新疆叶尔羌河流域土壤盐渍化特征研究

以新疆叶尔羌河流域为例,分析了该地区土壤盐渍化的类型、程度、特征、成因以及与地下水埋深的关系。盐渍化程度分析为该区农业发展提供了科学依据;3种土壤盐分组成剖面涵盖了新疆地区典型的土壤盐化类型,为提出针对性的解决方案提供可靠保证;剖析了土壤盐渍化成因及与地下水埋深的关系,指出控制土壤盐分的关键是合理的淋洗与排水、建立明渠排水与竖井排灌相结合的灌溉方式。为新疆及其他类似地区评价与解决土壤盐渍化问题提供了新思路。     

宁夏引黄灌区日光温室集约种植区浅层地下水硝态氮含量与耕层土壤硝态氮含量的关系

  目的  探讨宁夏引黄灌区日光温室集约种植区地下水硝态氮污染现状及其与土壤硝态氮含量之间的关系,为有效防治地下水硝态氮污染及土壤盐渍化提供理论依据。  方法  通过抽样调查方法,采集7个典型日光温室集约种植区不同时期的214个地下水样及102个0 ~ 20 cm土壤样品,分析了地下水和土壤的硝态氮含量及电导率等。  结果  地下水样本硝态氮含量超过Ⅲ类水标准的达53.3%;近80%的土壤样本呈现出不同程度的盐渍化,其中中度盐化土占57%。当地下水硝态氮含量大于40 mg L?1时,地下水电导率、土壤电导率和土壤硝态氮含量均随地下水硝态氮浓度增加而急剧增加。土壤电导率与土壤硝态氮含量之间呈极显著线性函数关系,决定系数达0.376。土壤硝态氮含量与地下水硝态氮含量之间呈极显著的指数函数关系,土壤电导率与地下水电导率之间呈极显著的线性函数关系。  结论  宁夏典型日光温室集约种植区的地下水硝态氮污染和次生盐渍化严重,并与土壤硝态氮含量和盐渍化密切相关。     

均质土壤毛管水上升特性室内试验研究

针对西北地区因过量灌溉而引起的土壤盐渍化问题，通过室内模拟土柱试验,对地下水埋深较浅(仅为地面以下70 cm)的均质土上升毛管水运动特性进行了研究，分析了毛管水上升高度、地下水毛管补给量与时间之间的关系，以及毛管水上升高度与地下水补给量之间的关系，探明了地下水毛管上升的运动机理。结果表明，均质土壤毛管水上升高度和地下水补给量与时间之间均为幂函数关系，毛管水上升高度与地下水毛管补给量之间呈明显的线性关系。     

黄河三角洲土壤盐渍化与地下水特征关系研究

为研究黄河三角洲表层土壤盐分含量与地下水特征的关系,对研究区内土壤盐分含量及地下水进行原位监测,分析土壤盐渍化和地下水特征,并运用灰色关联分析法对地下水埋深、电导率、p H和主要离子含量的关系进行定量分析。结果表明:土壤表层盐分含量均值为3.90~6.31 g kg-1,表层以下土壤盐分含量均值为2.54~3.44 g kg-1,属于中度及以上盐渍化程度;地下水埋深平均值为1.16~1.71 m,普遍较浅;地下水阴离子以Cl-为主,阳离子以Na+为主,两者分别占阴、阳离子总量的比例约为65%。关联分析表明,不同地下水特征指标与土壤表层盐分含量的密切程度不同,同一特征指标与土壤表层盐分含量的密切程度在不同时期间差异显著,总体而言,土壤表层积盐与地下水电导率、Na+、Cl-的关系较为密切,与p H、CO32-和HCO3-之间的关系较弱。在防治土壤盐渍化中,应当加强对地下水电导率、Na+、Cl-的控制与管理。     

苏北海涂典型围垦区土壤盐渍化风险评估研究

为定量评估制约苏北海涂土壤资源开发利用的盐渍障碍因素,以苏北海涂典型围垦区江苏省大丰市金海农场为例,将灰色系统理论应用于风险评价,构建了实用的生态风险评价数学模型、指标体系与评价流程,并对区域土壤盐渍化风险状况进行了定量评估与分级。结果表明:土壤盐分、表土层容重与地下水矿化度是该区域盐渍化风险评估的重要因素;研究区土壤盐渍化风险总体较高且不同部位差异较大,其生态风险值F介于0.12～0.60之间,平均值达0.30;盐渍化风险分布表现出与土壤盐分、地下水矿化度较为相似的空间规律;受种植制度与耕作措施差异的影响,研究区东部水稻田盐渍化风险总体高于西部棉花地;研究区域不存在土壤盐渍化较小风险区,以一般风险、较大风险为主,其中较大风险区占总面积的50.11%,一般风险区占49.41%,很大风险区仅占0.48%,一般风险和较大风险区是该区土壤改良治理的重点区域。该结果可为海涂区中、低产地的质量提升、盐渍化土壤的科学改良与田间管理提供参考依据。     

开都河流域下游绿洲土壤盐渍化影响因子分析

以开都河流域下游绿洲为例,应用灰色关联度方法分析了6种影响因子在土地盐渍化过程的相对影响力大小。结果表明:自然和人为因素共同作用于研究区土壤盐渍化过程。土壤含盐量与土壤盐渍化影响因子之间的关联度排序0—10cm层为:地下水埋深最近排水渠距离高程最近灌溉水渠距离最近湖岸距离地下水矿化度;10—30cm层为:地下水埋深最近湖岸距离最近排水渠距离高程最近灌溉水渠距离地下水矿化度;30—50cm层:最近灌水渠距离地下水埋深最近排水渠距离地下水矿化度最近湖岸距离高程。在3个不同土层深度上土壤盐渍化影响因子的影响力不同,土壤盐渍化防治需要综合考虑多种影响因子的作用。     

盐渍土地区地下水矿化度的分层测定法

在盐渍土地区,地下水矿化度与土壤盐渍化有密切的关系。因此,探讨地下水及其盐分变化规律是改良利用盐渍土的重要任务之一。     

河北曲周盐渍土区土壤元素特征

研究了地处华北冲积平原的曲周盐渍土区土壤元素全量 (ST)、1∶1浸出液(SE)和土壤溶液 (SS)中各元素的浓度范围和特征 ,及其与地下水中元素的联系。土壤元素全量主要与土壤质地 (反映了矿物组成 )有关 ,只有盐渍化严重的土壤 ,易溶性元素对其全量的增加有一定影响。元素在土壤溶液和 1∶1浸出液中的浓度差异受土壤水分状况的影响。各土层元素在SE中的含量占全量的百分率 ,其平均值和变异系数在一定程度上说明了该元素的可溶性和移动性。土壤—地下水系统中 1m和 2m土层的大部分元素在 1∶1浸出液中的浓度平均值与地下水矿化度和与地下水中相应元素的浓度值之间呈显著或极显著相关 ,无相关关系的元素 ,大多属迁移系数较小的元素。文中还以例说明了不同盐渍化程度土壤 1∶1浸出液中元素浓度垂直剖面特征 ,以及与地下水中相应元素浓度的联系。     

青海黄河沿岸农田土壤盐渍化成因及改良途径

青海省黄河上游沿岸农田的　土壤盐渍化，已成为该区农业发展的严重限制因素．研究主要选择了盐渍化严重的黄河上游　龙羊峡库区的农田．该区农田土壤为氯化物－硫酸盐盐土；土壤剖面盐分分布为两种类型，即　盐分表面聚集型和通体含盐型．土壤盐渍化成因主要有气候、灌溉水矿化度、土壤母质、灌溉制度和地形．当地土壤盐渍化的解决途径主要是生物措施，相应地配合水利与造林等工程　措施．     

塔里木沙漠公路防护林咸水灌溉土壤盐渍化状况研究

为了研究塔里木沙漠公路防护林建林后土壤在咸水灌溉条件下的盐渍化状态,本文结合防护林建林前土壤普查资料土壤的盐分状况,运用统计分析、相关性分析及灰色关联分析,对防护林沿线的40个监测点的土壤盐离子、土壤盐渍化的现状及驱动力作了初步研究。研究结果表明：塔里木沙漠公路防护林建成后,土壤盐分各离子含量均较建成前有了显著增加。其中,阳离子含量Na K ＞Mg2 ＞Ca2 ,阴离子含量Cl-＞CO32-＞SO42-＞HCO3-;防护林沿线土壤盐渍化类型以氯化物型与硫酸盐-氯化物型为主,分别占到监测点的84.2%与15.8%;对土壤盐渍化程度的研究表明：有近81.6%的监测点已达到中度盐渍化程度;灰色关联分析结果表明：引起塔里木沙漠公路防护林土壤盐渍化的主要驱动力依次是灌溉年限、地下水矿化度,地下水pH和地下水埋深。     

“绿色革命”以来大气CO2浓度升高对C3作物营养品质的影响

自20世纪60年代"绿色革命"以来,育种技术和农耕技术的发展促进了农作物产量的大幅提升,然而作物的营养品质出现下降趋势。在相似的遗传背景下,大气CO_2浓度升高会使单位体积农作物产品的营养元素含量下降,因此"绿色革命"至今,农作物产品的营养元素下降可能受大气CO_2浓度升高影响。通过植物生长箱模拟"绿色革命"初期和目前的大气CO_2浓度水平(310μmol/mol和400μmol/mol),针对主要C_3作物水稻、小麦和大豆,研究"绿色革命"以来大气CO_2浓度升高对其籽粒的C、N、Fe、Zn元素含量的影响,结果表明:CO_2浓度升高对3种作物籽粒的C元素含量几乎没有影响,变化幅度在±1.5%之间;籽粒的N、Fe、Zn元素含量普遍呈现下降趋势,但均未达到显著水平。     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.     

Collection and preliminary evaluation of native turfgrass accessions in Italy

Despite a raising interest on turfs in Italy, all theavailable varieties of this kind in the Country are of foreign origin, and areoften poorly adapted to the prevailing climatic conditions. This prompted tobegin a collection activity of indigenous turfgrass species, with the ultimategoal of identifying promising materials for future breeding based on localgenetic resources. The collection was carried out in three areas of Italy, viz.the northern Po Plain, the coastal region of Liguria, and the island of Sardiniathat are characterised, respectively, by subcontinental, warm temperate, andtypical Mediterranean climate. Altogether, 141 sites were visited, yielding 226accessions belonging to eight species of potential interest for turfs:Poa pratensis, Poa trivialis,Festuca rubra, Festuca arundinacea,Lolium perenne, Agrostis stolonifera,Agrostis tenuis, and Cynodon dactylon,this last being a warm-season grass. Poa pratensis andCynodon dactylon were mostly collected in northern Italyand Sardinia, respectively, whereas Festuca arundinacea andLolium perenne were rather ubiquitous. The collection sitesranged from 0 to 1040 m asl, but sites over 750 m wereonly visited in the inner part of Sardinia. All the accessions, collected aswhole plants, were transplanted at Lodi, northern Italy, where they are beingevaluated. Their preliminary evaluation for traits of importance for turf use,such as sward colour and overall quality, highlighted the great variation andthe occurrence of interesting accessions in all species. Other characters wererecorded, bearing specific importance in individual species, and in all casespromising accessions were identified. The germplasm of Festucarubra, Festuca arundinacea, and Loliumperenne proved highly infected by endophytic (symbiotic) fungi of thegenus Neotyphodium.     

Karyotypic and genome size variation in Cajanus cajan (L.) Millsp. (pigeonpea) and some wild relatives

Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value.     

Effect of some fungicide seed treatments on the survival of Bradyrhizobium japonicum and on the nodulation and yield of soybean [Glycine max. (L) Merr.]

Several commercial fungicide seed treatments were evaluated for their possible effect on the survival of Bradyrhizobium japonicum on seeds and on the nodulation and yield of soybeans in a greenhouse and a field experiment. quinolate Pro (carbendazim and oxine copper), Vitavax 200FF (carboxin and thiram), and Monceren (pencycuron) had a small effect or no effect on the survival of B. japonicum and on the nodulation and yield of soybeans. They can thus be considered compatible with soybean seed inoculation. Germipro UFB (carbendazim and iprodione), Apron 35J (metalaxyl), and Tachigaren (hymexazol) decreased B. japonicum survival and the nodulation and yield of soybeans and thus cannot be considered compatible with soybean seed inoculation.     

Leaf position and genotype differences for mineral element concentrations in sorghum grown on tropical acid soil 1

Mineral element deficiencies and toxicities are common problems associated with sorghum [Sorghum bicolor (L.) Moench] production on acid soils. To better understand some of the mineral element problems and the analysis of plant tissue of sorghum plants grown on acid soils, four sorghum genotypes were grown on an acid Oxisol at Carimagua, Colombia limed with dolomite at 2 and 6 Mg ha^‐1.

Samples for mineral element analyses were obtained from leaves at different positions on the four genotypes. Concentrations of P and Mg were highest in the flag leaf (Leaf No. 1) and decreased as the position on the plant declined from the top of the plant for plants grown at 2 Mg lime ha^‐1. Similar decreases in P, Mg, K, and Zn concentrations occurred in plants grown with 6 Mg lime ha^‐1. Concentrations of Ca, S, Si, Mn, Fe, Cu, and Al increased as leaf position declined from the flag leaf for plants grown at 2 and 6 Mg lime ha^‐1. The higher lime supply enhanced Ca and reduced Mn and Fe concentrations in leaves. Differences in mineral element concentrations for the four genotypes used were fairly extensive. The elements to show the greatest range among genotypes were Al and Si and the elements to show the least range among genotypes were P, K, and S. Care should be used in collecting leaf samples for plant analysis and genotypic differences for accumulation of mineral elements should be considered in interpretation of results.