河北省低平原区近16年来农田施肥量、作物产量和养分效率的变化特征

为阐明近16年来河北省低平原区农田养分管理措施对作物产量和养分效率的影响,提高农田养分管理技术水平,对1998~2014年在河北省开展的6个土壤肥力定位监测试验进行了统计分析。结果发现,河北省低平原区小麦氮、磷、钾肥施用量一直维持在较高的水平,年平均施用量分别为315.2、199.5和173.2 kg/hm~2。玉米施肥量逐年增加,2014年氮、磷、钾施用量分别为247.0、69.8和128.5 kg/hm~2。小麦、玉米施肥区产量分别较1998年提升了40.7%和72.4%,小麦无肥区没有明显增产,玉米无肥区产量提高了36.1%。施肥量增加对小麦产量没有明显的影响,但对玉米产量增加有显著的促进作用,其中氮素是影响玉米产量的最主要因素。小麦的氮肥偏生产力和农学效率因施肥量较高在过去16年间没有明显的变化,而玉米则随时间和施肥量的增加呈下降趋势。土壤基础地力对小麦、玉米产量的贡献率呈逐年下降的趋势。     

变频调速装置在给水系统中的应用分析

分析讨论了工业企业给水系统的特点和当前常用的给水系统调节方式和优缺点及变频调速装置的节能原理,指出变频调速装置应用于给水系统是最为节能的运行方式.     

Determinants of parr size variations within a population of brown trout Salmo trutta L.

Abstract – The size of 2-month old trout Salmo trutta parr differed between sites and between years along the River Esva catchment (Asturias, northwestern Spain). Such variation was in a direction opposite to the variation observed in parental size. Parr were smaller in sites where parents grew faster, whereas larger parr occurred in sites where parents grew less. Parr size of six cohorts (1990–1996, except 1995) at 14 sites along the River Esva was inversely related to the growth rate and length of parents and positively related to canopy, egg size, and water temperature. The latter acted similarly on all parr independently of egg size and the site where the egg originated. Covariation patterns among parr size, parental traits, and canopy suggest that a canopy-regulated, growth-determined trade-off between egg size and number, previously described for the Esva trout, also extends to alevin size. In forested, shaded sites, adult trout grew less and spawned fewer larger eggs that resulted in larger alevins, whereas in fully insolated, production-rich sites, trout grew faster and spawned higher numbers of smaller eggs that produced smaller parr. I hypothesize that the phenotypic plasticity illustrated by the environmentally induced trade-off between egg size and number further extended to alevin size may be evolutionarily advantageous because it relates the size of trout alevins to food availability, as predicted by the growth previously experienced by parents. ^NOTE     

不同林龄油松人工林叶凋落物分解特性

2005年在北京市延庆县营盘村附近中山采用网袋法,比较21、29、36年生油松叶凋落物分解动态、分解速率、基质质量的差异.结果表明:在所观测的14个月内,不同林龄油松叶凋落物分解动态差异较小,均呈快椔龡快的规律,翌年5至7月份凋落物分解速率低于2005年同期的分解速率.21 a、29 a、36 a油松叶凋落物分解速率分别为26.97％、26.10％和23.96％,半分解周期分别为2.21 a、2.29 a和2.54 a,周转期分别为9.54 a、9.91 a和10.94 a.凋落物分解速率、半周转期、周转期失重率仅在0.1水平上差异显著.林龄对叶凋落物N影响最大(P=0.004),对粗灰分(P=0.028)影响显著.林龄对纤维素、木质素、粗脂肪、粗蛋白影响不显著.不同林龄叶凋落物C/N(P=0.009)、木质素/N(P=0.048)显著差异,C/N、木质素/N与叶凋落物分解速率相关系数均为-0.333.     

遮荫对10种地被植物光合特性的影响

为了探讨地被植物在不同遮荫条件下的适应性,本研究以10种地被植物为材料,对其在不同光照条件下的生长状态、日平均净光合速率、表观量子效率及光补偿点进行分析.结果表明:遮荫水平对10种植物的光合有很大影响,10种植物能忍受的遮荫程度不同.对旋覆花、甘野菊、大叶铁线莲、青杞、委陵菜来说,全光比较合适;对蛇莓、匍枝毛茛、匍枝委...     

Soil texture affects the conversion factor of electrical conductivity from 1:5 soil-water to saturated paste extracts

Electrical conductivity(EC) of soil-water extracts is commonly used to assess soil salinity. However, its conversion to the EC of saturated soil paste extracts(ECe), the standard measure of soil salinity, is currently required for practical applications. Although many regression models can be used to obtain ECe from the EC of soil-water extracts, the application of a site-specific model to different sites is not straightforward due to confounding soil factors such as soil texture. This study was...     

Estimating cation exchange capacity using soil textural data and soil organic matter content: A case study for the south of Iran

Cation exchange capacity (CEC) is an important soil property that is used as an input data in soil and environmental models. Although CEC can be measured directly, its measurement is expensive and time-consuming, therefore pedotransfer functions can be used for estimating it from more readily available soil data. As CEC is highly dependent on soil texture, it may be successfully estimated from the soil textural data. In this study, 20 soils were selected from Fars province, in the south of Iran, and the values of CEC, soil organic matter content, and soil particle size distribution curve of each soil were measured and the geometric mean particle-size diameter (d _g ), and the summation of the number of spherical particles for whole parts of the soil particle-size distribution (N) were determined for each soil. Then, five multiple linear regressions were derived between CEC and mentioned soil properties. The results showed that more applicable equation for the study area was based on the percentages of clay, sand and soil organic matter content.     

重庆市植烟区不同肥力植烟土壤氮素矿化特性研究

通过室内培养试验研究了重庆市植烟区不同肥力植烟土壤氮素矿化规律,求得土壤氮素矿化参数,并探讨了氮素矿化潜势（N0）、有机质、全氮、pH、碱解氮之间的关系。结果表明,在35℃条件下培养,一级动力学方程能够很好的拟合氮素的矿化过程,相关系数均达到显著水平（r高肥力土=0.976、r中肥力土=0.986、r低肥力土=0.996）,不同肥力土壤氮素矿化量存在显著差异。矿化潜势(N0)为：高肥力土（25.0mg?kg-1±0.60）﹥中肥力土（21.5mg?kg-1±0.61）﹥低肥力土（19.7mg?kg-1±1.14）;矿化速率（k）为：低肥力土（0.1596mg?kg-1?d-1±0.0104）﹥中肥力土（0.1492mg?kg-1?d-1±0.0155）﹥高肥力土（0.1029mg?kg-1?d-1±0.0071）。矿化潜势(N0)与全氮、有机质呈正相关,相关系数分别为0.9799和0.9788,与pH之间呈负相关（R=-0.9784）。表明不同肥力植烟土壤的供氮能力存在差异,在肥料管理上要因土、因时施肥。     

不同类型玉米品种间子粒脱水速率相关分析

利用10个黄淮海区域有代表性的玉米品种,进行子粒脱水速率相关性状研究。结果表明,子粒水分含量与散粉天数、生理成熟天数、穗轴水分、苞叶水分、百粒重及小区产量具有显著的正相关,与子粒脱水速率呈显著负相关。不同品种所有子粒脱水性状间均存在显著差异。通径分析结果表明,仅苞叶水分这一性状对子粒含水量具有显著的正向直接效应。依据子粒生理成熟期时的水分含量把其划分为3种不同脱水类型,品种不同类型、同一类型不同品种间均具有完全不同的脱水方式。根据研究结果提出,实现机收子粒应该重点考虑3个重要因素,即生理成熟期、生理成熟后子粒脱水速率和种植密度。