硒酸根与氢氧根离子在可变电荷土壤表面的交换反应: Ⅱ. 氢氧根离子释放的动力学

A self-made constant pH automated titration instrument was used to study the kinetics of hydroxyl release during selenite reacting with variable charge soils. The rate of hydroxyl release was very rapid at the first several minutes, then gradually slowed down, and at last did not change any more. The experimental data was well fitted by the Langmuir kinetic equation, and with increasing selenite concentration or decreasing solution pH, the reaction lasted longer, the maximum of hydroxyl release (x_m) increased, and the binding constant (k) decreased. The time of hydroxyl release with Xuwen latosol was much longer than that with Jinxian red soil.     

Impact of rainfall regime on the decomposition of leaf litter with contrasting quality under subhumid tropical conditions

In alley-cropping systems, hedgerow trees are regularly cut back. Losses of N released from the decomposing prunings are minimized when N release is synchronized with crop N demand. In this study, the sensitivity of the decomposition of Leucaena leucocephala, Senna siamea, and Dactyladenia barteri leaf litter to the nature of the rainfall regime is correlated with the residue quality. The litterbag technique was used to measure decomposition. Four periods of 115 days, each starting at a time when hedgerow trees are normally pruned, were selected and the rain that fell during each of these periods in 1986 was simulated on a day-to-day basis by applying irrigation water on the litterbags. The number of rainfall events was better correlated with the percentage dry matter loss than with the total amount of precipitation. The relationship consisted of two lines. The slope of the first line, indicative of the sensitivity of the decomposition to varying numbers of rainfall events, correlated well with the watersoluble fraction (P<0.05), the C:N ratio (P<0.05), and the polyphenol: N ratio (P<0.01) of the residues. The decomposition process was shown to be dominated by microbial catabolism, rather than leaching. Because the decomposition of the higher quality residues is affected by varying rainfall patterns and because rainfall may often be unpredictable in frequency and intensity, synchronization of N released from a significant part of the decomposing residue with crop N demand may require additional management practices.     

缓/控释肥对小麦增产与提高氮肥利用率的效果研究

以不施氮肥、尿素基施和尿素基追比5:5等3个处理做对照,对3种包膜缓/控释肥处理冬小麦产量、产量相关因子、不同时期植株含氮量及肥料利用率进行了分析比较。结果表明,缓/控肥处理的以上几个指标均接近于尿素基追比5:5处理。与尿素基施相比,包膜缓/控释肥增产10.03%～11.17%,有效穗数和穗粒数增加,返青-拔节期植株含氮量明显提高,氮肥利用率提高了6.18%～11.57%。3种缓/控释肥相比较,产量、产量因子、植株含氮量及肥料利用率没有显著性差异。     

有机酸根对不同土壤组分无机磷生物有效性的影响

A field investigation was conducted to determine the survival and growth rate of eucalyptus (Eucalyptus camaldulensis Dehn.) and guava (Psidium guajava L.) saplings planted in salt-affected soils. The field used was highly saline-sodic in nature with a wide variation in electrical conductivity of the saturated soil extract (ECe), pHs, sodium adsorption ratio (SAR) and gypsum requirement (GR). A randomized complete block design was utilized with three treatments, i.e. T1=plastic container bags totally removed, T2=only the plastic container bag‘s base removed and T3=plastic container bags un-removed. There were 34 and 8 plants in each block for eucalyptus and guava, correspondingly. The survival rates of eucalyptus and guava saplings were greater than 90%. In addition, gain in eucalyptus height was significantly higher in the T1 treatment where the bags were totally removed while for guava height the treatments were not significant. The gain in girth was not significant for both eucalyptus and guava saplings. With eucalyptus the taproot length was greater than the lateral roots while for guava the lateral roots were longer than the taproots. There was a decrease in the salinity-sodicity of the soils for the upper 30 cm depth under both types of vegetation, indicating that the salts had leached down to the B-horizon.     

亲水性聚合物在肥料学中的应用

对亲水性聚合物型肥料进行了总结,对亲水性聚合物进行了分类,并阐述了亲水性聚合物型肥料的种类、亲水性聚合物型肥料的养分释放及其影响因素,最后指出了该类型肥料存在的问题并对前景进行了展望。     

聚乙烯醇/淀粉共聚物包膜材料消泡研究

聚乙烯醇／淀粉共聚物包膜材料在对肥料进行包膜过程中会产生大量的气泡，在肥料表面形成微小孔隙，因此降低了肥料的缓释性能。本试验通过对不同种类的消泡剂消泡效果的研究，削述了消泡剂的消泡机理，并且通过研究确定了改性有机硅型消泡剂和聚二氧化硅型消泡剂消泡效果最好，降低了膜的吸水量和透水性，从而提高了聚乙烯醇／淀粉共聚物包膜肥料的缓释效果。     

缓释复合肥对黄连营养效应的研究

田间试验研究了4种黄连缓释专用复合肥（SRF）对3～5年生黄连产量与药用品质的影响。结果表明,缓释复合肥料较普通复合肥料（CK）显著或极显著提高各年份黄连的生物量与根茎产量，以SRF4与SRF-的增加幅度最大（6．3％～18．7％）。各缓释复合肥处理对不同年份黄连植株地上部和地下部养分含量的影响表现为氮、磷养分含量变化特点相同。钾含量则相反。缓释复合肥的养分比例明显影响不同年份黄连的药用品质，SRF3对3年生和5年生黄连小檗碱、生物碱含量增加明显，4年生黄连则以SRF-的提高作用最大。无论地上部还是地下部，较高的N／P比、N／K比，较低的K／P比均有利于提高不同年份黄连的产量，提出的高产（量）优质处理对应的养分比例可作为高产优质黄连植株营养诊断的重要依据。     

辐射灭菌技术在制药业上的最新应用进展

《60Co中药灭菌标准》发布以来,药品辐射灭菌技术得到广泛应用。本文从辐射剂量控制、药品包装及对功能成分影响等几个方面,介绍了该技术在制药业上的最新应用进展,并针对当前我国药品辐照灭菌存在的主要问题提出具体应对措施。对辐照灭菌技术在保健食品、酶制剂和缓控释胶囊的应用也作了专门介绍。     

辐射不育技术防治柑桔大实蝇的效果

在贵州省惠水县中联桔园(500亩)中,1987年和1989年分别释放56272头和95320头辐射不育柑桔大实蝇,释放比分别为12.5:1和45:1,使柑桔大实蝇虫果率由常年的5—8％下降到0.005％,防治效果十分显著。测得柑桔大实蝇可飞翔扩散1500米远。     

有机酸对污染土壤中镉释放的影响

There is limited information on the release behavior of heavy metals from natural soils by organic acids. Thus, cadmium release, due to two organic acids (tartrate and citrate) that are common in the rhizosphere, from soils polluted by metal smelters or tailings and soils artificially contaminated by adding Cd were analyzed. The presence of tartrate or citrate at a low concentration (≤ 6 mmol L^-1 for tartrate and ≤ 0.5 mmol L^-1 for citrate) inhibited Cd release, whereas the presence of organic acids in high concentrations (≥ 2 mmol L^-1 for citrate and ≥ 15 mmol L^-1 for tartrate) apparently promoted Cd release. Under the same conditions, the Cd release in naturally polluted soils was less than that of artificially contaminated soils. Additionally, as the initial pH rose from 2 to 8 in the presence of citrate, a sequential valley and then peak appeared in the Cd release curve, while in the presence of tartrate the Cd release steadily decreased. In addition, Cd release was clearly enhanced as the electrolyte concentration of KNO₃ or KCl increased in the presence of 2 mmol L^-1 tartrate. Moreover, a higher desorption of Cd was shown with the KCl electrolyte compared to KNO₃ for the same concentration levels. This implied that the bioavailability of heavy metals could be promoted with the addition of suitable types and concentrations of organic acids as well as reasonable field conditions.