中国天眼工程周边地区土地利用时空演变与生态环境效应

[目的] 分析FAST （中国天眼）工程周边的贵州省平塘县、惠水县、罗甸县的土地利用类型和空间变化,探讨土地利用变化与生态环境的关系,为FAST工程周边的生态环境保护和改善提供科学参考。[方法] 以2000,2005,2010,2013和2017年5期TM遥感影像数据为基础,运用RS和GIS技术解译遥感影像数据获取惠水县、罗甸县、平塘县“三生”空间的土地利用数据,计算区域生态环境质量指数及其生态贡献率,分析研究区近20 a土地利用功能演变特征及区域生态环境响应状况。[结果] ①FAST周边林地面积比例最大,但呈减少的趋势。研究区土地利用面积表现为：生态用地>生产用地>生活用地,但生活和生产用地面积增加,分别由1 661.74和12.84 km²增加到1 674.07和25.66 km²,生态用地面积则由6 610.55 km²减少到6 590.86 km²。②FAST工程建设加速土地利用类型的转变,促使FAST周边林地生态用地、草地生态用地、农业生产用地、水域生态用地相互转换,其中林地生态用地的转出面积最大,占转出面积的46.14%。③FAST周边的生态环境质量指数由0.471 0下降到0.468 1,生态环境呈现下降的趋势,FAST周边的发展促使高生态环境土地利用转向低生态环境土地利用类型。[结论] FAST周边的生态环境与土地利用变化存在耦合关系,生态环境质量随生态用地向生产、生活用地转变呈现下降趋势。提高FAST周边生态用地质量,有助于FAST工程的安全运行。     

生态工程对科尔沁沙地主要生态服务功能的影响

[目的] 研究生态工程实施下科尔沁沙地主要生态服务功能的变化特征,为该区今后生态保护建设提供科学依据。[方法] 运用已有的生态服务评估方法定量评估了2001—2018年科尔沁沙地固碳量、水源涵养及水土保持服务功能的时空变化情况。[结果] ①科尔沁沙地土地利用类型主要以耕地、林地和草地为主,生态工程实施期间,林地、耕地面积分别增加8 448 km²,3 280 km²,草地面积减少12 639 km²; ②科尔沁沙地固碳量稳步增长,林地和耕地的固碳量均增加,草地的固碳量减小,但草地固碳量依然最高; ③科尔沁沙地水源涵养量呈先增加后略微减少的趋势,所有土地类型中林地水源涵养量持续升高; ④科尔沁沙地水土保持量持续上升,约增加1.38×10⁷ t,林地水土保持量增加最显著。受地势的影响,区域水土保持总量呈西高东低的分布特征。[结论] 科尔沁沙地生态工程建设效果良好,创造了显著的生态效益。     

辽宁省抚顺市2000-2020年土地利用格局变化与生态环境效应

[目的] 探讨辽宁省抚顺市退耕还林以来土地利用格局时空变化特征及生态环境效应,揭示土地利用格局变化对环境的影响,为该区土地利用结构优化提供科学依据。[方法] 以2000,2010和2020年3期遥感影像为基础数据,通过土地利用动态度、土地利用程度综合指数、土地利用转移矩阵、NDVI差值分析、区域生态环境质量指数等方法定量分析抚顺市土地利用格局时空变化特征及生态环境效应。[结果] ①2000—2020年研究区各种土地类型存在相互转化的关系,其中林地和耕地变化较为明显。20 a间,耕地面积减少825.59 km²,增长率-7.32%;林地面积增加591.14 km²,增长率5.24%;城镇用地面积增加182.36 km²,增长率1.62%; ②2000,2010和2020年研究区土地利用程度综合指数分别为224.48,225.57和226.12,同比增长0.49%和0.24%,研究区土地开发利用强度缓慢上升; ③研究区20 a间植被覆盖整体呈上升趋势,NDVI减少的区域与城镇用地的扩张区域基本重合; ④3个时期土地利用类型转化的生态环境质量指数分别为0.744 8,0.775 4和0.782 6,10 a间环境质量生态指数分别上升4.11%和0.93%,环境质量整体呈上升趋势。[结论] 20 a间研究区快速推进城镇化进程的同时环境质量整体向好,局部范围内生态环境质量改善与恶化并存。城镇用地、耕地、林地之间的转化为主要原因,退耕还林等环境保护政策使研究区环境质量不断上升,但随着时间的推移,上升趋势趋于平缓。     

广东省1980-2018年“三生”用地转型对生态环境质量的影响

[目的] 研究基于格网单元的广东省“三生”用地转型对生态环境质量的影响,为区域生态、经济协调发展提供科学依据。[方法] 基于广东省8期土地利用现状遥感监测数据和“三生”土地利用主导功能分类体系,对该区“三生”用地转型特征及生态环境质量进行定量研究。[结果] ①1980—2018年,广东省农业生产用地面积大幅减少,共减少了5 369.61 km²,城镇生活用地、工矿生产用地面积大幅增加,分别增加了4 526.02 km²,2 406.93 km²,农业生产用地和林地生态用地间转换现象明显。②“三生”用地空间转型主要表现为工矿生产用地、林地生态用地中心逐渐靠近广东省几何中心,农业生产用地、城镇生活用地中心逐渐远离几何中心。③广东省生态环境质量指数从1980年0.648 1降至2018年的0.641 4,生态环境质量空间分异明显,呈现“沿海低—内陆高”的分布特点。④Getis-Ord G_i^*指数表明,生态环境质量变化热点区域集中在粤东西北地区,冷点区域多位于珠江三角洲地区。⑤广东省生态环境存在改善和恶化两种趋势。[结论] 建议充分考虑区域自然条件、功能定位以及导致生态环境变化的主导因素,制定土地政策措施,实现土地利用方式创新,更好地推动广东省区域均衡发展。     

海南岛海岸带土地利用变化及其对碳储量时空演变的影响

[目的] 预测未来土地利用/覆盖变化(land use and land cover change,LULCC)及其对生态系统碳储量的影响,为区域土地利用决策和碳管理提供科学依据。[方法] 基于30 m分辨率的海南岛1990,2000,2010,2020年土地利用遥感解译数据,运用ArcGIS与InVEST模型,探究土地利用时空演变及碳储量响应状况,并引入GeoSOS-FLUS模型预测研究区2030年土地利用多情景变化特征及其对未来不同情景下生态系统碳储量的影响机制。[结果] ①1990—2020年研究区耕地、林地、草地和未利用地面积减少,水域和建设用地面积增加。未利用地和耕地面积持续减少,建设用地面积持续增加。②30 a间LULCC导致区域碳储量持续减少,达到1.50×10⁶ t且年变化率为5.00×10⁴ t/a。建设用地的大肆扩张及林地退化是导致碳储量下降的重要原因,“未利用地→草地”为碳储量增加中最明显的图谱变化,“草地→林地(人工林地)”是碳储量减少中最显著的图谱变化。③2020—2030年的3种预测情景中,林地仅在生态优先情景下得到了有效保护,且面积增加了11.91 km²。建设用地在3种预测情景中均呈现不同程度扩张态势,且发展优先情景涨幅最大。[结论] 海南岛大面积高碳密度的天然草地转换为低碳密度的人工林地,高碳区转变为低碳区,区域固碳能力削弱。应采取提高林地、草地等地类比重等一系列的土地利用调控政策,加大区域碳源向碳汇转换的优化发展。     

基于“三生”空间的重庆市土地利用演变与城镇化关系研究

[目的] 分析重庆市土地利用时空演变规律,探究土地利用转型及景观格局响应的演变特征与城镇化的关系,为重庆市"三生"土地规划与城镇化可持续发展提供数据支持。[方法] 基于"三生空间"功能分类的视角构建用地分类标准,利用2000,2010,2020年土地遥感影像和夜间灯光数据,采用转移矩阵、相关性分析及回归分析法进行分析。[结果] ①2000-2020年重庆市生产、生态空间总体减少,生活空间持续扩张。2000-2010年,生产、生态空间减少191.87,252.95 km²,生活空间增大446.03 km²;2010-2020年,生产空间面积减少13.76 km²,生态空间减少324.05 km²,生活空间增大314.87 km²。②重庆市生产功能向生活功能转化较为明显。随着城镇化加强,生态空间转向生产空间显著,功能转变明显聚集于重庆市中心区域。③重庆市空间景观破碎度减小,景观复杂度逐渐提高,林草水生态空间占据主导优势。④2000-2010,2010-2020年土地利用面积变化对夜间灯光值的影响存在差异;2000年,城镇生活空间、农村生活空间变化对夜间灯光变化影响起主导作用,而2020年工业生产空间、城镇生活空间变化对夜间灯光变化影响较强。[结论] 重庆市各类空间发生相互转换,利用不同"三生"空间类型变化和城镇化的关系,推动土地规划与城镇化协调发展。     

抚仙湖流域生态用地时空演变及其驱动因素

[目的] 研究生态用地时空演变规律及形成机制，为维持区域生态平衡和保障生态文明建设提供科学参考。[方法] 运用土地利用变化幅度、洛伦兹曲线、基尼系数、回归分析及GIS技术等方法，分析2010-2018年抚仙湖流域生态用地时空演变特征及其形成机理。[结果] ①抚仙湖流域生态用地以耕地、林地和水域及水利设施用地为主。8 a来，耕地面积减少5.15 km²，林地面积减少1.94 km²，草地面积减少0.81 km²，园地面积减少0.19 km²，其他土地面积减少1.40 km²，水域及水利设施用地面积增加0.03 km²。②流域各种生态用地空间分布差异较大，耕地、林地空间分布较均匀，洛伦兹曲线比较靠近绝对均匀线，基尼系数居0~0.25之间。草地、园地、水域及水利设施用地和其他土地分布相对集中，洛伦兹曲线下凹程度较大，基尼系数多处于0.5之上。生态用地空间分布不均的趋势有所加强。③从驱动机制来看，导致流域生态用地时空变化的主要驱动因素为人口密度、城镇化水平、政策、到主要公路距离、到水域距离、到城镇建成区距离。[结论] 研究时段内，抚仙湖流域生态用地时空变化较显著，其变化是自然条件、社会经济条件及空间区位条件多种因素协同作用的结果。     

1980—2020年内蒙古自治区通辽市土地利用变化及其驱动力

[目的] 分析内蒙古通辽市土地利用变化及其驱动力,为该地区经济建设、土地可持续发展提供科学依据。[方法] 基于通辽市1980—2020年8期土地利用数据及统计年鉴数据,采用土地利用动态度、土地利用程度、土地利用转移矩阵和主成分分析方法对通辽市土地利用变化特征及其驱动力进行研究分析。[结果] 通辽市1980—2020年土地利用以耕地和草地为主,耕地总面积增加了3 037 km²,整体增幅为20.48%,草地总面积减少了2 922 km²,整体减幅为10.40%。建设用地面积在40 a间持续增加,其单一土地利用动态度最大。土地利用程度综合指数处在中低等水平,由于研究期间综合指数变化率为正值,整体上处于上升发展期。研究期间内草地主要转化为耕地、林地、建设用地及未利用土地。通辽市土地利用变化的社会经济驱动力以经济发展水平、农业发展水平、社会富裕程度和产业结构为主,人口的影响次之。气候驱动因素方面主要是年平均气温和年降水量的影响较为显著。[结论] 1980—2020年通辽市土地利用空间上存在明显异质性,土地利用变化速度趋于稳定,土地利用水平不断提高,土地利用转换愈加频繁,社会经济和气候因素对土地利用变化有正向显著作用,整体上不断促进该地区经济建设和土地可持续发展。     

2000-2019年青海省同仁市NDVI时空动态变化

[目的] 研究地处黄土高原最西端,与青藏高原接壤的青海省同仁市植被时空动态变化,为黄土高原与青藏高原过渡地带的生态保护和治理提供参考。[方法] 基于MODIS-NDVI数据,采用线性趋势回归、Hurst指数,从时间和空间尺度分析了同仁市2000—2019年NDVI动态变化特征,对NDVI与土地利用和海拔高度的关系进行初步分析,并对NDVI未来变化趋势进行预测。[结果] ①2000—2019年同仁市NDVI整体呈波动上升趋势,平均增速为0.027/10 a。NDVI高值区域增加明显,主要分布在东西部山区,NDVI值介于0.8～1的区域由2000年的388.63 km²增加到2019年的1 066.92 km²。②NDVI上升的区域为2 925.21 km²,占全市面积的84.42%,广泛分布在隆务河谷地区和周围山区,其中林地626.13 km²,草地2094.11 km²。③NDVI值下降的区域为539.79 km²,占全市面积的15.58%,少部分分布在隆务河河谷地区,大部分在西部和南部山区。以同仁市冻融侵蚀海拔下限3 583 m为界,海拔3 583 m以上区域NDVI下降的面积占全市NDVI下降总面积的70.93%。④未来NDVI值持续上升的区域占全市面积的79.17%,持续下降的区域占13.13%。[结论] 过去20 a,同仁市NDVI整体上升,高覆盖度植被面积明显增加,NDVI下降区域主要分布在高海拔地区。未来同仁市NDVI整体上将持续上升,但仍有部分区域存在下降趋势。     

马来西亚吉隆坡市土地利用变化特征分析与预测

[目的] 揭示快速城市化过程中港口城市土地利用景观格局变化规律，为当地编制土地利用规划提供科学依据。[方法] 以马来西亚吉隆坡市2000，2005，2010，2015，2020年5期遥感影像为基础数据，基于交互式数据语言（IDL），采用指数分类法提取土地利用信息，并应用RS，GIS技术和景观生态学方法对吉隆坡市2000—2020年土地利用景观格局变化进行研究，最后采用灰色预测模型预测2025年吉隆坡市土地利用数据。[结果] 2000—2020年吉隆坡市种植园和林地大幅减少，建设用地迅速增加，港口与城市圈中部区域种植园主要转化为建设用地；土地利用景观形状趋于复杂化、不规则化，景观类型空间连通性降低，景观异质性增强；2025年吉隆坡市建设用地和种植园面积分别为1 624.12 km²和2 216.99 km²，与往年相比，建设用地增加，种植园减少。[结论] 2025年吉隆坡市土地利用类型仍主要以种植园为主。宏观来看，随着城市的快速发展，种植园的数量持续减少。未来发展规划需进一步合理规划土地利用方式，提高土地利用效率，加大对种植园的保护力度。     

“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.     

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.     

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.     

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.