Abstract:Through the study on soil erosion and agricultural non-point source pollution to the water body of the Fangbian valley in Nanjing,a new research approach,integrated quantitative monitoring,was introduced.It adopts the "3S" technique to gain necessary data to satisfy factors of the mathematical model of soil erosion monitoring.First,obtain accurate amount of soil loss through quantitat ive monitoring of soil erosion,and then work out an accurate non-point pollution sources distribution map and figure out pollution load to the reservoir based on the results obtained in the previous step and the annual mean soil nutrient contents under different land uses.Precision of the monitoring is verified through evaluation of the measured bedloads at the upstream and downstream hydraulic monitoring stations,while pollution load into the reservoir is determined through test and analysis of water samples and measured volume of runoffs.In 2002,the precision of monitoring of soil erosion was 93.62% in the studied area,and of the pollution load of total phosphorus into the water body from non-point sources was 77.79%.The results initially show that the method of integrated quantitat ive monitoring is characterized by precision,quickness and economization.

Abstract:Through field survey,lab analysis and reference to large volumes of soil profile data,study on basic soil taxonomy of Earth-cumulic Orthic Anthrosols(Lou soil) was carried out in Guanzhong,Shaanxi Province.Soil classification was made at the soil family level based on particle composition,soil mineral composition and soil temperature.Of the profiles with the control sections(0 to 160 cm) of soil <2 mm,the majority were of clay loam,and the minority of loams or sandy loam in texture.The soils were dominated with illite,mixed illite or vermiculite in mineral composition and mesic or low-thermic in soil temperature.The control section of the soil series was defined to be from the top of surface horizon down to 160 cm in depth or to the bottom of the diagnostic horizon when the bottom of the diagnostic horizon exceeds 160 cm in depth.The diagnostic horizon had 11 characteristic horizons,i.e.Fimic epipedon,Earth-cumulic epipedon,Mollic epipedon,Agric horizon,Argic horizon,Weak-argic horizon,Intensive-calcic horizon,Medium-calcic horizon,Weak-calcic horizon,Redoxic horizon and Weak-cambic horizon.Based on the data of the 9 profiles and other related data of Earth-cumulic Orthic Anthrosols(Lou soil),the soils could be sorted into 9 soil families and 9 soil series.Typical characteristics of the soil series and differences between the series were described.

Abstract:Mass fractal dimension of soil particles is one of the inherent properties of soil.However,some assumptions,such as uniform density,have been questioned in calculating soil mass fractal dimension.Additionally,traditional methods to obtain particle-size distribution(PSD) are laborious.For this reason,the concept of the volume fractal dimension of soil part icles is developed and a formula to calculate soil volume fractal dimension is introduced in this paper.Based on the conception of volume fractal dimension and the analysis of 178 soil samples from different land uses,some conclusions could be drawn as follows:the volume fractal dimension of soil particles was significant correlated with the volume percentage of soil clay contents;in soil profile of vegetable and tea land,both the volume fractal dimension and the volume percentage increased with the soil depth;and in soil profile of cropland,both showed the same tendency of increasing with the soil depth,but not monotonously.Soil management had some influence on volume percentage of soil clay and volume fractal dimension.For example,both of them decreased with the rising years of cultivation

Abstract:With the original data as basis,the cultivated land quality in Yidu County,Hubei Province was evaluated with the aid of GIS and the fuzzy matte-relement proximity cluster analysis model.The procedure of the evaluation goes:(1) Use the principal component analysis method to determine factors affecting cultivated land quality;(2) Extract correlatographs with the aid of ArcGIS vectorization,put them under spatial analysis and use the multi-map superimposition method to define evaluation units and extract unit attribute data;(3) Based on membership functions of the evaluation factors,calculate weight coefficients of the evaluation factors and proximity of the evaluation units with the fuzzy matter-element proximity cluster analysis model,and sort the cultivated lands into various quality levels.At the same time,120 samples were collected randomly to verify veracity of the results.The results indicate that the cultivated land in this area is medium in quality and can sorted into 6 levels,account ing for 12.96%,30.37%,31.71%,16.16%,7.14% and 1.66%,respectively,which is roughly in accord with the actual situation.

Abstract:With the aid of GIS(Geographical Information System),remote sensing technology,and the SWAT(Soil and Water Assessment Tool) model developed by the ARS(Agricultural Research Service) of the USDA(United States Department of Agriculture),relevant parameters essent ial to the SWAT model were extracted from Lianshui Basin,Xingguo County,Jiangxi Province,and computer simulation of chemical composition of the runoff in the study area was carried out,Twelve typical subbasins varying sharply in simulation value from 1993 to 2000 were selected for analysis of relationship between land use and simulated chemical composition,using the land use maps of the two time periods.Results show that land use was closely related to translocation rates of organic N,organic P,nitrate N,Soluble P and Mineral P.The findings of the study can be used as technical aid and basis for sustainable development of the agriculture,comprehensive administration and programming of the basin,and realization of agricultural BMPs(Best Management Practices).

Abstract:Polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs) in a typical farmland soil from Yangtze River Delta region were detected by high resolution gas chromatography coupled with high resolution mass spectrometry(HRGC/HRMS).The results showed that averaged total PCDD/Fs concentration in the farmland soil was 2 639 pg g^-1 dw.The isomers of PCDD/Fs covered Cl₄~Cl₈.WHO-TEQ calculation indicated that PCDD/Fs TEQ in the soils ranged from 20.82 to 21.32 pg g^-1 dw,among which 2,3,4,7,8-PCDF and 1,2,3,7,8-PCDD were the two important isomers contributing largely to the total PCDD/Fs TEQ.It is concluded that the farmland soil had been contaminated to some extent with polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs) that were likely released from dismantlement,dissolution and cineration of capacitors in transformer and/or electronic wastes.

Abstract:The comet assay(the alkaline single cell gel electrophoresis) was applied universally in the field of ecotoxicology as a sensitive bioassay to detect DNA damage in the cell level.Little has been reported on its application in assessing effects of mutagens on earthworms in the soil ecosystem.In this paper,earthworms(Eisenia f oetida) were exposed to different levels of mitomycin C and soil samples collected from an area irrigated with wastewater for years.After the exposure,coelomecytes of the earthworms were extracted and subjected to comet assay.The samples were compared in endpoints,such as tail length(TL),tail DNA content(TD) and tail moment(TM).Results show that the utilization of comet assay in combination with vivo exposure of earthworms is a promising tool for evaluation of mutagenic chemicals and polluted soil,and that among the endpoints,TM and TL are more sensitive in representing the dose-effect relationship.

Abstract:Effect of clear-cutting on soil respiration was investigated in a Chinese fir(Cunninghamia lanceolata) plantation in Fujian Province for one year(from February 2003 to January 2004) following clear-cutting.Soil respiration was measured in situ utilizing the alkali sorption technique.During the first 4 months clear-cutting significantly increased soil respiration level,which dropped drastically in the following 6 months,while there was no significant difference in mean soil respiration rates during the study periods between the clear-cut site and the control site(intact site).Respiration rates of forest floor and mineral soils in the clear-cut site were significantly higher than in the control site during the first 5 and 6 months,and there were no significant differences thereafter.Root respiration rate in clea-rcut site declined rapidly and disappeared after the 3 months,and was only significantly higher than in the control site during the first month.The contributions to total CO₂ evolution from forest floor respiration,mineral soil respiration and root respiration in clea-rcutsite were 34.5%,6319% and 116%,and were 231 4%,5011% and 2615% in control site,respectively.Soil temperature and soil moisture together accounted for 54% and 90% of variations of the soil respirations in the clea-rcut and the control sites.Soil respiration and its compartments in the clea-rcut site were lower in temperature sensitivity but higher in moisture sensitivity than in the control site.Q₁₀ values for total soil respiration,mineral soil respiration,and forest floor respiration was 1142,1153,and 1134,respectively,in the cut site and 2142,1181,and 2140,respectively,in the control site.Root respiration of the control site was the highest in Q₁₀ value,being as high as 4.41.

Abstract:To study variations of soil potassium-bearing minerals,Q/I relation and soil capacity of fixing extraneous K,data from 18 long-term stationary field experiments with K treatments and zero K treatment were cited.The results show that (1) readily available K and slowly available K were higher in Treatment NPK than Treatment NP,with the latter being on average 7.67 mg kg^-1 a^-1 higher in hydromica-or smectit-edominated soils.(2) Due to long-term zero K application,crops depleted soil K,thus making hydromica weather and turn into vermiculite.Application of adequate K could defer or stop the process.(3) As a result of long-term zero K application,soil-△K° band AR_e^k were declining while PBC^k ascending,which means that the pool of readily releasable K in soil was getting smaller,K adsorption capacity of the soil higher,and soil K supply capacity lower.A higher rate of K should be applied if K concentration in the soil solution was to be increased.(4) As a result of long-term zero K application,soil K was depleted,which led to strengthened soil K fixation capacity for extraneous K.However,once NH₄⁺-N was accumulated in soil to a certain level,soil K fixation capacity for extraneous K would be reduced.

Abstract:Humic acid and fulvic acid were extracted from evergreen broadleaf forest surface layer soil of the Jingyun Mountains in China.The mechanism of humic acid(HA) and fulvic acid(FA) adsorption by Fe₂O₃、MnO₂ or Al₂O₃ solid sorbent in solution different in pH were studied.The results show that the adsorption increased with the organic carbon concentrations of HA and FA.The adsorption of HA,however,decreased with the rise in pH.When pH remained the same the percentage of HA in the adsorption decreased with the increase in organic carbon concentration of HA.At the same pH,the FA adsorption percentage curves all appeared to be a singlet,and the peaks moved towards low organic carbon concentrations of FA when pH rose.Langumuir equations were adapted to fit the adsorption.It indicated that the max adsorption quantities S_max and adsorption constants K of HA were more than those of FA,while the thermodynamic change in standard free energy of HAΔGm^o was less than that of FA at the same pH.The ΔGm^o of HA and FA were all less than zero,indicating the spontaneous adsorption reactions.

Abstract:Adsorption and redox reactions between As (Ⅲ) and two variable charge soils collected from Guangdong province and Jiangxi province were studied with the batch method.As (Ⅲ) adsorption by the soils increased with the amount of As (Ⅲ) added.The latosol adsorbed more As (Ⅲ) than the red soil did,because the content of iron and aluminum oxides in the former was higher than that in the latter.As (Ⅲ) adsorption by both soils increased with pH.As (Ⅲ) could be oxidized to As (V) by manganese oxides in the latosol,while no appreciable redox reactions with As (Ⅲ) were observed in the red soil.As (Ⅲ) oxidization decreased with increasing pH.The results from desorption of As (Ⅲ) by 1.0 mol L^-1 KNO₃ indicated that the desorption rate of adsorbed As (Ⅲ) was less than 35%,suggesting that most As (Ⅲ) was adsorbed through the formation of inner sphere surface complexes on the soils.The desorpation rate of As (Ⅲ) increased with the pH of the adsorption system in the experiment,indicating that the proportion of outer sphere surface complexes to the total surface complexes increased at higher pH.

Abstract:Chlorophyll content and biomass of plants are usually increased by the addition of certain amount of ammon-i um to the nutrient solution.In order to study the mechanisms of enhanced effects by ammonium on plant growth and chlorophyll content,Chinese cabbage was hydroponically grown in nutrient solutions with six different ratios of NO₃^-:NH₄⁺,i.e.,5.0:0.0,5.0:2.5,5.0:5.0,5.0:7.5,5.0:10.0 and 0.0:5.0.The results obtained were as follows.In the presence of 5 mmol L^-1 nitrate,addition of ammonium(2.5 mmol L^-1) to the solution promoted the biomass and leaf area of Chinese cabbage by 39.6% and 1613% compared with no ammonium addition and the leaf area was significantly correlated with biomass(r=0.941,p< 0.01).There was a significant relationships between ammonium concentration added and SPAD readings,active iron content and chloroplast protein content in the plants with the r values of 0.914,0.954 and 0.964,respectively.The mechanism of the properly enhanced ammonium on biomass was the facilitated expansion of leaf blade,and thus the increased total photosynthet ic area.The facilitated expansion of leaf blade can be attributed to leaf cell division resulting from the enhanced ammonium effect,which should be studied in future.A further study showed that the reason for enhanced ammonium to increase the chlorophyll content was related to the increased reusage of total iron in Chinese cabbage plant,thus increasing the active iron content in leaf blade and chloroplast protein content.

Abstract:Nitrogen release experiments and field experiments were conducted to study release characteristics of the controlled release fertilizer(CRF) coated with hydrophobic material(organic macromolecule polymer) and its effect on rice yield as compared to common urea fertilizer(CUF).The results show that nutrient release of the CRF in water met the requirements for controlled-release.Compared with the CUF,the CRF significantly increased the contents of alkalytic N(ALR-N) and NH₄⁺-N in the paddy soil,facilitating N uptake by the roots of rice.There was no difference in total biomass of the rice plants between the different nitrogen treatments,but the results of two years' field experiments show that the grain yield of the rice in the CRF treatments was 10%~40% greater than that in the CUF treatments.Especially,the CRF,applied at a rate only 1/3 of the rate of the CUF,also increased the grain yield of rice by 15.1% in 2003.Under the local paddy field conditions,the results proved that the nitrogen use efficiency of CRF was up to 51.2% in 2002.The CRF showed its advantages of controlling release of N nutrient,promoting N uptake by the rice,increasing grain yield and nitrogen use efficiency,and reducing nitrogen application rate.

Abstract:Pot experiments in a glasshouse and field experiments were conducted to investigate effects of soil moisture con tent and phosphorus(P) supply on total P uptake by rice cult ivated in aerobic soil.Results showed that soil moisture and P ap plication did not affect significantly total P uptake by rice cultivated in aerobic soil in the field experiment.But in the pot experi ments,P application increased significantly P uptake by the rice plants,though the effect of soil moisture was not significant.A big interaction between soil moisture and P application was founded.And,thus,the highest P uptake by the rice plants was found in the treatment with 0.0300 g kg^-1 of P application rate and 80% in saturated water content.The biggest difference of total P uptake by the rice plants was observed between the application and no application of P under 80% of soil saturated water content and the difference of P uptake by the rice plants between different P application rates was less.Distribution of the P taken up by the rice plants,was in the following order:grain>shoot>root.The results obtained in this experiment could serve as a theoretic basis for water and P management of rice cultivated in aerobic soil in the hilly areas of Southern China.

Abstract:A strain of bacteria with high capability of accumulating poly-P was isolated and screened from soils by using the pure culture and blue and white colored screening methods.Identified as Citrobacter freundii and named GM1,this strain could grow normally in either LB,YG or MOPS media with pH ranging from 6.5 to 8.5.The optimal temperature and pH for its growth were 30℃ and pH 7.5,respectively.After incubation aerobically in the MOPS medium for 24 hours,the phosphorus concentra tion in GM1 reached 11.5% of its weight,while the concentration of phosphate in the medium declined from 43.8 to 14.7 mg L^-1,so the phosphate removing rate was 69%.At that time,poly-P granules could be observed in thalli by the poly-P staining method,indicating that GM1 has a high capability of accumulating phosphate.

Abstract:An investigation was conducted of the alt iplano grassland,which was the important agricultural and animal husbandry base in Tibet.Soil samples with roots,2 kg each,were collected from the rooting-zone of 22 dominant plants at a depth of 2~30 cm and each sample had three replicates.Then the soil samples were ai-rdried,sieved through a 2 mm sieve and stored at 4℃.The root samples were rinsed with tap water,soaked in 10% (w/v) KOH(30 min,90℃),acidified in lactic acid(10 min),and stained with 0.5% trypan-blue.Thirty 0.5 to 1 cm root fragments were examined per sample for their arbuscular mycorrhizal status under a compound microscope(×200).A hundred grams of soil were taken from each sample and wetsieved.Then AMF spores were counted on a grid pattern dish under a binocular stereomicroscope.Spores of AM fungi isolated from the field soil and trap cultures were mounted on glass slides in polyvinyl-lacto-glycerol(PVLG).Then spores examined microscopically and identified according to current taxonomic criteria(Schenck and Prz,1990) and internet information from INVAM(http://invam.caf.wvu.edu).The results show that the invest igation of resources and ecological distribution of arbuscular mycorrhizal fungi(AMF) were contributive to the study on diversity of AM fungi in the alt iplano grassland in Tibet.Five genera of AM fungi were collected and identified in the sampled soils.In terms of spore density,isolation frequency,relative abundance and importance value,they were in the order of Glomus>Acaulospora>Gigaspora>Scutellospora>Entrophospora.Glomus,but they all were of prominent genus in the investigation area and Acaulospora,Gigaspora and Scutellospora were of common genus while Entrophospora was rarely found.The appearance and distribution of AMF are related to regional difference,soil factors and plant hosts.Among the five genera,Gigaspora,Glomus and Acaulospora were distributed widely in the target areas,while Scutellospora and Entrophospora were only found in altiplano grassland.The diversity character was similar in most areas,only Acaulospora appeared more frequently in frigid meadow.Under different meadow types and soil texture,the diversity of AM fungi was in the trend of frigid meadow>upland brushy grassland>meadow,and loam>sandy loam and heavy sandy soil> light sandy soil.AM fungi were the commonest in the soil with pH in the level of 6.0~6.7,olsen P in 5.3~13.8 mg kg^-1 and organic matter in 35.7~54.6 g kg^-1.AM fungi colonized well in the plants of Carex praecpara,Kobresia humilis and Cyperus compressus,but not in Fagopyrum esculentum.Tamarix chinensis and Salsola nepalensis,commonly recognized as good host,were not colonized,either.It was also found soil pH was positively correlative to spore density,but not to colonization.

Abstract:A field experiment was conducted to study effects of fertilizer combination on yield,quality and forms of nutrients in leaf of lettuce.The results show that yield of lettuce was significantly increased(135.8% ~177.0% ) by balanced application of secondary-and micro-nutrient fertilizer and organic fertilizer in addition to N application at the same rate in CK.In terms of yield increment,the treatments were in the sequence of NP₁K₂MgZnB>NP₂K₂>NP₁K₂RM>NP₁K₂PP>NP₁K₂Mg>NP₁K₂>NP₂K₁.Nitrate contents of lettuce were reduced in all treatments.It was the most significant in Treatment NP₁K₂MgZnB and the least in Treatment NP₂K₂ in leaf,and the most in Treatment NP₁K₂RM and the least in Treatment NP₂K₂ in stem.Quality of the lettuce was improved in all the treatments and the most in Treatment NP₁K₂RM.In terms of forms of nutrients in the plant,protein-N,non-protein-P and non-protein-K dominate,respectively,in the lettuce leaf.Effects of fertilizer combination on forms of N and P nutrients in the leaf of lettuce differed from treatment to treatment but the effects of raising contents of the three forms of potassium were similar.Among the forms of nutrients,only non-protein-N showed a significantly negative correlat ion with nitrate in the stem of lettuce,but a positive one with Vc content in the stem and amino acid content in the leaf,non-protein-P showed a significantly negative correlation with Vc in the leaf and amino acid in the stem,and non-protein K and total K showed a significantly negative correlation with nitrate in the leaf but a positive one with Vc contents in the stem and leaf and amino acid in stem.Protein K showed a significantly negative correlation with nitrate in the stem,but a positive one with Vc and amino acid in the stem and leaf.

Abstract:Cobalt,iron,and selenium in rocks,soils,and forage plants,of six background zones different in geology in the major ruminant product ion base of Yunnan were determined and analyzed.Results show that in terms of abundance of cobalt,iron,and selenium in soil and forage,the Paleozoic Basalt Zone(Ⅴ) and Carbonate Red Earth Zone(Ⅰ),are at the top,the Yellow Red Earth Zone of mixed of Carbonate,Clastic Rock and Basalt(Ⅱ) in the middle and the Purple Earth Zone of Mesozoic Clastic Rock(Ⅲ),the Yellow Red Earth Zone of Clastic Rock(Ⅳ),and the Dark Red Earth Zone of Precambrian Metamorphic Rock(Ⅵ),at the bottom.The concentrations of cobalt,iron,and selenium in forages are affected by the geological background values,especially abundances of these microelements in the soil.

Abstract:A general introduction is given to trend of the research in the world on soil quality guidelines/standards,and the principle as well as application function,and several suggestions for amendment of the existing soil environmental quality standards in China.Derivation of risk-based soil quality guidelines/standards has been an international trend,which takes into consideration land uses,and settings of generic exposure pathways,exposure scenario(e.g.exposure period and frequency) and critical receptors associated with various types of land uses.Risk-based soil quality guidelines/standards are mostly applied to risk management,serving as crit ical values for identification of contaminated sites/soils.To amend the existing soil environmental quality standards in China,it is essential to take into consideration function and objectives of the standards,methodologies,land uses,effect of the transport of soil contaminants on other environmental media,and categories of soil contaminants.The standards are to be amended to set up "soil environmental and healthy quality guidelines/standards" for protection of the ecology and human health,which will serve for risk identification and comprehensive management of contaminated sites,and meanwhile to set up "soil native quality guidelines/standards" for protection of soil resource.

Abstract:国外利用卫星遥感进行土壤盐渍化研究始于20世纪70年代,至90年代以来一直以目视判读为主,Bao^[1]作了盐渍土光谱特征的专门研究,发现土壤盐渍化程度越高,光谱反射越强;在红光和绿光波段,地表植被覆盖影响盐渍土的光谱反应;土壤含水量也会影响盐渍土的光谱响应模式.骆玉霞等^[2]对盐渍土遥感信息单要素分类与遥感信息地理信息综合分类进行了比较研究.新疆是我国干旱的内陆盐渍土分布区,其中以塔里木盆地最多.

Abstract:土壤风蚀是形成沙尘暴导致土壤沙漠化的主要原因,它能够降低耕作层的保水性能和抗蚀能力,导致土壤肥力和生物生产量的下降,影响农业的可持续发展,对人类生存环境造成不同程度的危害^[1].土壤风蚀是一个复杂的物理过程,其根源除了严酷的自然气候外,有94.5%是人为掠夺式经营方式所致^[2].科学家研究了风吹情况下土粒的运动,发现能被风吹到高空,运移千里之外的主要是土粒直径70μm以下的微粒或浮尘,微粒主要存在于耕作的农田和草地.沙漠经过多年风蚀,已经没有多少微粒存留下来^[3],由于人类不合理翻耕土地、放牧和樵采等活动造成大量疏松裸露的土地,为沙尘暴的发生提供了沙尘源,沙漠化面积不断扩大.

Abstract:土壤酶是土壤生物学活性的重要组成部分,它催化有机物的矿化释放无机养分,参与土壤腐殖物质的分解形成,反映了土壤各种生物化学过程的动向和强度;其活性与土壤的理化性质和其他生物学特征紧密相关,且有易于测定的优点,是近年来土壤质量评估工作中必不可少的内容^[1].土壤酶一直受到红壤研究者们的重视^[2,3],但这些研究涉及的酶的种类较少,近年来国外相关文献中的一些常见的酶,如葡糖苷酶、荧光素水解酶、芳基硫酸酯酶等^[4~6]鲜见报道;也没有回答在长期不同施肥管理条件下,红壤中酶活性的综合水平特点和土壤酶动力学特征的差异等问题.本文的工作则针对上述问题开展研究,以期为合理化提高红壤肥力的施肥措施提供理论依据.

Abstract:土壤环境的优劣决定着我国未来农业的可持续性发展,同时也深刻地影响着动物和人类的健康.土壤动物作为土壤污染程度的指示生物已成为国际土壤生态学领域研究中的热点问题^[1,2],对土壤动物作为土壤质量表征的研究目前仍处在开展阶段^[3].有机氯农药化学性质稳定,残留时间长,脂溶性强,且利用率低而对农业生态环境造成严重的污染^[4].此前已有文献讨论有机氯农药与土壤的关系^[5~7],土壤动物对重金属污染的反应^[8],但是从生物多样性的角度调查有机农药污染的相关文献较少.

Abstract:我国随着水危机、水土流失、干旱及土壤障碍等问题逐年增加,各种先进的节水增产增效技术陆续引进我国,应用液态地膜就是其中被看好的具有较好的增温保墒护土促苗和增产前景的技术之一.特别是1979年以来随着我国地膜栽培技术大面积推广,同时引发出严重的“白色污染”问题,人们对应用液态地膜的兴趣也在不断增加.自1986年中比科技合作开始,由中国农业科学院土壤肥料研究所率先从比利时Labofina公司引进BIT产品,先后在山东、河北、北京、山西、陕西、宁夏、新疆等地在农业粮、经、饲草等作物上进行试验研究,尤其在我国北方干旱半干旱以及水土流失严重地区土壤上应用,对液态地膜改土、保墒、增温、增产、减少水土流失效果给予了肯定^[1~5],进而推动了液态地膜国产化生 产和开发.

Abstract:农作物的秸秆既含有相当数量的作物必需的碳、氮、磷、钾等营养元素,又具有改善土壤的理化性状和生物学性状、提高土壤肥力等作用^[1].土壤微生物是土壤的重要成分,通过它们的代谢活动,转化土壤中各种物质的形态,是构成土壤肥力的重要因素.土壤微生物控制着土壤生态系统的许多过程,行使的功能包括:有机物料的分解,土壤化学循环,土壤结构的形成,污染物的脱毒等.土壤微生物群体的改变可以作为预示土壤变化的指标^[2].近年来,在各种自然、人为因素的影响下,西藏中部地区农田土壤退化严重,农业可持续发展面临严重挑战.

Abstract:我国热带和南亚热带地区(简称热区)光热水资源十分丰富,在农业综合开发上,应重点发展经济价值高、适于山地丘陵种植的外向型名特优水果,如龙眼、荔枝等^[1].龙眼是原产华南地区的名贵水果,其生产分布受自然条件影响很大,我国乃至世界适宜龙眼生产的范围不大,我国龙眼的主产区分布在福建和台湾^[2].长期以来我国龙眼产量较不稳定,气候条件的影响是重要原因,但迄今有关气候因素与龙眼产量关系的研究尚未能较为准确地揭示其间的变化关系^[3],同时现有关于龙眼适种地分布的研究也多为基于单一气候因素,而用综合指标遴选龙眼适种地的研究鲜见报道.