中国生态农业学报(中英文)

Soil AMF community structure and assembly mechanism of Medicago sativa field in Loess Plateau

GAO Rui, LUO Zhuzhu, HE Renyuan, NIU Yining, LIU Jiahe, CAI Liqun, HAI Long

2023, 31(6): 835-844. doi: 10.12357/cjea.20220697

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Abstract:
Arbuscular mycorrhizal fungi (AMF) mediate the interactions between plants and soils, play crucial roles in terrestrial symbiosis, and are important components of soil microbial communities. However, information on the variations of soil AMF communities with respect to the loess soil properties is limited. Therefore, the present study investigated soil AMF diversity, community structure, and physicochemical properties in Medicago sativa fields and farmland in the Loess Plateau semi-arid area. Soil samples (0–20 cm) were collected in June 2021 from four treatments: maize (Zea mays) field (Farmland) and M. sativa fields established in 2019 (L₂₀₁₉), 2012 (L₂₀₁₂), and 2003 (L₂₀₀₃). Illumina MiSeq high-throughput sequencing and real-time fluorescent quantitative PCR were used to explore the structure and diversity of the AMF communities under the four treatments (Farmland, L₂₀₀₃, L_2012, and L₂₀₁₉). Statistical methods (redundancy analysis and molecular ecological network analysis) were used to explore the relationship between soil physicochemical properties and the AMF community. Zero-model analysis was used to reveal the assembly process of the soil AMF community. The results showed that long-term alfalfa planting decreased soil total phosphorus and available phosphorus contents. The AMF gene abundance ranged from 1.02×10⁴to 1.50×10⁴copies∙g⁻¹ in dry soil, which was significantly higher in M. sativa field planted in 2003 than in other treatments (P<0.05). Correlation analysis between the abundance of AMF genes and physicochemical factors showed that soil AMF gene abundance was positively correlated with total nitrogen content and negatively correlated with total phosphorus and available phosphorus contents. One class, four orders, seven families, and seven genera of AMF were identified. Glomus, Diversispora, and Paraglomus were the common genera of M. sativa fields and Farmland, and the dominant genera of M. sativa fields and Farmland were Glomus (65.15%−99.12%), mainly contributing to the changes of soil AMF community structure in different treatment groups. Long-term cultivation of M. sativa propagated rare microbial taxa, including Ambispora and Scutellospora, whereas Pacispora and Acaulospora were sterilized. Ambispora was significantly higher in M. sativa field planted in 2019 than in the other treatments (P<0.05). The analysis of the molecular ecological network showed that there were highly abundant genera (Glomus and Paraglomus) that had cooperative relationships in the ecological network, whereas the low-abundance genera (Pacispora and Acaulospora) had competitive relationships in the ecological network. RDA showed no main environmental factors affecting the AMF community structure. The null model was used to infer AMF community assembly processes. In Farmland and M. sativa field established in 2019, community mechanisms were dominantly assembled with deterministic processes (66.67%), with heterogeneous selection contributing the most. For the M. sativa field established in 2012 and 2003, the community mechanisms were dominantly assembled with random processes (100.00%); the undominated processes contributed the most to M. sativa field planted in 2012, and dispersal limitation contributed the most to M. sativa field planted in 2003. The Mantel test showed no main environmental factors driving AMF community assembly. Long-term cultivation of M. sativa increases the number of random processes. This is beneficial for maintaining the sustainability and stability of the artificial grassland ecosystem functions. In summary, long-term M. sativa planting significantly affected the composition of soil AMF communities. This study provides basic data and a theoretical basis for further studies on the microbial mechanisms of AMF on the Loess Plateau after years of M. sativa planting.

Evaluation of the effect of future climatic change on Hebei cotton production and water consumption using multiple GCMs

WANG Keyu, YANG Yanmin, YANG Yonghui, Liu De Li, CHEN Li

2023, 31(6): 845-857. doi: 10.12357/cjea.20230016

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Abstract:
Climatic models are the primary source of uncertainty in climate change impact assessments. Uncertainty can be significantly decreased by using multiple climate models during an assessment. In this study, the crop model APSIM-COTTON was carefully calibrated based on two years of field experiments, and 22 GCM (Global Climate Models) models (AR6) were used to drive crop models to evaluate the effects of climate change on cotton production and water consumption in Hebei Province. The leaf area index, plant height, squares number, bolls number, and dry matter weight of each plant were used to correct various APSIM-COTTON parameters. The coefficient of determination was greater than 0.8, indicating that the simulated and observed values fit well. The trend of climate change at this site was that the solar radiation intensity under SSP1-2.6, SSP2-4.5, and SSP5-8.5 was higher than the baseline (from 1980 to 2010) and increased with time, but it was lower than the baseline under SSP3-7.0. Temperature tended to increase in all scenarios, and the amplitude increased with the increase in radiative forcing and time. In most scenarios, the minimum temperature increased more than the maximum temperature, and annual rainfall increased over time. The responses of cotton production and water consumption to future climate change are the comprehensive effects of CO₂ concentration, solar radiation, temperature, rainfall, and other climatic factors. The crop model simulation results showed that the sowing date was advanced under all climate scenarios and future time periods, and all development stages (emergence, squaring, flowering, and harvesting) were shorter than those of the baseline period. In the 2090s, under scenarios SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5, the boll opening stage advanced 9.3, 12.0, 14.7, and 16.0 days, respectively, whereas the harvest stage advanced 15.3, 21.0, 30.3, and 35.2 days, respectively. The annual evapotranspiration (ET) under all scenarios, except SSP3-7.0, showed an increasing trend, whereas the irrigation amount decreased. Under the SSP5-8.5 scenario, the annual ET in the 2030s, 2050s, 2070s, and 2090s increased by 6.5, 7.8, 14.3, and 32.7 mm compared with the baseline, whereas the irrigation amount decreased by 25.7, 23.8, 30.5, and 29.0 mm, respectively. In the future, changes in cotton yield will not be large in scenarios of lower radiation focusing (SSP1-2.6), and there will be a decreasing trend with age under high radiation forcing (SSP5-8.5 and SSP3-7.0). Under SSP1-2.6 and SSP2-4.5 scenarios, lint yield decreased by approximately 61.5 and 46.6 kg∙hm⁻², respectively, in the 2090s. However, under SSP3-7.0 and SSP5-8.5 scenarios, the reduction by 2090s reached 407.1 and 432.5 kg∙hm⁻², respectively. In this study, 22 GCM models were used to simulate the response of cotton growth and water consumption to climate change over 100 years in the 21st century, and the changing trends in different scenarios and time periods were compared to provide technical support for developing adaptation strategies to climate change. However, the uncertainty of evaluating the climatic effect on cotton production still exists in this study. More site data should be considered in the calibration process, and more crop simulation models with different mechanisms should be compared in future research.

Effect of nitrogen fertilizer and soil conditioner on soil carbon and nitrogen content, and oat yield

SUO Wenkang, YANG Jinhan, HU Chenyang, FENG Shasha, TIAN Xiaoming

2023, 31(6): 858-867. doi: 10.12357/cjea.20220553

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Abstract:
Soil conditioners have been applied in agriculture due to advantages, such as coordinating soil water and fertilizer, improving soil water-retaining and fertility-reserving capacity. A new type of liquid conditioner was introduced in oat cultivation in this study, its’ effects on soil physical properties, and characteristics of soil organic carbon and nitrogen, and oat yield under nitrogen fertilizer reduction were investigated to explore the driving mechanism of N reduction by conditioners on crop yield and soil nutrients. Five treatments were set: no fertilizer (CK), 80% N fertilizer (N₈₀), regular N application (N₁₀₀), conditioner + 80% N fertilizer (PN₈₀), and conditioner + regular N application (PN₁₀₀). The results showed that the fertilizer + conditioner treatments differed from the single fertilizer treatments in terms of physical properties, carbon and nitrogen contents, and oat yield. The treatments with conditioner (PN₈₀ and PN₁₀₀) significantly increased soil water content, field capacity, porosity, and reduced soil bulk density compared with the treatments with only fertilizer. Furthermore, the nitrogen reduction of 20% (N₈₀) significantly increased soil porosity and reduced soil bulk density compared with conventional nitrogen application (N₁₀₀). The study showed that 20% N reduction had varying degrees of inhibition on organic carbon, total nitrogen, and its components in different soil layers. Furthermore, the addition of the conditioner significantly increased organic carbon, total nitrogen, nitrate nitrogen, active organic carbon, and microbial carbon in the 0–60 cm soil layer and 20−60 cm soil layer compared with the treatments with N fertilizer alone. The effect of the PN₁₀₀ treatment was the most significant. The effects of different treatments on the nutrients and yield of oats varied greatly, with that of the PN₈₀ treatment being the most significant. Compared with N₁₀₀, the total N, P, and K contents and crop yield of oats in PN₈₀ significantly increased by 12.93%, 15.16%, 3.69%, and 18.73%, respectively (P<0.05). Compared with N₁₀₀, N₈₀ significantly reduced N, P, and K uptake in oats at 20% N reduction, but did not cause yield reduction in oats. In conclusion, compared with conventional fertilization, N₈₀ with a soil conditioner improved soil properties, increased soil carbon content, reduced the risk of nitrate N leaching, and significantly increased the nutrient uptake and yield of oat. The effect of 80% N fertilizer + soil conditioner on the nutrient content and yield of oats was the most significant, while the treatment with 100% N fertilizer + soil conditioner was the most effective in improving soil nutrient content. This is essential to realize the green development of agriculture, reduce the environmental impact of fertilizer input, and improve the utilization rate of nitrogen fertilizers.

Effects of content dynamics of NO₃⁻-N and phenolic acids in soil on root growth of cotton seedlings under the return of wheat straw

LI Jianan, YANG Changqin, SHU Hongmei, ZHANG Guowei, WANG Xiaojing, LIU Ruixian, CHEN Jiamin, WANG Feibing, CHEN Xinhong

2023, 31(6): 868-876. doi: 10.12357/cjea.20220918

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Abstract:
Nitrate nitrogen (NO₃⁻-N) is the main form of nitrogen released from crop straws under dry farming conditions, and is the main form of nitrogen absorption by the roots and the plant root growth regulatory signal of cotton. Straw return affects the availability of soil and fertilizer N, thus inhibiting the early growth of crops and even decreasing crop yields. The straw return also releases many phenolic acids, inhibiting crop seed germination and root growth. This study aimed to reveal the mechanisms by which the contents dynamics of NO₃⁻-N and phenolic acid in the soil affect the growth of cotton seedlings under the return of wheat straw. Based on the 11-year return of wheat straw, field experiments were conducted in 2021 and 2022 at Jiangsu Academy of Agricultural Sciences Experimental Station in Nanjing, Jiangsu Province, China. Two treatments, wheat straw removal (CK) and wheat straw return (S), were applied. The contents of NO₃⁻-N and phenolic acid in the soil of the subsequent cotton field, the NO₃⁻-N content and nitrate reductase activity of cotton seedlings, the activity and morphology indices of cotton roots, and the biomass of cotton seedlings were investigated. The results demonstrated that straw return increased the contents of NO₃⁻-N and phenolic acid in the soil, and the effect on the 0–20 cm soil layer was greater than that on the 20–40 cm soil layer. With a delay of days after the straw return, the contents of NO₃⁻-N and phenolic acid in the soil increased and then decreased, reaching a peak at 24−31 d after the straw return. Within 31 days of straw return, the root activity, root NO₃⁻-N content, nitrate reductase (NR) activity, root biomass, and morphological indices of cotton seedlings under the straw return treatment were significantly lower than those under the CK treatment but showed the opposite trend after 31 d of straw return. The correlation analysis showed that phenolic acid content in 0–20 cm soil were significantly and negatively correlated with the root activity, NO₃⁻-N content, length, diameter, and surface area of the root, and the aboveground biomass of cotton seedlings. The NO₃⁻-N content in different soil layers was positively correlated with the index of morphology and physiology and the biomass of cotton seedlings but did not reach a significant level. The effect of straw return on the growth of cotton seedlings showed a trend of “first inhibition and then promotion”. Within 31 d after straw return, the “inhibition effect” of phenolic acid in soil on the growth of cotton seedlings was greater than that of the “fertilization effect” of straw. Higher phenolic acid content reduced the root activity and root growth of cotton seedlings, inhibiting the absorption and utilization of NO₃⁻-N in cotton seedlings. After 31 d of straw return, the “fertilization” effect of straw was greater than the “inhibition” effect of phenolic acid, promoting the root growth of cotton seedlings.

Effects of long-term cotton straw return and application of manure on soil nutrients and enzyme activity in cotton fields

GUO Zhenwei, LI Yongshan, WANG Hui, CHEN Mengni, FAN Qiaolan, YANG Na, XI Jilong, ZHANG Jiancheng

2023, 31(6): 877-884. doi: 10.12357/cjea.20220614

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Abstract:
Incorporation of straw and manure into soil plays an important role in nutrient management, maintenance of crop productivity, and improvement of soil quality. An experiment was conducted to clarify the effects of long-term cotton straw returning and manure application on soil nutrient and enzyme activities in continuous cropping cotton fields, and to provide scientific evidence for cotton straw returning and manure application. The experiment relied on a long-term experiment (since 2007) in an agricultural system conducted by the Niujiawa Cotton Agroecosystem Experimental Station of the Cotton Research Institute, Shanxi Academy of Agricultural Sciences. Four treatments were established on the base of application of nitrogen and phosphorus fertilizers, namely straw stubble removal (NP), straw returning (NPS), manure application (NPM), and straw returning + manure application (NPSM). The cotton yields of the treatments of NPS, NPM, and NPSM significantly increased by 10.23%, 11.10%, and 26.22% (P<0.05), respectively, compared with that of the NP treatment. The contents of soil total nitrogen, total phosphorus, alkali hydrolyzable nitrogen, available potassium, and available phosphorus in the NPSM treatment significantly increased by 48.76%–60.18%, 91.23%–112.18%, 140.63%–229.17%, 35.86%–60.54%, and 146.92%–483.34% (P<0.05), compared with those of the NP treatment, respectively. NPSM treatment significantly increased soil enzymes activities (P<0.05): urease activity by 118.50%–151.84%, phosphatase activity by 76.81%–93.11%, catalase activity by 30.53%–41.33%, and invertase activity by 83.41%–129.32%, compared with those of the NP treatment. There were significant positive correlations between soil nutrient content and soil enzyme activity. Therefore, long-term straw return with manure application can significantly increase cotton yield, nutrient content, and enzyme activity for soil fertility improvement in continuously cropped cotton fields.

Spatiotemporal changes in physiology and total flavonoids of Tetrastigma hemsleyanum in response to blue and purple monochromatic light

LIU Shouzan, JIANG Lingtai, ZHANG Yun, GU Yiwen, HAN Minqi, LI Shan, WANG Hongzhen, BAI Yan

2023, 31(6): 885-894. doi: 10.12357/cjea.20230118

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Abstract:
Tetrastigma hemsleyanum Diels et Gilg has antitumor, antiviral, and fever-relieving properties. The main active components are flavonoids. It grows in shaded environments in forests, and its growth, development, physiological changes, and synthesis of active components are regulated by short-wavelength light of undergrowth. To explore the spatial and temporal responses of physiological mechanisms and flavonoid synthesis in T. hemsleyanum to short-wavelength light, blue or purple monochromatic light were selected as treatment light sources, and white light was used as the control for 7, 15, 30, 45, and 60 d. The total flavonoids content, flavonoid-related enzymes activities, and physiological and biochemical indexes, such as photosynthetic pigments, anti-resistance enzymes activities, malondialdehyde (MDA), and primary metabolic solubility, of leaves were measured to investigate the spatial and temporal responses of the flavonoid synthesis process and physiological and biochemical changes in T. hemsleyanum to short-wavelength light conditions. The results showed that: 1) short-wavelength light treatments regulated the changes in photosynthetic pigments contents; the control and blue light treatments increased photosynthetic pigments contents, but the purple light treatment significantly inhibited this effect. 2) Continuous monochromatic short-wave light treatments put T. hemsleyanum under mild stress, and the total flavonoids content was the highest with blue light treatment (137.75 mg∙g⁻¹ in leaves and 149.00 mg∙g⁻¹ in tubers). The phenylalnine ammonialyase activities in leaves and tubers (96.50 U∙g⁻¹ FW, 109.47 U∙g⁻¹ FW) and chalcone isomerase activity in leaves (65.17 U∙g⁻¹ FW) were highest under purple light treatment; while chalcone synthase activity in tubers was the highest with blue light treatment (46.76 U∙g⁻¹ FW). In addition, photosynthetic pigments, resilience, and soluble substances differed in their responsiveness to short-wave light, and both blue and purple light promoted the accumulation of osmoregulatory substances compared with white light. This study provided a theoretical basis and practical guidance for light regulation of T. hemsleyanum quality.

Nitrogen acquirement strategy of different nitrogen forms in two pineapple cultivars

CHEN Xiaohui, XU Xiuyu, FU Liyong, PAN Yanju, FENG Ying, CAI Zhiquan

2023, 31(6): 895-903. doi: 10.12357/cjea.20220857

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Abstract:
Pineapple [Ananas comosus (Linn.) Merr.] is China’s third largest tropical fruit, with the largest planting area in Xuwen County, Guangdong Province. As one of the most important macronutrients, nitrogen is closely related to pineapple yield. However, the uptake preferences for different nitrogen forms in field-grown pineapple plants remain unclear. In this study, the morphological, physiological, and growth traits of plants with different ages were measured in two field-grown pineapple cultivars (‘Tainong 17’ and ‘Bali’) with different growth periods in April and September, respectively, in Xuwen County. In addition, nitrogen acquisition strategies for three different forms of nitrogen (ammonium nitrogen, nitrate nitrogen, and glycine) in the pineapple roots were determined using the stable isotope ¹⁵N tracer technique. The results indicated that the growth period of the ‘Tainong 17’ pineapple (16 months) was shorter than that of ‘Bali’ (20 months). During the fruit harvest period in April, compared with the ‘Bali’ pineapple (796 g fresh fruit weight per plant), ‘Tainong 17’ pineapple plants had lower yield (532 g fresh fruit weight per plant), root biomass, and P content; but had similar plant height, plant biomass per plant, leaf N and K contents, and specific leaf area. As an indicator of long-term water-use efficiency, the δ¹³C value ranging from −15.16‰ to −13.28‰, was higher in the leaves of ‘Tainong 17’ pineapple than that in ‘Bali’. Neither cultivar nor age greatly affected the leaf δ¹³C values. In April and September, there were significant differences in the different forms of nitrogen uptake between the two pineapple cultivars. The nitrogen uptake capacity of ‘Tainong 17’ pineapple was higher than that of ‘Bali’. The high acquirement capacity of nitrogen and water use efficiency of ‘Tainong 17’ pineapple is attributed to promoting photosynthesis and thus maintaining plant growth in a relatively short life cycle. Both pineapple cultivars preferred to acquire ammonium nitrogen (36.8%–64.6%), followed by glycine (23.2%–47.1%), and the uptake rate of nitrate nitrogen was the lowest (9.1%–31.5%). The nitrogen uptake rate of pineapple plants in the vegetative growth stage (5–8-month-old) was higher than that of plants in the fruit-harvesting stage. However, with increasing plant age, the contribution rate of ammonium nitrogen increased, whereas that of glycine gradually decreased. Across different pineapple cultivars and plant ages, the rates of different forms of nitrogen uptake were not linearly correlated with the soil nitrogen content or measured plant traits. To the best of our knowledge, this is the first study to show that the roots of field-grown pineapple plants can directly absorb organic nitrogen from the soil. Cultivar and plant growth stages of pineapples are important factors that affect nitrogen acquisition strategies. However, the linear relationships between the absorption rates of different forms of nitrogen and soil nitrogen content or measured plant traits were very weak. These results contribute to nitrogen fertilizer management in pineapple plantations.

Analysis of differential metabolites and metabolic pathways of mono- and inter-cropped wheat in response to Blumeria graminis f. sp. tritici infection

CHEN Sheng, WU Xinyu, HE Jianyang, ZHOU Dong, LIU Zhenyang, TANG Li, ZHENG Yi, XIAO Jingxiu

2023, 31(6): 904-916. doi: 10.12357/cjea.20220808

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Abstract:
Wheat and faba bean intercropping can alleviate the occurrence and severity of wheat powdery mildew. However, the physiological mechanism of intercropping improving wheat disease resistance remains unclear. This study aimed to understand the metabolic differences between mono- and inter-cropped wheat in response to Blumeria graminis f. sp. tritici infection and reveal the physiological mechanism of intercropping for improving wheat resistance to powdery mildew. In this study, the following three nitrogen (N) application levels were established: 75 mg·kg⁻¹ (N1), 150 mg·kg⁻¹ (N2), and 225 mg·kg⁻¹ (N3). Following inoculation with B. graminis f. sp. tritici, the occurrence of powdery mildew in mono- and inter-cropped wheat was investigated, and the metabolomics of mono- and inter-cropped wheat in response to infection with B. graminis f. sp. tritici were analyzed by UPLC-MS/MS, using a widely targeted metabolomic method. The results showed that N levels and N levels × planting patterns significantly affected the incidence and disease indices of powdery mildew in wheat. Under all three N levels, wheat intercropping with faba bean reduced the incidence of wheat powdery mildew by 25.54%–38.81% and decreased the disease index by 20.11%–21.97% relative to mono-cropped wheat (MW), and the intercropping control effect under the N1 level was better than that under N2 and N3 conditions. A total of 822 differential metabolites were detected in the mono- and inter-cropped wheat leaves, of which 69, 52, and 88 were detected at the N1, N2, and N3 levels, respectively. Intercropping of wheat and faba bean regulated flavonoids, alkaloids, amino acids and derivatives, and phenolic acids in wheat leaves compared to MW. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis of differential metabolites showed that they were mainly enriched in the biosynthesis of amino acids, metabolic pathways, and secondary metabolites. Among them, metabolites with significant differences were enriched in metabolic pathways at the N1 and N2 levels, and metabolites with significant differences were enriched in amino acid biosynthesis under N stress conditions (N1 and N3). Further analysis of the metabolites from the top 10 up- and down-regulated genes revealed that intercropping upregulated glutathione (G-SH), L-tryptophan, L-asparagine, and L-glutamine in wheat leaves at the N1 level relative to MW, and upregulated L-asparagine, L-homomethionine, and L-tryptophan in intercropped wheat leaves at the N3 level relative to MW. In addition, a few metabolites, including alkaloids, phenolic acids, and organic acids, in wheat leaves were regulated by intercropping compared with MW under the N1 and N3 levels. In conclusion, the response of wheat to powdery mildew infection was regulated by N levels. Metabolites involving amino acids and derivatives, alkaloids, phenolic acids, and organic acids in wheat leaves are regulated by intercropping during B. graminis f. sp. tritici infection and induce different physiological reactions, possibly being one of the mechanisms by which intercropping improves wheat powdery mildew resistance. Intercrop-regulated amino acids and their derivatives under N stress are closely associated with wheat powdery mildew resistance. The present study identified the different responses of mono- and inter-cropped wheat to disease infection via metabolic analysis, facilitating a comprehensive understanding of crop diversity for the management of pests and diseases.

Accuracy evaluation and consistency analysis of multi-source remote sensing land cover data in the Yellow River Basin

WU Zongyang, CAI Zhuoya, GUO Ying, WANG Yanfang

2023, 31(6): 917-927. doi: 10.12357/cjea.20220816

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Abstract:
With the development of multi-source remote-sensing platforms and technologies, various land cover datasets have been developed that provide a wealth of data to support the understanding of global land cover conditions, land surface process model simulations, and socioeconomic development decisions. However, selecting appropriate data for different regions from nationally or globally available land cover datasets is challenging. In this study, six land cover products in 2020 over the Yellow River Basin, including CLCD_v01_2020, GLOBELAND30, GLC_FCS30_2020, LANDCOVER (300 m), MCD12Q1 (500 m), and CNLUCC1000 (1000 m), with resolutions ranging from 30 to 1000 m, were evaluated for regional-scale accuracy and consistency analysis. Accuracy analyses were performed on six products based on 1540 samples for seven land cover types collected by Google Earth. Data with the highest overall accuracy (OA) were used as a reference for the area consistency analysis of the other five products. Category confusion and confusion mapping analyses were performed on six types of data. Hopefully, this study will provide a scientific reference for users to select appropriate land cover data for the Yellow River Basin. The results showed that the highest classification accuracy was for CLCD_v01_2020, with an OA of 88.12%, followed by GLOBELAND30 (OA=85.32%), GLC_FCS30_2020 (OA=84.09%), LANDCOVER300 (OA=77.79%), MCD12Q1 (OA=73.38%), and CNLUCC1000 (OA=71.82%). The KAPPA coefficients of the land cover products with a resolution of 30 m were all above 0.8, and the classification accuracy decreased as the spatial resolution decreased. CLCD_v01_2020, with the highest OA, was used as the reference dataset, and the area correlations and confusion mapping were calculated separately for the remaining five validation product datasets. The relative proportions of different land cover types were generally consistent across the six products; however, there were still large differences between croplands and grasslands. GLC_FCS30_2020 had the highest correlation with the reference data CLCD_v01_2020, with an R² value of 0.9976. Category confusion analysis showed that the six data types were generally confused between croplands, forests, and grasslands. There was good consistency in the grasslands of eastern Qinghai in the upper reaches of the Yellow River and the cropland and construction land of the middle and lower reaches. The areas of poor consistency were mainly in the middle reaches of the Yellow River in northern Shaanxi and western Shanxi, which were mainly confused grasslands with forests. For the primary classification of land cover data in the Yellow River Basin, it is recommended that CLCD_v01_2020 data be selected for 30 m resolution and LANDCOVER300 for 100-m scale resolution data. In contrast, secondary classification can be chosen according to the desired classification system.

ENSO events impacts on apple production in Shandong Ⅱ: Changes in agricultural meteorological disasters under different ENSO scenarios and their impacts on apple yield

CUI Cheng, LIU Yuan, LIU Buchun, SUN Yankun, YANG Fan, ZHANG Xiaonan, LIU Shanshan, ZHU Yongchang, HE Jinna

2023, 31(6): 928-942. doi: 10.12357/cjea.20220533

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Abstract:
Apple is one of the dominant fruits in Shandong Province, and its production is profoundly affected by agricultural meteorological disasters. Exploring the evolutionary characteristics of agrometeorological disasters and their influence on local apple production under extreme climate events is of great significance. In this study, based on daily meteorological data, prefectural and municipal apple production statistical data, and monthly ENSO event data from 1991 to 2019 in Shandong, we analyzed the objectives of the study using mathematical statistical analysis and ArcGIS spatial expression. First, the results showed significant regional differences in agrometeorological disasters under different ENSO years from 1991 to 2019. During the period of fruit expansion from June to August, droughts occurred frequently during El Niño years (78 times), and the highest drought frequency was approximately 50%. In neutral years, flooding disasters were relatively serious, occurring up to 60 times. Drought frequently occurred in areas with sufficient heat resources, such as in West and Central Shandong. Rainfall and waterlogging disasters frequently occurred in areas with abundant rainfall resources in South Shandong. In East Shandong and the Jiaodong Peninsula, extreme low-temperature disasters occurred frequently during the apple flowering period from March to May. The number of low-temperature days was approximately 7–9 d·a⁻¹, with a frequency of approximately 60%–100%. In West Shandong and other places, high-temperature heat disasters occurred during the apple fruit expansion period from June to August, with occurrence days of 11–15 d·a⁻¹. Second, the study showed that, under different ESNO events, drought was positively correlated with El Niño years, whereas it was negatively correlated with La Niña years. During the apple growth period from March to October, there was a positive correlation between the Southern Oscillation Index (SOI) and rainfall during El Niño years, while there was a negative correlation between the SOI and rain waterlogging during La Niña and neutral years. Low-temperature disasters were negatively correlated with the SOI in El Niño years, while they were positively correlated with the SOI in La Niña and neutral years during the apple flowering period from March to May. Third, from March to October, the drought in the Jiaodong Peninsula intensified, leading to an increase in the apple yield reduction rate in El Niño years. Furthermore, the impact of rain and waterlogging on apple yield and income was aggravated in neutral years. In La Niña years and neutral years, drought in West Shandong was positively correlated with apple yield reduction rate. Meanwhile, in neutral years, the rainfall in most areas of Shandong was positively related to the reduction rate of apple yield during the apple expansion period from June to August. In El Niño years, the reduction rate of apple yield was less affected by extreme low-temperature disasters but more affected by high-temperature heat damage. The number of days of low temperature increased in most areas of Shandong during La Niña and neutral years, which led to a reduction in the rates of apple yield and risk increase. Owing to the high temperature and drought in the ENSO event, we should prevent the effects of low temperature, rain, and waterlogging on apple yield and quality and ensure the healthy and sustainable production of the apple industry.

Quality and quantity characteristics of saline ice meltwater under different pretreatments

QI Ji, SONG Jianbin, ZHAO Ying, HU Qiuli, PAN Yinghua, YU Qianjun

2023, 31(6): 943-953. doi: 10.12357/cjea.20220924

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Abstract:
Saline ice irrigation has a positive effect on heavy saline land reclamation and is of great practical importance for alleviating freshwater shortages. Water-salt separation is a salt redistribution process during saline ice melting. We aimed to clarify the influence of pretreatment on the quantity and quality of melted water and the melting duration of saline ice. To achieve these parameters, four ice pretreatments, including aerated ice, stacked ice, crushed ice, and regular ice; and four initial total dissolved solids (TDS) of saline ice of 0, 5, 10, and 15 g·L⁻¹ were used to compare and analyze the dynamics of water quantity and quality during the saline ice melting process. The results showed that aeration, stacking, and crushing treatments significantly reduced the melting duration compared with that of regular ice. The melting duration of each treatment was crushed ice < stacked ice < aerated ice < regular ice. The meltwater volume per unit time showed a trend of rapid increase followed by a gradual decrease, with the peak water volume in the order of regular ice < aerated ice < stacked ice < crushed ice. As the melting process continued, the TDS of the meltwater decreased rapidly and finally stabilized. Among all the pretreatments, the TDS and sodium adsorption ratio (SAR) of meltwater from crushed ice were significantly lower than those from regular ice. The highest freshwater (<1 g∙L⁻¹) yield was 33.26% at the initial TDS of 5 g∙L⁻¹ for crushed ice. Pretreatment measures can significantly change the water-salt reallocation process of saline ice melting, which provides a theoretical basis for utilization of saline groundwater resources.

Screening of accumulating plants in farmland surrounding typical lead and zinc smelting enterprises

HE Mengke, GUO Junmei, YANG Junxing, ZHENG Guodi, CHEN Tongbin, MENG Xiaofei, LI Yufeng, LIU Jie

2023, 31(6): 954-966. doi: 10.12357/cjea.20220711

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Abstract:
As one of the most important lead (Pb) and zinc (Zn) smelting production bases in China, the heavy metal content in the farmland surrounding the enterprises in Jiyuan City of Henan Province seriously exceeded the national standard due to the backward technology and large pollutant discharge. In order to explore the characteristics of heavy metal contamination in farmland around Pb and Zn smelting enterprises in Jiyuan City, select the dominant plants for remediation and safe utilization of heavy metal-contaminated farmland, and establish a preliminary remediation model, field experiments were conducted on farmland surrounding Pb and Zn smelting enterprises in Jiyuan City. The study included investigating the characteristics of cadmium (Cd), Pb, and arsenic (As) pollution in soil, analyzing the heavy metal content in main agricultural products, selecting 17 kinds of heavy metal-accumulating plants for field cultivation, and studying their biomass, heavy metal contents, bioconcentration factor, extraction amount, and remediation efficiency. The results showed that the average content of Cd, Pb, and As in soil was 2.22 mg·kg⁻¹, 173.1 mg·kg⁻¹ and 18.38 mg∙kg⁻¹, respectively, which were mainly distributed in the cultivated layer. Among them, the content of Cd and Pb exceeded the risk screening values in the Environmental Quality Standard for Soils (GB 15618—2018), and the single factor pollution index reached 3.71 and 1.02, respectively. In terms of the wheat and maize cultivated on the contaminated farmland, the content of Cd, Pb, and As in maize seeds did not exceed the values in the National Food Safety Standards (GB 2762—2022), but the Cd and Pb content in wheat seeds exceeded the standards, while the exceeding rates both reached 100%. In plant cultivation experiments, the biomass and heavy metal enrichment capacities of the 17 kinds of accumulating plants differed significantly. The biomass of Amaranthus hypochondriacus was the highest, reaching 29 598 kg·hm⁻², which was 46.61 times that of Noccaea caerulescens (635 kg·hm⁻²). The contents of Cd, Pb, and As in the 17 plant species were 2.90−30.90 mg·kg⁻¹, 7.81−93.07 mg·kg⁻¹, and 3.76−22.90 mg·kg⁻¹, respectively. The bioconcentration factors of Cd, Pb, and As were 1.31 to 13.92, 0.05 to 0.54, and 0.20 to 1.24, respectively. Helianthus annuus ‘S606’ had the largest Cd, Pb, and As comprehensive bio-concentration index of 2.3. Combining plant biomass and enrichment capacity, 17 plant species showed clear differences in the removal efficiency of contaminated soil. Cluster analysis showed that Amaranthus hypochondriacus, Brassica napus ‘Zhongyou 1000’, and Helianthus annuus ‘S606’ had higher Cd and Pb accumulation and remediation capacities in soil. The removal efficiency of these three species was higher than 1.90% for Cd and 0.07% for Pb, showing a promising potential for remediation of Cd and Pb-contaminated soils. In addition, Brassica napus and Helianthus annuus can be further processed to produce edible oil, feed, or fertilizer, which can bring economic benefits while remediating soil. In conclusion, the farmland surrounding the Pb and Zn smelting enterprise in Jiyuan City was typically light to moderately contaminated with Cd and Pb. In response to this situation, two technical modes of heavy metals-contaminated farmland remediation were proposed: Amaranthus hypochondriacus-Brassica napus rotation remediation mode and Helianthus annuus monoculture remediation mode. Both modes can achieve high remediation efficiency and were viable and extendable.

Effects of the combination of polystyrene nanoplastics and lead on seed germination and seedling growth of spinach (Spinacia oleracea)

GUO Linlin, ZU Jingmei, WANG Jingjing, CHEN Bingxu

2023, 31(6): 967-975. doi: 10.12357/cjea.20220721

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Abstract:
Microplastics (MPs) are a new environmental pollutant that has attracted widespread attention because of their negative effects on organisms and the environment. However, studies on the impact of co-contamination of MPs and heavy metals on vegetables are limited. To explore the effects of polystyrene nanoplastics (PSNPs), lead (Pb), and their co-contamination on seed germination and seedling growth of spinach, we investigated the germination rate, germination vigor and germination index of seeds; root length, shoot length, superoxide dismutase (SOD) and peroxidase (POD) activities, and soluble protein content of seedlings of spinach (Spinacia oleracea), which were exposed to the control, PSNPs (200, 400, 800, and 1600 mg·L⁻¹) and Pb (5, 25, 50, and 100 mg·L⁻¹) and their combination (Pb 5 mg·L⁻¹+ PSNPs 200 mg·L⁻¹, Pb 5 mg·L⁻¹+ PSNPs 800 mg·L⁻¹, Pb 50 mg·L⁻¹+ PSNPs 200 mg·L⁻¹, and Pb 50 mg·L⁻¹+ PSNPs 800 mg·L⁻¹). Single effects of PSNPs (≥400 mg·L⁻¹) significantly decreased the germination rate, vigor, and index; however, there was no significant difference between 200 mg·L⁻¹ PSNPs and the control for those indicators. PSNPs at low concentrations (200 mg·L⁻¹) promoted the length of roots and shoots, but other PSNPs concentrations (≥400 mg·L⁻¹) had no significant impacts on roots and shoots. SOD activity was inhibited at a high concentration (≥800 mg·L⁻¹) of PSNPs, and the POD activity was induced when PSNPs ≤800 mg·L⁻¹, whereas POD was inhibited at the high PSNPs concentration (1600 mg·L⁻¹). The soluble protein content in spinach seedlings under different concentrations of PSNPs increased, but the content was significantly higher than the control at 800 mg·L⁻¹ PSNPs. Under Pb exposure alone, germination rate, vigor, and index decreased. Further, treatments with low Pb concentration (5 mg·L⁻¹) increased root and shoot length, whereas high concentrations (≥25 mg·L⁻¹) reduced them. Moreover, SOD inhibition and POD induction were observed following Pb treatment. With increased Pb concentration, the soluble protein content of spinach seedlings decreased firstly at low concentration (5 mg·L⁻¹) and then increased. Compared with single Pb treatment, combined effects of PSNPs and Pb were generally antagonistic to seed germination. For example, PSNPs weakened the promotion effects of low Pb concentration (5 mg∙L⁻¹), inhibited the growth of root and shoot of spinach seedlings, and alleviated the inhibitory effects of high Pb concentrations (50 mg∙L⁻¹) on seedling root and shoot growth. Low concentration (200 mg·L⁻¹) of PSNPs and Pb showed synergistic effects in spinach seedlings, such as enhanced induction effects of Pb on POD activity. The co-contamination of PSNPs at high concentrations (800 mg·L⁻¹) and Pb caused greater damage to seedlings, and the activities of SOD and POD decreased significantly. These results showed that PSNPs alleviated the inhibitory effects of Pb on spinach seed germination. Low concentrations of PSNPs (200 mg∙L⁻¹) and Pb mainly showed synergistic effects, whereas high concentrations of PSNPs (800 mg∙L⁻¹) and Pb mainly showed antagonistic effects. This study demonstrates that co-contamination of PSNPs and Pb has significant toxicity on seed germination and seedling growth, affecting the antioxidant system and soluble proteins of spinach. In conclusion, coexisting PSNPs can alter the bioavailability of Pb and plant performance. Our findings can help evaluate the individual and comprehensive toxicity of microplastics and heavy metals in vegetable crops.

Impact of joining cooperatives on green production of family farms: an empirical analysis based on 422 provincial demonstration family farms

ZHANG Mingyue, ZHENG Jun, ZHAO Xiaoying

2023, 31(6): 976-988. doi: 10.12357/cjea.20220817

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Abstract:
Green production is the inevitable course to develop agriculture sustainably. To explore the effective methods of green production, the key area of modern agriculture, for family farms is of considerable theoretical value and practical significance. This study empirically analyzed the influence of family farms joining cooperatives on green production and its mechanism using the ranking selection and explanatory structure models based on the investigation data of 422 provincial demonstration family farms in Shandong Province. 1) Quantitative analysis showed that the proportion of green production of family farms joining cooperatives was evidently higher than that of farms not joining cooperatives. 2) From heterogeneity analysis, the proportion of green production by cooperative leaders’ farms was higher than that of farms with ordinary members. Joining cooperatives was significant for the green production of grain and vegetable family farms but not for fruit and livestock breeding farms. Joining the cooperative had a significant impact on the green production of medium-sized (10–20 people) farms but had no significant impact on the behavior of small-scale (less than 10 persons) and large-scale (more than 20 persons) farms. 3) After the family farm joined the cooperative, the three green production behaviors with the highest adoption rates were applying organic fertilizer (74.35%), water-saving irrigation (68.17%), and subsoiling (65.80%). In contrast, the three green production behaviors with the lowest adoption rates were ecological treatment of livestock and poultry breeding waste (26.84%), recycling pesticide waste (41.81%), and integration of water and fertilizer. 4) The regression equation results showed that family farms significantly increased the possibility of green production by joining cooperatives. Under the control of other variables, joining the cooperative had a significant positive impact on the green production of family farms at the 1% level, with an impact coefficient of 0.554, and the promotion of water-saving irrigation, application of organic fertilizer, and integration of water and fertilizer were more prominent. After considering other control variables, family farm management type, labor force, product quality certification, traceability of origin, and awareness and willingness toward green production all influenced green production. 5) From the explanatory structure model analysis, seven significant influencing factors played independent roles and were also interrelated, forming a complete chain of influencing factors for family farms to participate in green production. Joining the cooperative as a deep-rooted factor directly affected the origin traceability and product quality certification of family farm products and affected the green production of family farms from the source along the positive conduction relationship of “family farm green production cognition → green production willingness →green production behavior”. Therefore, we should encourage and support family farms to join cooperatives, focus on the heterogeneity between farms, and promote green production on farms through the training and supervision of cooperatives.

2023 Vol. 31, No. 6