中国生态农业学报(中英文)

Effects of organic waste application on soil greenhouse gas emissions of a winter wheat field

LI Chunxi, LI Sisi, SHAO Yun, MA Shouchen, LIU Qing, WENG Zhengpeng, LI Xiaobo

2019, 27(6): 815-824. doi: 10.13930/j.cnki.cjea.180913

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Abstract:
Exploring the impact of returning organic materials to the soil on greenhouse gas emission characteristics of winter wheat fields can help to improve economic and environmental consequences. Based on 3 modes of organic material return (JF:straw return and cow dung; J:straw return; JZ:straw return and mushroom dregs) and 2 nitrogen levels (N1:243 kg·hm^-2; N2:216 kg·hm^-2), the fluxes of N₂O, CO_2, and CH₄ in winter wheat fields were monitored using the static chamber method and gas chromatography, and the effects of the different fertilization measures on cumulative greenhouse gas emissions and warming potential of wheat fields were studied. During the experimental period, the amount of fuel consumed by farm machines and the power consumed during irrigation and fertilizer application were recorded and transformed to their carbon equivalents using a transformation coefficient. In addition, crop yield and aboveground biomasses were measured and carbon sequestration calculated. The total GWP under each of the 6 treatments were estimated based on the identified parameters of the greenhouse effect. The results indicated that wheat fields served as sources of N₂O and CO₂ and sinks of CH₄. Nitrogen application and adequate irrigation increased CO₂ and N₂O in the soil, but weakened the characteristics of CH₄ as an atmospheric absorption sink. The total amounts of N₂O and CO₂ emitted were highest in the JF treatment, at 3.5 kg (N₂O-N)·hm^-2 and 19 689.67 kg (CO₂-C) hm^-2 respectively, and the absorption value of CH₄ in this treatment was 5.33 kg (CH₄-C) hm^-2, significantly higher than in both of the JZ and J treatments. The total amounts of N₂O and CO₂ in each treatment increased, and the total amount of CH₄ decreased, with an increase in the nitrogen application rate. The GWP of JFN2, JN2, and JZN2 treatments were all negative, which indicated that the farmland ecosystem is an atmospheric carbon sink when organic materials were returned to the field; nitrogen was reduced by 20%, and the carbon interception by wheat was 1 038-2 024 kg·hm^-2. The GWP values were positive and the JZN2 treatment-treated wheat yield was 8 061 kg·hm^-2, significantly higher than that of the JFN2 treatment. In summary, JZN2 treatment could ensure wheat yield and had the most favorable environmental effects, and thus was the best fertilization management model for winter wheat in this region

Overwintering population density and cold tolerance of Bemisia tabaci in greenhouses and open fields in the Fujian Province

YAO Fengluan, ZHENG Yu, DING Xueling, LU Xuesong, HE Yuxian, WENG Qiyong

2019, 27(6): 825-835. doi: 10.13930/j.cnki.cjea.181073

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Abstract:
In order to clarify the overwintering mechanisms of sweetpotato whitefly[Bemisia tabaci (Gennadius)] in open fields and greenhouse vegetable production systems in Fujian Province, China, and to provide a theoretical basis for integrated pest management of B. tabaci, field surveys were conducted at six sites (Jian'ou County of Nanping City; Jiangle County and Sanyuan District of Sanming City; Minhou County of Fuzhou City; Xinluo District of Longyan City; and Longhai County of Zhangzhou City) in January 9-12 and February 21-24, 2017. Sixteen B. tabaci host plants belonging to six families were found, which included the following vegetables:broccoli (Brassica oleracea var. botrytis L.), tomato (Lycopersicon esculentum Mill.), and eggplant (Solanum melongena L.), and broadleaved weeds:Solanum nigrum L., Conyza canadensis (L.) Cronq., Ranunculus sieboldii Miq., and Ageratum conyzoides L. For broccoli grown in open fields, significantly greater densities of overwintering B. tabaci were found in January than in February, and substantially greater densities of B. tabaci were detected on postharvest broccoli residuals than those on broccoli at the rosette and the head development stages. There were significantly higher densities of overwintering B. tabaci in fallow greenhouses than in productive greenhouses. Markedly greater densities of overwintering B. tabaci were found in greenhouses than in open fields, regardless of whether the host plants were vegetables or broadleaved weeds. All life stages for overwintering B. tabaci were found in greenhouses across the province and in open fields in Zhangzhou, but eggs and pseudopupa were found in open fields in the Nanping and Sanming areas, where the temperature was low. Overwintering B. tabaci cryptic species MEAM1 and MED were detected in vegetables; in all, there were 57 and 111 individuals, respectively, of the two cryptic species. We inferred that the usage of greenhouses may promote the establishment of the cryptic species MED in the Fujian Province. We then carried out laboratory experiments to test the cold tolerance of B. tabaci and to test the suitability of broadleaved weeds for the development of B. tabaci. We demonstrated that eggs and old nymphs of B. tabaci could tolerate cold stress better than adults and young nymph. B. tabaci had comparable generational survival rates on broadleaved weeds S. nigrum (79.3%) and R. sieboldii (81.1%), lower than that on B. oleracea var. botrytis (83.6%), a common crop widely grown in Fujian Province during winter. The generational developmental duration of B. tabaci was significantly shorter on S. nigrum (16.7 d) than on B. oleracea var. botrytis (18.9 d), which was similar to that on R. sieboldii (18.8 d), implying that broadleaved weeds serve as important potential alternatives to vegetable crops as host plants for B. tabaci in winter. In summary, B. tabaci can overwinter successfully in the open fields in Fujian Province, and the establishment of greenhouses promotes the development of overwintering B. tabaci.

Effects of UV-B radiation on entomopathogenic nematode survival and pathogenicity

QIAN Xiujuan, ZHANG Shipeng, XIE Pan, LIU Changzhong

2019, 27(6): 836-844. doi: 10.13930/j.cnki.cjea.180561

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Abstract:
Entomopathogenic nematodes (EPN) possess many positive attributes as biocontrol agents. They are safe to humans and generally safe to other non-target organisms. To investigate the effects of ultraviolet radiation exposure on EPN, we studied the effects of 20 or 40 W UV-B radiation for different time lengths (30, 60, 90, or 120 min) on the virulence of EPN infective juveniles (IJs) to Galleria mellonella, including 9 strains from 4 species (Steinernema feltiae, S. kraussei, Heterorhabditis brevicaudis, and H. megidis) isolated from Gansu Province. The results showed that there were no differences among the strains in the survival rate of IJs with and without 30 min UV-B irradiation. The virulence of IJs varied among strains after exposure to 20 W ultraviolet radiation for 30 min: virulence of two strains (S. felitiae 0639C and S. feltiae 0663TD) was increased (P < 0.05), that of one strain (S. feltiae 0661YM) decreased (P < 0.05), and that of all others (H. brevicaudis 0641TY, H. megidis 0627M, S. felitiae 0639C, S. felitiae 0619HT, S. kraussei 0663HT, and S. kraussei 0657L) showed no significantly change (P > 0.05). For example, when measured at 32 h after infection, the mortality rate of host insects infected by S. felitiae 0639C increased significantly, from 13.3% to 73.3% (P < 0.05), whereas that of insects infected by S. felitiae 0661YM decreased significantly from 66.7% to zero (P < 0.05). At the same time, treating S. felitiae 0639C and 0663TD with UV affected host mortality 24 h after exposure to IJs:for S. felitiae 0639C, host mortality at 24 h was greater in the 40 W treatment than in either control or the 20 W treatment; for S. felitiae 0663TD, host mortality at 24 h was greater in the 20 W treatment than in either the control or the 40 W treatment. Ultraviolet radiation duration (30 min, 60 min, 90 min, or 120 min exposure) had no effect on the pathogenicity of S. felitiae 0663TD or S. felitiae 0639C (P > 0.05). Therefore, the following conclusions were drawn:All of the 9 tested strains of EPN isolated from Gansu Province had some tolerance to UV-B radiation, and, in particular, S. felitiae 0622L had a high tolerance to ultraviolet radiation. In addition, ultraviolet radiation had a variable impact on the pathogenicity of EPN in Gansu Province, as there were differences among different species and strains. For example, 20 W UV-B radiation for 30 min enhanced the pathogenicity of S. felitiae 0663TD, whereas it significantly weakened that of S. felitiae 0661YM. Ultraviolet radiation stimulated S. felitiae 0663TD and S. felitiae 0639C to infect and kill host insects more quickly, although the radiation intensity that optimized the 24-h mortality rate varied between the two strains. After 48 h, however, there was no significant difference in the pathogenicity of S. felitiae 0663TD and S. felitiae 0639C between the different radiation intensities (20 and 40 W). Additionally, IJs of S. felitiae 0663TD and S. felitiae 0639C both had high pathogenicity after 48-72 h, regardless of the radiation intensity (20 W or 40 W) or the duration of exposure (30, 60, 90, or 120 min). These findings will shed more light on using entomopathogenic nematodes under ultraviolet radiation stress.

Response of suitable distribution of citrus in Sichuan Province to climate change

LIN Zhengyu, CHEN Qiang, DENG Liangji, LI Xiao, HE Peng, XIONG Ying

2019, 27(6): 845-859. doi: 10.13930/j.cnki.cjea.180983

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Abstract:
Citrus is one of the main fruit products of Sichuan Province, China. Due to favorable market expectations and the low occurrence of citrus diseases in Sichuan basin, there is a trend of blind expansion of citrus cultivation. However, climate change has had a significant impact on the spatial distribution of crops, and has caused the instability and vulnerability of citrus production in Sichuan. In order to optimize the citrus production space, this study established a model of the relationship between the distribution of areas suitable for growing citrus and environmental variables based on the maximum entropy model (MaxEnt), used the ROC curve to determine the model's accuracy, and used the jackknife method to screen out the dominant environmental variables. The distribution of citrus-suitable areas in Sichuan Province in 1980 and 2010 were compared using ArcGIS, revealing the changes in citrus-suitable areas over nearly 30 years of climate change. The results showed that the dominant environmental variables determining citrus suitability in Sichuan were climatic variables characterized by light, heat, and water. During these 30 years, the trend of climate warming and drying in Sichuan Province changed the structure and function of the regional ecosystem, and caused temporal and spatial variations in citrus-suitable areas. There were two broad changes in the spatial pattern of citrus-suitable areas from 1980 to 2010. First, the highly suitable areas tended to migrate to the north. The boundary of moderately suitable areas located between Chengdu Plain area and northeastern Sichuan Province moved to the southeast. Second, the suitability grade changed in a stepwise fashion. The change in the grades in marginally and moderately suitable areas was obvious. In 2010, the total highly suitable area was about 42 200 km², moderately suitable areas covered about 41 900 km², and the least suitable areas covered 44 000 km²; most of the province was not suitable. Using this data of the highly suitable areas, government departments can create policies to increase the quantity of citrus in the south Sichuan region and the southern Shengdu Plain. This study objectively assessed the changes in suitability for planting citrus in Sichuan Province under climate change, and provided a scientific basis for the optimization of citrus space. Application of the maximum entropy model is valuable for accurate simulation and prediction of crop distribution and can be important in guiding crop climatic suitability zoning. However, appropriate environmental variables, spatial scale, and species sampling locations should be selected for different regions and crops to reduce systematic cumulative error and improve the precision of crop climatic suitability zoning.

Response of interspecific competition and complementarity of maize/pea intercropping to reduced tillage and high-density planting

REN Xuling, TENG Yuanyuan, WANG Yifan, YIN Wen, CHAI Qiang

2019, 27(6): 860-869. doi: 10.13930/j.cnki.cjea.180850

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Abstract:
Through the study of an interspecific relationship, the effects of reduced tillage and high-density planting was analyzed in a maize/pea intercropping system. The research could provide a theoretical basis for further optimization of intercropping technology. The study, conducted in 2016-2017 in the Hexi Oasis Irrigation Area, used a maize/pea intercropping system as the research setup. Two tillage patterns were measured:conventional tillage and reduced tillage. Simultaneously, maize was planted at low, medium and high density to study the effects of different treatments on the competitiveness of maize/pea intercropping systems. Also, the recovery ability of maize after the pea harvest was analyzed to reveal the interspecies relationship and the correlation with intercropping production. The results showed that the land equivalent ratio of different intercropping treatments was higher than 1, indicating that these intercropping treatments resulted in an increased yield. Compared with conventional tillage, reduced tillage increased the yield of maize/pea intercropping system by 5.79%. Under reduced tillage conditions, the yield of intercropping system at medium density was considerably increased by 8.37% and 9.09% relative to low-density and high-density conditions, respectively. This observation indicates that combining reduced tillage with a medium-density plantation further increased the yield of a maize/pea intercropping system. Reduced tillage combined with a medium-density plantation enhanced the competitiveness of maize/pea intercropping:the competitiveness was 36.56% and 20.17% higher relative to the low-density and high-density treatment, respectively. The enhanced competitiveness formed the basis of the enhanced maize intercropping recovery effect. After the pea harvest under reduced tillage conditions, maize displayed a significant recovery growth effect, which was 10.30%-47.11% higher than that under conventional tillage conditions. The correlation between the grain yields of intercropping system and the average competitiveness of pea relative to maize during the whole growth period was quadratic function. The integration of reduced tillage and a medium-density planting technology in the maize/pea intercropping model provides the potential for an intercropping system to increase the yield by regulating the interspecific relationship.

Effect of maize/soybean relay strip intercropping system on soybean morphology, chlorophyll fluorescence, and yield in Sichuan area

CHEN Yuankai, FENG Lingyang, MUHAMMAD Ali Raza, FAN Yuanfang, CHEN Junxu, YONG Taiwen, YANG Wenyu, YANG Feng

2019, 27(6): 870-879. doi: 10.13930/j.cnki.cjea.181014

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Abstract:
Maize/soybean relay strip intercropping can make efficient use of light and land resources to improve yield per unit of land area. The research was conducted to explore the influence of row spacing of maize on the soybean canopy light environment and morphological traits. Two maize varieties, semi-compact (Chuandan 418) and compact (Rongyu 1210), were used to study the efficient utilization of land resources to enhance yield and yield components. Three arrangements of 20 cm, 40 cm, and 60 cm of maize narrow row spacing were set with same width of strip intercropping (SI) belt and soybean row spacing. Solely soybean with a fixed strip width of 200 cm was planted as a control. The light transmittance, morphology, photosynthetic pigment, fluorescence parameters, biomass of soybean and grain yield of both maize and soybean were analyzed. The results showed that the light transmittance and red light/far-red light (R/FR) ratio of the soybean canopy decreased with an increasing narrow row spacing of maize. The same trend was visible in the stem diameter, node number, and dry matter of stem and leaves. The maximum values were measured in the maize narrow row spacing width of 20 cm. Compared with the control, the stem diameter, node number, dry matter of stem and leaves of soybean were significantly reduced under intercropping with two maize varieties, while the second internode length and main stem length of soybean were significantly increased. Photosynthetic pigments contents in intercropped soybean leaves gradually decreased with the increase of narrow row spacing of maize, and were lower than monocultured soybean. The fluorescence parameters of soybean leaves of F_v/F_m, NPQ, F_q'/F_m', and F_q'/F_v' first increased and then decreased, while a reverse trend was visible for F_o with the increase of narrow row spacing of maize. The soybean rapidly recovered after exposure to a full light environment by harvesting the maize crop. The difference in soybean morphological and physiological indexes between intercropping and monoculture was reduced. However, owing to the shading effect of maize in the early growth stage, a significant difference in the grain yield was observed between different intercropping treatments. A benefit analysis of the maize/soybean intercropping system demonstrated that the comprehensive yield was the highest for a narrow row spacing arrangement of maize (40 cm). The yield of maize and soybean were on average 8 559.52 kg·hm^-2 and 1 717.60 kg·hm^-2, respectively. The average land equivalent ratio was 1.57. There was no significant effect on soybean morphological and physiological indexes under intercropping conditions between both types of maize in this experiment. It can be concluded that selecting compact or semi-compact maize varieties and moderately reducing the narrow row spacing of maize can significantly improve the growth of soybean in a maize/soybean strip intercropping system, and result in higher biomass and yield.

Comparison of yield and nitrogen use efficiency-related traits of cotton cultivars released during the last sixty years

BAIDENGSHA·Maimaitiaili, SUN Liangbin, LIU Zhongshan, FENG Gu

2019, 27(6): 880-889. doi: 10.13930/j.cnki.cjea.180929

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Abstract:
The cotton breeding process is closely related to the improvement of soil fertility, innovation of culturing technology, climate change, and so on. The selection of lint yield-related traits is connected to the selection of traits of nutrient uptake and use efficiency. To understand the impact of the cotton breeding process on the nutrient efficiency of cotton, 22 cotton varieties released from the 1950s to 2013 in Xinjiang were grown together in a field with a randomized block design. The biomass, lint yield, N content and N use efficiency of each cultivar were analyzed. The results showed that there were significant differences in N use efficiency and partial factor productivity among the analyzed varieties. The biomass of the seeding stage, befuddling stage, flower and boll stage, and boll opening stage were 2.87-11.67 g, 20.8-38.6 g, 42.3-88.3 g, and 58.2-120.4 g per plant, respectively. Coefficients of variation were 30.2%, 8.2%, 5.6%, and 5.6%, respectively. For the yield components, the coefficient of variation of the boll number per plant was the highest (29.0%), and lint percent the lowest (1.0%). The variation of N use efficiency was 1.12-4.47 kg·kg^-1, and the partial factor productivity of N (PFPN) was 2.87-11.67 kg·kg^-1, with the coefficients of variation of 35.3% and 27.6%, respectively. It showed that PFPN had a significant correlation with biomass and lint cotton yield. The cotton economic coefficient had not changed significantly during the past 60 years and remained in a range of 0.20-0.24 g·g^-1. The lint yield of cotton increased gradually from 853.6 kg·hm^-2 in the 1950s to 1 569.8 kg·hm^-2 in 2013. There were significant changes in PFPN and N use efficiency:these factors increased from 4.12 kg·kg^-1 to 5.78 kg·kg^-1, and from 2.32 kg·kg^-1 to 3.07 kg·kg^-1, respectively. Based on lint yield components, N use efficiency and PFPN, the cotton varieties were divided into three groups:a high N efficiency group, a medium N efficiency group, and a low N efficiency group. Cluster analysis showed that 'Xinluzao 50' and 'Xinluzao 57' were the high N efficient varieties. Compared with the low-efficiency cultivar, the high N-efficiency cultivar had a higher lint yield and biomass. It can be concluded that high-yield cultivar selection could improve N use efficiency and PFPN of cotton.

Classification evaluation and fiber quality characteristics of different types of cotton varieties using similarity-difference analysis method

TANG Shurong, WEI Shoujun, WEI Jingyan, MENG Junting, GUO Ruilin, FENG Xiaojian

2019, 27(6): 890-900. doi: 10.13930/j.cnki.cjea.181011

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Abstract:
For an accurate analysis of the regional distribution characteristics, the fiber quality traits of 531 candidate varieties in national cotton regional trials in China between 2005 and 2014 were analyzed to achieve comprehensive evaluation of hybrid and conventional cotton varieties by using similarity-difference analyses method in crop-breeding fields. The results showed that:1) conventional cotton varieties with fiber quality qualified as type Ⅰ, type Ⅱ, and type Ⅲ accounted for the total conventional varieties of 1.58%, 28.42%, and 14.74%, whereas the proportions of type Ⅰ, type Ⅱ, and type Ⅲ for hybrid cotton were 0.59%, 19.94%, and 10.56%, respectively. The identical degree of the conventional and hybrid cotton cultivars in the Yellow River Valley (YeRV) was estimated to be 0.869 3 and 0.888 8, the identical degree of hybrid cotton in the Yangtze River Valley (YaRV) was 0.864 3, and that of cotton varieties in the Northwest Inland (NWI) was 0.890 5. 2) The fiber quality of conventional cotton in the NWI was better than that of hybrid cotton in the YeRV, and the fiber quality of the latter was better than that of conventional cultivars in the YeRV and hybrid cotton in the YaRV. There were no significant differences in conventional cultivars in the YeRV and hybrid cotton in the YaRV. The YaRV is suitable cotton planting area for medium-long length and high-strength of fiber, and high-micronaire hybrid cotton varieties. The NWI is suitable for planting high-quality conventional cotton varieties with long and fine quality as cotton spinning high yarn industry base. In brief, the fiber quality traits of conventional cotton in the NWI were proven to have the most potential, which can be an important reference value to optimize high-quality cotton regional layout and to adjust the planting structure in China.

Response of leaf stomata and photosynthetic parameters to short-term drought stress in cotton (Gossypium hirsutum L.)

WANG Kaili, GAO Yanzhao, LI Shan, ZHANG Menglu, WU Zhihao, LIU Liantao, SUN Hongchun, LI Cundong, ZHANG Yongjiang

2019, 27(6): 901-907. doi: 10.13930/j.cnki.cjea.180928

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Abstract:
Studying the response of stomata to drought stress can help to understand the behavior of stomatal regulation and improve water utilization efficiency of crops. This study was conducted in an artificial climate chamber using the cotton cultivar 'Guoxin 9'. Four concentrations of PEG 6000[0 (control), 1.5%, 3%, and 4.5%] were added into the nutrient solution. Stomatal morphological parameters, gas exchange parameters, and chlorophyll fluorescence kinetic parameters were measured every two days from the first day to the seventh day of treatment. The results showed that with the elongation of treatment time, the values of leaf water potential, stomatal length, stomatal width, stomatal aperture, net photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r), intercellular CO₂ concentration (C_i), maximal photochemical efficiency (F_v/F_m), and actual photochemical production quantum (Yield) all decreased to some extent, whereas stomatal density and non-photochemical quenching coefficient (NPQ) increased. Similar trends were observed in different treatments with an increase in drought stress. After 5 d and 7 d of treatment, leaf water potential, stomatal length, stomatal width, P_n, G_s, T_r, and C_i with 1.5%, 3%, and 4.5% PEG 6000 were significantly different from those with the control (P < 0.05). The magnitudes of the declines in leaf stomatal length, G_s, and T_r were 1.17%-2.61%, 61.62%-69.09%, and 37.62%-67.48%, respectively. Correlation analysis revealed that significant positive correlations existed among leaf stomatal length, width, and aperture (P < 0.01). Stomatal width was not significantly correlated with stomatal density. Stomatal length, width, and aperture were positively correlated with P_n and Yield (P < 0.01), negatively correlated with NPQ (P < 0.01), and not significantly correlated with G_s, T_r, or F_v/F_m. These results suggested that the simulated drought induced by PEG 6000 may result in cotton stomatal closure and an increase in stomatal density, along with decreases in net photosynthetic rate and stomatal conductance. Compared with Yield and NPQ, F_v/F_m was less sensitive to drought stress in cotton.

Effects of water supply on photosynthesis and fluorescence characteristics of sweet potato[Ipomoea batatas (L.) Lam.] leaves and comparison of light response models

WU Haiyun, GUO Qilin, WANG Jinqiang, LI Huan, LIU Qing

2019, 27(6): 908-918. doi: 10.13930/j.cnki.cjea.181046

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Water supply plays a vital role in the growth and yield of sweet potato. In this paper, the edible sweet potato 'Yanshu 25' was used to study the photosynthesis-light response process and fluorescence characteristics of sweet potato leaves under different water treatments. Different models were used to study the light response process, and the effects of different water treatments on photosynthesis and fluorescence characteristics of sweet potato were analyzed. The results showed that:drought and flooding treatment significantly reduced the net photosynthetic rate (P_n), stomatal conductance (G_s), and transpiration rate (T_r) of sweet potato leaves; at PAR ≤ 1 000 μmol·m^-2·s^-1, the decrease of P_n under drought and flooding treatment was induced by stomatal restrictions, and at PAR > 1 000 μmol·m^-2·s^-1, the decrease of P_n was induced by non-stomatal restrictions. The fluorescence parameters indicated that the light capture and absorption capacity of photosystem Ⅱ (PS Ⅱ) of sweet potato leaves decreased under drought and flooding treatment, while the heat dissipation increased. The modified rectangular hyperbola model demonstrated the best fit among all the light response models and matched the light saturation point. The model was, therefore, suitable for simulation of photoresponse simulation under different soil water environments. The model parameters showed that the initial quantum efficiency (α) of sweet potato leaves ranged from 0.039 to 0.055 under different water treatments, falling within the theoretical range of 0-0.125. The sweet potato leaves demonstrated significant photo-saturation and photo-inhibition under drought and flooding treatment, resulting in a reduced light utilization capacity. The light utilization capacity under flooding treatment was lower than that under drought treatment. It can be concluded that the modified rectangular hyperbola model is the optimal model to analyze light response changes of sweet potato under different water conditions. Both the drought and flooding treatment damage the photosynthetic system of sweet potato and reduce its photosynthetic capacity. Flooding is more likely to reduce the light utilization capacity of sweet potato leaves when compared with drought, and high light intensity increases the degree of water stress of sweet potato.

Daily standardized antecedent precipitation evapotranspiration index (SAPEI) and its adaptability in Anhui Province

CHEN Jinhua, YU Weiguo, LIU Ruina, YUE Wei, CHEN Xi

2019, 27(6): 919-928. doi: 10.13930/j.cnki.cjea.180835

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Abstract:
Agricultural drought and waterlogging are two of the most compelling problems affecting agricultural productivity and efficiency. At present, most of the widely used drought and waterlogging indices are based on ten-day, monthly, and seasonal scales. Their timeliness and accuracy are still far from the desired levels that would enable a sustainable means of preventing and controlling agricultural drought and waterlogging disasters. Based on the data of 78 meteorological observing stations in Anhui Province, selected as the transitional zone between the North Semi-humid and South Humid climates, a daily standardized antecedent precipitation evapotranspiration index (SAPEI) was constructed by fitting the daily antecedent precipitation evapotranspiration index (APEI) series with a 3-parameter log-logistic distribution. In addition, its feasibility and adaptability were analyzed in representative stations that were selected in different dry and wet zones, namely, North of the Huaihe River, Between the Huaihe River and Yangtze River, and South of the Yangtze River. The results showed that the empirical probability distribution curve of representative stations' APEI series highly corresponded with the theoretical log-logistic distribution curve. Representative stations' daily SAPEI curve could describe the changes in farmland water budget in the presence/absence of rain. In the case of the rapid change in drought and flood on June 8 and 28, 2011, SAPEI's drought and waterlogging grade and change trends were in good agreement with soil moisture in the same period. Spatial distribution of drought, waterlogging frequency, and annual mean values of accumulated index based on winter wheat whole development stage's SAPEI was primarily distributed latitudinally. These distribution characteristics conformed to the actual distribution of drought and waterlogging in Anhui Province. The 0-value line of annual mean SAPEI (I_SAPEI) in the winter wheat whole development stage was located north of the "Between the Huaihe River and Yangtze River" zone and along the eastern and southern foot of the Dabie Mountains. The area covered by negative values was drier and was the main area planted with winter wheat in Anhui Province, and the other area covered by positive values was more humid. In conclusion, the daily-scale SAPEI and its accumulated index could reflect the temporal distribution of precipitation and the impact of daily rainfall amount, and accurately depict the changes in drought and waterlogging and the cumulative effects of drought and waterlogging processes in different regions of Anhui Province. Therefore, SAPEI not only retained the advantages of standardized precipitation evapotranspiration index (SPEI) such as strong regional applicability, dimensionless character, and the ability to reflect the influence of temperature, but also had higher timeliness and sensitivity by modifying the precipitation evapotranspiration index from a monthly or seasonal scale to a weighted cumulative precipitation evapotranspiration index at a daily scale. SAPEI can be used in daily dynamic monitoring and the assessment process of drought and waterlogging in Anhui Province.

Variation in characteristics of light and heat resource utilization efficiency of double-season rice and its impact on meteorological yield along the Yangtze River in Anhui Province

YUE Wei, CHEN Jinhua, RUAN Xinmin, CHEN Xi, CHEN Yantao, WANG Zhen

2019, 27(6): 929-940. doi: 10.13930/j.cnki.cjea.180865

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Abstract:
To be further acquainted with the variation in characteristics of the light use efficiency and the heat use efficiency for double-season rice along the Yangtze River basin in the Anhui Province, and the effect of light resources and temperature resources on meteorological yield for double-season rice, this study analyzed the variation characteristics of light resources and heat resources, resource use efficiency, and the influence on meteorological yield on early-season rice, late-season rice, and double-season rice. To analyze these, methods including linear fitting, M-K mutation test, correlation analysis, and regression analysis, based on data for daily average temperature and daily sunshine hours from 1961 to 2017 from the nineteen meteorological stations along the Yangtze River basin in the Anhui Province, and the yield for both early-season rice and late-season rice from 1961 to 2006 in seven counties, which are the main production area for double-season rice, were used. The results showed that the amount of total solar radiation significantly decreased (P < 0.01) by 30.5 MJ·m^-2, 69.8 MJ·m^-2, and 86.6 MJ·m^-2, on average, per decade, during the growth of early-season rice, late-season rice, and double-season rice, respectively; the accumulated temperature ≥ 10℃ showed a significant increasing trend, and increased, on average, by 39.1℃·d, 24.4℃·d, and 14.7℃·d per decade in early-season rice, late-season rice, and double-season rice, respectively; the light use efficiency and heat use efficiency both significantly increased (P < 0.01). The rise in light use efficiency was 0.040%, 0.103%, and 0.083% per decade for early-season rice, late-season rice, and double-season rice, respectively. And the heat use efficiency increased by 0.141 kg·℃^-1·d^-1·hm^-2 per decade for early-season rice, 0.39 kg·℃^-1·d^-1·hm^-2 per decade for late-season rice, and 0.315 kg·℃^-1·d^-1·hm^-2 per decade for double-season rice. Significant improvements in the utilization efficiency of light resources and heat resources of rice were mainly a result of the substantial increase in yield. For early-season rice, the meteorological yield showed an extremely significant positive correlation (P < 0.01) with total solar radiation and a significant positive correlation (P < 0.05) with accumulated temperatures above 10℃. Although the meteorological yield for late season rice was significantly positively correlated to total solar radiation, it was insignificantly correlated to the accumulated temperatures above 10℃ in their growth duration. The total solar radiation was the main factor that affected the meteorological yield of early-season rice and late-season rice, whereas the accumulated temperature above 10℃ was the second most influential factor. The effect on the change in light and heat resources on early-season rice was more obvious compared with that on late-season rice. Therefore, given the trend in decreasing total solar radiation and increasing accumulated temperatures above 10℃, for the purposes of improving the utilization efficiency of light resources and heat resources for double-season rice along the Yangtze River basin in the Anhui Province, to achieve a high and stable annual yield of rice, it is suggested that some field management measurements should be adopted, such as the selection of cultivars with high photosynthetic efficiency, or improved film seedlings or greenhouse seedling management, which can increase the accumulated temperatures in the early rice-growing season and appropriately prolong the growth period of late-season rice, and determining a suitable planting density.

Evolution and driving forces of cultivated land quantity in Xiamen City using niche theory

GAO Xueli, ZHANG Jian, YANG Dewei, LIU Bin

2019, 27(6): 941-950. doi: 10.13930/j.cnki.cjea.181032

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Abstract:
It is vital to identify the changes in cultivated land quantity and its effect on regional land use structure to understand the urbanization process and regional sustainability. To determine the spatiotemporal evolution characteristics and driving mechanism of the cultivated land quantity, the niche was measured for land use types and six districts in Xiamen City from 1990 to 2015. The results identified by the niche ecostate-ecorole, expansion-compression, breadth, and entropy measurements showed that:1) the cultivated land quantity niche in Xiamen declined gradually from 1990 to 2015, with an average annual compression rate of 1.45%, which was directly related to the expansion of the construction land quantity niche. The evolution of cultivated land quantity niche in Xiamen City was in the late stagnating stage. However, it was faster than that of the national cultivated land niche ecostate-ecorole, possibly due to the rapid urbanization process. 2) The change in cultivated land quantity niche in the six urban districts was consistent with that in Xiamen City, and followed an overall decreasing trend. There was a large difference in the cultivated land area occupancy rate and the decrease rate in cultivated land area in each district. The evolution characteristics of the cultivated land quantity niche in each district could be classified into three distinct categories. First, the breadth of cultivated land quantity niche in the Huli and Siming districts were smaller than that of the construction land. The cultivated land ecostate was small in the six districts and had little interannual change, and the construction land ecostate rose steadily. Second, the breadth of the cultivated land quantity niche in the Jimei and Haicang districts had undergone a change from greater to lower than that of the construction land. The cultivated land ecostate was in the middle of the six districts, and the construction land ecostate increased greatly. Third, the range of change in the breadth of cultivated land and construction land quantity niche was the smallest in the Tong'an and Xiang'an districts. The cultivated land ecostate was at a high level among the six districts, and the construction land ecostate in the Tong'an district showed the largest increase. 3) In the context of rapid urbanization and intensive industrialization, the difference in comprehensive benefit niche between the cultivated land and construction land became gradually wider in Xiamen City, which drove the evolution of the cultivated land quantity niche. Among the difference in benefit niche from economic, ecological, and social aspects, the differences in the economic benefit niche for cultivated land and construction land were the largest, which indicated that the economic benefits were the major benefits for the change in the quantity of cultivated land and construction land. This paper attempted to describe the change in cultivated land quantity in Xiamen City by using the niche theory. This study could improve our understanding of cultivated land protection and the changes in land use structure to support sustainable land resource management.

Environmental risks and precautions in pig husbandry relocation in China

HAN Dongmei, JIN Shuqin, HU Yu, WU Tianlong, CHEN Yanli

2019, 27(6): 951-958. doi: 10.13930/j.cnki.cjea.181029

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Abstract:
Livestock breeding is not only a pillar industry of China's agricultural and rural economy, but also the most important source of agricultural pollution. Under the influence of environmental protection and industrial policies, pig husbandry in the southern provinces of China has largely reduced in recent years. These provinces were originally the traditional pig husbandry regions. Meanwhile, the pig husbandry is booming in the northern provinces of China. This relocation from the southern to the northern part of China is just a microcosm of the transition in Chinese agriculture. Although there is some rationality based on the availability of resources and environmental characteristics, there are still huge environmental risks associated with the process of pig husbandry relocation. Based on this argument, this study analyzed the potential environmental risks and environmental injustice caused by the current relocation of pig husbandry and the following conclusions were drawn. Firstly, the climatic conditions and farming system in the northern part of China are not suitable for resource utilization of cultured manure. Secondly, it may pose a huge potential risk to the water quality and water supply in the area. Moreover, the breeding density in some areas might be too large, which is beyond the carrying capacity of the land and threatens the local ecological environment. The ecological environment of Northeast China is as important as that of South China. To avoid damaging the environment in the northern part of China, we should establish and optimize an inter-regional ecological compensation mechanism to reduce the environmental unfairness between northern and southern China. The region of pig breeding should also be scientifically optimized to avoid uneven distribution. Moreover, farming and pig husbandry should be combined organically by an accompanying reward and punishment policy. Finally, strict environmental protection policies must be implemented, and innovative pollution reduction methods should also be introduced.

Effect of capital endowment on farmers' decision-making in protecting cultivated land in a rice-growing area:An empirical study based on a double-hurdle model

CUI Yue, ZHAO Kai, HE Jing, QU Meng

2019, 27(6): 959-970. doi: 10.13930/j.cnki.cjea.190034

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Abstract:
Improving the fertility of cultivated land and promoting green development of agriculture are strategic choices for rural revitalization strategies. As a direct part of cultivated land utilization, farmers' decision-making regarding farmland protection directly affects green agricultural production and food safety. Oryza sativa is one of the most important food crop varieties in China. This study divided farmers' capital endowment into 4 facets:human capital, economic capital, natural capital, and social capital endowments. Using survey microdata from 394 households in Qingtongxia (one of China's high-yield, high-quality rice areas), a double-hurdle model was employed to distinguish farmers' decision-making of participation in farmland protection into two stages, participation willingness and degree of participation. The influence of capital endowment on participation in cultivated land protection decision-making in this rice-growing area was then assessed. The objective of this study was to provide references for scientifically formulating relevant policies for arable land protection in rice-growing areas and ensuring the development of a green agricultural economy. The results showed that:1) most farmers were willing to participate in farmland protection, but their willingness to pay for farmland protection was relatively low. The proportion of farmers willing to participate in the protection of cultivated land was 73.86%, but the average amount they were willing to pay was only 3 100.65¥·hm^-2. 2) Capital endowment had a strong correlation with the farmers' willingness to participate in farmland protection and degree of participation. Specifically, human capital endowment (education level and agricultural training), economic capital endowment (household income and agricultural machinery input), and social capital endowment (social relationship and social participation) had positive effects on the farmers' willingness and the degree of participation in farmland protection. Natural capital endowment (farmland endowment and degree of fragmentation) had a positive impact on the farmers' willingness to participate in farmland protection and a negative impact on their degree of participation. 3) Awareness of the importance of cultivated land protection only promoted the farmers' willingness to participate in the protection of cultivated land, whereas the degree of understanding of cultivated land protection policy promoted both the farmers' willingness to participate in the protection of cultivated land and their degree of participation. Farmers' awareness of farmland protection and their degree of policy understanding had positive effects on their willingness to participate in the protection of cultivated land as well as their degree of participation. Some suggestions had been put forward, including establishing and improving economic compensation policies for farmland protection; encouraging farmers to actively invest in environmentally friendly technologies for sustainable development of green agricultural production, thereby enhancing the participation of farmers in the protection of cultivated land; actively setting up agricultural cooperatives and farmland protection organizations to promote the collective protection and control of arable land; further improving the rural education and training system to instruct new farmers about the development of green agriculture; strengthening publicity for farmland protection in rice-growing areas; and promoting the correct interpretation of rural grassroots organizations' and farmers' policies on farmland protection, thus raising the farmers' support for these policies.

Study on dynamic changes in ecosystem service values in Qinglong County based on coefficient correction

LIU Qian, LI Ge, ZHANG Chao, ZHAO Li, ZHU Yongming

2019, 27(6): 971-980. doi: 10.13930/j.cnki.cjea.180927

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Abstract:
Ecosystem service value is an important index to reflect the ecological environment condition and ecological benefit of a region, and the change of ecosystem service value is of great significance to regional ecological construction and sustainable development. In reference to the research of Xie Gaodi and others, the Costanza ecosystem service value assessment model was used to study the Qinglong County of Hebei Province. The regional differences coefficient and the correction coefficient of social development were used to adjust the table of equivalent factors of the ecological service value. A new dynamic assessment model for ecosystem service value was constructed, and the dynamic changes in ecosystem service value in the Qinglong County were evaluated and analyzed from 2006 to 2016. The results of the study indicate that:1) the total ecosystem service value of Qinglong County in 2006-2016 showed a trend of increase-decrease-increase, with a total increase of 4.507 billion Yuan, an annual change of 451 million Yuan per year, and an annual average change rate of 4.54%. 2) Among different land types, forest land and garden land provided the highest value of ecosystem services, followed by water area and cultivated land, and unused land and wetland had the lowest value. 3) The value structure of the ecosystem service function of the whole research area remained stable, and the ranking was as follows:biodiversity conservation > water conservation > climate regulation > gas regulation > soil formation and protection > raw materials > waste disposal > recreation culture > food production. There were differences in the value of ecosystem services between different regions and the values were continually changing depending on the development of a society. Compared with previous static assessment models on ecosystem service values, this study took into account the impact of location conditions and social development in the study area. The model is more suitable for a small-scale county and can reveal the dynamic change mechanism and effect of a regional ecosystem service value.

2019 Vol. 27, No. 6