Governing Body: Journal of South China Agricultural University
Organizers: Journal of South China Agricultural University
Chief editor：Liu Yahong
ContactAddress: No.483 Wushan Rd, Tianhe, Guangzhou 510642, Guangdong Province, China
Editing and publishing：Editorial Office of Journal of South China Agricultural University
Domestic distribution:Editorial Office of Journal of South China Agricultural University
Issued abroad:China International Book Trading Corporation
2022, DOI: 10.7671/j.issn.1001-411X.202110016
目的 探究日粮添加不同共轭亚油酸(Conjugated linoleic acid，CLA)异构体对小鼠体脂、能量代谢和肠道微生物的影响。方法 用普通日粮(对照组)、普通日粮分别添加质量分数为2%的顺9，反11?共轭亚油酸(c9, t11-CLA)和反10，顺12?共轭亚油酸(t10, c12-CLA)饲喂小鼠12周，检测小鼠脂肪含量、能量代谢和肠道微生物的变化。结果 与对照组相比，c9, t11-CLA和t10, c12-CLA组小鼠体质量分别降低了22.79%和25.04%；脂肪含量分别降低了57.98%和59.41%；小鼠皮下脂肪、附睾白色脂肪以及褐色脂肪含量也显著降低。c9, t11-CLA和t10, c12-CLA均显著提高小鼠耗氧量和产热量，其中，t10, c12-CLA显著降低小鼠夜间的呼吸交换率。16S rRNA测序结果显示，3组小鼠的肠道微生物菌群结构存在明显差异，c9, t11-CLA和t10, c12-CLA组小鼠肠道中与机体代谢相关的菌群丰度显著高于对照组，且t10, c12-CLA能促进与脂质代谢相关的菌群丰度上调。在门水平，c9, t11-CLA和t10, c12-CLA组厚壁菌门和放线菌门相对丰度显著上调，拟杆菌门和疣微菌门相对丰度显著下调；在属水平，与对照组相比，c9, t11-CLA组双歧杆菌属相对丰度显著上调，Ileibacterium和Akkermansia相对丰度显著下调。结论 日粮添加c9, t11-CLA或t10, c12-CLA，可显著降低小鼠脂肪沉积，这可能与CLA促进机体能量代谢和改变肠道微生物菌群结构有关。
2022, DOI: 10.7671/j.issn.1001-411X.202109021
Objective The acquisition of high quality disease-resistant rice maintainers is the premise of improving the quality and resistance of sterile lines. The molecular marker-assisted selection (MAS) can be used for oriented breeding and accelarating the breeding process of elite rice maintainers.Method ‘Hengfeng B’ and ‘Guang 8B’ were used as recurrent parents, and ‘B39’ carrying fragrance gene Badh2 and rice blast resistance gene Pita was used as donor parent. The successive backcross breeding and MAS technology was combined to improve the quality and resistance traits of these two maintainer lines. Result Through multi-generation backcross breeding, 14 samples of BC3F2 improved materials were obtained. The improved single-plant line was tested with the corresponding sterile line, and the sterility grades of the corresponding plot were fully sterile and high sterile. Through quality and resistance identification, most of improved target strains were rated as strong aroma. The resistance to rice blast significantly improved and the disease nursery identification showed that they were resistant or highly resistant to rice blast. Rice quality was characterized by slender rice grains with low amylose content and low chalkiness. Other agronomic and economic characteristics were similar to the recurrent parent. The genetic background recovery rates of most strains were 80% to 90% which met the estimated recovery effect. Conclusion MAS shortens the process of trait improving for maintainer lines, helps acquiring improved maintainers with better quality, stronger blast resistance and fragrance, and realizes the oriented genetic improvement of ‘Hengfeng B’ and ‘Guang 8B’, which lays a foundation for further integrated improvement in rice quality and resistance of three-line hybrid rice.
2022, DOI: 10.7671/j.issn.1001-411X.202109041
Objective Heading date is an important agronomic trait in rice, which determines suitable cultivated areas and seasons of rice varieties. Ghd7 and DTH8 are two key heading date genes in rice, comprehensively discovering their genetic interaction, expression regulation, and effects on agronomic traits are important for variety breeding, improvement of adaptability and yield of rice. Method In this study, we bred a Ghd7/DTH8 digenic segregating population in the non-functional hd1 and prr37 background from the progeny of the hybrid rice ‘Ningyou 1179’ by molecular marker-assisted selection. Heading date, expression of the downstream genes (Ehd1, Hd3a, RFT1), and some agronomic traits were investigated. Result Under natural long day and natural short day conditions, either Ghd7 or DTH8 independently repressed the expression of Ehd1, Hd3a and RFT1 genes, and delayed heading. Both Ghd7 and DTH8 could significantly promoted plant height, number of primary branches, number of secondary branches, spikelets of main panicle and
2022, DOI: 10.7671/j.issn.1001-411X.202107025
Objective To explore the effects of drought stress on maize tassel development characteristics and yield, and provide a theoretical basis for drought resistance and yield protection of maize planting in northeast China.Method In the pot experiment, original soil treatment and adding soil conditioner treatment were set up. Different drought stress degrees of normal water supply (CK), light drought stress, moderate drought stress, and severe drought stress were conducted from the big trumpet stage to silking stage of maize, to study the effects of different drought stress degrees on maize anthesis-silking interval, tassel morphological and physiological characteristics and yield. Result Drought stress delayed the silking time of the female inflorscence of maize causing the tasseling and, silking of the maize to be asynchronous, most seriously under severe drought stress. Compared with CK, the anthesis-silking interval in the original soil and adding soil conditioner treatments was extended by 6.33 and 4.67 d, respectively. Different drought stress degrees decreased the maize size and spindle length. Light drought stress was conducive to the accumulation of dry matter in the maize tassels, and compared with CK, the tassel dry matter in the original soil treatment and the adding soil conditioner treatment increased by 5.18% and 14.87%, respectively. Drought stress prompted the tassels to secrete antioxidant system enzymes and osmotic adjustment substances to resist adversity damage. However, under severe drought stress, too much malondialdehyde (MDA) and harmful substances were produced in the tassel, which caused the activity of the antioxidant system enzyme to decrease. Drought stress caused a serious decline in maize yield. Under severe drought stress, the maize yield in the original soil treatment decreased by 62.39% compared with CK, and the yield in the adding soil conditioner treatment decreased by 57.77%.Conclusion Drought stress seriously affects the development and yield of maize tassels, especially under severe drought stress, which causes irreversible damage to the tassels. The application of soil conditioner can improve the stress resistance of maize tassels to a certain extent, thereby ensuring the normal growth and development of maize tassels and yield.
2022, DOI: 10.7671/j.issn.1001-411X.202107044
Objective The aim was to obtain a water and fertilizer management mode that regulates potato-planting soil organic carbon storage, and reveal the influence of soil enzyme activity on soil organic carbon fraction and carbon pool management index (CPMI). Method Field experiment was carried out in Nanning under the rain-shelter condition with two drip irrigation levels (high irrigation amount: Soil water content was maintained at 60%–70%, 70%–80%, 75%–85% and 50%–60% of field capacity at the seedling, tuber formation, tuber expansion and starch accumulation stages, respectively; Low irrigation amount: Soil water content was maintained at 50%–60%, 60%–70%, 70%–80% and 40%–50% of field capacity at the seedling, tuber formation, tuber expansion and starch accumulation stages, respectively) and three drip fertigation ratios (NK100-0: All N,K fertilizer were applied to soil as base fertilizer; NK70-30: 70% N,K fertilizer were applied to soil as base fertilizer and 30% as topdressing with drip fertigation; NK50-50: 50% N,K fertilizer were applied to soil as base fertilizer and 50% as topdressing with drip fertigation). The contents of total organic carbon (TOC), dissolved organic carbon (DOC), microbial biomass carbon (MBC) and labile organic carbon (LOC) and the activities of sucrase, cellulase and catalase in the soils were measured after harvesting the potato. Then CPMI was calculated and the relationships of soil organic carbon fraction and CPMI with soil enzyme activities were analyzed. Result Drip irrigation amount affected organic carbon contents and components in the soils significantly. Under the same fertigation ratio, high irrigation amount had higher organic carbon contents and components, CPMI and sucrase activity in the soils than those of low irrigation amount. Under the high irrigation amount condition, NK50-50 increased TOC content by 15.2% and 7.1% respectively compared with NK100-0 and NK70-30, and NK50-50 increased LOC content by 25.0% compared with NK100-0. Moreover, NK50-50 of high irrigation amount treatment had significant higher contents of TOC and LOC than those of other treatments. Under the same drip irrigation amount, the effect of drip fertigation ratio on the activities of three enzymes was not significant. Among all treatments, NK50-50 of high irrigation amount treatment had the highest sucrase activity. Compared with NK100-0, NK50-50 increased soil CPI and CPMI by 15.1% and 25.8% respectively under the high irrigation amount condition, and NK50-50 increased carbon pool index (CPI) and CPMI by 12.6% and 8.4% respectively under the low irrigation amount condition. Among all treatments, NK50-50 of high irrigation amount treatment had higher CPI and CPMI. In addition, soil TOC, DOC and MBC were extremely significantly or significantly correlated with the sucrase activity (with correlation coefficients of 0.61, 0.48 and 0.46, respectively). Conclusion NK50-50 of high irrigation amount treatment increases the contents of organic carbon and its components and sucrase activity in soil, and can be used as the water and fertilizer management mode regulating potato-planting soil organic carbon storage. Soil sucrase activity affects the contents of TOC, DOC and MBC.
2022, DOI: 10.7671/j.issn.1001-411X.202108022
Objective To discover the effects of biochar on soil bacterial community diversity, abundance and structure of different rice varieties, and provide a scientific basis for the application of biochar in paddy field. Method Experiment of split-split plot was designed in the late rice field of Fluvo-aquic soil type in Taishan Town of Jiangmen County, Guangdong Province in 2019, treatments were designed with no biochar application(CK), biochar application of 3.5 t/hm2 (Tr1) and 7 t/hm2 (Tr2) as the main plots, six different conventional high-quality rice varieties, including ‘Huanghuazhan’, ‘Wuchangxiangdao’, ‘Xiangyaxiangzhan’, ‘Xiangwanxian’, ‘Nongxiang 32’ and ‘Yuzhenxiang ’, were designed as the subplots in each main plots. 16S rRNA gene V3-V4 high-throughput sequencing technology analysis was conducted. Result Biochar Tr1 and Tr2 treatments significantly improved the bacterial community diversity of rice variety ‘Yuzhenxiang’, and biaochar Tr2 treatment significantly improved the bacterial community richness of rice variety ‘Yuzhenxiang’, and also biaochar Tr1 treatment significantly increased the bacterial community abundance of rice variety ‘Huanghuazhan’. A total of 73 phyla, 92 classes, 174 orders, 298 families, 682 genera and 456 species of bacteria were obtained, mainly including 10 main phyla of Proteobacteria, Firmicutes, Bacteroidetes, Nitrospirae, Acidobacteria, etc. Among them, the Proteobacteria are the first dominant bacteria (the proportion of relative abundance reaching 30.0%~61.1%), with γ-, δ-, and α-Proteobacteria as the dominant subgroups. Compared with CK, Proteobacteria and Bacteroidetes of some rice varieties showed a significant increase in Tr2 treatment, and Euryarchaeota increased significantly in Tr1 treatment. Biochar treatment caused changes in the structural composition of the corresponding soil bacterial community at the genus level. Soil bacterial groups with relatively low or extremely low abundance, such as Acidovorax, Sphingomonas and Pedobacter, were more sensitive and susceptible to the impact of biochar. The Tr1 treatment had an effect on the composition and distribution of soil bacteria compared with CK. Conclusion Biochar treatment can affect the soil bacterial community in rice field to some extent, the soil bacterial communities of rice varieties of ‘Yuzhenxiang’ and ‘Huanghuazhan’ are mostly affected by biochar. Biochar treatment increases the soil bacterial community diversity and richness of rice varieties of ‘Yuzhenxiang’ and ‘Huanghuazhan’, and the difference between biochar treatment is mainly reflected in the relative abundance of soil bacterial communities.
2022, DOI: 10.7671/j.issn.1001-411X.202107043
Objective This study was aimed to investigate the tolerance of Ilex rotunda, absorptions and accumulations of lead (Pb) and cadmium (Cd) in Pb or Cd polluted soil, and provide a theoretical basis for phytoremediation of Pb or Cd contaminated soil. Method A pot experiment was conducted to evaluate the effects of single Pb pollution (500, 1 000 and 1 500 mg·kg?1) and single Cd pollution (10, 25 and 50 mg·kg?1) on growth, root morphology, nutrients and Pb or Cd absorption and accumulation of I. rotunda seedlings. Result Compared with the control (non-polluted soil), 500 mg·kg?1 Pb treatment significantly increased the root biomass and root surface area of I. rotunda, and both 500 and 1 000 mg·kg?1 Pb treatments significantly increased shoot diameter and quality index. 1 500 mg·kg?1 Pb treatment significantly reduced the biomass, quality index, and total nitrogen (N) accumulation of I. rotunda and inhibited root growth, but significantly increased phosphorus (P) contents in root and shoot as well as potassium (K) content in shoot. All Pb addition treatments showed significantly higher total Pb contents and accumulations than those of the control treatment, and 1 500 mg·kg?1 Pb treatment had the highest Pb contents and accumulations in root, shoot and total plant. Compared with the control, Cd treatments had no significant effect on growth, root morphology and nutrient accumulation of I. rotunda, but significantly increased K content in shoot. All Cd treatments significantly increased Cd contents and accumulations in root, shoot and total plant. Root Cd content increased significantly with the increase of Cd concentration, while 50 mg·kg?1 Cd treatment had the highest root Cd content of 6.40 mg·kg?1. The content and accumulation of Pb in root were significantly higher than those in shoot. Cd content in root was also significantly higher than that in shoot. Cd accumulation in root was significantly higher than that in shoot under 50 mg·kg?1 Cd treatment. Conclusion I. rotunda is well adapted to single Pb or Cd pollution in soil, and has a strong ability to absorb and accumulate Pb or Cd. I. rotunda can be used as a candidate tree for remediation of Pb or Cd polluted soil.
2022, DOI: 10.7671/j.issn.1001-411X.202104024
Objective To discuss the effects of different phosphorus concentrations on soil characteristics, growth status and chromone content of Saposhnikovia divaricata, and provide theoretical basis for technical strategy formulation of S. divaricata artificial cultivation and responding mechanism research of S. divaricata to low phosphorus stress. Method Two-year-old S. divaricata was used as material, and three phosphorus treatments with NH4H2PO4 concentration of 1.0, 0.1 and 0 (no phosphorus) mmol/L respectively were set up. The soil physical and chemical properties, and the growth characteristics and total contents of four kinds of chromones in S. divaricata were determined on the 30th, 60th, and 90th day to analyze the correlativity between the various indicators and total chromone content under different phosphorus concentrations. Result The root diameter and weight of 2-year-old S. divaricata in no phosphorus treatment were lower than those of 1.0 mmol·L?1 phosphorus treatment during the whole treatment period, and the root length after 90 d of treatment was significantly higher than those of 1.0 and 0.1 mmol·L?1 phosphorus treatments. After 60 d of treatment, the soil pH of 1.0 mmol·L?1 phosphorus treatment was significantly higher than those of 0.1 mmol·L?1 and no phosphorus treatments. The contents of soil organic matter in 1.0 and 0.1 mmol·L?1 phosphorus treatments were significantly lower than that in no phosphorus treatment during the whole treatment period. After 90 d of treatment, the alkali-hydrolyzable nitrogen content in soil of no phosphorus treatment was significantly higher than those of 1.0 and 0.1 mmol·L?1 phosphorus treatments, whereas the available phosphorus content in soil of 0.1 mmol·L?1 phosphorus treatment was significantly higher than that of no phosphorus treatment, the total content of four chromones of 0.1 mmol·L?1 and no phosphorus treatments were significantly higher than that of 1.0 mmol·L?1 phosphorus treatment. On the 30 th day of treatment, the activities of acid phosphatase in soil among three treatments were significantly different. There were positive correlations between root diameter/root fresh biomass and chromone content in 1.0 mmol·L?1 phosphorus treatment, between alkali-hydrolyzable nitrogen content/available phosphorus content/root fresh biomass and chromone content in 0.1 mmol·L−1 phosphorus treatment, between pH/alkali-hydrolyzable nitrogen content /acid phosphate activity and chromone content in no phosphorus treatment, respectively. Conclusion S. divaricata has a series of response mechanisms to phosphorus stress, including chromone content significantly increasing, synergistic interaction of pH, organic matter, alkali-hydrolyzable nitrogen and acid phosphatase, which ensures the absorption and utilization of nutrients by S. divaricata.
2022, DOI: 10.7671/j.issn.1001-411X.202108016
: Objective To explore the effects of arbuscular mycorrhizal (AM) fungal inoculation on the growth of Nitraria sibirica Pall. under different levels of salt and heavy metal stress, and provide a scientific basis and data support for plant-microbial joint remediation of heavy metal contaminated and salinized soil. Method Greenhouse potted soil was used to simulate different levels of heavy metal Cd polluted (0, 2, 5 mg·kg?1 Cd in dry soil) and NaCl (0, 1.5 g·kg?1 Na+ in dry soil) salinized soil (Cd0Na0, Cd0Na1.5, Cd2Na0, Cd2Na1.5, Cd5Na0, Cd5Na1.5). The effects of AM fungi (Funneliformis mosseae) on mycorrhizal infection, element absorption, ion balance, biomass, Na+ and Cd contents of N. sibirica under Cd and NaCl stress were studied. Result Under heavy metal Cd and NaCl stress, the mycorrhizal infection rate of F. mosseae roots was 12.68%?21.90%. Compared with CK with no inoculation, AM inoculation increased the total dry weight of N. sibirica in different treatments by 101.35%?215.29%. The aboveground mineral nutrient elements significantly increased by 47.55%?216.50%. Na+ contents in shoots and roots decreased significantly, while Na+ accumulation in root increased significantly. Cd contents in shoots treated with Cd2Na0, Cd2Na1.5, Cd5Na0 and Cd5Na1.5 and roots treated with Cd2Na1.5, Cd5Na0 and Cd5Na1.5 significantly decreased. At the same time, K+/Na+, Ca2+/Na+ and P5+/Na+ ionic equilibrium in shoots and roots were adjusted after AM inoculation. Conclusion AM fungi can alleviate the adverse effects of NaCl and heavy metal stress on the growth of N. sibirica by promoting the absorptions of nutrient elements, regulating the ion balance in the plant and affecting the absorptions of Na+ and Cd.
2022, DOI: 10.7671/j.issn.1001-411X.202105042
Objective To evaluate the ecological environment quality of coal mining area in Huaibei, and provide a scientific and theoretical basis for monitoring the ecological environment change in the mining area. Method The growth and development condition of Caenorhabditis elegans in the water environment of the mining area and the change of soil nematode community structure were studied to evaluate the ecological environment quality.Result The water environment in the coal mining area reduced the life span, the survival rate, the body length and the number of eggs laid by C. elegans, meanwhile induced the apoptosis of C. elegans germ cells. The longer the coal mining time was and the closer the sampling site was to the mine, the more significant the inhibitory effect on the nematode development indicators was. Soil environment in coal mining area decreased the number of nematode genera, increased the relative abundance of phytophagous. At the same time, the Shannon diversity index, Wasilewska index and free-living nematode maturity index significantly decreased, and the phytophagous maturation index significantly increased, indicating that the mining environment reduced the soil health status. The longer the coal mining time was and the closer the sampling site was to the mine, the greater the influence on the soil nematode community structure was. Conclusion The responses of C. elegans growth and development index to water environment and soil nematode community structure to soil environment have well indicated the quality of water environment and soil environment in Huaibei coal mining area, therefore nematode can be used to evaluate the quality of water environment and soil environment of coal mining area.
2022, DOI: 10.7671/j.issn.1001-411X.202105028
目的 探讨入侵植物空心莲子草Alternanthera philoxeroides与其共存本土同属种莲子草A.sessilis的元素化学计量比差异及环境驱动力，明晰其资源分配格局与营养策略。方法 在广西、广东、江西和河南等省（区）的野外生境中设置6个莲子草?空心莲子草共存群落样地和7个莲子草单生群落样地，分别测定这2种植物的w(C)、w(N)、w(P)及其化学计量比（C∶N、C∶P和N∶P），并记录样地环境指标，利用回归分析和典范对应分析探究空心莲子草、莲子草的营养策略差异及对异质生境的响应。结果 在莲子草?空心莲子草共存群落中，这2种植物的w(C)、w(N)、w(P)及其化学计量比均无显著性差异。w(C)均随气温上升呈“先上升后下降”趋势；空心莲子草w(N)随降雨量上升而下降，莲子草w(N)随降雨量上升呈“先下降后上升”趋势；莲子草w(P)随海拔上升而增加。C∶N均随海拔上升呈“先下降后上升”趋势，莲子草C∶P随海拔上升而下降、N∶P随土壤N上升而下降，空心莲子草C∶P和N∶P与环境因子之间均无显著性关系。在莲子草单生群落中，其w(C)随土壤w(NH4+-N)上升而降低、随降雨量上升而增加；其w(P)随海拔和土壤w(N)上升而降低；其C∶N随土壤w(NH4+-N)、w(NO3?-N)上升而降低；其C∶P随土壤w(N)上升而增加。结论 莲子草的C、N、P生态化学计量特征对异质环境的响应程度高于空心莲子草，莲子草在高海拔区域选择以“生长竞争策略”应对空心莲子草入侵。研究可为预测外来种的入侵力及深入理解物种共存机制提供理论依据。
2022, DOI: 10.7671/j.issn.1001-411X.202107041
Objective In view of the current situation that the quality of transplanting is mainly based on manual observation and random sampling in China, it is proposed to use the convolutional neural network GoogLeNet to recognize the morphology of rice seedlings.Method Firstly, clear and intact images of rice seedlings were obtained by UAV aerial photography at low altitude. Data sets of floating seedlings, damaged seedlings and qualified seedlings were made by cutting and marking. Then, based on the GoogLeNet structure training data, the optimal network recognition model was obtained. Finally, the image classification experiment of seedlings per hole was carried out, and compared with traditional image classification algorithms (SVM，BP neural network).Result Under the condition of using the same samples, the seedling morphology recognition method based on GoogLeNet completed the judgment and classification was faster and more accurately. The average accuracy of seedling morphology recognition was 91.17%, and the average detection time was 0.27 s. Compared with SVM and BP neural network, the average classification accuracy increased by 21 and 13 percentage points respectively, and the detection time was shortened by 1.09 and 0.58 s respectively. Conclusion This study can provide the relevant support for evaluation of rice transplanting quality.
2022, DOI: 10.7671/j.issn.1001-411X.202109005
Objective In order to realize the precise application of herbicides for lawn weed management, an improved fuzzy C-means (FCM) clustering segmentation algorithm was proposed to solve the problem that it is difficult to segment weeds due to the similar color between weeds and lawns in natural environment.Method The region of interest was extracted by extra-green operator, and the multi-channel information in HSV space was incorporated for image preprocessing to expand the feature difference between weeds and lawns. The filtering range was constrained using region area to remove the lawn background noise in the preprocessed image and reduce the gray level loss in the target region caused by median filtering. An anisotropic detection operator of difference of gray distribution(DGD) was proposed. In the clustering process, the gray distribution difference characteristics in different directions around pixels were introduced to realize lawn weed segmentation.Result Compared with the traditional FCM, FCM-S2, FCMNLS and RSFCM algorithms, the algorithm in this paper (DGDFCM) had better suppression effect on most noise areas and could achieve ideal weed segmentation effect. The DGDFCM algorithm could effectively segment lawn weeds, and the average segmentation accuracy was 91.45%, which was 16.35%, 4.12%, 6.80% and 8.06% higher than FCM, FCM-S2, FCMNLS and RSFCM algorithms, respectively.Conclusion The DGDFCM algorithm can effectively segment lawn weeds in natural environment, provides the condition of precise application of herbicides for lawn weeds, and has a practical application value.
2022, DOI: 10.7671/j.issn.1001-411X.202107049
Objective To achieve low-cost agricultural machinery field positioning for small and medium-size farmland in southern China, so as to reduce labor intensity for machine operator, and improve the working efficiency of agricultural machinery. Method This system utilized ultra wide band (UWB) technology to accomplish real-time positioning of operating machinery, and the precise three-dimensional coordinates of the positioning labels were calculated using the localization algorithm. The position correction algorithm was then used to correct the field positioning error resulted from the body tilt of working machinery. A path planning algorithm based on AB line was designed to plan the operation path and calculate the operation deviation in a real-time manner. This system provided real-time driving assistance information for agricultural machinery operators through the visual human-computer interaction interface. Result In the paddy field environment, the average lateral deviations were less than 7 cm when agricultural machinery traveled along the planned path at speeds of 0.5, 1.0 and 1.5 m/s, respectively. When the travel speed was above 1.0 m/s, the average lateral deviation, the average standard deviation and the maximum lateral deviation were reduced by 52.79%, 49.82% and 50.04% respectively, based on the position correction algorithm. When the agricultural machinery equipped with the auxiliary navigation system was tested in the field transplanting experiment, the average lateral deviation between each operating trajectory and its fitting line was 5.90 cm and the average standard deviation was 3.64 cm. The average lateral deviation between each operating trajectory and its planned path was 6.98 cm and the average standard deviation was 4.95 cm. Conclusion The auxiliary navigation system has high positioning accuracy and good stability, as well as low-cost and strong universality, which can address the requirements of agricultural machinery field operation for small and medium-size farmland in southern China. The research results can provide a valuable reference for precise positioning of agricultural machinery in the field.
2022, DOI: 10.7671/j.issn.1001-411X.202108015
Objective The construction method of discrete element model and the setting of simulation parameters of sugarcane segment as stalk material with large length and diameter ratio are not clear, the accuracy of the model has a great influence on the dynamic response characteristics between particles, and the accuracies of the simulation parameters need to be improved by parameter calibration. Method Taking the physical repose angle of sugarcane segment as the response value, the discrete element parameters were optimized and calibrated by simulation test method. Firstly, the basic physical parameters of sugarcane segment were measured by physical test, and the sugarcane segment simulation model was constructed based on the multi-sphere polymerization model and XML method. Then, the Plackett-Burman test was used to screen the significance of eight initial parameters in the discrete element simulation of sugarcane segment, and the optimal value ranges of significant parameters were determined by the steepest ascent search test. Further, the second-order regression equation between the significant parameters and repose angle was established based on the Box-Behnken test, and taking the physical repose angle of 42.70° as the target value, the regression equation was optimized. Result The significance screening test showed that the Poisson’s ratio of sugarcane segment, the static and dynamic friction coefficients between two sugarcane segments had significant influence on the simulated repose angle. The optimal parameter combination was as follows: The Poisson’s ratio of sugarcane segment was 0.35, the static and dynamic friction coefficients between sugarcane segments were 0.53 and 0.04 respectively. The simulation test results of the optimal parameter combination showed that there was no significant difference between the simulated repose angle and the physical repose angle, and the relative error between them was 0.99%, which further verifies the reliability of sugarcane segment parameters calibrated by discrete element method. Conclusion The sugarcane segment discrete element model and the optimal simulation parameters can be used in the sugarcane segment discrete element simulation test, and can provide a reference for calibration of the discrete element parameter of stalk agricultural materials with large length and diameter ratio.