中国生态农业学报(中英文)

Theoretical framework and realization pathway of agricultural green development

MA Wenqi, MA Lin, ZHANG Jianjie, ZHANG Fusuo

2020, 28(8): 1103-1112. doi: 10.13930/j.cnki.cjea.200238

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Abstract:
Agricultural green development, as a novel concept, technical pattern and systematic procedure, is the new direction of China's agricultural development, but many theoretical and scientific questions about agricultural green development remain unsolved. In this study, we described the theoretical framework and the realization route of agricultural green development in China. Compared with sustainable agricultural development overseas, China's agricultural green development is considered to focus more on the synergy of "green" and "development", and emphasis the characterized as "green" led by "development" and "development" promoted by "green", which in turn poses difficult challenges for China's agricultural green development. Ten key points of agricultural green development are proposed in this paper, namely: focusing on food systems; persisting in the two themes, i.e., green and development; reinforcing the three pillars, i.e., society, economy and ecological environment; focusing on the four interfaces, i.e., resources, production, consumption and environment; coordinating the relationships among five stakeholders, i.e., government, farmers, companies, retailers and consumers; following the eight principles, which are input control, resource cycling for improving efficiency, potential realization through integrated management, emission reduction, integration for value appreciation, diet optimization for environmental pressure alleviation, policy mechanism guarantee, and local implementation; respecting the rules of four processes, including materials, energy, information and value flows; innovating the regulatory measures in seven sections of green development, i.e., policy, capital, services, technology, products, knowledge and engineering; taking the three paths of transforming towards, which are the ecological environmental control mechanisms based on green development checkpoints, the implementation of the whole industrial chain green policy and technology, the optimization and regulation of food supply and demand; and realizing these paths through the nine approaches. Eventually, the coordination of the six agriculture-related goals in the social, economic, productivity, ecological, environmental, and resource sectors will be achieved. We propose to enhance key researches on agricultural green development theory, technology, and strategy. We also propose to implement the "five-one" agricultural green development technical engineering projects that promote China's agricultural green development as early as possible, namely, "one basic database, one batch of technical equipment, one set of science and technology platforms, one batch of demonstration projects and one series of think tank achievements".

Construction of a green development index system for agriculture in China and examples

ZHANG Jianjie, CUI Shilei, MA Lin, MENG Fanlei, SONG Chenyang, LI Yumeng, MA Wenqi

2020, 28(8): 1113-1126. doi: 10.13930/j.cnki.cjea.200069

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Abstract:
Quantitative indicators are crucial for analyzing agricultural green development (AGD). Accordingly, the present study aimed to develop a system of indicators to serve for goals of AGD in China based on agriculture and the whole food production-processing-consumption chain. The indicator system included five aspects (society, economy, productivity, resources, and environment) and a total of 53 indicators (27 direct, 14 indirect, and 12 optional). The indicators enabled quantitative analyses of AGD at different scales. Social and economic indicators were calculated using collect statistical data and literature; and then, production, resource, and environmental indicators were calculated using the NUFER (nutrient flows in food chains, environmental, and resources use) model. Criteria for indicator selection, calculation process, and grading standards were also established. Based on the index system, a "top-down" research approach was adopted, and the spatial and temporal characteristics of AGD indicators were quantitatively analyzed at different scales. At the national scale, nitrogen flow in China was quantitatively analyzed, and the overall characteristics, problems, and future optimization strategies for AGD in China were described. From 1980 to 2017, the N use intensity, N production ability, crop protein yield and animal protein yield increased; while the N use efficiency of crop production first decreased and then increased, livestock manure use efficiency decreased and environmental emission cost of resources increased sharply in China. The main reasons for these changes were irrational use of N in crop-livestock production systems, changes in crop and livestock structure, separation of crop production and livestock husbandry, and uneven development of economy and society. At the provincial scale, the characteristics of AGD in the tropical islands of Hainan Province were analyzed. The intensive use of pesticides and N fertilizer was the main limitation of AGD in Hainan. The main impact factors were the high proportion of tropical fruits and vegetables and high density of livestock and poultry breeding At the county scale, both the current status of agricultural development and the resource and environmental costs of Hebei Province were analyzed. High inputs of agricultural chemicals were the main limiting factor for AGD in Hebei. Besides, the disconnection between crop and livestock production was the main limiting factor of AGD. Through benching marking, the spatiotemporal characteristics of green development indicators in the whole dairy industry chain in China was discussed to distinguish the development gap, bottleneck problems and limiting factors. This empirical research indicated that the AGD index system and the NUFER model were useful for quantitatively analyzing the characteristics and costs of AGD at different scales in China.

Systematic research and quantitative approach for assessing agricultural green development

JIN Xinpeng, MA Lin, ZHANG Jianjie, MA Wenqi, ZHANG Fusuo

2020, 28(8): 1127-1140. doi: 10.13930/j.cnki.cjea.200241

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Abstract:
Research on agricultural green development (AGD) is a scientific direction of integrating multi-disciplinary knowledge. It takes the food system as the research boundary, and focuses on analyzing the relationship between different sectors in the food system to achieve the targets of food security, human health, resource conservation and environmental protection. It also devotes attention to the coordination of "green" and "development" in agriculture production system. Previous methods often neglect systematically thinking and quantitatively analyzing of the AGD, and cannot coordinate multiple objectives of AGD. In this study, we firstly defined the research boundary of AGD, which considered "soil-crop production-animal production-food processing-household consumption-environmental impacts" systems; secondly, we developed the quantitative research approaches of "top-down" and "bottom-up", combining the whole food chain and multi-scale characters in AGD studies; thirdly, we developed the new modelling system for AGD (NUFER-AGD), including a core model (the food system nutrient flow model, NUFER), three quantitative analysis modules (water, atmosphere and land use modules) and one index module (linked to Driving force-Pressure-States-Impacts-Response, DPSIR; Sustainable Development Goals, SDGs; and Planet Boundaries, PBs); and last, we reviewed several case studies of quantitative research on AGD. Here, case studies were conducted by following 3 steps: (1) coordinating the overall goals AGDs at national level by nexus analysis approach and multiple indicators evaluation; (2) designing AGDs solutions quantitively by using green environment and resource limits as thresholds at the watershed scale; (3) analyzing the technical pathways of AGD systemically in the whole industrial chain. This research can not only provide systematic thinking and quantitative methods for the research of AGD, but also provide scientific support for the national strategy of AGD in China.

Spatiotemporal variation of nitrogen indicators related to agricultural green development in China

CUI Shilei, ZHANG Jianjie, TONG Bingxin, MA Lin, MA Wenqi

2020, 28(8): 1141-1155. doi: 10.13930/j.cnki.cjea.200159

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Abstract:
Nitrogen is an important indicator of green development of agriculture, which is related to resources, environment, food security and human health in agricultural and food production systems. In this study, the model of NUtrient Flows in food chains, Environmental and Resources use (NUFER) was used to quantify 18 nitrogen indicators related to agricultural green development in China based on collected statistics and data from the scientific literature. Based on the potential values and thresholds reported in the literature, the levels of agricultural green development of each indicator were divided, from high to low, into levels Ⅰ, Ⅱ, Ⅲ and Ⅳ. These were used to evaluate and analyze the variations in the spatiotemporal characteristics of the nitrogen indicators, and to identify the factors influencing the relevant nitrogen indicators, which allowed us to suggest improvements for agricultural green development. From 1980-2017, the nitrogen use intensity indicators, environmental emission indicators and most of the efficiency use indicators decreased from level Ⅰ to level Ⅳ. The straw recycling efficiency indicator, most of the nitrogen production indicators and the food consumption indicators increased over time from level Ⅳ to Ⅰ. From the spatial distribution perspective, nitrogen input and environmental losses increased in the north, east, central, and south regions of China. The diet consumption level increased in all regions and was more pronounced in the eastern regions. Compared with 1980, the unit animal protein production and unit area plant protein production levels in the east and north of China were higher in 2017, but still at level Ⅲ. The levels of the efficiency indicators of agricultural green development in all regions of China were low, and most regions were still at level Ⅲ and Ⅳ in 2017. Compared to 1980, the nationwide proportion of nitrogen indicators at levels Ⅳ and Ⅲ were relatively stable in 2017, and the proportion of indicators at level Ⅰ decreased from 27.1% to 8.3%. From 1980 to 2017, the levels of agricultural green development across the whole China decreased. Among the seven major regions, the proportion of level Ⅰ in each region decreased (with most areas below 30.0%), while the proportion of levels Ⅲ and Ⅱ significantly increased. In terms of indicator types, the proportion of nitrogen production and food consumption indicators at level Ⅳ decreased in 2017 compared with 1980, and the sum of the proportion of nitrogen environmental emissions and efficiency indicators at levels Ⅰ and Ⅱ also decreased. The reasons for these trends include the irrational use of nitrogen resources in crop-livestock systems, changes in planting and breeding structures, inadequate integration of agriculture and livestock husbandry, and uneven development of the economy and society. Therefore, based on the characteristics of the spatiotemporal changes of these different types of indicators, it is necessary to optimize the use of nitrogen to improve the nitrogen indicators by means of soil fertilization, changing the cultivation structure, applying nitrogen emission reduction technologies and policies, and promoting agricultural green development in China.

Spatial and temporal characteristics of agricultural green development indica-tors in Hainan Island

SONG Chenyang, ZHANG Jianjie, LIU Ling, MA Wenqi, MA Lin, DING Shang, ZHAO Hongwei

2020, 28(8): 1156-1167. doi: 10.13930/j.cnki.cjea.200011

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Abstract:
Since the establishment of Hainan Province, the scale, structure, and methods of agricultural production have undergone significant changes, which are critical with respect to the progress of agricultural green development (AGD). In this study we adopted China's AGD indicator system with 20 indicators, and using the NUFER (NUtrient flows in Food chains, Environment and Resources use) model, we quantitatively calculated the spatial and temporal changes in Hainan Island AGD indicators from 1988 to 2017. Moreover, we discussed the factors restricting AGD in Hainan Island. The results revealed that the overall level of Hainan Island's AGD had shown a declining trend over the past 30 years. The numbers of indicators at lower levels (Ⅲ and Ⅳ) had increased from 12 to 15, whereas those at higher levels (Ⅰ and Ⅱ) had decreased from 8 to 5. With increase in the proportion of economic crops such as vegetables and fruits, the scale of livestock and poultry farming and the degree of intensification, Hainan's agricultural output value and social development level had continued to increase. Furthermore, the agricultural output value per unit cultivated land area and level of agricultural mechanization had increased from 6 200 ￥·hm^-2 and 3 kW·hm^-2 to 161 000 ￥·hm^-2 and 13 kW·hm^-2, respectively. Over the past 30 years, there had been an increasingly excessive input of agricultural resources (nitrogen, phosphorus, pesticides, and agricultural film), among which, the intensities of pesticide and agricultural film usage had shown the highest increases, rising from 8.0 kg·hm^-2 and 0 kg·hm^-2 to 41.9 kg·hm^-2 and 34.7 kg·hm^-2, respectively. As a consequence of the low productivity levels, the environmental emissions of applied nutrients (e.g., nitrogen surplus in farmland, nitrogen runoff in farmland, and NH₃ volatilization from agricultural system) had increased significantly, with NH₃ volatilization and nitrogen surplus per unit sown area showing the largest increases, rising from 61.0 kg·hm^-2 and 152.1 kg·hm^-2 to 131.4 kg·hm^-2 and 297.9 kg·hm^-2, respectively. Environmental pollution caused by an excessive input of agricultural resources and the separation of agriculture and animal husbandry had been the main factors contributing to the restriction of AGD in Hainan Island. Given that the central part of the island is covered in montane forest and has been designated as a national key ecological function protection area, the scale of development in this region had been relatively limited. Consequently, the coastal plains had experience more rapid growth in resource input. Although this had a detrimental impact on the environment, the economy growth, social development, and agricultural productivity indicators for these areas had improved to a greater extent than those for mountain forest area. In the future, Hainan Island should rationally optimize the planting structure in coastal areas, improve the level of production management, and strengthen the combination of agriculture and animal husbandry to reduce resource losses and achieve the island's requisite AGD goals.

Temporal and spatial characteristics of agricultural green development indica-tors in counties of Hebei Province

LI Yumeng, ZHANG Jianjie, CUI Shilei, MA Lin, MA Wenqi, WEI Jing

2020, 28(8): 1168-1180. doi: 10.13930/j.cnki.cjea.200483

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Abstract:
In order to analyze the main problems and limiting factors of agricultural green development at county level in Hebei Province, this study took 135 counties (districts) in Hebei Province as the research objects, focusing on five dimensions (society, economy, productivity, resources and ecological environment), selected 26 agricultural green development indicators based on expert opinions and statistical data to analyze the spatio-temporal change characteristics of agricultural green development indicators at county scale in Hebei Province in 1996 and 2016. According to the degree of agricultural green development from high to low, the selected indicators were divided into Ⅰ, Ⅱ, Ⅲ and Ⅳ grades. The results showed that the agricultural production condition in Hebei Province had been improved continuously from 1996 to 2016. The agricultural mechanization level and farmland irrigation level had increased at different degrees. The agricultural economic benefits also improved greatly, in which agricultural output value per unit cultivated land area and rural disposable income per capita increased by 1.96 times and 3.05 times, respectively. The agricultural production capacity continued to increase, as demonstrated by the continuous increases in caloric and protein production per unit cultivated land area and utilization efficiency of nitrogen. The input of resources increased resulting from the use intensity of nitrogen, phosphorus, pesticide and agricultural film increased continuously; and the environmental risk remained at a high level. In terms of spatial variation, the degree of agricultural green development of social development, economy and agricultural production in the northeast and south of Hebei Province showed an increasing trend, while that of resources and eco-environmental indicators showed a decreasing trend. The results showed the characteristics of high degree of agricultural green development in the northwest and southeast of the province. The number of counties with the grade Ⅰ green development of five indexes was relatively high, showing a significant spatial difference. The main bottleneck of agricultural green development in Hebei Province came from resource shortage, environmental pollution and ecological destruction; which caused by the excessive investment of resources, the change of planting and breeding structure and the separation of agriculture and animal husbandry. It is necessary for the agricultural green development in Hebei Province to improve the efficiency of resource utilization, keep the environment clean and the ecosystem stable.

Spatiotemporal characteristics of green development indicators in the whole dairy industry chain in China

GAO Wei, ZHANG Jianjie, ZHANG Yanfang, ZHANG Nannan, WANG Xuan, BAI Zhaohai, MA Wenqi, MA Lin

2020, 28(8): 1181-1199. doi: 10.13930/j.cnki.cjea.200471

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Abstract:
Dairy industry is a key agricultural industry related to public health and food safety. According to the agricultural green development index system in China, 28 indicators were selected from five aspects (i.e. social development, economic benefits, agricultural productivity, resource utilization and ecological environment) in this study to establish the green development indicators and benchmarks of the whole dairy industry chain in China. Based on the index system, this study quantitatively analyzed spatiotemporal variations of green development indicators of the whole dairy industry chain in China during 1990-2017 using NUFER-animal model. The results showed that 1) milchigs consumption per capita in China increased from 2.0 to 12.5 kg·cap.^-1·a^-1 during 1990-2017, 2) milk yield per cow increased from 2.4 to 7.0 t·head^-1·a^-1, 3) nitrogen use efficiency of crop-livestock farming system increased from 8.4% to 14.4%, 4) blue water footprint of milk decreased from 0.5 to 0.2 m³·kg^-1, 5) land use per unit milk product decreased from 18.5 to 3.3 m²·kg^-1, and 6) NH₃ volatilization from farming system reduced from 21.9 g(N)·kg^-1 to 7.0 g(N)·kg^-1. Resource utilization and environmental costs per unit of milk showed a downward trend, while they were higher than that of Europe and America. Moreover, production and processing costs of milk increased in China with lower profits than that of developed countries (e.g. Europe and America). The green development level of production, resource utilization and ecological environment were relatively high in the eastern China and the transition zone between cropping area and nomadic area. Production and consumption of milk in the northern China were higher. It is an effective way to promote the revitalization and green development of China's dairy industry by 1) implementing the green technologies and integrating production systems of crop and animal production; 2) building the benefit sharing mechanism of production, processing and marketing industrial chain; and 3) reestablishing the milk quality tracking system of the whole industry chain and the trust mechanism of publics.

Effects of modified urea ammonium nitrate solution topdressing on ammonia volatilization and leaching

XIAO Qiang, LI Hongyan, YI Wenping, ZOU Guoyuan, LI Lixia, SUN Shiyou

2020, 28(8): 1200-1209. doi: 10.13930/j.cnki.cjea.190811

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Abstract:
In this study, with urea ammonium nitrate solution as raw material, NBPT (n-butyl thiophosphoric triamide) and DMPP (3, 4-dimethylpyrazole phosphate) were used as inhibitors, and polyurethane as a protective agent to develop two modified urea ammonium nitrate solutions (YUL1 and YUL2). And their effects on ammonia volatilization and leaching loss in summer maize in the North China Plain were studied. In the field experiment, six treatments were set up: 1) no urea application (CK), 2) farmers' traditional urea application (CN), 3) optimized urea application (CNU), 4) application of optimized urea ammonium nitrate solution (UAN), 5) and 6) optimized modified urea ammonium nitrate solution 1 (YUL1) and 2 (YUL2) application. The effects of nitrogen regulation characteristics were systematically evaluated. The properties of the products were analyzed by scanning electron microscope (SEM) and energy disperse spectroscopy (EDS). The in-situ continuous dynamic observation of ammonia volatilization and nitrogen transformation was carried out within 15 days after nitrogen application (which occurred at bell mouth stage of summer maize); the yield and economic benefits were measured and calculated at the maturity stage of maize. The results showed that the modified urea ammonium nitrate solution was clear and free of impurities, the film surface was smooth and dense after casting, and the inhibitors were evenly distributed on the film surface. The content of phosphorus and sulfur on the film surface was increased by energy spectrum test, which proved that the composite inhibitors and urea ammonium nitrate solution achieved effective fusion. Under the same optimized nitrogen application rate, compared with CNU, the total amount of ammonia volatilization of YUL1 decreased significantly by 19.3% and YUL2 increased by 9.6%. Compared with UAN, YUL1 and YUL2 decreased the total amount of ammonia volatilization significantly by 57.3% and 42.0%, respectively. Compared with other nitrogen application treatments, the soil layer of 0-20 cm in the middle and late period of summer maize growth of YUL1 and YUL2 treatments still maintained relatively higher nitrogen contents. After harvest, the soil nitrate nitrogen contents of YUL1 and YUL2 were 46.0% and 43.4%, respectively, higher than that of CNU, and 45.6% and 44.7% higher than that of UAN in the 0-20 cm soil layer; in the soil layer of 180-200 cm, they were significantly lower than those of other treatments. With regard to ensuring the yield and net income of summer maize, the modified urea ammonium nitrate solution significantly reduced ammonia volatilization and leaching loss of nitrogen.

Responses of dry matter accumulation and yield in a following maize crop to spring wheat straw returning

YIN Wen, CHEN Guiping, GUO Yao, FAN Zhilong, HU Falong, FAN Hong, YU Aizhong, ZHAO Cai, CHAI Qiang

2020, 28(8): 1210-1218. doi: 10.13930/j.cnki.cjea.200164

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Dry matter accumulation is the highest form of photosynthetic products in crops, and its accumulation dynamic characteristics are closely related to grain yield. Therefore, it is important to identify the effects of different straw retention methods on dry matter accumulation and crop yield with plastic film mulching. In this study, a field experiment was carried out in a typical irrigated inland region with an arid climate, to determine the characteristics of the above-ground dry matter accumulation and the yield of maize under different retention methods of straws of the preceding spring wheat. The treatments were: no-tillage with long spring wheat straw mulched in the field (NTM), no-tillage with spring wheat straw standing in the field (NTS), conventional tillage with long spring wheat straw incorporated into the soil (CTS), and conventional tillage without straw retention (CT). The results showed that the NTM and NTS treatments increased the maximum and the mean dry matter accumulation rate and delayed the emergence time of the maximum dry matter accumulation rate of maize. The NTM treatment had the most obvious effect. Compared to CT, the NTM treatment significantly increased the maximum and mean dry matter accumulation rate of maize by 5.7% and 11.2%, respectively. The emergence time of the maximum dry matter accumulation rate underh NTM was delayed by 3.4 days (P < 0.05). The NTM and NTS treatments maintained a high dry matter accumulation rate, effectively delaying the decline of dry matter accumulation rate for maize from the silking to filling stage. This prolonged the duration of dry matter accumulation and increased the amount of dry matter accumulation at the maturing stage. Compared to CT, NTM and NTS treatments significantly increased the dry matter accumulation of maize at the harvest stage by 11.3% and 9.9% (P < 0.05), respectively. The grain yield of maize was 15.6%, 13.0%, and 7.8% higher in NTM, NTS, and CTS treatments than in CT treatment (P < 0.05). The most significant effect on improved yield was from NTM treatment, which was 7.3% higher than that of CTS (P < 0.05). The main reason for the increased yield was the combined increase in spike numbers, grain numbers per spike, and 1000-grain weight. Correlation matrix analysis showed that the population size of following maize could be regulated by optimizing the previous spring wheat straw returning methods, which affected the growth and yield characteristics. Our results showed that the NTM (no-tillage with spring wheat straw mulch) is the most appropriate cultivation method to optimize dry matter accumulation and obtain high yields of maize in an arid inland irrigation region.

Response of soil organic carbon fractions to exogenous carbon input in mine reclamation

ZHANG Yunlong, GAO Chunhua, LIU Liang, JIN Dongsheng, LU Jinjing, LI Jianhua

2020, 28(8): 1219-1229. doi: 10.13930/j.cnki.cjea.190925

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Studying the effects of exogenous carbon input on soil organic carbon fractions is important for understanding changes in soil organic carbon and fertilization management in the reclamation of mining areas. Based on a long-term experiment in a coal mining subsidence reclamation area in Xiangyuan County, Shanxi Province, China, this paper explored the response characteristics of the carbon fractions of reclaimed soil to the input of different exogenous carbon sources (biochar, compost, biogas residue, cow manure, and straw). Reclamation soil samples (0-20 cm) were collected in 2011 and 2016. The organic carbon, easily oxidized organic carbon, and labile carbon pool Ⅰ/Ⅱ in soil were measured. The results showed that the growth rate and the annual change of soil organic carbon with the biochar treatment increased by 101.80% and 0.56 g·kg^-1·a^-1, respectively, compared with the no-addition control (CK), and the increases with biochar were significantly higher than those with other organic material treatments. Compared with CK, the amounts of carbon sequestration in the biochar and cow manure treatments increased by 100.52% and 91.52% in the 0-20 cm soil layer, respectively; and the amounts of carbon sequestration in the biochar and cow manure treatments were significantly higher than those of other organic material treatments. There were no significant differences among composting, biogas residue, and straw treatments in promoting soil carbon sequestration. The addition of organic materials significantly increased the growth rate and annual change of easily oxidized organic carbon in reclaimed soil; the highest value was observed in the compost treatment, with an increase of 12.37% and 0.16 g·kg^-1·a^-1, respectively, compared with CK. The addition of cow dung significantly increased the growth rate and annual change of the labile carbon pool Ⅰ/Ⅱ, with a greater effect than other organic materials in reclaimed soil. The addition of organic materials also improved the stable organic carbon content of the soil. Compared with CK, the biochar and cow manure treatments showed the greatest improvement in the stable organic carbon content, with a significantly higher contribution than those of other organic material treatments. However, there was no significant difference between cow manure and biochar treatments. The carbon management index of biochar treatment was 36.30%, 52.23%, 41.50%, and 52.02% higher than that of composting, biogas residue, cow manure, and straw treatments, respectively. The application of all the exogenous carbon sources significantly improved the content of carbon fractions and the carbon management index of reclaimed soil. The application of biochar had the best effect. This indicates that biochar can be used as an effective management measure to improve the soil organic carbon of reclaimed mining areas.

Changes in planting structure and nitrogen and phosphorus loss loads of farmland in Taihu Lake region

MIN Ju, JI Rongting, WANG Xia, CHEN Kewei, XU Jiantao, PAN Yunfeng, LU Zhixin, LU Guang, WANG Yuan, SHI Weiming

2020, 28(8): 1230-1238. doi: 10.13930/j.cnki.cjea.200152

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The Taihu Lake region is the most developed agricultural region in China. In recent years, driven by economic interests, the transformation of rice paddy into orchard, vegetable field and tea garden in Taihu Lake region has become prominent. The changes in the trend and distribution characteristics of planting structure, as well as the N and P fertilizer inputs and runoff loads (before and after the change in planting structure) are still not studied. Based on the Agricultural Statistical Yearbook and survey data of literatures, through the analysis on planting areas of rice paddy, orchard, vegetable field, and tea garden in major cities in Taihu region (Changzhou, Wuxi, Suzhou, and Huzhou) from 2002 to 2017, nutrient input and N and P loads in farmland were studied to provide scientific basis for prevention and treatment of agricultural non-point source pollution in the area. The main results were summarized as follows: from 2002 to 2017, the planting areas of orchard, vegetable field, and tea garden significantly increased; especially for orchard (increased by 2.852×10⁴ hm²) and tea garden (increased by 1.892×10⁴ hm²). However, the area of rice paddy was decreased by 1.985×10⁵ hm²; the change in rate of planting structure from 2002 to 2010 was much higher than that of 2010 to 2017. The increased planting areas of orchard, vegetable field, and tea garden were mainly concentrated in the lakeside districts, such as Wujin, Nanxun, Yixing, Suzhou urban area, and Changxing. The total N and P fertilizer inputs were decreased by 25.26% and 9.59%, respectively, from 2002 to 2017. The risk of total N runoff reduced significantly by 34.66%, while the total P loss amount remained stable (overall decline by 1.84%). In 2017, the estimated N loss loads from the sources of rice paddy, orchard, vegetable field, and tea garden were 10 200 t, 670 t, 10 100 t and 250 t respectively, and the P loss loads were 290 t, 400 t, 3 000 t and 50 t, respectively, in the Taihu Lake region. With the change in planting structure, rice paddy was no longer the largest source of N and P loss in the farmland, but the total N and P loss from orchard, vegetable field, and tea garden was the largest; these are currently the priority control objects of N and P loss in farmland of the Taihu Lake region. It is suggested that in the next stage, the prevention and control of agricultural non-point source pollution should focus on the optimization of planting structure, and strengthen research on the prevention and control technology of P pollution, in order to achieve clean and sustainable development of the planting industry in the Taihu Lake region.

Optimizing chemical fertilizer use in a tea plantation based on the SWAT model

MENG Lingyu, YANG Haoyu, ZHANG Naiming, DENG Hong, LIU Huijian, BAO Li, HUANG Weiheng

2020, 28(8): 1239-1248. doi: 10.13930/j.cnki.cjea.200122

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Optimizing fertilizer use is one of the main ways to improve soil fertility and reduce the eutrophication of surface water in tea plantations, simultaneously. This approach will play an important role in improving the ecological environment of tea plantations. The study used field data, collected from March to September 2018, and meteorological and hydrological data from 2011 to 2016 in the Mengbang Reservoir Area, Menghai County, Yunnan Province, China, to build a regional model aimed at reducing fertilizer use in a tea plantation based on the soil and water assessment tool (SWAT) model. Four different fertilizer application methods were examined (conventional chemical fertilizer and three combined application methods: 70% chemical fertilizer + organic fertilizer, 70% chemical fertilizer + slow-release fertilizer, and 70% chemical fertilizer + soil modifier). Their effect was calculated using fuzzy comprehensive evaluation to systematically study the optimal application of chemical fertilizers in a Menghai tea plantation. The results showed that: 1) the simulation and observed results of monthly runoff and water quality in the Mengbang Reservoir Area had the same trends (R² = 0.895, Nash-Sutcliffe efficiency = 0.837), and the model fitted well. 2) In terms of overall benefit, the water environment index (0.412) contributed more than the soil fertility index (0.317) and the economic benefit index (0.271). 3) The optimal chemical fertilizer application for tea plantations in Menghai County was the 70% chemical fertilizer + slow-release fertilizer combination. Its soil fertility benefit index, water environment benefit index, economic benefit index, and comprehensive benefit evaluation index scores were 0.96, 0.97, 0.99, and 0.97, respectively. In summary, a combined application of 70% chemical fertilizer + slow-release fertilizer can effectively reduce the risk of eutrophication of surface water in tea plantations and improve the soil fertility, without affecting the economic benefits.

Effects of soil flooding of biogas slurry on root-knot nematode (Meloidogyne spp.) and soil nematode community

LI Yufei, LIU Bensheng, XU Junxiang, LI Jijin, LANG Qianqian, QIAO Yuhui, SUN Qinping

2020, 28(8): 1249-1257. doi: 10.13930/j.cnki.cjea.200099

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Root-knot nematodes (RKN, Meloidogyne spp.) cause soil-borne diseases in food crops, and can lead to a huge crop damage worldwide. It has been demonstrated that application of biogas slurry during planting is an effective method to control diseases caused by RKN. We explored the inhibition effect of biogas slurry on RKN by a soil flooding method to provide scientific basis for a new idea to prevent and control soil-borne diseases. A pot experiment was conducted using soil infected with RKN from a vegetable greenhouse. Four treatments were set: 1) biogas slurry was routinely applied to soil three times during the planting period (BS), with an application rate of NH₄⁺ 50 mg·kg^-1; 2) soil was pretreated by flooding with 70% biogas slurry twice before planting (BSS); 3) soil was covered with mulching films and heated to 45 ℃ (HE) to simulate a conventional smothering process and, 4) soil was untreated (CK). The most obvious inhibition of RKN was BSS treatment, with a control effect of 97.1%. The root-knot index in BSS treatment decreased by 96.9% and 92.9%, respectively, compared with that of HE and BS. However, this method showed a small trend of inhibiting crop growth. Although HE significantly reduced the number of RKN compared with CK, the RKN number rebounded at the later stage (60 d after treatment), and even was higher than that of CK. Taken together, the proportion of herbivores nematode was the highest in CK (mean 81.8%), while bacterivores dominated in the two biogas slurry treatments, BS and BSS (mean 78.3%). Omnivores and carnivores nematode disappeared in soil flooded with biogas slurry, although they reappeared at the destructive sampling period, the relative abundance was still very low. In the pot system, soil flooding with biogas slurry before planting significantly improved the inhibition effect on RKN compared with the application of biogas slurry during planting. This result revealed that the critical period of using biogas slurry to prevent and control RKN is at the larval stage: that is, before nematodes invade plant roots. Further studies are needed under field conditions to study the toxic effects of biogas slurry flooding in plants, and the potential risk of environmental pollution.

Testing the performance of compound microbial additives in silage maize nutrients and the effect of feeding Tan sheep

WANG Xiaoping, WANG Xiaoqi, LI Biao, WANG Lin, DUAN Ziyuan

2020, 28(8): 1258-1264. doi: 10.13930/j.cnki.cjea.200053

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Abstract:
Silage can be affected by a variety of factors during fermentation, which reduce its feed and fattening qualities. We selected and combined silage microbial additives to address the problems that occur during the natural fermentation of silage maize, such as nutrient loss and mold. The performance of a compound of one strain of lactic acid bacteria (Lactobacillus acidophilus) and one strain of yeast (Saccharomyces cerevisiae), which were isolated from mixed silage maize collected in multiple spots in the central arid area of Ningxia Hui Autonomous Region, China, were tested. The compound lactic acid bacteria-yeast strain microbial additive was inoculated into silage maize; at the same time, silage without and with commercial microbial additives were set as the control group. The nutritional composition was determined after a 45-d fermentation period. The results indicated that the neutral detergent fibers (NDF) and acid detergent fibers (ADF) of the feed decreased significantly after treatment with compound microbial additives, while the dry matter content and ether extract (EE) increased significantly. The degradation of crude protein (CP) was slightly inhibited, although this was not significantly different to the control. The 75-d fattening study and 5-d digestive and metabolic experiments for Tan sheep showed that the average daily feed intake significantly increased, while the difference in the average daily grain, final weight and ratio of feed to gain were not statistically significant. During the course of fattening, the final body weight, average daily gain, and feed efficiency increased. Then, the digestive and metabolic experiments for Tan sheep were showing that the apparent digestibility for CP and EE were significant increased. NDF tends to increased, while the different in the apparent digestibility of ADF was statistically insignificant. Thus, it is clear that the compound microbial additives noticeably improved the feed quality of silage and that silage maize inoculated with compound microbial additives facilitated the growth performance of Tan sheep.

Study on the impact of China's urbanization on agricultural ecological effi-ciency:Based on panel data of 13 major grain-producing regions in China from 2009 to 2018

SHANG Jie, JI Xueqiang, CHEN Ximing

2020, 28(8): 1265-1276. doi: 10.13930/j.cnki.cjea.200135

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Abstract:
Urbanization is an important factor to impact agricultural ecological efficiency. However, most of the existing studies have discussed the impact of urbanization on agricultural ecological efficiency from a single perspective. Further, these studies are often affected by the impact of exogenous environment or other random factors during the measurement of agricultural ecological efficiency. To analyze the impact of urbanization on agricultural ecological efficiency more comprehensively and accurately, the present study used the three-stage SBM-DEA model, which provides simultaneously evaluation of both the undesirable and desirable outputs, entropy value method, and Tobit model, based on panel data obtained from 13 major grain-producing regions in China from 2009 to 2018. Various models and methods were used to study the impact of urbanization on agricultural ecological efficiency from multiple perspectives based on theoretical analysis. Our results showed that: 1) the impact of exogenous environment and random interference significantly impacted the agricultural ecological efficiency. After excluding these impacts, the agricultural ecological efficiency of the 13 major grain-producing regions in China changed significantly. Additionally, unlike the existing studies, the impact of urbanization on agricultural ecological efficiency too changed, after the effects of exogenous environment and random interference were removed. 2) The agricultural ecological efficiency of China's 13 major grain-producing regions showed a continuous growth trend from 2009 to 2018. The average annual efficiency, after excluding the impact of exogenous environment and random interference, increased from 0.53 in 2009 to 0.80 in 2018. However, there was a big gap in the agricultural ecological efficiency among different regions. For example, in 2018, the agricultural ecological efficiency of Hebei and other regions reached the frontier (1.00), but that of Inner Mongolia was only 0.45. 3) Urbanization as a whole improved the agricultural ecological efficiency. The comprehensive index of urbanization significantly affected agricultural ecological efficiency (at a level of 1%, impact coefficient: 0.60). 4) Various indicators of urbanization differently impacted the agricultural ecological efficiency. The population urbanization rate showed an insignificant negative impact on the agricultural ecological efficiency. The per capita disposable income of urban residents and urban economic density significantly positively affected the agricultural ecological efficiency. The output value of the secondary and tertiary industries, proportion of built-up area and per capita built-up area had significantly negative effect on the agricultural ecological efficiency. To further elucidate the role of urbanization in promoting agricultural eco-efficiency, this article proposed suggestions to modify the relevant policies, based on the research results from three aspects of population, economy, and land urbanization.

Research on the relationship between agricultural economic growth, agricul-tural structure, and agricultural non-point source pollution in Fujian Province

YANG Jun, LI Jianqin

2020, 28(8): 1277-1284. doi: 10.13930/j.cnki.cjea.190871

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Abstract:
Agricultural structure is considered to play an important role in regulating the dual pressures of economic growth and non-point source pollution from agricultural development. The total amount of surplus nitrogen, which is the main source of agricultural non-point source pollution, was calculated according to Truog's nutrient balance theory. The impulse response function and variance decomposition methods, based on the vector error correction model (VECM), were used to investigate and explain the relationship among agricultural economic growth, agricultural non-point source pollution, and agricultural structure in Fujian Province from 1998 to 2017. The research results showed that: 1) there was a relationship of long-term equilibrium among agricultural economic growth, agricultural non-point source pollution, and agricultural structure. 2) The Granger causality test showed that: agricultural non-point source pollution and economic growth were Granger causes for each other; agricultural structure was the Granger cause of non-point source pollution and agricultural economic growth; and agricultural economic growth was the Granger cause of agricultural structure. 3) The results of variance decomposition showed that there was little impact of agricultural economic growth and agricultural structure on agricultural non-point source pollution. The variance contribution of the impact of agricultural economic growth and agricultural structure on agricultural economic growth was 4.31% and 4.02%, respectively. The agricultural non-point source pollution had a great effect on agricultural economic growth. In the next 10 years, the variance contribution from agricultural non-point source pollution would reach 47.02%. 4) In the light of these findings, potential policy suggestions include: continuing to rectify agricultural non-point source pollution; encouraging the development and application of green agricultural technology and methods; increasing the role of the construction of agricultural infrastructure and farmer organization, introducing more detailed and guided financial policies to support agriculture; and strengthening the awareness on green consumption.

2020 Vol. 28, No. 8