The impact of land use on the credibility of dispersive clay soils in central and southern Italy

Abstract. Tracts of dispersive Plio-Pleistocene clays in central and southern Italy suffer from severe erosion, which has led to the creation of badlands characterized by 'calanchi'(unvegetated knife-edge ridges) and 'bian-cane'(cone-shaped hummocks). In recent decades, large areas of this eroded land have been reclaimed for arable cultivation by remodelling the landscape with heavy earth moving equipment. This exposes the clay to erosive rainfall. Wet aggregate strength was used to assess those physical and chemical properties that govern the erodibility of the clays. Regression analysis demonstrated that the most significant variables in predicting soil erodibility were the % organic matter and the exchangeable sodium percentage (ESP). Threshold values of 1–2% and 3–4% organic matter were obtained, dependent on the method of pre-wetting. Reclaimed land is on the borderline of these thresholds and therefore at risk of erosion. Nevertheless, the stability of reclaimed land is significantly higher than that of the badland parent material, ascribable to a lower ESP. Careful land management is required to avoid a recurrence of erosion and the reestablishment of badlands.     

Aggregate stability in organically and conventionally farmed soils

A range of factors that influence aggregate stability and soil erodibility were analysed for soils sampled from land managed under contrasting agricultural methods. These included: an organic farm; a conventional farm that incorporated organic fertilizers; a conventional farm that only used inorganic fertilizers; and a non-cultivated control site. The stability of aggregates that compose the bulk soil structure (macroaggregates), and aggregates that were mobilized from the soil by simulated rainfall and surface runoff (microaggregates), were evaluated in terms of the soil fragmentation fractal dimension, organic carbon content and ATP (adenosine 5'-triphosphate; a signature of live biomass) concentration. The results were used to interpret the existing physical condition of the soils, the (microbial) processes that contribute to that physical structure, and how both pedogenic processes and existing soil quality are influenced by agricultural methods. The soils sampled for this study were demonstrated to be multi-fractal in nature: soils with greater bulk density were composed of more stable macro-aggregates, which, in turn, fragmented into larger, more stable micro-aggregates, rendering the entire soil structure less erodible. Soil erodibility and sustainable soil management should therefore be approached at multiple scales. The primary control on both macro- and micro-aggregate stability was determined to be the organic matter input to the soil, as represented by measurements of organic carbon and ATP. Organic content was greatest for the non-cultivated soil, which reflects the degradation of organic reserves in cultivated soils. For cultivated soils, it was not possible to differentiate aggregate stability for soils managed under organic or conventional (i.e. using biological and inorganic fertilizers) farming practices, but aggregates of soils that only received artificial fertilizers consistently exhibited less stability.     

螯合物稳定性的探讨

螯合物的特殊稳定性在许多方面得到广泛应用，但其稳定性的原因未见有关资料详细报道。从原子结构和热力学两方面对其阐述之，澄清了人们对其的模糊认识。     

三种乳化剂对疫苗乳液稳定性的影响

采用正交试验L9(34),对F-188、ELP和TWEEN-80三种乳化剂的复配比例进行了研究.结果表明:F-188∶ELP∶TWEEN-80的比例为1∶3∶3时,疫苗乳液的稳定性最好,黏度较小,乳液颗粒直径皆在0.2μm以下,且粒径均匀.方差分析表明,3种乳化剂对乳液稳定性的影响差异极显著(P<0.01),且ELP、TWEEN-80的乳化效果极显著优于F-188.     

气象信息与农业经济决策的一种数学方法

本文给出了一种更加合理，有效地利用气象信息进行农业生产决策，以提高气象信息经济价值的最优决策方法，并引入了转变概率，决策区域等概念，以简化最优决策及其稳定性分析过程。     

表面活性剂改善竹丝板尺寸稳定的研究

针对竹丝板生产存在的问题,探讨添加表面活性剂对改进竹丝酚醛树脂浸渍含量和竹丝板尺寸稳定性的影响.试验结果表明,在选用的3种表面活性剂中,OP-10对酚醛树脂浸渍含量的影响不显著,但可以明显提高竹丝板的尺寸稳定性;与改性剂聚乙二醇PEG-1000同时使用时效果更显著.     

具连续分布时滞细胞神经网络的指数稳定性

利用Cramer法则和Brouwer不动点定理,通过构造适当的Lyapunov泛函并结合矩阵形式的Halanay微分不等式分析技巧,研究了一类具有连续分布时滞的细胞神经网络模型的动力学性质,获得了该模型的平衡点的存在性和全局指数稳定性的充分条件.改进和推广了已有文献的结论.这些结果对设计全局指数稳定的细胞神经网络具有重要的指导意义.     

路面基层水稳砂砾裂缝分析及防治办法

结合黑龙江省水泥稳定砂砾施工裂缝的防治、分析及处理办法,从选定料源,进场材料控制,施工含水量、摊铺时间进行控制,就能有效减少裂缝病害的出现。     

发酵乳饮料稳定性的研究

本次实验通过使用稳定剂、乳化剂和品质改良剂，对发酵乳饮料的稳定性进行了研究。实验结果表明，使发酵乳饮料的稳定性最好，风味最佳的配方是30％的发酵乳、62％的水、8％的白砂糖，0．3％的CMC，0．1％的蔗糖酯，0．05％的单甘酯，0．1％的Na2HPO，，并用0．1％的柠檬酸调酸到60'T左右。     

地克珠利在溶液中稳定性的研究

地克珠利是一种高效低毒的广谱驱球虫药。本研究分别采用６０℃密闭、避光加热实验，３７℃密闭、避光加热实验，室温自然光照实验及连续加热不同酸碱度溶液实验，对地克珠利溶液的稳定性进行了考查。结果表明：地克珠利在溶液中对光、对热、对碱不稳定；地克珠利溶液制剂应在避光、阴凉处保存。