中国生态农业学报(中英文)

Research progress toward and emission reduction measures of ammonia volatilization from farmlands in China

LIU Baishun, HUANG Lihua, HUANG Jinxin, HUANG Guangzhi, JIANG Xiaotong

2022, 30(6): 875-888. doi: 10.12357/cjea.20210820

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Abstract:
Ammonia volatilization is the main mechanism of nitrogen loss in farmlands. It not only reduces nitrogen use efficiency but also causes ecological and environmental problems such as haze, atmospheric dry and wet deposition, and greenhouse effects. In this study, we briefly analyzed the research status of ammonia volatilization in farmlands within the past 10 years (2011−2020) and the corresponding temporal and spatial variation characteristics in China; further investigated the influence mechanism of ammonia volatilization; reviewed the development process, principles, advantages, and disadvantages of the determination methods for ammonia volatilization in farmland; and summarized the existing problems of the main measures for reducing ammonia emissions. Research on farmland ammonia volatilization has shown rapid development and significant international trends in China, but the international influence of this researches needs further improvement. Due to its vast territory, ammonia volatilization in farmland presents the characteristics of large temporal and spatial variations, which are closely related to crop types, fertilization, climate, soil, and crop growth period. To regulate and mitigate ammonia volatilization, nitrogen fertilizer application should be managed scientifically according to local conditions. After more than 200 years of development, methods for determining ammonia volatilization in farmland have gradually developed from initial indirect estimation to chemical measurement and spectral analysis, and the accuracy and scope of measurement have been greatly improved. Additionally, we summarized the main measures and existing problems in reducing ammonia volatilization from farmlands in China. In the future, researches on the microbiological mechanism and temporal-spatial variability of ammonia volatilization in farmland should be increased, air-space-land integrated monitoring technology for ammonia volatilization should be applied in farmland, and the mechanization and intelligence of farming should be strengthened; moreover, a more accurate evaluation system for reducing ammonia emissions should be gradually established. The suggested improvements will provide a reference for future research on ammonia volatilization and the formulation of reasonable emission reduction policies in China.

Plant and arbuscular mycorrhizal fungal diversities in field margins of the globally important agricultural heritage rice-fish system

ZHOU Jingyi, ZHAO Lufeng, TANG Jianjun, QIU Ziyue, LOU Liyi, CHEN Chaowei, WU Jing, LIN Jiachen, GUO Liang, HU Liangliang, CHEN Xin

2022, 30(6): 889-899. doi: 10.12357/cjea.20210524

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Abstract:
The role of Globally Important Agricultural Heritage Systems (GIAHS) in agro-biodiversity conservation is recently concerned. Studies have shown that the GIAHS-Qingtian rice-fish system has maintained a high diversity of rice varieties and local common carp population. The wild plant species diversity and the associated biota maintained in the GIAHS-Qingtian rice-fish system, however, are less well known. In this study, we examined plants and the associated arbuscular mycorrhizal fungi (AMF) in the field margins of the GIAHS-Qingtian rice-fish system. At the pilot site of the rice-fish system in Qingtian County, southern Zhejiang Province (120°26′–121°41′E, 27°25′–28°57′N), we investigated wild plant species diversity and collected soil samples from the rhizosphere at the field margin along a hillside with terrace fields. The α and β diversity indices of wild plants were calculated. The AMF communities in the soil samples were determined using high-throughput sequencing, and their diversity and composition were analyzed. No significant difference was found in the sample plots at different position along the slope. In the GIAHS-Qingtian rice-fish system, 109 vascular plant species belonging to 53 families in the field margin were found. Plant species α diversity (Shannon-Wiener index) was 0.74–0.84, and the β diversity (Whittaker index) was 0.67–0.77. The average AMF colonization rate of the plant species in the field margin was 6.67%–44.44%. Nine families, 14 genera, and 62 AMF species were found in soil along the field margin. The dominant AMF family was Glomeraceae, with a relative abundance of 87.29%–89.64%, and the dominant genus was Glomus (87.29%–89.64%). Carbon, nitrogen, phosphorus, and potassium contents were relatively high in the rhizospheric soil at the field margin. Correlation analysis showed that the AMF species diversity index (Shannon index) was positively correlated with the plant species diversity index (species richness). At the genus level, the AMF species diversity index (Shannon index) of Glomus was positively correlated with total soil nitrogen, available nitrogen, organic carbon, and organic matter. At the operational taxonomic unit (OTU) level, available phosphorus content had the most significant effect on the soil AMF community among the soil properties tested based on redundancy analysis. Our results showed that high plant species diversity and associated AMF were conserved in the GIAHS-Qingtian rice-fish system. These results enhance our understanding of the important role of GIAHSs in maintaining the biodiversity of agricultural ecosystems.

Effects of reduced chemical nitrogen input combined with organic fertilizer application on the productivity of winter wheat and summer maize rotation and soil properties in central Henan Province

YE Shengjia, ZHENG Chenmeng, ZHANG Ying, LIU Xing

2022, 30(6): 900-912. doi: 10.12357/cjea.20210658

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Abstract:
To explore the potential of nitrogen (N) reduction in winter wheat and summer maize rotation system located at central Henan Province and pursue the best crop nutrient management strategy, the effects of reduced chemical N fertilization (RCN) combined with organic fertilizer application (OFA) on rotation system productivity and soil properties were assessed through a field experiment over three years. Ten treatments were employed in the present study: without fertilization (CK), farmers’ chemical N application rate (100%CNF), gradually reducing the chemical N application rate by 20% (80%CNF, 60%CNF, and 40%CNF), applying organic fertilizer alone (OF), and combined application of RCN and OFA (100%CNF+OF, 80%CNF+OF, 60%CNF+OF, and 40%CNF+OF). The differences in grain yields and aboveground biomass of wheat and maize, soil physicochemical properties, enzymes activities, and bacterial communities among treatments were analyzed. In the absence of OFA, the highest grain yield and aboveground biomass for wheat and maize were achieved with 80%CNF. Compared with 100%CNF, grain yield and aboveground biomass of wheat in 80%CNF significantly increased by 9.67%−10.55% and 30.53%−35.76%, respectively, and those of maize in 80%CNF significantly increased by 28.06%−51.42% and 29.62%−41.27%, respectively, suggesting that farmers’ conventional fertilization constituted excessive N supply. Furthermore, reducing 20% of farmers’ chemical N fertilization significantly increased rotation system productivity. The OFA could further release the space for N reduction, which was confirmed by the lack of statistical difference in wheat grain yield among 60%CNF+OF, 40%CNF+OF, and 80%CNF; and in maize grain yield between 60%CNF+OF and 80%CNF. The RCN alone or in combination with OFA did not alter the contents of soil organic matter, easily oxidized organic carbon, and total nitrogen, or pH, but substantially reduced the NO₃⁻-N content. The effects of RCN and OFA on the contents of NH₄⁺-N, available phosphorus, and available potassium varied among treatments. Compared to 100%CNF, RCN combined with OFA significantly increased the activities of urease and arylsulfatase and reduced the activity of β-glucosidase but did not affect the activities of sucrase, alkaline phosphatase, and dehydrogenase. The combination of RCN with OFA improved the α diversity of the bacterial community. This was indicated by the Simpson and evenness indices in 60%CNF+OF and 40%CNF+OF being significantly higher than those of 100%CNF. The RCN combined with OFA also significantly changed the β diversity of the bacterial community, which was more dependent on RCN rather than OFA. At the phylum level, Proteobacteria, Actinobacteria, and Acidobacteria dominated the bacterial community. The combinations of RCN and OFA significantly reduced the average relative abundance of Actinobacteria by 10.92%–14.39%. At the genus level, RCN combined with OFA significantly increased the average relative abundances of unclassified GP6 and Sphingomonas, whereas reduced the average relative abundances of Nocardioides, Kribbella, Lechevalieria, Promicromonospora, Massilia, Glycomyces, and Dongia. Redundancy analysis demonstrated that available potassium and NO₃⁻-N contents were the two most important soil environmental variables driving the bacterial community structure. In addition, co-occurrence network analysis also indicated that RCN strengthened the interactions of species in the bacterial community and yielded highly complex and connected associations among bacterial taxa. In the current study, reducing 60% and 40% of farmers’ chemical N fertilization in wheat and maize production, respectively, and in combination with 3000 kg∙hm⁻² of OFA in each season could maintain relatively high rotation productivity. This fertilization regime not only maximized the potential of N reduction in the rotation system but also improved soil microbial diversity and community structure. Notably, the optimal fertilization regime obtained here must be re-verified across crop varieties, organic fertilizers, and fields. Moreover, the long-term effects of RCN and OFA on yield and soil properties in winter wheat and summer maize rotation systems in central Henan Province need to be further assessed.

Effects of mulching practices on soil carbon, nitrogen contents, and grain yield, water and nitrogen use efficiencies of summer maize

WANG Zhen, SUN Jun, DU Yadan, SUN Dan, GAN Haicheng, NIU Wenquan

2022, 30(6): 913-923. doi: 10.12357/cjea.20210574

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Abstract:
Ridge furrows with plastic film mulching (RFM) and straw mulching (SM) are beneficial for improving grain yield and rainwater use efficiency; however, it is not clear whether they can affect the changes in soil carbon and nitrogen under continuous RFM and SM in the Loess Plateau of China. A 2-year field experiment (2019–2020) was established with three treatments, namely, RFM, SM, and no mulching (NM), to study the effects of RFM and SM on soil water and heat conditions, soil organic carbon and nitrate nitrogen contents, soil respiration rate, as well as summer maize nitrogen uptake, aboveground dry matter accumulation, evapotranspiration, soil water and nitrogen use efficiencies, and grain yield. Finally, a mulching method suitable for rainfed agriculture in the semi-arid Loess Plateau was proposed to provide a scientific basis for summer maize planting and environmental protection in this area. The results showed that compared with NM, RFM significantly increased the soil temperature by 0.5–1.0 °C at 5 cm soil depth and by 0.2–0.7 °C at 10 cm soil depth (P<0.05), accelerated the decomposition of soil organic carbon, significantly decreased the soil organic carbon content by 4.2%, and significantly enhanced the soil respiration rate by 33.2% (P<0.05). SM significantly decreased the soil temperature by 0.2–1.5 °C at 5 cm soil depth and by 0.5–1.0 °C at 10 cm soil depth (P<0.05), increased the soil organic carbon content by 21.3% (P<0.05), and decreased the soil respiration rate by 44.0% (P<0.05). Compared with NM, RFM significantly decreased the soil nitrate nitrogen content in the furrow (P<0.05). SM significantly increased the soil nitrate nitrogen content at 0–80 cm depth (P<0.05), but significantly reduced the nitrate nitrogen content in the deeper soil (P<0.05). The results showed that SM significantly increased the nitrate nitrogen content of the soil surface, promoted the supply of nitrogen, and reduced the residual nitrate nitrogen content as well as the leaching loss. SM and RFM significantly increased the soil water content by 23.8% and 15.2% (P<0.05), respectively; increased the plant nitrogen uptake by 37.6% and 11.3% (P<0.05), respectively; transferred more nitrogen to the grains; significantly increased the grain nitrogen uptake, nitrogen harvest index, and grain dry weight (P<0.05); increased the aboveground dry matter accumulation (P<0.05); significantly improved the grain yield of summer maize by 16.8% and 9.2% (P<0.05), respectively; and increased the water use efficiency by 13.0% and 9.1% (P<0.05), respectively. Mulching practices (RFM and SM) can increase the soil water content, plant nitrogen uptake, and grain yield. However, compared with RFM, SM was more effective in conserving soil water, increasing production, and reducing carbon dioxide emissions. SM could increase the summer maize nitrogen uptake and utilization as well as grain yield of summer maize by improving the soil moisture content, soil organic carbon content, and soil nitrogen availability. Therefore, SM is an effective mulching method for rainfed agriculture in the semi-arid Loess Plateau, China.

Water-nitrogen coupling influence on rhizosphere environment and root morphology of rice under wheat straw return

ZHANG Yujie, MA Peng, WANG Zhiqiang, YANG Zhiyuan, SUN Yongjian, MA Jun

2022, 30(6): 924-936. doi: 10.12357/cjea.20210552

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Abstract:
To provide a theoretical and practical basis for establishing a water-nitrogen coupling model suitable for rice growth under straw return in the Chengdu Plain, the relationship between water management, straw return, N application, and rice root morphogenesis was studied through field experiments. The effects of water-nitrogen coupling on the rhizosphere environment and root development of hybrid indica rice (Oryza sativa) ‘F You 498’ under wheat straw return conditions were investigated with the application of two water treatments, three N treatments, and two straw return treatments. The two water treatments were alternate dry-wet irrigation (W1) and submerged irrigation (W2); the straw return treatments were full-burying and return of wheat straw (S1) and no straw return (S0); and the N treatments involved the application of 150 kg∙hm⁻² of N applied at ratios of basal∶tillering∶panicle fertilizers of 3∶3∶4 (N1), 7∶3∶0 (N2), and 0 (N0). The results showed that compared with W2, W1 promoted straw decomposition before the jointing stage, increased the total organic acid content of rhizosphere soil after the jointing period (1.38%–8.49%) and microbial biomass C content of rhizosphere soil before maturity (0.25%–12.93%), increased root activity during the entire growth period, and increased root morphological indices of the rice population, except at 10 days after transplanting and at the mature stage (18.53%–75.83% of root length, 10.57%–101.33% of root number, 2.49%–88.24% of root volume, and 8.91%−68.08% of root surface area). Compared with W1, W2 increase the total organic acids (3.34%) and microbial biomass C content (2.69%–6.23%) at the mature stage, and the decomposition of straw and the root morphological indices of single stems (12.03%–27.21% of root length and 9.05%–51.44% of root number). Compared with S0, S1 treatment inhibited root morphology development and reduced root activity (2.47%–45.83%), but increased the total organic acid content (8.02%–22.74%) and microbial biomass C and N levels of rhizosphere soil (1.58–31.22%), and the effect of improvement was highly noticeable under W1. The application of N fertilizer promoted the decomposition of straw, increased the total organic acids and microbial biomass C and N contents of rhizosphere soil, promoted root development, and increased root activity. Compared with N0, the optimal N application mode (N1) promoted the root development of single stems (8.27%–38.09% of root length and 2.96%–36.66% of root number) and promoted and maintained the root activity (2.26%–156.35%) in the middle and late growth stages; whereas the conventional N application mode (N2) increased the population root index (12.68%–44.32% of root volume and 4.91%–55.82% of root surface area) and root activity only in the early growth stage (22.01%–29.31%). W1 irrigation coupled with optimized N application promoted straw decomposition, significantly accelerated root growth and development, increased total organic acid content, microbial biomass C and N contents, and root activity in rhizosphere soil, and delayed root senescence. Therefore, under the condition of straw return, the optimized N application mode with W1 is the most suitable agriculture model.

Effects of long-term nutrient recycling pathways on soil nutrient dynamics and fertility in farmland

XING Li, ZHANG Yuming, HU Chunsheng, DONG Wenxu, LI Xiaoxin, LIU Xiuping, ZHANG Lijuan, WEN Hongda

2022, 30(6): 937-951. doi: 10.12357/cjea.20220306

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Abstract:
Nutrient recycling plays an important role in soil nutrient conservation and is an effective measure for fertilizing soils in agro-ecosystems. This study relied on a long-term experiment (since 2001) on an agricultural management system conducted by the Luancheng Agroecosystem Experimental Station of the Chinese Academy of Sciences. The aim of this study was to provide a theoretical basis for developing agricultural management measures for soil fertility cultivation and enhancing soil carbon sequestration potential. Four treatments were set: no fertilization (i.e., conventional, CK), all applications of chemical fertilizer (NPK), chemical fertilizer and 80% of the above-ground output feeding pigs through belly (as pig manure) to the field (MNPK), and chemical fertilizer and straw crushed direct return to the field (SNPK). The soil organic matter (SOM), total nitrogen (TN), available phosphorus content (AP), and composition of soil carbon and nitrogen pools of the treatments were determined. The results showed that the implementation of nutrient recycling significantly increased the contents of SOM, TN, and AP in the soil in the order of MNPK > SNPK > NPK > CK. After 18 years, we found that SOC, TN, and AP storage in the 0–20 cm soil layer increased in MNPK by 9.21 t(C)∙hm⁻², 1.01 t(N)∙hm⁻², and 144.87 t(P)∙hm⁻², respectively. The SOC, TN, and AP storage in SNPK increased by 4.51 t(C)∙hm⁻², 0.56 t(N)∙hm⁻², and 24.68 t(P)∙hm⁻², respectively. The SOC, TN, and AP storage in NPK increased by 0.64 t(C)∙hm⁻², 0.16 t(N)∙hm⁻², and 29.00 t(P)∙hm⁻², respectively. This shows that the fertilizing effect of pig manure was significantly higher than that of direct straw return; and the effect of direct straw return on the expansion of carbon and nitrogen pools was significant, but direct straw return had a minor effect on the construction of an effective phosphorus pool. Under the fertilization level of this study, the application of chemical fertilizer alone can maintain the basic balance of soil organic carbon and nitrogen pool, and have a significant effect on phosphorus pool expansion. Compared to NPK, MNPK and SNPK significantly increased the contents of soil labile organic carbon (LOC) and resistant organic carbon (ROC), and significantly increased the proportion of active organic carbon in total organic carbon; thus, the ratio of LOC+DOC to TOC increased from 9.2% of NPK to 19.0% (MNPK) and 16.3% (SNPK), respectively. The results showed that the recycling of nutrients based on the application of chemical fertilizer not only promoted the accumulation of a stable carbon pool but also expanded the soil active carbon pool, which played a positive role in improving the fertilizer conservation and supply capacity of soil. Based on the effects of different fertilization methods on the composition of the soil nitrogen pool, the contents of soil nitrate, ammonium, and total nitrogen supply capacity in the MNPK treatment was higher than those in the SNPK treatment, whereas the SNPK treatment had a significantly higher amino-sugar-nitrogen content than MNPK. This indicates that straw return was more favorable for microorganisms to fix available nitrogen into the transition pool than belly return. Not only does it reduce the export risk of active nitrogen to the environment but also improves the storage and supply capacity of soil to nitrogen. In view of the complementary effect of nutrients returning to the field and straw returning directly to the field, it is suggested that organic manure should be promoted to replace part of the chemical fertilizer based on straw returning in agricultural production.

Microstructure characteristics of soil aggregates of maize farmland under different utilization patterns of green manure in a desert oasis area

LYU Hanqiang, HU Falong, YU Aizhong, SU Xiangxiang, WANG Yulong, YIN Wen, CHAI Qiang

2022, 30(6): 952-964. doi: 10.12357/cjea.20210467

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Abstract:
It is difficult to describe the microstructure characteristics of soil aggregates using traditional methods. Although classification and analysis of <0.25 mm aggregates are necessary, knowledge about them is insufficient. Thus, accurate evaluation of the effect of agronomic measures on soil aggregate structure characteristics using modern microscopic techniques is important for soil management via the adoption of scientific methods. A long-term positioning field experiment in 2016 in the Shiyang River Basin of desert oasis area of the Hexi Corridor was conducted to investigate the effect of green manure retention practices on soil aggregate characteristics under a wheat-green manure-maize rotation system. The different practices included tillage with full quantity of green manure incorporated into the soil (TG), no-tillage with full quantity of green manure mulched on the soil surface (NTG), tillage with above-ground green manure moved and roots incorporated into the soil (T), no-tillage with above-ground green manure moved (NT), and conventional tillage without green manure (CT, the control). In 2019 to 2020, a scanning electron microscopy was used to analyze the microcosmic images of 0–30 cm soil during maize tasseling and silking stages to qualitatively reveal the apparent characteristics. Nano Measurer software was used to quantitatively analyze the soil particle size and aggregate characteristics. Results showed that most of the soil particle size under CT was less than 0.25 mm, of which 23.9%−27.4% were sand, a kind of smooth surface and regular shape with particle size ranged from 0.05 to 0.25 mm. Others were silt and clay (USDA), and the number of soil aggregates accounted for 9.1%−9.6% of the total particles. Compared to those under CT, the soil particles of NT and T were very fine sand with particle size ranging from 0.05 to 0.1 mm, and the number of soil aggregates under the two treatments was improved by 10.1%−23.3% and 14.4%−17.3%, respectively. The TG and NTG treatments facilitated the reduction in the particle size of single-grain sand in the maize field. These small single grains constituted large aggregates with rough, porous, and uneven surfaces and were attached by a lot of silt and clay. The particle size of large aggregates ranged from 0.1 to 0.25 mm. Compared to that under CT, the number of soil aggregates under TG and NTG treatments was improved by 25.8%−50.9% and 34.1%−43.4%, respectively. In addition, soil under NTG exhibited structural performance and potential to form large aggregates with particle size >0.25 mm. Therefore, in a desert oasis area, a full quantity of green manure was incorporated into the soil or mulched on the soil surface with no tillage after wheat-green manure cropping system, and the soil under both the systems had superior structural characteristics of soil aggregates compared to that under the control system.

Influences of continuous monoculture of alfalfa and rotation of annual crops on soil fungal communities in the semi-arid Loess Plateau

SUN Pengzhou, LUO Zhuzhu, LI Lingling, NIU Yining, CAI Liqun, LIU Jiahe, WANG Xiaofei

2022, 30(6): 965-975. doi: 10.12357/cjea.20210348

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Abstract:
Lucerne (Medicago sativa) is widely planted in the Loess Plateau of western China and can accumulate soil carbon and nitrogen nutrients. However, continuous cropping of lucerne has consumed soil water and phosphorus for many years leading to a decrease in soil quality and alfalfa productivity. Therefore, after lucerne is planted for a certain period, it is necessary to plant the stubble and rotate annual crops to promote sustainable land use. Choosing suitable crops can improve the stability of the soil ecosystem. In this study, we analyzed the effects of long-term continuous cropping of alfalfa and rotation with annual crops on the structure and diversity of soil fungal communities in semi-arid areas based on a long-term localization experiment in the rainfed agricultural area of the Loess Plateau using the FUNGuild platform to predict the ecological functions of fungi in different treatments. The cropping systems included monocropping for 16 years of lucerne (LC), field fallow for 7 years after monocropping for 9 years of lucerne (rotation of lucerne-fallow, LF), field fallow for 2 years after monocropping for 9 years of lucerne and then planting corn (Zea mays) for 5 years (rotation of lucerne-fallow-corn, L_FC), planting potato (Solanum tuberosum) for 7 years after monocropping for 9 years of lucerne (rotation of lucerne-potato, LP), and planting millet (Panicum miliaceum) for 7 years after monocropping for 9 years of lucerne (rotation of lucerne-millet, LMi). A total of 7 phyla, 25 classes, 77 orders, 169 families, and 347 genera of fungi were identified. The fungi were mainly Ascomycota, Zygomycota, and Basidiomycota at the phylum level. Ascomycota was the first dominant phylum in different treatments, and its relative abundance ranged from 69.17% to 88.22%, which was much greater than that of the subdominant phyla Zygomycota (6.72%–19.88%) and Basidiomycota (1.64%–9.01%). The dominant genera varied in different treatments, with Phaeomycocentrospora in LC treatment, Gibberella in LF, LP, and LMi treatments, and Mortierella in L_FC treatment. Redundancy analysis revealed that soil available phosphorus (P=0.002) was the main factor influencing the soil fungal community structure. The alpha diversity results showed that crop type had no significant impact on the diversity and richness of the soil fungal communities. However, the Shannon index was significantly negatively correlated with the soil nitrate-nitrogen content (r=−0.553, P<0.05) and the Simpson index was significantly positively correlated with the soil nitrate-nitrogen content (r=0.515, P<0.05). Functional prediction with FUNGuild showed that pathotrophs (25.44%–39.27%) was the dominant fungal functional group of loessal soil in this study. After lucerne rotation with annual crops, the relative abundance of transitional fungal groups, such as soil saprotrophs-symbiotrophs, pathogens-saprotrophs-symbiotrophs, and pathotrophs-saprotrophs-symbiotrophs, changed, whereas the relative abundance of pathotrophs-saprotrophs decreased. Available phosphorus (P=0.002) and nitrate-nitrogen (P=0.02) were the main environmental factors affecting the changes in soil fungal functional groups. In conclusion, rational cropping systems are conducive in enriching the structure of soil microbial communities and promoting the stability of the soil ecosystems in the region. The results of this study can provide reference and data support for the prediction of soil fungal communities and their functions in different planting systems.

Comparative study of different meteorological yield separation methods in waterlogging disaster assessment

MENG Huayue, WANG Zhaolin, YAO Pei, QIAN Long, CHEN Cheng, LUO Yunying, JU Xueliang

2022, 30(6): 976-989. doi: 10.12357/cjea.20210770

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Various meteorological yield separation methods have been applied in research on agricultural drought and flood disaster assessment. However, a specific comparison of the performance of these methods is rarely performed. The middle-and-lower reach of Yangtze River is an important cotton-production belt in China, but the region is frequently flooded, resulting in severe cotton yield losses. Hence, the objective of the present work was to assess the impacts of waterlogging disasters on cotton yield fluctuation in this cotton-production belt and to compare the accuracy of different meteorological yield separation methods for characterizing the correlations between waterlogging intensity and cotton climatic yields. Six provinces located in this belt were selected as the study areas, and the cotton climatic yields were calculated using various meteorological yield separation methods: linear fitness (LF), quadratic polynomial fitness (QP), cubic polynomial fitness (CP), HP filtering (HP), 3-year moving average (TMA), 5-year moving average (FMA), and five-point quadratic smoothing (FPQS). The performances of the employed methods were compared and well-performing methods were recommended. Specifically, the waterlogging intensity over cotton growth periods was quantified using the widely used standardized precipitation evapotranspiration index (SPEI). Next, according to the correlation between waterlogging intensity and cotton climatic yield, the performances of the seven methods were compared; in addition, this comparison was further performed on historical waterlogging area data. The results indicated that the long-term trends of cotton climatic yield derived from different methods were similar, whereas the short-term trends could be different or even opposite. The absolute values of the cotton climatic yield in Zhejiang Province were obviously lower than those in other provinces, indicating that the cotton plants in Zhejiang suffered much lower yield losses from climatic disasters. Regarding the correlation between waterlogging intensity and cotton climatic yield, LF, QP, and HP were preferable at the provincial scale, and HP, TMA, FMA, and FPQS performed satisfactorily at the county scale. Considering the ability of the seven methods to make predictions in historical waterlogging areas, HP, QP, and CP were the most satisfactory. In general, HP performed the best in various aspects. In a few cases (e.g., counties in Anhui Province), the relationships identified by various methods between waterlogging intensity and cotton climatic yields were different, which implies that the selection of meteorological yield separation methods may alter conclusions in some areas. All methods concluded that Hubei and Anhui Provinces suffered the most severe yield-reducing effect of cotton waterlogging, whereas results in other provinces were inconsistent. Although Hubei and Anhui Provinces were identified as the most waterlogging-affected provinces, the waterlogging intensity over cotton growth periods in these two provinces was lower than that in other provinces. In conclusion, HP filtering was demonstrated to be a preferable method for agricultural waterlogging assessment, and to prevent and control cotton waterlogging disasters in the middle-and-lower reach of the Yangtze River Plain, special attention should be given to Hubei and Anhui Provinces.

Effects of intercropping sweet potato in banana plantation on functional diversity of soil microorganisms

LI Yanpei, LIN Jiaqi, XIAO Shixiang, FENG Dou, DENG Yingyi, XUAN Weiyan

2022, 30(6): 990-1001. doi: 10.12357/cjea.20210665

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Abstract:
Reasonable intercropping patterns of crops have positive regulatory effects on the metabolic functional diversity of soil microbial communities. To explore the functional diversity of the soil microbial community and the characteristics of soil microbial transformation in soil nutrients and carbon source utilization in intercropping of banana and sweet potato, the changes in soil microbial functional diversity under banana monoculture and banana-sweet potato intercropping in ‘Guijiao No. 1’ banana plantation were compared and analyzed by using the Biolog method and principal component analysis. The results showed that the soil microbial metabolic activity from the vegetative growth stage to the budding stage of banana could be significantly improved by intercropping sweet potato in a banana plantation (P<0.01). The average color change rate of the intercropping soil microbial community was increased by 0.77–14.36 times, and the diversity, dominance, and richness of the soil microbial community increased by 0.09–1.01, 0.02–0.31, and 0.52–5.04 times, respectively, compared with those of the single cropping. However, there was no significant difference in soil microbial community evenness between intercropping and monoculture in the banana orchards. In addition, the carbon source utilization and metabolic activity of soil microorganisms increased in banana plantations intercropped with sweet potato. The metabolic activities of soil microorganisms for carbohydrates, amino acids, carboxylic acids, polymers, phenolic acids, and amines in intercropping were 13.81, 9.22, 5.38, 9.93, 6.08, and 3.46 times higher than those in the monoculture, respectively. There were differences in the utilization efficiency of different carbon sources between monoculture and intercropping systems. Carbohydrates and amino acids were the main metabolic carbon sources for soil microorganisms in intercropping, and polymer compounds and phenolic acids were the main metabolic carbon sources in the monoculture. The number of carbon sources utilized by soil microbial communities in intercropping was increased by 9–28 times compared with that of the monoculture, and the difference between intercropping and monoculture reached a very significant or significant level (P<0.01 or P<0.05, respectively). For banana intercropping with sweet potato, the utilization rate of carbohydrates by soil microorganisms was the highest, reaching 20.29%–25.25%, followed by amino acids with a utilization rate of 18.58%–20.31%, whereas the utilization rate of carboxylic acids, multi-cluster compounds, phenolic acids, and amines was lower than 18.28%. For banana monoculture, the utilization rate of multi-cluster compounds by soil microorganisms was the highest, reaching 0.60%–52.71%, followed by phenolic acids with the utilization rate of 13.94%–26.56%, whereas the utilization rate of the other four carbon sources was lower than 17.82%. There were notable differences in the utilization efficiency of single carbon sources by soil microorganisms between banana intercropping with sweet potato and banana monoculture. The main carbon sources used by intercropping soil microorganisms were d-cellobiose, N-acetyl-d-glucosamine, d-mannitol, α-d-lactose, d-galacturonic acid, d-xylose, l-arginine, and l-asparagine, accounting for 24.53%–31.12% of the total carbon sources. The carbon sources utilized by monoculture microorganisms included Tween-80, L-arginine, N-acetyl-d-glucosamine, L-asparagine, γ-hydroxybutyric acid, and α-d-lactose, accounting for 32.02%–78.45% of the total carbon source. Principal component analysis showed that carbohydrates and amino acids were the main carbon sources that changed the soil microbial diversity of banana intercropping with sweet potato. The diversity of rhizosphere soil microbial communities in banana plantations could be improved, and the carbon sources utilization efficiency and activity of the soil microbial community were improved by intercropping sweet potato; thus, the functional diversity of the rhizosphere microbial community was significantly improved.

Effects of controlled-release fertilizer residual coat accumulation on soil microbial communities

WANG Xuexia, CAO Bing, ZOU Guoyuan, ZHANG Jiajia, WANG Jiachen, LIU Dongsheng, CHEN Yanhua

2022, 30(6): 1002-1013. doi: 10.12357/cjea.20210226

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Abstract:
To explore the effect of controlled-release fertilizer residual coat accumulation on soil microbial communities, pot experiments were conducted with five treatments of 3.60–4.00 mm polyurethane addition (residues of controlled-release fertilizer coat), namely no residual coat (CK), 140 kg∙hm⁻² polyurethane addition (CR1), 280 kg∙hm⁻² polyurethane addition (CR2), 560 kg∙hm⁻² polyurethane addition (CR3), and 1400 kg∙hm⁻² polyurethane addition (CR4). Illumina MiSeq high-throughput sequencing technology was used to analyze the differences in soil bacterial and fungal community composition and diversity under different treatments. The results revealed that the contents of soil dissolved organic carbon (DOC), soil moisture (SM), and belowground biomass of maize (BGB) in CR4 treatment and NO₃⁻-N in CR3 treatment were significantly increased compared with those in CK; however, the soil pH and contents of available potassium, total nitrogen (TN), available phosphorus (AP), and NH₄⁺-N did not significantly change in all treatments. The operational taxonomic units of bacteria and fungi, the diversity index (Shannon), and the richness indexes (Ace and Chao) of the soil bacterial community increased as the polyurethane addition rate increased, and the difference between CR4 and CK was significant; however, the diversity and richness indexes of the soil fungal community did not significantly change under different treatments. The relative abundance of the soil bacterial and fungal communities at the phylum and genus levels changed as the polyurethane residual coat increased. The relative abundance of Proteobacteria, Bacteroidetes, and Burkholderia increased with the accumulation of the residual coat; however, the relative abundance of Acidobacteria and Sphingomonas showed the opposite pattern, and the difference was significant between treatments CR4 and CK. Compared with CK, treatment CR3 improved the relative abundance of Ascomycota significantly, treatment CR4 increased the relative abundances of Glomeromycota and Mortierella significantly. The Mantel test showed that soil DOC, AP, SM, and maize BGB were the key factors affecting the bacterial community structure, whereas soil DOC, TN, and SM were the key factors affecting the fungal community structure. Therefore, polyurethane residual coat addition can directly or indirectly improve the diversity of bacterial communities and affect the composition of bacterial and fungal communities in the short term by changing the soil DOC, SM and maize BGB, and other factors.

Advance in treatment of co-contamination of antibiotics and heavy metals from stock breeding

QI Shiying, YU Shaole, WU Juan, CHENG Shuiping

2022, 30(6): 1014-1026. doi: 10.12357/cjea.20210641

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Abstract:
With the rapid development of stock breeding and aquaculture in China, antibiotics, which are widely used to prevent and treat diseases and protect the health of animals, are discharged into the environment, thereby posing a threat to the ecological environment and human health. The frequent use of antibiotics has also resulted in increased microbial resistance. Heavy metals, as feed additives, can accumulate in the environment and cause pollution. In this review, the use of antibiotics and heavy metals in breeding and the pollution in animal species and the ecological environment are elaborated. Additionally, the existing treatment technology of antibiotics and the research progress of combined antibiotic-heavy metal pollution are summarized. The coexistence of antibiotics and heavy metals leads to the persistent combined pollution of antibiotics and heavy metals in wastewater and sediments produced by breeding. The co-selection mechanism driven by heavy metals affects the transmission of antibiotic-resistance genes to a certain extent. At present, the removal of antibiotics is based on advanced oxidation treatment supplemented by biological and ecological treatments. Biological treatment mainly uses microbial degradation of antibiotics and the adsorption capacity of activated carbon, whereas ecological treatment achieves pollutant removal via plants and other coupling processes in constructed wetlands. Advanced oxidation processes can achieve an efficient removal effect in a short time; however, the actual application must maintain a balance between the removal effect and cost. In addition, research on the antibiotics removal effect of various methods in the presence of heavy metal ions is lacking. Future research should focus on the following aspects: 1) ecological treatment techniques for co-contaminated aquaculture wastewater, such as artificial wetlands; 2) phytoremediation of co-contaminated sediment, especially plant selection and cultivation optimization; and 3) application of a combination of biological and ecological treatment technologies in practice.

Effect of centrifugal microfiltration on solid-liquid separation of pig farm wastewater

HU Xuzhao, DONG Hongmin, YIN Fubin, CHEN Yongxing

2022, 30(6): 1027-1035. doi: 10.12357/cjea.20210576

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Abstract:
Large amounts of livestock waste are discharged owing to the rapid development of the livestock industry, and they cause serious environmental pollution if not effectively treated. Livestock waste has high pollutant concentrations and complex compositions; hence, it requires effective pretreatment to avoid high post-treatment difficulties and low treatment effects. Solid-liquid separation has been reported to be a key technology for livestock waste treatment. This technology could produce a solid fraction that can be used as a high-nutrient fertilizer and reduce pollutants in the waste, lowering the loads for subsequent treatments. However, the effect and efficiency of the traditional solid-liquid separation process for treating livestock waste are relatively low and need to be improved. In this study, a new centrifugal microfiltration separator, used for the reduction of pollutants in livestock waste, was systematically evaluated under different conditions. This study monitored the correlation between total solid (TS) concentrations in pig farm wastewater and other related water quality parameters. The effects of different TS concentrations and mesh sizes on the rate and treatment costs of the separator were also studied. The TS was set to 1%, 2%, 3%, 4%, and 5%, and the mesh sizes were set to 15, 25, and 50 µm. The results showed that TS concentrations were negatively correlated with pH and electrical conductivity (EC), and positively correlated with chemical oxygen demand (COD), total nitrogen (TN), ammonia nitrogen (NH₄ ⁺-N) and total phosphorus (TP) in the wastewater. The correlation between TS and pH, COD, and TP was higher, with correlation coefficients (R²) of 0.57, 0.53, and 0.66, respectively. TS had no obvious correlation with turbidity, EC, TN, or NH₄ ⁺-N with R² of 0.33, 0.02, 0.10 and 0.03, respectively. The separator effectively removed TS from pig farm wastewater with a removal rate of 17%−68%. The removal rate of turbidity, COD, TN, TP and NH₄ ⁺-N were 3%–39%, 17%–59%, 4%–43%, 18%–54%, and 2%–17%, respectively. The removal rate of pollutants from pig farm wastewater increased with an increase in TS and a decrease in mesh size. The removal rate increased with increasing mesh size. The mesh size of 15 µm had the highest removal rates of 68% for TS, 40% for turbidity, 59% for COD, 42% for TN, and 54% for TP. There was a significant difference in treatment capacity between all mesh sizes (P<0.01). The treatment capacity of 50 µm mesh size was 14‒19 m³∙h⁻¹ and that of 15 and 25 µm mesh size was 2‒7 m³∙h⁻¹. The operational costs of centrifugal microfiltration machine using the screen sizes of 15, 25, and 50 µm in a pig farm having stock of 10 000 pigs as an example were estimated to be 2.44, 2.06, and 1.08 ¥∙m⁻³, respectively. The optimal mesh size and TS for treating pig farm wastewater were 50 µm and 5%, respectively, when considering removal rate and treatment capacity. Compared with traditional solid-liquid separators, the new separator has good application prospects because of its high separation effect and low energy consumption.

Effects of starvation stress on growth, antioxidant system and biochemical substances of Pomacea canaliculata (Lamark 1822)

XIAO Zeheng, GAN Tian, QIN Zhong, ZHANG Jia’en, SHI Zhaoji, ZHANG Chunxia

2022, 30(6): 1036-1044. doi: 10.12357/cjea.20210660

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Abstract:
Pomacea canaliculata is a highly dangerous invasive alien species that threatens rice and aquatic crop production, thereby causing large economic and ecological losses. Starvation stress is an environmental pressure that organisms often face. Under starvation conditions, organisms slow down growth and development and consume energy storage substances to provide energy to maintain life activities. To investigate the physiological and ecological responses of P. canaliculata to short-term starvation stress, the effects of 10, 20, and 30 d of starvation stress on the growth, antioxidant system, and biochemical substances of P. canaliculata were studied. The results showed that the free water content of the snails continued to increase with the increased starvation time and was significantly higher than that of the control from 20 d onwards (P<0.05). The mean content of free water of the snails in the treatment group was 84.19% at 30 d, which was significantly higher than that of the control group at 81.60% (P<0.05). The growth and development of snails were inhibited by starvation stress, and shell height and shell mouth length were significantly smaller than those of the control after 20 d (P<0.05) and the inhibition persisted until the end of the experiment. Body weight, shell width, and shell mouth width were not significantly different from those of the control during the first 20 d. As the starvation period was extended to 30 d, all the growth indicators were significantly lower than those of the control (P<0.05). Under the starvation stress, the antioxidant capacity of the snails was improved, and the total superoxide dismutase activity was significantly higher than that of the control from 20 d until the end of the experiment (P<0.05). There was no significant difference in the catalase activity and malondialdehyde content between the first 20 d and the control; however, they were significantly higher than those of the control with the extension of the starvation time to 30 d (P<0.05). There was no significant difference in the peroxidase activity or reduced glutathione content between the starvation stress and control groups. The glycerol content showed a trend of increasing then decreasing; it was significantly higher than that of the control at 10 d (P<0.05), then decreased rapidly, and was significantly lower than that of the control at 20 d and 30 d (P<0.05). The lipid content was lower than that of the control at all three observation periods (P<0.05), the glycogen content was lower than that of the control at 20 d and remained low until the end of the experiment (P<0.05). The total protein content was significantly lower than that of the control at 30 d (P<0.05) but did not differ significantly from that of the control at the other observation periods. The results suggest that P. canaliculata can mitigate the effects of short-term starvation stress via a number of physiological mechanisms such as slowing growth, increasing antioxidant capacity, and depleting endogenous biochemicals. Limiting the food source can inhibit the outbreak and damage caused by P. canaliculata to a certain extent.

2022 Vol. 30, No. 6