农田作物层生态因子的研究方法

作者总结十几年田间试验观测和研究成果，提出了农田作物层生态因子这一研究领域的研究内容、田间观测小区布置、使用仪器及观测方法等。     

农田作物层生态因子的研究方法

作者总结十几年田间试验观测和研究成果，提出了农田作物层生态因子这一研究领域的研究内容、田间观测小区布置、使用仪器及观测方法等。     

作物施硫生态效应研究

通过田间试验和盆栽试验研究了小白菜和油菜在不同的土壤类型、肥料品种和不同施肥量条件下的生态效应 ,结果表明施用硫肥能促进作物生长、提高其干重生物量和含硫量 ,但施用石膏效果更佳 ,并随施肥量增加 ,效果也增强。盆栽试验中 ,同一处理油菜干重生物量和含硫量都表现为黄棕壤 >红壤 >灰潮土。施用单质硫能提高土壤中的有效硫 ,有利于改变土壤缺硫状况。缺硫土壤中油菜表现出花期延迟、花粉粒发育不全等。     

旱地作物群体生理生态几个问题的探讨

在黄土高原旱地小麦生产实践的基础上，简述了作物群体生理生态研究方法、根系生理生态、群体自动调节机制、叶面积发育动态以及群体光合生理生态等方面的问题。     

旱地作物群体生理生态几个问题的探讨

在黄土高原旱地小麦生产实践的基础上，阐述了作物群体生理生态研究方法、根系生理生态、群体自动调节机制、叶面积发育动态以及群体光合生理生态等方面的问题．     

场平工程的水土保持生态防护

华南地区降雨量大,若没有相应的防护措施,施工动土后会造成严重的水土流失,影响项目区周边环境,为有效降低场平施工对自然生态环境的破坏和对周边环境的影响,必须对项目区实施水土生态防护。以华南山丘地区场平工程为例,围绕华南山丘地区场平工程建设造成的水土生态破坏,探讨性地提出了该区域场平工程水土生态防护的重要环节。     

农田长期生态过程的长期试验研究进展与展望

长期试验是研究农田长期生态过程及其环境效应和调控措施的重要手段.本文综述了国际上重要农业长期试验的研究发展趋势,分析了农业长期试验的重要作用,然后分析了国内农业长期试验网的发展现状,提出了未来发展的建议.农业长期试验的发展主要表现在长期农业生态和环境过程的研究领域不断扩展、长期试验成为多学科交叉研究平台和应用研究平台.国内建立了两个主要的农业长期试验网络,重点开展了水分和养分的长期试验.目前农业长期试验网络需要在区域尺度上加强农业、环境和生物科学的交叉研究;扩展试验地面积,完善试验设计;完善分析测试方法和样品、数据的保存系统.国家需要制定和实施稳定农业长期试验研究的管理和经费支持政策.     

Application of drainage theory in the field

Abstract. The prediction of water-table levels from groundwater theory for a drainage system in a uniform homogeneous soil was tested in an existing field system. Specially designed meters recorded water-table heights and drain discharge with time. A comprehensive hydraulic conductivity survey was made below the water table.
The results agreed with theory for water-table heights up to about 300 mm above the mean drain level. The drainage above that level was larger than predicted, either because of an increased hydraulic conductivity (which could have been produced by subsoiling the previous year and would not have been picked up by die hydraulic conductivity measurements), or because of the presence of an older shallower lateral drainage system, broken and blocked, that was discovered during the work.
Attention is drawn to the inadequacies of dip-wells for monitoring rapid changes in water-table levels and to the problem of sample size in hydraulic conductivity measurements, which if too small can lead to apparent variability.     

动物微生态营养理论在生态畜牧业中的应用

阐述了动物微生态营养学胃肠道微生态理论、胃肠道微生物的生理作用、胃肠道微生物对营养物质的消化代谢、微生态制剂对胃肠道微生物的调控等,并讨论了今后微生态营养学的研究重点。     

流域生态需水的理论及计算研究进展

生态需水是生态水文学的重要研究内容之一.该文分析了生态需水国内外研究进展,在辨识生态需水及其相关概念的基础上,该文认为广义的生态需水是在一定生态目标下,维持相应时空范围内生态系统水分平衡所需要的总水量,而狭义的生态需水是一定的生态目标下,为维持生态系统正常生态与环境功能所需要补充的径流性水资源量.生态需水研究涉及陆地和水域生态系统,该文重点探讨了河流、湿地湖泊等水域生态系统以及陆地植被(包含农田)生态需水理论研究现状,综述了个生态系统生态需水主要计算方法.生态需水研究应加强基础理论研究、生态需水量化方法以及耦合方法研究,尤其是不同生态系统目标下生态需水量的分析还需进一步探讨.     

Growth responses of cereal crops to organic nitrogen in the field

Eleven rice varieties differing in grain size were grown under controlled environmental conditions during the grain-filling period. The grain weight of upper grains in a panicle was examined at successive stages of growth during the grain-filling period. The effect of temperature on the rate and the duration of the period of grain-filling was determined using Khao Lo, a large-grain variety, and Bom Dia, a small-grain variety. Both the grain-filling rate and duration of the period of grain-filling differed among rice varieties and were positively and significantly correlated with the grain size. The duration of the grain-filling period from flowering to the time when almost maximum grain weight was attained ranged from 12 days at 32/24°C in Bom Dia to 36 days at 20/12°C in Khao Lo. The grain-filling rate was low in small-grain varieties, and generally increased with increasing grain size.

By lowering the temperature, the grain-filling rate decreased, the duration of the grain-filling period increased but the grain weight was almost constant.

Weight per grain was closely correlated with hull size. No relationship was found between weight per grain and nitrogen percentage of brown rice.     

分形理论在土壤大孔隙研究中的应用及其展望

土壤大孔隙是普遍存在的现象 ,而非例外 ,它们使水及溶质快速穿过土壤 ,确定大孔隙大小分布需要大量的野外和室内实验。本文在对分形理论概念进行简要阐述的基础上 ,介绍了分形理论在大孔隙研究中所取得的成果 ,结果表明应用分形理论确定土壤大孔隙性质是一种省时、省力和具有广泛代表性的方法 ,最后对分形理论在土壤大孔隙研究中应用前景作了展望。     

分形理论在土壤大了忆隙研究中的应用及其展望

土壤大孔隙是普遍存在的现象，而非例外，它们使水及溶质快速穿过土壤，确定大孔隙大小分布需要大量的野外和室内实验。本在对分形理论概念进行简要阐述的基础上，介绍了分形理论在大孔隙研究中所取得的成果，结果表明应用分形理论确定土壤大孔隙性质是一种省时、省力和具有广泛代表性的方法，最后对分形理论在土壤大孔隙研究中应用前景作了展望。     

Modelling production of field crops and its requirements

Simulation models are being developed that enable quantitative estimates of the growth and production of the main agricultural crops under a wide range of weather and soil conditions. For this purpose, several hierarchically ordered production situations are distinguished in such a way that the results of simulations on one hierarchical situation are used as input for the calculations of another. For the highest hierarchical production situation, water and plant nutrients are optimally available; in the next situation water may be limiting at times, whereas in further situations limited supplies of the main plant nutrients are also taken into account. The reclamation activities and the yield-increasing inputs that are needed to achieve the simulated yield levels for the various situations are estimated.

The weather data and the physical soil data that are needed for the calculations in the first two hierarchical production situations are specified. It is shown that environmental heterogeneity contributes considerably to the complexity of the problem and that especially the averaging of weather data over time and soil data over space leads to distortion or even destruction of data. To avoid this, the data from the original observation sites should remain accessible at all times. The easy accessibility of computers and data base management systems implies that there is no excuse anymore to average first and then calculate, instead of the other way round.     

Does transport of water to roots limit water uptake of field crops?

The question was examined under which conditions the water extraction rate of plant roots in the field can be limited by water transport to the roots. For this purpose we used a numerical solution of the single root model. Scenario calculations were carried out in order to investigate the general model behaviour. A sensitivity analysis showed that initial volumetric water content and root length density are of greater importance than root diameter in determining the maximum water transport rate to the roots. Data from a field experiment were taken, describing root length density, volumetric water content and water uptake rates under oats (Avena saliva L.) and faba beans (Vicia faba L.) as model input parameters. With this data the model calculated the water content difference between the bulk soil and the root surface which is necessary to induce a water flow to the roots matching the observed water uptake rate. Root length densities below the grain legume crop faba beans are one order of magnitude lower compared to that of the cereal crop oats. The therefore higher specific water influx rates of faba beans roots resulted in a higher decrease in water content near the root surface. However, water uptake by faba beans was controlled by the water flow towards the roots probably only in deeper soil layers with very low root length density. For the given conditions no transport limitation of water uptake was calculated, when rooting densities were higher than about 0.1 cm.cm^?3.     

Limitations of crystal field theory applied to sedimentary systems

Crystal field theory has previously been applied to the sorption of ions from aqueous solution by manganese oxide minerals. This paper emphasises the need to consider the overall free-energy change of the appropriate reaction and not just that relatively minor contribution arising from changes in crystal field stabilisation energy.     

Derivation and interpretation of hazard quotients to assess ecological risks from the cultivation of insect-resistant transgenic crops

Cost-effective and rigorous risk assessments for chemicals may be based on hazard quotients (HQs): the ratio of a measure of exposure to a substance and a measure of the effect of that substance. HQs have been used for many years in ecological risk assessments for the use of synthetic pesticides in agriculture, and methods for calculating pesticide HQs have been adapted for use with transgenic crops. This paper describes how laboratory methods for assessing the ecotoxicological effects of synthetic pesticides have been modified for the measurement of effects of insecticidal proteins, and how these effect measures are combined with exposure estimates to derive HQs for assessing the ecological risks from the cultivation of insect-resistant transgenic crops. The potential for ecological modeling to inform the design of laboratory effects tests for insecticidal proteins is also discussed.