中国生态农业学报(中英文)

Progress and perspective in research on plant resistance mediated by root exudates

MAO Mengxue, ZHU Feng

2021, 29(10): 1649-1657. doi: 10.13930/j.cnki.cjea.210328

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Abstract:
Root exudates are a variety of biochemical substances actively or passively secreted by plant roots that play an important role in mediating material exchange, energy transfer and information exchange in plant rhizosphere microenvironments, as well as in plant responses to environmental stresses. Biotic and abiotic stresses can change the composition and quantity of root exudates and increase the content of defensive compounds in plant root exudates. Plants use different root exudates to resist biotic and abiotic stresses, including releasing toxic substances for direct defense, releasing volatile substances to attract natural enemies, interacting with microorganisms to resist biotic stresses, releasing root exudates with osmotic regulation and antioxidant capacity and coordinating hormone signals to resist abiotic stress. Additionally, root exudate flow increases the concentration of many common metabolites, changing the soil physical and chemical properties and microbial activities, and affecting the physiological and biochemical processes at the soil-plant interface, thereby, directly or indirectly improving plant stress resistance. In this paper, the effects of biotic and abiotic stresses on the composition and quantity of plant root exudates were reviewed, the mechanisms of plant defense against biotic and abiotic stresses mediated by root exudates were summarized, and the aspects needed to be further studied were also suggested, to provide a reference for further research on the adaptive mechanism of plants under stress.

Characteristics and environmental effects of nitrogen flows in the crop-livestock system of Jiangsu Province

YU Le, JIAO Yangmei, DING Shang, ZHU Zhiqiang, ZHAO Hongwei

2021, 29(10): 1658-1667. doi: 10.13930/j.cnki.cjea.210172

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With the rapid development of agriculture and animal husbandry, large nitrogen inputs have caused a series of environmental problems. To provide a scientific reference for regional nutrient management, Jiangsu Province, an economically developed region in the Yangtze River Delta, was selected to study the nitrogen flow characteristics in crop-livestock systems from 1998 to 2018 and their environmental effects. The research was based on the NUFER model (NUtrient flows in Food chains, Environment and Resources use, NUFER) and incorporated statistical yearbook data, survey data, and literature data. The nitrogen account balance, nitrogen use efficiency, nitrogen recycling, and loss of the crop-livestock systems in Jiangsu Province were quantitatively analyzed, and the relationships between the economy, resources, and environment of the crop-livestock systems were explored based on a structural equation model. The results showed that from 1998 to 2018, the crop subsystem increased the amount of nitrogen carried by the crop products under the gradual decrease of the total nitrogen imports of the subsystem. Nitrogen carried by the main crops and crop by-products increased from 8.31×10⁵ t to 1.20×10⁶ t. Total nutrient loss also declined. For the livestock-poultry subsystem, nitrogen was mainly introduced via exogenous and local feed; exogenous feed was the main source of nitrogen in the subsystem. The proportion of local feed nitrogen supply increased annually, from 29.32% in 1998 to 44.77% in 2018. From 1998 to 2018, the nitrogen use efficiency of the crop-livestock system increased from 21.39% to 35.00%. The amount of straw to field, local feed, and manure to field increased annually, and the total amount of recycled nitrogen increased from 2.54×10⁵ t to 3.00×10⁵ t. Nitrogen environmental emissions decreased in the past 20 years, and the main sources of loss included soil nitrogen surplus, gas emission loss, water discharge loss, and manure residue. The structural equation model results showed that in the developmental process of the agricultural and animal husbandry systems in Jiangsu Province, economic development and resource reduction promoted improvements in product output and system efficiency. Under the guidance of regional development and policies, crop-livestock systems in Jiangsu Province developed rapidly from 1998 to 2018. The scale of the agricultural and animal husbandry systems had continuously expanded, resource utilization had been relatively efficient, and environmental emissions had gradually decreased. However, there was also a slight imbalance in the development of crop-livestock systems, and there were relatively few combinations of crop-livestock. Future development of the agriculture and animal husbandry systems in Jiangsu Province should focus on coupling the crop and animal husbandry subsystems, moderately expanding the production scale, and balancing the development of agriculture and animal husbandry subsystems to promote local agriculture and animal husbandry.

Spatio-temporal variation in and the driving factors of desert vegetation in Xinjiang

CUI Can, GUO Ying, SHEN Yanjun

2021, 29(10): 1668-1678. doi: 10.13930/j.cnki.cjea.210121

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Desert vegetation is an important part of arid and semi-arid ecosystems in Xinjiang and plays a key role in the maintenance of ecosystem balance. Timely and accurate monitoring of the temporal and spatial distribution of desert vegetation is important for the sustainable utilization of the resources and ecological restoration. Based on remote sensing technology combined with two Normalized Difference Vegetation Index (NDVI) products (AVHRR-NDVI and MOD13A2-NDVI), the area of desert vegetation in Xinjiang from 1989 to 2017 was estimated. The temporal and spatial characteristics of desert vegetation in three typical river basins (Ulungur River Basin, Aksu River Basin, and Yarkand River Basin) were analyzed, and the relationships between desert vegetation and the climate factors, runoff changes, and policy factors were discussed. The NDVI products were used to calculate the vegetation coverage ( f_c), and the distribution and area of desert vegetation were determined according to the threshold of vegetation coverage. Desert vegetation was determined within the f_c threshold range of 0.1–0.35, where 0.1–0.25 indicates low-coverage desert vegetation and 0.25–0.35 indicates high-coverage desert vegetation. The transformation between desert vegetation and other vegetation types was calculated using the land use transfer matrix to explore the evolution and transformation of desert vegetation in Xinjiang from 1989 to 2017. The driving factors of desert vegetation evolution in the three typical river basins were analyzed using correlation analysis. The results showed that the total area of desert vegetation in Xinjiang significantly increased from 1989 to 2017 at a rate of 30 900 hm²∙a⁻¹. The area of low-coverage desert vegetation significantly increased at a rate of 32 200 hm²∙a⁻¹; whereas the area of high-coverage desert vegetation did not vary, with a multi-year average value of 2 087 100 hm². The area of desert vegetation in northern Xinjiang increased slightly, accounting for 67% of the total area of desert vegetation. This was mainly due to an increase in low-coverage desert vegetation. The area of high-coverage desert vegetation in northern Xinjiang slighly decreased. The desert vegetation area in southern Xinjiang significantly increased. During vegetation transformation, 508 500 hm² of desert vegetation transformed from high to low desert vegetation, 3.4124 million hm² of non-desert vegetation types transformed into desert vegetation, and 1.9125 million hm² of desert vegetation transformed into non-desert vegetation types. This study of typical river basins showed that the area of desert vegetation increased with increasing precipitation. Precipitation was the most important factor affecting the evolution of desert vegetation, followed by runoff and policy factors. The influence of air temperature on desert vegetation varied across regions, and the area of desert vegetation near water increased with increasing temperature.

Effect of increased plant density with reduced nitrogen on yield formation and nitrogen use efficiency of hybrid rice under high temperature and high humidity conditions

JIANG Peng, XU Fuxian, ZHANG Lin, ZHOU Xingbing, ZHU Yongchuan, GUO Xiaoyi, LIU Mao, CHEN Lin, ZHANG Rong, XIONG Hong

2021, 29(10): 1679-1691. doi: 10.13930/j.cnki.cjea.210288

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Abstract:
The effects of increased plant density with reduced nitrogen (N) application rate on yield formation and nitrogen use efficiency (NUE) of hybrid rice were studied to provide a theoretical basis for optimum nitrogen fertilizer management and plant density under high temperature with high humidity conditions. Field experiments were conducted in Luzhou City from 2018 to 2019. The high yield and high quality hybrid rice variety ‘Nei6you107’ was grown under six combinations of plant density and N application rate: 1) locally recommended combination with a plant density of 16.5×10⁴ hills∙hm⁻² and a N rate of 180 kg∙hm⁻² (LDN_ck); 2) combination of a plant density of 16.5×10⁴ hills∙hm⁻² and a reduced N rate by 15% (153 kg∙hm⁻², LDN_−15%); 3) combination of a plant density of 16.5×10⁴ hills∙hm⁻² and a reduced N rate by 30% (126 kg∙hm⁻², LDN_−30%); 4) combination of a increased plant density by about 27% (21.0×10⁴ hills hm⁻²) and a reduced N rate by 15% (153 kg∙hm⁻², HDN_−15%); 5) combination of a increased plant density by about 27% (21.0×10⁴ hills∙hm⁻²) and a reduced N rate by 30% (126 kg∙hm⁻² HDN_−30%); and 6) combination of a plant density of 16.5×10⁴ hills∙hm⁻² and zero N rate (LDN₀). The grain yield, yield components, dry matter, N uptake and NUE were measured. The results showed that the grain yield of hybrid rice was significantly affected by different combinations of plant density and N rate (P<0.01). HDN_−15% and HDN_−30% produced higher grain yields than LDN_ck by 4.3%−4.9% and 2.3%−3.6%, respectively. The higher grain yields under HDN_−15% and HDN_−30% were attributed to improvement in spikelets per panicle, grain filling rate, translocation of dry matter accumulated at heading stage (TDM_HD), translocation percentage of dry matter accumulated at heading stage (TPDM_HD), contribution percentage of pre-anthesis dry matter translocation to grain yield (CPDMTG_HD) and harvest index. The LDN_−15% and LDN_−30% had 2.3%−2.5% and 4.8%−5.0% lower grain yield than LDN_ck, respectively. The yield gap between LDN_−15%, LDN_−30% and LDN_ck was attributed to the difference in effective panicles, total dry matter, dry matter accumulation from heading to maturity, and contribution percentage of dry matter accumulation from heading to maturity stage to grain yield (CPDMG_HD-MA). The HDN_−15% and HDN_−30% had lower nitrogen accumulation from heading to maturity and total N uptake than LDN_ck, whereas the translocation of N accumulated at heading stage (NTGN_HD), translocation percentage of N accumulated at heading stage (TPN_HD), contribution percentage of pre-anthesis N accumulation translocation to grain N accumulation (CPNTGN_HD), N use efficiency for biomass production (NUEBP), N use efficiency for grain production (NUEGP) and N harvest index under HDN_−15% and HDN_−30% were higher than those under LDN_ck. Consequently, HDN_−15% and HDN_−30% had lower N requirements to produce 100 kg of grain (NRPG) than LDN_ck by 6.8%−8.4% and 9.0%−9.9%, respectively. HDN_−15% enhanced the agronomic efficiency of applied N (AE_N) by 36.7%−37.4%, partial factor productivity of applied N (PFP_N) by 22.8%−23.5% and recovery efficiency of applied N (RE_N) by 5.6%−12.0% over LDN_ck. The HDN_−30% produced higher AE_N, PFP_N and RE_N than LDN_ck by 55.5%−60.4%, 46.3%−48.2% and 17.0%−20.0%, respectively. The rational combination of plant density and N rate can improve panicle number per unit area, grain filling, TDM_HD, TPDM_HD, NTGN_HD, TPN_HD and harvest index, which further increasing the grain yield and NUE. The optimum combination is plant density of 21.0×10⁴ hills∙hm⁻² plus N rate of 126−153 kg∙hm⁻² in high temperature with high humidity condition.

Effects of fertilizer patterns on the potential nitrogen fixation rate and community structure of asymbiotic diazotroph in highland barley fields on the Tibetan Plateau

MA Ruiping, DAI Xianglin, LIU Guoyi, XIE Yongchun, GAO Xiaoli, GAO Xue

2021, 29(10): 1692-1703. doi: 10.13930/j.cnki.cjea.210148

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Free-living nitrogen fixation (FLNF) by diazotrophs is an important nitrogen (N) source in terrestrial ecosystems and may reprensent a viable solution to environmental pollution caused by N over-fertilization. Studying the impact of different fertilizer regimes in highland barley fields on the diazotrophic community profiles and potential N fixation rates (PNFR) may provide scientific fertilization strategies and a theoretical basis for agricultural green development in the Tibetan Plateau. Here, quantitative PCR, high-throughput sequencing and ¹⁵N labeling methods were used to better understand the impact of different fertilizer regimes on the abundance and composition of diazotrophs as well as the potential N fixation rates in highland barley fields on the Tibetan Plateau. The experiment included five treatments: a control without fertilizer (CK); N, phosphorus (P) and potassium (K) mineral fertilzers (F); manure fertilizer (M); mineral NPK fertilizers plus manure (FM); and mineral NPK fertilizer plus straw (FS). The results showed that: 1) compared with the CK and F treatments, the M, FM and FS treatments significantly (P<0.05) increased the contents of soil organic carbon (C) and total N. Moreover, the ammonium nitrogen (NH₄⁺-N) content was significantly (P<0.05) higher in the FM treatment than in the other treatments. The highest contents of organic C, total N, nitrate N (NO₃⁻-N), available P and available K were observed in the M treatment, and their contents were significantly (P<0.05) higher than those in the other treatments. 2) The PNFR ranged from 2.63 to 4.07 μg∙kg⁻¹∙d⁻¹ under different fertilizer treatments. Fertilization, especially the application of organic fertilizers (sheep manure or straw), reduced the PNFR, and the inhibitory effect of straw on PNFR was higher than that of sheep manure. The soil NH₄⁺-N content was the main factor affecting PNFR. 3) The M and FM treatments significantly (P<0.05) increased diazotrophic abundance, while the opposite was observed for the F and FS treatments. The total N content was the key factor affecting diazotrophic abundance. 4) Different fertilizer patterns significantly changed the diazotrophic composition, and the similarities in the diazotrophic compositions among different fertilizer regimes fell into three major categories: no fertilization (CK), organic fertilization (M), and chemical fertilization (F, FM, FS). Available P was the key factor regulating diazotrophic composition, followed by pH and C/N. In conclusion, the M treatment was the optimal fertilizer practice to improve soil fertility, increase diazotrophic abundance and reduce PNFR decline in highland barley fields on the Tibetan Plateau.

Analysis of mechanical grain harvesting quality and its influential factors of spring maize in Shanxi Province

YAN Xiaoguang, LI Hong, DONG Hongfen, LI Aijun, WANG Guoliang, ZHOU Nan, HU Ying, DU Yanwei

2021, 29(10): 1704-1711. doi: 10.13930/j.cnki.cjea.210151

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The study of mechanical grain harvesting quality and its influential factors is significant for popularizing mechanical maize harvesting technology in Shanxi Province and enhancing the core competitiveness of the maize industry. To study the influence of harvest time on the quality and yield of maize mechanically grain harvested, five maize varieties suitable for mechanical harvest were harvested at six times (Septmber 24th, and October 1st, 8th, 15th, 22th and 29th) by the same harvester and driver. The grain moisture content, broken rate, impurity rate, as well as ear loss rate, grain loss rate, total loss rate and yield of maize were investigated. The results were as follows: first, the grain moisture content declined gradually with a delayed harvest time. With a delayed harvest time, the grain broken rate and loss rate decreased rapidly in the early period but was stable and slightly increased in the later period. Furthermore, with a delayed harvest time, the impurity rate declined gradually and tended to be stable at the end. Finally, with a delayed harvest time, the ear loss rate increased gradually. The average yield when the field was harvested on October 15th was 11.9% higher than that harvested on September 24th. The high grain broken is the main factor limiting the quality of mechanical grain harvesting of spring maize in Shanxi Province. The relationship between grain moisture content and broken rate could be fitted in the model y=0.03x²−1.224x+16.78 (R²=0.802^**). The grain broken rate was the lowest when its moisture content was 20.4%. When the grain moisture content was between 15.6% and 25.2%, its broken rate was less than the national standard of 5%. Choosing the optimal variety for mechanical harvest in the spring maize area of Shanxi Province and harvesting on October 15th could guarantee harvesting quality and yield. ‘Changdan 511’ ‘Dika 159’ and ‘Changdan 716’, which have both perfect mechanical harvest quality and high yield, could be used as mechanical harvest varieties in the spring maize area of Shanxi Province.

Impact of saline irrigation and application of N and P on growth and nutrient distribution of Tamarix chinensis planted in coastal saline-alkali soil

QIU Fagen, YANG Lilin, LIU Min, ZHU Xiangmei, CHEN Shuling

2021, 29(10): 1712-1721. doi: 10.13930/j.cnki.cjea.210209

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Saline irrigation is a highly effective method of elimination of salt and drought stress in spring in the coastal severe saline-alkali soils. Tamarix chinensis, a salt-tolerant plant, plays an important role in reforming the ecological landscape of the coastal wetlands in northern China. However, the responses of plant growing rhythm of T. chinensis to long-term saline irrigation-associated fertilization remain unclear. To promote the rapid growth of T. chinensis for carbon (C) fixation, landscape construction, and saline-alkali soils reclamation, an experiment involving irrigation with local phreatic saline resources and application of nitrogen (N) and phosphorus (P) was conducted to alleviate spring drought and salt stresses, and solve the prominent problems of soil N and P deficiencies in the coastal severe saline-alkali soil. The experiment was consisted of two factors of saline irrigation and N and P fertilization over a four-year period in the coastal saline-alkali soil in the low plain of North China. Six treatments included no fertilizer as control (CK, WCK), only applying N (N, WN), applying both N and P (NP, WNP), each corresponding to no irrigation (the first) and irrigation with local phreatic saline water containing 8.02−9.34 g·L⁻¹ salt (the second), respectively. The results showed that the growth and resprouting of T. chinensis occurred mainly in spring till to summer, but plant height and diameter increase and resprouting did not synchronized simultaneously. The trends of rates of plant height growing, resporuting and stem diameter thickening of T. chinensis during the growth season were as sloping shapes, triangle, and up fast following down slowly, respectively. In the first year of saline irrigation, soil water content, fresh weight of plant and leaf dry weight of T. chinensis was reduced significantly (P<0.01); but the stem dry weight was not impacted. However, after three-year saline water irrigation, the plant height and diameter growth was inhibited, the N content of stem and leaf were decreased significantly (P<0.05), but the P content of leaf increased by 11.8% on average, and branch numbers of T. chinensis increased significantly (P<0.05). The WNP treatment, i.e. saline irrigation and applying NP, retarded the decline of growth rate of plant height and stem diamter during spring to summer (May−June), not only accelerated the resprouting rate, but also increased the N and K contents of leaves, and promoted the transfer of Ca²⁺ and Mg²⁺ from stem to leaves, which resulted in a distribution change of ion in stem and leaf. WNP can alleviated the negative effect of continuous saline irrigation on the growth of T. chinensis by accelerating resprouting, promoting nutrient absorption and ion transport. The results provides a support for rational saline water irrigation and fertilization for T. chinensis in the costal serious saline-alkali soil.

Effects of nano-zero-valent iron (nZVI) on earthworm-bacteria-soil systems

LIU Chang’e, YUE Minhui, TAN Huilin, ZHANG Yue, ZHANG Weilan, XIAO Yanlan, PAN Ying, DUAN Changqun

2021, 29(10): 1722-1732. doi: 10.13930/j.cnki.cjea.210156

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Nano-zero-valent iron (nZVI) is widely used to remedy soil heavy metal pollution. However, the potential effects of nZVI on soil invertebrates, soil quality and microbial communities have not been well studied. In this study, we used Eisenia foetida (0, 10 pieces per kilogram soil) as the test species and examined the potential effects of nZVI (mass ratios of 0, 0.05%, 0.25%, and 0.50%) on the earthworm-bacteria-soil ecosystems after 15, 30, and 45 days of exposure. The results showed that after 45 days of exposure, there was no significant difference in survival rate and biomass of earthworms. The earthworm survival rate and content of malondialdehyde in the 0.50% nZVI system decreased by 27.66% and 0.86 nmol∙g⁻¹, respectively, compared with those on day 15. However, the earthworm biomass increased by 1.20 times, and the catalase activity increased by 2.62 times. At the phylum or genus level, nZVI had no significant effects on the relative abundance, diversity index, and abundance index of soil microorganisms. Compared with the 0 nZVI system, the proportion of soil large aggregates (>250 μm), the average weight diameter of soil aggregates, and the content of available phosphorus (P) in the 0.50% nZVI system increased by 15.69%, 12.59%, and 21.20% under earthworm-mediated conditions, respectively. The proportion of soil macroaggregates and the average weight diameter of soil aggregates in the earthworm and nZVI composite systems were significantly higher than those in the corresponding single nZVI system, and earthworm activity significantly improved the stability of soil aggregates under nZVI stress (P<0.01). In this study, we found that long-term exposure to nZVI had no significant toxic effects on the community characteristics of soil microorganisms but promoted the growth of earthworms, which further improved the bioavailability of soil nutrients. This study provides a scientific basis for environmental safety assessments of nZVI in soil restoration applications.

The development space of and recommendations for ecological farms in China

GAO Shangbin, SONG Chengjun, XU Zhiyu, SUN Renhua, XUE Yinghao, HU Xiaofang, QIAO Yuhui

2021, 29(10): 1733-1741. doi: 10.13930/j.cnki.cjea.210241

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Ecological farms are the main implementation objects for agricultural environmental policy in developed countries. Ecological farms represent the basic unit of promotion for ecological agriculture in China and have become an effective approach for agricultural green development. Based on a 7-year field investigation and 5 years of experience in the construction of eco-agriculture bases, the economic parameters of four regions of China (Northeast China, North China, the Middle and Lower Reaches of the Yangtze River, and South China) and three types of ecological farms (planting farm, breeding farm, plant-breeding combined farm) were obtained. According to the development plan of China’s new type of agricultural business and the proportion of 3%−5% ecological transformation, the development space of ecological farms at the regional and national scales was evaluated, and the industrial value of the ecological farms in promoting agricultural green development was analyzed. The latest requirements and policy recommendations for China’s recent ecological farm construction were put forward at the strategic level. The results show that: 1) the input-output efficiency of ecological farms in South China is the greatest and that in Northeast China is the lowest. With respect to ecological farm type, ecological farms carrying out planting-breeding have the greatest input-output ratio and average profit margin, but breeding-based ecological farms and planting-based ecological farms have lower input-output ratios and average profit margins. 2) There will be 30 000−50 000 ecological farms in China by 2022, and the scale of industrial value for the ecological farms ranks as North China > the Middle and Lower Reaches of the Yangtze River > Northeast China > South China, which will effectively drive market investment and provide employment opportunities. 3) Recently, it is necessary to build several ecological farms as the national demonstrations in the Yangtze River Delta region and other key areas, gradually promote the evaluation of ecological farms throughout the country. Meantime, optimizing the compensation policies, building a big data system, cultivating an industrialization platform, creating the investment and financing mechanism, and cultivating talented workforce and market subjects who would be engaged in the operation and management of ecological farms should be conducted.

Realization path of moderate expansion of management scale of urban leisure agriculture

LI Yufeng, LI Shanwei, XU Pu

2021, 29(10): 1742-1751. doi: 10.13930/j.cnki.cjea.210339

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It is necessary to determine how to appropriately expand the scale of leisure agriculture entities under constraints of existing resources and effectively promote sustainable development of urban leisure agriculture for realization of large-scale operational willingness of urban leisure agriculture entities limited to resources and policy restrictions of metropolises. Based on questionnaire data of 87 leisure agriculture entities in Shanghai, this study constructed a Logistic-ISM (interpretation structure model) model and took the willingness of leisure agriculture entities as measurement targets to study significant factors that affected the willingness, and logical hierarchical relationships between factors. Results showed that moderate expansion depended on the influence of the three levels of factors: 1) Among deep-seated factors, the leisure agriculture entities supported by government construction land were more willing to expand the scale of farmland. 2) Among middle-level indirect factors, the characteristics of agricultural resources, scientific park planning, innovative management capabilities, and business industrial structure positively affected the willingness of leisure agriculture entities to expand the scale of farmland, while the ecological nature of agricultural production was strong, the expansion of operators’ willingness to farmland size was weak. 3) Among the direct factors at the surface level, culturally functional leisure agriculture entities were willing to expand the scale of farmland, while leisure functional management entities tended to reduce the scale of farmland. To promote moderate scale operation of urban leisure agriculture, the government should introduce state-owned enterprises to play a demonstration effect to revitalize stock of rural land resources, and release value of resources. At the same time, leisure agriculture should provide strategic space for urban core functions, fully consider the heterogeneity of leisure agriculture entities, dig deep into rural cultural heritage, and promote transformation from undertaking the function of guaranteeing the supply of agricultural products for multiple functions to highlighting the economic, ecological, and esthetic values of agriculture and rural areas.

Influencing factors of farmers’ willingness to adopt rice-crayfish co-culture and their heterogeneity

HU Naijuan, WANG Yutao, CHEN Qian, ZHU Liqun

2021, 29(10): 1752-1761. doi: 10.13930/j.cnki.cjea.210281

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In recent years, rice-crayfish co-culture has been vigorously promoted as an ecological agricultural mode. As a direct production decision-maker, farmers’ adoption intention and its influence mechanism should be clarified for the scientific promotion and sustainable development of rice-crayfish co-culture. Based on the questionnaire survey and on-the-spot interviews data of 603 farmers in five cities of Jiangsu Province, this study explored the influencing factors and their heterogeneity of farmers’ willingness to adopt the rice-crayfish co-culture mode using the theory of planned behavior and ordered logistic model. Results show that: 1) 56.88% of the farmers in the sample were willing to adopt the rice-crayfish co-culture mode, with income expectation as the key influencing factor. 2) Behavioral attitude, subjective norm, and perceived behavioral control had significant effects on farmers’ willingness to adopt the rice-crayfish co-culture mode. The order of influence was as follows: perceptual behavior control > behavior attitude > subjective norm. 3) Under different qualifications, the factors influencing farmers’ willingness to adopt the rice-crayfish co-culture mode were heterogeneous. Specifically, complete infrastructure and part-time industrialization had a stronger influence on the willingness to adopt this mode of farmers with a high expected income. The farmers who were given subsidies and less affedcted by neighborhood had a stronger willingness to adopt the rice-crayfish co-culture mode. Farmers who were less influenced by the neighborhood had higher requirements for technical training and easeness of learning. The neighborhood effect, guidance of the agricultural technology department, difficulty of technical learning, and level of education had a significant positive effect on the willingness of farmers who participated in the technical training. Distributing subsidies and improving the guidance effect from agricultural technology departments could increase farmers’ willingness to adopt this mode in areas with incomplete infrastructure. Neighborhood effect and part-time employment had a negative impact on the difficulty of technology training, while the income expectation and environmental expectation stimulated farmers to adopt the rice-crayfish co-culture mode. Based on these results, the following policy recommendations were put forward: firstly, the government should strengthen the technical training and guidance effect; second, farmland infrastructure should be improved; third, new agricultural management subjects should be fostered quickly; and finally, differentiated incentive and guidance policies should be formulated according to farmer types.

Measurement, spatial spillover and influencing factors of agricultural carbon emissions efficiency in China

WU Haoyue, HUANG Hanjiao, HE Yu, CHEN Wenkuan

2021, 29(10): 1762-1773. doi: 10.13930/j.cnki.cjea.210204

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The efficiency of agricultural carbon emissions is a bridge between crop production and emission reduction, acting as a critical indicator of the potential for emission mitigation in agricultural production. In previous estimations, the outcomes yield the input-output efficiency of agriculture under the carbon emission constraint, rather than the efficiency of agricultural carbon emission, due to failing to separate the contribution of carbon emissions from other factors. To optimize the existing idea and understand the efficiency more precisely, a theoretical framework and a corresponding equation were developed for analysis in this study. In agricultural production, given the input factors, the efficiency of agricultural carbon emissions under the prerequisite of no desirable output was defined as the ratio of the minimum possible emissions to the actual emissons. On this basis, the GB-US-SBM model was employed to calculate the slack of emissions in 30 Chinese provinces from 2000 to 2019, reflecting the distance between the actual emission and production frontier. Then, the efficiency was estimated based on the slacks and actual emissions. Finally, the influencing factors and spillover effects of agriculural carbon emissions efficiency were explored using the spatial Durbin model. Results showed that: (1) From 2000 to 2019, the average agricultural carbon emissions efficiency was 0.778 in China, indicating considerable potential for emission reduction. At the provincial level, only Inner Mongolia and Qinghai had an efficiency of 1.000, while the rest of the provinces had different spaces for emission mitigation. (2) According to the emissions quantity and efficiency, the 30 provinces were divided into four groups. The five provinces, Henan, Hebei, Shandong, Heilongjiang, and Guangxi, belonged to a group of high emissions with high efficiency. The group of low emissions with high efficiency accounted for the majority, including 12 provinces, such as Inner Mongolia and Gansu. The group with high emissions and low efficiency covered seven provinces, such as Hunan and Hubei. Six provinces, including Zhejiang and Fujian, were classified as low emissions with low efficiency. (3) The global Moran’s index was significantly greater than 0, with a P-value under 0.01, verifying that there was a positive spatial autocorrelation in the provinces. The spatial econometric regression showed that efficiency had a significant positive spatial spillover effect, suggesting that an interactive evolution existed among close provinces. Specifically, four factors—industry structure, investment intensity, financial support for agriculture, and the degree of disaster, harmed the agricultural carbon emissions efficiency directly. By contrast, the irrigation effectiveness and urbanization indicated significant positive effects. In terms of spillover effects, the intensity of a disaster in a province negatively affected the efficiency of agricultural carbon emissions in neighboring provinces, while the urbanization rate exhibited a positive effect. Hence, it was essential to pay attention to the key factors that influence efficiency. Making full use of spillover effects could also help in achieving regional agricultural low-carbon transition. Additionally, local solutions should be addressed, owing to the regional characteristics of efficiency. This study results could provide a theoretical basis for the development of low-carbon agriculture in China.

Regional differences, dynamic evolution, and convergence of the carbon compensation rate of planting industry in China

WU Guoyong, CHEN Ying, SUN Xiaojun

2021, 29(10): 1774-1785. doi: 10.13930/j.cnki.cjea.210225

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Abstract:
Global warming is an increasingly serious problem. Carbon emissions from agriculture had hindered its transition to green agriculture, and carbon emissions from the planting industry cannot be ignored. Reducing the regional differences and clarifying dynamic evolution and convergence of the carbon compensation rates in the planting industry are conducive to the benign development of low-carbon agriculture. At present, few studies consider both agricultural carbon sources and carbon sinks, and an in-depth analysis of the carbon compensation rate of the planting industry is lacking. Existing studies on the agricultural carbon compensation rate focus only on the spatial effect of agricultural carbon but do not effectively analyze the sources and convergence of regional differences in the carbon compensation rate of the planting industry. Therefore, this study considered both the carbon sources and the carbon sinks and estimated the carbon compensation rate of the planting industry in 31 Chinese provinces (municipalities and autonomous districts) from 2002 to 2018. The Dagum Gini coefficient decomposition method was used to measure and decompose the regional differences, the dynamic evolution process of kernel density with non-parametric estimation was investigated, and the σ-convergence, absolute β-convergence, and conditional β-convergence models were used to test the convergence characteristics of the carbon compensation rate. The results were as follows: (1) The overall relative difference in the carbon compensation rate of the planting industry tended to expand. The relative differences in the eastern region expanded, while the relative differences in the central and western regions showed only little change. The relative differences between the eastern and western regions and the eastern and central regions increased, whereas that between the central and western regions decreased. The regional differences were the main reasons for the differences in the carbon compensation rates of the planting industry. (2) The carbon compensation rate of the planting industry in China increased annually, and the number of provinces with high carbon compensation rates increased. The provincial difference in carbon compensation rate first decreased and then increased. The carbon compensation rate in the eastern provinces increased gradually, and the inter-provincial absolute gap decreased, changing from polarization to unipolarization. The carbon compensation rate in the central provinces increased gradually, and the absolute gap decreased. The carbon compensation rate in the western provinces was relatively stable and showed little change. (3) There was no σ-convergence in the carbon compensation rate of the planting industry in the whole country and the eastern and western regions, but it was not obviously observed in the central region. The absolute and conditional β-convergences were significant in the whole country and the eastern, central, and western regions. The results of this study emphasize that regional heterogeneity in the carbon compensation rate of China’s planting industry is prominent and that the temporal trend of carbon compensation rate is generally increasing. The “catch-up effect” among provinces and the convergence trend of the carbon compensation rate growth among regions are apparent. In the future, it will be important to improve the carbon compensation rate of the planting industry to better formulate a green development strategy for regional agriculture and actively reduce regional emissions.

Temporal and spatial characteristics of China’s provincial green total factor productivity of grains from the ecological value perspective

ZHOU Yingheng, YANG Zongzhi

2021, 29(10): 1786-1799. doi: 10.13930/j.cnki.cjea.210106

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Abstract:
Green development is important for China’s future food safety, and measuring green productivity is an effective method to explore ways to increase green grains production. Based on the differences in the endowment of cultivated land resources in different regions, this study adopted the ecological services value evaluation method to measure the ecological value of cultivated land during the process of grain production. To incorporate the nutrient pollution and non-nutrient pollution generated in the process of grain production, the global Malmquise Luenberger index and the super efficiency model were used from the static and dynamic perspectives, to calculate China’s total factor productivity and input-output redundancy rate from 1997 to 2019. To better understand the temporal and spatial changes in China’s green total factor productivity, the spatial development characteristics of the agricultural production factors were investigated in the selected six years (1997, 2001, 2005, 2009, 2013 and 2019) using the equidistant distribution method, and Moran’s I index was used to study the spatial heterogeneity and agglomeration of green total factor productivity of grains in China. The results showed that: 1) During the study period, the ecological value of grain production reduced by 0.39%, from 647.157 billion Yuan in 1997 to 644.616 billion Yuan in 2019; a loss of 2.541 billion Yuan. The ecological value in the northeast, central, and southwest regions increased, whereas that in the east and northwest regions decreased. 2) Analysis of the environmental impact of grain production showed that the traditional total factor productivity, which does not consider environmental effects, tended to ignore the positive and negative aspects of grain production and cannot accurately assess the true efficiency of China’s grain production. After accounting for environmental factors, such as the ecological value of grain production and agricultural non-point source pollution, this study found that the green total factor productivity of grains increased by 0.60% annually, from 0.9754 in 1997 to 1.0990 in 2019, driven mainly by technological progress (1.0308). The driving effect of technical efficiency (0.9973) was weak. 3) The proportion of provinces (cities) that were relatively effective in the green total factor productivity of grains increased from 9.68% in 1997 to 67.74% in 2019. In terms of time and space, the relatively effective provinces (cities) was mainly in the eastern region and then graduallydeveloped to the northeast, central, and northwest regions. 4) Due to high pollution emissions and resource consumption, the main reasons for the provinces (cities) that were relatively ineffective in green total factor productivity of grains were the redundancy of employees in the primary industry, the use of agricultural film, and carbon emissions. 5) The green total factor productivity of grains in China had a significant positive spatial correlation dominated by high-high agglomeration, and the green total factor productivity of grains showed spatial characteristics of agglomeration in the central and southwestern high-efficiency areas. The degree of agglomeration was increasing. Based on the above results, this study advocates for a better understanding of the positive and negative effects of grain production activities, strict control of the non-grain and non-agricultural phenomenon of agricultural land, and the promotion of advanced agricultural technologies to promote the green total factor productivity of grains.

Spatio-temporal changes of water resources ecosystem services in the Hanjiang River Basin based on the shared socioeconomic pathway

CHEN Zeyi, YU Peiheng, CHEN Yiyun, JIANG Song, BAI Shaoyun, GU Shixiang

2021, 29(10): 1800-1814. doi: 10.13930/j.cnki.cjea.210160

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Abstract:
A comprehensive assessment framework for watershed ecosystem services and trade-offs was proposed for watershed governance and regional sustainable development in this paper. The framework integrated both shared socioeconomic pathways (SSPs) and future land use simulation (FLUS) models. The socioeconomic data of China’s provincial SSPs considering domestic development and regional differences were introduced to the FLUS model, meeting the needs of regional level land-use simulation scenarios and fully considering the interaction between human socio-economic activities and the natural environment. Taking the Hanjiang River Basin as an example, the FLUS models under different SSPs scenarios were built to evaluate the ecological and environmental effects on land-use change. We further investigated the response of water conservation and water quality purification services to social development decision-making and spatiotemporal evolution by using InVEST model. Results showed that: 1) the water production depth in 2035 under all the SSP scenarios was significantly higher than that in 2015. The increment under the SSP1 and SSP2 scenarios was relatively small, and the increment under the SSP3 scenario was relatively higher with the most intense change. The areas with increased water production depth were mainly concentrated in the southeast, central, and western regions of the Hanjiang River Basin. 2) From 2015 to 2035, due to frequent human activities and rapid urban expansion, in areas where the water production depth increased, urbanized land also increased significantly. According to the land-use simulation and water production depth change results, urbanized land had a strong water production capacity due to low vegetation coverage, weak evapotranspiration, and low permeability of hardened ground. 3) The nitrogen and phosphorus loads in the SSPs scenarios in 2035 were lower than those in 2015. The reduction under the SSP1 and SSP5 scenarios was relatively large, and the SSP3 scenario was the same as that in 2015, but the change was the most intense. The areas with increased nitrogen and phosphorus loads were mainly concentrated in the southeast and western regions. 4) According to the results of land-use simulation and nitrogen and phosphorus load change, the urbanized land had more pollutants due to the frequent human socio-economic activities, while the cropland was due to the use of chemical fertilizers and pesticides in the process of agricultural production, making part of the nitrogen and phosphorus elements not absorbed by crops. The two types of land-use caused serious pollution in the water environment of the basin. The future development planning of the Hanjiang River Basin can be based on the SSP1 scenario, referring to the economic and technological development model under the SSP5 scenario, combined with the basin functional district, optimizing the land-use structure, and ensuring the water ecological environment security of the basin while paying attention to economic development. The results of this study can be used to prepare territorial spatial planning and sustainable water resource asset management in the Hanjiang River Basin, support the construction of the Hanjiang River eco-economic belt, and promote the improvement of the water ecological environment in the Yangtze River Basin.

2021 Vol. 29, No. 10