The effect of ionic strength on soil P reactions is negligible

The electrolyte concentration of the soil solution affects the availability of some nutrients in the soil, especially of P, but it is not know at what salt concentration the reactions start to be significantly affected and their magnitude. This study was carried out to evaluate the effect of rates of potassium chloride (KCl) on some soil parameters that determine supplying of P, K, Ca, Mg, and Al in an unlimed acid soil. Increasing rates of KCl (from zero up to 2000 mg K kg^–1) were applied to soil samples fertilized with 360 mg P kg^–1. Solution (C_li) and exchangeable (C_si) forms of P, Ca, Mg, K, and Al were determined in the treated soil samples after 30-days of incubation; cation activity in solution and their selectivity coefficients were then calculated. Addition of KCl at rates equal to or above 500 mg K kg^–1 caused a large relative increase on P in the soil solution (P_li) but a small and insignificant increase on the absolute value of P_li. All forms of soil K increased with increases on K applied, and buffer power for K varied according to the range of soil K. At all KCl rates, K displaced Ca, Mg, and Al from the solid phase to the soil solution, but had no effect on the extractable values. The relative preference of cations for the adsorption sites increased with increase on cation valency, and only those selectivity coefficients involving K were affected by K applied.     

Comparison of single and coastal superphosphate for subterranean clover on phosphorus leaching soils

Coastal superphosphate, a partially acidulated rock phosphate (PARP), is being considered as an alternative fertilizer to single superphosphate for pastures in high rainfall (> 800 mm annual average) areas of south-western Australia. The effectiveness of single and coastal superphosphate, as P fertilizers, was measured in two field experiments using dry herbage yield of subterranean clover (Trifolium subterraneum). The experiments were started in April 1990 and were terminated at the end of 1993. In the years after P applications, soil samples were collected each January to measure Colwell soil-test P, which was related to plant yields measured later on that year, to provide soil P test calibrations.Relative to freshly-applied single superphosphate, the effectiveness of freshly-applied coastal superphosphate and the residues of previously-applied single and coastal superphosphate were less effective in some years (from 3% as effective to equally effective), and up to 100% more effective in other years. This large range in effectiveness values in different years is attributed to different climatic conditions. Soil P test calibrations were different for soils treated with single or coastal superphosphate. The calibrations were also different for different yield assessments (harvests) in the same year, and in different years. Consequently soil P testing can only provide a very crude estimate of the current P status of the soils.     

单组分湿固化聚氨酯密封剂的制备、固化特性及开发应用

介绍了单组分湿固化聚氨酯密封剂的制备、固化特性及该产品的国内外发展概况，并就其开发工作提出了看法。     

考虑土体强度参数深度依赖性的非平稳随机场边坡滑动深度和体积分析

基于随机有限元方法（RFEM）和Monte-Carlo模拟,建立了能够模拟具有深度依赖性的土体强度参数边坡或具有软弱夹层边坡的非平稳随机场模型。通过辐射扫描方法获取最危险滑动面,得到非平稳随机场边坡滑动深度和滑动体积。将该方法与均质边坡和平稳随机场边坡获得的滑动深度和滑动体积进行对比,研究土体强度参数深度依赖性的非平稳随机场边坡的不同坡度和各向异性对滑动深度和滑动体积的影响。结果表明：基于RFEM的非平稳随机场滑动深度和滑动体积结果为地质灾害风险及后果评估提供了一个参考分析的新角度;参数的深度依赖性程度越高(变化率b越大),则边坡平均滑动深度和滑动体积越小;在大坡度滑坡风险后果评估中,可以基于均质边坡分析结果进行初步预估;在非平稳随机场中,随着各向异性的增大,所有坡度边坡的滑动体积变异系数增大;不同坡度下,水平方向的相关程度越大,则土坡内软弱夹层的不确定性越强,滑动体积的变异系数也不断增大。     

对土壤速测技术的几点看法

为有利土壤测试工作的开展,促进测土配方施肥技术的推广,对土壤速测技术提出一些基本观点:应用区域主要是乡镇一级;对测试速度要求当天拿结果即可;对准确性适度要求;土壤样仍以风干样品为好;土壤样品粒径统一取0.30 mm。并对速测项目,土壤浸提方法,水、化学试剂的选用提出意见。     

原子吸收光谱法测定土壤中的微量金属元素

采用火焰原子吸收光谱法测定了不同地区土壤样品中的铅、铜、镍、锌元素的含量,相对标准偏差为0.1-3.3,回收率为99.6%-101.6%。该方法简单、快速,并具有良好的精密度和准确度。重点讨论了前处理方法、共存离子对测定结果的影响。     

Phosphorus availability from phosphate rock and sewage sludge as influenced by the addition of water soluble phosphate fertilizer

Phosphorus (P) inputs are required for sustainable agricultural production in most acid soils of the tropics and subtropics. Phosphate rocks (PR) and organic materials have been suggested as alternative P sources in these soils. Quantitative information on the P availability from sewage sludge (SL) is scanty. Methods to improve the effectiveness of PR such as partial acidulation and compaction with water-soluble P sources have been recommended. The objective of this greenhouse study was to evaluate the relative agronomic effectiveness (RAE) of Florida PR and sewage sludges (irradiated and non-irradiated) applied alone and in mixture with a water-soluble source (triple superphosphate, TSP) at two rates (50 and 150 mg P kg^–1 soil). The ³²P isotope dilution technique was utilised to determine the proportion of P in the plant taken up from the P fertilizer treatments. Wheat was grown on an acid loamy sand Dystric Eutrocrepts and harvested 6 weeks after planting. Results on total P uptake and the RAE of the P fertilizer sources tested indicated that the addition of 50 mg P kg^–1 soil as TSP was adequate in supplying P to the 6-week-old wheat plants as compared to PR and sewage sludge. Intermediate values were obtained for the mixtures. Similar responses were observed for the high P rate. For a given P rate, phosphorus uptake from PR and SL in presence of TSP was higher than P uptake from these sources alone, indicating an enhancement effect of TSP on the effectiveness of these non-readily available sources. With respect to P uptake from PR applied alone, the relative increases in P uptake from PR due to TSP influence were 52 and 67% for the low and high P rates, respectively. The relative increases in P uptake from SL due to TSP when compared to P uptake from SL alone were 102 and 59% for the low and high P rates of application. Application of a water-soluble P fertilizer together with a non-readily available P source shows an enhancement on the P uptake from the non-readily available P source by the wheat plants. In this experiment the estimated enhancement effects are very likely underestimated.     

吸湿介质对碳纤维增强铸型尼龙复合材料的吸湿行为及力学性能的影响

本文对碳纤维增强铸型尼龙(CF／MC 尼龙)复合材料在不同吸湿介质中的吸湿行为进行了研究。结果表明，对于纤维体积分数为10％的碳纤维增强铸型尼龙复合材料(10％CF／MC尼龙复合材料)，随着吸湿介质的PH值减小，它的吸湿率增大。同时，经过吸湿后，10％CF／MC尼龙复合材料的弯曲强度有明显的下降。随着吸湿介质的PH值减小，试样的弯曲强度下降。使用环境扫描电子显微镜观察在10％HCl溶液中吸湿的试样的剪切断口形貌，得到的结果与吸湿实验的结果一致。     

重碱加压过滤的研究探索

在化工领域偿试使用加压过滤技术处理重碱，使重碱水份由真空过滤的１８～２０％降为加压过滤的１２％，可使生产厂家降低能耗；节约返碱     

非饱和黏性土直剪强度特性及其修正分析

为研究非饱和黏性土的直剪强度特性,采用非膨胀土及两种不同干密度的弱膨胀土进行了包含低应力状态下8种不同上覆压力的直剪试验。试验结果表明,随着上覆压力的增大,最大剪应力及所对应的剪切位移逐渐增大,试验中低应力状态下测定的土体凝聚力小于高应力状态,且试验中的上覆压力对膨胀性土凝聚力的影响大于非膨胀性黏土;而低应力状态下测定的土体内摩擦角大于高应力状态。对直剪试验中上下盒接触面积减小对抗剪强度参数测定的影响进行了分析,分析表明,接触面积减小对抗剪指标有影响,但极其微小。提出对膨胀土边坡浅层破坏进行稳定性分析时应采用低应力下的抗剪强度参数。