中国生态农业学报(中英文)

Effects of soil O₂ on CO₂ and N₂O concentration change under extreme precipitation

HAN Hui, QIAO Linming, WANG Xiaolu, DU Yanling, WANG Rui, GUO Shengli

2022, 30(10): 1555-1564. doi: 10.12357/cjea.20220116

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Abstract:
Agricultural soils play an important role in global greenhouse gases emissions. Precipitation is a critical factor driving soil greenhouse gases emissions in arid and semi-arid regions; however, the mechanism of greenhouse gas generation and emission under extreme precipitation has not been well documented. The aim of this study was to determine the relationships between greenhouse gases (CO₂, N₂O) concentrations and fluxes and soil O₂ dynamics under extreme precipitation. Based on an extreme precipitation scenario (100 mm), a simulation experiment of soil column was established at the Changwu Station, and high-frequency measurements of soil O₂, CO₂, and N₂O concentrations and CO₂ and N₂O fluxes were conducted under three soil management practices (no fertilization, nitrogen fertilization, and nitrogen fertilization plus straws incorporation). The results showed that N₂O cumulative emissions in no fertilization, nitrogen fertilization, and nitrogen fertilization plus straws incorporation under extreme precipitation increased by 310%, 440%, and 190% of those under light precipitation (10 mm), respectively. However, CO₂ cumulative emissions in no fertilization, nitrogen fertilization, and nitrogen fertilization plus straws incorporation increased by 27%, 1%, and −11%, respectively, compared to that under light precipitation. The surface CO₂ and N₂O fluxes followed basically CO₂ and N₂O concentrations dynamics in the soil, and there was a significant positive correlation between soil surface fluxes and belowground concentrations. Under extreme precipitation events, soil O₂ concentrations sharply decreased and progressively recovered to the initial level, and concomitantly, soil CO₂ and N₂O concentrations peaked, showing an opposite dynamic pattern. In addition, the timing of the three gases concentrations under extreme precipitation was delayed compared to that under light precipitation events. Soil O₂ concentrations were negatively correlated with CO₂ and N₂O concentrations. Soil CO₂ concentrations followed a logistic growth pattern with decreasing O₂ concentrations, and N₂O concentrations followed an exponential growth pattern with decreasing O₂ concentrations. Therefore, soil CO₂ and N₂O production and emissions are strongly related to soil O₂ concentration dynamics during extreme precipitation events. These results will help clarify the mechanism of greenhouse gases emissions from rainfed croplands in the Loess Plateau.

Effects of biochar on annual greenhouse gas emissions and freeze-thaw effects in saline soil

ZHANG Ruxin, QU Zhongyi, YANG Wei, LIU Zuting, WANG Qiyuan, WANG Liping

2022, 30(10): 1565-1576. doi: 10.12357/cjea.20220010

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Abstract:
Inner Mongolia is the main grain-producing region in China and is one of the regions subject to the most significant effects of climate warming. This study investigated the effects of biochar on annual greenhouse gas emissions and the freeze-thaw effect of saline soil in the Hetao Irrigation Area, Inner Mongolia. Three biochar addition treatments [biochar rate of 15 t∙hm⁻² (B15), 30 t∙hm⁻² (B30), and control without biochar application (CK)] were set up before the freeze–thaw period in 2019, and no biochar was applied thereafter. Soil CO₂, CH₄ and N₂O emission fluxes and physicochemical properties were measured in different treatments during the freeze–thaw period in the first year, sunflower growth period, and freeze–thaw period in the second year in the experiment. The results showed that biochar treatment increased soil pH, electrical conductivity, water content, temperature, and available P and K contents, and this effect persisted after two years of soil freezing-thawing. Soil CO₂ and N₂O emission fluxes were positively correlated with soil temperature and soil moisture during the entire experimental period. However, there was no significant correlation between CH₄ flux and soil temperature, moisture, conductivity, pH, or available P and K. The soil CO₂ flux in different sampling periods showed obvious seasonal variation, with a lower level in the freeze–thaw period and a higher level in the crop growing period. The overall variation pattern of CO₂flux was similar to that of temperature. The application of biochar significantly reduced the accumulated soil CO₂ emissions during the sunflower growing period, with B15 and B30 reducing CO₂ emissions by 9.86% and 14.37%, respectively, compared to CK, whereas there was no significant effect on CO₂ emissions during the freeze–thaw periods in the first and second years. Soils in the freeze–thaw period in the first year, sunflower growth period and freeze–thaw period in the second year were dominated by CH₄ uptake, where the intensity of CH₄ uptake by soils in the freeze–thaw periods was greater than that in the sunflower growth period. Biochar application reduced cumulative soil CH₄ emissions by 31.15%−55.59%, 18.75%−28.13% and 9.33%−25.36% in the three periods, respectively, and the reduction rate decreased gradually over time. N₂O emissions usually reach their peak when soil moisture is sufficient, and in this experiment, soil N₂O emissions were mainly concentrated in the melting and crop-growing stages. Compared with CK, biochar addition significantly reduced cumulative soil N₂O emissions in three periods, ranging from 42.86% to 54.76% in the freeze–thaw period in the first year, 14.08% to 26.76% in the sunflower growing period, and 24.07% to 59.26% in the freeze–thaw period in the second year. The global warming potential (GWP) was negative in both freeze–thaw periods, indicating that no warming effect was observed in the soil during the freeze–thaw period. The GWP value of biochar treatment was significantly lower than that of CK, and the order of warming potential was CK > B15 > B30. Compared to CK, the GWP values of B15 and B30 decreased by 15.74% and 30.19%, respectively. Compared with CK, B15 and B30 significantly increased the sunflower yield by 6.51% and 9.44%, respectively. Biochar applied to salinized soil underwent two rounds of the freeze–thaw could significantly inhibit N₂O emissions and promote CH₄ uptake without significantly reducing soil CO₂ emissions.

Sensitivity and uncertainty analysis of carbon footprint evaluation: A case study of rice-crayfish coculture in China

JIANG Rong, XU Qiang, LI Jingyong, DAI Linxiu, AO Dicai, DOU Zhi, GAO Hui

2022, 30(10): 1577-1587. doi: 10.12357/cjea.20220188

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Rice-crayfish coculture has recently been developed owing to its high economic benefits. In 2020, the area used for rice-crayfish coculture in China reached 1.26×10⁶hm². The objective and comprehensive evaluation of the carbon footprint of rice-crayfish coculture is crucial for low-carbon green development of the integrated farming industry of rice and aquaculture animals. Sensitivity and uncertainty analyses of carbon footprint can help to increase the robustness of the evaluation results and provide a reference to further optimize parameters and reduce the uncertainty of evaluation results in the future. Based on a field experiment and life cycle assessment (LCA), a comprehensive carbon footprint evaluation of rice monoculture and rice-crayfish coculture was carried out using 1 hm² (area), 1 ¥ (output value), and 1 NDU (nutrient density unit) as the functional units (FU). The results showed that the carbon footprint per hectare (CF_A) of rice monoculture and rice-crayfish coculture was 14 126 kg(CO₂-eq)·hm^–2 and 13 140 kg(CO₂-eq)·hm^–2, respectively; the latter was 7.0% lower than the former. Compared with rice monoculture, rice-crayfish coculture had higher economic output value and nutrition density delivery. Thus, the carbon footprint per output value [0.11 kg(CO₂-eq)·¥^–1] and carbon footprint per NDU [3.05 kg(CO₂-eq)·NDU^–1] of rice-crayfish coculture was 49.3%–81.4% lower than those of rice monoculture, whereas the net ecosystem economic budget (NEEB) of rice-crayfish coculture (85 745 ¥·hm^–2) was 511.5% higher than that of rice monoculture. Hotspot analysis showed that CH₄ emissions, electricity consumption, and feed input contributed greatly to carbon footprint, accounting for 59.8%, 13.8%, and 12.3%, respectively. The application of urea, compound fertilizer, and organic fertilizer contributed 4.7%, 3.8%, and 1.5% to carbon footprint, respectively; and N₂O emissions, diesel consumption, and rice seeds contributed even less (3.3%, 0.3%, and 0.4%, respectively). Sensitivity analysis showed that the carbon footprint was most sensitive to CH₄ emissions. When CH₄ emissions varied by ±40%, the carbon footprint varied between 9994 and 16 283 kg(CO₂-eq)·hm^–2. Carbon footprint was also sensitive to electricity consumption and feed input. When these two parameters were varied by ±40%, the carbon footprint varied from 12 413 to 13 864 kg(CO₂-eq)·hm^–2 and 12 491 to 13 787 kg(CO₂-eq)·hm^–2, respectively. Other parameters (i.e., diesel consumption, organic fertilizer, and rice seed inputs) had a weaker impact on the carbon footprint. The results of uncertainty analysis showed that the mean value of the carbon footprint of rice-crayfish coculture was 13 302±1166 kg(CO₂-eq)∙hm^–2, and the median and coefficient of variation were 13 250 kg(CO₂-eq)·hm^–2 and 8.76%, respectively, indicating a weak variation. Under 95% confidence interval, the CF_A of rice-crayfish coculture varied between 11 179 and 15 613 kg(CO₂-eq)·hm^–2. The results of this study highlighted the rich nutritional output function of rice-crayfish coculture and analyzed the urgency and necessity of transforming traditional agriculture to ecological agriculture from the perspective of improving the dietary structure of residents. The methods used in this study can provide technical support for a more comprehensive carbon footprint evaluation of agricultural production systems with multi-functional outputs.

Effects of multiple cropping systems based on spring maize on soil fungal communities in the North China Plain

CHEN Xingqiong, LI Jinna, GUO Yifan, CHEN Lin, XU Jie, SUI Peng, LIU Jin, GAO Wangsheng, CHEN Yuanquan

2022, 30(10): 1588-1600. doi: 10.12357/cjea.20220030

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Abstract:
To explore the impact of multiple spring maize cropping systems on soil quality in the North China Plain, we used DNA Illumina high-throughput sequencing to study fungal community diversity in the 0–20 cm topsoil layer of six cropping systems based on field experiments. The results showed that: 1) Compared with spring maize monocropping (MM, control), the multiple cropping systems [double-cropping systems of winter wheat-summer maize (MW), spinach-spring maize (MSp), rye-spring maize (MR), and relay intercropping systems of pea/spring maize (MP), and potato/spring maize (MPo)] increased the diversity of soil fungal communities (P<0.05), and the Shannon index by 12.18%, 12.17%, 10.37%, 11.69%, and 8.44%, respectively, compared with MM. However, there was no significant difference among all cropping systems for the soil fungal richness index. 2) The dominant phyla in these cropping systems were Ascomycota, Mortierellomycota, Basidiomycota, Chytridiomycota, and Rozellomycota; in particular, the relative abundance of Ascomycota was more than 80%. 3) Multiple cropping systems increased the number of beneficial fungi. The potentially beneficial communities at the genus level, such as Mortierella and Metarhizium, were relatively enriched in MR, MW, and MSp; and Metarhizium was particularly abundant in MSp. Pyrenochaetopsis was often considered to increase the disease risk in crops, and the order of relative abundance in the six cropping systems was as follows: MM>MW>MP>MR>MSp>MPo. 4) The FUNGuild function prediction results showed that the cropping systems changed the proportion of soil fungal nutrition types. The sprotroph (26.09%), pathotroph (22.48%), and pathotroph-sprotroph-symbiotroph (26.39%) were the main types in the MM; the sprotroph (29.99%) was the main type in the MW; and the sprotroph (21.11%−27.88%) and pathotrophs (23.74%−30.40%) accounted for a larger proportion in the remaining multiple cropping systems. 5) Correlation analysis showed that soil field water-holding capacity, soil organic matter, and bulk density were the main environmental factors affecting soil fungal community structure in this experiment. In summary, compared with spring maize monocropping, rotating or intercropping spring maize with other crops could significantly increase the diversity of soil fungal communities. Among the multiple systems, the rotation patterns of rye-spring maize, spinach-spring maize and winter wheat-summer maize had good performance in improving soil fungal diversity and enriching beneficial microbiota. In addition, the rotation systems of rye-spring maize and spinach-spring maize reduced the abundance of potentially pathogenic fungi to a certain extent. Therefore, combining the demands of water and land conservation, spring maize rotated with rye or spinach may be a better choice from the perspective of soil microorganisms in the North China Plain.

Response of spring wheat yield to snow cover in the black soil region: A perspective from the regulation of freezing and thawing processes of seasonally frozen soil

FU Wei, REN Jian, LI Yifan, WEI Xiaorong, YU Shuhui, HU Yongxiang, SHANG Guofei

2022, 30(10): 1601-1609. doi: 10.12357/cjea.20220006

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Seasonal snow and seasonally frozen soil are sensitive to climate change in middle-high latitude regions. Changes in seasonal snow associated with climate change could alter the freezing and thawing processes of seasonally frozen soil. Thus, these modifications may have important consequences on agricultural production by affecting the soil environment (e.g., moisture, temperature, and nutrients). However, the effects of seasonal snow on seasonally frozen soil and their association with food production remain unknown, especially in assessing the impacts of climate change on sustainable agricultural development and food security in the black soil region. This study was designed to explore how seasonally frozen soil regulates spring wheat yield in response to snow cover in an agroecosystem. To achieve this goal, we conducted a snow manipulation experiment in spring wheat fields, composed of snow cover treatment and snow free treatment. Immediately after each snowfall, we manually removed snow using shovels to maintain a snow-free condition in the snow free treatment plots, whereas snow was left undisturbed in the snow cover treatment plots. We measured spring wheat yield, soil temperature dynamics, and soil moisture dynamics in the 0−100 cm soil profile during the soil freezing and thawing periods. Soil freeze-thaw cycle frequency was determined by using soil temperature data. The results showed that spring wheat yield increased with soil moisture at a depth of 10 cm at the spring wheat sowing to seedling stage, and soil freeze-thaw cycle frequency at a depth of 10 cm during the soil thawing period. In contrast, the spring wheat yield decreased with soil moisture at a depth of 20 cm at the spring wheat seedling to four-leaf stage, and soil freeze-thaw cycle frequency at a depth of 10 cm during the soil freezing period. Furthermore, the soil moisture parameters (soil moisture at a depth of 10 cm at the spring wheat sowing to seedling stage and at a depth of 20 cm at the spring wheat seedling to four-leaf stage during the soil thawing period) and soil freeze-thaw cycle frequency parameters (soil freeze-thaw cycle frequency at a depth of 10 cm during the soil freezing/thawing period) explained 74.3%−77.6% and 77.8%−78.7% of the variance in the spring wheat yield in both the snow free and snow cover treatments, respectively. However, spring wheat yield was not related to soil temperature in the 0−100 cm soil profile, soil freezing duration, or soil thawing duration. Thus, the spring wheat yield was regulated by the above-mentioned soil moisture parameters and soil freeze-thaw cycle frequency parameters of seasonally frozen soil, and it did not respond to snow cover in the dry year. Therefore, the response of spring wheat yield in the dry year to snow cover was not significant in the black soil region. These results might provide insight into the potential role of seasonally frozen soil (development of soil freezing and thawing processes, soil temperature, and soil moisture regime) in regulating spring wheat yield in response to snow cover and improve the understanding of the relationship between seasonal snow-seasonally frozen soil and food production in the black soil region of Northeast China during climate change.

Effects of shading stress after heading on the accumulation and remobilization characteristics of non-structural carbohydrates in internodes of indica hybrid rice

ZHOU Xing, LI Bo, ZHU Youyun, LI Qiuping, HE Chenyan, YUAN Yujie, HUANG Xiaofan, HE Yuxin, WANG Li, CHENG Hong, REN Wanjun, DENG Fei

2022, 30(10): 1610-1619. doi: 10.12357/cjea.20220187

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Abstract:
This study was performed to investigate the dynamic changes of non-structural carbohydrate (NSC) content and accumulation, as well as the redistribution characteristics of NSC in different internodes of hybrid Indica rice. A field experiment with 53% shading treatment was conducted using the Indica rice hybrids ‘Yixiangyou 2115’ and ‘C Liangyouhuazhan’. The results showed that the NSC content in the lower internodes rapidly decreased after heading, which resulted in faster remobilization of stored NSC in the lower internodes. Meanwhile, the remobilization of the stored NSC in the upper internodes was slower than that in the lower internodes. In addition, some of the upper internodes continued to accumulate NSC after heading. Compared with the control, the shading treatment significantly decreased the NSC content in each internode of by 20.98% to 95.45% at the maturity stage (P<0.05), and increased the remobilization amount of stored NSC in each internode by 3.37% to 453.70%, as well as the remobilization rate and contribution rate of remobilized stored NSC in each internode by 3.25 to 325.07 and 0.63 to 9.18 percentage points, respectively. With the exception of neck internodes, the content and accumulation of NSC, as well as the remobilization amount and contribution rate of stored NSC in each internode was greater in ‘Yixiangyou 2115’ than in ‘C Liangyouhuazhan’. Compared to ‘C Liangyouhuazhan’, ‘Yixiangyou 2115’ exhibited lower reduction of both seed-setting rate and grain yield under shading stress, which was attributed to the greater NSC accumulation before heading and remobilization amount of stored NSC after heading in each internode. Correlation analysis indicated that the difference in grain yield between the control and shading treatments was significantly negatively correlated with the difference in NSC accumulation in the third and fifth internodes, but significantly positively correlated with the differences in remobilization amount of stored NSC and the remobilization rate within these internodes. In conclusion, rice could reduce the adverse effects of shading stress on grain yield by enhancing the remobilization of stored NSC in internodes (especially the third and fifth internodes) after heading. Therefore, the selection of rice varieties with high NSC accumulation before heading and high NSC remobilization after heading is helpful in relieving the harm caused by shading stress.

Effects of low iron stress on growth, antioxidant, and photosynthetic physiological characteristics of maize cultivar with contrast iron efficiency

FU Hao, REN Yun, CHEN Zexiong, NIE Shushu, YU Wenjing, LI Qiang

2022, 30(10): 1620-1629. doi: 10.12357/cjea.20220036

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When corn is deficient in iron, its leaves lose their green and yellow color, its growth is retarded, and heading ceases, resulting in reduced production. Previous studies on the response of corn genotypes to low iron stress have mostly focused on the differences in root morphology, absorption efficiency, and material production. Studies on the effects of low iron stress on the antioxidant and photosynthetic physiological characteristics of corn varieties with different iron efficiencies are not common. This study adopted different iron efficiency corn varieties as experimental material to analyze oxidation resistance and photosynthetic physiological characteristics of corn seedlings under low iron stress. The study aimed at to identify iron efficient mechanism of different corn varieties to lay the theoretical foundation and develop technical support for corn cultivation. Corn varieties with high iron efficiency (ZH 2; ZD 619) and iron low efficiency (CD 418; XY 508) were tested at three concentrations of pure iron (Fe0: 0 μmol∙L⁻¹; Fe10: 10 μmol∙L⁻¹; Fe100: 100 μmol∙L⁻¹), and the effects of low iron stress on seedling growth and antioxidant and photosynthetic physiological characteristics of corn varieties with different iron efficiencies were studied. The results showed that plant height, stem diameter, leaf area, net photosynthetic rate, stomatal conductance, transpiration rate, aboveground dry matter and iron accumulation and allocation ratio, dry matter weight per plant, and iron accumulation in corn seedlings decreased significantly under low iron stress, whereas the intercellular CO₂ concentration, peroxidase (POD) activity, contetns of malondialdehyde (MDA), soluble sugar, proline and soluble protein, root dry matter and iron accumulation ratio, root shoot ratio, and root shoot iron ratio were significantly increased. However, the morphological characteristics, photosynthetic characteristics, accumulation and distribution of dry matter and iron, and MDA content of iron-efficient varieties were lower than those of iron-inefficient varieties. The increase in osmotic regulation substances contents and POD activity was higher than that of iron-inefficient varieties, and the difference amplitude between the two varieties increased with the increase in stress. Correlation analysis showed that iron accumulation in corn seedlings was positively correlated with plant height, stem diameter, leaf area, and dry matter, and negatively correlated with the root-to-shoot ratio and root-to-shoot iron ratio, among which the correlation with dry matter (R²=0.9811) was the strongest. Comprehensive analysis showed that, compared with iron-inefficient varieties, iron efficient varieties under the stress of low iron have high osmotic regulation substances contents and antioxidant enzyme activity, which is beneficial for reducing membrane lipid peroxidation damage, maintaining high photosynthetic characteristics, accumulation and distribution of underground material and iron, and maintaining aboveground growth, so as to improve its adaptability to low iron environment.

Response of alfalfa nutritional quality to fall dormancy level and harvest time in the coastal alkali-saline region of Hebei Province

WANG Shichao, FANG Dong, LI Xiaolin, HAN Lipu

2022, 30(10): 1630-1637. doi: 10.12357/cjea.20210919

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Alfalfa (Medicago sativa L.) is an important forage crop with high protein content. Alfalfa cultivation is a predominant method for high-efficiency utilization of saline-alkali land and can help ensure feed grain security. Alfalfa productivity in coastal saline-alkali land is typically constrained by factors such as freshwater shortage and high salinity levels, leading to a decrease in the nutritional quality of alfalfa forage. Although alfalfa yield did not show a strong relationship with fall dormancy type in moderate climatic regions, nutritive quality could be correlated. Reasonable harvest management is integral to achieving a high forage quality in alfalfa. Therefore, the aim of the current study was to explore the effects of fall dormancy types, harvest times, and their interaction on forage quality in saline-alkali soils. A field experiment was conducted in the coastal saline-alkali region of Hebei Province. The treatments comprised five fall dormancy types with 40 alfalfa cultivars (extreme fall dormancy, fall dormancy, semi-fall dormancy, non-fall dormancy, and extreme non-fall dormancy) and six harvest times. We found that the following results: 1) The total annual yield of crude protein (CP) was significantly affected by fall dormancy type and harvest time (P<0.05). The highest total annual CP yield was obtained in the extreme fall dormancy treatment and was 14.5% higher than that in the semi-fall dormancy treatment. The CP yield of the fifth harvest differed significantly among different fall dormancy types, whereas the fall dormancy type had no obvious effects on the CP yield of crude protein at other harvest times. 2) The CP content initially increased and then decreased with increase in harvest time. Fall dormancy had a significant effect on CP content at the sixth harvest, when the highest value for CP content (21.5%) was observed in the extreme fall dormancy treatment and was higher than that in the non-fall dormancy treatment. 3) After the first harvest, the fall dormancy type had significant effects on neutral detergent fiber (NDF). The highest NDF was observed in the extreme fall dormancy type. Fall dormancy type had no significant effect on acid detergent fiber (ADF). 4) Relative forage value (RFV) differed significantly across fall dormancy types and harvest times. The highest RFV was observed at the fourth harvest. The RFV of the first harvest of the extreme non-fall dormancy (165.3) was higher than that of the extreme fall dormancy. Overall, we found that fall dormancy type and harvest time had significant effects on alfalfa nutritional quality in the coastal alkali-saline region, with these effects especially strong in the first and final harvests at low temperatures. Combining the CP yield and relative feeding value, alfalfa with higher fall dormancy levels is an important source of feed from the second to the fourth harvest in the coastal alkali-saline region. To achieve high-quality alfalfa yields in the coastal alkali-saline region of Hebei Province, the effects of fall dormancy type and harvest time on the nutritive quality of alfalfa must be considered.

Water-saving potential analysis of spring wheat in Altay based on AquaCrop model

REN Xiaohong, WANG Huixiao, LIU Changming, FAN Ling

2022, 30(10): 1638-1648. doi: 10.12357/cjea.20220031

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In 2017, the comprehensive irrigation quota of various crops in Altay was 955 mm, and the actual irrigation quota of spring wheat, the main food crop, was approximately 780 mm, which is far higher than the actual water demand of spring wheat. To improve water-use efficiency, the best irrigation quota for spring wheat was determined, and the relationship between crop yield and water consumption was established. The AquaCrop model was used as the research model, and the main parameters of the AquaCrop model were localized in northern Xinjiang. The annual rate and applicability of the AquaCrop model from 2005 to 2014 were evaluated based on standardized water production efficiency (WP*) and reference harvest index (HI₀). After determining the appropriate parameters, the meteorological data from 2015 to 2017 were used for verification. Two sowing dates of spring wheat variety ‘Xinchun 6’ on April 10 and April 20 were set in this study, and irrigation quotas of 400 mm, 350 mm, 300 mm, 250 mm, and 200 mm and irrigation cycles of 7 d and 10 d were set under each sowing date for a total of 20 scenarios. The spring wheat yield in the Altay region of Xinjiang was simulated, and the spring wheat yield and irrigation water use efficiency under different scenarios and influence of the irrigation quota and irrigation times were compared. The optimal irrigation strategy was selected, with high yield and water-use efficiency as the goal. Using the wheat planting area and irrigation quota in 2017 as reference values, the differences in wheat yield and total water-saving amount under different scenarios in 2017 and 2020 were compared to analyze the water-saving potential of wheat. The results are as follow: 1) WP*=18 g∙m⁻² and HI₀=48% were recommended as the yield module parameters in the Altay area. The parameters of the AquaCrop model are divided into two modules: crop growth and yield. The parameters of the crop growth module required field experiments; therefore, the parameters of the yield module were adjusted. WP*=18 g∙m⁻², HI₀=48% and WP*=19 g∙m⁻², HI₀=45% were selected as the yield module parameters, and the yield error ranges were −3.44% to 5.67% and −4.92% to 4.56%, respectively. WP*=18 g∙m⁻² and HI₀=48% had better applicability, and the evaluation indexes: root mean square error (RMSE), relative RMSE (RRMSE), residual coefficient (CRM), Willmott cossitancy (d), and Nash efficincy coefficient (E_NS) were 0.110, 0.023, 0.002, 0.956, and 0.935, respectively. Finally, meteorological data from 2015 to 2017 were used for validation, and the validated yield error results were −0.41%, −3.02%, and 3.34%, respectively, with small simulation errors. 2) Scenario S15 (sowing on April 20, irrigation quota of 300 mm, irrigation cycle of seven days) can be used as the recommended irrigation strategy. Through the simulation of spring wheat yield and calculation of irrigation water-use efficiency under different scenarios, it was found that the postponement of sowing date was beneficial to the accumulation of crop yield because the crop was less exposed to low-temperature stress at that time. The effect of irrigation cycle on spring wheat yield was the opposite under different planting dates and irrigation quotas. The spring wheat yield of S15 was 5.610 t∙hm⁻², and the irrigation water use efficiency was 1.870 kg∙m⁻³. 3) In 2017, scenario S15 saved 2.335×10⁸ m³ of water. Under irrigation quotas (400 mm, 350 mm, 300 mm, 250 mm and 200 mm), 1.849×10⁸ m³, 2.092×10⁸ m³, 2.335×10⁸ m³, 2.579×10⁸ m³, and 2.822×10⁸ m³ were saved in 2017. Under the recommended irrigation strategy, water savings of 2.407×10⁸ m³, 2.431×10⁸ m³, and 2.476×10⁸ m³ can be achieved in the future when the utilization coefficient of irrigation water is 0.570, 0.580 and 0.600, respectively; indicating a huge water-saving potential.

Residues and accumulation characteristics of plastic fragments and microplastics in farmland soil of Guanzhong Plain, Shaanxi

CHEN Ronglong, CHEN Yanhua, HUANG Shan, YU Yao, CHEN Ronghuan, XUE Sha, LIU Ying, YANG Xiaomei

2022, 30(10): 1649-1658. doi: 10.12357/cjea.20220137

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The application and extension of agricultural film-mulching technology has greatly promoted the development of agriculture in arid and semi-arid areas. However, soil pollution caused by agricultural film residues and their fragmentation have become a great challenge to the development of green agriculture and sustenance of ecological security. In this study, the topsoil (0−30 cm) of farmland from the Guanzhong Plain in Shaanxi Province planted with different crops was taken through field investigation, and samples were analyzed using advanced plastic fragments and microplastic extraction and microscopic scanning identification method to study the characteristics of plastic fragments and microplastics and accumulation in two case study areas: vegetable cultivation area in Caijiapo (S1) and greenhouse planting area in Yangling (S2). The results showed that plastic fragments were detected in all the soil samples, and the residue color was red, black, white, and blue in the vegetable planting area. In the greenhouse planting area, the residues from the culture cups were mainly black. The number of plastic fragments decreased significantly with increasing soil depth (P<0.05) and increasing area. Specifically, in the vegetable planting area, 37.8% of the fragments were in the 0.25−2 cm² group, followed by those in the 2−10 cm² and 10−25 cm² groups, and the lowest fragment group was >25 cm². In the greenhouse planting area, 67.5% of the debris was in the 0.25−2 cm² group, followed by that in the 2–10 cm² and 10–25 cm² groups, and large plastic residue (>25 cm²) was almost not detected. In the different soil layers, the content of plastic residues decreased significantly with increasing soil depth (P<0.05). Specifically, the content of residues in the 0−10 cm soil of S1 and S2 was 26.2 μg·g⁻¹ and 34.9 μg·g⁻¹, respectively, and the residual content in 20−30 cm soil layer was the lowest; it was 2.48 μg∙g⁻¹ in vegetable plot and 4.79 μg∙g⁻¹ in greenhouse nursery. However, the detection rate of microplastics in the vegetable growing area was 23.9%, with a maximum of 1.8×10³ particles·kg⁻¹ in the 0–10 cm soil layer of S1-2. In the greenhouse planting area, the detection rate of microplastics was 39.5%, with a maximum of 500 particles·kg⁻¹ in the 0–10 cm soil layer of S2-2. In conclusion, the long-term application of agricultural plastic film and plastic products in agriculture leads to an increase in plastic residues in farmland soil. Significant differences in plastic residue and microplastic accumulation were found in different soil layers, and they may be harmful to soil properties and crop growth, reducing soil fertility, declining crop yield, and causing other adverse consequences. Therefore, further studies are needed to understand the fragmentation process of plastic residues and the cumulative and migration risk of microplastics in soil to provide a survey-based dataset for comprehensive assessment of plastic pollution in the Guanzhong Plain.

ENSO events impacts on apple production in Shandong Ⅰ: A study of changes in apple climatic resources and yields under different scenarios

CUI Cheng, LIU Yuan, LIU Buchun, SUN Yankun, YANG Fan, ZHANG Xiaonan, QIU Meijuan

2022, 30(10): 1659-1674. doi: 10.12357/cjea.20210925

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Abstract:
El Niño-Southern Oscillation (ENSO) is one of the strongest ocean-air coupling systems in the world. Furthermore, ENSO events have a major impact on climate resources and agriculture in China. Shandong is one of the major apple-producing areas in China. The variation in apple yield is affected by local climate conditions, cultivated varieties, and management. Analyzing the influence of climate change on local apple yield under the influence of ENSO events is of great significance. Therefore, based on the daily meteorological observation data, county-level apple planting statistical data in Shandong Province, and worldwide ENSO data from 1991 to 2019, the spatio-temporal variation in climate resources in the apple growing period in Shandong Province under different ENSO types were analyzed, and the impact of climate resources on local apple yield was explored. The results showed that: 1) the apple planting area in Shandong Province first increased and then decreased, while the total yield and yield per unit area increased significantly from 1991 to 2019. The center of gravity of the apple planting area and total output moved from Weifang to the Jiaodong Peninsula, while the center of gravity of the yield per unit area moved from the center to the southwest in Weifang. 2) There was no significant correlation between the climate resources and ENSO events in different ENSO years. The spatial distribution of the apple growing period climate resources was not uniform for different ENSO years. The light resources decreased from north to south, while the heat resources increased from east to west. The precipitation decreased from south to north. Light and heat resources were superior in El Niño years, and precipitation resources were superior in La Niña years and neutral years. 3) There was a negative relationship between the climatic resources and meteorological yield per unit area in different ENSO years, which restricted the apple meteorological yield per unit area to some extent. The precipitation resources in El Niño and La Niña years were positively correlated with the apple meteorological yield per unit area, while the precipitation resources in neutral years were negatively correlated with the apple meteorological yield per unit area. Superior climatic resources have a positive effect on apple production. Excessive climatic resources can cause a certain degree of inhibition of apple yield. In the future, it is necessary to focus on high temperature, drought, and other related disasters during El Niño years, low temperature and flood disasters in La Niña years and neutral years to avoid the impact of meteorological disasters and ensure the healthy development of the local apple industry.

Effects of social capital and technology cognition on farmers’ adoption of conservation tillage in black soil areas

LI Wenhuan, WANG Guixia

2022, 30(10): 1675-1686. doi: 10.12357/cjea.20220032

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Abstract:
Black soil is an extremely precious natural resource that plays an important role in ensuring food security, promoting green agricultural development and rural revitalization. However, in the case of overutilization, the quality of black soil deteriorates. Improvement of the adoption rate of conservation tillage by farmers and the growth of the black soil layer from “thin” to “fat” is an urgent issue that needs to be addressed. Previous studies have focused on the impact of economic and policy factors on farmers’ adoption of conservation tillage in black soil areas and pay less attention to the role of social capital embedded in rural areas. Based on the theory of embedded social structure and survey data of 625 farmers in typical black soil areas of Jilin and Heilongjiang Provinces, this study analyzed the transmission path and group differences of social capital and technology cognition on farmers’ adoption behavior of conservation tillage in black soil areas by using a structural equation model (SEM). The results showed that 1) social capital had a positive effect on farmers’ adoption of conservation tillage, in which social networks, social trust, and social norms promoted farmers’ adoption of conservation tillage. 2) Technology cognition played a positive role in promoting farmers’ adoption of conservation tillage. Technology cognition played an intermediary role in the impact of social capital on farmers’ adoption of conservation tillage. The indirect impact of technology usefulness cognition was greater than that of technology usability awareness because farmers more concerned about whether the technology can bring benefits to themselves than whether the technology is easy to master. 3) Multi-group SEM results showed differences in the influence of planting scale and age on farmers’ adoption behavior of conservation tillage technology in terms of social capital and technology cognition. The technology adoption behavior of large-scale growers was more easily affected by social networks, whereas small- and medium-sized farmers were more affected by social trust. Young and middle-aged adults were more likely to be affected by social networks, whereas older adults were more likely to be affected by technology usability. In view of this, in addition to relying on the government, the promotion of conservation tillage technology in northeast black soil areas should give full play to the role of social capital considering the heterogeneity of farmers.

The influencing factors and income effects of green prevention-control technology adoption — An empirical analysis based on the survey data of 792 vegetable growers

TIAN Lu, ZHENG Shaofeng, CHEN Rujing

2022, 30(10): 1687-1697. doi: 10.12357/cjea.20220038

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Abstract:
To comply with the agricultural production trend of protecting the ecological environment, reducing the application of chemical pesticides, comprehensively developing green agriculture, and helping the rural areas to achieve long-term development, the Chinese government made efforts to promote the application of green prevention-control technology; however, the application level of this technology in China is not high and existing research on the adoption of green prevention-control technology as a method selection by farmers is insufficient. To promote the adoption of green prevention-control technologies by vegetable farmers, achieve green production and quality improvement and income increase, provide policy reference for the effective promotion of green prevention-control technologies in the vegetable planting industry, and enrich the promotion theory of green prevention-control technologies, this study used vegetable growers in Shouguang City, Shandong Province as an example to quantitatively analyze the influencing factors and income effects of vegetable farmers’ adoption of green prevention-control technologies. Based on the micro-data of 792 vegetable farmers, this study characterized the behavior of vegetable farmers in adopting green prevention-control technology according to two aspects, adoption decision and adoption degree, explored the influencing factors affecting the adoption of green prevention-control technology of vegetable farmers using the Heckman correction method model. And the average treatment effect of the adoption of green prevention-control technology of vegetable farmers on their income was analyzed by using an endogenous conversion regression model. The study found that the degree of adoption of green prevention-control technologies by vegetable farmers was insufficient. The numbers of vegetable farmers adopting one and two green prevention-control technologies were the largest, which were 292 households and 216 households, respectively, accounting for 36.87% and 27.27% of the total sample, respectively. The level of awareness of green prevention-control technology of vegetable farmers, the experience of getting quality testing and training, and the active use of the internet in collection of information were significantly positively correlated with the adoption of green prevention-control technologies by vegetable farmers. Factors such as the number of plots owned, the number of information devices significantly negatively correlated with the adoption of green prevention and control technologies among vegetable farmers. Vegetable farmers whose per capita income exceeded the average sample level were more willing to accept green prevention-control technology, and the use of this technology could increase the proportion of the average annual income of vegetable farmers by 7.2%. Therefore, a variety of factors, such as family, information, and government policies, affect the decision-making and adoption degree of green prevention-control technologies by vegetable farmers; moreover, the adoption of green prevention-control technologies has a positive impact on the income of vegetable farmers. Based on this, we should give full play to the increase in the income effect of green prevention-control technology, stimulate the endogenous motivation of vegetable farmers to adopt new technologies, and propose that the government should accelerate the improvement of the promotion mechanism of green prevention-control technology, improve the risk compensation mechanism, give vegetable farmers science and technology policy subsidies, enhance the scientific and technological awareness of vegetable farmers, and actively promote the moderate-scale operation of farmers.

Research progress and prospects of ecotourism

ZHU Chunyu, CAO Jiansheng

2022, 30(10): 1698-1708. doi: 10.12357/cjea.20210900

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Abstract:
Ecotourism is a type of ecological project and tourism activity which has attracted increasing attention from scholars because of rising interest in sustainable development in the world since the 1980s. This paper reviewed the progress and problems in ecotourism research over the past 40 years from concept, stakeholder, environmental impact, and management perspectives. It found that: 1) the concept of ecotourism was constantly developing with the socioeconomic environment and the ecotourism industry; their common characteristics include taking nature and associated humanistic ecosystems as the object, responsible tourism, and the dual attributes of ecological and economic benefits. 2) The stakeholders of ecotourism may be considered as core layer, close layer, or loose layer members. The conflicts between the demands of the different core layers, such as the government, tourism enterprises, tourists, and community residents, constituted the main issues for ecotourism. Researchers should try to resolve this conflict by exploring the appropriateness of relationships and mechanisms of profit allocation for stakeholders. 3) The effect of ecotourism on the environment caused damage and destruction on a small scale, while protecting the landscape on a large scale by providing support for wildlife, reducing the resource needs of local residents, and improving the public’s environmental awareness. 4) Ecotourism management was composed of scenic spot planning, tourist management, environmental education, and community participation. Some new technologies and concepts such as 3S technology, “Internet +” and Tourist Cognitive Management were gradually being applied in the development of the ecotourism management. On this basis, we put forward some suggestions for future research on ecotourism trends, combined with the practical needs of Chinese ecotourism in the new era. We hope that this study can provide a reference for the practice and research of ecotourism.

2022 Vol. 30, No. 10