水淹胁迫对紫穗槐生长及营养元素积累的影响

通过对不同水淹条件下紫穗槐(Amorpha fruticosa)植株营养生长及各组织中营养元素积累量的分析,发现紫穗槐在表面水淹条件下根系浅生化,半水淹条件下茎根生长不定根,近全淹条件下先生长茎后生出不定根来适应水淹胁迫。3个水淹处理组植株对氮、磷、钙、铁及锰的吸收表现为增益;对铜的吸收表现为降低;改变氮、磷、钙、锌和铜的分配以适应水淹逆境,均与对照组植株存在明显差异(P<0.05)。所有处理各营养元素的积累量均不低于植物正常生长水平,营养生长指标未见严重缺素症,表明紫穗槐可针对不同水淹条件选择最有效节能的适应机制,是优良的抗涝灌木种。     

玉树典型嵩草草甸植物及土壤特性初探

以青海玉树小嵩草(Kobresia pygmaea)、藏嵩草(K.tibetica)健康草甸和退化草甸为研究对象,测定并分析比较了草甸的株高、盖度等植被特性和土壤有机质、土壤全氮、土壤全磷等土壤养分的变化规律,同时分析了环境因子对生物量的贡献率。结果表明,退化嵩草草甸植被盖度、植被高度和生草层厚度显著降低（P≤0.05）,鼠洞密度、裸地面积显著增加（P≤0.05）;退化嵩草草甸土壤含水量、土壤有机质和土壤全氮显著降低（P≤0.05）;土壤因子对生物量的贡献率最大,土壤因子与其它环境因子存在较高的多重共线性。以上结果说明,土壤因子质的改变是嵩草草甸退化最显著的特征。     

贵州都匀马尾松种子园针叶DRIS营养诊断分析

通过对都匀1．5代无性系种子园20年生马尾松针叶中N、P、K、Ca、Mg、Cu、Zn、Fe、Mn、B等营养元素含量变化的测定和分析,初步筛选出N／P、K／N、Ca／N、Mg／N、N／Cu、zn／N、N／Fe、K／P、Ca／P、P／Mg、P／Cu、P／Zn、Fe／P、K／Ca、K／Mg、K／Cu、K／Zn、Fe／K、Ca／Mg、Ca／Cu、Ca／Zn、Fe／Ca、MgJCu、Zn／Mg、Fe／Mg、Zn／Cu、Fe／Cu、Fe／Zn共28对元素比值为重要参数,对贵州都匀马尾松种子园针叶作DRIS营养诊断分析。结果表明,该地区马尾松针叶内Mn含量过高,平均值为767．01mg／kg,而B含量较低,仅为12．95mg／kg,马尾松的需肥顺序为Cu〉P〉Zn〉Mg〉Ca〉N〉K〉Fe。     

Phosphorus Enhanced Establishment,Growth, Nutrient Uptake,and Productivity of Dalbergia sissoo Seedlings Maintained at Varying Soil Water Stress Levels in an Indian Arid Zone

We assessed interactive effects of varying levels of applied phosphorus fertilizer and water stress on growth, productivity, and mineral accumulation in container-grown Dalbergia sissoo L. seedlings. Height, collar diameter, leaf size and area, root volume and total biomass were reduced, and dry matter allocation to root was increased with increasing levels of soil water stress. The reduction was >32% in growth, >50% in leaf, and >77% in biomass when seedlings were grown with <50% of soil field capacity. Phosphorus application at the level of 10 mg kg^?1 soil enhanced stems and leaf biomass and nutrient accumulation at all irrigation levels, and thus tolerance to drought. Phosphorus responses to growth and biomass production increased with irrigation levels. Thus, 20 mg P kg^?1 soil is beneficial at sufficient soil water availability and a lower dose (i.e., 10 mg P kg^?1) is recommended under high soil water stress conditions to benefit growth and productivity of D. sissoo.     

Effects of Simulated Acidic Precipitation and Aluminum on the Growth of Alnus glutinosa and Alnus hirsuta Seedlings and Their Nitrogen Fixation

This study was conducted to examine the effect of simulated acidic precipitation and aluminum treatment on the growth of Alnus species and the contents of nitrogen fixed by Frankia. The growth and nitrogen contents of Alnus species inoculated with nitrogen-fixing organisms were greater than those of noninoculated Alnus species when treated with simulated acidic precipitation. The nitrogen contents were higher in the soils used for the growth of Alnus glurinosa inoculated with Frankia than in those without Frankia inoculation when treated with either acidic precipitation or aluminum. The-development of root hairs treated with simulated acidic precipitation was poor as lhe pH level decreased, and the injury of A. glurinosa was more severe than that of Alnus hirsuta under scanning electron microscopy (SEM). The growth and nitrogen contents of A. hirsura inoculated with Frankia were greater than those of non-inoculated species and A. glutinosa when treated with aluminum. The leaves of A. glutinosa became yellowish-brown and fell earlier. Under SEM and light microscopy, the surface layer of roots in both Alnus species was injured severely and the number of root hairs decreased as aluminum levels increased.     

Estimating Weathering Rates of Swedish Forest Soils in Different Scales,Using the PROFILE Model and Affiliated Databases

Abstract

Weathering rates of forest soils are important for estimating nutrient sustainability and critical loads of acidity. Such rates can be estimated with the PROFILE model using input data about soil properties, climate, and forest species. PROFILE has been extensively tested on field data in the past, and found to perform well under a wide range of conditions. A high resolution soil geochemistry database now available in Sweden implies new possibilities for regional assessments of weathering rates as well as assistance to local assessments. Regional weathering rates are required by decision makers as inputs in forest sustainability assessments and critical load calculations, whereas calculations on a local level can provide help for the forest owners to adjust their forestry to the nutrient availability of the soil in order to inhibit long-term nutrient deficiency. In this paper weathering calculations for different scales, using the PROFILE model, are demonstrated and discussed. The high resolution geochemical database of Sweden is a good basis for PROFILE weathering calculations in different scales. The required resolution of complementing input data depends on the requested accuracy in the output, which is closely connected to the aim of the calculations.     

Recent Advances in Breeding Disease Resistant Pines / ONLANGSE VORDERINGS IN DIE TEELT VAN SIEKTE-BESTANDE DENNEBOME

Recent results in breeding disease resistant pines are discussed. Breeding for disease resistance is economically feasible and could be initiated in South Africa if it becomes necessary, provided that adequate personnel is appointed.     

3种肥料品种的氮素养分静水释放试验

以3种不同肥料品种为试验材料,通过静水释放试验测定其氮素养分释放速率。结果表明,3种肥料的氮素养分释放曲线均呈“L”形;尿素在第3h的氮素累积释放率就达到了99．53％,而油茶专用肥（15-6-9）和掺混肥（15-6-9）在第23h的氮素累积释放率分别达到97．28％和99．36％。从长期累积释放情况来看,油茶专用肥缓释性优于掺混肥,更优于尿素。可见,添加有机质、经过造粒工艺处理,可在一定程度上减缓肥料养分的释放速率,有利于提高肥料利用率和降低肥料对环境尤其是对水的污染。     

Advances in the Design of Resource-Efficient Cropping Systems

SUMMARY

Cropping systems in the Midwest USA are evolving as farmers seek labor-efficient designs to capture and use available light and precipitation. Heavy reliance on fossil fuels and other energy-intensive production inputs coupled with uncertain markets for commodities have encouraged the search for greater energy efficiency as well as alternative crops, markets, and production systems. Agroecology has emerged as an innovative and integrative approach to evaluating systems more suited to the often harsh and unpredictable environment, using native prairie structure and function as one guide to design of future systems. A more specific approach, Natural Systems Agriculture, is being explored as a new paradigm to saving soil while producing the crop and animal output needed for a growing global population. Whole-farm and landscape-level design and planning will become more important as society recognizes and values multifunctional rural landscapes.     

Delivering Fertilizers Through Seed Coatings

Summary

Coating seeds with nutrients may be an effective way of supplying starter fertilizer for establishment of seedlings and early growth. However, a large variability in benefits of providing nutrients with seeds has been reported, highlighting differences in the implementation of the techniques. This chapter will discuss the main principles relating to the imprecisely defined concept of nutrient-amended seeds.