桑树夏伐时间与土化性状的关系

为探索夏伐时间与土化性状的关系,在同一桑园地且其它桑园管理措施一致的前提下进行了该试验。结果是采叶后第2~4d夏伐,可适当提高土壤养分含量,改变土壤pH值,同时影响土壤物理性状及桑树生长发育性能。结合该夏伐时间对桑叶产质量的影响之结果,生产中建议推广使用采叶后第3d夏伐的伐条方式。

春伐桑树不同伐条时间与土化性状及桑树生长发育的关系

试验在桑园其它管理措施一致的前提下,改变其伐条时间,并对土壤理化性状及桑树生长发育进行了跟踪调查。结果是12月底到翌年1月初伐条,可适当提高土壤养分含量,同时影响土壤物理性状及桑树生长。

夏伐桑树不同栽植密度与土化性状的关系

为探索夏伐桑树不同栽植密度与桑园土化性状的关系,在同一桑园地并在其它桑园管理措施一致的前提下进行了试验。结果表明：夏伐桑树每667m^2桑地面积栽植400～600株,可适当提高土壤养分含量,改变土壤pH值,同时影响土壤物理性状及桑树生长发育性能。

种茧育桑园测土配方施肥比例的试验初报 3.冬季不同施肥比例对土壤理化性状的影响

试验在其它桑园管理措施一致的前提下,改变其N、P2O5、K2O肥的施用比例,并对土壤理化性状进行了调查。结果N∶P2O5∶K2O=10∶5∶5能适当提高土壤速效钾含量和适当降低土壤pH值;显著提高土壤有机质含量和全氮含量;极显著提高土壤速效磷含量;同时影响土壤的物理性状及桑树生长。

不同技术处理对桑园土壤理化性状的影响

在桑树栽植密度和其它桑园管理措施一致的前提下,对春伐桑树不同技术处理与土壤理化性状的关系进行了调查。结果是栽植密度为每667m^2种植1 000-1 200株、N：P2O5：K2O=10：5：5的施肥比例,每667m^2桑园面积留条7 500-8 000根,低干无拳式树形的组合,对土壤理化性状及桑树生长发育没有显著影响。

春伐桑树省力化施肥技术的试验初报(II)

在保证全年施肥量一致、其它桑园管理措施相同的前提下,省力化施肥技术在极显著降低667 m2桑地面积用工数的前提下,可适当提高土壤养分含量和桑树生长发育性能及土壤理化性状,同时降低土壤pH值。

种茧育春伐桑园氮磷钾肥比例对桑叶产量的影响

试验在桑园其他管理措施一致的条件下,改变N、P2O5、K2O肥的施用比例,并对桑叶产量及土壤理化性状进行了调查。结果是N∶P2O5∶K2O=10∶5∶5的施肥比例,可适当提高春季发芽率和土壤速效钾含量,显著提高春叶产量及全氮含量,极显著提高秋叶产量、土壤有机质含量及速效磷含量,同时影响土壤的物理性状及桑树生长。

不同技术处理桑树对冬季桑园的影响

在其它桑园管理措施一致的前提下,采用施肥比例N∶P2O5∶K2O=10∶5∶5、667m^2桑地面积留条7 500～8 000条、中干拳式树形的技术组合,可适当提高土壤养分含量,改变土壤pH值,同时影响土壤物理性状及桑树生长。

春伐桑树不同栽植密度对冬季桑园的影响

为探索春伐桑树不同栽植密度对冬季桑园的影响,在其它桑园管理措施一致、并在同一地块的前提下进行了该试验。结果是春伐桑树每667m^2桑地面积栽植900-1 200株,可适当提高土壤养分含量,改变土壤pH值,同时影响土壤物理性状及桑树生长发育性能。

桑园不同耕作方式与免耕种植的比较试验 3.不同耕作方式对冬季桑园的影响

在其它桑园管理措施一致的情况下,就不同耕作方式对冬季土壤理化性状的影响进行了试验。结果是不同耕作方式对冬季桑园的影响较大。建议有条件的地区采用每年2～3次的耕作方式,而免耕种植方式必须与化学除草相结合,才能发挥其作用。

Study on Influencing Factors of Farmland Soil Heavy Metals in Central Yunnan Province

[Objective] This study aimed to explore the relationship between contents of heavy metals with soil type, altitude distribution as well as physical and chemical properties. [Method] Based on determination of contents of soil heavy metals and soil physical and chemical properties from agricultural land in Central Yunnan Province, the relationship between soil heavy metals with soil type, altitude distribu- tion and soil physical and chemical properties were analyzed. [Result] The average contents of all heavy metals in farmland of Central Yunnan didn＇t extend their limits of Grade II in the National Soil Environmental Quality Standard （GB15618-1995）. and the heavy metals content in red soil was higher than that in other types. Soil Cd content changes slightly with the altitude, while contents of other heavy metals were greatly affected by altitude. There were extremely significant positive correlation between heavy metals and clay particle content, that is, soil with heavier texture has more heavy metals. There was positive correlation between pH and each heavy metal content; there were positive correlation between Mn with Pb, Cd, Hg and Hg; exchangeable Ca and Mg contents in soil show negative correlations with most heavy metals. [Conclusion] This study has provided scientific bases for the heavy metal management in Central Yunnan area.

Effects of Green Manure Mixed Cropping Patterns on Physical and Chemical Properties of Soil and Economic Characters of Flue-cured Tobacco

[Objective] The aim was to clear the suitable green manure cropping pat- terns in Xiangxi tobacco-planting areas. [Method] 8 treatments were set to study the effects of the monoculture and mixed cropping of common vetch （Vicia gigantea Bge.）, perennial ryegrass （Lofium） and rapeseed （Brassica campestris L.） on physi- cal and chemical properties of soil and economic characters of flue-cured tobacco. [Result] （1） Green manure turnover can reduce soil bulk density by 1.08%-8.62%, and the effect of green manure mixed cropping pattern was the best. （2） Green manure turnover also can increase the soil nutrient, soil organic matter, total nitro- gen （N）, total phosphorus （P）, total potassium （K）, alkali-hydrolyzale N, rapidly available P and rapidly available K by 1.44%-6.10%, 0.01-0.12 g/kg, 1.89%- 11.32%, 0.12%-3.56%, 1.06%-11.76%, 0.04%-18.93% and 0.98%-23.12%, respec- tively, and the effect of the monoculture of common vetch was the best.（3） The overall change of soil pH was not obvious.（4）Green manure turnover can increase the yield and output of flue-cured tobacco, and the effect of the monoculture of common vetch was the best. [Conclusion] The monoculture of common vetch can be generalized in the dry land of Xiangxi tobacco-planting areas.

Effects of Once Fenlong Cultivation on Soil Properties and Rice Yield and Quality for 7 Consecutive Years

[Objective] The objective of this study was to explore the long-term effect of Fenlong cultivation for one time. [Method] The physical and chemical properties of soil and rice yield and quality were investigated and determined by measuring the soil at the depth of 23 cm in the paddy field with Fenlong cultivation and 16 cm of control （conventional farming） for 7 years. [Result] Compared with the control, the average yield of early rice of the Fenlong cultivation increased by 1 972.5 kg/hm2 of the first year, an increase of 23.87%, and milled rice and protein increased by 15.95% and 14.61%, while the increase rates of organic matter, available nitrogen, available phosphorus and available potassium per hectare were 74.58%, 67.01%, 104.41% and 129.62%, respectively. In the 7th year after Fenlong cultivation, the yield increased by 234 kg/hm2 from the control, an increase of 3.21%, and milled rice and protein increased by 0.5% and 0.14%, while the increase rates of organic matter, available phosphorus and available potassium per hectare were 745.8%, 62.635 and 73.37%, respectively, and the increase rates of total nitrogen, total phosphorus and total potassium were 46.03%, 50.58% and 36.65%, respectively. During the 7 years after Fenlong cultivation, the yield increased by 3.21-23.87%, and its average net income per season increased by 1 843.61 Yuan/hm2 with a gain of 18.03%. [Conclusion] At the 7th year after Fenlong cultivation, the paddy field still had the furrow remain at a depth of 22 cm, which was 46.67% thicker than the traditional one. The yield and quality of paddy rice increased for 7 consecutive vears showed that Fenlon.q cultivation was highly feasible for paddy field.

Assessment of rapid impact compaction in ground improvement from in-situ testing

Ground improvement has been used on many construction sites to densify granular materials, in other word, to improve soil properties and reduce potential settlement. This work presents a case study of ground improvement using rapid impact compaction （RIC）. The research site comprises the construction of workshop and depots as part of railway development project at Batu Gajah-Ipoh, Malaysia. In-situ testing results show that the subsurface soil comprises mainly of sand and silty sand through the investigated depth extended to 10 m. Groundwater is approximately 0.5 m below the ground surface. Evaluation of improvement was based on the results of pre- and post-improvement cone penetration test （CPT）. Interpretation software has been used to infer soil properties. Load test was conducted to estimate soil settlement. It is found that the technique succeeds in improving soil properties namely the relative density increases from 45% to 70%, the friction angle of soil is increased by an average of 3°, and the soil settlement is reduced by 50%： The technique succeeds in improving soil properties to approximately 5.0 m in depth depending on soil uniformity with depth.

Ethylene Polymerization with Palygorskite Supported Nickel-Diimine Catalyst

A nickel-diimine catalyst [N, N'-bis(2,6-diisopropylphenyl)-1,4-diaza-2,3-dimethyl-1, 3-butadiene nickel dibromide, DMN] was supported on palygorskite clay for ethylene slurry polymerization. The effect of supporting methods on the catalyst impregnation was studied and compared. Pretreatment of the support with methylalumi-noxane (MAO) followed by DMN impregnation gave higher catalyst loading and catalytic activity than the direct impregnation of DMN. Catalyst activity as high as 5.42×105g PE·molNi-1·h-1 was achieved at ethylene pressure of 6.87×105 Pa and polymerization temperature of 20℃. In particular, the morphological change of the support during MAO treatment was characterized and analyzed. It was found that nano-fiber clusters formed during the support pretreatment, which increased the surface area of the support and favored the impregnation of the catalyst. The investigation of polymerization behavior of supported catalyst revealed that the polymerization rate could be kept at a relatively high level for a long time, different from the homogeneous catalyst. By analyzing the SEM photographs of the polymer produced by the supported catalyst, the morphological evolution of polymer particles was preliminarily studied.

Soil Uncertainties on Performance of Geotechnical Works

Performance-Based Design （PBD） is a more rational approach, particularly in seismic environments. In this approach it is relevant the performance required to structures and to geotechnical works, as well as the geotechnical constitutive models used to predict the performance. The parameters of the constitutive models are related in turn to soil properties. So soil properties are a key point for Performance-Based Design. Questions arising are： （i） which are the more relevant soil properties to solve a specific PBD geotechnical problem？ （ii） which are the more relevant model parameters and how they can be evaluated and/or correlated to soil properties？ （iii） which is the role of the soil parameters uncertainty in Performance-Based Design？ An answer to these questions is given in this paper, outlining the potential offered by the new advanced in-situ and laboratory tests and discussing the performance required by some geotechnical works.

Properties of Fresh and Hardened Self-compacting Concrete Produced by Using Locally Available Materials

Self-compacting concrete （SCC） is defined so that no vibration is necessary for the compaction. The main criteria of producing SCC have to satisfy the following characteristics [1, 2, 3]： （1） Ability to flow into and completely fill complex forms under its own weight; （2） Ability to pass through and bond to congested reinforcements; （3） High resistance to aggregate segregation. Self-compacting concrete presents a significant sign in improving the product quality and efficiency of the building industry. It also enhances the working conditions and the quality and appearance of concrete. Japan has been used self-compacting concrete in bridge, building and tunnel construction since the early 1990s. In the last decade, SCC has been produced a high potential for greater acceptance and wider applications in highway bridge construction in the Europe and U.S.. However, till now, there is no application of SCC in the construction industry in Egypt. Therefore, the main objective of this research is to produce SCC by using the locally available materials in our region such as basalt, gravel, sand, limestone powder and silica fume. Experimental programme was designed to characterize the properties of fresh and hardened SCC. It comprises different concrete mixes thbricated with different types and percentages of constituent materials. Three full-scale reinforced concrete beams were fabricated from the SCC mixes and tested under flexure. For the purpose of comparison, an extra RC beam was made of conventional normal concrete to serve as a reference beam. This study, in general, demonstrated that the applications of SCC in construction industry oiler products with enhanced characteristics as well as could be economical.

Scale Dependence of Soil Spatial Variation in a Temperate Desert

Spatial variation is a ubiquitous feature of natural ecosystems, especially in arid regions, and is often present at various scales in these regions. To determine the scale dependence of the heterogeneity of soil chemical properties and the dominant scales(factors) for soil heterogeneity in arid regions, the spatial variability of soil resources was investigated in the Gurbantunggut Desert of Central Asia at the scales of 10-3, 10-2, 10-1, 100, 101, 102, 103and 104m(from individual plant to population or community to ecosystem). Soil chemical properties including pH, electrical conductivity(EC), organic carbon, total nitrogen, available nitrogen, total phosphorus, and available phosphorus were considered in the investigation. At a scale of 10-1m, which represented the scale of individual plant, significant enrichment of soil resources occurred under shrub canopy and "fertile islands" formed in the desert ecosystem. Soil EC exhibited the largest heterogeneity at this scale, indicating that individual plants exerted a great influence on soil salinity/alkalinity. Soil nutrients exhibited the greatest heterogeneity at a scale of 102m, which represented the scale of sand dune/interdune lowlands(between communities). The main important factors contributing to soil spatial heterogeneity in the Gurbantunggut Desert were individual plants and different topographic characteristics, namely, the appearance of vegetation, especially shrubs or small trees, and existing sand dunes. Soil salinity/alkalinity and soil nutrient status behaved differently in spatial heterogeneity, with an inverse distribution between them at the individual scale.

Influence of Soil Properties on Zinc Solubility Dynamics Under Different Redox Conditions in Non-Calcareous Soils

Zinc(Zn) deficiency in paddy soils is often a problem for rice production.Flooding can decrease metal availability in some noncalcareous soils through different mechanisms associated with soil redox status.Laboratory experiments were performed in order to better understand the processes that governed the dynamics of Zn in non-calcareous paddy soils at varying redox potentials(Eh).Airdried non-calcareous soil samples collected from four different paddy field sites in the Philippines were submerged and incubated in a reaction cell with continuous stirring and nitrogen purging for 4 weeks,and then purged with compressed air for another week to reoxidize the system.The Eh of the four soils started at 120 to 300 mV,decreased to —220 to —300 mV after 100 to 250 h of reduction,and was maintained at this low plateau for about 2 weeks before increasing again upon reoxidation.Zinc solubility showed contrasting patterns in the four soils,with two of the soils showing a decrease in soluble Zn as the Eh became low,probably due to zinc sulfide(ZnS) precipitation.In contrast,the other two soils showed that Zn solubility was maintained during the reduced phase which could be due to the competition with iron(Fe) for precipitation with sulfide.Differences in the relative amounts of S,Fe,and manganese(Mn) oxides in the four soils apparently influenced the pattern of Zn solubility after flooding.