of the interaction of alternate wetting and drying irrigation and nitrogen levels. To that end, a pot-soil experiment was conducted using a mid-season japonica rice cultivar 'Lianjing 7' under different nitrogen rates[0N, MN (240 kg·hm^-2) and HN (360 kg·hm^-2)] and three irrigation regimes[keeping water (0 kPa), alternate wetting and moderate drying (-20 kPa) and alternate wetting and severe drying (-40 kPa)] in 2015 and 2016. The results showed that there was remarkable interaction between nitrogen rate and irrigation regime with the results similar for the two years. Under the same nitrogen rate, tartaric acid, citric acid, oxalic acid, malic acid, succinic acid, total organic acid and amino acid secretion of rice root at heading stage were higher (respectively by 13.2%, 8.7%, 27.3%, 40.0%, 6.7%, 6.3% and 6.4%) in treatment of alternate wetting and moderate drying than in treatment of keeping water flood irrigation. The nitrogen agronomic utilization and partial productivity of rice were increased by 4.1% and 1.7% respectively. The secretion amounts of tartaric acid, citric acid, oxalic acid, malic acid and succinic acid at heading stage decreased (respectively by 16.4%, 4.5%, 12.8%, 41.7% and 5.6%) under the treatment of alternate wetting and severe drying than under the treatment of keeping water. This also reduced total organic acid and amino acid in roots and overall nitrogen use efficiency. Under the same irrigation condition, nitrogen application accelerated the root secretion of tartaric acid, acetic acid, malic acid and succinic acid, but decreased the secretion of oxalic acid and citric acid at heading stage of rice. The differences in tartaric acid, acetic acid, malic acid and succinic acid secretion by roots were small between MN and HN treatments. Nitrogen application has positive effects on total organic acid, amino acid, malic acid, succinic acid secretion. Also its interaction effect with alternate wetting and moderate drying was positive, while the interaction effect with alternate wetting and sever was negative. Correlation analysis indicated that citric and oxalic acids secretion by rice roots was significantly positively correlated with nitrogen utilization. However, acetic acid was negatively correlated with nitrogen use efficiency. The results of the study suggest that increasing root secretion capacity through appropriate regulation of irrigation coupled with nitrogen rate increased nitrogen use efficiency and thereby promoted high yield of rice.

Effects of arbuscular mycorrhizal fungi on antioxidant metabolism and rhizo-spheric micro-organism of soybean (Glycine max) under drought stress

HU Zhenxing, LIU Ling, CHEN Liping, CHEN Ming'ai, CHEN Ling

2018, 26(4): 526-537. doi: 10.13930/j.cnki.cjea.170517

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Arbuscular mycorrhizal fungi (AMF) not only improves nutrient absorption, but also enhances the resistance of host plant to stress such as drought. AMF inoculation has become one of the effective ways to resist drought stress. To explore the drought resistance mechanism of soybeans (Glycie max) inoculated with AMF, an experiment involving soybean variety 'Guichundou 103' as material was conducted. After inoculation with Claroideoglomus etunicatum (C.e), the effects of C.e on activities of antioxidant enzymes and C/N/P-cycle-related enzymes were investigated by collecting rhizospheric soil of soybean under drought stress. The changes in bacterial and fungal community diversities in rhizospheric soil were analyzed by denaturing gel gradient electrophoresis (DGGE) and other technologies. The results showed that activities of SOD, POD, sucrase, urease and phosphatase, free proline (FP) content, number and indexes of Shannon-Wiener diversity, richness and evenness of microorganisms in rhizospheric soil, as well as biomass and plant height of soybean with C.e inoculation (+AM) treatment were significantly higher than those without C.e inoculation (-AM) treatment under normal water supply condition. On the contrary, MDA content decreased significantly. Under drought stress (+D), MDA content with +AM treatment was lower and higher than that with -AM+D and +AM treatment, respectively. FP content was both higher than those of two treatments. The other indexes mentioned above along with band numbers of rDNA fragments of rhizospheric soil bacteria and fungi population were significantly higher than those with -AM+D treatment, and lower than those with +AM treatment. The bacterial and fungal communities of rhizospheric soil of -AM and -AM+D treatments belonged to different groups, while those of +AM treatment were clustered together with those of +AM+D treatment. In conclusion, +AM+D treatment obviously promoted the activities of antioxidant enzyme system, alleviated inhibition of drought on soil enzyme activities, kept high stability of cell membrane system, retained high population number and microbial structure diversity, promoted circulation and transformation of C, N and P in rhizospheric soil, improved drought resistance and effectively stimulated soybean growth. These results will lay a critical foundation for promoting sustainable development of agroecological systems.

Study on nitrogen nutrition diagnosis and fertilization recommendation of winter wheat using canopy digital images from cellphone camera

XIA Shasha, ZHANG Cong, LI Jiazhen, LI Hongjun, ZHANG Yuming, HU Chunsheng

2018, 26(4): 538-546. doi: 10.13930/j.cnki.cjea.180184

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Abstract:
Digital cameras have been successfully used in nutrition diagnosis of crops. Few researches were reported on the application of cellphone cameras on nutrition diagnosis and precision fertilization of crops, though the cellphone cameras have various advantages, such as portability, handleability and universality. In this study, we used Samsung and Xiaomi smart cellphones to photograph winter wheat canopy at jointing stage from four shooting angles, frontlighting looking down, frontlighting overlooking, backlighting looking down and backlighting overlooking. The color parameters of achieved winter wheat canopy images were extracted, processed and analyzed. And their correlations with traditional nitrogen nutrition indexes were analyzed. According to the statistical analysis of the correlation, appropriate color parameters were selected, and the nutrition diagnosis model was established with color parameters and nitrogen nutrition index. Then the model was fitted to establish indicator systems of diagnosis of nitrogen nutrition and recommendation system of fertilization for winter wheat. The aim of the study was to provide references for application of smart cellphone on precision fertilization of crops. The results showed that there was no remarkable difference in the color parameters of canopy images taken with different types of smart cellphones. However, a certain difference was observed in color parameters of canopy images taken from different shooting angles. More than half of color parameters of canopy images taking from the view of backlighting overlooking were significantly correlated with traditional nutrient indexes. Furthermore, the results indicated that the color parameters VARI[(G-R)/(G+R-B)] and R/(R+G+B) both had outstanding correlations with leaf SPAD and stem nitrate concentration. And VARI was found to be the best, and therefore, selected as the sensitive color parameter for winter wheat nitrogen nutrition diagnosis. The diagnosis model was stem nitrate concentration=1.481×10⁶×VARI^4.987. According to the equation, the nitrogen nutrition status of winter wheat was normal when VARI was between 0.201 3 and 0.250 9. The nitrogen application rates under different VARI values were calculated for different target yields of winter wheat. The results were applied to develop cellphone software for nitrogen nutrition diagnosis and fertilization recommendation of winter wheat. In summary, it was possible and applicable to take photographs of canopy from the view of backlighting overlooking with smart cellphone and extract VARI color parameter to diagnosis nitrogen nutrition status. The results provided technical support for the diagnosis of nitrogen nutrition and recommendation of fertilization of winter wheat based on cellphone camera.

Spatio-temporal analysis of winter wheat yield gaps in Henan Province using AEZ model

WANG Lianxi, LU Yuanyuan, LI Qi, HU Zhenghua, WU Dongli, ZHANG Yang, WANG Tian

2018, 26(4): 547-558. doi: 10.13930/j.cnki.cjea.170843

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Global climate change has become one of the most severe environmental problems facing human society. Agriculture is among the sectors with the most sensitive response to climate change. The analysis of yield gaps could reveal the factors limiting the growth and production of crops in various regions. Henan Province is the most important commodity grain base in China, with rich climatic resources and remarkable climate change. Analysis of yield gaps and change trend of winter wheat yield in Henan Province are critical for understanding the impact of climate change on the potential productivity of winter wheat in the province. It also can be used to draw on advantages and avoid disadvantages of climatic change, making full and rational use of climatic resources of winter wheat. Current researches on the impact of climate change on crop yield gaps have often focused on large-scale analysis, few people divided the study area into small pieces. To improve the accuracy of simulated effects of climate change, Henan was divided into five planting areas, which were northern Henan planting area (Ⅰ), eastern Henan planting area (Ⅱ), shallow mountain hilly basin planting area (Ⅲ), Huaibei Plain and Nanyang Basin planting area (Ⅳ) and southern Henan planting area (Ⅴ). Data obtained from 14 meteorological stations were used in AEZ model to simulate potential productivities of winter wheat for 1961-2013 in Henan Province. Then yield gaps were calculated, which were gap between photosynthetic potential productivity and light-temperature potential productivity (YG_1-2), gap between light-temperature potential productivity and climate potential productivity (YG_2-3) and gap between light-temperature potential productivity and average field yield (YG_2-a). The results showed that photosynthetic potential productivity of winter wheat in Henan Province decreased in 1961-2013. The light-temperature potential productivity increased and climate potential productivity remained basically unchanged. Analysis of average field yield showed significant differences in average outputs at 14 meteorological stations and the trend in winter wheat output gradually increased. YG_1-2 of winter wheat decreased, while YG_2-3 followed a Ⅴ-shaped trend with the valley occurring in 1981-1990. YG_2-a in Ⅰ, Ⅱ and Ⅴ areas had a decreasing trend, while that in Ⅲ and Ⅳ areas initially increased and then decreased. In terms of spatial change, YG_1-2 and YG_2-3 of winter wheat declined from north to south, while YG_2-a increased from east to west in Henan Province. The order of yield increase potential of winter wheat for each area was Ⅲ > Ⅴ > Ⅳ > Ⅱ > Ⅰ. Agronomic conditions were the main factors driving the dwindling gaps in winter wheat yield in Henan Province. By improving agronomic conditions (e.g., varieties, modern agricultural technology, reasonable pesticide and fertilizer use, and rational arrangement of high-quality regions), it was possible to reduce the gaps in winter wheat yield in the study area.

Improvement and applicability of winter wheat water budget index in Gansu Province

JIA Jianying, HAN Lanying, WAN Xin

2018, 26(4): 559-566. doi: 10.13930/j.cnki.cjea.170817

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Winter wheat is a major grain crop in Gansu Province, where precipitation is the most limiting factor for winter wheat production. The uneven space-time distribution of precipitation results in perennial winter wheat drought in Gansu Province. It is therefore practically important to accurately monitor drought and quantitatively evaluate disaster losses of winter wheat in Gansu Province. This can provide the needed scientific basis for decision-making departments to formulate agricultural disaster prevention and mitigation measures towards regional food security. In this study, we collected data on soil water content and winter wheat growth conditions in three agronomic observatory stations. Data were also collected on meteorological conditions, yield and drought disaster in 38 winter wheat growing counties for the period 1981-2014. Based on soil water storage during fallow period and on water budget for winter wheat development stage, crop water budget index was revised. There was a high correlation among crop water budget index and soil water storage, yield factors and losses. Therefore, it objectively, accurately and quantitatively reflected the impact of drought on winter wheat yield in Gansu Province. A yield-factor assessment model and a yield-loss assessment model were developed in the study based on the revised water budget index. The results showed that while the yield-factor assessment model passed 0.01 test of significance, and much of the yield-loss assessment model passed 0.05 test of significance. The assed and measured values of winter wheat yield factors passed F-test (P < 0.01). The validation results of the yield loss assessment model showed that 68.4% of wheat growing counties passed F-test (P < 0.05), which more accurately assessed the loss due to drought in Gansu Province. The revised crop water budget index objectively reflected the drought of winter wheat in Gansu Province and the established assessment model accurately estimated the loss due to drought, which provided a reliable reference for application.

Maize production status and yield limiting factors of Kenya

LI Xiaoxin, CHEN Suying, Stephen O. ALUOCH, Peter S. MOSONGO, CAO Jiansheng, HU Chunsheng

2018, 26(4): 567-573. doi: 10.13930/j.cnki.cjea.170632

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Maize as the main food crop in Kenya, is very important for reducing hunger and ensuring the country's food security. This paper introduced the present situation of maize production from cultivation, planting distribution and change of maize yields from 1961 to 2014. According to the natural planting environments and the local agricultural technique, the limiting factors of maize production were analyzed. Water limitation, fertilizer shortage and poor quality of maize seeds were the main factors limited the yield increasing of maize. Base on the analysis results of the relationship of maize yields with water and fertilizer inputs, this paper gave some advices for increasing maize yield in Kenya. First, the drainage and rain-harvesting technology cooperated with irrigation technique should be implemented to regulate and redistribute precipitation in maize growing season. The second was increasing fertilizer application amount, especially the use of phosphate fertilizer, to ensure the health growth of maize. The third was straw returning technology to improve soil structure. This study provided a reference for rain water utilization, fertilization and tillage techniques to get high yield in the rainfed maize planting area of Kenya.

Research progress in agricultural application of nitrogen-fixing cyanobacteria

BAO Jiangqiao, ZHOU Yiwei, HE Luxi, LI Qi, LI Huashou, ZHANG Dinghuang, HE Hongzhi

2018, 26(4): 574-583. doi: 10.13930/j.cnki.cjea.170947

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As autotrophic photosynthetic micro-organisms with the ability to fix nitrogen and carbon into the soil, nitrogen-fixing cyanobacteria belong to an important microbial resource. The first report on their application in agriculture came from India in 1939. Although it subsequently had global attention, large-scale popularization and application of nitrogen-fixing cyanobacteria were not implemented in the end. The reasons were related to the wholesome use of chemical fertilizers in the world and the immature application technology of nitrogen-fixing cyanobacteria with high complexity, high cost and low reliability. For the former, although chemical fertilizers promoted crop production dramatically, its negative effects on agriculture and the eco-environment were already a growing concern in the public thinking. For the latter, with the development of new technologies in large-scale production and inoculation of nitrogen-fixing cyanobacteria, these defects were gradually eliminated. In the big background of current national policy advocating for "reduction" and "low carbon" development in agriculture, the application of nitrogen-fixing cyanobacteria (as green bio-fertilizer) has ushered in a new development opportunity for future application. In addition to bio-fertilizers in agriculture, studies in recent years have shown that nitrogen-fixing cyanobacteria were used in crop growth regulation, bio-pesticide development, agricultural pollution control and agro-ecological protection. This paper reviewed the progress in studies on agricultural application of nitrogen-fixing cyanobacteria in the past five years (2013-2017) at national and international scales. Moreover, the existing problems and future development directions were discussed. It was hoped that the review provided a summary reference for the development of this field in China. In recent years, there have been new ideas and considerable progresses in the application of nitrogen-fixing cyanobacteria in crop growth regulation, bio-fertilizer production and application, pest control, agricultural pollution treatment and agro-ecological protection. However, there were still problems in this field. Before large-scale application, these problems needed to be solved through further re-search. This included research on algal hormone metabolism and regulation mechanism, metabolic interaction of micro-organisms in biofilm, field evaluation of the degree of crop protection, protection mechanism, pathways and key enzymes of pesticides degradation, field-applied technologies, and effects and mechanism of drought and salt resistance.

Effects of deep tillage and straw return on soil structure of high-yield spring maize field

YU Bo, YU Xiaofang, GAO Julin, HU Shuping, SUN Jiying, WANG Zhigang, GAO Xin, ZHU Wenxin

2018, 26(4): 584-592. doi: 10.13930/j.cnki.cjea.170677

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There are some structural issues of farmland soils in the irrigated Inner Mongolia Plain, such as hard (bulk density of 1.55-1.62 g·cm^-3), shallow plough layer (0-16 cm) and thick plow pan (45 cm). To solve these problems and achieve optimum tillage depth of 22 cm and soil bulk density of 1.1-1.3 g·cm^-3 of the topsoil layer, a test with 1, 2, 3 and 4 years of continuous straw return plus deep tillage was conducted in a high-yield spring maize field in the Science-Technology Demonstration Garden of Inner Mongolia Agricultural University. The full maize straw (20 034. 97 kg·hm^-2) was crushed after autumn harvest and returned to soil combined with 40 cm deep tillage. Four treatments for 1-4 years of straw return plus deep tillage (SF1-SF4) were set and no deep tillage with maize straw return was the control (CK). The soil bulk density, hardness, aggregates and their stability, fertility and pH value were studied. The results showed that:1) in 0-40 cm layer, soil bulk density and hardness significantly decreased under SF1-SF4 treatments compared with CK. 2) In 0-20 cm soil layer, the proportion of aggregates > 0.25 mm (R_0.25), mean weight diameter and geometric mean diameter of SF4 significantly dropped compared with CK. The percentage of aggregate disruption under SF1 significantly decreased by 9.56% compared with CK, the sabotage water-stable aggregates decreased significantly with years of the experiment. The fractal dimension of aggregates of SF4 significantly increased by 7.30% compared to CK. 3) In 20-40 cm layer soil, the R_0.25 of SF1 and SF2 were significantly increased by 13.69% and 17.83%, respectively, compared with CK; the mean weight diameter and geometric mean diameter of aggregates of SF2 were significantly increased by 23.92% and 53.38%. Then percentage of aggregate disruption of soil aggregates significantly decreased by 9.20% (SF1), 3.02% (SF2), 8.38% (SF3) and 3.16% (SF4) compared with CK. Sabotage water-stable aggregates significantly increased by 13.58% (SF1), 16.49% (SF2), 22.67% (SF3) and 25.42% (SF4) compared with CK. Fractal dimension of aggregates of SF2 significantly decreased by 7.39% compared with CK. 4) Soil organic matter content significantly increased by 16.32% (SF1), 24.78% (SF2), 25.07% (SF3) and 25.56% (SF4) compared with CK. Also, available nitrogen, phosphorus and potassium significantly increased compared with CK. Soil pH of SF3 and SF4 significantly decreased respectively by 1.95% and 1.73% compared with CK. In conclusion, the 2-year deep tillage with maize straw return was most suitable for improving the structure of soil plow pan. The 3-year and 4-year deep tillage with maize straw return were suitable for improving the structure of topsoil layer. The application of deep tillage with maize straw return not only improved soil structure of plough layer, but also increased soil organic matter, decreased the percentage of aggregate disruption of soil aggregates and the sabotage water-stable aggregates, and enhanced tillage layer fertility.

Numerical difference in soil water between vertically stratified and homoge-nized soil profiles

XIONG Dinghui, LIU Suxia, MO Xingguo

2018, 26(4): 593-603. doi: 10.13930/j.cnki.cjea.170450

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For many land surface process models, soil moisture is described quantitatively by assuming that its vertical distribution is uniform and that the upper soil texture is representative of the whole soil profile. There are differences in soil moisture between stratified and homogenous soils, which have been little documented so far in research. By setting up three stratified soil groups with different soil hydraulic conductivity combinations and using the upper soils as representative of the soil profiles of the three stratified soil groups, one-dimensional soil water movement model was established to analyze the differences in soil moisture. At the same time, the sensitivities of five parameters (including saturated hydraulic conductivity, saturated water content, residual moisture content, pore size distribution and particle shape) to the differences in leakage and water storage between stratified and homogenous soils were analyzed. It was found that:1) soil water profile simulated by the one-dimensional soil water movement model was consistent with that simulated by Yeh Analytical Solution and also that by Water Transformation Dynamical Processes Experimental Device (WATDPED) experiment. This proved that the model was reliable irrespective of whether root water uptake was considered or not. 2) The greater the difference in saturated hydraulic conductivity between upper and lower soils, the greater the difference in hydrological variables of homogeneous and stratified soils. When saturated hydraulic conductivity of the upper soil was 1.5 times that of the lower soil, the difference in soil mois-ture distribution between stratified and homogeneous soils was less than 0.05 cm³·cm^-3. When it was 3.3 times, the differences in soil moisture, leakage and water storage were 0.15 cm³·cm^-3, 20 cm and 5 cm, respectively. 3) Compared with the lower layer of stratified soil, water holding capacity of the lower layer of homogeneous soil was lower and with water outflow was faster, which resulted in lower moisture distribution, higher leakage and lower storage capacity in lower layer of homogeneous soil. 4) Soil particle shape (n) was the most sensitive parameter to leakage. Then pore size distribution was the most sensitive parameter to water storage, followed by soil particle shape n. In reality, if upper and lower soil saturated hydraulic conductivities differed largely, homogeneous treatment induced significant errors, differing greatly from actual soil moisture distribution in the layers. This heavily affected the accurate estimation of soil moisture, which required a realistic consideration of the use of this practice.

Regionalization of suitable development of unutilized lands in Huanghua City

HE Ling, YAN Huihui, JIA Qijian, ZHANG Li, SONG Zhouying

2018, 26(4): 604-615. doi: 10.13930/j.cnki.cjea.170583

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Abstract:
Unutilized land is an important reserve of land resources, the study on its suitability and development modes is an important measure for sustainable land use. Also unutilized land development is an important action towards food security, economic growth and eco-civilization. It is the focus of scientific and technological innovations of land, and the guidance of development and utilization of unutilized lands to evaluate development suitability and to regionalize rationally the exploitation of unutilized lands. Huanghua City was used as a case study to evaluate the suitability of cultivation, construction and ecological risk of unutilized lands. The indexes systems were established for cultivation suitability evaluation according to land type from aspects of soil property, water resource and vegetation coverage; for construction suitability evaluation from aspects of natural quality, landform and engineering geology; and for ecological risk evaluation from aspects of salinity degree, vegetation coverage, soil thickness and waterlogging degree. The synthetical index method was used to evaluate the suitability of unutilized land for cultivation and construction and ecological risk of exploitation. A coupling model and genetic algorithm were used to evaluate triplet coupling exploitation partitions of unutilized lands. The case study was meant to provide a methodological demonstration of the development and utilization of unutilized lands in the study area and beyond. The results showed that 1) the exploitation suitability for cultivation of unutilized lands had four grades, with the largest unutilized land area belonging to the N grade (not suitable for cultivation) which was in the east of Huanghua City. 2) Construction suitability of unutilized lands had three grades, and the third grade (low suitable) had the biggest area, which concentrated in the center and west of Huanghua City. 3) There were five grades of ecological risk, with high ecological risk regions in the east of Huanghua City and low ecological risk regions in the west of the city. The main region was the middle-to-low and middle-to-high ecological risk grade. 4) The study area was divided into three key exploitation partitions, including exploitation partitions of cultivation lands, construction lands and ecological lands. The exploitation partition of cultivation lands was mainly concentrated in the center and west of the city. The exploitation partition of construction lands was mainly located in the central of Huanghua City. Then the exploitation partition of ecological lands was mainly concentrated in the east of the city. The results could provide scientific support for resolving the dilemma of land supply and demand in the study area.

The deep purification of four aquatic macrophytes for tailrace of rural sewage treatment plants

LIU Haiqin, QIU Yuanyuan, WEN Xuezheng, WANG Yan, ZHANG Yingying, SONG Wei, ZHANG Zhiyong

2018, 26(4): 616-626. doi: 10.13930/j.cnki.cjea.170537

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Abstract:
To provide theoretical basis for optimized application of restoration engineering of aquatic macrophytes in deep purification of tail water of rural sewage treatment plant, a dynamic simulation experiment with running water was conducted, in which the purifying effects of Eichhornia crassipes, Pistia stratiotes, Hydrilla verticillata, and Iris pseudacorus on effluent from sewage treatment works (STW) were compared. Based on the results, plant systems significantly improved water quality of effluent from STW. The purifying effects of E. crassipes and P. stratiotes on nitrogen (N) and phosphorus (P) in STW effluent were better than those of I. pseudacorus and H. verticillata. The average concentration of total nitrogen (TN) in STW effluent was 12.22 mg·L^-1. The average removal efficiency of TN by E. crassipes, P. stratiotes, I. pseudacorus, H. verticillata and control group were 46.25%, 45.74%, 43.41%, 38.39% and 29.22%, respectively. The average concentration of total phosphorus (TP) in STW effluent was 0.38 mg·L^-1. The average removal efficiency of TP by the five experimental treatments were 36.84%, 34.21%, 31.58%, 28.95% and 26.32%, respectively. The average concentration of permanganate index (COD_Mn) in STW effluent was 3.88 mg·L^-1. The average removal rates of COD_Mn in the five experimental treatments were 42.27%, 30.93%, 32.47%, 32.47% and 37.89%, respectively. The net growth rates of E. crassipes, P. stratiotes, H. verticillata, and I. pseudacorus biomass were 550.5%, 418.8%, 210.6% and 80.3%, respectively. The amount of TN absorbed by E. crassipes, P. stratiotes, H. verticillata, I. pseudacorus were 7.36 g, 2.33 g, 5.12 g and 4.46 g, respectively. The amounts of absorption of TP by the four aquatic plants were 0.60 g, 0.19 g, 0.33 g and 0.78 g, respectively. The ability of E. crassipes to assimilate nitrogen was stronger than the other three aquatic plants. Meanwhile, the ability of H. verticillata to assimilate phosphorus was stronger than the other three aquatic macrophytes. The apparent contribution rates of absorption by E. crassipes, P. stratiotes, H. verticillata, I. pseudacorus to nitrogen removal were 15.29%, 4.90% 11.17% and 11.34%, respectively. Meanwhile, the apparent contribution rates of absorption by the four plants to phosphorus removal were 50.34%, 17.17%, 35.24% and 76.34%, respectively. It was feasible and effective to cultivate the floating plant of E. crassipes and submerged plant of H. verticillata in different water layers and combinations in space for deep purification of STW effluent.

Comparison of comprehensive benefits of traditional and hybrid rices -A case study of Hei'er Zhuang Nationality Village in Shizong County, Yunnan Province

GUI Zichang, CHEN Zhen, LI Hongmei, DING Li

2018, 26(4): 627-632. doi: 10.13930/j.cnki.cjea.170731

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Abstract:
Rice cultivation ensures long-term grain supply and food security. Yunan Province of China has the richest rice germplasm resources duo to its diversities of geomorphology, biology, climate and culture, and multi-ethnic groups. However, with rapidly pop-ularizing of hybrid rice in recent years, traditional rice varieties have been faced the risk of extinction (a huge loss of genetic resources) in Yunnan Province. Thus it was urgent and essential to develop conservation and sustainable utilization measures of traditional rice resources, especially in ethnic minority areas. Based on structured interview and questionnaire survey, data on hybrid rice variety 'Yi'xiang-725' and traditional rice variety 'Hei'er Sticky' were collected in Hei'er Zhuang Nationality Village in Shizong County in 2016. Based on production input, economic output, ecological effect and rice culture, the comprehensive benefits of traditional and hybrid rice varieties were compared. The results showed that hybrid rice grain yield was significantly higher than that of traditional rice. However, the comprehensive benefits of traditional rice were significantly higher than those of hybrid rice in the village. The total costs of cultivating one-season hybrid rice and traditional rice were respectively 7 960.35 ¥·hm^-2 and 4 464.90 ¥·hm^-2, the total input of hybrid rice was 1.78 times that of traditional rice. The total output values of traditional and hybrid rice varieties were 52 087.80 ¥·hm^-2 and 40 548.90 ¥·hm^-2, the output value of traditional rice was 1.28 times that of hybrid rice. The net profit and profit rate of traditional rice were respectively 47 622.90 ¥·hm^-2 and 91.42%, which were 32 588.55 ¥·hm^-2 and 80.39% for hybrid rice. The environmental stress and risk of hybrid rice cultivation were higher than those of traditional rice. Biodiversity in traditional rice field was obviously higher than that in hybrid rice field. The traditional rice was closely related with traditional ethnic culture such as food culture, festivals and religious sacrifices in the village. The study suggested that it was critical for sustainable development of rice production to protect and rationally utilize traditional genetic germplasm resources of rice in the region.

2018 Vol. 26, No. 4