中国生态农业学报(中英文)

Production and release mechanism of N₂O in agricultural soils irrigated with acid mine drainage

CHANG Yimeilin, TANG Changyuan, LI Xing, LI Rui, CAO Yingjie

2019, 27(1): 1-10. doi: 10.13930/j.cnki.cjea.180568

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Abstract:
Acid mine drainage (AMD) is mostly untreated or not up to standard level before directly drained into rivers for irrigation, causing severe pollution of agriculture eco-environments. Metal pollution had been widely reported in extensive fields including the red soil region in South China. As we have known, N₂O emitted from agricultural systems was one of the important causes of global greenhouse effects. However, there has been poor knowledge of potential changes in N₂O evolution in polluted fields. In this study, four agricultural soil profiles from sugarcane and paddy fields were used to track the changes in N₂O emission and sources of heavy metal polluted soils irrigated with AMD (Shangba Village, Wengyuan County, Guangdong Province) and then compared with unpolluted soils irrigated with natural water (Lianxin Village, Wengyuan County, Guangdong Province). The physical/chemical parameters and contents of heavy metals in the soils, N₂O concentration and stable nitrogen and oxygen isotope compositions were analyzed to determine the contribution of nitrification and denitrification of N₂O and the reduction ratio of N₂O. Our results showed that there was slightly higher N₂O concentration of the same crop in AMD irrigated area than in unpolluted soil irrigated with natural water, and higher soil N₂O concentration in sugarcane fields than in rice fields. The production of N₂O from denitrification was 71.29%, which was higher than that from nitrification in surface soil (0-30 cm) in sugarcane fields in areas irrigated with AMD. N₂O reduction ratio in the soil profile in AMD irrigation area decreased gradually with increasing depth. There was only 15.54% N₂O reduction to N₂ at the peak of N₂O concentration. However, the average ratio of N₂O reduction to N₂ in sugarcane fields irrigated with natural water was as high as 49.80%. Limited N₂O reduction led to high levels of N₂O residues in the soil. Studies showed that AMD irrigation changed the production and release of N₂O by changing pH, heavy metal content and moisture content of agricultural soils. N₂O production and reduction studies carried out using combined nitrogen and oxygen isotope compositions clarified potential risks of irrigated agricultural soils with AMD. This provided the scientific basis for future restoration works in polluted soils.

Community characteristics of soil ammonia oxidizing bacteria after different fertilizer applications

REN Lingling, LI Xiuling, LIU Lingzhi

2019, 27(1): 11-19. doi: 10.13930/j.cnki.cjea.180645

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Abstract:
Studies about ammonia oxidizing bacteria (AOB) have mainly focused on the topsoil and little has remained known about community distribution in the subsoil. There therefore has remained the need to understand the impact of long-term fertilization on AOB abundance, community structure and vertical distribution in order to deepen the exploration of microbial mechanisms of nitrogen (N) transformation and to develop sound fertilization regimes for sustainable soil quality in the study area and beyond. Thus, a long-term (1987-2015) fertilization experiment was set up in the brown earth in Shenyang Agriculture University, Liaoning Province, China. Four treatments were set, no fertilizer (CK), low N fertilizer (N₂), high N fertilizer (N₄) and low N fertilizer plus organic mature (M₂N₂). Soil samples were collected at three different depths (0-20 cm, 20-40 cm and 40-60 cm). The soil physico-chemical properties, 16S rDNA and AOB-amoA gene abundance (real-time PCR, qPCR) and AOB community structure and diversity (denaturing gradient gel electrophoresis, PCR-DGGE) were investigated. While soil pH decreased, the content of soil ammonium N (NH₄⁺-N) increased by 70.5%-939.21% and that of nitrate N (NO₃^--N) by 253.20%-625.48% in the fertilization treatments over CK treatment. Also while soil pH increased, the contents of soil NH₄⁺-N and NO₃^--N decreased with increasing soil depth, except for N₂ treatment. The results of qPCR showed that fertilization treatments increased AOB abundance, but decreased total bacterial abundance compared to CK treatment. AOB amoA gene abundance was generally higher at the 0-20 cm than at the 20-40 cm and 40-60 cm soil layers. AOB abundance peaked in the N₄ treatment, with 9.65×10⁵ copies per g dry soil. The Shannon diversity (H), evenness (E_H) and richness (S) indexes of AOB from DGGE fingerprints responded increasingly significantly (P < 0.05) to fertilization regimes and soil-fertilization interactions with increasing soil depth. Although the tested diversity indexes were highest in the surface soil (0-20 cm), N fertilizer treatments (N₂, N₄ and M₂N₂) significantly reduced AOB diversity indexes. Based on cluster analysis of the DGGE fingerprints, AOB community structure in the soil varied with fertilization treatments and soil depth. Three soil depths of high N fertilizer (N₄) treatment was grouped together clearly. For other treatments, it was grouped according to soil depth with no discernible difference in AOB community structure among CK, N₂ and M₂N₂ treatments. The 0-20 cm and 20-40 cm deep soils under fertilizer treatments formed single cluster with no less than 57% similarity, while 40-60 cm soil layer formed another cluster. Redundant gradient analysis (RDA) further showed that NO₃^--N (P=0.027) was the key factor that shaped AOB community under different fertilization treatments. The results indicated that AOB number and community structure diversity after long-term fertilization significantly varied with fertilization treatment, and showed obvious vertical distribution characteristics. Compared with chemical fertilizer (N₂ and N₄) application, organic manure plus chemical fertilizer (M₂N₂) more favorably improved soil pH and maintained AOB community diversity in the subsoil.

Effect of rotation on nematode community diversity in rhizosphere soils and yield of sweet potato

QIAO Yuejing, LIU Qi, ZENG Zhaohai, HU Yuegao, GAO Zhiqiang

2019, 27(1): 20-29. doi: 10.13930/j.cnki.cjea.180524

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Sweet potato rot nematode (Ditylenchus destructor) is a severe disease that can cause significant loss of sweet potato yield and that can destroy biotic community diversity in rhizosphere soils. In this study, nematode community structure in rhizosphere soils under sweet potato were investigated to verify the impact of rotation cropping patterns on rot nematode disease and the feasibility of denatured gradient gel electrophoresis (DGGE) in soil nematode research. The experiment was conducted on a long-term continuous sweet potato field in Lulong County, Hebei Province in 2014 to (→) 2015, where sweet potato rot nematode disease was seriously epidemic. The cropping patterns were included A1 (fallow→sweet potato), A2 (maize-fallow→sweet potato) A3 (maize-rye→sweet potato), A4 (bean-fallow→sweet potato), A5 (bean-rye→sweet potato) and CK (continuous sweet potato cropping). The nematodes were separately extracted from sweet potato rhizosphere soil in May, July and September in 2015, and the ITS genes analyzed using PCR-DGGE. The results showed that compared with continuous cropping, crop rotation significantly increased the diversity of nematode community, and decreased the population of sweet potato rot nematode in rhizosphere soil (P < 0.05). Community structure of nematodes in rhizosphere soil under sweet potato was stabilized by winter rotation with rye (A3 and A5). Based on PCR-DGGE, 9 genera of nematodes were detected in the rhizosphere soil of sweet potato-Ditylenchus, Dorylaimus, Aphelenchoides, Cephalobus, Pratylenchus, Criconemella, Belonolaimus, Aphelenchus, and Diplogasterida. While Ditylenchus was the dominant genus in all the cropping patterns, Dorylaimus, Aphelenchoides and Cephalobus were the main genera. Crop rotation increased sweet potato yield by 42.08%-55.83% and decreased disease index by 22.72%-30.79%. However, different crop rotations had no significant difference on sweet potato yield and disease index. The population of Ditylenchus destructor was significantly related with sweet potato yield and disease index at harvest time (P < 0.05). Therefore, crop rotation significantly increased the diversity of nematode communities in sweet potato rhizosphere soils and sweet potato yield. And DGGE was proved to be a useful tool to detect soil nematode community. For the economic and ecological effects, bean-rye→sweet potato was the best rotation pattern for the study area.

Effect of agricultural landscape composition on natural enemy population of corn borer

BIAN Zhenxing, GONG Lingchun, GUO Xiaoyu, YU Miao

2019, 27(1): 30-41. doi: 10.13930/j.cnki.cjea.180221

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The agricultural landscape with high proportion and diversity of non-cropped habitats is the key to maintaining agricultural biodiversity. It is a hypothesis that the natural enemy population and types of corn borer could increase by complex and high composition of non-cropped habitats in cornfields. To clarify the relationship between non-cropped habitats proportion and natural enemy, this study investigated the effects of composition of non-cropped habitats on natural enemy population of corn borer in Changtu County in the Northeast China Plain. Twenty plots (φ=600 m) were selected and classed into five groups based on the proportions of non-cropped habitats (0-10%, 10%-20%, 20%-30%, 30%-40% and 40%-50%). The samples of natural enemies of corn borer were collected by the pitfall trap method. The families of enemies were identified using stereomicroscope. Then principal component analysis was used to classify the main types of non-cropped habitats in the region. Stepwise regression model was used to fit relation curve of non-cropped habitat composition (ratio and type) and population of natural enemies of corn borer. Then the optimal model was selected based on the Akaike's Information Criterion (AIC) for effects of different proportions of non-cropped habitats on natural enemy population of corn borer. Results showed that natural enemy population of corn borer increased at first and then decreased with increasing proportion of non-cropped habitats. Natural enemy population of corn borer was highest[with the optimal model of AIC_{minimum value}=4.24, Y=b₀-b₁D + b₂PC2, PC2 (β=3.787, P=0.005)] when the proportion of non-cropped habitats was 20%-30%. This optimal model implied that there was significant positive correlation between natural enemy population of corn borer and the composition of non-cropped habitats dominated by woodland. There was also significantly negative correlation between natural enemy population of corn borer and the landscape diversity index D. Other models[PC1 (β=1.957, P=0.000)] for 20%-30% proportion of non-cropped habitats implied that significant positive correlation existed between natural enemy population of corn borer and the composition of non-cropped habitats dominated by grassland and village. Under other proportions of non-cropped habitats, the optimal models suggested that corn filed neighboring woodland or other crops fields was beneficial for increase of natural enemy population of corn borer. In conclusion, the study showed that natural enemy population of corn borer was highest when the proportion of non-cropped habitats was 20%-30%. Non-cropped habitats dominated by woodland, grassland, village or in intercropped patterns attracted natural enemies of corn borer in farmlands with different proportions of non-cropped habitats. The study further provided theoretical basis for the prevention and control of corn borer by ways of landscape ecology.

Analysis of microbial community structure of litter with different fermentation levels in pig-on-litter system using phospholipid fatty acid biomarkers

ZHENG Xuefang, LIU Bo, ZHU Yujing, WANG Jieping, LAN Jianglin, CHEN Qianqian

2019, 27(1): 42-49. doi: 10.13930/j.cnki.cjea.180548

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Pig-on-litter system is a new pig-raising technology that can reduce environmental pollution. In this system, micro-organisms are generally considered as the key factor. In order to determine the change in microbial community during fermentation and to set up basic data for scientific management of pig-on-litter system, microbial community of litter with different fermentation levels was analyzed using phospholipid fatty acid (PLFA) biomarkers. Fermentation levels of litters were divided into three grades (1^st, 2^nd and 3^rd) using the chromatic aberration (△E) method. Both surface (0-15 cm) and inner layer (30-45 cm) litters of each fermentation level were sampled. PLFA composition of each sample was determined by the Sherlock MIS 4.5 system. The results showed that the method used was sufficient to detect total 61 kinds of PLFA biomarkers. The most and least kinds of PLFA biomarkers occurred in litters with the 2^nd and 3^rd fermentation levels, respectively. PLFA biomarkers displayed the same order of distribution abundance in all samples-bacteria > fungi > actinomycetes. The contents of PLFAs that were referable to bacteria, fungi, actinomycetes, G⁺, G^- and total PLFA in the surface layer samples were all higher than those in the inner layer samples; being highest in surface layer litters with the 1^st fermentation level. Fermented litter had significantly higher content of total PLFA than unfermented litter (CK) (P < 0.05). The highest fungi/bacteria and G⁺/G^- ratios were for surface layer litter with the 3^rd and 2^nd fermentation levels, respectively. Diversity analyses indicated that the maximum values of the Shannon index and Pielou index were for litter of the 2^nd fermentation level and the maximum values of the Simpson index were for surface layer litter of the 3^rd fermentation level. Based on cluster analysis, the samples were clustered into three groups for Euclidean-distance of 223.15. Samples with the same fermentation level were clustered together. Also based on principal component analysis, surface layer and inner layer samples of the 1^st fermentation level were clustered into one lone group, while the other samples were clustered into other several groups. Put together, litters with different fermentation levels had different microbial community structures. The maximum values of microbial content and species were in surface layer litter with the 1^st and 2^nd fermentation levels, respectively. Moreover, surface layer and inner layer litters of the same fermentation level had similar microbial communities.

A review of progress in research and scaling-up methods of crop water use efficiency

JIANG Hanbing, ZHANG Yucui, REN Xiaodong, YAO Jiawei, SHEN Yanjun

2019, 27(1): 50-59. doi: 10.13930/j.cnki.cjea.180501

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Increasing crop water use efficiency (WUE) is an effective way of alleviating agricultural water scarcity. The scaling up of water use efficiency is the basis for mutual representation, verification and application of achievements at various scales. This paper summarized the main observation technologies of leaf-scale, plant-scale and plantation-scale WUE. At present, the widely used methods include leaf gas exchange measurement, carbon isotopic discrimination, pot weighing method, eddy covariance system, etc. Carbon isotope discrimination provides a new idea for the study of long-term cumulative effects of crop water use conditions which is also available at every scale. We reviewed the impacting factors and the related physiological mechanisms of crop water use at multi-scale WUE. Crop WUE at each scale was regulated by stomatal conductance and crops usually regulated stomatal aperture to response to temperature, humidity, CO₂ and other interactive environmental factors. Stomatal optimization theory essentially sought optimal state of stomata under complex environmental conditions to coordinate the process of photosynthesis and transpiration of crops. Instantaneous WUE at leaf scale cannot directly represent water use status at larger spatial and temporal scales. Thus we also discussed the feasibility of scaling up WUE from leaf to plant to plantation scales and analyzed the main limiting factors at each scale transfer. We pointed out the difficulties in transfer from leaf to plant in terms of WUE. It mainly focused on three points-uncertainty in leaf and light distributions, plant nighttime respiration and transpiration, and plant physiological adjustment mechanisms. Research on leaf to plant to plantation scale transfer was mainly influenced by canopy internal resistance, boundary layer resistance, soil evaporation, night transpiration of crops, crop water use and assimilates partitioning mechanism. Finally, existing research achievements on scale transfer were summarized. At present, WUE scale transfer depended mainly on improvement of models and observation methods. The transfer from leaf to plant focused on separation of water use during day and night and photosynthetic characteristics of each part of the crop. For transfer from leaf to plant to plantation scale, studies explored efficient ways. First, studies understood the structure of evapotranspiration and confirmed the characteristics of water use. Second, studies used the relationship between stomatal and canopy conductance as breakthrough point via models to explore transfer mechanisms. Actually, several models had already been established and applied in this respect.

Effects of soil nitrogen and phosphorus contents on ecological stoichiometry of wheat leaf

WANG Fankun, XUE Ke, FU Weiguo

2019, 27(1): 60-71. doi: 10.13930/j.cnki.cjea.180133

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Ecological stoichiometry is a science that studies the balance of energy and multiple chemical elements in the ecosystem. The contents of C, N and P and the related ecological stoichiometric ratios (N:P, C:N and C:P) in plants can be used to judge the level of nutrient supply during plant growth period. In this paper, a technical guidance for precise fertilization in wheat production was provided by determining the response of ecological stoichiometry of major elements in wheat leaf to different soil nitrogen and phosphorus conditions. The weak gluten wheat variety 'Yangmai 15' and strong gluten wheat variety 'Zhenmai 168' that were widely cultivated in the study area were selected as test materials. Using pot experiment, 16 treatments of different nitrogen and phosphorus gradients were set up and the ecological stoichiometric ratios of N:P, C:N and C:P at jointing, booting and grain-filling stages analyzed for different treatments. The results showed that:1) at jointing and booting stages, when soil N:P was 7.04-8.73, N:P of the two wheat varieties leaves were higher. At grain-filling stage when soil N:P was 8.73-10.42, N:P of the two wheat varieties was higher. There was significant positive correlation between N:P in wheat leaf and N:P in soil, but the correlation became weaker with wheat growth. 2) At a low soil N level (108.4 mg·kg^-1), leaf C:N of the two wheat varieties was at a higher level. There was a significant negative correlation between C:N in wheat leaf and N:P in soil indicating that C:N in wheat leaf decreased with increasing of N:P in soil. 3) At low soil P level (29.6 mg·kg^-1), C:P of the two wheat varieties leaves were higher as well. There was extremely significant negative correlation between C:P in wheat leaf and P content of soil, which suggested that C:P in wheat leaf decreased with increasing soil P content. The above results indicated that different supply levels of N and P in soil significantly changed leaf ecological stoichiometric ratios of different wheat varieties. Therefore, the steady-state characteristics of ecological stoichiometric ratio can be used as an important reference indicator for nutrient regulation in wheat production.

Degradation property of oxo-biodegradable plastic film and its mulching effect on soil moisture, soil temperature and maize growth in rainfed Northeast China

SUN Shijun, ZHANG Wangwang, LIU Cuihong, ZHOU Jiaqi, ZHU Kunlun

2019, 27(1): 72-80. doi: 10.13930/j.cnki.cjea.180550

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The growing use of plastic film in agriculture has significantly increased crop production as it positively enhances the soil environment. However, the massive disposal of this material has as well increased environmental risk. One way to solve this problem is by developing a substitutable mulching film such as biodegradable ﬁlms that are ultimately convertible into water, carbon dioxide and soil organic matter by micro-organisms. Oxo-biodegradable plastic film is a newly developed biodegradable film that can increase soil water, soil temperature and crop yield and it also has satisfactory degradation properties. In this study, series of experiments were conducted to determine the degradation properties (degradation rate, tensile strength and elongation) of oxo-biodegradable plastic films and the effects of different mulching treatments on soil moisture, soil temperature, maize growth and maize yield. The mulching experiment was conducted using three kinds of oxo-biodegradable plastic films with different ingredients and different degradation rates (Degradation a, Degradation b and Degradation c) and common plastic film, and using un-mulched field as the control. Maize was ridge-cultivated and films covered all soil surface. The results showed that:1) biodegradation rate of different oxo-biodegradable films met soil and crop requirements for high yield production. Degradation rates of Degradation a, Degradation b and Degradation c after maize harvesting were respectively 14.2%, 10.0% and 6.5%. While the tensile strength on the ridge tops of Degradation a, Degradation b and Degradation c were decreased respectively by 30.4%, 20.3% and 19.1%, elongation decreased by 10.4%, 13.5% and 5.0% under mulching in the field for 120 days. Meanwhile, tensile strength of side ridges decreased respectively by 59.0%, 50.7% and 45.6% for Degradation a, Degradation b and Degradation c and elongation by 71.7%, 55.6% and 51.0%. Decrease in degradation was significantly different for different films. Furthermore, decrease in degradation properties of the film on ridge side was significantly more than that on the top of ridge. 2) Compared with the control, oxo-biodegradable plastic film mulching significantly increased soil temperature in the 5-25 cm soil layer and soil moisture in the 0-40 cm soil layer on early maize growth period. Degradation a, Degradation b and Degradation c treatments increased average soil temperature in the 5-25 cm soil layers respectively by 4.5℃, 4.4℃ and 4.4℃. Soil moistures under Degradation a, Degradation b and Degradation c treatments were increased respectively by 3.2%, 2.9% and 2.2% in the 0-40 cm soil layer. 3) Oxo-biodegradable plastic film mulching promoted maize growth, enhanced early maize emergence and shortened overall growth period by 5-7 days. Also the height and LAI of maize under oxo-biodegradable plastic film mulching were significantly higher than those under un-mulched treatment and slightly better than that under common plastic film mulching. 4) Compared with the control treatment, three oxo-biodegradable plastic films and common plastic film treatments increased ear length, ear diameter and 100-kernel weight of maize. At the same time, Degradation a, Degradation b and Degradation c and common film treatments significantly increased maize yield by 14.3%, 14.3%, 10.4% and 13.2%, respectively. Based on the study, oxo-biodegradable plastic film mulching significantly increased soil temperature and moisture and enhanced maize yield more than common film mulching, with degradation rate adjustable by changing ingredients. The results provided scientific basis for the replacement of common plastic films by oxo-biodegradable plastic films and for the development, popularization and application of oxo-biodegradable plastic films in Northeast China.

Tomato growth as affected by soil extract of continuously cropped okra

YAN Yinan, LIU Mingyue, ZHOU Xiangzhu, LIN Zhiqiang, ZHANG Weiqing, XU Ru, WANG Shubin, CHEN Lu, SHANG Chunyu, LIN Yongwen, HOU Maomao, LIN Yizhang, ZHONG Fenglin

2019, 27(1): 81-91. doi: 10.13930/j.cnki.cjea.180495

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Single tillage system, single variety and excessive pursuit for economic efficiency have exacerbated the barriers of continuous cropping of greenhouse tomato (Lycopersicum esculentum). Although its root secretions can cause autotoxicity, okra (Hibiscus esculentus) is a new vegetable with great economic prospect in China. Rotation is an effective way to avoid continuous cropping obstacles, however, in practice, rotation of tomato and okra inhibited growth and impeded fruiting of tomato. To clear the hypotrophy between tomato and okra, soils of okra continuously cropped for 1 year and 10 years were used to conduct an experiment with tomato seeds and seedlings. Water extracts of two soils were diluted into 1 000 mg·mL^-1, 2 000 mg·mL^-1 and 3 000 mg·mL^-1 to treat tomato seeds, and into 125 mg·mL^-1, 250 mg·mL^-1 and 500 mg·mL^-1 to cultivate tomato seedlings. Physiological and biochemical analysis and seed root and stem morphology observation of tomato were conducted to investigate the influence on the below-ground and above-ground growth of tomato to determine the effects of okra soil extracts on tomato seed germination and seedling growth. The results showed that under the same concentration of soil extract, with continuous cropping years increase, the main root of tomato deformed with more but thin lateral root. Tomato seedling also showed increased root forks and root activity significantly lowered and with abnormal and green-lost top leaves compared to the control (total nutrient solution, CK) treatment. The activity of antioxidant enzyme, and MDA and proline contents were also significantly different from CK. Under different concentrations of soil abstracts for the same continuous cropping year, main root deformity appeared gradually in germinated tomato seeds as the concentration of soil extract increased. Also lateral roots increased and most relatively thin, tomato seedling rootlets increased and root tip number and rootlets were respectively 1 146 and 3 321 for the 1-year and 2 291 and 1 947 for the 10-year continuous cropping, all significantly higher than those under the control (1 071 and 385, respectively). Root activity of tomato seedlings firstly rose and then fell. At 3 days of cultivation, root activity of tomato seedlings under soil abstracts with over 250 mg·mL^-1 concentration of 1 year and 10 years continuous cropping were lower than that of CK. Antioxidant enzyme activity, MDA and proline contents were also significantly different from CK. Above all, some allelechemicals were secreted by okra roots, including the substances vestigital in the soil, which had negative effects on subsequent tomatoes. The substances were enriched with increasing years of continuous cropping, which caused more damage to succeeding tomato crops.

Effects of elevated CO₂ concentration on nutrients and secondary metabolites in Medicago sativa leaf under different damage degrees of pea aphid (Acyrthosiphon pisum, Hemiptera: Aphididae)

SUN Qian, ZHANG Tingwei, WEI Junyu, LYU Yuqing, LIU Changzhong

2019, 27(1): 92-99. doi: 10.13930/j.cnki.cjea.180411

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Due to massive exploitation and use of fossil fuel such as petroleum, coal and natural gas, atmospheric CO₂ concentration has been increasing, which not only accelerated global warming, but also affected the survival and distribution of animals and plants on the earth with far-reaching impacts on the ecosystem. This research was carried out to explore the effects of elevated CO₂ concentration and pest population density of Acyrthosiphon pisum on chemical substances in the leaves of Medicago sativa. The objective was assessed the effects of elevated CO₂ concentration and pea aphid density on the physiology and biochemistry of M. sativa. The nutrients and secondary metabolites in M. sativa leaves were determined by cultivating M. sativa seedlings attacked by 10-day old pea aphids of 10 head·plant^-1, 20 head·plant^-1, 30 head·plant^-1 and 0 head·plant^-1 (CK) for one week under three CO₂ concentrations[380 μL·L^-1 (CK), 550 μL·L^-1 and 750 μL·L^-1] in CO₂ gradient chamber. The results indicated that the contents of soluble protein, soluble carbohydrate and starch increased after aphid sucking of 30 head·plant^-1 with increasing CO₂ concentration. At 750 μL·L^-1 CO₂ concentration, they were respectively 11.62 times, 0.49 times and 0.24 times higher than those under CK, respectively. Also the contents of flavone, total polyphenols and simple phenols increased significantly. Furthermore, the contents of starch and simple phenols increased and then decreased with increasing degree of damage under the same CO₂ concentration. Comparatively, contents of soluble carbohydrate, total polyphenols and tannin were significant differences between aphid densities of 30 head·plant^-1 and 0 head·plant^-1, which increased by 1.66 times, 1.49 mg·g^-1 and 1.09 mg·g^-1 (P < 0.05) compared with those of CK under the highest level of CO₂ concentration. The results indicated that nitrogen fixing legume plants were more likely to adapt to increased CO₂ concentration and thereby enhanced self-induced resistance to insect pests.

Effect of straw return methods on maize straw decomposition and soil nutrients contents

TIAN Ping, JIANG Ying, SUN Yue, MA Ziqi, SUI Pengxiang, MEI Nan, QI Hua

2019, 27(1): 100-108. doi: 10.13930/j.cnki.cjea.180551

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By investigating the impacts of tillage and straw return methods on maize straw decomposition, a suitable approach of returning maize straw to soil was explored for straw utilization with high soil efficiency in the brown soil area of northeastern China. A two-year (2014-2015) field experiment including no-tillage with straw mulch (NTS), straw incorporation through rotary tillage (RTS) and straw incorporation through plow tillage (PTS) treatments was conducted in Shenyang, Liaoning Province. Nylon bags containing straw 2-5 cm long were buried in different depths of soil according to tillage depth of different treatments (0 cm for NTS, 15 cm for RTS and 25 cm for PTS) in the study, and the decomposition of straws and release rates of carbon (C), nitrogen (N), phosphorus (P) and potassium (K) by maize straw, along with the effects of straw return on nutrients contents of the topsoil were tested. The results showed that straw decomposition rates were high at the early phase and slowed down at the later phase under both RTS and PTS treatments, with the order of nutrients release rates in all treatments of K > P > C > N. The mean decomposition rates of straw in both years were 38.8%, 78.0% and 65.9% respectively for NTS, RTS and PTS treatments. Nutrients release rates of returned straws under NTS, RTS and PTS treatments were respectively 56.5%, 78.8% and 69.4% for C, 16.7%, 53.5% and 38.8% for N, 81.3%, 92.5% and 89.8% for P, and 92.0%, 99.4% and 98.9% for K. The tendency for straw decomposition and C and N release under NTS treatment fitted well with Logistic function, but those of RTS and PTS treatments fitted Michaelis-Menten function. Moreover, K and P nutrients release of all the three treatments changed according to the Michaelis-Menten functions. Straw return enhanced organic carbon and total nitrogen contents of the topsoil. Then total soil P content of RTS treatment was significantly higher than that of PTS (P < 0.05). However, there was no significant difference in total soil P content between RTS and NTS treatments, and in total soil K content for all the treatments. Based on comprehensive analysis from straw decomposition characteristics and fertility, straw incorporation through rotary tillage was the suitable approach for maize straw return in brown soil areas in Northeast China.

Characteristics and driving factors of acid-base buffer of typical tobac-co-planting soils in western Hunan Province

LI Yuanhuan, DENG Xiaohua, ZHANG Zhongwen, ZHOU Miliang, JIANG Zhimin, TIAN Feng, ZHANG Mingfa, SHI Nan

2019, 27(1): 109-118. doi: 10.13930/j.cnki.cjea.180643

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To determine the characteristics of pH buffer of soils cultivated with tobacco in the mountain regions that are under long-term fertilizer application, a total of 28 soil samples were collected in areas of typical flue-cured tobacco cultivation in mountain regions in western Hunan Province. The pH buffer characteristics of collected soils were analyzed using both titration curve and gray correlation methods. Then quantitative relationships and the driving factors of soil acid-base buffer characteristics were also investigated. The results showed that the range of pH buffer of soils cultivated with tobacco in western Hunan Province was 11.35-43.29 mmol·kg^-1 and the average was 17.26 mmol·kg^-1. Acid-base buffer of yellow brown soil (11.35-43.29 mmol·kg^-1) was significantly higher than that of yellow soil (11.79-20.70 mmol·kg^-1). While the sensitivity of yellow soil to acid was determined by the content of soil organic matter, that of yellow brown soil to acid was closely related to pH and organic matter content. Also while 78.57% of the samples were sensitive to both acid and base, soil type, organic matter contents, and clay content were positively correlated with pH buffer capacity. For yellow brown soil, pH buffer capacity was also positively correlated with pH and cation exchange capacity. However, it was negatively correlated with exchangeable acid and aluminum. The performances of pH buffer of two soil types were quite different. pH buffer capacity of yellow soil was mainly affected by soil organic matter content, cation exchange capacity, and clay content. Then pH buffer capacity of yellow brown soil was mainly affected by pH, cation exchange capacity, and organic matter content. For production, it was necessary to use chemical fertilizers properly, to add organic fertilizer, to adjust soil acidity and to take other measures to improve pH buffer capacity of soil cultivated with tobacco. This will create a good ecological environment for the production of high quality tobacco leaves.

Increase of fertilizer solution concentration and biomass mixing proportion can enhance water and nutrients distribution in wetted soils under moistube irrigation

LI Yilin, LIU Xiaogang, LIU Yanwei, DONGMU Hongdao, YANG Qiliang, SUI Long

2019, 27(1): 119-130. doi: 10.13930/j.cnki.cjea.180503

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Abstract:
Moistube irrigation is a new water-saving technology for continuous underground irrigation that can provide an effective carrier for agricultural fertigation technology. In order to investigate the mode of distribution of water and nutrients in wetted soils in moistube fertigation in vertical insert mode under different proportions of biomass mixture of soil, a series of indoor soil box infiltration simulation experiments were carried out using peanut shell power as mixed biomass. In the experiments, three fertilizer solution concentrations (F₀:pure water at 0 g·L^-1; F_L:low concentration at 0.2 g·L^-1; and F_H:high concentration at 0.4 g·L^-1) and four proportions of biomass mixture (B₀:no mixing at 0; B_L:low mixing at 1.5%; B_M:moderate mixing at 3.0%; and B_H:high mixing at 4.5%) were designed to study the distribution characteristics of soil water content, nitrate nitrogen, available phosphorus and available potassium in wetted soils under moistube fertigation in vertical insert mode. The results showed that the distribution areas of water and nutrients significantly expended after biomass mixture, but fertilizer solution concentration had no significant effect on the distribution areas of water and nutrients. Water and nutrients contents gradually decreased with increasing horizontal distance from moistube in wetted soils and the maximum water and nutrients contents occurred just next to the moistube. The distribution of soil water and nitrate nitrogen were more uniform, while available phosphorus and available potassium formed accumulation area within 0-10 cm in the horizontal distance from the moistube. Fertilizer solution concentration and mixing proportion of biomass significantly influenced the mean contents of water and nutrients in the wetted soils. Compared with F₀, mean soil water content and soil nutrients (nitrate nitrogen, available phosphorus and available potassium) contents increased with increasing fertilizer solution concentration respectively by 3.94%-14.09% and 124.92%-458.05%. Mean soil water content and soil nutrients contents increased with increasing proportion of biomass mixture respectively by 12.89%-33.32% and 28.37%-115.44%, compared with those of B₀. The distribution uniformity of soil water and nitrate nitrogen was higher, but that of available phosphorus and available potassium was lower in the wetted soils under moistube fertigation in vertical insert mode. The distribution uniformity coefficient of soil water and nitrate nitrogen increased with increasing fertilizer solution concentration and biomass mixing proportion, while that of available phosphorus and available potassium decreased in the wetted soils. The relationship between mean soil water and nutrients and horizontal distance from the moistube conformed to the fourth log-Logistic model in the wetted soils under moistube fertigation in vertical insert mode. In summary, mixing biomass with soil was improved water and nutrients movement in the wetted soils under moistube fertigation in vertical insert mode. Also increasing the concentration of fertilizer solution and proportion of soil biomass mixture significantly increased soil water and nutrients contents. This in turn increased the uniformity of soil water and nitrate nitrogen, and promoted the accumulation of available phosphorus and available potassium around moistube. The research results provided solid theoretical basis and practical reference for moistube fertigation technology.

Prediction of spatial distribution of soil organic matter based on improved OK models: A case study of Honghuatao Town in Yidu City

DUAN Lijun, GUO Long, ZHANG Haitao, JU Qinglan

2019, 27(1): 131-141. doi: 10.13930/j.cnki.cjea.180348

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Abstract:
Choosing a suitable prediction model to estimate soil organic matter (SOM) content is not only a prerequisite to improve the accuracy of spatial distribution simulation, but also the basis for monitoring dynamic changes in soil carbon pool and for guiding soil fertility input in farming. In order to achieve this, a research was set up to investigate the advantages of combined traditional Ordinary Kriging (OK) interpolation and Co-Kriging (COK) interpolation in constructing a new model that integrates Cooperative Correlation of auxiliary variables with OK model (CCOK). The following three aspects were thus discussed:1) whether the inclusion of auxiliary variables had an impact on SOM prediction result; 2) what were the differences in SOM prediction results caused by changes in the number of auxiliary information interpolations; and 3) how improved SOM prediction accuracy by cooperative correlation of auxiliary variables. To address these research questions, we collected 329 soil samples from a citrus plantation in Honghuatao Town located in the north Yidu City, Hubei Province. Through physical and chemical analysis, 14 soil properties were extracted. The correlation between SOM and other soil properties were discussed based on Pearson correlation coefficient (r) and available nitrogen was chosen as model auxiliary variable with the most significant correlation with SOM. With reference of OK (the control), we constructed modeling COK (COK₁), global COK (COK₂) and two improved OK models (CCOK₁ and CCOK₂). Among the models, COK₁ was a COK model which used modeling set auxiliary variables to participate in modeling. Based on COK₁, COK₂ changed the modeling set auxiliary variables to global auxiliary variables. CCOK₁ and CCOK₂ represented the OK interpolation models of two forms of functions constructed by the target variables and its auxiliary variables. Some of the results obtained were as follows:1) the range of the nugget/sill proportions of OK, CCOK₁ and CCOK₂ were 25%-75%, which belonged to medium spatial autocorrelation. However, the nugget/sill proportions of COK₁ and COK₂ were less than 25%, belonging to strong spatial autocorrelation. It then showed that the spatial variability of SOM as cross-variance function with auxiliary variables was more easily recognized by semi-variogram models. 2) The predicted SOM in the study area was within 7.38-29.03·kg^-1. Compared with OK interpolation, the strong spatial autocorrelation of COK₁ and COK₂ meant that the spatial distribution of SOM was even more fragmented. Furthermore, plots of CCOK₁ and CCOK₂ predictions were flaky, with digital mapping results of SOM with higher or lower values, which was more consistent with the actual distribution of land use in the study area. 3) The accuracies of COK₁ and OK were similar, but that of COK₂ was higher than the above two. Nevertheless, the correlation coefficients (r) of CCOK₁ and CCOK₂ increased from 0.10 to 0.70 and 0.69, with root mean square errors (RMSE) decreasing by 15.40% and 14.78%, respectively. Finally, the overall accuracy of SOM digital soil mapping was CCOK₁ ≈ CCOK₂ > COK₂ > COK₁ ≈ OK. This indicated that CCOK model minimized error between measured and predicted values in SOM prediction. Thus, the synergy of combined SOM estimation and auxiliary variables was a better correlation than the addition of only auxiliary variables or changing the amount of auxiliary variables. The improved OK model proposed in this study improved the maximum participation of auxiliary information, thereby providing a reliable reference for SOM prediction.

Carbon emission and ecological compensation of main functional areas in Sichuan Province based on LUCC

XU Jie, PAN Hongyi, HUANG Pei

2019, 27(1): 142-152. doi: 10.13930/j.cnki.cjea.180493

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Abstract:
Carbon emissions under land use/cover change (LUCC) reflect the disturbance degree of environment by human activities. Therefore, carbon budget and compensation research was of great significance to regional low-carbon economy and balanced development. Based on land use data for Sichuan Province in 2005 and 2015, this paper built a new local land use classification system and carbon emission model to quantitatively analyze carbon emission and carbon offset rate of land use in 183 counties in Sichuan Province. Taking into account regional differences at county level and breaking traditional administrative regional boundaries, the study based on the five main functional areas of Sichuan Province to measure ecological compensation standards with afforestation cost and carbon tax rate methods. The results showed that:1) during the study period, land use in each main functional area in Sichuan Province was consistent with the main functional area planning and was optimized according to the functional orientation. Cultivated lands in the key development area had absolute advantage, while the total amount and increase in construction land area was the largest. Otherwise, cultivated land holding capacity in the main agricultural production area remained the strongest. Woodland and grassland accounted for 70%-80% in the key ecological function areas. 2) During the study period, total carbon emission in each main functional area increased significantly, and the construction land was the main carbon source, and forest land was the main carbon sink. Total carbon emissions and increments in the key development area ranked first, with carbon sinks in the key ecological functional area accounting for 63% of Sichuan Province, although the ability to absorb carbon gradually weakened. 3) Carbon emission intensity of construction land of each main functional area was much greater than total carbon emission intensity. Total carbon emission intensity of each main functional area increased during the investigated period, but carbon emission intensity of construction land showed increased or decreased. Total carbon emission intensity of the key development area at national level was largest, while that of construction land was smallest. 4) The rate of carbon compensation in the ecological development areas was high, with economic development area having the reverse trend. The compensation coefficient of carbon absorption was highest for the restricted development area at national level (key ecological function area). 5) Carbon source area provided ecological compensation for carbon sink area based on the scope of ecological compensation. Ecological compensation standard for Ganzi Tibetan Autonomous Prefecture, which was a carbon sink area, was 5.82 billion to 20.56 billion Yuan. It indicated that carbon emission was correlated with functional location of each functional area. Ecological compensation standard generally decreased from Chengdu Plain to the surrounding areas, and ecological compensation standard of the restricted development areas were relatively low. On the basis of the ecological compensation standard for carbon emissions, a horizontal fiscal transfer payment policy was established as reference basis for energy conservation, emission reduction and balanced development of Sichuan Province.

Decoupling analysis on water resources utilization of planting industry and economic development in Shaanxi Province from the perspective of water footprint

ZHANG Wei, QIN Qiu

2019, 27(1): 153-162. doi: 10.13930/j.cnki.cjea.180447

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Abstract:
Shaanxi Province is located in a key area of the "One Belt One Road" promoted by China. The availability of agricultural water resources is bound to be further scarce due to accelerated economic transformation as a result of the "One Belt One Road" project. To therefore quantify water footprint of the crop industry and to determine the co-ordination between planting and economic development are critical for further clarification of the water use in planting and setting up relevant reference basis for water resources management in Shaanxi Province. Thus this paper incorporated the loss of water during distribution and irrigation of crop water footprint. By accounting for the value of water footprint of the crop industry in Shaanxi Province for the period 2005-2016, we analyzed the spatial and temporal differences in water consumption by various crops in Shaanxi Province, the utilization efficiency of green water and the pressure of water environment. Combined with the Tapio model, the change in relationship between economic growth of crop farming, water resource utilization and water environment was determined. The results showed that:1) water consumption by various crops was significantly different during the study period. The water footprint of vegetables and fruits were respectively 0.42 m³·kg^-1 and 0.51 m³·kg^-1, while that of tea was as high as 30.29 m³·kg^-1. However, there was an overall downward trend in water use. 2) The water consumption composition of planting industry in different areas was quite different, crop water consumption proportion in Guanzhong was 69.59%, grain and corn water consumption proportion in northern Shaanxi was 75.16% and that in southern Shaanxi was relative equilibrium among various corps. The water consumption composition was basically the same as water endowment and crop water footprint. 3) The use efficiency of green water footprint was relatively low. Also the pressure index of water environment was low in the south, high in the central and north. The average water environment pressure index for Xianyang was as high as 4.75 in 12 years, indicating serious water environment pressure. 4) The decoupling of economic growth of crop industry with water resource use and water environment pressure accounted respectively for 45.45% and 27.27% of total water use in the province. The research results showed that planting structure in Shaanxi Province was relatively reasonable and that green water footprint was hugely utilized. The efficiency and pressure of water environment still needed improvement. The relationship between economic growth of crop industry and water resources use was being gradually transformed from primary co-ordination of weak decoupling to quality co-ordination of strong decoupling. However, it still faced the change of industrial diversity, economic growth and environmental pressures.

2019 Vol. 27, No. 1