Polyamine Profiles Of Healthy and Parasite-Infected Vaccinium Myrtillus Plants Under Nitrogen Enrichment

Addition of nitrogen (N) to the field layer of boreal forests has been shown to increase the occurrence of the parasitic fungus Valdensia heterodoxa on Vaccinium myrtillus plants. We investigated whether N addition to soil alters the levels of polyamines in V. myrtillus shoots, and discuss here whether such changes could promote the spread of the parasitic fungus on V. myrtillus. Using HPLC, we analyzed the concentrations of free and conjugated polyamines in healthy and naturally V. heterodoxa-infected V. myrtillus plants, which had received a moderate or high dose of N fertilizer, or no additional N. Fertilization with N increased the concentrations of free diamines (putrescine and diaminopropane), but had no significant effect on conjugated amines. Thus, N-induced changes in the constitutive levels of soluble conjugated amines do not seem to explain the increased parasite susceptibility of V. myrtillus under N enrichment. Generally, the concentrations of free diamines and insoluble conjugated putrescine were higher in diseased than in healthy shoots, suggesting parasite-induced accumulation of diamines. Free spermine seemed to accumulate in unfertilized, diseased plants, but in fertilized plants this induction was dampened, suggesting that N-induced alterations in spermine metabolism may promote the spread of parasites on V. myrtillus under N-enrichment.     

KINETICS OF PAHS LOSSES AND RELATIONSHIPS BETWEEN PAHS PROPERTIES AND PROPERTIES OF SOIL IN SEWAGE SLUDGE-AMENDED SOIL

Abstract

The properties of soil determine the activity of its microflora which is responsible for the degradation of polycyclic aromatic hydrocarbons (PAHs). Moreover, soil properties influence the strength of the interactions between the PAHs and individual soil components. The introduction of sewage sludge into the soil changes these properties which, in turn, changes environmental conditions. In the present studies, relationships between the PAH content and changes in selected soil properties (pH, CEC, TEB, BS, N _t ) have been evaluated. The present experiment was carried out in two blocks of experimental plots divided according to the type of plants grown. In the first block, the following field plants were grown in specific sequence, (maize, spring barley, winter rape, potatoes and cereal mixture) while in the other block a perennial, i.e. willow, was grown. Plant cultivation was carried out for 54 months, whereas the cultivation of the willow was conducted over 42 months. Each block consisted of 6 plots with a surface area of 15 m² into which sewage sludge had been introduced in the following doses: soil without fertilization – control, sludge 30, 75, 150, 300, 600 t/ha. Both the disappearance rate and the scope of the individual polycyclic aromatic hydrocarbons as determined by their respective half-lives showed that losses of these compounds depended on the sewage sludge properties (among other things, the pollutant content) as well as the sludge dose and the type of area used. The correlation coefficients determined depended on the sludge dose and the experimental variant. The highest frequency of their occurrence was found in the case of the total sum of nitrogen and cation exchange capacity for the highest sludge doses (in the experimental with willow).     

科学施肥,提高化肥利用率与建议

为提高我国化肥的利用率，希望能做到科学合理施肥，同时提出了几点可行的建议。     

我国科学施肥技术的发展历程及趋势

将我国科学施肥技术的发展划分为"三个阶梯",分别为参照施肥技术模式施肥、根据区域大配方施肥、针对具体田块精准施肥。讨论了各阶梯的关键技术及其在推荐施肥中的特殊位置。     

Balanced pasture fertilization in the Basque Country: I. Phosphorus and potassium budgets on dairy farms

Dairy farming is the main agricultural activity of the Basque Country. A dairy farm is characterized as a system with soils and crops, forage, cattle and manure as main components, and in such a system, nutrient cycling is very important to maintain soil fertility and optimize forage production. To quantify nutrient transfers in the cycle, a simple system was developed and has been applied to seventeen farms to examine its ability to achieve a balanced P and K fertilization. These farms have provided data on inputs (fertilizer, feeds, concentrates), pasture and manure management, and outputs (milk production), and soil samples have been taken from farm pastures. Phosphorus and K in excreta and uneaten pasture is used with a relatively high efficiency as suggested by the relatively high efficiency of P and K utilization by the pasture that usually ranges from 70 to 90%. Concentrate feeding (3000 kg cow^–1 yr^–1) represents one of the main P and K inputs in Basque Country dairy farms, averaging 26 and 66 kg ha^–1, respectively. Besides, release of K in the soil through slow liberation from non-exchangeable sites was estimated as 30 kg ha^–1. Thus, a high efficiency in excreta recycling would diminish substantially P and K mineral fertilizer needs. Farm nutrient budgets appear to be a convenient tool for determining nutrient shortages and surpluses at farm level, and thus they are considered as a first step to support a better management of maintenance fertilization of permanent pastures.     

稀相气固两相流动的数值求解

本文对SIMPLE方法作了推广,提出了一种求解二维湍流稀相气固两相流动的数值方法。流动的六个控制方程都是非线性的,而且是互相耦合的偏微分方程。本文给出了求解固相容积率方程的一个稳定的差分格式,讨论了松驰因子,源项的处理方法及迭代方法的改进等因素对整个数值解的收敛性的影响,绘出了变量的残留误差随迭代次数的变化曲线。并就水平直管内的高载荷比气固两相流动进行了数值计算,其计算结果和收敛速度都是令人满意的。     

ANSYS 8.0在软基复杂水工结构分析中的应用

由于分析计算方法和手段的限制,长期以来对于软土地基上的水工结构,都是通过简化为平面问题的方法采进行分析计算.用平面分析的方法有相当的局限性,且不能考虑建筑物和地基的共同作用,现运用有限元方法,应用非线性理论对软土地基上复杂水工结构的空间应力应变分布情况进行数值分析,通过结合工程实例,将计算分析结果与原形监测数据进行比较,得出了很好的相关性,证明了此分析方法是可行和有效的。     

平衡施肥对稻田产量和土壤养分的影响

分析了水稻田土壤营养状况,土壤中N、P、K、Zn、Mn、Si等对沈农606超级稻的营养特性、吸肥规律、以及产量、质量的影响。对平衡施肥和生物肥技术进行了实验研究。试验区土壤有机质含量处于一般水平,土壤速效N、P、K、Zn及Mn普遍缺乏;N、K、Mn、Zn、Si均为产量限制因子。应用高产优质平衡施肥技术可以显著增加作物产量,多点平均产量为12.58t/hm2,较习惯施肥区产量增加1.46t/hm2,增产13.13%。     

城市污水处理厂污泥的肥料化利用

随着世界工业生产的发展,城市人口的增加,工业废水与生活污水的排放量日益增多,污泥的产出量迅速增加,城市污水污泥是城市污水处理的副产品,为避免二次污染和有效利用污泥中的有效成分,污泥的处理已经成为全世界关心的问题.目前污泥的处理方式主要有填埋、投海、焚烧、肥料化利用.本文通过对污泥的几种处理方式的比较,认为将稳定化、无害化处理后的污泥作为一种有机肥料使用,将成为我国一种很有应用前景的污泥处置与利用途径.