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1.
你也许厌倦了那些长篇大论的新赛季预测,而我们也对每年必有的"费德勒将赢得大满贯冠军"的文档感到麻木,所以我们试着将对现实的分析和游荡在天空的想象揉合在一起,希望各位能带着一点娱乐的心态看待你即将读到的文字。这13件事也许真的会有一些在接下来的时间里发生,也可能会在年末被当成板砖拍向的目标。当然,这一切发生的前提是——玛雅人的预言没有发生。 相似文献
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红土旱地冬小麦根系生长动态观测 总被引:3,自引:0,他引:3
冬小麦根系的生长发育可概括为根系的形成、壮大和逐渐衰亡三个阶段。初生根对根乃至小麦的整体生育具有奠基作用。 相似文献
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红土坡地崩岗侵蚀过程与机理 总被引:15,自引:4,他引:15
崩岗是广泛发育于华南红色风化壳坡地上的各种崩陷地形,其危害性很大。按其形态特征可分为:条形崩网,叉(分支)形崩岗、瓢形崩岗、箕形崩岗和劣地崩岗等几种类型,其形态演变过程经历了前期的水蚀为主阶段,以及后期的重力侵蚀为主阶段,崩网的发生与下述几种情况有关:红土的机械组成特征,以及与水作用发生的变化;风化壳内的各种软弱结构面的存在;大暴雨触发作用以及各种地形要素的影响等。 相似文献
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红壤中水热耦合转化的实验和数值模拟研究 总被引:1,自引:0,他引:1
Coupled transfer of soil water and heat in closed columns of homogeneous red soil was studied under laboratory conditions.A coupled model was constructed using soil physical theory,empirical equations and experimental data to predict the coupled transfer.The results show that transport of soil water was affected by temperaature gradient,and the largest net water transport was found in the soil column with initial water content of 0.148m^3m^-3,At the same time,temperature changes with the transport of soil water was in a nonlinear shape as heat parameters wre function of water content,and the changes of temperature were positively correlated with the net amount of water transported.Numerical modelling results show that the predicted values of temperature distribution were close to the observed values,while the predicted values of water content exhibited limited deviation at both ends of the soil column due to the slight temperature changes at both ends .It WAS indicated that the model proposed here was applicable. 相似文献
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液体培养研究不同土壤中硝化活性 总被引:2,自引:0,他引:2
A red soil, a fluvo-aquic soil and a permeable paddy soil were used in a long-term investigation to study changes in nitrification with treatments: 1) soil incubation, 2) liquid incubation inoculated with soil samples, and 3) liquid incubation inoculated with ammonia-oxidizing bacteria (AOB) from the soils. There were significant differences (P < 0.001) in nitrification rates among the three soils when measured for 28 days by adding (NH4)2SO4 at the rate of 154 mg N kg-1 dry soil to fresh soil. However, the amounts of nitrifying bacteria in the three soils were not related to soil nitrification capacity. When the soil samples or the isolates of AOB enriched from the corresponding soil were incubated in liquid with pH 5.8, 7.0 and 8.0 buffers and 10 mmol L-1 ammonium nitrogen, there were no significant nitrification differences in the same soil type at each pH. The ability to oxidize ammonia through AOB from different types of soils in a homogeneous culture medium was similar, and the soil nitrification capacity could reflect the inherent properties of a soil. Altering the culture medium pH of individual soil type also showed that acidification of an alkaline fluvo-aquic soil decreased nitrification capacity, whereas alkalinization of the acidic red soil and permeable paddy soil increased their nitrification. For a better insight into factors influencing soil nitrification processes, soil properties including texture and clay composition should be considered. 相似文献
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The stability of aggregates in the surface soil is crucial to soil erosion and runoff generation. Thus, to understand the stability and the breakdown mechanisms of soil aggregates as well as the relationship between aggregate stability and selected soil chemical properties, such as different forms of Fe and A1 oxides, organic matter, CEC and clay content, the aggregates of slightly and severely eroded red soils derived from Quaternary red clay in subtropical China were analyzed using the routine wet sieving and the Le Bissonnais methods. The results indicated that the aggregates of the severely eroded soils were more stable than those of the slightly eroded soils. Different aggregate breakdown mechanisms resulted in different particle size distribution. The slaking from entrapped air in aggregates severely destroyed the soil aggregates,especially in the slightly eroded soils. Meanwhile, mechanical breakdown and microcracking had little effect on the aggregates compared to slaking. The fragments resulting from slaking were mainly microaggregates that increased in size with increasing clay content. The main fragment size of the slightly eroded soils was 1.0-0.2 mm, while for the severely eroded soils it was 5.0-2.0 mm and 1.0-0.5 mm. Overall, more than 20% of the fragments were smaller than 0.2 mm.In addition, aggregate stability was positively and often significantly correlated with Fed, Ald, Feo and clay content, but significantly and negatively correlated to SOC. 相似文献
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为研究中微肥和有机肥对红土晒烟外观和内在品质的影响,探索提高和改善红土晒烟品质的有效途径,试验在基肥中加入有机肥,和大田生长期在叶面喷施中微量元素肥料,结果表明:施用有机肥的处理与对照相比,产量增加7.3% ̄20.9%,产值增加8.8% ̄25.3%,以厩肥 菜籽饼处理的效果最好;四个喷施微肥的处理其产量和产值均超过了喷清水的对照,其中产量增加6.7% ̄15.6%,产值增加6.8% ̄20.5%,以喷施镁肥的增幅最大。另外,喷施硼肥的处理与对照相比,烟碱降低了29.5%,总糖提高了20.9%;施用有机肥的处理,上部叶总糖、还原糖、总氮和蛋白质含量比对照增加,但烟碱变化不大。因此,红土晒烟生产上控制在适宜用量范围内使用有机肥是可行的。此外,施用有机肥还使红土晒烟的评吸质量获得提高。在团棵期和旺长期喷施硼肥,掌握在适宜用量的范围不仅可有效降低红土晒烟的烟碱含量,使烟丝化学成分更趋协调,而且改善了红土晒烟的香气品质,使整体内在质量获得提高。 相似文献