上海土壤磷的吸附特性及缓冲性能的研究   总被引：8，自引：0，他引：8  

傅明华  戴朱恒  承友松  顾仲兰 《土壤学报》1986,23(2):113-123

本文以上海土壤为对象,研究选定了土壤磷等温吸附试验条件为:水土比10,平衡时间6天,控温25℃,磷加入量为100,200,400,600μgP/g土,溶液基质为0.01M CaCl₂。磷缓冲能力试验条件为:平衡时间2天,磷加入量为20,40,100,200μgP/g土。根据Freundlich, Tempkin和Langmuir方程计算的土壤吸附指标与土壤类型及土壤性质有密切关系,是土壤磷素肥力的重要指标。反映土壤缓冲能力的“磷肥指标”与土壤有机质、粘粒、活性铝及pH值相关较好。上海几种主要土壤中以青紫泥的最大吸附量(X_m),0.2ppm P吸附量和“磷肥指标”为最高,其次为青黄土,沟干泥和黄泥头,最小为夹沙泥。应用磷吸附指标与“磷肥指标”来预测土壤需磷量,初步试验是可行的,但实际应用还需进一步试验研究。  相似文献   

Antitermitic activity of leaf essential oils and components from Cinnamomum osmophleum     

Chang ST  Cheng SS 《Journal of agricultural and food chemistry》2002,50(6):1389-1392

The antitermitic activities of the essential oils from the leaves of two Cinnamomum osmophloeumclones (A and B) and their chemical ingredients against Coptotermes formosanus Shiraki were investigated according to direct contact application. Results from this experiment have demonstrated that the indigenous cinnamon B leaf essential oil has a more effective antitermitic activity than indigenous cinnamon A leaf essential oil. Furthermore, when cinnamaldehyde, eugenol, and alpha-terpineol are extracted from indigenous cinnamon leaf essential oil and used at the strength of 1 mg/g, their antitermitic effectiveness is much higher than that using indigenous cinnamon leaf essential oil. Among the congeners of cinnamaldehyde examined, cinnamaldehyde has exhibited the strongest termiticidal property.  相似文献   

轮式车辆动力传动系自激振动研究（Ⅰ）——自激振动的机理分析     

郑联珠  贾建章  程悦荪 《农业工程学报》1996,12(4):37-42

研究了轮式车辆动力传动系自激振动的机理。建立了动力传动系力学模型，对振动进行了相平面分析，得出地面附着系数随滑转率的增加而减小的特性是造成车辆传动系自激振动主要原因的结论  相似文献   

用边际分析法确定黄河中游粗泥沙集中来源区          下载免费PDF全文

徐建华  金双彦  张成  林银平 《中国水土保持科学》2006,4(3):1-5

 为进一步寻找并治理对黄河下游主槽淤积危害最严重的粗泥沙集中来源区,根据1960年未建三门峡水库前自然水沙条件下下游河槽淤积物粒径组成,确定出黄河中游粗泥沙集中来源区界定中的粗泥沙界限为0.1mm。利用边际分析法在黄河中游多沙粗沙区确定粗泥沙集中来源区面积为1.88万km2。该面积仅占黄河中游多沙粗沙区面积的23.9%,可产生的全沙、粒径大于0.05mm和0.1 mm的泥沙分别占同期多沙粗沙区相应沙量的34.5%、47.6%和68.5%。由此看出,该区是名副其实的粗泥沙集中来源区。  相似文献   

Bayesian Semiparametric Model for Pathway-Based Analysis with Zero-Inflated Clinical Outcomes     

Lulu Cheng  Inyoung Kim  Herbert Pang 《Journal of Agricultural, Biological & Environmental Statistics》2016,21(4):641-662

In this paper, we propose a semiparametric regression approach for identifying pathways related to zero-inflated clinical outcomes, where a pathway is a gene set derived from prior biological knowledge. Our approach is developed by using a Bayesian hierarchical framework. We model the pathway effect nonparametrically into a zero-inflated Poisson hierarchical regression model with an unknown link function. Nonparametric pathway effect was estimated via a kernel machine, and the unknown link function was estimated by transforming a mixture of the beta cumulative density function. Our approach provides flexible nonparametric settings to describe the complicated association between gene expressions and zero-inflated clinical outcomes. The Metropolis-within-Gibbs sampling algorithm and Bayes factor were adopted to make statistical inferences. Our simulation results support that our semiparametric approach is more accurate and flexible than zero-inflated Poisson regression with the canonical link function, which is especially true when the number of genes is large. The usefulness of our approach is demonstrated through its applications to the Canine data set from Enerson et al. (Toxicol Pathol 34:27–32, 2006). Our approach can also be applied to other settings where a large number of highly correlated predictors are present.Supplementary materials accompanying this paper appear on-line.  相似文献   

机械式空气整根钵苗移栽器的研究     

马旭  马成林  张守勤  孙玉晶  孙廷琮 《农业工程学报》1997,(Z1)

空气整根钵苗全自动移栽机的核心部件是移栽器。采用机械方式完成全自动移栽机的送秧和投苗，简化了现有全自动钵苗移栽机的电动或气动送秧和投苗装置，降低了成本。移栽器的性能试验表明，所研制的移栽器性能良好，适应国内市场需要。  相似文献   

Spatial and seasonal distribution of organic amendments affecting methane emission from Chinese rice fields   总被引：1，自引：0，他引：1  

R. Wassmann  M. Tölg  H. Papen  H. Rennenberg  W. Seiler  D. X. Cheng  M. X. Wang 《Biology and Fertility of Soils》1996,22(3):191-195

The effect of fertilizers on methane emission rates was investigated using an automated closed chamber system in Chinese rice fields (Human Province). Each of three experiments compared two fields treated with a first uniform fertilizer dose and a second fertilizer dose which was different for each of the two fields. The uniform fertilizer doses for both fields in each experiment comprised mineral (experiment 1), organic (experiment 2) and combined mineral plus organic components (experiment 3). In all three experiments the second fertilizer dose comprised organic amendments for field 1 and no organic amendments for field 2. The rate of increase in methane emission with a given amount of organic manure was found to depend on the total amount of organic manure applied. A single dose of organic manure increased the emission rates by factors of 2.7 to 4.1 as compared to fields without organic manure (experiment 1). In rice fields that had already been treated with organic manure, the application of a second dose of organic manure only slightly enhanced the emission rates in experiment 2 by factors of 1.1 to 1.5 and showed no detectable increase in experiment 3. The net reduction achieved by separation of organic and mineral fertilizers was maximized by concentrating the organic amendments in the season with low emission rates, i.e. early rice, and using exclusively mineral fertilizers on late rice when emission rates were generally higher. This distribution pattern, which was not associated with significant yield losses, resulted in an annual methane emission corresponding to only 56% of the methane emitted from fields treated with blended fertilizers.  相似文献   

Enzymatic activities in constructed wetlands and di-n-butyl phthalate (DBP) biodegradation     

Q.H. Zhou  Z.B. Wu  S.P. Cheng  G.P. Fu 《Soil biology & biochemistry》2005,37(8):1454-1459

The bioaccumulation of phthalate acid esters (PAEs) from industrial products and their mutagenic action has been suggested to be a potential threat to human health. The effects of the most frequently identified PAE, Di-n-butyl phthalate (DBP), and its biodegradation, were examined by comparison of two small scale plots (SSP) of integrated vertical-flow constructed wetlands. The influent DBP concentration was 9.84 mg l⁻¹ in the treatment plot and the control plot received no DBP. Soil enzymatic activities of dehydrogenase, catalase, protease, phosphatase, urease, cellulase, β-glucosidase, were measured in the two SSP after DBP application for 1 month and 2 months, and 1 month after the final application. Both treatment and control had significantly higher enzyme activity in the surface soil than in the subsurface soil (P<0.001) and greater enzyme activity in the down-flow chamber than in the up-flow chamber (P<0.05). In the constructed wetlands, DBP enhanced the activities of dehydrogenase, catalase, protease, phosphatase and inhibited the activities of urease, cellulase and β-glucosidase. However, urease, cellulase, β-glucosidase activities were restored 1 month following the final DBP addition. Degradation of DBP was greater in the surface soil and was reduced in sterile soil, indicating that this process may be mediated by aerobic microorgansims. DBP degradation fitted a first-order model, and the kinetic equation showed that the rate constant was 0.50 and 0.17 d⁻¹, the half-life was 1.39 and 4.02 d, and the r² was 0.99 and 0.98, in surface and subsurface soil, respectively. These results indicate that constructed wetlands are able to biodegrade organic PAEs such as DBP.  相似文献   

Cadmium and other heavy metals in sea-skaters     

Lanna Cheng  George V. Alexander  Paul J. Franco 《Water, air, and soil pollution》1976,6(1):33-38

Exceptionally high concentrations of Cd (100 to 200 ppm dry weight) were found in samples of Halobates collected off Baja California. In contrast, no detectable Cd was found in Rheumatobates collected from mangrove lagoons in the Gulf of California. Concentrations of five other heavy metals in the two marine insects are also presented.  相似文献   

植物物料的化学组成和腐解条件对新形成腐殖质的影响   总被引：12，自引：1，他引：12  

程励励  文启孝  吴顺令  徐宁 《土壤学报》1981,18(4):360-367

植物物料的某些化学组成分与其腐解产物很相似,迄今还没有一种方法能够把两者清楚地分别开来。这为腐解过程的研究带来了很多困难。例如,已经证明,用碱液作为提取剂时,进入溶液的不仅有腐殖物质,而且也有植物物质^[8],因而所得到的样品不具有很好的代表性;另一方面,由于不能将植物物料与其腐解产物加以区分,甚至连单位重量的植物物料分解一定时期后生成了多少腐殖物质也不能较准确地知道,直到现今,人们仍不得不以残留碳量来作为估量不同植物物料对土壤有机质含量贡献大小的指标。  相似文献