2020 Vol. 28, No. 12

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Agroecosystem and Its Management
The effects of farmland shelterbelts on surface arthropod distribution: A case study in Changtu County, China
BIAN Zhenxing, YANG Yibo, GUO Xiaoyu, ZHANG Yufei, YU Miao
2020, 28(12): 1835-1846. doi: 10.13930/j.cnki.cjea.200786
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Improving farmland biodiversity is important for ecological agriculture. To explore how well farmland shelterbelts protect biodiversity, eight farmland shelterbelt units (unit=one field parcel; shelterbelt types:complete, incomplete, or extinct) in Jinjia Town, Changtu County, Liaoning Province, China were selected, and the surface arthropod distribution in adjacent farmlands was investigated using pitfall traps. Surface arthropods were sampled at 0, 50, 100, 150, and 200 m from the shelterbelt, and the shelterbelt vegetation characteristics were recorded. Analysis of variance and community ordination were used to analyze how the shelterbelt type, distance gradients, and shelterbelt vegetation structure affected the surface arthropod distribution. The results showed that the surface arthropod abundance was significantly higher in fields adjacent to complete and incomplete shelterbelts. The shelterbelt type had no significant effect on diversity; however, the surface arthropod community composition on the farmland adjacent to complete and incomplete shelterbelts differed from the extinct shelterbelts. The abundance gradient variation was significant in fields adjacent to complete and incomplete shelterbelts, demonstrating a low to high variation trend with away from shelterbelts. In all units, the diversity decreased as the distance toward the edge increased, and a significant edge effect was observed. Redundancy analysis (RDA) and Monte Carlo tests showed that the herb layer species abundance and the shelterbelt tree coverage were the primary factors affecting arthropod community distributions, accounting for 35.4% of the total surface arthropod population variation. Arthropod responses to the shelterbelt vegetation community significantly differed based on the species, carabids, and spiders present. The primary natural enemy of the local agricultural landscape was closely related to the shelterbelt vegetation structure; the carabid species diversity was positively associated with herb layer abundance, and the spider family diversity was positively associated with tree coverage. Farmland shelterbelts (a non-cropped habitat) significantly increased the number of surface arthropods in adjacent fields but did not affect species diversity. The herb layer abundance and shelterbelt tree coverage had a positive effect on natural enemy diversity (e.g., carabids and spiders). Strengthening agricultural landscape woodlands, such as increasing upper tree coverage and understory vegetation, improves the habitat quality and conserves farmland biodiversity, thereby promoting sustainable agriculture.
Effects of grazing on temperate grassland ecosystem based on a meta-analysis
ZHAN Tianyu, SUN Jian, ZHANG Zhenchao, LIU Moucheng
2020, 28(12): 1847-1858. doi: 10.13930/j.cnki.cjea.200383
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The temperate semi-arid grassland in Inner Mongolia is primarily used for grazing, which directly and indirectly affects material circulation and energy flow. Grazing intensity plays a decisive role in the health status and direction of grassland succession. Data from 40 studies about Inner Mongolia grassland grazing intensity were analyzed via a meta-analysis. The results showed that compared to the non-grazing grassland, light grazing did not affect the above- and below-ground biomass, soil total nitrogen, and total phosphorus, but significantly increased (P < 0.05) the soil organic carbon (3.60%), microbial carbon (7.80%), bacteria (11.40%), and fungi (10.83%). Moderate grazing did not affect the below-ground biomass and the number of microorganisms, but significantly reduced (P < 0.05) the above-ground biomass (21.62%), soil organic carbon (4.44%), total nitrogen (2.15%), total phosphorus (8.35%), and microbial biomass nitrogen (6.76%). Heavy grazing significantly decreased (P < 0.05) the above- and below-ground biomass (39.72% and 16.30%, respectively), soil organic carbon (7.62%), total nitrogen (6.46%), total phosphorus (8.03%), microbial biomass carbon (8.76%), bacteria (12.92%), and actinomyces (18.27%). These findings suggest that light grazing benefits soil fertility and grassland productivity; however, the grassland ecosystem's functional capacity weakens once the grazing intensity exceeds a certain threshold. This information is useful for adapting management strategies to prevent grassland degradation.
Spatial-temporal patterns of the food provisioning service based on calories in Guangxi, China
XIE Yuchu, ZHANG Suxin, LIU Qiaozhen, PAN Xinchao
2020, 28(12): 1859-1868. doi: 10.13930/j.cnki.cjea.200285
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As society and food consumption changes, more people are paying attention to the food supply chain as part of a healthier lifestyle. Understanding the spatial-temporal characteristics of food provisioning services is important for policy decisions regarding production capacity, especially in places with unstable food availability and unbalanced nutrition. The food provisioning service of the Guangxi Zhuang Autonomous Region (GZAR) was assessed based on calories from 2000 to 2015. The nutrition consumption standards were also used to calculate food provision calories. The results showed that in 2015, the caloric output totaled 4.46×1014 kJ; calories from grains and cereals were the most abundant, followed by sucrose, and then oils (grains and sucrose were 85.47% of the total caloric intake). From 2000 to 2015, calories from sucrose, fruits, and vegetables increased significantly, while the calories from grains and oils fluctuated. The overall food provision increased steadily, resulting in a surplus; the calories per person increased from 7.87×106 kJ (2000) to 9.31×106 kJ (2015). In 2015, the total and surplus calories supported population sizes of 103.28 million and 53.03 million, respectively (with a 'well-off' quality standard), which exceeded the total GZAR population (55.18 million). However, the proportion of calories from grains decreased yearly and was only 52.2% by 2015. In 23.3% of the counties and cities, less than 50% of the calories from grains were provided, indicating that calories were unevenly distributed, and some counties had a low grain-calorie capacity. The high caloric output areas were in the plains, basins, and valleys of the central-southern GZAR, where sufficient light, heat, flat fertile land, and water resources were available (e.g., Xingbin District, Wuming and Hengxian counties, and the cities of Guigang and Qinzhou). The low caloric output areas were in the northwest mountain region and urban areas. Therefore, protecting croplands in the high-yield regions and developing unused lands for sustainable food provision are important for the GZAR. Optimizing agricultural production for the local conditions, improving the production management and large-scale production capacity levels, and strengthening the regional grain trade may contribute to the sustainable development and security of the GZAR food supply.
Crop Cultivation and Physiological Ecology
Ammonia emission characteristics and emission coefficients of wheat and corn rotation cropland under different fertilization methods in lime concretion black soil
LYU Jinling, WANG Xiaofei, LI Taikui, KOU Changlin
2020, 28(12): 1869-1879. doi: 10.13930/j.cnki.cjea.200479
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Soil type affects farmland ammonia volatilization, but few studies have examined ammonia volatilization characteristics and emission coefficients. Therefore, the accurate inventory of regional farmland soil ammonia emissions is disadvantaged. Lime concretion black soil found in southern Henan, China, was used to explore the ammonia volatilization characteristics of winterwheat-summer maize-rotated cropland by the closed-sponge method. The soil was unfertilized (CK) or treated with traditional fertilizer (TR), optimized fertilizer (OPT), re-optimized fertilizer (ZOPT), or slow-controlled fertilizer (HK), and the ammonia emissions coefficient was determined. The results showed that the winter wheat and summer maize ammonia volatilization amounts using the traditional fertilizer treatment were 11.1 and 13.4 kg·hm-2, respectively. Summer maize ammonia emission was 21% higher than winter wheat, indicating that the summer maize season was a high-volume period. Winter wheat and summer maize treated with HK and ZOPT had the lowest ammonia emission coefficients (HK:1.7% for winter wheat, 1.5% for summer maize; ZOPT:2.1% for winter wheat, 2.6% for summer maize; P < 0.05), the OPT treatment had moderate coefficients (2.6% for winter wheat, 3.6% for summer maize), and the TR treatment had the highest coefficients (3.6% for winter wheat, 4.7% for summer maize). The ammonia emissions fertilization gradients and fertilization amounts were plotted, and the ammonia volatilization amounts under variable fertilization treatments were linear (R2:0.931 for winter wheat, 0.934 for summer maize). These results may help to improve nitrogen fertilizer use and the ammonia emission inventory and provide basis for nitrogen emission estimation of winter wheat-summer maize rotation in lime concretion black soil croplands.
The effects of deep application of nitrogen fertilization on ammonia volatilization in a winter wheat/summer maize rotation system in the North China Plain
HU Manman, DONG Wenxu, WANG Wenyan, Gokul Gaudel, Peter Mosongo, HU Chunsheng
2020, 28(12): 1880-1889. doi: 10.13930/j.cnki.cjea.200290
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The deep application of nitrogen fertilizers can reduce soil ammonia volatilization, but no annual systematic study in a winter wheat/summer maize rotation system exists. Nitrogen fertilizer was deeply applied to soil from a winter wheat/summer maize rotation system to determine the effects on ammonia emissions and optimize farmland fertilization. Five treatments were used from October 2018 to October 2019:no fertilization (CK), conventional fertilizer surface-application (T1), slow-release fertilizer surface-application (T2), twice layered deep-application of slow-release fertilizer (T3), and single layered deep-application of slow-release fertilizer (T4). Ammonia volatilization primarily occurred in the corn top-dressing season and accounted for 84.84% of the annual ammonia volatilization. The cumulative amounts of annual ammonia volatiles were 22.75 (T1), 6.17 (T2), 2.25 (T3), and 0.55 kg·hm-2(T4), accounting for 4.86%, 1.32%, 0.48%, and 0.16% of the total fertilizer application, respectively. The slow-release fertilizer treatments reduced the ammonia volatilization loss by 72.88% (T2), 90.11% (T3), and 96.30% (T4) compared to T1. The single deep application treatment (T4) avoided the summertime high soil ammonia volatilization period, and the cumulative annual ammonia emissions were comparable to the unfertilized emissions (0.43 kg·hm-2). The annual yields were 8.31 (CK), 13.20 (T1), 12.66 (T2), 14.42 (T3), 14.22 (T4) t·hm-2; and compared with T1, the slow-release fertilizer deep application increased the crop yield by 9.25% (T3) and 7.75% (T4). The surface application of slow-release fertilizer (T2) slightly decreased the yield but significantly reduced the ammonia volatilization amount. In conclusion, the deep application of slow-release nitrogen fertilizer improved crop yield and reduced soil ammonia emissions, and was shown to be a simple, efficient, and environment-friendly fertilization method.
Wheat and faba bean intercropping to improve yield and response to nitrogen
REN Jiabing, ZHANG Mengyao, XIAO Jingxiu, ZHENG Yi, TANG Li
2020, 28(12): 1890-1900. doi: 10.13930/j.cnki.cjea.200332
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The wheat and faba bean intercropping system improves crop yield. However, there are few systematic reports on the relationship between the yield advantage and the interspecific interaction and its response to nitrogen fertilizer. Nitrogen applications were tested to improve nitrogen management in intercropped legumes and grasses, gather information on efficient nutrient use, and determine the interspecific influence on wheat and faba bean yields. The field positioning test was conducted from 2015 to 2017 to study yield advantages and interspecies relationship of wheat||faba bean intercropping system under various nitrogen application levels:no nitrogen (N0), low nitrogen (N1, 90 kg·hm-2), conventional nitrogen (N2, 180 kg·hm-2), and high nitrogen (N3, 270 kg·hm-2). Compared with monocropped wheat, the intercropped wheat yield was significantly higher in all treatments[2016:24.55% (N0), 20.71% (N1), 19.92% (N2), 16.77% (N3); 2017:35.89% (N0), 28.63% (N1), 23.32% (N2), 18.25% (N3)]. The mono and intercropped faba bean yields were both around 4 000 kg·hm-2. The land equivalent ratio of the intercropping system under different nitrogen levels was N0 > N1 > N2 > N3 > 1, and the average intercropping productivity reached 5 023 kg·hm-2 in two years. The intercropped wheat dry matter accumulation ratio after flowering, transfer rate, and contribution rate increased by 37.68%, 7.95%, and 10.59%, respectively, and the intercropped faba beans increased by 19.66%, 41.43%, and 17.64%, respectively, compared with the monocultured crops. The increase rate decreased as nitrogen increased, and the intercropped wheat dry matter accumulation ratio after flowering was significantly different at N2 and N3 levels in 2016. The average wheat relative interaction indexes were 0.13 (N0), 0.11 (N1), 0.10 (N2), and 0.08 (N3), showing mutually beneficial effects, but the faba bean indices were -0.008 (N0), -0.03 (N1), -0.08 (N2), and -0.08 (N3), indicating a competitive effect. The average wheat relative competition intensity values were -0.19 (N0), -0.08 (N1), 0.21 (N2), and 0.32 (N3), indicating intraspecific competition at low nitrogen levels (N0, N1) and interspecific competition at conventional (N2) and high (N3) nitrogen levels. All faba bean values indicated intraspecific competition:-0.75 (N0), -0.75 (N1), -0.66 (N2), and -0.65 (N3). The relative interspecific competitiveness values of wheat versus faba beans were 0.51 (N0), 0.54 (N1), 0.56 (N2), and 0.58 (N3), suggesting different degrees of competitive advantage. Competitiveness was significantly correlated (a quadratic curve) with the above-ground dry matter of the intercropping system. The maximum mixed dry matter mass of the intercropping system (16 093 kg·hm-2) was reached when the wheat versus faba bean interspecific competitiveness value was 0.629 2. Wheat and faba bean intercropping reduced the interspecific competition intensity in a low nitrogen environment (N0, N1). It also expanded the mutually beneficial effects and competitive advantages of wheat and increased the dry matter accumulation ratio after flowering and the dry matter contribution rate of intercropping crops. The maximum competitive advantage of intercropped wheat was at the conventional nitrogen level (N2, 180 kg·hm-2).
Medicago ruthenica (L.) Sojak. cv. Zhilixing response and adaptation strategy to drought stress and rehydration
WU Rina, SHI Fengling, XU Bo
2020, 28(12): 1901-1912. doi: 10.13930/j.cnki.cjea.200308
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The effect of drought stress and rehydration on Medicago ruthenica (L.) Sojak cv. Zhilixing morphological structures, physiological metabolism, and matter distribution were investigated to determine the adaptation strategy in an arid environment. Seedling-stage M. ruthenica (with 6-8 leaves) were subjected to continuous drought stress for 12 days and then re-watered for 4 days; samples were collected from the control group (CK), after 9 and 12 days of drought stress, and 4 days after rehydration. Compared with the CK, the stoma opening rate decreased, while the stoma and epidermis cell densities increased by 48.5% and 36.6%, respectively. Smaller and denser epidermal cells formed. The malondialdehyde (MDA) content increased gradually during stress period. Superoxide dismutase activity (SOD), peroxidase activity (POD), and contents of chlorophyll, soluble sugar, soluble protein, and proline first increased and then decreased with prolonged drought. Total biomass also first increased then decreased, reaching the maximum after 9 days (0.433 7 g; 16.4% increase). The distribution of the above-ground biomass was higher than the under-ground biomass, and the under-ground biomass proportion increased with drought, while the opposite effect was observed with the above-ground biomass. After re-watering, all of the physiological and biochemical indexes recovered or exceeded those of the control, indicating strong rehydration sensitivity and resilience. M. ruthenica adaptation to drought stress and rehydration was divided into three periods:active adaptation, passive adaptation, and re-watering. The physiological parameter plasticity index was 0.16, 1.33 times greater than the morphological parameter index, during the active adaptation period. Drought stress adaptation was achieved by altering the antioxidant and osmotic regulation systems to reduce water loss, improving water retention and absorption efficiency, and maintaining the water absorption and loss balance. The morphological parameter plasticity index was 0.24, 1.31 times greater than the physiological parameter index, during the passive adaptation period. M. ruthenica sacrificed biomass and reduced pigments to aid survival. The root-shoot ratio (25.9%), stomatal opening rate (29.7%), and stomatal and epidermal cell density (24.2% and 16.3%, respectively) were higher than those in the CK during the re-watering period. These characteristics promoted rapid water recovery, absorption capacity, and water transport efficiency. Morphological and physiological changes allowed M. ruthenica to adapt to drought stress and rehydration, contributing to its survival in arid conditions.
The effects of chemical pesticide reduction on the occurrence of diseases, pests, weeds and rice yield
YI Jun, FU Huijuan, LI Xingyue, ZHU Conghua, LI Qiyong, ZHANG Hong
2020, 28(12): 1913-1923. doi: 10.13930/j.cnki.cjea.200297
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A split-field test was conducted to explore how chemical pesticide reduction affects rice yield. Two weed control methods (shallow rotary tillage with conventional herbicide amounts and deep tillage with 30% less herbicide; main factor), two disease and pest control methods (conventional insecticide and fungicide amounts and plant activator protein application with 30% less insecticide and fungicide; sub-plot factor), and two seedling treatment methods (transplanting with and without pesticides; split-split plot factor) were used to investigate rice diseases, pests, weeds, and dry matter production. The results showed that deep tillage significantly decreased the weed numbers and weight compared to the shallow rotary tillage, and the white panicle rate (caused by the borer) was also significantly lowered. Rice plant leaf blast was significantly reduced by using conventional shallow rotary tillage after transplantation with pesticides or the spraying of plant activator protein. Both the weed control methods and the disease and pest control methods had significant effects on the stem sheath dry matter accumulation, and stem sheath dry matter transformation. The interactions between the weed control methods, disease and pest control methods, and seedling treatment methods significantly affected the stem sheath exportation and dry matter transformation. After the plant activator protein application, the stem sheath dry matter increased by 4.0% to 19.4% at the full heading stage. When deep tillage was used, the stem sheath dry matter increased by an average of 7.1%. However, the stem sheath exportation and dry matter transformation decreased from the full heading to maturity stages. Correlation analysis showed that the rice yield was significantly negatively correlated with weeds (tillering and grain-filling stages) and leaf blast (tillering stage). No effect on the rice yield was observed when strategies such as deep tillage, transplantation with pesticides, or the spraying of plant activator protein were employed with 30% less pesticide. These results suggest that the chemical pesticide amount could be reduced during planting by using control methods such as deep tillage, transplantation with pesticides, or the spraying of plant activator protein, and that the rice yield would remain stable.
Corn disease recognition based on the Convolutional Neural Network with a small sampling size
YANG Mingxin, ZHANG Yaoguang, LIU Tao
2020, 28(12): 1924-1931. doi: 10.13930/j.cnki.cjea.200375
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Crop disease management influences yield and quality, yet identifying corn diseases is still difficult. High labor costs, small number of sample, and uneven disease distributions contribute to the difficulty. We propose an improved Convolutional Neural Network (CNN) model based on the transfer learning method for disease identification. The sample image set was enhanced by rotation and roll-over, then the migrated MobileNetV2 model was used to train the image data set for corn diseases. The Focal Loss function was used to improve the neural network loss function, and the Softmax classification method was used for corn disease image recognition. The training set accuracy, validation set accuracy, weight, run time, and the number of parameter in six models were experimentally compared. The verification set accuracy rates were 93.88% (AlexNet), 95.48% (GoogleNet), 91.69% (Vgg16), 97.67% (RestNet34), 96.21% (MobileNetV2), and 97.23% (migrated MobileNetV2). The migrated MobileNetV2 was 97.23% accurate and weighed 8.69 MB. Confounding the MobileNetV2 model improved the recognition accuracy by 1.02% and reduced the training speed by 6 350 seconds compared to the unconfounded model. The migrated MobileNetV2 model had the best corn disease recognition ability with a small sampling size; improved convergence speed, reduced model calculations, and greatly improved the recognition time.
Agricultural Resources and Environment
The application of crop phytoliths for reviewing occluded organic carbon
YUAN Faying, WANG Linjiao, SHENG Maoyin
2020, 28(12): 1932-1940. doi: 10.13930/j.cnki.cjea.200307
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Farmland ecosystems are important for maintaining terrestrial ecosystems and environmental homeostasis. As farmland ecosystems develop and evolve, change information is stored in the environment such as in phytoliths, which are stable, non-crystalline minerals in the soil that can indicate climate change. Phytolith analysis has been used for agricultural archaeology, paleoclimate reconstruction, and for estimating biogeochemical cycles and global carbon sequestration potential. Crop cultivation has a long history, and crops are globally distributed. Therefore, studying crop phytoliths and phytolith-occluded carbon is useful for exploring the origin and development of agriculture, estimating farmland ecosystem carbon sequestration, and responding to global climate change. The content and distribution of phytolith-occluded carbon, the phytolith carbon sequestration potential, and the contribution to global carbon sequestrations were analyzed (by literature review and phytolith morphological and archaeological information) to determine future crop phytolith research directions. The results showed that crops had differing phytolith characteristics, and most crop phytolith research had been completed in the family Gramineae. The crop phytolith carbon content was correlated to crop's carbon sequestration capacity and efficiency, and the phytolith-occluded carbon content may also be affected by the growth environment and plant genotypes. The climate, surface vegetation, and soil environment of the ecosystem had direct and indirect effects on the regional phytolith carbon sequestration potential. Significant differences in carbon sequestration between farmland crops were observed. Applying a silicon fertilizer or a silicon-phosphorus compound fertilizer and planting crops with high silicon content can significantly improve the carbon sequestration potential. Future studies should investigate the phytolith carbon sequestration of specific crops to identify past carbon sequestration levels and compare them with the current potential. The plant migration law, root systems, and soil should be improved, and crop silicon levels should be analyzed to determine the effect on accumulation volume and carbon sequestration. Future studies should investigate the silicon absorption mechanism, root silicification process, and phytolith-occluded carbon content of crops and the agricultural carbon sequestration potential of the ecologically fragile karst area in Southwest China to improve farmland ecosystem crop planting and carbon sink estimation.
Citric acid-mediated mobilization of legacy phosphorus in fertilized grey desert soil
HAN Chaoqun, LIU Jin, YANG Jianjun, LI Jumei, LIU Hua, CHEN Yuanquan, SUI Peng
2020, 28(12): 1941-1948. doi: 10.13930/j.cnki.cjea.200474
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Understanding soil phosphorus (P) characteristics and release potential is important for using the accumulated soil P (legacy-P). A long-term fertilization experiment in grey desert soil was performed to investigate the release potential and characteristics of soil legacy-P after mobilization with a low molecular-weight organic acid (i.e., citric acid). Grey desert soil was untreated (CK), treated with commercial fertilization (NPK) or organic manure plus commercial fertilization combination (NPKM), and extracted with citric acid at high (10 mmol·L-1) or low (2 mmol·L-1) concentrations. The results showed that the legacy-P release potential differed among the variable fertilization treatments and was consistent with soil total P concentrations (NPK > NPKM > CK). The legacy-P release potentials after citric acid extraction were similar at high and low concentrations and made up more than 80% of the soil total P. Rapid soil P release was accompanied by a sharp decrease in soil pH, indicating that acid dissolution is the primary release mobilization mechanism. Under NPK treatment, the mobilized P was greater than that under NPKM from the beginning to the end of mobilization. NPKM released more P at the beginning of mobilization with low citric acid concentration, similar to soil magnesium. These results suggest that magnesium-associated P played a major role in P mobilization under NPKM treatment. The high citric acid concentration primarily mobilized the inorganic Ca8-P pool, followed by the inorganic Ca10-P pool. Citric acid significantly facilitated P mobilization in fertilized grey desert soil. The high release potential indicates that grey desert soil legacy-P can be accessed by reducing fertilization and efficient P management practices.
The effects of biochars on humus composition in acidic purplish soil
ZHAO Hailan, LI Bing, WANG Changquan, LONG Sifan, LI Bin, XIAN Shunzhi, ZENG Linhao, XIAO Meijuan, LIU Qixin
2020, 28(12): 1949-1957. doi: 10.13930/j.cnki.cjea.200277
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Biochar characteristics are similar to feedstock lignin and cellulose contents. Two kinds of biochar were produced from cellulosic (maize straw) and ligneous (Eupatorium adenophorum) feedstocks, respectively, to evaluate how lignocellulosic feedstock biochar influence the humus composition in acidic purplish soil. Acidic purplish soil was treated with 5% maize straw biochar (MB) or 5% E. adenophorum biochar (EB) for 90 days, and the humic acid (HA), fulvic acid (FA), and humin (HM) contents, chemical elements, and HA color tonal coefficient were analyzed. The biochar specific surface areas were 2.32 m2·g-1 (MB) and 0.72 m2·g-1 (EB), and the total pore volumes were 42.71 mm3·g-1(MB) and 12.59 mm3×g-1 (EB). The carbon to hydrogen molar ratios (C/H) were 1.91 (MB) and 1.46 (EB), and the oxygen and sulfur to carbon molar ratios[(O+S)/C] were 0.09 (MB) and 0.16 (EB), indicating that the MB had a stronger adsorption capacity, a higher organic matter, condensation degree, and a lower oxidation degree. Biochar application significantly increased the soil HA, FA, and HM contents (P < 0.05) compared to no application (CK). After 90 days, biochar amendment increased the HA content by 65.59%-102.82%, increased the FA content by 85.87%-118.54%, and increased the HM content by 137.25%-161.23%. The MB increased the humus composition contents more than EB, and both treatments reduced the soil HA/soil organic carbon (SOC) values by 13.53%-27.06% and the FA/SOC values by 6.81%-18.03% (EB treatment P < 0.05). Both treatments also increased the HM/SOC values by 4.58%-11.40% (MB treatment P < 0.05). Biochar amendment increased the HA color tonal coefficient (ΔlgK) degree by 2.40%-5.60%, reduced the C/H of HA by 3.51%-11.81%, and increased the (O+S)/C by 1.51%-8.74%. The biochar application increased the content of each humic component, reduced the C/H condensation degree, and improved the HA oxidation degree; the effect was more prominent when MB was applied. MB application significantly increased the proportion and stability of HM/SOC, but reduced the stability of HA[C/H decreased, (O+S)/C increased]. EB biochar significantly reduced the proportion of HA/SOC and FA/SOC, and had no effect on the proportion of HM/SOC, and increased the proportion of labile organic carbon.
Chinese and international organic fertilizer standard comparison and risk assessment
XIE Wenfeng, WU Tong, SHI Yuejiao, ZHU Yi
2020, 28(12): 1958-1968. doi: 10.13930/j.cnki.cjea.200300
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China has a large population, daily life and manufacturing activities produce large quantities of organic waste. An efficient way to reduce organic waste pollution is by transforming it into organic fertilizer. Agricultural industry-standard NY 525-2012, established in 2012, is the only policy used to regulate organic fertilizers in China, but it is outdated. To improve the Chinese organic fertilizer standard system, we reviewed and analyzed the quality standards in Chinese, Japanese, Australian, European Union, and American organic fertilizers by comparing the organic matter, nutrient, and heavy metal concentrations and pathogen levels. The results showed that the Chinese organic fertilizer quality standard is stricter than that in the United States, but has disadvantages compared to the European Union. In China, there are no organic fertilizer limits for copper, zinc, and nickel, and some of the heavy metal limits (e.g., cadmium) are loose. Therefore, long-term application may lead to soil heavy metal contamination, risking crops. Additive and antibiotic overuse in the livestock and poultry industries, an organic fertilizer production technology shortage, missing scientific and professional guidance for farmers, and insufficient direction from relevant departments and agencies all increase the risks associated with organic fertilizer application in China. Improving the standard system, restricting heavy metals, antibiotics, and other toxic substances, and inspecting raw material batches before processing will support the quality and sustainable development of the organic fertilizer industry in China.
Predicting spatiotemporal changes in land use and habitat quality based on CA-Markov: A case study in central Ningxia, China
WU Dan, LI Huan, AI Ning, HUANG Tao, GU Jisheng
2020, 28(12): 1969-1978. doi: 10.13930/j.cnki.cjea.200221
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The ecological impacts of land use have become a contested topic in ecological environmental research. An understanding of the land-use structure characteristics in arid and semi-arid areas allows for habitat quality assessment and prediction and provides a decision-making guide for regional ecological planning and restoration. Remote sensing apparatus equipped with an operational land imager and enhanced thematic mapper plus sensors, meteorological data, and socio-economic data were used to explore the temporal and spatial changes of land use and habitat quality in the arid area of central Ningxia, China, from 2000 to 2030. Land-use transfer flow, the InVEST model, and the CA-Markov model were used to simulate the habitat characteristics and laws and generate predictions. The land-use transfer flow, which explored the dynamic changes of the land system structure, showed significant results and explained the land-use transfer laws and spatial distribution characteristics. The land system structure changes were consistent with the ecological construction plan and had a concentrated distribution on both sides of the Yellow River basin. The land system's comprehensive dynamics gradually decreased and stabilized. The entropy value showed an annual downward trend, indicating that over time, with less human disturbances, the land can self-adjust and self-repair, creating a stable state. From 2000 to 2015, the ecological environment quality showed "U" shape characteristics, indicating an excellent habitat quality grade. From 2015 to 2030, the land system structure will undergo significant changes; the excellent, good, and poor habitat quality areas will gradually expand, and the ecosystem will stabilize and improve. The multi-model integration application can thus provide support for regional land planning and ecological restoration.
Optimization of composting technology for vertical silo reactor
LIU Zelong, WANG Xuan, CAO Yubo, MA Lin
2020, 28(12): 1979-1989. doi: 10.13930/j.cnki.cjea.200336
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Abstract:
Reactor composting technology is a new and quick composting method. The reactor quickly degrades the material and kills pathogens; however, the reactor product is still unable to reach full maturity and requires further curing. The influence of process parameters, such as composting time, reactor discharge aeration mode, maturing treatment, and costs, on the reactor technology is still unclear. To investigate how the composting time and aeration mode affect the reactor efficiency, a pilot composting experiment was performed in a 12 m3 vertical composting reactor with chicken manure and sawdust using continuous and intermittent aeration modes (i.e., gas supply). The composting process was divided into two stages:reactor composting and curing. Five composting times (2, 4, 6, 8, and 10 days) were used in the reactor composting stage, and a static pile turned once per week was used for curing. Samples were taken every 2 days during the reactor composting stage and every 3 days during the curing stage. The temperature, moisture content, total nitrogen, organic matter, and germination index were measured, and the organic matter degradation rate, product moisture content, nitrogen loss, and operating costs were assessed. The results showed that the organic matter degradation rate in the 10-day compost increased by 60.7% (intermittent aeration) and 66.2% (continuous aeration) compared to the 2-day compost, and the product moisture content reduced by 41.2% (intermittent aeration) and 40.7% (continuous aeration). Most of the material degradation occurred during the reactor composting stage, and more time taken during this stage meant that less maturing time was required. However, the cost increased because of high energy consumption and a reduction in the composting reactor capacity. Increasing the reactor composting time also increased nitrogen loss. The 10-day composted material with a continuous gas supply lost 17.5% more nitrogen than the 2-day composted material. Compared with an intermittent gas supply, a continuous gas supply improved the composting efficiency, shortened the composting cycle by 32.1%, and increased the product total nitrogen content by 7.4% on average. The daily energy consumption during the reactor composting stage was 20.2% higher with the continuous gas supply, compared with the intermittent gas supply, but a shorter composting cycle reduced the average operating costs by 16.5%. Based on these results, the "continuous gas supply mode + 8-d in-reactor composting (R8-C)" is recommended to improve the reactor composting efficiency and costs.

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