中国生态农业学报(中英文)

"Dual character" of rice-crayfish culture and strategies for its sustainable development

CAO Cougui, JIANG Yang, WANG Jinping, YUAN Pengli, CHEN Songwen

2017, 25(9): 1245-1253. doi: 10.13930/j.cnki.cjea.170739

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Abstract:
Rice-crayfish culture has been greatly developed in China in recent years due to its high comprehensive benefits. Especially, rice-crayfish culture has been rapidly developed in Hubei Province, where has a large area and proven technique of rice-crayfish culture, and developed the "Qianjiang Mode". In this paper, we introduced the characteristics and the development of rice-crayfish culture, and studied the production and ecological effects of rice-crayfish culture in Hubei Province by investigation, demonstration and long-term experiment. And the "dual character" of rice-crayfish culture was illuminated. The "dual character" of rice-crayfish culture was mainly reflected by the following phenomena. (1) Rice-crayfish culture stabilized food synergy, but favored crayfish over rice. Rice yield of rice-crayfish culture was increased by 4.63%-14.01% compared with conventional rice culture, and the rice quality was improved. But sometimes the rice yield was decreased due to the poor management for rice. (2) Rice-crayfish culture improved the soil fertility, but aggravated the soil gleization. The contents of readily oxidizable organic carbon (ROC), total N, total P and total K in soil of rice-crayfish field were higher than those of conventional rice field, but soil color was darker, structure was tighter, the gleization was obvious. (3) The rice-crayfish culture conserved water, but in some cases increased water consumption. The water use efficiency and water conserving capacity in field with high groundwater level were higher, but water consumption was increased by 50%-80% in field with low groundwater level. (4) The rice-crayfish culture decreased fertilizers and pesticides application, increased water nutrient con-centration, but also increased the risk of water eutrophication. The costs of fertilizers and pesticides were decreased by 79.5% and 50.0%, respectively. The total N, total P, nitrate-N and ammonia-N concentrations were higher in the surface water of rice-crayfish field. (5) The pests amounts were deceased, but some disease occurrence increased and biodiversity changed in rice-crayfish field. The lepidoptera pests were decreased, but the basal rot was heavier, and the biodiversity was decreased firstly, then increased by years in rice-crayfish culture. Finally, we made some suggestions for improving the rice-crayfish culture, such as adjusting managements to local conditions and decreasing blindness, standardizing development, optimizing pattern and regulating water and fertilizer utilization, and scientific control of disease, pests and weed. These suggestions may ensure the sustainable development of rice-crayfish culture.

Meta-analysis on farmland soil N₂O emissions under biochar application in China

LUO Xiaoqi, FENG Hao, LIU Jingjing, ZHANG Afeng

2017, 25(9): 1254-1265. doi: 10.13930/j.cnki.cjea.170298

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Abstract:
In this study, a Meta-analysis was conducted to make clear the effects of biochar application on soil N₂O emissions and the main controlling factors in China. Based on observation data from published papers in the public domain, the effects of biochar application on soil N₂O emissions were quantitatively analyzed under different climatic conditions, soil properties, field management practices and biochar properties. Then path analysis was used to determine the dominant factors influencing soil N₂O emissions. The results showed that biochar application significantly decreased soil N₂O emissions (P < 0.05) under annual mean precipitation more than 600 mm, and the reduction effect was strengthened with increasing annual mean precipitation. Also when annual mean sunshine hours was greater than 1 000 h, the N₂O emission-reduction effect of biochar application decreased in trend following an initial increase with increasing annual mean sunshine hours. With increasing soil pH above 6.5, soil N₂O emission reduction first increased and then decreased under biochar application. Biochar application significantly decreased soil N₂O emissions in loam soils (P < 0.05), whereas the effects in sandy and clay soils were not significant (P>0.05). Moreover, the reduction in soil N₂O emissions under film mulching was higher than that without film mulching. The effect of biochar on soil emission decreased with increasing nitrogen application rate, but increased with increasing specific surface area of biochar. When C:N ratio of biochar was 30-500, the effects of biochar application on soil N₂O emissions was significant at P < 0.05. When the amount of biochar was 20-160 t·hm^-2, soil N₂O emissions significantly decreased with increasing biochar application rate. Furthermore, significant differences in N₂O emissions were observed for different regions under biochar application. For example, there was a significant reduction in N₂O in South, East, Central and Northeast regions of China (P < 0.05), except Northwest China (P>0.05). Generally, N fertilizer input, biochar application amount, annual mean temperature and annual mean precipitation were the dominant factors affecting the N₂O emission-mitigation effects of biochar, which was controlled by the interactions among these factors. The study provided a reference base for the promotion of biochar technology in farming in China and emission reduction of soil N₂O.

Effect of nitrogen fertilizer level on bacterial community and N₂O emission in paddy soil

SONG Yana, LIN Yan, CHEN Ziqiang

2017, 25(9): 1266-1275. doi: 10.13930/j.cnki.cjea.170146

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Abstract:
Microbial community structures are relevant for the utilization of nitrogen (N) and the emission of nitrous oxide (N₂O) in paddy soils. Nitrification and denitrification are the main ways to produce N₂O in soils and nitrification bacteria and denitrifying bacteria respectively drive the processes of nitrification and denitrification. In this study, changes in bacterial communities and the abundance of nitrification bacteria or denitrifying bacteria under different nitrogen fertilizer levels[CK (no N fertilization), 1/3N (N application of 60 kg·hm^-2), 2/3N (N application of 120 kg·hm^-2) and N (N application of 180 kg·hm^-2] in paddy soils were analyzed respectively by high-throughput sequencing and real-time PCR. The analysis in abundance of nitrification bacteria or denitrifying bacteria was based on ammonia-oxidizing bacterial amoA gene and denitrifying bacterial nirS gene or qnoB gene or nosZ gene. The results showed that increase in application of nitrogen fertilizer enhanced Chao1 index and Shannon diversity index of bacterial communities and changed the composition of bacterial communities in paddy soil. The relative abundance of Nitrospirae and Acidobacteria increased with improvement of nitrogen fertilizers, while that of Methylosinus decreased with improvement of nitrogen fertilizers in paddy soils. There was greater impact of increased use of nitrogen fertilizer on the abundance of amoA gene in paddy soils. The abundance of amoA gene increased with increasing nitrogen application in the 0-5 cm or 10-20 cm depths of soil. The abundances of nirS gene, qnoB gene and nosZ gene in no-fertilizer soil (CK) were significantly lower than those in fertilizer soils (1/3N, 2/3N and N) (P < 0.05). There was no significant difference in the abundance of nirS gene among 1/3N, 2/3N and N treatments. However, there was an increasing tendency in the abundance of qnoB gene and nosZ gene with increasing application of nitrogen fertilizer in the 0-5 cm depth of soil. The abundance of nosZ gene in the 10-20 cm depth of soil under both 2/3N and N treatments were significantly higher than that in 1/3N treatment (P < 0.05). At the same time, the emission of N₂O under N treatment was significantly higher than that under 2/3N or 1/3N treatment (P < 0.05), and the latter two were also higher than that under CK (P < 0.05). Correlation analysis showed that the emission of N₂O was markedly correlated with the relative abundance of Nitrospirae in the 0-5 cm depth of soil and the abundance of amoA gene in the 10-20 cm depth of soil (P < 0.05, n=10). In summary, increasing nitrogen application improved the diversity of bacterial communities and the emission of N₂O in the studied paddy soils. Also there was a closer correlation between changes in abundance of nitrification bacteria and the emission of N₂O. The results suggested that the influence of nitrification bacteria on the emission of N₂O in the studied paddy soils was greater than that of denitrifying bacteria.

Dynamic simulation of leaf area index of tobacco based on nitrogen effect

SHAO Huifang, LIU Zhihong, CUI Dengke, MU Tong, HUANG Wuxing, XU Zicheng

2017, 25(9): 1276-1286. doi: 10.13930/j.cnki.cjea.170214

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Abstract:
This study was set up to clarify the dynamic characteristics of leaf area index of flue-cured tobacco under different nitrogen levels and the relationship with accumulated temperature. The leaf area index and dynamic characteristics of three flue-cured tobacco cultivars ('YU12', 'QIN96'and'YUN87') were measured under different nitrogen levels (0 kg·hm^-2, 30 kg·hm^-2, 60 kg·hm^-2 and 90 kg·hm^-2) to improve photosynthetic structure of flue-cured tobacco. Using the Curve Expert 1.40 software and the limit method, the normalized accumulated temperature model was established. The result indicated that:1) A unimodal curve between leaf area index and accumulated temperature was observed after transplanting of flue-cured tobacco, with a skewness less than 0. Leaf area index of flue-cured tobacco increased with increasing nitrogen level, and the peak value of leaf area index was in the order of'QIN96' > 'YUN97' > 'YU12' at the same nitrogen level. 2) The rational function model y=(a+bx)/(1+cx+dx²) yielded the best simulation result of leaf area index change with relative active accumulated temperature with high precision level (R²=0.980 7^**). The accuracy and precision of the normalized model were tested with data for 2015, and the simulation accuracy (k) was all above 0.958, the precision (R²) all above 0.95 and RMSE below 6.04%. 3) There were significant differences among some varieties and nitrogen levels, showing that variety interaction with nitrogen level mainly changed the model values of b, c and d. 4) The velocity of relative leaf area index change during the growing period showed trends in'N'curve, reflecting the actual variability of leaf area index. 5) Secondary indexes were more sensitive to different nitrogen levels. The mean leaf area index and maximum leaf area index increased with increasing nitrogen level. These characteristic indexes of leaf area index could be served as a reference base for the regulation of plant nitrogen of flue-cured tobacco population. The model provided theoretical basis and decision support for monitoring growth dynamics and photosynthetic characteristics of flue-cured tobacco population.

Effects of combined biochar and organic matter on soil fertility and maize growth

ZHANG Ying, LIU Xing, JIAO Ruifeng, LI Dongfang, REN Xiujuan, WU Dafu, CHEN Xiling

2017, 25(9): 1287-1297. doi: 10.13930/j.cnki.cjea.170115

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As a new functional material, biochar can increase soil carbon pool, improve soil quality and increase crop yield because of its particulate physical and chemical properties and is thus widely used in agriculture. However, studies on the comparison between biochar and traditional organic matter and their combined application are relatively rare. Thus a pot experiment was conducted to study the effect of the separate application of biochar, straw and chicken manure or their combined application on nutrient status, enzyme activity of soil and maize growth in fluvo-aquic loamy and sandy soils. Principal component analysis and simple correlation analysis were also used to synthetically evaluate the effects of different treatments and to determine the main driving factors of maize growth. All in all, a total of six treatments were conducted:control (CK), biochar (BC), wheat straw (WS), chicken manure (CM), wheat straw plus biochar (WS+BC) and chicken manure plus biochar (CM+BC). The results showed that all treatments increased maize biomass and height in sandy soil, the order of treatments in terms of maize growth was CM+BC=CM > WS+BC, BC > WS > CK, and manure could also increase maize biomass and height in fluvo-aquic loamy soil. Biochar and organic matter increased soil organic matter content, with the former particularly inducing a sharp increase. Different treatments showed different effects on soil nutrients and enzyme activities in both fluvo-aquic loamy and sandy soils. Chicken manure respectively increased soil available N by 22.08% and 26.67%, available P by 91.92% and 53.65%, and urease activity by 40.54% and 36.94% in fluvo-aquic loamy and sandy soils. Biochar respectively increased soil available P by 83.52% and 89.91%, soil available K by 79.38% and 127.02%, and soil catalase activity by 3.41% and 11.22% in the two soil types. Wheat straw respectively increased soil available K by 49.48% and 63.02%, soil β-glucoside enzyme activity by 51.86% and 59.09% in both fluvo-aquic loamy and sandy soils. Overall, combined application of biochar and manure or straw complemented each other and thereby improved more comprehensively soil fertility. Principal component analysis and correlation analysis suggested that maize biomass and height were highly significantly correlated with the second principal component score (PC2), which led to the positive changes in soil N and P pool. Therefore, among the three forms of organic matter, chicken manure influenced soil N and P contents and the related enzyme activities the most. Straw greatly influenced soil K and cellulose degradation-related enzymes, while biochar more evenly enhanced soil fertility which led to the most comprehensive gains in soil fertility. Straw or chicken manure, combined with biochar, more comprehensively improved soil fertility.

Effect of sulfur on nitrogen/sulfur uptake/distribution and yield of maize

CAO Dianyun, WANG Hongwei, XU Xiaoxu

2017, 25(9): 1298-1305. doi: 10.13930/j.cnki.cjea.170457

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Abstract:
For an in-depth understanding of the effects of sulfur on crop yield improvement, a field experiment was conducted to determine the effects of sulfur application on the absorption and distribution of both nitrogen and sulfur in the'Zhengdang-958'maize cultivar. To that end, a single factor randomized block design was set up in the experiment with five levels of sulfur-0 kg·hm^-2, 40 kg·hm^-2, 80 kg·hm^-2, 120 kg·hm^-2 and 160 kg·hm^-2. The results showed that the application of sulfur increased the yield of maize within the range of 7.0%-18.1%. When the application of sulfur was 80 kg·hm^-2, the yield of maize reached the highest level (12 978.30 kg·hm^-2). Also dry matter accumulation in maize increased significantly through the application of sulfur, with the peak value under 80 kg·hm^-2 at all growth stage except for the big trumpet stage. Dry matter accumulation in leaf, leaf sheath and grain weight were also the highest in 80 kg·hm^-2 sulfur treatment among different sulfur application levels at the mature stage. However, the dry matter accumulation in maize stem, bract and cob were the maximum under sulfur application level of 40 kg·hm^-2. Sulfur absorption and accumulation in maize was the maximum at each growth period under sulfur dose of 80 kg·hm^-2, which was significantly higher than that under sulfur dose of 0 kg·hm^-2. Sulfur content in maize leaf increased with increasing sulfur application level. The sulfur accumulation in corn stalk, bract and cob were highest under sulfur application level of 40 kg·hm^-2 whereas those in maize leaf sheath and grain were highest under sulfur application level of 80 kg·hm^-2. Nitrogen accumulation in maize was highest from jointing to the silking stage when sulfur dose was 120 kg·hm^-2. But at maize grain-filling and maturity stages, the nitrogen accumulation reached the peak points under 40 kg·hm^-2 and 80 kg·hm^-2 levels application, respectively. Sulfur partial productivity and use productivity decreased with increasing sulfur application level. When sulfur dose was 40 kg·hm^-2, sulfur partial productivity and use productivity reached the highest values. The agronomic efficiency of sulfur was largest under sulfur dose of 80 kg·hm^-2. Sulfur accumulation was positively correlated with nitrogen accumulation. In conclusion, fertilization using sulfur (at 40-120 kg·hm^-2) had high yield and fertilizer use efficiency. All in all, sulfur application was critical for nitrogen and sulfur uptake, distribution and use efficiency of maize. The overall effect was best under sulfur application level of 80 kg·hm^-2.

Effect of organic fertilizer on growth and yield components of castor under different planting densities

ZHAO Baoquan, WANG Maowen, DING Hairong, XING Jincheng, ZHU Xiaomei, LIU Chong, DONG Jing, HONG Lizhou

2017, 25(9): 1306-1316. doi: 10.13930/j.cnki.cjea.170279

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Abstract:
A 3-year field experiment was conducted from 2013 to 2015 during summer castor growing seasons at the coastland of Jiangsu Province. The aim of the experiment was to analyse the effects of organic fertilizer and planting densities on population growth and yield components of castor. The interactive test of three planting densities[18 000 plant·hm^-2 (D1), 15 000 plant·hm^-2 (D2) and 12 000 plant·hm^-2 (D3)] and three organic fertilizer application rates[12 000 kg·hm^-2 (O1), 6 000 kg·hm^-2 (O₂) and 0 kg·hm^-2 (O₃)] were conducted with a castor cultivar of'Zibi 8'as tested material. The investigated items included dry matter accumulation and distribution, leaf area index, chlorophyll content, spike characters and yield components. The results showed that the soil fertility could be improved significantly by using organic fertilizer for three years. With the application of organic fertilizer of 12 000 kg·hm^-2 under planting density of 15 000 plant·hm^-2 (D2O1), the contents of soil total nitrogen, available phosphorus, available potassium and organic matter significantly increased by 47.37%, 169.21%, 54.65% and 13.77% respectively compared with that without organic fertilizer treatment (D2O₃). Both leaf area index (LAI) and relative content of chlorophyll at the late growth stage was maintained at a high level under planting densities of 15 000 plant·hm^-2 and 12 000 plant·hm^-2 with the application of organic fertilizer. Total dry matter production at filling and ripening stages under medium planting density (15 000 plant·hm^-2) plus 12 000 kg·hm^-2 organic fertilizer (D2O1) significantly improved to almost similar level to that under high planting density of 18 000 plant·hm^-2 (D1O1). In addition, the distribution of dry matter in spike and crop growth rate (CGR) under planting density of 15 000 plant·hm^-2 both improved after anthesis with the application of organic fertilizer. The effective panicles per plant, grain number per plant and 100-grain weight increased with the increased rate of organic fertilizer application, which effectively compensated for low spike number at lower planting density. In this study, the crop yield under medium density (15 000 plant·hm^-2) with 12 000 kg·hm^-2 organic fertilizer (D2O1) was 3 943.77 kg·hm^-2, which was similar to that under high planting density (D1O1). It was concluded that suitable planting density in combination with the application of organic fertilizer effectively improved population growth and the reasonable distribution of dry matter, delayed leaf senescence, increased dry matter accumulation and grain yield at mature stage of caster.

Effects of water and fertilizer integration on growth, morphology, physiology and photosynthetic characteristics of flue-cured tobacco in the North China

HUO Zhaoguang, SUN Zhihao, XING Xuexia, WEI Xuanzhi, LI Xiaohui, LIU Chao, XUE Gang, XU Shixiao, YANG Tiezhao

2017, 25(9): 1317-1325. doi: 10.13930/j.cnki.cjea.170174

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Drought stress inhibits the growth and development of flue-cured tobacco in the North China, resulting in lower yield and quality. The purpose of this study was to determine the effects of integration of water and fertilizer on the growth and development, root morphology and physiology, and on photosynthetic characteristics of flue-cured tobacco in the North China. The differences in agronomic attributes, dry matter accumulation, root morphology and physiology, photosynthesis, chlorophyll fluorescence and economic characteristics of'Yunyan 87'flue-cured tobacco grown under water and fertilizer integration, and conventional irrigation and fertilization were investigated. The results showed that compared with conventional irrigation and fertilization, the growth and development of flue-cured tobacco was significantly promoted under water and fertilizer integration and with better agronomic attributes. The integration of water and fertilizer significantly increased dry matter accumulation in the belowground and aboveground parts of the plant. It also improved the indices for root morphology and physiology in terms of root volume, total root absorption area, root active absorption area, root specific surface area, root activity and ATPase activity. All these attributes were significantly higher than those under conventional irrigation and fertilization. The integration of water and fertilizer also reduced root to shoot ratio (P < 0.05). Meanwhile, net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), water use efficiency (WUE), PSⅡ maximal photochemical efficiency (F_v/F_m), PSⅡ actual photochemical efficiency (φ_PSⅡ) and photochemical quenching coefficient (q_P) all significantly increased under the integration of water and fertilizer (P < 0.05). On the contrary, both transpiration rate (T_r) and non-photochemical quenching coefficient (NPQ) significantly decreased under the integration of water and fertilizer (P < 0.05). Furthermore, the economic characteristics were significantly higher under the integration of water and fertilizer than those under conventional irrigation and fertilization (P < 0.05). In conclusion, the results indicated that the integration of water and fertilizer supported good root morphology and significantly improved root physiology activity, photosynthesis and light energy utilization efficiency. This stimulated the growth and development of flue-cured tobacco, resulting in higher economic characteristics.

Effects of ethephon and kinetin on lodging-resistance and yield of maize

LIU Wenbin, FENG Naijie, ZHANG Panpan, LI Dong, ZHANG Hongpeng, HE Tianming, ZHAO Jingjing, XU Yanhui, WANG Chang

2017, 25(9): 1326-1334. doi: 10.13930/j.cnki.cjea.170083

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Lodging is one of the major factors affecting yield of maize. To determine the effect of plant growth regulator application dates on lodging-resistance and yield of maize, the foliage of'Demeiya-1'and'Demeiya-2'were sprayed with 400 mg·L^-1 ethephon (ETH), 10 mg·L^-1 kinetin (KT) and fresh water (CK) at the 5-, 7-and 9-leaf stages, respectively. Then stem morphology, mechanical indicators, chemical properties, lodging rates at filling stage and grain yield of maize were determined. The results showed that compared with CK, KT treatment at 5-leaf stage increased internode diameter by 21.11% and internode density by 13.23% in'Demeiya-1'maize variety. Also ETH treatment at 7-leaf stage reduced the total length of basal internode by 14.41%, but then increased internode diameter by 10.70% and internode density by 15.46% in'Demeiya-2'maize variety. ETH treatment at 7-leaf stage increased the break strength of internode by 26.04% and 16.77%, and internode penetration strength by 22.77% and 14.62% respectively in'Demeiya-1'and'Demeiya-2'maize varieties. The contents of hemicellulose, cellulose and lignin in internode of'Demeiya-2'increased by 25.49% under ETH treatment at 9-leaf stage. The effect of ETH on mechanics of maize stalks regulation were better than that of KT, although the two plant growth regulators all reduced lodging rate of both maize cultivars. There was a highly significant positive correlation between internode diameter and break strength (r=0.905^**), but significant or extremely significant negative correlation was noted between lodging rate and chemical compositions contents or internode diameter of internode. KT application at 9-leaf stage significantly increased grain yield of'Demeiya-1'(22.24%) and'Demeiya-2'(19.98%), while ETH treatment had no significant effects on maize yield. Based on the results therefore, KT treatment at 9-leaf stage significantly increased maize yield, but lodging-resistance under ETH treatment at 7-leaf stage was better than that under KT.

Identification method of high temperature resistance of hybrid rice based on flowering rate

XU Fuxian, ZHOU Xingbing, JIANG Peng, ZHANG Lin, XIONG Hong, GUO Xiaoyi, ZHU Yongchuan, LIU Mao

2017, 25(9): 1335-1344. doi: 10.13930/j.cnki.cjea.170156

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Using cultivars with high temperature resistance is an effectively approach to reduce yield loss induced by extreme high temperature. The objective of this study was to improve the identification method for high temperature resistance of hybrid rice varieties in both pot and field experiments. To that end, a pot experiment was conducted in an intelligent artificial climate chamber to determine the effects of extreme high temperature (38℃) on percentage grain filling at grain-filling stage in 2013 and 2014. Four cultivars were planted and exposed to extreme high temperature for 5 hours at 5.0 hours before and during flowering stage, and 1.0 hour, 1.5 hours and 2 hours after flowering stage. Also concurrently, hybrid rice cultivars were grown under normal background conditions (daily maximum temperature of panicle layer of approximately 31.2-32.8℃) as control (CK). A field experiment was conducted using 40 hybrid rice cultivars to study the relationship between high temperature resistance and flowering rate of hybrid rice at different times of the days based on 5 sowing dates (March 5, March 25, April 20, May 4 and May 24) in 2015-2016. In each year, 20 cultivars with same heading date were selected from 5 sowing dates to observe flowering rate at different times of the day. The results showed a significantly positive linear correlation between high temperature resistance index and flowering rate of hybrid rice before 11:30 AM under high temperature condition or before 12:00 noon under normal temperature condition. The increase in seed setting rate of high temperature resistant variety under high temperature condition was indirectly related with high temperature resistance index, while its' seed setting rate under high temperature condition was directly related with high temperature resistance index. Flowering of hybrid rice occurred earlier under high temperature condition, the cultivar flowering was also earlier under normal temperature condition. Flowering of hybrid rice was mainly concentrated around 9:30 AM to 12:30 PM. However, flowering rate differed with cultivar at different times of the day. Seed setting rate was not significantly affected by high temperature after 2 hours of flowering. When panicle layer temperature was 34℃ and 35℃, and their frequency reached 80% at 13:30 PM and at 15:30 PM, respectively, choosing cultivars that flowered 2 hours before high temperature (daily maximum temperature greater than 34℃ or at about 35℃) could effectively resist high temperature injury. Regression equation was established based on flowering rate before 11:30 AM under high temperature and before 12:00 noon under normal temperature condition and seed setting rate under high temperature condition. The equation provided a new identification method of high temperature resistance of hybrid rice cultivars at flowering stage at a percent accuracy (estimated value/measured value) of up to 92.29%-102.73%.

Flavonoid is associated with salt stress tolerance in Atriplex centralasiatica seedlings

LI Shuang, SUN Liangliang, BAI Lili, WANG Wenying, WAN Jinpeng, LIU Xiaojing, MA Jinhu, XU Jin

2017, 25(9): 1345-1350. doi: 10.13930/j.cnki.cjea.170079

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Atriplex centralasiatica is a typical halophyte that widely grows in saline areas of China. In earlier studies, we found that salt stress markedly induced the accumulation of flavonoid in the roots of A. centralasiatica seedlings. By integrating the physiological and biochemical analyses in this study, the physiological mechanisms of salt-induced flavonoid accumulation in the roots of A. centralasiatica seedlings were investigated by supplementing with KNO₃ (25 and 35 mmol·L^-1) and exogenous quercetin (100 nmol·L^-1 quercetin) in different salinity-treated seedlings (50, 100, 250, 500 and 600 mmol·L^-1 NaCl). Our results indicated that supplementation of exogenous quercetin markedly suppressed primary root (PR) growth and the accumulation of both H₂O₂ and MDA in roots, whereas it markedly increased soluble sugar levels in seedlings. This indicated that exogenous flavonoid-quercetin affected root system architecture by suppressing PR growth and improved salt tolerance by reducing oxidative damage in A. centralasiatica seedlings. Salt stress also induced the accumulation of nitrate (NO₃^-) in A. centralasiatica seedlings. We found that treatment with 25 and 35 mmol·L^-1 KNO₃ markedly induced the accumulation of flavonoid in root tips of A. centralasiatica seedlings. All in all, the results indicated that nitrate modulated salt tolerance in A. centralasiatica seedlings by flavonoid pathway. This knowledge was helpful for further elucidating the physiological and molecular mechanisms of salt tolerance in A. centralasiatica. It also provided further insights into novel strategies for breeding and cultivating salt-tolerant crops and improved saline-alkali soils using modern biotechnology and agricultural measure.

Using spectral transformation processes to estimate chlorophyll content of winter wheat under low temperature stress

ZHANG Xueru, FENG Meichen, YANG Wude, WANG Chao, GUO Xiaoli, SHI Chaochao

2017, 25(9): 1351-1359. doi: 10.13930/j.cnki.cjea.170134

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Abstract:
Chlorophyll content is a vital index of photosynthetic capacity and crop growth status. In recent years, freeze injury had become a main meteorological disaster at jointing stage of winter wheat in the northern region of China. Although global climate had been warming since the 1980s, freeze injury had not weakened. Climate warming had led to a decline in the proportion of wheat varieties planted in winter and to a rise in the proportion of the varieties planted in spring. With increasing warm autumn years, the issue of wheat overgrowth has worsened, decreasing the ability of wheat to resist cold. Climate change has not been stable and extreme weather events have increased, implying that there was still the risk of freeze injury of wheat. Shanxi Province suffered freeze injury and the maximum area affected by freeze injury has been estimated at 0.26 million hectares. This had a severe impact on the growth and development of wheat, and ultimately affected the yield of wheat. The rapid and accurate estimation of chlorophyll content of winter wheat is meaningful in resisting the occurrence of freeze injury. However, the routine methods of measuring chlorophyll content are complex and time-consuming. Therefore, developing a rapid and non-destructive chlorophyll content diagnosis technology can be an effective way to monitor winter wheat freeze injury. Here, two varieties of winter wheat were treated under -6℃ temperature stress for 4, 8 and 12 hours at jointing stage. Moreover, canopy spectra were collected and the raw spectrum transformed with respect to 15 transformation methods and then the spectral transformation processes of chlorophyll content of winter wheat were analyzed in the PLSR model. The aim was to select the optimal spectral transformation of chlorophyll content in winter wheat under low temperature stress, and provide theoretical basis for monitoring freeze injury of winter wheat. The results showed that the chlorophyll content of two winter wheat varieties declined with increasing time of low-temperature stress. With increasing number of days after freeze, the differences between low temperature and control treatments decreased gradually. Moreover, the near-infrared region reflectance increased greatly with strengthening low-temperature stress and the visible region had no significant difference in short-term stress after 5 days. While the yellow and red bands increased, the near-infrared region decreased in differences after 10, 20 and 35 days of stress. Compared with the raw spectrum, the transformation methods under differential treatments (e.g., reciprocal, logarithm, power, and square root transformation methods) failed to improve the relevance of chlorophyll content and therefore the overall performance of model was poor. Other differential transformation processes of chlorophyll content diagnosis models had higher precision than raw spectral analysis, except for T₆[(lgR)', R is the spectral reflectance]. Moreover, the second-order differential for raw spectrum (T₁₅, R") had a higher accuracy (R_C²=0.930, RMSE_C=0.340; R_V²=0.753) respectively for the calibrated and validated models after comprehensive evaluation of predicted performance and complexity level of different models. It showed that the second-order differential for raw spectrum (T₁₅, R") was the most plausible transformation method of spectral reflectance for evaluating chlorophyll content of winter wheat under low temperature stress.

Evaluation of agro-ecosystem services and analysis of irrigation benefit in the North China Plain

ZHOU Shumei, WU Jing, WANG Guozhen

2017, 25(9): 1360-1370. doi: 10.13930/j.cnki.cjea.170203

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Abstract:
Agro-ecosystem has become a hot research area in the field of ecology in recent years. One of the most important issues of agro-ecosystems is the strongly disturbance they have suffered from human activities. Agro-ecosystems not only provide critical services for human existence such as agricultural products, but could also have negative impacts on ecological environment which together comprise the negative services of agro-ecosystems. It is known that farmland irrigation is the main mode of groundwater depletion in the North China Plain. Although grain yields can be increased greatly under groundwater irrigation, over-exploitation of groundwater can lead to environmental problems including lowered underground water level. Therefore, it is essential to exactly measure the contribution of irrigation to agro-ecosystem production and to comprehensively evaluate the sustainability of the development of agro-ecosystems in the North China Plain. Based on the Millennium Ecosystem Assessment (MEA) framework developed by the United Nations Environment Programme and taking the typically high-yield farmlands in Luancheng District of Hebei Province in the North China Plain as the study area, we used emergy theory to analyze agro-ecosystem inputs. The study also analyzed both the positive and negative services of the agro-ecosystems in the three categories of service provision, service regulation and service support using statistical input/output data of the agro-ecosystems in Luancheng for the period from 1984 to 2008. Furthermore, irrigation efficiency was calculated by the sharing coefficient method and the development sustainability of agro-ecosystems was evaluated by the calculation and analysis of a series of emergy indicators. The results showed that annual emergy input of the agro-ecosystems in Luancheng was 1.00×10¹² sej·m^-2, over 90% of which were non-renewable industrial auxiliary emergy (6.81×10¹¹ sej·m^-2) and non-renewable environmental resource emergy (groundwater irrigation of 2.57×10¹¹ sej·m^-2). This indicated that agro-ecosystems consumed a huge portion of non-renewable resources. For agro-ecosystem output, the positive service (75.60% of the total output) was greater than the negative service (24.40% of the total output). While service provision (agricultural product supply, 1.07×10¹² sej·m^-2) was the main positive service (1.82×10¹² sej·m^-2), regulation service (greenhouse gas emission of 5.31×10¹¹ sej·m^-2) accounted for most of the negative service (5.87×10¹¹ sej·m^-2). The sharing coefficient of irrigation benefit of the agro-ecosystems was calculated as the lower value of 0.32, and the net irrigation benefit was determined to be 3.94×10¹¹ sej·m^-2, taking into consideration the negative services of the agro-ecosystems. The values of emergy sustainability index, emergy sustainability index of ecosystem service and emergy sustainability index of net ecosystem service in the study area were 0.10, 0.18 and 0.12, respectively. All the above three emergy sustainability indexes were far less than 1, suggesting that the agro-ecosystems of Luancheng largely depended on consumable resources. Therefore, a series of countermeasures were needed to be taken, including the conservation of groundwater, the promotion of alternative fertilizers and the development of low toxicity pesticides, the implementation of national policy and legal tools. These countermeasures ensured low-energy consumption and high-yield development in agriculture towards the realization of sustainable development of agro-ecosystems in the North China Plain.

Review of methodology and application of agricultural eco-efficiency

NIE Wan, YU Fawen

2017, 25(9): 1371-1380. doi: 10.13930/j.cnki.cjea.170163

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Abstract:
Agricultural ecological efficiency analysis is vital in evaluating sustainable development of agriculture. It can be used to accurately assess the real value of agricultural ecosystem for the realization of efficient use of agricultural resources and for the alleviation of endogenous pollution caused by agricultural waste. As a result, it can also be used to solve problems concerning the degradation of agricultural ecosystems and the reduction in environmental pollution, and thereby laying a solid foundation for sustainable agricultural development. After a systematic review of the existing literatures on agricultural ecological efficiency, it was found that the three prominent problems which needed thorough research were:1) the precise definition of agricultural ecological efficiency and consistent evaluation method of agricultural ecological efficiency. 2) A thorough research on the macro-factors with significant impact on agricultural ecological efficiency and detailed analysis of agricultural ecological efficiency at national scale. 3) Extensive researches on important issues such as ecological capital, ecological agriculture and ecological agriculture policy. Thus in order to promote sustainable development of agriculture in China, the following aspects were needed in future research:1) improvement of the method of evaluation of agricultural ecological efficiency, 2) augmenting factors in the research of agricultural ecological efficiency, and 3) promotion of the application of agricultural ecological efficiency in areas such as ecological capital production, ecological agriculture production and ecological agriculture policy.

Assessment of agricultural carbon emission performance and stochastic con-vergence in China using SBM-Undesirable model and panel unit root test

WU Haoyue, HE Yanqiu, CHEN Rou

2017, 25(9): 1381-1391. doi: 10.13930/j.cnki.cjea.170147

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Abstract:
On overall scale and industrial perspective, researches on the evaluation of carbon emissions and the test of convergence in China have matured. However, the study has remained relatively weak in agricultural carbon emissions. To complement not only existing research but also for better understanding of the carbon emissions, performance and convergence in different regions, the paper used SBM-Undesirable model to assess the performance of agricultural carbon emissions based on the estimation of agricultural carbon emissions in 30 provinces in 2000-2014. Then three panel unit root tests were selected to determine stochastic convergence test for the investigated districts. The main conclusions were as follows:1) for the period 2000-2014, the overall trend in national agricultural carbon emissions increased, but the quantities of the emissions in different regions were significantly different. The mean agricultural carbon emission in the middle region was much larger than that in the whole nation, the eastern region and western region. The gaps in agricultural carbon emissions between the middle region and the whole nation, the eastern and western region were 3.357 4×10⁶ t, 3.965 0×10⁶ t and 5.904 7×10⁶ t respectively in 2000, whereas this gaps widened to 5.244 8×10⁶ t, 7.351 2×10⁶ t and 7.681 0×10⁶ t in 2014, corresponding respectively to growth rates of 56.2%, 85.4% and 30.0%. 2) The performance of agricultural carbon emissions in different regions turned out to differ apparently from distinct to district. A line graph of the average performance suggested that the performance was better for the eastern region, which was stable at 0.8 for 15 years. On the contrary, the average performance was relatively low for the west and middle regions, which was for most of the time within 0.3-0.5. The performance improved for the western region. However, the trend for the middle region was apparently the reverse. 3) In terms of convergence test of quantity, the examination of simulated convergence confirmed that stochastic convergence occurred only for the eastern region. There was no sign that stochastic convergence existed for the whole country, western region or even middle region. In the test of performance, there was no stochastic convergence for the whole country, while three regions exhibited relatively obviousness in the trend in club convergence. The results suggested that neither the quantity nor the performance of the whole country was automatically reducible to steady-state level. Thus it was necessary to make effective policy intervention to narrow the gap among the regions. Finally, this paper provided a further data-driven reference base for developing reasonable policies for the reductions of regional and national carbon emissions.

Assessment of farmer willingness to exit rural homestead based on farmer land property rights:An empirical analysis of Songjiang and Jinshan Districts in Shanghai

DENG Mei'e, ZHANG Anlu, CHEN Hongbing

2017, 25(9): 1392-1402. doi: 10.13930/j.cnki.cjea.161191

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Abstract:
The management and circulation policy of rural homestead are not only a big concern to the interests of farmers, but also a vital issue related to rural social stability and national economic development. Under the current policy concerning the integration of urban and rural regions and the most practical concern of the vast majority of farmers is whether they can truly enjoy the right of transfer of their homesteads. The local homestead exiting pilot program for saving construction land space was designed to enhance land use efficiency, but still could infringe on land ownership of farmers. From the perspective of household property right function, this paper analyzed the farmers' willingness of homestead withdrawals. By using relevant survey data on Songjiang District, Jinshan District of Shanghai, we established a regression model of Logistic with 29 indicators as based variables, and quantitatively analyzed farmers' willingness to exit homestead under the condition that farmers enjoyed collective land property rights. The results showed that:1) farmers clearly understood their homestead rights with a strong will to exit. Farmers were concerned about whether their expectations and perceived welfare of homestead exiting could be met. Farmers had strong will to use their homesteads for commercial development, which could lead to better economic compensation. 2) The premise for active voluntary homestead exiting was that farmers enjoyed main residential land use rights, security and property rights, had a very clear understanding of homestead rights, and had strong protection consciousness of self-interests so long farmer right/interest safeguards were not damaged. 3) In Shanghai and other eco-nomically developed areas, farmers had a clear understanding of homestead ownership, functions and powers and had higher willingness to quit if there were effective guarantees. Therefore, in the practice of farmer homestead exiting, it was important to explore a systemic establishment where farmer homestead rights were more complete with well-protected reasonable expectations and compensa-tion standards of homestead exiting. Such a systemic establishment could help guide the orderly exit of farmer homesteads.

2017 Vol. 25, No. 9