中国生态农业学报(中英文)

Effects of different cultivation facilities on the diversity of soil meso-and micro-fauna

CHEN Xi, LI Qiangqiang, TANG Wei, WANG Zhenyi, TAO Jun, XU Yingjun, GU Wei

2019, 27(8): 1147-1156. doi: 10.13930/j.cnki.cjea.180618

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Abstract:
Organic agriculture, which has become increasingly popular in recent years and is widely used in greenhouse facilities, is generally believed to be more conducive to agro-ecosystems than conventional agriculture. The soil fauna is a significant biological indicator of the soil environment. An understanding of the differences in the community structure and diversity of the soil fauna under different facility management regimens is necessary. However, little is known about the effects of both organic and conventional agricultural systems on the diversity of soil meso-and micro-fauna. To investigate the effects of organic facility cultivation on the diversity and community structure of soil meso-and micro-fauna, the fauna of soils under 6 treatments (organic and conventional cropping patterns of leafy and solanaceous vegetables in greenhouse, organic and conventional cropping patterns in open air) in the Shunyi District of Beijing in June 2016 was studied. Fauna from the 0-15 cm soil layer was extracted by the modified Tullgren method. In total, there were 3 869 soil meso-and micro-fauna in the 18 sample plots, belonging to 30 families, 14 orders 14, 2 taxa (suborders). The results were as follows:1) the orders such as Actinedida, Oribatida, and Onychiuridae were in the largest quantities and were the most widely distributed in the study area, where Acarina, Rhabditidae, and Collembola constituted the main taxa of the soil meso-and micro-fauna. 2) In the open air, the numbers of soil meso-and micro-fauna in the 5-10 cm and 10-15 cm layers under organic cultivation were higher than those under conventional cultivation. In the greenhouse, the numbers of soil meso-and micro-fauna in the 0-5 cm and 5-10 cm layers under organic cultivation were significantly lower than those under conventional cultivation. 3) Under organic cultivation, the numbers of soil meso-and micro-fauna in the 0-5 cm and 10-15 cm layers in the greenhouse were significantly lower than those in the open air, and the Menhinick's abundance index of soil meso-and micro-fauna in the 10-15 cm layer in the greenhouse was higher than that in conventional cultivation. Under conventional cultivation, the number of soil meso-and micro-fauna in the 5-10 cm layer in the greenhouse was significantly higher than that in the open air. The Shannon-Weiner diversity index of soil meso-and micro-fauna in the 0-5 cm layer was higher in the greenhouse than in the open air under both organic and conventional cultivation. 4) Under organic cultivation, the number of soil meso-and micro-fauna in the 10-15 cm layer was lower than that under conventional cultivation, and the Pielou's evenness indices of soil meso-and micro-fauna in the 0-5 cm layer were higher than those under conventional cultivation when leafy vegetables were cultivated. Under the conventional cultivation of leafy vegetables, there were more meso-and micro-fauna in the 0-5 cm and 5-10 cm soil layers than in those of solanaceous vegetable cultivation. Therefore, organic cultivation and management in the greenhouse, and the effective use of crop rotation system can facilitate the restoration of soil fauna communities.

The structure of spider communities in crab paddies and conventional paddies

MA Xiaohui, CHE Xiqing, WANG Jingshi, SANG Haixu

2019, 27(8): 1157-1162. doi: 10.13930/j.cnki.cjea.181068

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Abstract:
Rice-crab co-culture (RC) is a new eco-agricultural process in paddy cultivation and breeding models. It has been significantly promoted in the development of eco-agricultural programs. Recent studies, which concern the RC system, mainly focus on the effects of multiple factors on crab or rice production. However, studies on the community of natural enemies in RC ecosystems are still rare. The goal of this study was to determine the regulation of occurrence, composition, and diversity of spider communities in crab paddies and conventional paddies. Suction samplers were applied to collect spiders in the paddies. Species composition and diversity of spiders were recorded and analyzed. The results showed that:1) 31 species and 11 families of spiders were found in both paddies. Three major families of spiders, Lycosidae, Linyphiidae, and Araneidae, accounted for at least 70% of the spider populations. 2) The number of individual spiders in the crab paddies was significantly higher than that in conventional paddies. 3) The Shannon-Wiener index indicated that the diversity of spider species was highest from August through September, and lowest in early June. Furthermore, the results showed that the Shannon-Wiener indexes were positively correlated with Pielou's or Margalef's indexes but were negatively correlated with the Simpon's indexes. The results revealed that there was no difference in the numbers or diversities of spider species between crab paddies and conventional paddies, whereas the difference in the number of individual spiders was significant between the two paddy types. This study lays a foundation for the study of the biodiversity characteristics of arthropods in RC systems.

Effects of different winter planting patterns on carbon management index of paddy field

ZHANG Peng, ZHONG Chuan, ZHOU Quan, TANG Haiying, LI Xinmei, LI Ping, HUANG Guoqin

2019, 27(8): 1163-1171. doi: 10.13930/j.cnki.cjea.180995

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Abstract:
The middle and lower reaches of the Yangtze River region is an important base for rice production in China, which plays an important role in ensuring China's food security. However, the utilization rate of paddy field resources in winter was not high in this area. In this study, the effects of different winter planting patterns on soil quality were discussed, which would contribute to the rational development and utilization of winter fallow fields and provide theoretical basis for improving the sustainability of paddy fields. Five winter cropping modes were set up, including winter fallow, winter Chinese vetch, winter rape, winter garlic and winter rotation (potato, Chinese milk vetch, rape). Soil carbon pool management index and comprehensive evaluation of different winter cropping modes were further analyzed by measuring nutrients, organic carbon, active organic carbon, and microbial biomass carbon in different soil layers. The results showed that the contents of soil organic carbon, microbial biomass carbon, soluble organic carbon and active organic carbon in different winter planting patterns were increased to a certain extent in the depth of 0-30 cm paddy field, compared with those in winter fallow treatment. Among them, soil organic carbon increased by 6.12%-7.17%, active organic carbon increased by 13.56%-20.76%, microbial biomass carbon increased by 0.13%-14.34%, soluble organic carbon increased by 3.49%-19.15%, and soil active organic carbon efficiency increased by 6.74%-17.20%. Winter rotation (potato, Chinese milk vetch, rape) could significantly promote the accumulation of total organic carbon and soluble organic carbon in paddy soil. Different winter patterns increased soil carbon pool activity index and carbon pool index, and soil carbon pool management index increased by 14.37%-27.29%. Soil organic carbon was significantly correlated with active organic carbon (P < 0.01); soil carbon pool management index was significantly correlated with total organic carbon (P < 0.05), and there was a significant correlation between soil organic carbon and active organic carbon (P < 0.01). It can be seen that different winter planting patterns can increase soil organic carbon content and improve soil carbon pool management index. The winter rotation (potato, Chinese milk vetch, rape) pattern has the best comprehensive effect, followed by winter garlic planting pattern.

Prediction of threshold temperature start date for rice at critical development stages in Southwest China

CHEN Chao, XU Fuxian, PANG Yanmei, LI Xiaolan, GUO Xiaoyi

2019, 27(8): 1172-1182. doi: 10.13930/j.cnki.cjea.180686

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Abstract:
Ensuring safe production is a fundamental requirement of the cropping system, being an important basis for stable and high yield of crops. Based on the daily average and maximum temperatures from 1961-2015 in 317 meteorological stations in the rice growing areas of southwestern China, the study analyzed safe sowing dates of rice under different guarantee rates (80%-95%) using the mean variance method. The earliest date of heat stress and chilling injury at rice flowering stage under different guarantee rates were analyzed too. A prediction model of the threshold temperature start date for rice at critical development stages in southwestern China was constructed using the stepwise regression method. At the 80%-95% guarantee rate, the earliest safe sowing date for rice was discovered in southern Yunnan, which was around February 20. The safe sowing dates in northern Yunnan, southwestern Sichuan, central Sichuan basin, most parts of Chongqing and parts of Guizhou were from March 10 to April 10. The safe sowing dates in the rest of southwestern China were from April 10 to May 20. At the 80%-95% guarantee rate, heat stress at flowering stage of middle-season rice occurred mainly in the Sichuan basin, Chongqing, northern and southeastern Guizhou, and the earliest occurrence dates were from July 15 to August 20. The earliest occurrence dates of chilling damage at ratooning or late rice flowering stage in most of Yunnan and Guizhou, and southwestern Sichuan were from June 20 to July 15. Meanwhile, the earliest occurrence dates of chilling damage in western Sichuan basin and northeastern Guizhou were from August 1 to August 20, and from August 20 to September 20 in the remaining areas. Based on the latitude, longitude and altitude, a model for predicting the threshold temperature initiation period for rice at critical development stages in southwestern China was established, which was simple and practical. In addition, using Hejiang of Sichuan and Meitan of Guizhou as the case study, the differences between the actual values and the simulated values of threshold temperature start date for rice were analyzed. The relative error between the actual values and the simulated values of threshold temperature start date for rice was less than 5.0%, which indicated that the model had a good simulation effect. In summary, the prediction of threshold temperature start date for rice at critical development stages can provide a theoretical basis for safe production, disaster prevention and mitigation options in rice production in southwestern China. On the one hand, according to the safe sowing period, the actual sowing period of rice can be adjusted in time, which is necessary to avoid hazards of meteorological disasters. On the other hand, the local major rice varieties can be selected through probabilistic decision-making, to ensure stable and high yield in rice production.

Effects of maize/soybean and maize/peanut intercropping systems on crops nitrogen uptake and nodulation nitrogen fixation

ZHANG Xiaona, CHEN Ping, DU Qing, ZHOU Ying, REN Jianrui, JIN Fu, YANG Wenyu, YONG Taiwen

2019, 27(8): 1183-1194. doi: 10.13930/j.cnki.cjea.181055

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Abstract:
Cereal/legume-based intercropping systems have a significant effect on the soil by increasing nitrogen (N) content. To understand the trends of N uptake, N nutrient competition capacity, and the legume nodulation characteristics in a maize/legume intercropping system, we investigated the N absorption advantage in maize/soybean and maize/peanut strip intercropping systems. We conducted a field experiment to study N accumulation, N nutrient competition, and the legume nodulation N fixation regulation characteristics in different planting patterns, which were maize monoculture (MM), soybean monoculture (SS), maize/soybean intercropping (MS), peanut monoculture (PP), and maize/peanut intercropping (MP). The results showed that compared with the monocultures, intercropping decreased N accumulation in maize and soybeans and had no significant effect on the N accumulation in peanuts. The trend of total N accumulation in the five planting patterns was MS > SS > MP; PP and MM treatments exhibited the lowest accumulation and the difference was not significant. Moreover, the N accumulation of MS treatment was 21.8% higher than that of MP treatment. Additionally, N accumulation of maize in MS and MP treatments decreased by 20.5% and 11.7%, respectively, compared with MM treatment. N accumulation of grain, leaves, and stalks of maize in MP treatment was 8.9%, 21.2%, and 14.3% higher than those in MS treatment. Furthermore, N accumulation of soybean in MS treatment decreased by 28.5%, and the central and fringe rows decreased by 10.1% and 15.4%, respectively compared with SS treatment. The effect of MP treatment on peanut N accumulation was not significant. The value of N nutrition competition indicated that maize had a dominant position in MS, whereas it exhibited less competition in MP treatment. Compared with SS treatment, the number of soybean nodules in MS treatment was higher at the fifth trifoliate stage and lower after the full bloom stage. The effect of nodule fresh weight was not significant at the fifth trifoliate stage, and it decreased after the full bloom stage. Nitrogenase activity of soybean nodules in MS treatment decreased, and the decrease was greater in the central rows. Relative to PP treatment, the number and fresh weight of peanut nodules in MP treatment were higher at the early flowering stage and lower after the acicula forming stage. The nitrogenase activity of peanut nodules in MP treatment decreased, and the amplitude of the decrease was greater in the fringe row. Although the amount of N accumulation of crops in the intercropping planting patterns was reduced, the total N accumulation of the intercropping system was significantly higher than the monoculture planting patterns. The amount of N accumulation of MS treatment was the highest in the two intercropping planting patterns.

Evapotranspiration characteristics of mulched drip-irrigated sunflower farmland in arid region

ZHANG Zhenyu, LIU Lijuan, LI Xiaoyu

2019, 27(8): 1195-1204. doi: 10.13930/j.cnki.cjea.190151

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Abstract:
Mulched drip-irrigation is a burgeoning water-saving irrigation mode in the arid region of Northwest China. It is of great significance to understand and optimize mulched drip irrigation in arid region by analyzing the characteristics of evapotranspiration in mulched drip-irrigated farmland and comparing it with ordinarily irrigated farmland. Using the oasis sunflower farmland in the Sangong River basin on the northern slope of the Tianshan Mountain in Xinjiang as the study area, the farmland evapotranspiration characteristics during the sunflower growth period in 2016 were analyzed using the Bowen ratio-energy balance method, geographical detector, and path analysis method. Furthermore, these characteristics were compared to those of ordinarily irrigated farmlands. The results showed that:1) for mulched drip-irrigated farmland, the average daily evapotranspiration was highest at the flowering stage, followed by the maturity stage, and lowest in the seedling stage. With the growth of crops, the correlation between net radiative flux and daily evapotranspiration gradually decreased. The change trends of average daily evapotranspiration were the same as those of ordinarily irrigated farmland, whereas the average daily evapotranspiration of mulched drip-irrigated farmland was lower than that of ordinarily irrigated farmland at each stage. 2) Regarding the intraday flux in mulched drip-irrigated farmland, the net radiative flux peak was highest at the flowering stage, followed by that at the mature stage, and the minimum appeared at the seedling stage. In terms of turbulent flux, the latent heat flux was equivalent to the sensible heat flux at the seedling stage. Post the flowering period, the latent heat flux was significantly higher than the sensible heat flux, and this characteristic was the opposite at the mature stage. For the ordinarily irrigated farmland, the latent heat flux was higher than the sensible heat flux in all three crop growth stages. 3) The relationship between evapotranspiration and meteorological factors calculated by path analysis showed that temperature, humidity, and wind speed were the dominant factors influencing evapotranspiration. The lower limit of humidity determined the minimum evapotranspiration. The upper limit of wind speed and temperature determined the maximum evapotranspiration. The influence of wind direction was not significant on evapotranspiration. Sunflower farmland using mulched drip-irrigation has unique evapotranspiration features compared with ordinarily irrigated farmland, the amount of water saving exceeds 300 mm during the entire growth period.

Evaluation of grain quality of winter wheat and its response to meteorological factors

XIN Zhihong, GUO Jianping, TAN Kaiyan, LIU Kaiwen, YANG Rongguang, ZHANG Lihua, SUN Yi

2019, 27(8): 1205-1217. doi: 10.13930/j.cnki.cjea.190126

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Abstract:
Using field staging test method and the main winter wheat varieties as test materials, which are predominantly cultivated in the north and south wheat areas; variance analysis and principal component analysis methods to evaluate grain traits; and linear correlation, quadratic curve correlation, and stepwise regression to identify significant meteorological factors; a winter wheat quality prediction model was constructed in the form of meteorological factor-quality response curve to explore variations in the qualities of different wheat varieties in different areas and the meteorological factors that cause these variations. The varieties used in the experiment were 'Tanmai 98' and 'Shannong 18' planted in the northern wheat areas of Gucheng of Hebei Province and Tai'an of Shandong Province, respectively; and 'Xumai 33', 'Wanmai 52', and 'Zhengmai 9023' planted in the southern wheat areas of Xuzhou of Jiangsu Province, Suzhuo of Anhui Province, and Jingzhou of Hubei Province, respectively. Five wheat varieties were planted at different times (10 days in advance, suitable time, 10 days later, and 20 days later). The results showed that the tested wheat varieties were all medium protein varieties. Among the main quality traits, starch had the highest content and minimum variation, followed by protein regarding the content with medium variation, and fat with the lowest content but the maximum variation. The differences in protein and fat in the different areas was significant. The quality and its' stability of winter wheat were higher for winter sowing in the northern area and their quality traits were excellent. Each nutritional component was generally higher and stable in the north than in the south. The amino acid quality of the protein component was explained by three principal components. The content of the non-essential amino acid, glutamic acid, was the highest, whereas that of the essential amino acid, methionine, was the lowest; the amino acid quality of wheat was better in the northern than in the southern areas. The daily temperature difference in the northern area was more conducive to increasing the amino acid content. The fatty acids of the fat component were explained by four principal components. The content of the unsaturated fatty acid, linoleic acid, was the highest and that of the saturated fatty acid, pentadecene monoenoic acid, was the lowest. Temperature and humidity were the main meteorological factors affecting the grain quality of winter wheat. The protein or amino acid quality could be improved by adjusting the daily range of temperature in the flowering-mature period and reducing soil moisture; the fat or fatty acid quality could be improved by adjusting soil moisture and the minimum temperature in the flowering-mature period.

Response of seed germination and physiological mechanism of Vigna angularis and Dolichos lablab to salt stress

DENG Xiaohong, JI Lala, WANG Ruijie, LIU Xiao, YANG Shujun, GUAN Ping, WANG Jianjian

2019, 27(8): 1218-1225. doi: 10.13930/j.cnki.cjea.190227

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Abstract:
Soil salinization has an important effect on seed germination of plants; however, little attention has given to the effect of salt stress on the seed germination of legumes. The Vigna angularis variety 'Yuhongdou 2' and traditional Dolichos lablab variety were used to determine the germination percentage, germination potential, germination index, vigor index, radicle length, embryo length, and fresh weight, malondialdehyde (MDA) content, and superoxide dismutase (SOD) and peroxidase (POD) activity under different NaCl concentrations (0 mmol·L^-1, 20 mmol·L^-1, 40 mmol·L^-1, 60 mmol·L^-1, 80 mmol·L^-1, 100 mmol·L^-1) in an artificial climate chest. The goal of this study was to investigate the relationship between osmotic regulators, stress resistance enzymes, and salt tolerance of leguminous plants under NaCl stress. The results were as follows:1) salinity stress inhibited the germination index of V. angularis. Then germination percentage, germination potential, germination index, and vigor index of V. angularis decreased with increasing NaCl stress and was significantly higher than that of D. lablab. 2) The relative salt damage rate of V. angularis and D. lablab increased with the increase in NaCl concentration. When the NaCl concentration was 80 mmol·L^-1 and 100 mmol·L^-1, the relative salt damage rate of D. lablab was 96.58% and 96.67%, whereas the relative salt damage rate of V. angularis was 47.05% and 83.18%, indicating that the salt damage to V. angularis was less intense. 3) The radicle length, embryo length, and fresh weight of V. angularis and D. lablab seedlings decreased with the increase of NaCl concentration. When NaCl concentration was 100 mmol·L^-1, the radicle length of D. lablab was 0, and that of V. angularis was 0.23 cm. 4) With the increase of NaCl concentration, the content of MDA in the leaves of V. angularis and D. lablab increased, resulting in a gradual increase in cell membrane permeability, but the accumulation of MDA in V. angularis seedlings was lower than that in D. lablab, which indicated that the cell membrane of V. angularis leaves was less damaged. 5) Under NaCl stress, SOD activity of V. angularis and D. lablab increased significantly, but SOD activity of V. angularis was significantly higher than that of D. lablab. Under NaCl stress, POD activity of V. angularis increased significantly, but the POD activity of D. lablab decreased significantly. It was found that V. angularis could reduce the oxidative damage of the cell membrane and the accumulation of MDA by increasing SOD and POD activities, thus improving the germination ability of seeds. V. angularis was higher in salt tolerance than D. lablab under the same concentration of NaCl stress and can better adapt to a salt stress environment.

Soil water storage under conservation tillage based on LSTM neural network simulation in the Loess Plateau Gully Region of central Gansu

WANG Jun, LI Guang, LIU Qiang

2019, 27(8): 1226-1237. doi: 10.13930/j.cnki.cjea.180949

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Abstract:
In order to analyze the effects of soil water storage for four different tillage measures[traditional tillage (T), no-tillage with no straw cover (NT), traditional tillage with straw incorporation (TS) and no-tillage with straw cover (NTS)], the field research was conducted in the Loess Plateau Gully Region of central Gansu. The objectives of the study were to establish a prediction model for soil water storage based on Long Short-Term Memory (LSTM), and to evaluate the model's effectiveness using the long-term positioning experiment of the rotation sequence for spring wheat/pea (W/P) and pea/spring wheat (P/W) crops. In the experiment, monthly average temperature, monthly precipitation, monthly average radiation, monthly average evaporation and monthly crop water consumption constituted input factors, and value for soil water storage constituted the output factor in the prediction model. The results of the present study showed that:1) The water storage model based on LSTM neural network showed good applicability for predicting soil water storage, particularly in conservation tillage practice, in the Loess Plateau Gully Region of central Gansu. The average root mean square error and mean absolute error of the model simulation were 7.76 mm and 6.95 mm, respectively; moreover, the relative error was controlled between -5% and +5%. 2) In P/W rotation sequence, the soil water storage of various treatments increased by 1.09%-1.43% as compared to W/P. 3) Within different rotation sequences, water storage effect of NTS treatment turned out to be better than those for other three tillage measures. In W/P rotation sequence, the annual average soil water storage of NTS treatment was 2.89%, 1.70% and 2.46% higher than that of T, NT, and TS, respectively. In P/W rotation sequence, the average annual soil water storage of NTS treatment increased by 3.03%, 1.91% and 2.57%, respectively, compared to that of T, NT, and TS. 4) In the years with different precipitation, the soil water storage of NTS treatment was the highest, and this effect was markedly more significant in the dry year. The soil water storage of NTS treatment increased by 2.71%, 1.48% and 2.19%, on average, in the wet year, and it increased by 3.97%, 2.54% and 3.64%, on average, in the dry year as compared to the values recorded for T, NT and TS. 5) The water storage effect for conservation tillage measures varied with the season. There was obvious water storage advantage of conservation tillage measures during the early stages of crop growth (March-May). However, there was not significant between the results of conservation tillage measures and traditional tillage during the full growth stage (May-June). Nevertheless, the soil water storages for conservation tillage increased significantly during the late stage of crop growth (July). Going by the effect on soil water storage based on LSTM neural network, no-tillage mulching remains the best practice as well as the most suitable measure of protective tillage in the Loess Plateau Gully Region of central Gansu.

Prediction of minimum water level in Baiyangdian Lake based on precipitation

ZHAO Chunlei, QIAN Shuan, HUANG Qiang, WU Guoming, MENG Chengzhen

2019, 27(8): 1238-1244. doi: 10.13930/j.cnki.cjea.180781

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Abstract:
The planning outline of Xiong'an New Area clearly states that the proportion of blue-green space in the Xiong'an New Area will be stable at 70% in the future. Baiyangdian Lake is the largest wetland and water body in the Xiong'an New Area. Understanding and predicting changes in this water body is of great significance to ensure the production of domestic water and ecological security of the Xiong'an New Area. In order to predict the lowest water level of Baiyangdian Lake from October to April of the next year, and to guide water resources management and disaster prevention and mitigation of the Xiong'an New Area, a historical data regression method and a machine learning method were used to analyze the water level variation in the Baiyangdian Lake with different regional precipitation. It was found that the lowest water level of Baiyangdian Lake from October to April was highly correlated with both the mean precipitation in the current rainy season and the water level in May of that year. Based on this result, a method was established to predict the lowest water level in Baiyangdian Lake from the current rainy season until the next rainy season by using the precipitation data in the current rainy season and the water level before the current rainy season. According to the precipitation and water level data in Baiyangdian Lake from 2001 to 2017, the prediction model for the lowest water level was established. Furthermore, gradient descent algorithm was adopted for machine learning and training. After model verification, the lowest water level prediction model was developed based on the average rainfall from July to August/July to September and the water level in May as the prediction factors. The model was verified using the collected data; the fit of the model was acceptable as the simulated and predicted result errors were both below 5%. According to the Baiyangdian Lake water level in May 2018 and the average precipitation data of July to August/July to September 2018, the lowest water level of Baiyangdian Lake from October 2018 to April 2019 would be between 8.52 m and 8.38 m, which was higher than the lowest ecological water level of Baiyangdian Lake. According to the latest minimum water level from October 2018 to February 20, 2019, the model predicted result errors were below 4%. Thus, our model can predict the lowest water level of Baiyangdian Lake 3-7 months in advance, which provides a significant scientific basis to improve the comprehensive management and the rational allocation of water resources in the Xiong'an New Area.

Dry deposition flux of atmospheric heavy metals and its source apportionment in a typical farmland of Hebei Province

ZHANG Guozhong, HUANG Wei, PAN Yuepeng, GU Mengna, LYU Xuemei, NI Xue, HE Yuexin, LIU Bowen, WANG Yuesi, TIAN Shili

2019, 27(8): 1245-1254. doi: 10.13930/j.cnki.cjea.190092

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Abstract:
Atmospheric deposition is a major contributor of heavy metals contaminating the farmland, which endangers the quality of soil as well as agricultural products. Because of the paucity of relevant observational data, the dry deposition flux and sources of atmospheric heavy metals in agricultural areas have for long remained unclear. Based on a year of field observation in a typical farmland in Hebei Province, we measured the content of 25 elements in nine size-segregated particles. The dry deposition flux of atmospheric metal elements was estimated by employing resistance modeling. In addition, the sources of atmospheric metal elements were apportioned using the PMF model. The results indicated that there were large differences in the concentrations of 25 metals between the fine particles (D_P ≤ 2.1 μm, aerodynamic diameter, the same below), coarse particles (2.1 < D_P ≤ 9 μm), and giant particles (D_P>9 μm). Heavy metals (such as Zn, Cd, and Pb) were primarily concentrated in fine particles, whereas the crustal elements (such as Al, Fe, and Th) were primarily concentrated in coarse particles. The concentrations of most metals were higher in spring and in winter rather than in summer and autumn. Annual mean concentration of Cr was the highest among the heavy metals both in fine and coarse particles, followed by As, Zn, Pb, V, and Sb. Regarding the dry deposition flux, Cr also had the highest value of 350.7 mg·m^-2·a^-1, followed by As, Sb, and V, which were 153.4, 103.1, and 102.3 mg·m^-2·a^-1, respectively. The primary sources of atmospheric metal elements confined to the study area were road dust, industrial pollution, mineral dust, coal combustion and vehicle emission. The metals in the giant particles were primarily from dust source (62.0%), whereas the metals in the fine particles were primarily from coal, motor vehicles and industrial sources (totally 67.7%). With decrease in particle size, the contribution of anthropogenic pollution increased, thereby increasing the pollution risk (enrichment factor) of heavy metals. In conclusion, the study was critical in considering the input and sources of atmospheric deposition regarding regulation of farmland involving heavy metals.

Temporal and spatial distribution characteristics and factors influencing nitrate level in waters of a typical karst underground river system

SHEN Chunhua, HAN Zhiwei, GUO Yongli, ZHANG Shui, TU Han, GUO Fang

2019, 27(8): 1255-1264. doi: 10.13930/j.cnki.cjea.180970

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Abstract:
Karst underground rivers, which are widely distributed in karst areas in Southwest China, are important water resources. In recent years, with the continuous economic development, karst underground rivers have been rendered polluted to variable proportions. Nitrate pollution is a prominent and common problem in karst underground rivers. The high heterogeneity of karst aquifers makes it difficult to decipher the formation and distribution process of nitrate by simulation. The typical karst underground river system in Guancun Village, Daliang Town, Liuzhou City, Guangxi was selected as the study area. The land use was dominated by agriculture and the primary pollutant was nitrate. Multiple water samples were collected during the wet and dry seasons. The nitrate concentration and stable isotope variation characteristics were analyzed employing tracing and statistical methods. The results indicated that in the Guancun karst underground river system the trending of nitrate concentration during the wet and dry periods were consistent. The nitrate levels gradually increased from the Shanghu Cave to Xiahu Cave. On the contrary, the nitrate levels decreased from the Xiahu Cave to the underground river outlet. The waters of study area were obviously affected by human activities. The nitrates in the water primarily originated from agricultural and living sources. The input from the agricultural source had a profound influence on the nitrate concentration in the water. Due to the different sources of nitrate in the recharge water in different seasons, the distribution of nitrate concentration and stable water isotopes showed significant seasonal characteristics of the underground river system with the average nitrate concentration during wet season being greater than that during the dry season. As a result of the input of exogenous nitrate, mixing waters, and reduction processes, the distribution of nitrate concentration in karst underground river system also exhibit obvious spatial distribution characteristics. In this study, tracing method was employed to analyze the spatial and temporal distribution characteristics and the factors influencing nitrate levels in the karst underground river system. The conclusions arrived at would be significant in formulating non-point source pollution prevention strategies in karst areas.

Residues of three insecticides in tea leaves, soil and rainwater runoff

ZHAO Zhide, LI Haitao, LIANG Tao

2019, 27(8): 1265-1274. doi: 10.13930/j.cnki.cjea.180814

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Abstract:
Insecticide residues in tea have attracted much attention, and the means to reduce the level of residues in tea and the surrounding environment is a serious issue. Reducing the usage or dose of insecticide may be a viable option to address this problem. We analyzed the possible dietary intake risks and the effects of regular dose versus reduced dose of bifenthrin, deltamethrin, and chlorfenapyr on their residues in fresh tea leaves, soil, and rainwater runoff in tea plantations of the green tea variety 'Fenglv' (Camellia sinensis Yutakmitor). Field trials using bifenthrin, deltamethrin, and chlorfenapyr were conducted in the tea plantations of Yucha Village, Shaoxing City, Zhejiang Province in China. The local regular dose and 30% dose reduction of bifenthrin, deltamethrin, and chlorfenapyr were considered as the experimental treatments group, which included dosages of bifenthrin at 150 mL·hm^-2 and 105 mL·hm^-2, deltamethrin at 750 mL·hm^-2 and 525 mL·hm^-2, and chlorfenapyr at 750 mL·hm^-2 and 525 mL·hm^-2, respectively. Samples of tea leaves and soil were collected on the 1^st, 3^rd, 7^th, and 10^th day after spraying, and rainwater runoff was similarly collected on the 4^th and 8^th day after spraying. The data related to insecticide residues in all the collected samples were used to evaluate the behavioral pattern of residue and risk assessment of the three insecticides. The results indicated that no significantly different residues present in fresh tea leaves was observed sprayed with regular dosage and 30%-reduced dose. The half-lives of bifenthrin in fresh tea leaves sprayed with regular dosage and reduced dosage were 5.89 d and 4.61 d, respectively, and the half-lives of deltamethrin with regular dosage and reduced dosage were 5.75 d and 2.55 d, respectively; and those of chlorfenapyr with regular dosage and reduced dosage were 3.72 d and 2.70 d, respectively. The residue levels of bifenthrin, deltamethrin, and chlorfenapyr in soil were lower than the primary standard value (≤ 0.05 mg·kg^-1) of organochlorine insecticide, hexachlorocyclohexane, as stated in Environmental Quality Standard for Soils (GB15618-1995). The residue levels of bifenthrin and chlorfenapyr in rainwater runoff were lower than the value (≤ 0.005 mg·L^-1) of organochlorine insecticide hexachlorocyclohexane as stated in Standards for Drinking Water Quality (GB5749-2006). The residue levels of deltamethrin in rainwater runoff were lower than the value (≤ 0.02 mg·L^-1) of deltamethrin as stated in Standards for Drinking Water Quality (GB5749-2006). Dietary exposure risk assessment referred to the risk assessment of exposure to insecticides and other harmful substances ingested through food. The results related to the assessment of risk of dietary exposure to the three insecticides in tea indicated that the maximum exposures of bifenthrin, deltamethrin and chlorfenapyr were 0.5×10^-4-1.7×10^-4, 1.0×10^-6-7.3×10^-6, 1.0×10^-5-8.3×10^-5 mg·kg^-1(bw)·d^-1. Risk quotient was expressed as the ratio of maximum exposure to acceptable daily intake. The risk quotients of bifenthrin, deltamethrin and carbonitrile were 0.005-0.017, 0.000 2-0.001, 0.000 2-0.003, respectively, which meant the risk to consumers was within an acceptable range. Reducing sprayed dosages of the above three insecticides in the tea plantations made no significant differences to the residues in tea and the environment.

Circular development modes of modern agriculture and animal husbandry in Tibet

ZHANG Huaguo, TANG Xiaoyu

2019, 27(8): 1275-1283. doi: 10.13930/j.cnki.cjea.180931

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Abstract:
The circular economy is a novel concept and method for the effective utilization of waste resources of agricultural and animal husbandry. Tibet has special natural attributes, such as a diversified elevation gradient, varied climate, great daily temperature range, and a large complexity and diversity of natural resources. It is of great importance to utilize natural resources to their full potential through the establishment of effective modes of agricultural and animal husbandry production, thereby allowing sustainable and efficient development in Tibet. This paper has summarized the circular economy development modes of agriculture and animal husbandry in Tibet, comprising the clean production of highland barley; the combination of forestry, agriculture, and animal husbandry; the comprehensive utilization of agricultural and animal husbandry wastes; the alpine grassland greenhouses; and the co-cultivation of fish and vegetables. The clean production of highland barley was based on the principle of "reduce, reuse, and recycle". The combination system of agriculture, forestry planting, and animal husbandry was characterized by high-efficiency ecological reproduction, scientific planting, and expansion of agricultural products. The comprehensive utilization system of agricultural and animal husbandry wastes was the optimized combination and rational utilization of different resources reclaimed from the wastes of crop planting and animal breeding. The alpine grassland greenhouses were a comprehensive system of grassland protection, grass production, and greenhouse grass cultivation, which balanced grassland resources and animal breeding requirements to meet the climate of Tibet. The co-cultivation of fish and vegetables used a courtyard-based system, with greenhouse production as a core element to promote the production and cultivation and horticultural crops through the symbiogenesis of fish and vegetables. The five circular modes were typical patterns of agricultural and animal husbandry development in different ecological areas in Tibet. Each mode had its' own development attributes and characteristics that may be used for reference, popularization, and application. Finally, based on the analysis results, four measures and suggestions for promoting the circular patterns of agricultural and animal husbandry development in Tibet were proposed.

Advances in research on fertilization and decision-making behavior of farmers in the context of green development

WANG Heng, YI Xiaoyan

2019, 27(8): 1284-1292. doi: 10.13930/j.cnki.cjea.180976

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Abstract:
Ecological vitalization is one of the "Five Vitalizations" and so is an inherent requirement of rural vitalization. To promote ecological vitalization, the green development of agriculture should be increased, and green and environmentally friendly fertilization should be adopted under circumstances of excessive use of chemical fertilizer. To achieve green fertilization, in this study, we reviewed the relevant literatures. Firstly, this paper summarized the connotations of green fertilization behavior, including the choice of fertilizer in agreement with the concept of green development, the choice of green production technology, the improvement of fertilizer utilization efficiency, and the reduction of environmental pollution caused by excessive fertilization. Most research on green fertilization had been based on planning behavior theory and a household's behavior theory; therefore, in this study, we systematically determined the decision-making mechanism of green fertilization behavior. Farmers were rational and they made choices based on their own information and identification of the external environment. Next, the paper summarized the influencing factors on green fertilization behaviors from four aspects:plot characteristics, external policy environment, individual and family characteristics, and farmers' perception. Finally, through a literature review, it was found that the research content of green fertilization needed to be expanded, and the main subject of research needed to be extended. There are two main trends in the future research on green fertilization:1) the content of the research should continue to expand with the progress of green fertilization technology; 2) the main subject of the research should focus on the green fertilization behavior of new agricultural operators.

Effect of irrigation method on farmers' planting decision and the economy: A case in Zhangbei County, Hebei Province

LIN Huifeng, LIU Moucheng, JIAO Wenjun, HE Siyuan, YANG Lun, MIN Qingwen

2019, 27(8): 1293-1300. doi: 10.13930/j.cnki.cjea.180796

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Abstract:
Owing to drought and water shortage in North China, water-saving irrigation is considered an effective measure to reduce agricultural water consumption. Domestic and foreign studies have shown the effect of water-saving irrigation technology on water saving and crop yield increase at the field scale. However, from the perspective of the socio-economic-ecological compound system, the shift of irrigation methods can change the farmers' planting decision and agricultural production behavior, which has a complex effect on the regional agricultural water use. Taking Zhangbei County of Hebei Province as an example, through field investigation and model simulation, we analyzed the effect of irrigation methods conversion on farmers' planting decisions and welfare. It was found that high-efficiency irrigation methods improved water productivity of crops by 25.0%-347.7%. Under the same input of other factors and the same amount of water resources, higher yields and benefits were obtained through the adoption of high-efficiency irrigation methods. In the case of scarce water resources, the same output was achieved with relatively less water resources. Secondly, when farmers adopted high-efficiency irrigation practices, 88.9% of the local farmers grew more water intensive cash crops with higher yields to obtain higher investment returns. At the same time, farmers also tended to shift from minimizing material inputs to maximizing profits. For crops with lower yields, compensating the cost of irrigation facilities with the benefits of using high-efficiency irrigation methods was often difficult, and farmers were less motivated to change irrigation practices. Thirdly, changes in irrigation methods affected the input and output of agricultural production, increased the construction cost of irrigation facilities by 6.6%-16.2%, the input of pesticides by 2-4 times, and decreased labor input by 20.6%-59.3%. With the economic situation of yearly increase in labor costs, the reduction in labor input owing to drip irrigation and the increase in labor productivity were likely to be the primary reasons why farmers were willing to choose high-efficiency irrigation methods. The results of the study explained why farmers choose to change the irrigation method, how the individual planting decisions of farmers change, and the economic effect on farmers after the transition. As the transformation of individual farmers' irrigation methods and their planting decisions had a direct effect on the water use of regional agricultural production, the results of this study provided a scientific basis for further analysis of the effect of water-saving irrigation on regional agricultural production.

2019 Vol. 27, No. 8