中国生态农业学报(中英文)

Habitat-specific influences on insect diversity in regional landscapes: A case study of Xishuangbanna

ZHANG Xiang, LU Zhixing, WANG Qing, GAO Shutong, TANG Chunying, LI Qiao, CHEN Youqing

2021, 29(5): 771-780. doi: 10.13930/j.cnki.cjea.200684

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Abstract:
Habitat-specific plays an important role in the maintenance of biodiversity. This study aimed to understand the influence of habitat type on the diversity of different insect groups and the differences in community structure across the regional landscape. This study also explored the distribution patterns and maintenance mechanisms of insect diversity on a large scale. From August to September 2019, the sample line survey method was used in the Xishuangbanna region to estimate the number of species and endemic species of butterflies, true bugs, and beetles in four different habitat types (reserve, secondary forest, artificial forest, and farmland) and to analyze the habitat specificity index of the insect communities, the community structure similarity, and the relationships between species richness and the ecological factors. A total of 2588 insects were collected, including 94 butterfly species (744 heads), 197 bug species (1094 heads), and 129 beetle species (750 heads). The number of insect species and endemic species in the reserve was higher than those in the other habitats, and the observed habitat specificity index of the insect community was higher than the expected value in the reserve. The observed habitat specificity index values for the other habitat types were lower than the expected values. There was no significant difference in the habitat specificity index of the insect communities in different habitat types (F_{3, 57}=2.054), but there was a significant difference in the habitat specificity index of beetles (F_{3, 55}=3.478). The habitat specificity index of butterflies (F_{3, 38}=1.504) and true bugs (F_{3, 53}=1.153) did not differ. Analysis of the community structure similarity showed that the insect community structure of the three groups significantly differed between the reserve and farmland. There was a significant difference in the community structure of butterflies between secondary forests and artificial forests (P=0.037), and there was a significant difference in the community structure of true bugs between the reserve and secondary forests (P=0.029). There was no difference in the insect community structure of beetles (P=0.507), and only habitat type had a significant effect on the species richness of the insect community. The other ecological factors did not have a significant effect. In large-scale regional landscapes, the reserve had the greatest impact on diversity, and the habitat types were closely related to the species richness of the insect communities. Well-protected natural forests are important for maintaining the distribution and diversity of insect communities in regional landscapes.

Phosphorus flow characteristics and its influencing factors on the crop-livestock system of Jiangsu Province

YU Le, GUO Haohao, FU Yang, ZHAO Hongwei

2021, 29(5): 781-791. doi: 10.13930/j.cnki.cjea.200526

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Abstract:
To provide a theoretical basis for the sustainable development of the crop-livestock production system in Jiangsu Province, this study explored phosphorus flow and its influencing factors. Literatures research, data analyses, combined with the NUFER model (NUtrient flow in the Food chain, Environment, and the Resource use) were used to quantitatively analyze phosphorus flow and its influencing factors in the crop-livestock production system of Jiangsu Province from 1998 to 2018. The total phosphorus inputs of the crop-livestock production system from 1998 to 2018 decreased from 423.19 Gg to 382.86 Gg, and the main reduced inputs were chemical fertilizer and exogenous feed. The fertilizer input per unit cultivated area decreased from 78.78 kg·hm^-2 to 67.27 kg·hm^-2, and the supply of exogenous feed phosphorus decreased from 58.07 Gg to 46.54 Gg. The total output of phosphorus increased from 194.24 Gg to 255.06 Gg. The dominant output items were main crop products and animal by-products; the main crop products increased from 77.53 Gg to 131.86 Gg. The phosphorus utilization rate of the agricultural production subsystem increased from 31.82% to 52.46%, and the livestock production subsystem remained between 27.67% and 35.31%. The results showed that the phosphorus utilization rate of the crop-livestock production system was consistent with that of the agricultural production subsystem, which increased from 16.55% to 32.24%; phosphorus loss per unit of crop-livestock products decreased from 0.26 kg(P)·kg^-1 to 0.12 kg(P)·kg^-1. From 1998 to 2018, crop-livestock husbandry in Jiangsu Province developed rapidly, the total phosphorus input decreased annually, the output of crop-livestock products increased annually, and the total phosphorus loss to the environment (runoff, erosion, leaching, and manure loss) decreased annually. Reductions in chemical fertilizer input, fertilization based on soil testing formula, and planting and breeding structure adjustments led to a slightly higher utilization rate of phosphorus in the crop-livestock production system compared to the national level. Thus, nutrient management had achieved preliminary results, but there was still some room for improvement. To promote the sustainable development of crop-livestock husbandry in Jiangsu Province, it is necessary to further control phosphate fertilizer input, increase the input of organic fertilizer and local feed, improve the comprehensive utilization rate of straw and livestock manure, adjust the planting structure and breeding layout, develop planting, and restrict breeding.

Effect of rice-frog cultivation on ammonia volatilization in rice-Chinese milk vetch rotation system

CHEN Huiyan, SHA Zhimin, WU Fujun, FANG Kaikai, XU Chunhua, YANG Xiaolei, ZHU Yuanhong, CAO Linkui

2021, 29(5): 792-801. doi: 10.13930/j.cnki.cjea.200657

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Abstract:
Ammonia (NH₃) volatilization is one of the main mechanisms of nitrogen loss in paddy fields. Studying the impact of the ecological cultivation model in paddy fields on ammonia volatilization can provide a theoretical basis for its ecological and environmental benefits. To evaluate the effects of rice-frog cultivation on ammonia volatilization in a rice-Chinese milk vetch (CMV) rotation system, the continuous airflow enclosure method was used to collect ammonia in a field plot experiment to study soil ammonia volatilization and its related factors. The experiment included three treatments: control check (CK, no fertilization, no frogs), conventional rice cultivation (CR, fertilization, no frogs), and rice-frog cultivation (RF, fertilization, frogs released). The results showed that the cumulative amount of ammonia volatilization in the rice-frog cultivation treatment was 47.02 kg·hm^-2, accounting for 12.9% of the nitrogen application rate in the current season. The subsequent cumulative amount of ammonia volatilization in the Chinese milk vetch season was 16.27 kg·hm^-2. The cumulative ammonia volatilization in the annual rotation system was 63.29 kg·hm^-2, which was 15.3% lower than that of conventional rice planting. The cumulative amount of ammonia volatilization produced by rice-frog cultivation in the annual rice-Chinese milk vetch rotation system accounted for 17.4% of the annual nitrogen application, which was significantly lower than that of conventional rice cultivation (20.5%). The ammonium nitrogen concentration in the floodwater was the main factor affecting ammonia volatilization in the rice season, followed by the pH and temperature of the floodwater, air temperature, and wind speed. As the temperature increased, the influence of the ammonium nitrogen concentration in the floodwater on ammonia volatilization increased. Frogs did not affect the rice yield, rice yield components, nitrogen fertilizer efficiency, or Chinese milk vetch yield. Therefore, rice-frog cultivation has the potential to reduce ammonia in the rice-Chinese milk vetch rotation system, but the long-term effects of this model on ammonia volatilization in paddy fields and its mechanisms require further study.

Control effects of blue and yellow light on Bemisia tabaci on greenhouse cucumbers

HAN Dubin, CHEN Xiangrong, ZHOU Fucai, WU Xiaoxia, ZHAO Ming, CHEN Xuehao

2021, 29(5): 802-808. doi: 10.13930/j.cnki.cjea.200727

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Abstract:
Bemisia tabaci is the main pest of cucumbers; it is critical to control B. tabaci using non-chemical measures for green cucumber cultivation. To explore the control effects of light on B. tabaci in greenhouse vegetables, the relationship between RGB values and the virtual wavelength was used to simulate the colors of different wavelengths on a computer. The light colors repelling B. tabaci were selected according to the selection rate of B. tabaci to different light. On this basis, the changes in the population of B. tabaci on cucumbers treated with the selected light were investigated for the control effects of B. tabaci. The results showed that the color with RGB values of 0, 0, and 255 (wavelength of 470 nm; blue) had the highest repellent rate to B. tabaci. Yellow light (54%) and green light (42%) had a strong trapping effect on B. tabaci. Adding blue light to the environment with yellow and green light could improve the selection of yellow light (68%) and green light (56%). Blue light accelerated the migration of B. tabaci from green to yellow areas. In the greenhouse cucumber field, the population of B. tabaci decreased rapidly after blue light irradiation, and the number of B. tabaci on the cucumber plants decreased significantly with increased light exposure (P < 0.05); a corrected population decline rate of 92.76% was noted after 6 days of blue light irradiation. After 10, 20, and 30 days of treatment, the corrected population reduction rates of B. tabaci on the cucumber leaves increased by 13.80%, 18.17%, and 15.10%, respectively, compared to those without yellow light. These results show that blue light has a strong repellent effect on B. tabaci, and the combination of blue and yellow light improves the control effect. Thus, adding a yellow plate may significantly increase the trapping rates of B. tabaci.

Annual soil salt balance and crop performance under brackish water irrigation during the winter wheat season

GAO Congshuai, SHAO Liwei, YAN Zongzheng, LI Lu, CHEN Suying, ZHANG Xiying

2021, 29(5): 809-820. doi: 10.13930/j.cnki.cjea.200698

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The annual double cropping system of winter wheat-summer maize is a stable cropping system in the low plain of the Bohai Sea. Owing to the shortage of fresh water and the relative abundance of shallow saline water in this region, saline water is used to irrigate winter wheat. The accumulated salt in the soil after the winter wheat season affects the following summer maize season, and the annual soil salt balance is affected by saline irrigation. To address these issues, a continuous 4-year field study was conducted at the Nanpi Eco-agriculture Experimental Station of Chinese Academy of Sciences from 2015 to 2019. Four treatments were set up to irrigate winter wheat once using irrigation water (70 mm) with different total salt contents at the jointing stage, i.e., freshwater 1 g·L^-1 (F), 3 g·L^-1 brackish water (S3), 4 g·L^-1 brackish water (S4), and 5 g·L^-1 brackish water (S5). There was also a treatment without irrigation (rain-fed, CK). The results showed that there was no significant difference in winter wheat yield among the four irrigation treatments, and the average yield with irrigation was 31.6% greater than that of CK. Irrigation using brackish water increased the soil salt content of the top 1 m soil profile during winter wheat harvesting. The soil salt content increase was proportional to the salt content of irrigation water. There were no significant differences in the soil salt contents below 1 m. The necessary irrigation using 70 mm freshwater for the seedling establishment of summer maize after winter wheat harvest reduced the salt content of the top 20 cm soil layer, which created favorable soil conditions for maize growth. No significant differences in summer maize yield were observed among different treatments. With concentrated rainfall during the summer monsoon season, the salt content in the top soil layer (0-40 cm) for the S3, S4, and S5 treatments decreased by more than 30% due to leaching, but the salt content of deep soil did not change. The results showed that the high salt tolerance of winter wheat maintained a stable yield with saline water irrigation. With irrigation at maize sowing and the subsequent summer rainfall, the accumulated salt is leached out of the major root zone to enable the continued use of saline water irrigation for winter wheat in this region.

Lignin metabolism and lodging resistance characteristics of oil flax at different potassium levels

LIU Xuan, DONG Hongwei, GAO Yuhong, YAN Bin, CUI Zhengjun, LI Yue, WU Bing

2021, 29(5): 821-832. doi: 10.13930/j.cnki.cjea.200823

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Abstract:
To explore the effects of potassium supply on the lodging resistance of oil flax, split-plot experiments were conducted with the cultivars 'Longya No. 11' (V1) and 'Dingya No. 23' (V2) and four potassium (K₂O) levels: no potassium[K0, 0 kg(K₂O)·hm^-2], low potassium[K1, 30 kg(K₂O)·hm^-2], medium potassium[K2, 60 kg(K₂O)·hm^-2], and high potassium[K3, 90 kg(K₂O)·hm^-2]. The lignin content, lignin synthesis-related enzyme activities, stem mechanical properties, lodging resistance index of the stem, and yield of oil flax under different potassium supply levels were analyzed. The results showed that under different potassium levels, the relationships between the plant physical characteristics and lodging were mainly observed from the green fruit stage to the maturation stage. The lodging resistance index of oil flax was significantly positively correlated with culm diameter and negatively correlated with plant height and gravity center height. The lignin content of the oil flax stems changed during the growth period and with the potassium supply. The lignin content of V1 and V2 was higher in K2 treatment after potassium application from the seedling stage to the flower stage. Compared with that under K0 treatment, the lignin content of V1 and V2 under K3 treatment increased by 17.68% and 23.25%, respectively, from the green fruit stage to the maturation stage. The effects of cultivar, potassium application, and their interactions on the lignin content at the green fruit stage reached extreme significance (P < 0.01). The K2 treatment increased the phenylalanine ammonia-lyase (PAL) activity of the stem from the budding stage to the green fruit stage and the tyrosine ammonia-lyase (TAL) activity of the V1 cultivar at the budding stage; the K3 treatment increased the TAL activity of the V2 cultivar. Potassium fertilizer significantly affected the cinnamon alcohol dehydrogenase (CAD) activity of the oil flax stem at the green fruit stage. Compared with that in the no potassium treatment, the CAD activity of two cultivars increased by 31.96% and 12.09% on average, respectively, after potassium application. K2 and K1 are the suitable potassium supply levels for peroxidase activity improvement in the V1 and V2 cultivars, respectively. Compared with the indexes at K0, the snapping resistance and lodging resistance indexes of V1 in the K2 and K3 treatments increased by 45.68% and 48.90%, respectively, and by 16.86% and 31.92%, respectively; V2 snapping resistance increased by 84.32% (K2) and 77.50% (K3), respectively, and the lodging resistance index increased by 1.89% (K2) and 14.49% (K3), respectively. Correlation analysis showed that the four lignin related enzymes were positively correlated with lignin content and lodging resistance index at the green fruit stage. After potassium application, the highest grain yield was observed in the K3 treatment, which increased by 10.71% for V1 and by 17.77% for V2 compared with that in the K0 treatment. There was no significant difference in the yield of V1 among different potassium levels. However, the yields of V2 in the K2 and K3 treatments were significantly higher by 12.24% and 17.77%, respectively compared with that of K0. These results indicate that the cultivar is an important influencing factor of the lignin accumulation process of oil flax and that potassium fertilizer has a synergistic promotional effect on the lignin content and the metabolism-related enzyme activities. In this experiment site and the farmlands with similar ecological environments, the use of medium and high potassium fertilizers[60-90 kg(K₂O)·hm^-2] promotes the synthesis and accumulation of oil flax stem lignin, prevents oil flax lodging, and establishes a foundation for a high and stable yield.

Effects and associated regulatory factors of the microbial characteristics of yellow-brown soils following long-term nitrogen fertilization

WANG Jing, WANG Lei, LIU Yaobin, ZHANG Huan, ZHANG Hui, WANG Jidong, WU Jianyan, ZHANG Yongchun

2021, 29(5): 833-843. doi: 10.13930/j.cnki.cjea.200583

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Changes in soil microbial biomass C (MBC) and N (MBN) and their potential regulatory factors were investigated following long-term N fertilizer application since 2011 in a wheat-sweet potato rotation system. In the study, we aimed to provide a theoretical basis for the application of N fertilizers and to improve soil quality and ecological functions. Four N fertilization treatments were used: no fertilizer application (CK), no N-fertilizer application (PK), chemical N-fertilizer application (NPK), and chemical N-fertilizer combined with organic fertilizer application (NPKM). The soil MBC and MBN content, soil potential enzymes activities, and microbial C and N utilization efficiencies were investigated after the harvest of the two crops. Redundancy analysis and structural equation modeling were used to identify the potential biotic and abiotic factors that regulate MBC and MBN in the weakly acidic yellow-brown soils. The results showed that the contents of MBC and MBN and activities of sucrase and urease decreased in the N fertilization treatments. Compared with the NPK treatments, NPKM treatment increased the contents of MBC and MBN and the activities of sucrase and urease. Significantly higher contents of soil organic C (SOC), total N (TN), and mineral N (MN) were detected in the NPK and NPKM treated soils than in the CK and PK treated soils. However, long-term N fertilization significantly decreased the soil pH and efficiencies of microbial C and N utilization. Compared to the wheat season, the sweet potato season showed lower SOC and MN contents and higher MBN content and sucrase activity in the soils under all fertilization treatments. N fertilization strengthened the relationships between MBC and MBN and the sucrase and urease activities. Moreover, variations in the soil MBC and MBN contents and both sucrase and urease activities were regulated by soil pH, SOC and N content, and microbial C and N utilization efficiencies. Soil pH was the key factor driving the soil MBC content. Interactions were found between the activities of soil enzymes and the contents of MBC and MBN. In conclusion, long-term N fertilization decreased the MBC and MBN contents and the invertase and urease activities in yellow-brown soils. However, the combined application of chemical N fertilizers and organic fertilizer alleviated the decline in soil biological properties. The strong microbial C metabolism processes increased the MBN content in the wheat-sweet potato rotation system.

Effects of different mulching on soil water-heat and spring maize yield in newly reclaimed land

WANG Juan, ZHANG Yu, HUANG Chengzhen, ZHUANG Ye, FENG Shaoyuan

2021, 29(5): 844-854. doi: 10.13930/j.cnki.cjea.200627

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With rapid urbanization, the net cultivated land area continues to decrease, and it is important to utilize potential land resources for Chinese food security. To examine the effects of different tillage practices on soil water-heat characteristics and crop growth in newly reclaimed land, we conducted field experiments in 2018 and 2019 with four treatments: plastic film mulching (FM), buried straw layer (BS), buried straw layer with plastic film mulching (F+S), and traditional tillage (CK) as the control. We measured the soil moisture, soil temperature, and growth and yield of spring maize under each treatment. The 2018 results showed that under F+S, BS, and FM, the average soil moisture increased by 24.4%, 16.5%, and 12.6% at 0-20 cm depth, respectively, and by 9.1%, 3.2%, and 3.7% at 20-40 cm depth, respectively, compared with those under CK. Water storage of the soil profile (0-100 cm) under each treatment ranked as FM > F+S > CK > BS in 2018 in maize seedling stage indicating higher water storage under treatments with film mulch than that under no mulching. In 2019, it ranked as F+S > BS > FM > CK. The soil temperature increased under F+S, BS, and FM at each depth, especially at the 5 cm depth, compared with that under CK. The soil temperature (5-25 cm) ranking was F+S > FM > BS > CK. The temperature decreased with increasing soil depth during the growth period; the improved soil temperature effect of mulching and tillage was the strongest at the early growth stage and weakened later. The plant height dynamics were similar among treatments; it improved to a maximum at approximately 70 days after sowing but then reduced and remained stable. The plant height and leaf area index were higher in the treatments with film mulching than those under the no film mulching treatments (P < 0.05). The maize yield under the F+S, BS, and FM treatments were significantly higher than that under the CK treatment in 2018 (P < 0.05), and the yield increased by 17.0%, 13.5%, and 6.6% in 2018 and by 30.5%, 23.9%, and 3.8% in 2019, respectively. Stepwise regression analysis of the yield composition showed that ear length had the greatest effect on maize yield, and yield was positively correlated with the number of ear rows and hundred-grain weight. F+S treatment conferred a comprehensive advantage and effectively regulated the soil water and heat conditions, improved the soil environment, and promoted plant growth and development, resulting in a high yield. Therefore, F+S treatment represents an appropriate mulching and tillage management system for spring maize in a newly reclaimed land.

Effect of planting density on lodging change of spring maize after physiological maturity

ZHANG Dongmei, YANG Ke, JIANG Chunxia, ZHANG Wei, HUANG Mingjing, LIU Huatao, YAN Liuying, LIU Enke, ZHAI Guangqian, WANG Juanling

2021, 29(5): 855-869. doi: 10.13930/j.cnki.cjea.200592

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Heat resources are abundant in the Jinzhong Basin and can be used for dehydration in the late growth stage of spring maize. Lodging resistance is the key limiting factor for direct mechanical grain harvesting in this region. High planting density and harvest delay are important factors for the development and popularization of mechanical grain harvesting technology, but lodging in the late growth stage of maize limits the increase in planting density. One problem with implementing spring maize mechanical grain harvesting technology in the Jinzhong Basin is the selection of an appropriate planting density with high yield and lodging resistance. A field experiment was conducted in the Dongyang Experiment and Demonstration Base of Shanxi Academy of Agricultural Sciences from 2017 to 2019, with three planting densities (6.0×10⁴, 7.5×10⁴, and 9.0×10⁴ plants·hm^-2) and 29 maize cultivars. Changes in lodging at three planting densities were analyzed after the spring maize matured physiologically. The results showed that the average lodging rate for three planting densities at physiological maturity was 0.4% (6.0×10⁴ plants·hm^-2), 1.2% (7.5×10⁴ plants·hm^-2), and 2.5% (9.0×10⁴ plants·hm^-2). After physiological maturity, the average lodging rate increased significantly (P < 0.05). For every 10 days of delay, the lodging rate for three planting densities increased by 0.2 (6.0×10⁴ plants·hm^-2), 0.7 (7.5×10⁴ plants·hm^-2) and 1.5 (9.0×10⁴ plants·hm^-2) percentage points. The national standard GB/T 21962-2008 mentions that the lodging rate of maize should be less than 5% under mechanical grain harvesting conditions. According to the fitting equation, the lodging rate for the 9.0×10⁴ plants·hm^-2 density was higher than 5% after October 2. However, the lodging rates for the 6.0×10⁴ plants·hm^-2 and 7.5×10⁴ plants·hm^-2 densities were less than 5% until November. Therefore, maize grown at 6.0×10⁴ plants·hm^-2 and 7.5×10⁴ plants·hm^-2 could make full use of the local accumulated temperature for dehydration. According to the two-way average method with yield and lodging rate of the harvest period, the varieties and densities with high yield and lodging resistance in three years were always 'Jinkeyu3306' (7.5×10⁴ plants·hm^-2), 'Jinkeyu3306' (9.0×10⁴ plants·hm^-2), 'Dika517' (7.5×10⁴ plants·hm^-2), and 'Huanong887' (7.5×10⁴ plants·hm^-2). The average yield was 14 091.8 kg·hm^-2, and the average lodging rate was 1.7%. These varieties and densities of spring maize were suitable for mechanical grain harvesting in the region. The planting densities of 6.0×10⁴ plants·hm^-2 or 7.5×10⁴ plants·hm^-2 were suitable according to the annual precipitation, irrigation conditions, and the density tolerance of the varieties to achieve high yield and lodging resistance.

The rapid chlorophyll a fluorescence characteristics of different cotton genotypes reflect differences in leaf senescence

XUE Huiyun, WANG Sufang, ZHANG Xin, ZHANG Zhiyong

2021, 29(5): 870-879. doi: 10.13930/j.cnki.cjea.200888

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The light reactions of photosystem Ⅱ (PSⅡ) is greatly associated with the photosynthetic capacity. In order to capture more detailed information describing the status of PSⅡ during leaf senescence and rapidly screen cotton (Gossypium L.) genotypes with different duration of photosynthetic capacity, the PSⅡ photochemistry of the first leaves counted from the stem top of three cotton genotypes ('Baimian1' 'Baimian5' and 'DP99B') presented different leaf senescence progresses in production were examined by chlorophyll a fluorescence (Chl F) analysis during leaf senescence. The results showed that 'Baimian1' 'Baimian5' and 'DP99B' were late, intermediate and early aging types, respectively, based on the performance index of light absorption (PI_ABS). The three genotypes complied with the similar patterns in electrical transferring inhibition accompanying leaf senescence. The depletion of oxygen-evolving complex (OEC) was obvious at the late growth stage. The inhibition of the acceptor side of PSⅡ was greater than that of the donor side. The electron flow that through the light reactions of photosystem Ⅱ and photosystem Ⅰwas significantly limited accompanying leaf senescence. With the duration of leaf senescence, the energy distributed to thermal dissipation and the primary quinone electron acceptors of PSⅡ (Q_A) restoration increased, and correspondingly the energy used to transport an electron into the electron transport chain beyond Q_A^- (the reduction state of Q_A) declined. However, three cotton genotypes showed greater and greater electron transferring inhibition, except the number of Q_A reduction events between time=0 and time to reach maximal fluorescence, in the order of 'DP99B' > 'Baimian5' > 'Baimian1' with the duration of leaf senescence. It can be seen that the chlorophyll fluorescence characteristics can quickly and noninvasively reflect the senescence and the internal physiological mechanism of leaf senescence among different cotton genotypes.

Ecological prediction model of main chemical components of Yuxi flue-cured tobacco 'K326'

ZHU Anqi, JING Yuanshu, HU Baowen, XIE Xinqiao, LI Xiangwei, ZHU Yuncong

2021, 29(5): 880-889. doi: 10.13930/j.cnki.cjea.200860

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Due to national policies and adjustments to the industrial structure, the tobacco industry has implemented "quality optimization, planting regionalization, and technological intelligence" process requirements. To better meet these requirements, understand the quantitative relationships between tobacco chemical components and ecological factors, and improve the intelligence degree of flue-cured tobacco quality evaluation, it is necessary to develop an ecological prediction model of the chemical composition of tobacco leaves that corresponds with the actual production of Yuxi flue-cured tobacco. While prior research has only considered the impact of a single ecological factor (weather or soil) on the chemical composition of tobacco leaves, this study used the main chemical components (nicotine, total sugar, reducing sugar, total nitrogen, potassium, and chlorine) of flue-cured tobacco 'K326' in nine typical locations from 2009 to 2017 in the Yuxi area and ecological data (weather and soil) corresponding to the different growth periods. These factors were analyzed to obtain a comprehensive index of the influential ecological factors and to establish an ecological prediction model of the chemical composition mechanisms of tobacco leaves. Using the ecological data from 2018, the content of main chemical components in the tobacco leaves was predicted and compared with the observed values. Data from 90 flue-cured tobacco samples were used to calculate the maximum information coefficient (MIC) to screen the input variables; this method ensures the integrity of the input parameters and is not limited to specific function types (e.g., a linear function) as long as there is a significant functional relationship between the ecological factors and chemical components. To overcome the shortcomings of the back-propagation (BP) neural network (i.e., it is easy to fall into local minima and slow convergence speed), the Grey Wolf optimizer was used in the modeling process to optimize the weights and thresholds of the neural network. To establish an intelligent algorithm for the tobacco leaf chemical composition ecological prediction model, the absolute error was used to intuitively show the difference between the simulated value of the BP neural network optimized by the Grey Wolf algorithm and that before optimization. The results showed that the prediction model of the mechanism algorithm could judge the degree of influence of the ecological factors on the tobacco chemical composition and indicate whether the influence was positive (promoting effect) or negative (adverse effect) by the size and the positive and negative values of the comprehensive index. The average R² value of the ecological prediction model of the mechanism algorithm was 0.29, the average root mean square error (RMSE) was 0.13, and only the RMSE of the reducing sugar was slightly greater than 0.2. These results indicated that the model understood the chemical composition characteristics of Yuxi flue-cured tobacco under particular ecological conditions in a given year. The absolute error of the ecologyical prediction model of the optimized intelligent algorithm was significantly smaller than that before optimization, indicating a better simulation effect for the optimized intelligent algorithm of the ecological prediction model. All R² values were greater than 0.95, and the R² values of the other prediction models (except for total nitrogen) were as high as 0.99. This suggested a very high degree of fit and that the model did well to explain the variability in the chemical composition; each RMSE was less than 0.1, and some values were less than 0.01, suggesting accurate prediction results.

Advances in the intercropping remediation of heavy metal polluted soil

GUO Siyu, WANG Haijuan, WANG Hongbin

2021, 29(5): 890-902. doi: 10.13930/j.cnki.cjea.200635

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Phytoextraction is an efficient, novel, economic, green, and low-risk method for metal-polluted soil remediation that harvests metal hyperaccumulators to remove heavy metals from the soil. The cultivation of a single hyperaccumulator for the remediation of heavy metal-polluted soil not only interrupts agricultural production, leading to economic loss, but also results in low remediation efficiency owing to many disadvantages, such as low biomass and long remediation cycle. As a traditional agronomic management method, intercropping can improve the utilization efficiency of resources and increase the quality of co-planted crop species by using the principles of ecological niche and biodiversity. For the remediation of moderately or lightly metal-polluted soil, an intercropping system can be used to increase the concentrations of heavy metals in hyperaccumulators by regulating the growth and development of the hyperaccumulators and crops. Furthermore, the antioxidative ability of the hyperaccumulators and crops is also improved, which decreases the contents of peroxidation products, such as malondialdehyde and reactive oxygen species, in the cell membrane lipids. Intercropping generally enhances low molecular weight organic acid (LMWOA) secretion from the roots of heavy metal hyperaccumulators, decreases the pH value of rhizospheric soil, increases the activity of heavy metals, and consequently promotes heavy metal uptake by hyperaccumulators. However, LMWOA secretion from the crop roots is inhibited, resulting in decreased heavy metal uptake and improved crop yield and quality. Decreased heavy metal uptake by crops reduces the risk to human health, and the increased metal accumulation in hyperaccumulators enhances the removal of heavy metals from the soil. Moreover, the benefits to farmers are not affected or may even increase when using intercropping remediation technology. Therefore, the land utilization rate and economic benefits increase based on the "production while remediated" approach. This study systematically reviewed changes in biomass, physiological and biochemical responses, heavy metal uptake, translocation, and accumulation in hyperaccumulators and crops, as well as the effects of intercropping on soil environmental quality. While many studies examining the effects of intercropping systems on heavy metal hyperaccumulators and crops had focused on growth and development, metal uptake, translocation, accumulation, and physiological and biochemical responses to heavy metal stress, little information was available on the underlying molecular mechanisms of the physiological and biochemical processes. Additionally, the effects of intercropping on the microbial composition of the rhizosphere of heavy metal hyperaccumulators and crops and the related ecological implications and main function mechanisms remained unclear. From these unsolved questions, future perspectives in this field, such as the signal transduction and molecular mechanisms of the intercropping system of hyperaccumulators and crops, the different and functional mechanisms of rhizosphere microorganisms of two plants, and how to construct an efficient intercropping system to improve the remediation efficiency of heavy metal-polluted soil, were also proposed.

Effects of night warming and soil copper contamination on copper retention in wheat

DENG Yi, KOU Taiji, LAI Lukuan, XU Xiaofeng, WANG Xugang, MA Ming

2021, 29(5): 903-909. doi: 10.13930/j.cnki.cjea.200624

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Abstract:
Grain production in China is subject to the stresses of copper (Cu) contamination in agricultural soils and asymmetric climate warming; it is vital to understand the effects of these dual pressures on crop growth and production. Since asymmetric climate warming and soil Cu accumulation potentially affect wheat production in China, it is important to analyze the effects of night warming on the uptake and distribution of Cu in wheat under Cu pollution stress. A pot experiment was conducted during the 2018-2019 wheat growth season on the Experimental Farm of the Henan University of Science and Technology (34°35N, 112°24E), an agricultural area with an annual average temperature of 14.86℃ and annual average precipitation of 600 mm. The experiment had two temperature treatments (a control group and night warming under a passive night warming system) and two levels of Cu pollution (6 mg·kg^-1[control] and 155 mg·kg^-1[Cu pollution]). The Cu-polluted soils in the pots were collected from a Cu single factor contaminated site at the Kaiyuan Campus Farm of Henan University of Science and Technology. The crop responses (vs. Luohan 11) to night warming and Cu contamination with respect to yield, biomass of different aboveground tissues, and content, accumulation, and translocation coefficients of Cu in the aboveground tissues were investigated. The results showed that night warming significantly increased the crop straw, spike, aboveground, and total biomasses by 25.1%, 21.3%, 22.7%, and 22.3%, respectively, and could alleviate the inhibition of Cu pollution on wheat growth. Night warming significantly increased the straw Cu content by 26.3% in the control group, but significantly decreased the straw Cu content by 13.9% in the Cu pollution groups. In the control group, night warming significantly increased Cu accumulation by 14.7%-56.5% in the straw, spike, aboveground, and whole plant. In the Cu pollution groups, night warming increased Cu accumulation by 12.1%-22.8% in the roots, spikes, and whole plant. Night warming and Cu pollution affected the migration and utilization of Cu in different tissues. Night warming significantly increased the Cu translocation coefficient from root to stem and decreased the stem to leaf and stem to spike Cu translocation coefficients in the control. Night warming significantly decreased Cu transport from root to stem, did not affect Cu transport from stem to leaf, and increased Cu transport from stem to spike in the Cu pollution groups. Cu pollution changed the response law of wheat Cu absorption and utilization as it related to night warming. This study illustrated that night warming improved wheat production and alleviated the harmful growth-related effects of Cu stress, however, if increased potential risk of Cu pollution on grain crop quality.

Effects of aggregate size on kinetics of glyphosate degradation in red soil

XIN Longchuan, WU Wenxue, XUE Sha, FU Gejuan, CHEN Yanhua, WANG Xuexia, LIU Dongsheng, YANG Xiaomei

2021, 29(5): 910-921. doi: 10.13930/j.cnki.cjea.200686

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Abstract:
With intensive glyphosate application, its residues and consequent risks of soil health and ecological environment safety have received greater attention. The degradation kinetics of glyphosate in red soil aggregates with different sizes, as well as the interaction between physical and chemical properties of soil aggregates and the degradation of glyphosate, have rarely been studied. Thus, in this study, the degradation characteristics of glyphosate in red soil aggregates with different sizes were observed under laboratory conditions by particle pre-sieving, incubation in a controlled climatic chamber, and residue analysis via liquid chromatography-tandem mass spectrometry. The physical and chemical properties of the soil aggregates, such as contents of organic matter, total phosphorus, and available phosphorus, were tested according to the national approved methods and standards. The relationships between the physical and chemical properties of the aggregates and the degradation of glyphosate were further analyzed and compared in the same observation day. The results showed that 1) the glyphosate content decreased in the different aggregate particles during the observation period, following the single first-order kinetic degradation model. However, no significant differences were observed among different aggregate sizes. The half-life time of glyphosate in the different red soil aggregates ranged from 15.8 to 20.6 d, with a longer half-life time in the smallest aggregates (< 0.25 mm, 20.6 d). The aminomethylphosphonic acid (AMPA) content, the main metabolite of glyphosate, increased immediately and peaked on the 5^th day after glyphosate application, but no differences were found among different aggregates. However, the AMPA content changed and declined significantly in different aggregates after the 5^th observation day (P < 0.05). The contents of organic matter, total nitrogen, total phosphorus, and available phosphorus in different aggregates varied greatly, especially the available phosphorus content, which decreased with glyphosate degradation. 2) Correlation analysis and principal component analysis of glyphosate, aggregate size, and their properties showed that the residual glyphosate was significantly positively correlated with the content of available phosphorus (P < 0.05), and the AMPA content was significantly positively correlated with the activities of acid phosphatase and N-acetylamino-β-glucosidase (P < 0.05). There were no significant relationships between the aggregate size and the residuals of glyphosate, but a significant positive correlation was observed between the aggregate size and the AMPA content (P < 0.05). Furthermore, during the whole period of glyphosate degradation, the organic matter content, acid phosphatase, N-acetylamino-β-glucosidase, and β-glucosidase showed a significant negative relationship with the soil aggregate size (P < 0.05). In conclusion, the characteristics of the red soil aggregates affect the degradation kinetics of glyphosate, as well as the persistence of AMPA, especially the residuals in the smallest aggregates (< 0.25 mm). The contents of glyphosate and AMPA in the red soil aggregates were still high after 30 days, which may affect soil health. Glyphosate degradation was also closely related to phosphorus in the soil. Therefore, the fate of glyphosate under conditions of phosphorus deficiency or abundant soil should be explored to provide detailed information on glyphosate risk assessment in red soil.

Effect of crushing degree and returning method on straw combustion

LI Chao, CHENG Kaikai, LIAO Yulin, GUO Lijun, WEN Li, TANG Haiming, TANG Wenguang, WANG Ke, CHU Fei, ZHONG Lingtao, JIANG Haitian, XIAO Xiaoping

2021, 29(5): 922-928. doi: 10.13930/j.cnki.cjea.200668

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Abstract:
Rice straw burning is a major source of pollutants emissions in China. Its contribution to the emission of various pollutants is much higher than that of corn and wheat straws, which has resulted in tremendous pressure on the surrounding urban environment and residents' health. Simultaneously, rice straw will become the most important source of organic fertilizer for rice production in the future. To fundamentally forbid rice straw burning and promote rice straw return to the field, in this study, we set the current conventional mode of rice harvest, including rice straw stripped to the field without crush (T1) and with moderate crush (T2) as controls, and crushed rice straw stripped to the field (T3) and evenly returned to the field (T4) as the treatments. The treatments relied on a self-invented device that crushed and homogeneously scattered the rice straw in field tests. The field simulation tests aimed to study the influence of different crushing degrees and returning methods on the rice straw combustion characteristics. The results showed that the scattering homogeneity and returning density of rice straw increased significantly with increased crushing degree, but the returning thickness of rice straw significantly decreased. The rice straw average length of T4 was 5.3 cm, which was only 13.6% and 36.8% of T1 and T2, respectively. The scattering homogeneity of T4 was 87.4%, which was 49.7% and 42.0% higher than that of T1 and T2, respectively. The thickness of rice straw returned to the field of T4 was 2.7 cm, which was only 22.1% and 27.8% of T1 and T2, respectively. The density of rice straw returned to the field of T4 was 17.6 kg·m^-3, which was 88.3% and 17.3% higher than that of T1 and T2, respectively. Under the rice straw strip-returning modes (T1, T2, T3), the higher the degree of rice straw crushing, the slower the decline in moisture content, the longer the combustion time, the lower the combustion rate, the slower the combustion speed, the higher the ash content, and the less sufficient the combustion. Although T4 can accelerate the decrease in rice straw moisture content by homogeneous scattering, the combustion time, combustion speed, and ash content were only 0.3%, 6.0%, and 1.7%, respectively. This was significantly lower than those in the other treatments, indicating that the rice straw was almost unburned. These results indicate that the rice straw could not be burned when crushed and evenly thrown to the field, which was beneficial for achieving a ban on rice straw combustion. Therefore, local government functional departments need only to compulsorily install the devices for crushing and homogeneously scattering rice straw with the combine harvester, which will completely prohibit the burning of rice straw. This will promote the fertilization of paddy soil and greatly reduce the difficulty and costs of agricultural law agencies enforcing rice straw burning bans.

Impact of farmers' scarcity perception and overdrawn cognition on efficiency of groundwater irrigation: based on the survey data of 457 farmer households in groundwater overdraft area of Hebei Province

LIU Weizhe, WANG Xiqin

2021, 29(5): 929-936. doi: 10.13930/j.cnki.cjea.200691

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Abstract:
In recent years, with economic and social development, shortages in the surface water supply have led to a large-scale shift in groundwater exploitation and environmental problems caused by the overexploitation of groundwater. As the main water user, agricultural irrigation must reduce waste and improve efficiency. Based on the survey data of 457 farmer households in Hebei Province, this study used a stochastic frontier model to calculate irrigation water efficiency. We rebuilt the index system of water scarcity perception and groundwater overdraft cognition based on relevant research and empirically analyzed the effect of farmers' perceptions of scarcity and overexploitation on irrigation water efficiency while controlling for individual, family, and production characteristics. The results showed that the average irrigation water use efficiency of farmers was 0.59, the main distribution range was 0.40-0.80, with which farmer households accounting for 87.74% of the total. indicating there was a certain level of water waste (water use efficiency had a large scope for improvement). In scarcity perception, quantity perception, water level perception, and scarcity expectation had significant positive effects on irrigation water efficiency. In the cognition of groundwater overdraft, hazard cognition and environmental protection cognition promoted irrigation water efficiency. The number of farming years and education level were positively correlated with irrigation water efficiency. Transferred land had higher irrigation water efficiency than self-owned land. The fragmentation of cultivated land and the distance from irrigation facilities significantly reduced irrigation water efficiency. Based on the above conclusions, in this study, we recommend the following suggestions to improve agricultural irrigation efficiency in Hebei Province: conduct water situation education and improve the farmers' perception of water quantity and water level information. It is important to improve the dynamic monitoring mechanisms of water quantity and the water level, strengthen publicity and education on the current status of water shortages and future development, help farmers establish water-saving concepts. The publicity and education of groundwater environmental protection should be widely popularized, and the comprehensive cognition level of groundwater exploitation for farmers enhanced. Comprehensive measures for groundwater over mining should be widely publicized, and farmers should be mobilized to support and participate in the comprehensive treatment of groundwater over mining. Farmers should also consciously reduce waste and improve the efficiency of irrigation water.

2021 Vol. 29, No. 5