基于Mega16的灌溉自动控制系统的设计

为了降低灌溉自动控制系统的成本,增强其实用性,研究设计了一种基于Mega16的灌溉自动控制系统.在3种质地不同的土壤中,对自制的基于电导原理的土壤水分传感器进行了标定试验.结果表明,在同一土壤类型和同样的耕作条件下,土壤的含盐量保持基本不变,土壤的电导率和土壤的体积含水率之间近似成线性关系.该灌溉自动控制系统能实时监测土壤水分,并进行及时和足量的灌溉.     

不同水氮对果树幼苗叶片导水特性的影响

果树苗叶片导水率受温度的影响成单峰或双峰的变化;水分对果树幼苗叶片面积、叶片导水率有显著的影响,叶片面积、叶片导水率随着土壤水分的升高而增加;施氮肥对梨树和桃树幼苗叶片导水率有显著的影响,桃树和梨树叶片面积,叶片导水率都是随着施氮量的增加而增加;3种果树幼苗叶片导水率与叶片面积都成线性增加关系。     

储存玉米膜脂过氧化与生理指标的研究

【目的】研究储存玉米品质变化的生理生化机制,寻找评判玉米储存品质的指标。【方法】对同一区域不同储存年限玉米样品的过氧化氢酶（CAT）活性、过氧化物酶（POD）活性、电导率、丙二醛（MDA）等4个细胞膜脂过氧化指标和生活力、发芽率、呼吸强度第3个生理指标进行研究。【结果】随储存时间的延长,MDA含量增加,细胞质膜透性增大,保护酶类活性均逐渐降低;生活力、发芽率、呼吸强度呈极显著相关性（P＜0.01）,4个膜质损伤指标与3个生理指标呈显著和极显著的相关性。【结论】自由基损伤导致的玉米籽粒内部抗氧化酶活性的降低、细胞膜质过氧化程度的加深及细胞膜透性的增加是储存玉米品质变化的重要因素。     

The effects of electrical discharge on the mechanical properties of <Emphasis Type="Italic">Bombyx mori</Emphasis> silk fibroin

Bombyx Mori is a representative of natural fibers which is known for its mechanical stability. In this study, electrical discharge of the fibers exposed to different voltages for certain periods was examined and mechanical lifetime was measured and also the structure parameters U _o and γ were calculated. We observed that crosslinks might be formed at the silk fibers exposed to high voltages and as a result, fibers become more resistant to mechanical effects.     

干旱区葡萄园漫灌和滴灌压盐效果比较

针对干旱区葡萄园春季压盐问题,通过对漫灌和滴灌两种不同的压盐方式下土壤剖面不同深度电导率测定,研究比较了两种方式的压盐效果.结果表明,大水漫灌压盐效果显著,在灌水量1 500 m3/hm2时垂直压盐深度达100～120 cm.而滴灌方式压盐时,灌水量为600 m3/hm2即可以在以滴头为中心的水平半径200 cm、深度60 cm的半椭球状土体内形成盐分淡化区,从而满足葡萄生长需要.但要注意如果是长期的滴灌洗盐必然在田间形成条带状的盐分淡化区和集盐区.     

两个高粱品种及其三系之种子老化中发芽及活力变化

以623×276、7501×283高粱杂交种及其三系亲本种子为材料,采用人工加速老化的方法,研究了种子在老化过程中发芽、种子活力、电导率的变化,结果表明：（1）（54±1）℃高温、高湿（100%相对湿度）密闭处理,时间低于36h时,种子的多项发芽指标、种子活力下降不明显。当处理达24h时,623 ×276、623B、283R的多项发芽指标和种子活力比其对照明显升高。处理达36h时623A比其对照也明显升高。（2）种子在老化过程中,随老化处理时间的延长种子的电导率并不一定等速率升高,在某处理时间段则下降。（3）从种子的发芽,活力、电导率变化综合分析,两个品种及其三系种子耐老能力存在差异,632×276、623A、623B、283R、7501×283相对较耐老化而其它三系种子抗老化能力较弱。     

管道保温技术的探讨

作者通过五大方面对管道保温技术进行分析探讨,并提出在施工过程中应注意的几点事项。     

Porosity and soil water properties of Caribbean volcanic ash soils

Abstract. Volcanic ash soils are generally recognized as soils with excellent and stable physical properties. Here we characterized the porosity and water properties of volcanic ash Andosols and Nitisols from Guadeloupe in contrasting banana systems: (1) perennial crop without mechanization, (2) mechanized and regularly replanted crop. Desiccation from 1 kPa to 1550 kPa moisture tension leads to significant shrinkage in the Andosol, representing a 50% reduction of the void space. The clayey Nitisol exhibited limited shrinkage. Soil clods from the mechanized plots had a significantly smaller macroporosity than that from perennial plots. The soil hydraulic conductivity was also drastically reduced in the compacted layers of the mechanized plots. However, Nitisols appeared to be less affected than Andosols. Laboratory compression tests showed that both soils were susceptible to compaction at soil moisture close to field capacity. The shrinkage properties of the Andosol were due to microaggregation of non-crystalline components upon drying. The relative stability of the macroporosity in the Nitisol was probably related to the presence of stable microaggregates made of halloysite and iron oxide. Two major processes promote soil structure degradation in the Andosol under mechanized banana cropping, surface desiccation and soil compaction. They are both induced by repeated tillage after clearing.     

三倍体毛白杨无性系木材热学性质变异初探

该文对三倍体毛白杨无性系木材的热学性质进行了研究 ,结果表明热学性质在无性系间存在显著差异 .比热系数、导热系数和导温系数的无性系重复力分别为 0 5 9,0 77和 0 6 2 ,表明三倍体毛白杨无性系木材的热学性质受到较强的遗传控制 .热学性质与木材密度呈正相关 ,导热系数与木材密度达到极显著相关 ,木材密度与导热系数、导温系数和比热系数的相关系数分别为 0 810 0 ,0 5 778和 0 0 938.     

Changes in the properties of a Vertisol and responses of wheat after compaction with harvester traffic

Soil compaction has been recognised as the greatest problem in terms of damage to Australia’s soil resource. Compaction by tractor and harvester tyres, related to trafficking of wet soil, is one source of the problem. In this paper an array of soil properties was measured before and immediately after the application of a known compaction force to a wet Vertisol. A local grain harvester was used on soil that was just trafficable; a common scenario at harvest. The primary aim was to determine the changes in various soil properties in order to provide a “benchmark” against which the effectiveness of future remedial treatments could be evaluated. A secondary aim was a comparison of the measurements’ efficiency to assess a soil’s structural degradation status. Also assessed was the subsequent effect of the applied compaction on wheat growth and yield in the following cropping season. Nine of the soil properties measured gave statistically significant differences as a result of the soil compaction. Differences were mostly restricted to the top 0.2 m of the soil. The greatest measured depth of effect was decreased soil porosity to 0.4 m measured from intact soil clods. There was 72% emergence of the wheat crop planted into the compact soil and 93% in the uncompact soil. Wheat yield, however, was not affected by the compaction. This may demonstrate that wheat, growing on a full profile of stored soil water as did the current crop, may be little affected by compaction. Also, wheat may have potential to facilitate rapid repair of the damage in a Vertisol such as the current soil by drying the topsoil between rainfall events so increasing shrinking and swelling cycles. If this is true, then sowing a suitable crop species in a Vertisol may be a better option than tillage for repairing compaction damage by agricultural traffic.