中国生态农业学报(中英文)

Ecological mechanisms and guiding principles of mixed cropping of crop varieties

HOU Saisai, WANG Lei, XU Huasen, WANG Hong, WANG Xinxin

2023, 31(1): 1-10. doi: 10.12357/cjea.20220508

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Abstract:
With the development of social economy and the continuous increase in population, the agricultural planting structure in China has gradually simplified, and the biodiversity of the agricultural system has drastically reduced. Agricultural development faces the challenges of ensuring food security and sustainable development. In this article, we reviewed the ecological mechanism of mixed cropping of varieties of crops in ecology and agronomy researches from perspectives of complementary effect, selection effect, resistance to pathogens, mycorrhizal symbiosis, and plant-soil feedback effect; and described the potential risks, which are affected by variety, environment, and management aspects. Studies on mixed cropping of crops varieties in natural and agricultural systems have shown that biological and genetic diversity is usually beneficial to ecosystem function. Mixed cropping of varieties improves biodiversity, which is of great significance for improving crop productivity and reducing pests and diseases. We summarized the screening principles and basis of functional trait evaluation of mixed cropping of crops varieties. The selection of varieties should be based on functional traits and goal-oriented and actual production needs, and the performance of varieties should be comprehensively evaluated by yield, yield stability, and stress resistance.

Effects of different types of villages on the distribution of arable land near-surface arthropods

BIAN Zhenxing, LIU Yao, WANG Chuqiao, SUN Zhiquan, YU Miao

2023, 31(1): 11-20. doi: 10.12357/cjea.20220286

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In agricultural landscapes, villages are mostly distributed in or around cultivated land, which is a special non-arable habitat; however, its role in arable land biodiversity is unclear. In this study, three villages (containing high, medium, and low proportions of semi-natural habitats) in the south of Changtu County, Liaoning Province were selected, and the distribution of near-surface arthropods in adjacent farmlands at different distances from the villages was investigated by using the trap method. The effects of village type and distance gradient on the whole and different functional groups of arable land near-surface arthropod communities were investigated by analysis of variance and sparse extrapolation curves. The results showed that 1) the number of plant-eating species in the adjacent cultivated land of the village was the largest, accounting for 75.34% of the total number, which was the main trophic group of the near-surface arthropods in the study field, followed by predatory species, accounting for 17.94% of the total population. 2) The diversity and dominance of near-surface arthropods in the farmland adjacent to the village showed a decreasing trend from the edge to the inside of the cultivated land. The higher proportion of semi-natural habitats made village a source of near-surface arthropod migration. 3) Villages increased the abundance of predators in arable land as well as the activity density of plant-eating species, while villages with a higher proportion of semi-natural habitats promoted the spread of more predators to farmland and further curb pest outbreaks. In summary, whether semi-natural habitats remain or are re-established within a village as a special type of non-arable habitat and their proportion have key impact on the biodiversity of adjacent arable land. Increasing the area of semi-natural habitats within the village by planting flowers or hedges on idle homesteads can provide habitat and refuge for predators, and increase the biological control effect of farmland in the event of pest outbreaks.

Research progress on regulation of root nodule formation and development of legume by light signals and photosynthetic products

LI Yiling, CHEN Ping, FU Zhidan, LUO Kai, DU Qing, GAO Chao, REN Junbo, YANG Xueli, LIU Shanshan, YANG Lida, YUAN Xiaoting, PENG Xinyue, YONG Taiwen, YANG Wenyu

2023, 31(1): 21-30. doi: 10.12357/cjea.20220415

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Legumes coexist with rhizobia to form nodules to meet plant nitrogen requirements through symbiotic nitrogen fixation. Legume nitrogen fixation capacity is of great significance to reduce nitrogen fertilizer consumption and potential environmental pollution and achieve sustainable development of agricultural production. The symbiotic nitrogen fixation of legumes consumes a large amount of energy; therefore, the energy supply of plants regulates the process of symbiosis and nitrogen fixation. This study reviews the recent research progress on the control of root nodule formation and development by light through plant photomorphogenesis and photosynthesis. Plant leaves sense blue light signals through blue light receptors (CRY1b) and produce light receptor-dependent transcription factors (STFs/FTs) to move from ground to ground. In addition, they integrate root hair development and the rhizobia-induced symbiotic signal (NIN) pathway to form root nodules. The movement and attachment ability of rhizobia in the environment are stimulated by light. In the symbiosis between plants and rhizobia, plants exchange photosynthetic products to produce NH₄⁺, which is assimilated by rhizobia. In addition, photosynthetic products (sucrose) are transported to root nodules through the phloem for a long distance and are metabolized into organic acids through glycolysis and other pathways in root nodules, providing a carbon skeleton, energy, and reductant for nitrogen fixation of rhizobia. The intermediate metabolites of photosynthates, such as glucose, glucose-6-phosphate, and trehalose 6-phosphate, combine with the regulatory proteins of glucose signal metabolism proteins TOR and SnRK1 to initiate the complex growth and development pathway of nodule cortex cells. Under low-nitrogen conditions, photosynthates are also secreted into the rhizosphere in the form of flavonoids and organic acids, recruiting rhizobia to form symbiotic relationships with plants.

Effects of leaf trichome and stomata on PAHs uptake in the leaf of winter wheat

WANG Jinfeng, LI Jia, CAI Jun, WU Fuyong

2023, 31(1): 31-39. doi: 10.12357/cjea.20220314

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To explore the effects of leaf structure on polycyclic aromatic hydrocarbon (PAHs) uptake in winter wheat, an indoor-simulated atmospheric exposure experiment was conducted. The characteristics of trichomes and stomata of leaves of seven winter wheat varieties were compared, and the relationship between leaf structure and PAHs of leaves in winter wheat was analyzed. The results showed that trichome density and length on the leaf abaxial side were larger than those on the adaxial side, while the opposite was true for stomatal density and area for most varieties of winter wheat. Among all wheat varieties, the largest trichome density and length on the leaf abaxial and adaxial side were found in ‘Zhongmai 175’, while the lowest trichome density on the leaf adaxial side was recorded in ‘Changwu 521’. The stomatal density on the leaf adaxial side of ‘Zhongmai 175’ was significantly (P<0.05) higher than that of ‘Cangmai 6005’ ‘Changwu 521’ and ‘Xiaoyan 22’, and the stomatal area on the leaf adaxial side of ‘Changwu 521’ ‘Xiaoyan 22’ and ‘Zhengmai 7698’ were significantly higher than that of ‘Jiaomai 266’. The concentration of Σ₅PAHs in the leaf of ‘Changwu521’ were significantly lower than those of the other six varieties, which may be related to the smaller trichome and stomatal density and shorter trichome in the leaf. At an exposure concentration of 6.00 mg∙L^–1 Σ₅PAHs, PAH concentrations in the leaves decreased with increasing molecular weight of PAHs. In addition, trichome density and length on the leaf adaxial side and phenanthrene (PHE) and Σ₅PAHs concentration showed a significant positive correlation. This result may be due to the higher volatility and lower molecular weight of PHE, which are easily attached to the leaf surface and then absorbed and enriched by leaves. There was a significant correlation between stomatal density on the leaf adaxial side and PHE (P<0.05) and Σ₅PAHs (P<0.05) concentrations, indicating that the denser the stomatal distribution on the leaf adaxial side, the stronger the uptake capacity of PHE. PCA results further confirmed that leaf trichome density was the main limiting factor for PAHs accumulation in leaves. Therefore, selecting winter wheat varieties with a sparse leaf trichome distribution can reduce the human risk of PAHs in winter wheat in polluted areas.

Effects of seed orientation planting on root growth in summer maize

DUAN Shiming, GU Huijie, LI Baoru, JIANG Hanbing, ZHANG Xiying, LIU Xiuwei

2023, 31(1): 40-53. doi: 10.12357/cjea.20220300

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Seed orientation during planting significantly affects crop shoot growth; however, its effect on the root system remains unclear. To explore the effects of seed orientation on above- and below-ground growth, this study used cultivar of summer maize ( Zea mays L., Zhengdan 958) to conduct germination paper, soil pot, and field experiments, from 2020 to 2021. The experiments included two irrigation treatments (irrigation, and non-irrigation or drought) and four seed orientation plantings (tip pointed up, T-U; tip pointed down, T-D; embryo lying up, E-U; and embryo lying down, E-D). The root mass density, root length density, specific root length, soil water content, shoot biomass, and yield of maize were analyzed. The results showed that under irrigation treatment, the root systems of plants in the E-U group were the biggest (5% higher in deep root mass density and average root mass density, 48% higher in deep root length density, and 10% higher in average root length density); thus, the soil water consumption was increased by 18%, from bell-mouthed to grain-filling. Additionally, plants in the E-U group had a wider leaf growth azimuth (35%), larger leaf area index (7%), and higher shoot biomass (3%); therefore, the grain yield was also higher (8%). Our correlation analysis showed that grain yield was directly correlated with shoot biomass, ear number, and harvest index; and indirectly correlated with deep root mass density. Under drought conditions, the maize roots under normal T-D treatment had a faster growth rate (36%) and narrower root angle (43%), resulting in the highest root mass density in the deep soil layer (19%), as well as higher soil water consumption (5%); as a result, plants also had higher shoot biomass (6%), even with a narrower leaf growth azimuth. In conclusion, under adequate water conditions, the distribution of the aboveground parts and root system together contributed to the increased grain yield under E-U treatment. Under drought conditions, dry matter production under the normal T-D treatment was mainly affected by root distribution. In the future, adjusting seed orientation when planting may facilitate a further increase in shoot biomass accumulation and yield formation by coinciding with root and shoot development under drought stress.

Effects of sowing date on yield performance and safe sowing date window of mechanically grain-harvested spring maize

RONG Meiren, GAO Julin, WANG Fugui, WANG Zhen, YU Xiaofang, SUN Jiying, HU Shuping, WANG Zhigang

2023, 31(1): 54-66. doi: 10.12357/cjea.20220202

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The selection and promotion of mechanically grain-harvested maize varieties pose new challenges to the full utilization of heat in northern spring maize regions. Under the background of climate warming, exploration of the potential of advancing the sowing date can provide a basis for making full use of regional heat resources and obtaining sufficient dehydration time for mechanically grain-harvested maize. In this study, suitable local grain-harvesting maize varieties were used as test materials. Experiments were carried out in six ecological regions of Inner Mongolia, which are the east region of Xing’an Mountain (EXM), south region of Xing’an Mountain (SXM), west Liao River Plain (WLR), north region of Yanshan Mountain (NYM), Tumote Plain (TMP), and Hetao Plain (HTP). The results showed that in the spring maize areas of six ecological regions of Inner Mongolia, maize was sown six to eight days ahead of the conventional sowing date for mechanical grain-harvesting, and the maize yield could be increased by 7.5%–18.4% under the optimal sowing date. The suitable sowing date window of each ecological region was different: EXM from May 4 to 11, SXM from April 27 to May 10, WLR from April 15 to 30, NYM from April 9 to 26, TMP from April 9 to 29, and HTP from April 3 to 22. With an increase in latitude, this period gradually became “narrower”. For every 1° increase in latitude, the average window period was shortened by 1.8 d, and the average advance of the sowing date was reduced by 2.8 d. The sowing date had no significant effect on the corn harvest index. At the “source” end, the development of pre-anthesis leaf area index, pre-anthesis photosynthetic potential of the mechanically grain-harvested maize population were promoted, which significantly increased the population biomass. At the “sink” end, the population sink activity and yield per plant were improved by increasing grains number per ear and 1000-grain weight. In Inner Mongolia, the yield of spring maize mechanically grain-harvested in the security window for suitable early sowing was increased by 10.4% through ascension of “source” development pre-silking, extension of the persistent period of leaf area, optimization of “sink” activities, improvement of the yield per plant and full use of the heat resource condition. Meantime, the mature seed dehydration occurred at an effective accumulated temperature of 43.7 ℃ to 130.9 ℃. This is beneficial for increasing yield and harvest quality of mechanically grain-harvested maize.

Effects of Medicago sativa cultivation on soil denitrifying bacterial community in the Loess Plateau

SUN Pengzhou, LUO Zhuzhu, LI Lingling, NIU Yining, WANG Xiaofei, TIAN Jianxia, LIU Jiahe

2023, 31(1): 67-78. doi: 10.12357/cjea.20220250

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Microorganisms with nitrite reductase genes can reduce nitrite to nitric oxide (NO), which is an important influence in the biological nitrogen cycle. A field study was conducted to investigate soil denitrifying bacteria (nirK- and nirS-type) communities and diversity in a farmland (Zea mays field) and Medicago sativa land established based on different times (2, 9, and 18 years, respectively expressed as L₂₀₁₉, L₂₀₁₂ and L₂₀₀₃). Illumina MiSeq high-throughput sequencing and real-time fluorescent quantitative PCR technology were used to investigate the structure and diversity of denitrifying bacterial communities under four treatments (Farmland, L₂₀₀₃, L₂₀₁₂ and L₂₀₁₉). Redundancy analysis and molecular ecological network analysis were used to evaluate the relationship between soil physical and chemical properties and denitrifying bacterial community. The results indicated that the abundance of nirK gene was significantly higher than that of nirS gene. The abundance of nirK gene varied from 4.91×10⁷ to 6.33×10⁷ copies∙g⁻¹, whereas the abundance of nirS gene varied from 1.02×10⁷ to 1.86×10⁷ copies∙g⁻¹. The years of M. sativa cultivation did not affect the diversity of nirK- and nirS-type denitrifying bacteria. Proteobacteria had the highest abundance in the denitrifying bacterial community. The dominant genera of the nirK-type denitrifying bacteria were Paracoccus (1.10%–39.94%), Achromobacter (0.07%–12.50%), and Sinorhizobium (0.50%–7.60%). The relative abundance of Paracoccus in M. sativa soil was significantly higher than that in maize soil (P<0.05), and the relative abundance gradually increased with increasing age of M. sativa stands. The relative abundance of Achromobacter in M. sativa soil was significantly lower than that in maize soil (P<0.05), and the abundance decreased gradually with increasing age of the M. sativa stand. The dominant genus of nirS-type denitrifying bacteria was Rhodobacter (1.42%–5.20%). There was no significant difference in Rhodobacter abundance between the maize fields and M. sativa fields. Correlation analysis showed that the abundance of nirK-type denitrifying bacteria had no significant response to soil environmental factors, but the abundance of nirS-type denitrifying bacteria had a significant positive correlation with soil organic carbon (r=0.762), total nitrogen (r=0.776), and microbial biomass carbon (r=0.622) and a significant negative correlation with soil water (r=–0.678) and available phosphorus (r=–0.628). RDA analysis indicated that soil water (P=0.002) and organic carbon (P=0.020) were the main environmental factors affecting the community structure of nirK-type denitrifying bacteria, and soil available phosphorus (P=0.006) was the main environmental factor affecting the community structure of nirS-type denitrifying bacteria. The proportion of positively correlated edges in the nirK-type denitrifying bacterial ecological network was 98.37%, and the proportion of negatively correlated edges was 1.63%; however, all edges in the nirS-type denitrifying bacterial ecological network were positively correlated. This indicated that the relationship between bacterial communities of both types of denitrifying bacterial was mainly synergistic. In summary, long-term planting of M. sativa significantly affected the composition of soil denitrifying bacterial community. Our results provide a scientific basis for further studies on the microbial mechanism of denitrification in the Loess Plateau after years of M. sativa planting.

Effects of elevated CO₂ and warming on soil enzyme activity and temperature sensitivity of millet

LIANG Meng, LU Bingbing, WU Yang, WANG Xuesong, ZHENG Fenli, LIU Guobin, XUE Sha

2023, 31(1): 79-89. doi: 10.12357/cjea.20220344

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Study on the response of soil enzyme activity and temperature sensitivity to elevated CO₂ concentration and warming at important growth stages of crops is of great significance to evaluate the impact of climate change on crop production and the functional stability of soil ecosystem. In view of this, the soil of millet (Setaria italica) at grain filling stage was selected as the research object for pot experiments, and three climate scenarios were designed using an artificial climate chamber as follows: elevated CO₂ concentration (700 μmol∙mol⁻¹ CO₂ concentration and 22 ℃ ambient temperature, EC), elevated CO₂ concentration and warming (700 μmol·mol⁻¹ CO₂ concentration and 26 ℃ ambient temperature, EC+T), and control (400 μmol·mol⁻¹ CO₂ concentration and 22 ℃ ambient temperature, CK). Two water conditions were set for each climate scenario as follows: adequate water supply (70% field capacity) and mild drought stress (50% field capacity). The responses of the activities and temperature sensitivity of β-glucosidase (βG), β-N-acetyl glucosidase (NAG), cellulase (CBH), and β-xylosidase (βX) to elevated CO₂ concentration and warming were analyzed. The results showed that the activities of βG, NAG, CBH, and βX in the control group (CK) first increased and then decreased with an increase in incubation temperature under the condition of sufficient water supply, and the temperature at which enzyme activities were the highest was 25 ℃. At the optimum temperature (25 ℃), elevated CO₂ concentration significantly decreased soil βG activity but had little inhibitory effect on the activities of soil NAG, CBH, and βX. The effect of the interaction between elevated CO₂ concentration and warming was related to water conditions; specifically, the enzyme activities were inhibited under mild drought condition but no significant difference was observed under adequate water supply. In addition, elevated CO₂ concentrations and warming significantly affected the temperature sensitivity (Q₁₀) of soil enzyme activity at millet grain filling stage. The elevated CO₂ concentration significantly increased Q₁₀, whereas warming decreased Q₁₀. Under sufficient water supply, warming counteracted the effect of elevated CO₂ concentration on Q₁₀, and the interaction between elevated CO₂ concentration and warming had no significant effect on Q₁₀. However, elevated CO₂ concentration and warming had significant effects on Q₁₀ under mild drought condition as follows: the interaction of CO₂ concentration, temperature, and water content on Q₁₀ was significant. In addition, the interaction between elevated CO₂ concentration and mild drought had a significant effect on Q₁₀, but there was no significant difference in the effect of elevated CO₂ concentration and the interaction of the three factors. Moreover, redundancy analysis showed that Q₁₀ was affected by environmental variables such as microbial biomass and soil nutrients. This study demonstrated that the effects of elevated CO₂ concentration, warming, drought, and their interactions on soil enzyme activities and temperature sensitivity were complex and particularly, the elevated CO₂ concentration inhibited the temperature sensitivity of soil enzymes and weakened the metabolic functions and stability of enzymes related to soil carbon and nitrogen cycling, which further affected the functional stability of the soil ecosystem.

Economic and ecological sustainability assessments of single mid-season rice systems under different planting modes in hilly areas

TANG Rongli, TANG Xinglong, ZHANG Wujun, DUAN Xiujian, LI Jingyong, YAO Xiong

2023, 31(1): 90-101. doi: 10.12357/cjea.20220367

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An improvement in rice planting mode is important to reduce costs and increase production efficiency and grain income in hilly areas. Compared with artificial planting mode, machine-transplanted seedlings and direct seeding modes are more efficient, and they improve the economic benefit of rice production. However, their high material and energy requirements impose pressure on the ecosystem to a certain extent. Therefore, an evaluation of the sustainability of different rice planting modes in hilly and mountainous areas from a comprehensive cost-benefit and ecological economic perspective is of great significance for green and high-quality development of the rice industry. In this study, different planting modes of single mid-season rice in Yongchuan District of Chongqing City, which is an advanced county for national grain production in China, were evaluated. Cost-benefit and emergy analyses were conducted to compare the main production processes, net benefits, emergy structure, and investment in artificial planting mode, mechanical transplanted seedling mode, and direct seeding mode; and their ecological sustainability was quantitatively evaluated based on agro-environmental, emergy economic, and sustainability indexes. The results showed that there were differences among three planting modes in their main production processes, material and labor inputs, yield, and economic output. The direct seeding mode had the highest rice yield, followed by the mechanical transplanting seedling mode, and then the artificial planting mode. From the cost-benefit perspective, the benefits of the three planting modes were low or even at a loss and their economic sustainability was weak. In terms of cost composition, the cost of materials and services was the highest, accounting for 37.92%–48.52% of the total cost. The second highest was land rent, accounting for 35.78%–42.63% of the total cost. Labor inputs accounted for 9.09%–26.30% of the total cost, and this variation was an important factor affecting the profitability of mid-season rice production when different planting modes were used. Emergy structure analysis showed that the renewable resource input and non-renewable environmental resources of the three rice planting modes were the same, whereas the supplemental emergy input was different and in the following order: machine-transplanted seedling mode > artificial planting mode > direct seeding mode. Industry supplemental emergy input was the main input form, of which fertilizer input and rice drying emergy consumption were the main components, accounting for 49.00%–56.54% and 27.32%–32.74% of industrial supplemental emergy, respectively. To improve the sustainability of different rice planting modes, methods for efficient fertilizer utilization and rice drying emergy reduction should be further explored. The results of the agro-environmental indexes showed that the pressure on the agro-ecological environment by the three planting modes was low. The results of the emergy economic indexes showed that the emergy investment-to-yield ratio of the direct seeding mode was better than that of the other two modes. Emergy sustainability index indicated that the three types of rice systems mainly depended on the input of environmental resources and were natural resource-driven eco-economic systems. Overall, the direct seeding mode had the greatest economic and ecological advantages, and can be further promoted and applied in hilly areas. Planting mode improvement methods should be fully explored to maintain healthy development of regional rice production. Planting mode improvements are important measures for reducing investment costs and increasing production efficiency and grain income in hilly areas.

Sensitivity analysis and calibration of the APSIM next-generation model under different irrigation and sowing density in wheat

ZHANG Meng, GAO Yanmei, ZHANG Yongqing

2023, 31(1): 102-112. doi: 10.12357/cjea.20220384

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The Agricultural Production Systems Simulator (APSIM) is currently one of the most widely-used crop and farming system models globally. With increasing challenges and demand for agricultural modeling, the APSIM Initiative is building the next generation of APSIM to improve its prediction accuracy and increase its applicability to a wider range of farming systems. The APSIM next-generation (APSIM NG) model implemented new phenology- and morphology-simulating mechanisms, introduced additional parameters, and allowed modelers to add custom parameters. These parameters cannot be directly measured and must be calibrated when the APSIM NG model is applied to a new environment and cultivar. Determining the relative importance of the parameters to the specific outputs can streamline the calibration of crop models for new cultivars, and a sensitivity analysis can quantify the influence of model input parameters on model outputs. In this study, we used the Extended Fourier Amplitude Sensitivity Test to perform a sensitivity analysis on the wheat module of the APSIM NG for the first time. We also calculated the main and total effect sensitivity indices of three outputs — yield, flowering day, and maturity day — to crop parameters under different irrigation and plant density treatments. We found that days to anthesis and physiological maturity were mostly sensitive to the parameters that determine the length of the reproductive stages (phyllochron, number of leaves the plant will produce when fully vernalized early and grown in long photoperiod, and photoperiod sensitivity), and yield was most sensitive to the cultivar parameters that determine the yield component (GrainsPerGramOfStem, MaximumPotentialGrainSize) and phyllochron. Irrigation and sowing density treatments affected the main effect and total effect sensitivity index of parameters to yield; however, it did not affect the order of parameters. Next, we calibrated the model against data from 2015 to 2018 from the Wuqiao Experimental Station of the China Agricultural University in Hebei Province. The data comprise four irrigation and plant density treatments. The calibrated APSIM NG model captured the Zadoks decimal growth scale and yield with acceptable accuracy. Across the treatments, the APSIM NG explained more than 98% of the variation in the growth scale. The root-mean-square error (RMSE) of the yield was 508 kg∙hm⁻², compared with the experimental data. This study provides guidelines for APSIM NG model calibration in the North China Plain, as well as guidance to simplify the APSIM NG model and improve its precision, especially when many parameters are used. For robust phenology and yield prediction with APSIM NG, more research on the environment, genotype, and management factors is suggested.

Spatial correlation characteristics and mechanism of cultivated land landscape pattern and cultivated land quality in different geomorphic areas of Liaoning Province

QIAN Fengkui, PANG Ranran, YU Yang, XU Huan, HAN Chunlan

2023, 31(1): 113-124. doi: 10.12357/cjea.20220392

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Exploring the relationship between the landscape pattern and quality of cultivated land plays an important supporting role in the protection of cultivated land by trinity. Existing research lacks an analysis of the mechanism of cultivated land landscape pattern indexes on cultivated land quality, which restricts the development of cultivated land quality improvement from the perspective of cultivated land landscape patterns. Therefore, this study used the central plain, eastern mountainous area, and western hilly area of Liaoning Province as the research objects, and used the spatial autocorrelation analysis method to explore the correlation characteristics between the landscape pattern indexes of cultivated land and the quality of cultivated land in different geomorphic areas. The spatial error model was used to analyze the specific effects of each cultivated land landscape pattern index on the quality of cultivated land in different geomorphic areas. Research results showed that 1) the comprehensive index of cultivated land landscape pattern and the quality of cultivated land in different geomorphic areas generally showed comprehensive characteristics of ‘better’ in the central plain area and ‘worse’ in the western hilly and eastern mountain areas. 2) There was a positive correlation between the comprehensive index of cultivated land landscape pattern and the quality of cultivated land in different geomorphic areas, with the correlation coefficients of 0.45 in the eastern mountain area, 0.24 in the central plain area, and 0.17 in the western hilly area. 3) The influence mechanism of the cultivated land landscape pattern indexes on cultivated land quality differed in different geomorphic areas. Among them, the maximum patch index had a significant impact on the improvement of cultivated land quality in different geomorphic areas. The landscape shape index, the average patch size, and the aggregation index had a relatively large impact on the improvement of cultivated land quality in the central plain, eastern mountain, and western hilly areas, respectively. The research results revealed that there were different degrees of positive correlations between the cultivated land landscape pattern indexes and the quality of cultivated land in different geomorphic areas, and each cultivated land landscape pattern index had different effects on the quality of cultivated land in different geomorphic areas.

Effects of layered soil on the accumulation and leaching of nitrate-nitrogen in shallow groundwater regions

WANG Shijun, TIAN Luyao, LIU Bingxia

2023, 31(1): 125-135. doi: 10.12357/cjea.20220409

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Excessive nitrogen application in agriculture causes the accumulation of nitrate-nitrogen (NO₃⁻-N ) in the vadose zone and intensifies nitrate pollution in groundwater. Heterogeneous layered soil is relatively common in nature and plays an important role in controlling pollutants entering groundwater from the surface. Heterogeneous layered soil exists in the low plain area of North China which is sensitive to groundwater pollution owing to its shallow groundwater burial and short nitrate leaching path. Thus, it is important to clarify the influence of the heterogeneous layered soil structure on the NO₃⁻-N migration process to prevent nitrate pollution in groundwater. In this study, four typical soil profiles, heterogeneous and relatively homogeneous, and two land use types were selected in Nanpi County, Hebei Province. The four typical soil profiles included three heterogeneous layered soils (P1, P2, P3), one relatively homogeneous profile (P4), and two land uses, which were unfertilized grassland with multiple 30 cm thin clay soil interlayers (P1), fertilizing farmland with multiple 30 cm thin clay soil interlayers (P2), fertilizing farmland with 140 cm thick clay soil interlayers (P3), and fertilizing farmland with relatively homogeneous silty loam (P4). The effect of layered soil on the accumulation and leaching of NO₃⁻-N was studied by analyzing the relationship between the physical and chemical properties of different layered soil profiles and NO₃⁻-N content in soil profiles and groundwater. The results showed that the vertical distribution of NO₃⁻-N was affected by the depth and thickness of the clay loam soil layer. The NO₃⁻-N contents in the three heterogeneous layered soil profiles were higher than that in the homogeneous profile with silt loam. In the three heterogeneous layered soil profiles, P3 with a 140-cm clay soil interlayer, its’ peak content of NO₃⁻-N (238 mg·L^–1) and the accumulation layer thickness (100–250 cm) were the highest. In the rainy season of 2018 (from August to September), the leaching amounts of NO₃⁻-N in the heterogeneous profiles were P3 (319.2 kg·hm^–2) < P1 (383.9 kg·hm^–2) < P2 (554.7 kg·hm^–2), which indicated that the control effect of the layered soil profile with a thick clay loam interlayer on NO₃⁻-N leaching was significantly better than that with multiple thin clay loam interlayers (P<0.05). NO₃⁻-N in shallow groundwater was affected by the soil deposition structure of the aquifer. The over-limit ratio and average increasing rate under a heterogeneous deposition profile with clay loam interlayers (P2, 93% and 2.14 mg·L^–1·d^–1) were significantly higher than those of the homogeneous deposition profile with silt loam (P4, 21% and 0.53 mg·L^–1·d^–1). This study verified that layered soil profiles have a blocking effect on soil water and NO₃⁻-N migration; and thicker the clay loam interlayer, the stronger is the blocking effect of soil water and NO₃⁻-N migration. The interaction of soil water and solution between the vadose zone and groundwater is frequent in shallow groundwater regions; thus, the NO₃⁻-N concentration in groundwater is controlled by the structure of the layered soil in the vadose zone and the depth of groundwater. These results provide a scientific basis for the prevention and control of nitrate pollution in shallow groundwater regions.

Climate-smart agriculture research: hotspots, trends, and prospects

PAN Youju, XU Yuting, YU Ran, XU Guoliang, ZHOU Yan, LI Yingni

2023, 31(1): 136-148. doi: 10.12357/cjea.20220467

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Abstract:
Climate-smart agriculture (CSA), a high-potential agricultural system solution to the dual challenges of climate change and food security, received great attention from researchers worldwide as soon as it was proposed. However, the progress of CSA research projects in China is slow and has not attracted widespread attention from the academic community. Using the CiteSpace (5.8. R3) software, this study selected the core data set of the Web of Science to analyze the international CSA research literatures from 2010 to 2021, sorted out foreign research hotspots and trends, and put forward new outlooks to provide theoretical and practical support for the development of CSA in China. The research results were as follows: 1) CSA had formed a complete conceptual framework for balancing agriculture and climate change in multiple dimensions. 2) CSA and sustainable intensification, smart agriculture (smart farming), conservation agriculture, and other researches were intertwined and developed, and research hotspots revolved around “three pillars”: productivity, adaptation, and mitigation. 3) The trend of CSA research tended to be generalized, and the research areas covered developing countries, research objects focused on multiple goals, and research content covered multiple fields. Finally, according to future research trends, CSA was predicted to pay more attention to its connotation exploration, implementation framework formulation, vulnerable group needs, interdisciplinary cooperation, and agricultural transformation. In addition, this study emphasizes that as a new model of agricultural development in response to climate change, the theoretical framework and practical technologies of CSA have both theoretical and practical significance for agricultural transformation in China, and its application and adaptive development in China is an area that needs to be urgently investigated.

Sustainable agricultural development from a green perspective in Japan: paths, results, and policy inspirations

MA Jian, YU Hao, ZHOU Jia

2023, 31(1): 149-162. doi: 10.12357/cjea.20220372

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Abstract:
Promoting agricultural development from a green perspective is an important direction for realizing the modernization of agriculture and rural areas. Since the 1970s, a green development model for agriculture has gradually formed in Japan, with organic agriculture and environmentally friendly agriculture as the main paths. Japan has achieved certain results in system construction, policy support, identification of ecological farmers, reduction of chemical input, and other aspects by undertaking several measures, such as the innovation of organization, establishment of a sound legal system, and reinforcement of the guiding role of excellent cases. The inductive method was applied in this study to systematically determine the innovation of relevant organizations and evolution of the legal and regulatory system of green agricultural development in Japan. Additionally, the case study method was used to summarize and compare the successful paths and main experiences of some excellent cases. We found that, first, a coordinated promotion mechanism of integrating officials and citizens has gradually formed in Japan upon the establishment of social groups, parliamentarian unions, organic societies, and other organizations. Second, a more accurate support system for laws and regulations has gradually been built by competent administrative departments under the continuous improvement of relevant policies to support the green development of agriculture. Meanwhile, various honors with Japanese characteristics have been set by the Competent Departments of Agriculture and Forestry in Japan to encourage farmers and agricultural business organizations to choose green production behavior; many excellent farmers and agricultural organizations have emerged and they play a good demonstration and leading role in the green and sustainable development of agriculture in Japan. However, the overall scale of organic and environmentally friendly agriculture in Japan remains a niche industry for the national agricultural layout. Although the penetration rate of environmentally friendly agriculture has increased considerably, Japan still faces some realistic challenges, such as the decreasing number of ecological farming households, limited premium space for green agricultural products, and relatively small scale and certification area of organic agriculture. To cope with these challenges, Japan has made great efforts to cultivate new agricultural business entities and actively promote the international development of organic agriculture. In addition, Japan has explored many innovation paths, such as creating regional environmental symbiotic industrial chains based on the idea of “integration of production and consumption”. Based on these results, the following suggestions are put forward for green and high-quality agricultural development in China: first, clarifying the path for green agricultural development and establishing technical standards for the reduction of chemical inputs; second, formulating an identification system for ecological farmers and cultivating successors to green agricultural development; third, attaching importance to the social academic groups for giving full play of their roles and functions to create a legal environment for green development of agriculture; fourth, building a national unified market for green agricultural products based on those products with good quality and based on the idea of “local production for local consumption”.

2023 Vol. 31, No. 1