小麦水分状况的光反射测量

反射测量可用于对作物的水分状况进行快速而经济的评估.该研究以土壤最大持水量为标准,设65%、52%、39%、32.5%、26%和19.5%共6个水处理水平.小麦叶片光反射的测量用数码相机进行,测量结果用L*a*b*颜色系统进行评估和分析.在该三维系统中,参数a*和b*分别描述绿/红和蓝/黄颜色的比例,参数L*用来描述颜色的浅淡.结果表明,随水胁迫加剧,小麦叶片光反射参数a*(绿/红)和/或b*(蓝/黄)在9个特定波段表现出有规律的增加,植株含水率与光反射参数b*之间呈线性负相关关系,其中与510～780 nm波段的光反射参数b*之间的决定系数r2最大,达到0.95.因此光反射测量可以作为小麦水分状况测量的一个重要工具.     

Semi‐natural grassland biomass for combustion: influence of botanical composition,harvest date and site conditions on fuel composition

Bioenergy generation by combustion is an alternative utilization of biomass from semi‐natural grasslands no longer needed for forage production. Variability of fuel composition affects the suitability of grassland herbage for combustion, in terms of ash‐related problems and harmful emissions of N, S and Cl compounds. A field experiment was established at six semi‐natural grassland sites in southwest Germany to investigate the importance of botanical composition, harvest date and site effects in influencing fuel composition. The first growth at each site was harvested at five dates from June to October. Concentrations of N, S, K, Ca, Mg and ash were lower in grasses than forbs. Between June and October, K concentrations decreased and Ca concentrations increased in grasses and forbs. Ash concentration increased only in grasses, while yields remained stable. Considerable site effects were also found, particularly for K and Cl. The findings are discussed in relation to knowledge of combustion technology. Fuel composition of the investigated grassland biomass was less suitable for combustion than that of perennial energy grasses, but comparable to that of cereal straw. Most critical parameters were high N concentrations, cause of NO_x emissions, and high ash, K and Cl concentrations, responsible for particle emissions, fouling and corrosion. Although combustion of semi‐natural grassland biomass for small‐scale residential boilers cannot be recommended currently, results of this study suggest that utilization in medium‐scale combustion units may offer realistic perspectives, creating synergies between bioenergy production and biodiversity conservation.     

Integrating a simple shading algorithm into CERES-wheat and CERES-maize with particular regard to a changing microclimate within a relay-intercropping system

Wheat/maize related multi-cropping systems are the dominant cropping systems in North China. To improve and adjust those systems, and to study competition effects within intercropping, extended field experiments are necessary. As field experiments are time consuming, laborious and expensive, a viable alternative is the use of crop growth models that can quantify the effects of management practices on crop growth and productivity. Field experiments showed that intercropped maize yielded as high as monocropped maize, and grain yield of intercropped wheat increased by up to 32%. Based on a process-oriented modeling approach, this study focuses on analyzing and modeling competitive relationships in a wheat/maize relay intercropping system with regard to yield, solar radiation and microclimate effects. A simple shading algorithm was applied and integrated into the CERES models, which are part of the DSSAT software shell vs. 4.5. The algorithm developed estimates the proportion of shading as affected by neighbouring plant height. The model was tested to investigate the applicability of this shading algorithm within the CERES models in the simulation of grain yield and dry matter yield of wheat and maize. Model error of grain and dry matter yield for both species was below 10%. There was a tendency for grain yield to be simulated adequately but for dry matter yield to be slightly underestimated. Increased top soil temperature in intercropped wheat increased the mineralization of nitrogen and improved N supply. The wheat/maize system was N efficient. Thus, N dynamics were taken into account for simulation as well as CO₂ dynamics based upon modified wind speed. Wheat border rows were exposed to a higher wind speed until mid-June and to reduced wind speed thereafter. As a result, solar radiation, soil temperature and wind speed differed between monocropping and intercropping and could provide a starting point for simulating intercropping. Microclimate effects are often small, subtle or non-existent, while spatial and climate variability and the heterogeneity of plant populations can be considerable. Quantifying microclimatic effects may prove difficult but should not be neglected when simulating intercropping systems.     

Influence of agronomic factors and extraction rate on the acrylamide contents in yeast-leavened breads

Because the impact of agronomical factors on bakery products quality is still an insufficiently studied field, acrylamide contents of breads produced from flours of nine wheat, two rye, and two spelt varieties harvested in 2003 and 2004 were investigated. It could be demonstrated that acrylamide content in bread strongly depends on the cultivar, with extremes differing by a factor of 5.4 due to marked differences in free asparagine and crude protein contents. Nitrogen fertilization also resulted in elevated amino acid and protein contents, thus increasing acrylamide levels from 10.6 to 55.6 mug/kg. Independent of fertilization, harvest year turned out to be another factor influencing acrylamide formation. Breads produced from 2003 flours showed significantly higher acrylamide contents than those of 2004, which was ascribed to favorable light and temperature conditions during the cultivation period, thus enhancing amino acid and protein contents. Sprouting of the grain also resulted in significantly higher acrylamide levels, which was attributed to elevated enzyme activities and the formation of precursors from protein and starch. Furthermore, bakery products made from flours with higher extraction rates were shown to contain higher acrylamide levels resulting from extracted free asparagine and protein from the aleuron layers of the cereal grain.     

优化施肥和传统施肥对夏玉米生长发育及产量的影响

中国农业大学和德国霍恩海姆大学(Hohenheim University of Germany)中德合作项目"华北平原作物高产高生产力条件下环境可承受的持续农业研究"2000～2001年度北京试验基地研究结果的一部分.试验结果表明,优化施肥和秸秆还田优化施肥夏玉米株高、基部节间直径、同一时期叶面积指数、干物质积累量、穗部基本性状,如穗长、穗粗、秃尖长、产量结构及产量与传统施肥无显著性差异,而氮肥利用率显著提高.在优化施肥条件下,夏玉米棒三叶总叶面积略微减少,生育后期穗位叶叶绿素含量下降稍快,吐丝至收获干物     

育苗移栽夏玉米灌浆特性研究

以夏玉米唐抗5号为材料,研究了移栽、直播和耕后播种夏玉米的子粒灌浆特性.结果表明,灌浆前期(授粉后16d以前),移栽玉米的子粒灌浆速率略低于直播和耕后播种处理;但灌浆中后期的灌浆速率显著高于直播,耕后播种处理的灌浆速率最低.移栽处理各发育时期提前10～15d,从而延长了子粒有效灌浆期的长度.移栽降低株高和穗位高,单位面积的穗数、穗粒数和千粒重均不同程度地提高,从而提高了经济产量.     

Consumers’ beliefs about whole and refined grain products in the UK, Italy and Finland

The objective of this study was to increase our understanding of consumers’ product related expectations that may influence their willingness to use whole grain (WG) foods. Consumers’ beliefs about WG and refined grain (RG) product categories were measured, compared and consumers were segmented based on these beliefs. Data were collected with self-completion questionnaires in the UK (N=552), Italy (N=504), and Finland (N=513).On average, consumers in Finland, Italy and the UK were aware that WG products are healthier than RG products as the WG product category was rated as more nutritionally balanced, healthier, more natural, more filling, releasing energy more slowly and slightly more digestible than the RG product category. However, certain consumer segments did not perceive much difference between whole and RG products in their health-related characteristics suggesting a lack of motivation for increasing WG consumption. This sets a challenge for promoting WG products especially in Italy and the UK, where the respondents were less likely to differentiate between the healthiness of WG and RG products than the Finnish respondents. Differences between the consumer segments and ways of promoting WG consumption are discussed.     

灌溉制度和氮肥对冬小麦粒重的影响

为探讨传统栽培技术和优化栽培技术对小麦粒重的影响，于1999－2000年在中国农业大学中德合作项目北京试验基地进行了包括灌溉，氮肥和秸秆3因素共18个处理组合的田间试验，结果表明：（1）秸秆处理对粒重无明显影响，优化灌溉有利于提高粒重，优化灌溉配合优化施氮肥提高小麦粒重；（2）小麦不同粒位粒重的高低顺序为：第2位粒＞第1位粒＞第3位粒，而且栽培技术无法改变这种差异；（3）施氮对对籽粒胚乳细胞数目的影响取决于土壤水分状况，土壤水分不足时为负效应，否则为正效应，本文从粒重角度建议北京地区种植多穗型和灌浆速度快的小麦品种。     

不同氮效率玉米杂交种的叶光反射研究

培育氮高效的玉米新品种是众多植物育种项目的主要研究领域。反射测量可能用于对作物的氮效率进行快速而经济的评估。本研究以适应低氮的SL (氮高效品种 )和适应高氮的TH (对照品种 )两个玉米杂交种为材料 ,设 0和 1 5 0kgN hm2 两个施氮水平。在播种后 46、62、76、90和 1 0 4d ,用数码相机LEICASIPRO测量玉米叶片的光反射 ,测量结果用L a b 颜色系统进行评估和分析。在这个三维颜色系统中 ,反射参数a 和b 分别描述绿 红和蓝 黄颜色的比例 ,参数L 用来描述颜色的浅淡。结果表明 ,在低氮条件下 ,开花期前后的玉米叶片光反射参数a 和b 在 5 1 0～ 780nm、5 1 6～ 780nm、和 5 4 0～ 780nm 3个特定波段表现出规律性的变化 ,SL 的反射参数a 显著高于TH 的 ,反射参数b 正相反 ,显著低于TH 的b 值。上述结果说明 ,开花期前后的反射测量可以作为玉米氮效率筛选的一个简单、快速而经济的评估工具。