Showing papers in "Chinese Journal of Eco-agriculture in 2011"

Research advances on source/sink intensities and greenhouse effects of CO_2,CH_4 and N_2O in agricultural soils

Abstract: Climate change is an increasing global challengeGreenhouse gas emission via anthropogenic processes is the main cause of global warmingCO2,CH4 and N2O are the main greenhouse gases,accounting for ≈80% of greenhouse effectIt is esti-mated that each year,5%～20% of CO2,15%～30% of CH4 and 80%～90% of N2O in air are emitted from soilsAgricultural soils are the main sources of greenhouse gas emissionThis work expatiated the mechanisms and affecting factors of greenhouse gas forma-tion,emission and absorption in agricultural soilsAnd the contribution of farmland ecosystem to greenhouse effects was discussedIt was indicated that anthropogenic factors such as land use and agricultural activity influenced greenhouse gas formation,emission and absorption in agricultural soilsBecause anthropogenic processes affected agricultural ecosystems,greenhouse gas emission re-ductions for stabilized carbon and nitrogen were possible through improved agricultural cultivation and production systemsThis study summarized the latest research advances in source/sink intensities of greenhouse gas emissions from farmlands and how that contributes to greenhouse effectThe study suggested that accurate estimation of source/sink intensities of greenhouse gases and ap-propriate assessments of greenhouse gas effects were the theoretical basis for reducing greenhouse gas emissions and uncertainties in predicting climate change

Antagonistic effect of multifunctional actinomycete strain Act12 on soil-borne pathogenic fungi and its identification

Abstract: Antagonistic effects of multifunctional actinomycete strain Act12 on six soil-borne pathogenic fungi were determined using agar block method and inhibitory test.The strain Act12 was identified by analyses on its morphological character,physiological and biochemical characteristics,as well as 16 S rDNA sequence.The results showed varying degrees of Act12 antagonism against all tested six soil-borne pathogenic fungi.The widths of inhibitory zones against Fusarium equiseti and F.oxysporum f.sp.niveum were 20.5 mm and 18.4 mm,respectively.The rate of bacteriostasis of Act12 axenic fermentation filtrate against F.equiseti after 48 h cul-tivation was 83.2%.Based on micro-morphology,and cultural,physiological and biochemical characteristics,as well as 16 S rDNA sequence analysis,Act12 strain was identified as Streptomyces pactum.

Soil greenhouse gas emission in winter wheat/summer maize rotation ecosystem as affected by nitrogen fertilization in the Piedmont Plain of Mount Taihang,China

Abstract: The effect of soil nutrient augmentation via nitrogen deposition or fertilization on the processes of storing,releasing and re-absorbing of methane(CH4) carbon dioxide(CO2) and nitrous oxide(N2O) greenhouse gases(GHG) in soil ecosystems are poorly understood.This study described an original field experiment for measuring soil GHG flux at nitrogen application rates of N0 [0 kg(N)-hm-2],N200 [200 kg(N)-hm-2],N400 [400 kg(N)-hm-2]and N600 [600 kg(N)-hm-2] in winter wheat/summer maize double cropping system in the Piedmont Plains of Mount Taihang.CH4,CO2 and N2O emissions from soils under the winter wheat/summer maize rotation system were measured from July 2008 through June 2010 using the static transparent chamber and gas chromatogra-phy technique.The results showed that soils under winter wheat/summer maize ecosystems served as CH4 sink,and CO2 and N2O sources.With increasing nitrogen application,CH4 absorption rate decreased and CO2 and N2O flux rates increased.In winter wheat season,CH4 absorption rate under N0 treatment was significantly higher than under other nitrogen treatments.Both CO2 and N2O emission flux rates under N600 treatment were significantly higher(P0.05) than under N0 treatment.Nitrogen fertilization and irrigation sharply induced CO2 and N2O peak flux emissions and decreased CH4 peak absorption.Rising soil temperature,precipita-tion or alternating wet/dry weather increased soil N2O and CO2 emission flux rates.Negative N2O flux rates were observed under low temperature and high evaporation conditions in N0 application treatments in winter.CH4 emission accumulation for 2008-2009 un-der N0,N200,N400 and N600 treatments was -1.42,-0.75,-0.82 and -0.92 kg-hm-2-a-1,respectively.For 2009-2010,it was -2.60,-1.47,-1.35 and -1.76 kg-hm-2-a-1,respectively.CO2 emission accumulation for 2008-2009 under N0,N200,N400 and N600 treatments was 15 598,19 346,21 456 and 29 013 kg-hm-2-a-1,respectively.For 2009-2010,it was 10 318,11 474,13 984 and 20 639 kg-hm-2-a-1,respectively.Then N2O emission accumulation for 2008-2009 under N0,N200,N400 and N600 treatments was 1.05,2.16,5.27 and 6.98 kg-hm-2-a-1,respectively.Also for 2009-2010,it was 1.49,2.31,4.42 and 5.81 kg-hm-2-a-1,respectively.

Nitrogen flux and its manipulation in the cropland ecosystem of the North China Plain

Abstract: The North China Plain(NCP) is one of the areas of intensive cereal production in China,producing large winter wheat and summer maize.A critical challenge facing the agro-production sector of the NCP,however,includes over-application of chemical fertilizers,excessive soil nutrient accumulation and declining nutrient use efficiency.This study investigated relationship between nitrogen(N) flux and crop nutrient uptake/loss processes under conventional fertilization at 400 kg(N)-hm-2-a-1 in the winter wheat/summer maize crop rotation system in the piedmont region of NCP.The management practices of the fields were adjusted on the basis of the characteristics of N output fluxes.The results showed that in the region,a total N input of 561-580 kg-hm-2 and out-put of 468-494 kg-hm-2 resulted in a N surplus of 86-93 kg-hm-2 per year.Organic N load in the study area was 24-36 kg-hm-2.N loss via ammonia volatilization and NO3--N leaching was 60 kg-hm-2 and 47-84 kg-hm-2 per year,respectively,collectively ac-counting for 30% of applied N fertilizer in the region.N loss via nitrification-denitrification was only 5.0-8.7 kg-hm-2 per year,ac-counting for 1%-2% of applied N fertilizer.Ammonia volatilization and NO3--N leaching were the main modes of N loss,and there-fore the main drivers of lower N fertilizer utilization rate in the study area.Appropriate management practices such as adjustments of the rates and time of N fertilization and irrigation were important for decreasing ammonia volatilization,NO3--N accumulation in deep soil profile and therefore the mitigation of NO3--N loss in the region.Amendments with wheat/corn straw changed the rates of N transformation and migration in the soil,which also resulted in low NH3 loss and NO3--N leaching.Analysis of precision fertiliza-tion via NO3--N or hyper-spectra information feature also showed that the main indices of N loss were the amount of soil available nutrient and crop nutrient content.This laid the basis for efficient fertilizer application in the study area.Control-release fertilizer and precision fertilization techniques improved crop nutrient uptake,which in turn increased N use efficiency.An integrated fertilizer utilization technique for sustainable environmental and agricultural development in the piedmont region of NCP was possible.

Changes in and correlation analysis of quality indices of hydroponic lettuce under short-term continuous light

Abstract: Nitrate easily accumulates in vegetables(especially leaf vegetables) and poses serious health hazard if excessively in-gested.Light is a critical environmental factor influencing plant nitrate content.In this study,changes in contents of nitrate,soluble sugar and vitamin C(Vc) in hydroponic lettuce under 72 h continuous light and their correlation were analyzed.The aim of the study was to explore quality control measures of vegetables grown in controlled environments.The study showed that nitrate content in both leaf blade and petiole decreased significantly with variational rate in different time.Nitrate content in blade and petiole tended to steady after 24 h and 48 h continuous light respectively,while soluble sugar and Vc contents increased rapidly at a roughly con-stant rate and showed little trend of slowing down.There was no significant difference between blade and petiole soluble sugar con-tents.However,blade Vc content was much higher than that in petiole.Both in blade and petiole,nitrate content was significantly negatively correlated with soluble sugar and Vc contents.The results showed that short-term exposing to continuous illumination was suited to produce high quality lettuce with perfect unity of low nitrate accumulation and high soluble sugar and Vc contents.

Character evolution and branch classification of Brassica juncea (L.) Czern. et Coss

Abstract: In this paper, 67 B. juncea germplasm resources were used to determine character evolvement and branch classification based on 52 morphological traits by the maximum synchronization method. In the study, Cleome spinosa Jacq. from Capparidaceae was used as out-group. The results showed unique, homochronous or asnychromous evolution rules of basal leaves, leaves in elongated stems, bolting stem leaves and flowers traits of B. juncea. Sixty-seven B. juncea germplasm resources were classified into two groups, wild and cultivated groups. Regardless of whether the germplasms was wild or cultivated, germplasms of a group always came from one region or different regions with similar climatic conditions. The results indicated similarity in character evolution of B. juncea germplasm resources that was closely related with geographical and climatic backgrounds of the origins.

Changes and driving forces of land use/cover and landscape patterns in Beijing-Tianjin-Hebei region

Abstract: Conversion matrix of land use/cover,landscape fragmentation index(LFI) and landscape diversification index(LDI) were used to quantitatively and qualitatively analyze changes in land use/cover(LUC) and landscape pattern(LP) for 1990-2000 in Beijing-Tianjin-Hebei(BTH) region and their driving forces.Two typical sample belts were used in the study.The results showed that changes in LUC and LP were significant especially in the residential areas of Beijing,Tianjin and Shijiazhuang cities.The appli-cation of component and correlation analyses on socio-economic statistical data showed that LUC and LP changes in the region were mainly driven by socio-economic,agro-production and transportation factors.Terrain and policy effects on the changes in LUC and LP were also analyzed and discussed.Complex terrains hindered human disturbances in the west/north mountain areas.Compared with mountainous areas therefore,the plains had more profound changes in LUC and LP in the study area.On the other hand,eco-logical policies such as conversion of croplands into forests and grasslands along with land development and consolidation consti-tuted critical modes of LUC and LP changes in mountainous regions.Comprehensive analysis on the driving forces of LUC and LP changes in the region showed that socio-economic factors were more important in the metropolises and that agro-production condi-tions dominated in traditional agricultural areas.The analysis and especially that of temp-spatial analysis provided a useful dimension to land resources management and protection in the BTH study area.

Monitoring soil moisture by apparent thermal inertia method

Abstract: Soil moisture is one of the most important indices for agricultural drought monitoring and water resources management.Remote sensing is a critical technology for monitoring spatial and temporal variations in soil water content.The thermal inertia method,which is a thermal infra red(IR) technology,has demonstrated advantages in monitoring soil water condition.Among the several models for computing soil thermal inertia by remote sensing,ascertaining the conditions for monitoring soil water content by thermal inertia remains a major obstacle.This paper proposed an improved model for calculating Apparent Thermal Inertia(ATI).In the first step,a new soil ATI model with improved algorithms for simulating net radiation was developed.Then a strict control ground experiment was conducted to test the proposed model.A total of 10 experimental plots with different vegetation covers and soil water contents were set up at the Luancheng Agro-Ecosystem Experimental Station of Chinese Academy of Sciences.The vegetation covers were fully representative by NDVI(normalized difference vegetation index).The actual measured land surface temperature,NDVI,albedo,soil water content,solar radiation and long-wave atmospheric radiation were used to compute ATI under different land cover and soil water conditions.Then correlation and regression analyses were finally done to relate ATI and soil water content.The results indicated that the proposed thermal inertia model reliably monitored the soil water condition,especially in low vegetation cover areas.For low vegetation cover(NDVI 0.35),the coefficient of determination between ATI and soil volumetric water content was 0.7.The proposed thermal inertia method was invalid for NDVI 0.35 and the corresponding coefficient of determination was 0.2.NDVI that was the equivalent of 0.35 could be critical for determining the applicability of the proposed model in monitoring soil water conditions.This was because temperature dynamics(the most critical criteria for calculating ATI) for bare and vegetated lands were different.However,the proposed model was not only simple,but it carries distinct physical meaning and easy-to-use interfaces.The experiment suggested that the model was applicable in reliably monitoring soil water conditions.

Progress in molecular and physiological mechanisms of water-saving by compensation for water deficit of crop and how they relate to crop production

Abstract: The theory and technology of water-saving through crop compensation for water deficit and how they relate to crop production are theoretically important and potentially promising in agriculture application Molecular and physiological mechanisms, however, still constitute those issues that need further research The molecular and physiological processes of water-saving of crop by compensation for moderate water deficit was systematically analyzed based on related research advances in recent years The researches results showed that water deficit and re-watering could change growth of plant nutritional organs such as roots, stems and leaves Osmo-regulation, transpiration, photosynthesis and other physiological processes were also altered by water deficit and re-watering Protein activity and molecular metabolism of crops adapted to changes in water availability A water deficit threshold controlled compensations in crop production With appropriate degree and duration of water deficit, crop water use efficiency improved and even increased (instead of decreasing) crop yield If widely adopted in agricultural production, water-saving technologies through compensation for water deficit could be vital for improving economic returns and food safety

Soil evaporation under sole cropping and intercropping systems and the main driving factors

Abstract: Several studies have shown that compared to sole cropping,well managed intercropping improves agricultural resources utilization efficiency,include radiation,nutrient,water and landHowever,high productivity of traditional intercropping system has mainly depended on high input of agricultural resourcesWith severe water shortages in recent years(especially in mainland China),intercropping system of farming has continuously declinedThe scientific challenge therefore is the determination of water consump-tion characteristics and systematic development of high-efficiency water-saving theories and technologies of intercropping systemIn this study,a field experiment(comprising of wheat or maize sole cropping and wheat-maize intercropping systems under three dif-ferent irrigation schemes) was conducted in 2008 in the Hexi Corridor oasis regionThe study investigated soil evaporation charac-teristics and associated driving factors under the different cropping systems and treatments with the aim of laying the scientific basis for developing optimized irrigation techniquesThe study showed that evapotranspiration(ET) under wheat-maize intercropping was 4144%～4715% higher than the average ET under wheat and maize sole cropping systemsTotal soil evaporation(E) of intercrop-ping system was significantly higher than that of sole cropping systemsHowever,daily E of intercropping system was significantly lower than that of maize sole cropping systemAlso compared with sole cropping system of maize,wheat-maize intercropping sys-tem enhanced E/ET ratioWith increasing irrigation,total water consumption increased significantly under intercroppingHowever,the difference in water consumption between two adjacent irrigation treatments under sole cropping systems of wheat and maize was insignificantThe difference in E of sole cropping maize and intercropping wheat-maize was insignificant for different irrigation schemesIt then implied that high water consumption of intercropping system was mainly driven by high transpirationAverage daily E was positively correlated with water content in the 0～30 cm soil profile,temperature in the 0～25 cm soil profiles and average leaf area index of the cropsHigh E was driven by high water content in the 0～30 cm soil profile and temperature in the 0～25 cm soil profile of maize sole cropping systemOn the average,wheat-maize intercropping not only reduced water consumption but also in-creased water and land use efficiency compared to sole croppingThis cut down wasteful crop transpiration,which was an effective means of water-saving irrigation

Changes in NDVI and yield of winter wheat cultivars with different plant types

Abstract: Plant type and irrigation scheme are key influencing factors of real-time yield estimation and monitoring of winter wheat in precision farming. In this paper, MODIS remote sensing data were used in combination with GPS and ground-truth non-remote sensing data to determine the dynamics of normalized difference vegetation index (NDVI) of winter wheat cultivars with different plant types under irrigation and non-irrigation conditions. The relationship between NDVI and yield of different winter wheat culti-vars in different growth stages was then analyzed. Results showed the trends in NDVI with developmental stages of different wheat cultivars were same, following a low-high-low curve. There were obvious differences in NDVI from jointing to booting stages for different cultivars, and NDVI for cultivars with horizontal plant types was higher than that for cultivars with erect plant types. It im-plied that the jointing-to-booting stage was the best period for identifying plant types of winter wheat cultivars. Even for the same cultivar, mean NDVI was obviously different at each growth stage for irrigated and non-irrigated lands. NDVI for irrigated winter wheat was higher than that for non-irrigated winter wheat, with a notable difference especially at the early heading stage. At early heading stage, NDVI was strongly correlated with yield in irrigated and non-irrigated lands. However, regression equation based on NDVI both in the early heading and filling stages gave better prediction for wheat yield than that based on NDVI only in the early heading stage. This was especially the case for non-irrigated wheat fields.

Effect of pre-flowering light deficiency on biomass accumulation and physio-logical characteristics of rice

Abstract: To lay the scientific basis for super rice production in light-poor areas,an experiment was conducted under real field conditionsThe experiment used a super-hybrid rice combination "II Youhang 2" to study the effects of pre-flowering light deficiency on rice biomass production and physiologyIn the experiment,shading rates were set at 55% and 85% from jointing through initial heading stageNatural light condition was set as the control of the experimentThe results showed that yield of light deficient treat-ments(shading rates of 55% and 85%) dropped significantly by 4825% and 7054% compared with the controlThe drop was mainly due to fewer numbers of spikes per plant and grains per panicleThere was no significant difference in seed setting rate between the control and shading treatmentsCompared with the control,biomass and harvest index of light deficient treatments also significantly droppedThis was attributed to restrained net assimilation rate(NAR) and leaf area index(LAI),which significantly retarded crop growth rateThere were inhibited pre-flowering dry matter accumulation,translocation and contribution to grain and vegetative organ under light deficiencyThe inhibition was enhanced with increased intensity of light deficiencyMoreover,net photosynthetic rate,nitrate reductase activity and bleeding rate decreased and MDA content increased under pre-flowering light deficit,and the change was becoming more obvious under high shading intensityPre-flowering light deficit weakened photosynthesis,membrane system and root activityIt also blocked photosynthate transport,and restrained leaf growth and NARThese factors limited photosynthetic produce capability,decreased biomass production and significantly dropped crop yield

Impact of warming climate on crop water requirement in Gansu Province

Abstract: Global warming is an increasingly worrisome environmental and climatic phenomenon.Global average temperature increased by 0.60～0.70 ?C over the last centuray,with an average temperature rise of 0.80～1.50 ?C in China.Northwest China is one of the most sensitive areas to climate change.Temperature(a critical factor of global warming) is often used in an integrated method to calculate crop water demand.In other words,temperature afftects climate change,which in turn affects crop water needs.Crop water requirements in Northwest China is therefore critical in farm water cycle.It is also an important hydraulic and water-saving parameter in agricultural research,planning and design.This study addressed issues such as: the effect of climate change on agricultural water demand in different regions,and current lack of systematic and quantitative data to support crop water requirement research in the face of global warming.This study analyzed the effects of warming climate on crop water requirement in Gansu Province under different temperature scenarios(future temperature increases of 1～4 ?C).The results showed that the effects of warming climate on crop water requirement were different for different crops.Warming climate greatly afftected water requirement of winter wheat,followed by spring wheat and maize.When future temperatures rose by 1～4 ?C,water requirement of winter wheat increased by 3.05%～12.90%,which was the equivalent of 13.2～81.2 mm.That of maize increased by 2.49%～10.80%,the equivalent of 9.9～60.6 mm.Then spring wheat water requirement increased by 2.74%～11.69%,the equivalent of 6.7～40.0 mm.Regional differences were noted in the impact of warming climate on crop water requirement.The impact of warming climate on crop water requirement was highest for arid regions,followed by semi-arid regions,and then semi-humid regions.The least effect was for humid regions.When future temperatures rose by 1～4 ?C,the temperature scenario caused additional irrigation water requirement of 1 243,1 302,1 374 and 1 465 million m3 for winter wheat;794,832,878 and 930 million m3 for maize;and 497,516,542 and 576 million m3 for spring wheat,respectively.Warming climate worsened water shortage problems in the study area.