中国生态农业学报(中英文)

Temporal variation of atmospheric wet/dry reactive nitrogen deposition in Taiyuan rainfed farming area of Shanxi Province

LIU Ping, LIU Xuejun, LIU Enke, HAN Yanlong, LI Lijun, BAI Guangjie, XU Wen, LYU Wei, ZHANG Qiang

2017, 25(5): 625-633. doi: 10.13930/j.cnki.cjea.161024

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Abstract:
Nitrogen (N) deposition has a series of negative effects on ecosystem, therefore the atmospheric reactive N (Nr) pollution and deposition induced by excessive anthropogenic Nr have become a global environmental concern. Until recent years, researches on Nr deposition and precipitation were conducted at different scales, but still there are few continuous monitoring data about N deposition in rainfed farming areas. Here, the temporal variation of atmospheric wet and dry N deposition was quantified using the DELTA system, passive samplers and rain gauge at Hecun Village (which is Yangqu County, Taiyuan City, Shanxi Province) in a four-year period spanning from April 2011 to March 2015. The results showed the average deposition rates of NH₃, HNO₃, NO₂, particle form of NO₃^- (pNO₃^-) and particle fore of NH₄⁺ (pNH₄⁺) in the four-year period were 4.50 kg (N)·hm^-2·a^-1, 3.54 kg (N)·hm^-2·a^-1, 2.56 kg (N)·hm^-2·a^-1, 1.62 kg (N)·hm^-2·a^-1 and 2.75 kg (N)·hm^-2·a^-1, respectively. This led to total dry deposition value of 12.38-18.95 kg (N)·hm^-2·a^-1, with N dry deposition flux being the highest in 2011, and the lowest in 2014. From April 2011 to March 2015, there was a positive linear correlation between monthly dry N deposition and ammonia deposition (with a correlation coefficient range of 0.809 8-0.937 1), indicating that ammonia had a significant influence on N deposition of the study area. Total wet N precipitation range was 11.67-41.31 kg (N)·hm^-2·a-1 in the region and the average concentrations of NO₃^--N and NH₄⁺-N in rainfall were 3.20 mg (N)·L^-1 and 2.43 mg (N)·L^-1, respectively. There were considerable differences in annual wet N deposition fluxes in the four-year period, of which it was the highest in 2012 and the lowest in 2014. Moreover, wet N deposition accounted for over 50% of total N deposition. Furthermore, there was a positive linear correlation between NO₃^--N and NH₄⁺-N concentrations in rainwater in the four-year period, and there was also a positive linear correlation between NO₃^--N concentration and rainfall and then a quadratic correlation was also observed between NH₄⁺-N concentration and rainfall. This indicated that rainfall had a significant impact on wet depositions of NO₃^--N and NH₄⁺-N. Such high deposition rates of Nr in Taiyuan showed a severe Nr pollution from anthropogenic sources and a significant atmospheric N input in croplands. Overall, there were bigger differences in annual wet N deposition than annual dry N deposition for the investigated four-year period in Taiyuan area. Although tested in dry land, the rate of dry deposition was lower than that of wet precipitation. This study was important for N management referring to Nr deposition in farmlands and for monitoring N cycle in the farmland ecosystem.

Simulation of maize evapotranspiration at different growth stages using revised dual-layered model in arid Northwest China

WU Lin, MIN Leilei, SHEN Yanjun, ZHOU Xiaoxu, LIU Fenggui

2017, 25(5): 634-646. doi: 10.13930/j.cnki.cjea.160839

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Abstract:
Evapotranspiration (ET) is composed of two separate processes-water loss to the atmosphere from soil surface by evaporation (E) and water loss to the atmosphere from plant canopy via transpiration (T). ET plays a key role in energy and water balance in agricultural system and is also a critical process in terrestrial hydrological cycle. Accurate estimation of ET is significant for improving water use efficiency and optimizing regional water use, particularly in arid and semi-arid regions. Although ET models have been an important tool in understanding the regulation of ET in ecological, agricultural and environmental sciences, the accuracy of the models is limited by aerodynamic and canopy resistance. Numerous models have been developed to integrate aerodynamic and canopy resistances[e.g., Penman-Monteith (P-M) model] in simulating the processes of response of ET, but many studies have suggested that the P-M model could produce large errors under partial or sparse canopy conditions because it treated plant canopy and soil surface as a single entity. Next, the dual-layered Shuttleworth-Wallace (S-W) model was developed to estimate ET under different conditions. In this model, the crop ET is divided into two components-latent heat flux from crop and that from soil. It has been tested by various surface conditions and widely used because of its good performance. In this study (which used maize data of three eddy covariance observations for the period from May through September 2012 in Heihe River Basin, an arid area in Northwestern China), two canopy resistance models coupled for maize. Two S-W models were coupled with canopy resistance models of maize taking or non-taking into account the effect of atmospheric CO₂. Then the whole maize growth period was divided into three stages, early, middle and late growth stages. Then maize ET on half hour scale was simulated using the two S-W models. The performances of the two S-W models were validated for three different growth stages using eddy covariance field-measured data. The results showed that simulated maize ET by the S-W model (which took into account the effect of atmospheric CO₂ at every growth stage of three different places) best agreed with field-measured eddy covariance data. Sensitivity analysis of the revised S-W model (taking into account the effect of atmospheric CO₂) showed that maize ET was more sensitive to canopy resistance (r_s^c) and aerodynamic resistance from canopy to reference surface height (r_a^a) at different growth stages. Therefore, it is very necessary to determine resistance parameters at different growth stages taking into account the effect of atmospheric CO₂ when calculating maize ET using the revised S-W model.

Response of wheat yield to light distribution in intercropped Paulownia fortuneii shelterbelt and wheat

ZHAO Yang, QIAO Jie, WANG Weiwei, WANG Baoping, ZHOU Haijiang, CUI Lingjun, DUAN Wei, SU Lingyan

2017, 25(5): 647-655. doi: 10.13930/j.cnki.cjea.160887

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Abstract:
Paulownia fortuneii-wheat intercropping system is one of the most important agro-forestry ecosystems in Yellow-Huai-Hai River Flooding Plain in China. In this paper, a P. fortuneii shelterbelt intercropped with wheat was studied in order to determine light distribution and its impact on wheat yield. A total of 24 observation points with different differences to P. fortuneii shelterbelt were set to monitor photosynthetically active radiation (PAR) and 72 quadrats investigated to measure wheat yield, 1000-grain weight and grains per unit area for the period 2013-2015. Correlations between PAR at 3 key stages (including flowering stage, grain-filling stage and whole growth stage) and wheat yield, 1000-grain weight and grains per unit area were then analyzed. The results suggested that PAR and transmittance increased along with increasing distance from Paulownia shelterbelt and there were significant changes within 10 m (approximately 1-fold tree stem height) in the Paulownia shelterbelt. PAR and transmittance changed slightly above the distance of 10 m apart. The transmittance at 2 m apart from the south of the shelterbelt at grain-filling stage was smallest among all the observation points at 3 growth stages. The correlations were significant between wheat yield and PAR for whole growth period (r=0.918, P=0.000), the number of grains and PAR at flowering stage (r=0.926, P=0.000), the 1000-grain weight and PAR at grain-filling stage (r=0.922, P=0.000). The number of grains per unit area and 1000-grain weight were directly affected by shelterbelt overshadow both at flowering stage and grain-filling stage. The spatial difference in wheat yield in the intercropping system was explained by the difference in number of grains per unit area. The linear regression equation for wheat yield (y) and PAR (x) was y=0.121 3 x+95.117 (R²=0.842). The K-W rank test (P=0.609) at equation precision of 91.8% showed no significant difference between predicted yield and actual yield. The equation (in combination with observed PAR) was suitable for predicting wheat yield in the intercropping system. This study provided theoretical basis for establishing predictive model of ecosystem productivity and for designing optimal structure of Paulownia-wheat intercropping system.

Comprehensive evaluation of ecological risk of land during 1990-2012 in Yulin City

REN Zhiyuan, SUN Yijie, WU Linxiao

2017, 25(5): 656-664. doi: 10.13930/j.cnki.cjea.160843

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Abstract:
Land use/cover change is a determinant factor in the analysis of ecosystem services for regional ecological security and maintenance. Ecological risks of land serves as a vital index in measuring sustainable utilization of land resources. The research area used in this study was Yulin City, a city in northern Shaanxi Province located in the Loess Plateau and Maowusu Desert border where the climate is arid and the land use structure is irrational. This region is one of the areas with the most severe water and soil erosion on the Loess Plateau, with ecologically-fragile environment, damage susceptibility and recovery difficulty. Thus based on the natural geographical conditions, development history of the city, basic land system characteristics and removed single factor evaluation uncertainty, this study established an evaluation index system of various sources risk in Yulin City. Percent precipitation anomaly index was used as indicator for the risk of drought, the risk of land use structure as the indicator for the effect of human activity on the ecological system, and wind/water erosion as the indicators of soil erosion. Then the four evaluation indicators were used to construct a comprehensive evaluation model for the qualitative and quantitative evaluation and analysis of the factors affecting ecological risk of land in Yulin City for the period 1990-2010. The main conclusions of the study were as follows: (1) the distribution of precipitation was uneven, with percent precipitation anomaly index initially decreasing and later increasing in the period from 1990 to 2012 for Yulin City. The area with lower value of the index mainly covered the eastern part of the city. And the index increased from the south to the north. (2) There were large and significant changes in the differences in regional risks of land use structure. The land use structure risk first increased and then decreased in the course of the investigated 21-year period. (3) More severe soil water erosion occurred mainly in the eastern and the southern regions of the study area (driven mainly by topographic factors) with an initial mean increase and then a decrease over the 1990-2012 period. (4) There was more severe wind erosion mainly in the northern region, with Yuyang District having the largest erosion and Suide and Mizhi Counties the smallest erosion, and with a decreasing trend in mean erosion for the investigated period. (5) The trend in ecological risk of land was decreased, and significant differences in ecological risk of land were observed among counties. The area of Yulin City with severe ecological risk in 1990 was mainly in the northwest, area with high ecological risk in 2001 was mainly in the central region and west of Yulin City (e.g., Dingbian County), area with moderate ecological risk was mainly in the southeast. The ecological security status in the study area was improved overall, although the situation remained grim. This research put forth a theoretical proposal for optimizing the allocation of land resources and protecting the ecological environment in order to realize a harmonious development of regional economy and ecology.

Surpluses and deficits of cultivated land protection externalities in grain-production regions: A case study of Henan Province

NIU Haipeng, XIAO Dongyang

2017, 25(5): 665-676. doi: 10.13930/j.cnki.cjea.160911

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The concept model of multi-level function boundary of cultivated land protection externalities in a typical zone was advanced in this paper. And the measurement models of surpluses and deficits of a typical zone with cultivated land protection externalities were delineated at provincial and national boundaries to measure the surpluses and deficits of cultivated land protection externalities in grain-production dominated zones of 18 cities in Henan Province. The aim of the study was to measure and analysis surpluses and deficits of cultivated land protection externalities under different boundaries to provide reference for setting standards of inter-regional compensation for cultivated land protection. The results showed that: (1) there were obvious differences in the surpluses and deficits of cultivated land protection externalities among different cities in Henan Province. Under provincial boundary, there were 9 surplus areas and 9 deficit areas. Overall, the northwest was in the deficit area, the northeast in the moderately surplus area and the southwest in the moderately and highly surplus areas. Under the national boundary, the proportion of areas with deficit cultivated land protection externalities increased, and that with surplus cultivated land protection externalities declined with increasing per-capita grain consumption. On per-capita grain consumption levels of 380 kg, 400 kg, 420 kg and 435 kg, the percentages of the areas (cities) with cultivated land protection surplus were 88.89%, 83.33%, 77.78% and 72.22%, respectively. (2) There were obvious differences in spatial distribution of surpluses and deficits of cultivated land protection externalities in areas/cities of Henan Province between at provincial and nation boundaries. From provincial boundary to national boundary, the deficits of cultivated land protection externalities weakened, the surpluses strengthened. Then some areas with deficits changed from deficit to surplus in the same cities. It was concluded that the multi-level compensation systems should be established in the future according to spatial distribution regularities of surpluses and deficits in cultivated land protection externalities in combination with construction of main functional regions. Meantime, the paying areas and accepting areas, as well as standards of economic compensation for cultivated land protection should be defined scientifically.

Effect of phosphorus and silicon application on the uptake and utilization of nitrogen, phosphorus and potassium by maize seedlings

ZHANG Jiali, ZHU Conghua, DOU Pan, MA Xiaojun, WANG Xinglong, KONG Fanlei, YUAN Jichao

2017, 25(5): 677-688. doi: 10.13930/j.cnki.cjea.170222

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Abstract:
This study tested the effect of three levels of phosphorus (P)[1.0 mmol (P)·L^-1 (P_1.0), 0.1 mmol (P)·L^-1 (P_0.1) and 0.01 mmol (P)·L^-1 (P_0.01)] and three levels of silicon (Si)[1.5 mmol (Si)·L^-1 (Si_1.5), 0.75 mmol (Si)·L^-1 (Si_0.75) and 0 mmol (Si)·L^-1 (Si₀)] on a range of characteristics of'Zhenghong 2' and'Zhenghong 115' maize cultivars. The study analyzed dry matter, leaf area, root morphology and NPK contents of maize to determine the effects of the combined application of Si and P on maize root growth, dry matter accumulation and NPK accumulation and utilization at seedling stage. The results indicated that P deficiency not only suppressed maize seedling growth, but also decreased root length, root volume, root surface area, leaf area, NPK assimilation and dry matter accumulation, and the effects were strengthened with decreasing P concentration. The enhanced maize root-to-shoot ratio at seedling stage increased the distribution rates of P and N in root system and the accumulation efficiency of NPK in dry matter, which improved the adaptation of rice to P-deficient environments. P deficiency stress enhanced root growth and P absorption and accumulation more in'Zhenghong 115' than in'Zhenghong 2' maize cultivar. However, the distribution rate in the root system of'Zhenghong 115' maize cultivar increased substantially under P deficiency. Si accelerated maize root growth, increased NPK accumulation, improved the distribution rate of NPK in aboveground system, increased leaf area and dry matter accumulation under normal P condition (P_1.0). Under medium P deficiency (P_0.1), the application of Si alleviated P deficiency stress through increasing NPK accumulation in maize seedlings, furthermore, it also accelerated growth of both root and shoot system. Under severe P deficiency (P_0.01), the application of Si had no significant effect on root growth and dry matter accumulation, but it increased the PK accumulation in root system. It was therefore concluded that there existed significant synergetic and coordination effects of P and Si on beneficial traits of maize at seedling stage.

Influence of different fertilization modes on soil fertility and crop yield in Dongting Lake upland areas

CHEN Ge, TANG Chunchun, LI Zusheng, HUANG Yunxiang, ZENG Xibai, WEN Jiong, GAO Xue, ZHANG Qian

2017, 25(5): 689-697. doi: 10.13930/j.cnki.cjea.160824

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Abstract:
An experiment was conducted under cotton-rapeseed crop rotation system in upland areas of Dongting Lake to determine the effect of different fertilization modes on soil fertility and crop yield. The treatments in the experiment included none fertilization (control), conventional fertilization (TF), formula fertilization (NPK) and different combinations of chemical and organic fertilizers (10%OM, 30%OM and 50%OM, in which 10%, 30% and 50% of total N was from organic fertilizer). The results indicated that combined inorganic and organic fertilizer application greatly improved yields of cotton and rapeseed, with the highest yield under 50%OM treatment. The order of yields from high to low was: 50%OM, 30%OM, 10%OM, NPK, TP and CK. The yields of cotton and rapeseed under 50%OM were respectively 24.52% and 29.57% higher than those under TP and also 46.03% and 49.07% higher than those under NPK. The inter-annual variation in crop yields under organic fertilizer treatments was less than 20%, which was obviously lower than those under TP, NPK and control. Organic fertilizer application not only improved crop yield, but also supported stable production. 50%OM treatment increased soil organic matter, total N, alkali-hydrolyzable N and quick-acting K respectively by 57.5%, 38.2%, 65.1% and 48.1% over those before the experiment. Soil available P increased with increasing application of P fertilizer. However, soil organic matter and nutrient content decreased in control treatment. The linear equation (y=ax+b) well fitted the changes in soil organic matter and nutrient (y) with time (x). Reasonable application of organic plus inorganic fertilizers had significant potential to improve crop yield and soil fertility in upland soils in Dongting Lake area. The 50%OM treatment showed the best effects under the experimental conditions.

Effects of irrigation threshold and lateral depth on tomato growth in greenhouse

GU Jun, NIU Wenquan, LYU Wang, LI Yuan, LIANG Bohui, GUO Lili

2017, 25(5): 698-707. doi: 10.13930/j.cnki.cjea.161051

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Abstract:
Soil water is critical for crop growth, yield and water use efficiency. In order to study mutual responsive mechanism between root growth and different irrigation methods (e.g., deficit and lateral irrigation) on soil water distribution, root distribution and dry matter distribution in tomato, a test of subsurface drip irrigation was conducted in a sunlit greenhouse in Dazhai Villiage, Dazhai Town, Yangling City, Shaanxi Province. The study was designed as a 2-factor experiment-lateral depth (D) and irrigation threshold (I). The lateral depth was divided into 4 levels (0 cm, 10 cm, 20 cm and 30 cm) below the surface of ridges and the irrigation threshold set at 50%, 60% and 75% of field capacity. Each treatment was repeated 3 times. The results showed that lateral depth had a significant effect on water consumption of tomato under mild water deficit (75% of field capacity) and moderate-mild water deficit (60% of field capacity) conditions, while lateral depth of 10-20 cm was much better for root water uptake than other treatments. Increase in lateral depth reduced the distribution of roots in the 0-20 cm soil layer, but promoted the growth of roots in the 20-60 cm soil layer. Lateral depth had a significant effect on root growth in the 0-10 cm, 20-30 cm and 30-40 cm soil layers, but had no significant effect on root growth in the 50-60 cm soil layer. Root length and root surface area of fine roots (with diameter less than 1 mm) and coarse roots (diameter greater than 1 mm) of tomato were significantly affected by irrigation threshold. However, lateral depth only had a significantly effect on root length and root surface area of fine roots. Then mild water deficit and lateral depth of 20 cm favored root length and surface area growth of fine roots, but reduced the growth of coarse roots. Mild water deficit and lateral depth of 20 cm better favored total dry matter accumulation, while the 75% of field capacity treatment increased root dry matter allocation. Then lateral depth of 20 cm promoted dry matter accumulation of stems and leaves, but reduced the distribution ratio of root dry matter. For the observed responses, information on how root distribution and dry matter allocation in tomato adapted to different irrigation methods provided a useful guide for field production practices and possible indicator mechanisms for high quality/yield.

Effect of enhanced UV-B radiation on cotton growth and photosynthesis

QI Hong, DUAN Liusheng, WANG Shulin, WANG Yan, ZHANG Qian, FENG Guoyi, DU Haiying, LIANG Qinglong, LIN Yongzeng

2017, 25(5): 708-719. doi: 10.13930/j.cnki.cjea.160801

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It has been shown that the thinning of ozone layer continuously enhances ambient ultraviolet-B (UV-B) radiation. Enhanced UV-B radiation influences the growth, development and metabolism of crops, of which photosystem is the initial and most important target. In this study, UV-B radiation was increased by 20% and 40% by using ultraviolet lamp during the whole growth period of cotton under field condition, and its effect on cotton morphology, dry matter accumulation, photosynthetic pigment content and seed cotton yield were analyzed. The influencing mechanism of enhanced UV-B radiation on photosynthesis was also investigated by determining gas exchange parameters and chlorophyll fluorescence parameters in functional leaves. The results showed that the growth of cotton stems, leaves and dry matter accumulation were significantly inhibited by enhanced UV-B radiation. The inhibition effects of enhanced UV-B radiation on cotton were more obvious at seedling stage than that at later growth stages. Seed cotton yield also remarkably decreased with increasing UV-B radiation. The contents of chlorophyll a (Chl_a) and chlorophyll b (Chl_b) increased under the treatment of 20% above ambient UV-B radiation and there was no change in Chl_a/Chl_b. When UV-B radiation increased to 40% above ambient UV-B radiation, Chl_a, Chl_b and Chl_a/Chl_b significantly decreased. With increasing UV-B radiation, net photosynthetic rate (P_n) of functional leaves on cotton main stem significantly decreased. Although there were no change in stomatal conductance (G_s) and transpiration rate (T_r) under 40% increase in UV-B radiation, while intercellular CO₂ concentration (C_i) increased, which indicated that the decline in photosynthesis was mainly caused by non-stomatal limitation factors. The results of chlorophyll fluorescence parameters analysis showed that with increasing UV-B radiation, maximum quantum efficiency (F_v/F_m), operating efficiency (Φ_PSⅡ), linear electron transport rate (ETR) and photochemical quenching (qP) of PSII remarkably decreased, but non-photochemical quenching (NPQ) increased. All the chlorophyll fluorescence parameters were significantly correlated with P_n changes. Slowly relaxing NPQ (NPQ_S) and its proportion in NPQ significantly increased under enhanced UV-B radiation, which indicated that the photochemical efficiency of PSⅡ decreased as its reaction center was damaged by elevated UV-B radiation. The results demonstrated that photosynthetic leaf area, chlorophyll content and photosynthetic rate of cotton dropped under enhanced UV-B radiation during the cotton growth period. This inhibited cotton growth, material accumulation and seed cotton yield. Decrease in P_n due to enhanced UV-B radiation was closely related with the destruction of PSⅡ reaction center.

Ion response of sunflower at sprouting stage to mixed salt stress

MA Rong, WANG Cheng, MA Qing, HOU Peichen, WANG Xiaodong

2017, 25(5): 720-729. doi: 10.13930/j.cnki.cjea.160871

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Research on the mechanism of response of sunflower to salt stress can provide scientific basis for rapid screening of salt resistant varieties, a critical element in the exploitation of saline-alkali lands. In this study, salt-sensitive variety 'YK18', moderately salt-tolerant variety 'YK06' and highly salt-tolerant variety 'GF01' of sunflower were used to analyze seed germination, ion accumulation and distribution in seedlings of different varieties of sunflower under mixed salt (NaCl/Na₂SO₄ of 9/1 mol) concentrations of 0 mmol·L^-1, 50 mmol·L^-1, 100 mmol·L^-1, 150 mmol·L^-1, 200 mmol·L^-1 and 250 mmol·L^-1. Scanning ion-selective electrode technique (SIET) was used to determine K⁺, Na⁺ and Ca²⁺ fluxes in roots after 24 h mixed salt stress. The results showed that seed germination, germination rate and germination index decreased under salt stress and the average germination time of oil sunflower extended. Under salt-stress condition, there was an obvious K⁺ efflux in roots. Compared with high salt-tolerant variety 'GF01', the roots of salt-sensitive variety 'YK18' and moderate salt-tolerant variety 'YK06' had higher K⁺ extrude capacity. Salt stress led to a net Na⁺ influx in the range of 0-100 mmol·L^-1 in mixed salt concentrations, and was highest for salt-sensitive variety 'YK18'. The pattern of Na⁺ flux in roots changed significantly under higher mixed salt concentrations (150-200 mmol·L^-1) and there was a clear efflux of Na⁺ in seedlings, which was highest for salt-tolerant variety 'GF01'. After mixed salt stress, Na⁺ content increased while K⁺ content decreased, resulting in a decrease in K⁺/Na⁺ ratio in the whole plant. Salt-tolerant variety 'GF01' had the lowest K⁺/Na⁺ ratio, had the potential to intercept Na⁺ in stems under low salt concentration ( < 150 mmol·L^-1). The sunflower variety 'GF01' had higher capacity to extrude Na⁺. As a result, 'GF01' had the least Na⁺ content (for the whole plant) and had higher K⁺/Na⁺ ratio in leaves under high salt stress (≥150 mmol·L^-1). SIET data also showed that after 24 h exposure to mixed salt stress, a clear Ca²⁺ influx in salt stressed seedlings that was proportional to the mixed salt concentration developed. The Ca²⁺ absorption rate of 'GF01' was higher than that of 'YK18'. In conclusion, different degrees of salt tolerance in different sunflower varieties were regulated by Na⁺ and K⁺ absorption and efflux as a mode of adaption to the salt stress environment. Strong salt tolerant variety had stronger ability to protect K⁺, but K⁺ can also be protected by regional Na⁺ application (under low salt concentration), salt rejection mechanisms to enhance salt tolerance and then by maintaining reasonable K⁺/Na⁺ ratio in leaves. In addition, accelerated absorption of Ca²⁺ by plants alleviated salt damage in plants after salt stress. The results of the study provided theoretical basis for the selection and cultivation of salt tolerant varieties. And the established ion flux detection technique was a reliable screening method for salt tolerant varieties selection in plant breeding.

Effect of sick rhizosphere soil under tomato continuous cropping on soil nematodes, microbes and tomato growth

MA Yuanyuan, LI Yulong, LAI Hangxian, GUO Qiao, XUE Quanhong

2017, 25(5): 730-739. doi: 10.13930/j.cnki.cjea.160792

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Abstract:
Continuous cropping of tomato is a widespread practice that severely restricts sustainable tomato production. The interaction between soil nematodes, soil microbes and plants may be related with root-knot nematode disease due to continuous cropping. However, a little attention has been paid to the interrelatedness of these factors or the effect of continuous cropping on the relationship among soil and other 3 factors. Thus, this study explored the effects of sick soil (root-knot nematode infecting soil) on tomato root-knot disease, mechanism of micro-ecological obstacles and plant growth of continuously cropped tomato with a pot experiment. The abundances and communities of microbes and nematodes in root-zone soils and the activities of defensive enzymes in seedling leaves of tomato were analyzed to determine what pathogenic mechanism existed in such cropping systems. Compared with healthy soil, sick soil caused the following changes: (1) at seedling stage, root-knot nematodes began to infect roots and therefore root-knots appeared on tomato roots. Compared with the healthy soil, silk soil increased the abundance of soil nematode by 390.4%. At maturity, the infection rate of root-knot nematode was 62.7% and the related disease index was 80.0%. (2) The growth of tomato was restrained and the activities of defense enzymes reduced. The dates of blossoming and fruiting delayed too. Fresh biomass of shoot and root at maturity significantly (P < 0.05) decreased by up to 50.2% and 33.1%, respectively. Also the quantity and fresh mass of fruit significantly (P < 0.05) decreased by up to 59.7% and 68.2%, respectively. While compared with healthy soil, PPO activity of seedling leaves significantly (P < 0.05) decreased (by 15.8%), and POD activity significantly (P < 0.05) increased (by 24.0%) for silk soil. (3) Tomato roots became easily infected by harmful bacteria (Pseudomonas brassicacearum). The number of pathogenic bacteria P. brassicacearum in tomato roots in sick soils was 463 times greater than that in healthy soils. The total number of bacteria, fungi and actinomycetes in rhizosphere soils increased by 46.3%, 94.5% and 134.0%, respectively. (4) The abundance of soil nematodes increased nearly 3 times, among which the abundance of fungi-feeding nematodes, bacteria-feeding nematodes and plant-parasitic nematodes increased by 1.6, 3.3 and 7.3 times, respectively. The abundance and diversity of plant-parasitic nematodes greatly increased, of which root-knot nematode accounted for 95.6%. In conclusion, the inoculation of sick soils from the root-zone under continuous tomato cropping had complex effects on root-zone soil ecology. It inhibited tomato growth and increased the incidence of root-knot nematode disease by influencing the abundance and diversity of microbes and nematodes in root-zone soils and also by influencing biochemical metabolism of tomato. Mass propagation of plant parasitic nematodes and plant pathogenic bacteria decreased defensive enzyme activity and stress resistant ability of tomato, which in turn led to more severe root-knot nematode infection with significant inhibitory effect on tomato production. The negative effects of continuous cropping on tomato growth were caused by the interactions among root-zone soil microbes, root endophytes and soil nematodes.

Effects of adding proportions of functional absorption materials on performance of new slow-release urea

WU Zhenyu, YANG Yang, ZHOU Zijun, NI Xiaoyu, YU Lixiang, LU Hewei, LIU Binmei, WU Yuejin, WANG Yu

2017, 25(5): 740-748. doi: 10.13930/j.cnki.cjea.161006

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Abstract:
Nitrogen fertilization enhances crop productivity. However, common nitrogen fertilizers have some drawbacks (e.g., high risk of nitrogen leaching and ammonia volatilization) which lead to environmental and economic problems. The development and application of new types of high-efficiency fertilizers such as matrix-based slow-release fertilizer is a possible solution to these drawbacks. Matrix-based slow-release fertilizer has the advantages of simple production process, low cost and stable performance. The added proportion of modified functional absorption materials affects the performance, effective component content and production cost of slow-release fertilizers. However, little is known about the relationship between the added proportion of functional absorption materials and performance of slow-release urea. The objective of this study was to assess the effects of added proportion of functional absorption materials on the performance of a new materials-based slow-release urea. The tested functional absorption materials were modified zeolite and bentonite by using organic polymer. The nitrogen loss characteristics and field crop performance of the functional absorption materials-based slow-release urea (SRU) were analyzed using sand leaching, ammonia emission chamber and field maize experiment methods. Experimental treatments mainly consisted of common urea (CU, as control), and six SRUs added 1%, 2%, 3%, 4%, 5% and 6% functional absorption materials, respectively. Then nitrogen release characteristics of urea were described using the first-order kinetic model. In field conditions, soil in the plough layer (0-20 cm) and ear leaves of maize were sampled at silking stage for measurement of soil available nitrogen concentration, leaf chlorophyll content and nitrate reductase activity. The optimal added proportion of functional absorption materials in slow-release urea was calculated using a polynomial model. Results showed that the highest nitrogen leaching ratio occurred at the first leaching-i.e., 81.6% in common urea treatment and 27.7%-42.8% in SRU treatments. The cumulative nitrogen leaching ratio in common urea treatment reached 100% at the sixth leaching, while that in SRU treatments reached 90% only at the twelfth leaching. Slow-release urea with 6% functional absorption materials had the best performance of reducing nitrogen leaching. The nitrogen release characteristics was fitted by the first-order kinetic equation-N_t=N₀(1-e^-bx), where N_t is cumulative nitrogen release ratio, N₀ is the maximum cumulative nitrogen release ratio, b is nitrogen release ratio constant, and x is the number of leaching. Nitrogen release ratio constant (b) of SRU treatments was 67.4%-82.6% lower than that of CU treatment, while cumulative ammonia emission of SRU treatments was 15.8%-39.3% lower than that of CU. Available nitrogen content in the plough layer of maize field increased with increasing proportion of functional absorption materials, which also increased leaf chlorophyll content and nitrate reductase activity in maize. SRU increased maize biomass and grain yield. Calculation based on a polynomial model showed that the highest plant biomass (15 829 kg·hm^-2), shoot biomass (164.0 g·plant^-1), root biomass (26.9 g·plant^-1) and grain yield (6 769 kg·hm^-2) were obtained in SRU treatments with 5.28%, 4.80%, 5.24% and 4.76% functional absorption materials, respectively. Overall, slow-release urea with 5% functional absorption materials had better performance in terms of nitrogen loss reduction via leaching and ammonia emission reduction, maize nitrogen nutrient improvement, and then maize biomass and grain yield increase.

Soil moisture dynamics of apple orchards in Loess Hilly Area of northern Shaanxi Province

LI Jiayang, WANG Yanping, HAN Mingyu, ZHANG Linsen, HAN Wenshe

2017, 25(5): 749-758. doi: 10.13930/j.cnki.cjea.160758

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Abstract:
Knowledge on the variation in soil moisture is critical for the scientific management of orchards, the efficient utilization of limited rainfall and the improvement of fruit production and fruit quality. In this study, a comprehensive soil moisture monitoring method was used in combination with FDR, neutron moisture meter and oven-drying to determine the general characteristics of soil moisture in loess hilly apple orchards of northern Shaanxi Province. Also the variation in soil moisture at different sampling sites around orchard trees and the environmental effects of different dry-farming measures (e.g., straw mulching, ridge film mulching with furrow rainwater harvesting and organic fertilizer mulching) were investigated in 6-year-old 'Fuji' apple orchard for the period from April 2015 to June 2016 in Mizhi County in Shaanxi Province. The results showed that seasonal drought was quite severe, especially during the shoot growth and young fruit development stages. The degree of soil drought in spring was highly dependent on soil water storage in the last winter. Soil moisture in the 0-60 cm soil layer (root-zone layer) varied with rainfall and had seasonal variation characteristics, but lagged behind that of rainfall. The effect of rainfall on the variation of soil moisture weakened with increasing soil depth. Soil moisture in soil layer below 200 cm was relatively stable, but soil desiccation occurred in 6-year-old apple orchard in the hilly region. There was an obvious low humidity layer in the 90-300 cm soil, where volumetric soil water content was less than 12% for the whole year. Soil moisture increased with increased sampling distance from apple tree. While the regression equations of soil moisture between apple plants and between apple tree rows (y) with distance to apple tree were respectively y=0.010 5x+6.870 2 (R²=0.996 6) and y=0.014x+7.691 2 (R²=0.982 7), the mean soil moisture for the sites was closest to the one 105 cm away from the tree Soil moisture at different sites from tree between rows was significantly higher than that at equivalent distance between plants (P < 0.05). Compared with CK (no mulching or irrigation), dry-farming measures such as the straw mulching, ridge film mulching and furrow rainwater harvesting and organic fertilizer mulching effectively improved soil moisture environment. To a certain extent, these dry-farming measures were recommended for dealing with the issue of soil water supply and demand, especially during plant growing season. Among the measures, ridge film mulching and furrow rainwater harvesting had the highest degree of preservation of soil moisture. Thus ridge film mulching and furrow rainwater harvesting was recommended as the most effective agricultural measure in preserving soil moisture in rainfed apple orchards in Loess Hilly Areas of northern Shaanxi Province.

Effect of vegetable cropping system on total nitrogen, phosphorus and COD in farmland leachate

TENG Yanmin, HAN Hui, HAO Ziyi, YANG Hefa, LI Ji

2017, 25(5): 759-768. doi: 10.13930/j.cnki.cjea.160940

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Abstract:
At present, China has the largest land area under greenhouse vegetable cultivation in the world. Greenhouse production has frequently been associated with excessive fertilizer use and high proportion of organic fertilizer input. These factors have induced changes in soil nutrient content and physicochemical properties, and enhanced leaching of soil nitrogen and phosphorus. However, comparative investigations of soil nutrient losses due to leaching in conventional greenhouse vegetable cropping systems have been inconclusive. Thus this study investigated long-term field trials of three different greenhouse vegetable cropping systems in terms of total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD) leaching. The experiment, started in March 2002, was carried out in three side-by-side greenhouses with three cropping systems-(1) organic system (ORG), in accordance with IFOAM Basic Standards by using only compost and physical and biological control; (2) integrated system (INT), with lower inputs of agrochemicals and compost; (3) conventional system (CON), with chemical fertilizers and composts applied in accordance with local practices. The application rates of compost and chemical fertilizer in the INT system was half of those in the ORG and CON systems. While pest control in ORG included physical control and biological fungicide, sulfur fumigation was used to control plant diseases. In the INT and CON systems, insecticides and fungicides were used to control insects and diseases. Each treatment was applied to the entire greenhouse. Chemical fertilizer was in the form of urea, calcium superphosphate and potassium chloride at the ratio of 3:5:4. Compost composed of cow manure, dry chicken manure and straw with VT microbial agent. All three systems were under the same irrigation scheme and 13 times of flood irrigation was used during the two seasons in 2014 in each cropping system, with single-event irrigation amount of 975 m³·hm^-2. Leaching soil water at about 1 m deep was collected using lysimeter within 4-6 days after each irrigation and then analyzed for TN, TP and COD. The objective was to build the theoretical base for the development of sustainable agricultural systems. Results showed that the amount of TN in the leachate in ORG during the two seasons was 137.02 kg·hm^-2, respectively 12.0% and 25.9% lower than that in INT and CON cropping systems. The amount of TP in the leachate collected under ORG was 18.23 kg·hm^-2, which was respectively 51.2% and 119.9% higher than that in INT and CON systems. The COD in the leachate under ORG cropping system was 856.99 kg·hm^-2, which was also 32.4% and 3.1% higher than that in INT and CON systems, respectively. The trends of variation in TN, TP and COD in leachates under three systems were significantly different. The TN in leachate in prophase was constantly high, with an obvious peak after top dressing, which then decreased rapidly before it maintained a low level in June. The loss of TP via leaching changed smoothly, with an increasing trend followed by a decreasing and eventually reaching a peak level in June or July. The COD in leachate slightly decreased initially to the minimum point before top dressing and then gradually increased in May. In summary, it was concluded that ORG system reduced nitrogen loss via leaching, but significantly increased the risk of leaching of phosphorus and COD compared with INT and CON systems.

Characteristics of ammonia emission from large-scale livestock/poultry breeding and its mitigation countermeasures in Chongqing

LIAO Renjun, CHEN Yucheng

2017, 25(5): 769-777. doi: 10.13930/j.cnki.cjea.161078

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Abstract:
With environmental concerns raised on air quality and livestock/poultry industries, there has been an increasing pressure on rapidly developing large-scale livestock/poultry breeding to take actions to mitigate these concerns. As such, it was necessary to explore ammonia emission from large-scale livestock/poultry industries and its characteristics for management of air quality and prevention of livestock/poultry pollution driven by sound scientific knowledge and countermeasures. With data on ammonia emission from large-scale livestock/poultry breeding and the related coefficients, this study calculated the amount of ammonia emission in 2013 in large-scale livestock/poultry breeding in Chongqing. The paper also analyzed the characteristics of ammonia emission and the corresponding mitigation countermeasures for large-scale livestock/poultry breeding. The results showed that total ammonia emission from large-scale livestock/poultry breeding in Chongqing was 17 102.92 t in 2013 and the emission intensity was 0.21 t·km^-2. Hechuan, Fengdu and Tongnan were the top three counties for ammonia emission, with their contribution accounting for 30.19% of the total ammonia emission. Jiangbei County had the least ammonia emission in Chongqing. Ammonia emission intensity for Bishan County was the highest, followed by Hechuan County, with respective emission intensity of 1.17 t·km^-2 and 1.09 t·km^-2. Chengkou County had the least, with emission intensity of 0.01 t·km^-2. Based on the spatial distribution characteristics, there was significant spatial auto-correlation in the spatial distribution of ammonia emission from large-scale livestock/poultry breeding industries in Chongqing. Through localized spatial auto-correlation analysis, it was noted that four counties belonged to high-high type, five counties belonged to low-low type and none belonged to high-low type or low-high type of spatial distribution of ammonia emission. Pig breeding was the highest contributor to ammonia emission, with 9 538.63 t of emitted ammonia which accounted for 55.80% of total large-scale live-stock/poultry breeding emission. Then layer breeding accounted for 15.87% and broiler breeding (with the least value) accounted for 6.68% of ammonia emissions. Ammonia emissions from livestock and poultry manure differed in the stages of animal house, storage and utilization of manure. For poultry, ammonia emissions of stage in breeding house were the dominant of overall stages, with a contribution rate of over 60%. For livestock, however, ammonia emission contribution rate at utilization stage was the highest. In order to reduce emissions, it was need to focus on management of dairy cattle breeding. Such management countermeasures included the use of feed stocks with low ammonium content, renovation of stable, covered or sealed manure, and injection application of manure.

Evaluation of ecological security of coastal saline land in Hebei

YU Shuhui, ZHOU Xiangli, QING Jichuan, CHEN Zikang, GUO Aiqing, QIN Ling

2017, 25(5): 778-786. doi: 10.13930/j.cnki.cjea.160705

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Abstract:
Severe soil salinization and fragile ecological environment are characteristic features of coastal saline land. It is therefore very important to analyze the state of ecological security of coastal saline land and the driving mechanisms in order to lay the basis for struc-tural land adjustment and land function upgrade. Based on the land use types, a classification standard of land use ecological security (LUES) in coastal saline area of Huanghua City, Hebei Province was developed. LUES values in 2000, 2005 and 2010 were calculated in Huanghua City, and key land use types were explored. Based on the above results, we selected 16 indicators (including LUES) combining with TM data and socio-economic data for 2000-2010, coupling with Erdas, ArcGIS and Fragstats platforms, to construct the P-S-R land ecological security evaluation model, and then used this model to evaluate the state of land ecological security status in Huanghua City. The results showed that: (1) LUES value for Huanghua City was 0.458-0.466 during the period of 2000-2010, LUES was at critical security state; and there was an urgent need to control the areas of construction land, salty land and heavily saline land. (2) Improvement of LUES in Huanghua City was mainly due to the decreased of soil salinization. Positive ecological effects of decrease in both moderate and severe saline land areas, and increase in lightly saline land areas exceeded the negative ecological effects of increase in construction land areas. (3) The land ecological security index (LESI) of Huanghua City showed a rising trend year by year, and the safety state improved from less secure (LESI=0.431) in 2000 to safe (LESI=0.666) in 2010. (4) The stress index (P) decreased, while the response index (R) increased year by year. For 2010, R contributed the most to LESI (45.3%), which indicated that the developed measures reduced ecological risk of land in the study area. The results provided a scientific basis for ecological utilization of land in Huanghua City.

2017 Vol. 25, No. 5