玉米秸秆还田时间和还田方式对土壤肥力和作物产量的影响

采用微区和田间两种长期定位试验(12年),探讨了玉米秸秆不同还田时间和还田方式对土壤的培肥作用和对作物产量的影响。研究结果表明,玉米秸秆的还田时间以秋天直接还田并配以适量的微生物快腐剂为好,春天施用腐熟的玉米秸秆不但费工费力,而且对土壤肥力和作物产量没有明显的提高作用;玉米秸秆不同还田方式对土壤肥力和作物产量的影响程度不明显,因此生产上应根据因地制宜的原则,确定适合的还田方式。     

我国主要农区秸秆还田试验总结

本文是 1999年全国 19个省市 10 7份秸秆还田的试验材料的归纳和总结。介绍了我国各主要农区的气候、作物、种植制度、秸秆还田的方法及秸秆还田的增产、改土培肥效果 ,反映了我国各主要农区的秸秆还田现状 ,可为各地的秸秆还田提供参考     

秸秆还田对西藏中部退化农田土壤水分的影响

对西藏中部退化农田进行秸秆还田后的土壤水分效应以及土壤水分与土壤有机质、土壤速效养分的关系进行了探讨,初步结果表明,在西藏高原干旱、半干旱条件下,秸秆直接还田,特别是高茬和秸秆覆盖由于使土壤表层环境得以较好保护,对遏制土壤风蚀、减少土壤水分蒸发具有重要作用。同时,由于土壤水分对土壤环境、土壤过程的深刻影响,土壤有机质、碱解氮、速效钾含量均随之提高,土壤速效磷含量则与土壤含水量呈微弱负相关。     

不同促腐条件下秸秆直接还田对土壤养分时空动态变化的影响

通过两年田间定位试验,研究了冀东地区玉米秸秆连续直接还田对土壤氮素和磷素养分时空动态变化的影响。结果表明,玉米秸秆直接还田可明显提高土壤氮素和磷素供应水平。在调节秸秆C/N15∶1~35∶1范围内,调节秸秆不同C/N未改变秸秆还田后的转化进程,其转化对土壤氮素和磷素时空动态变化的影响亦无明显差异。在调节秸秆C/N的前提下配施促腐剂,使秸秆还田后的转化进程明显加快。     

不同促腐条件下秸秆直接还田对土壤酶活性动态变化的影响

通过两年田间定位试验,研究了冀东地区不同促腐条件下玉米秸秆连续直接还田对土壤酶活性动态变化的影响。结果表明,在小麦各生育期,还田处理总体酶活性均高于单施化肥处理;还田处理中,配施促腐剂处理表现出高于未配施处理的趋势。不同促腐条件下,秸秆直接还田对土壤过氧化氢酶和转化酶活性在小麦各生育期分布态势的影响没有差异,但影响了土壤脲酶和磷酸酶活性在小麦各生育期的分布态势,配施促腐剂使土壤脲酶和磷酸酶活性高峰期出现的时间提前。     

贵州喀斯特山区旱地绿肥聚垅秸秆还土的培肥增产效应研究

在贵州喀斯特山区黄壤和石灰土上进行定位试验 .研究结果表明 ,绿肥聚垅、秸秆还土和绿肥聚垅 秸秆还土均能在一定程度上提高土壤有机质及养分含量 ,改善土壤物理性状 ,提高土壤肥力 ;促进作物 (特别是玉米 )生长发育 ,改善作物经济性状 ,提高产量 ,各处理的年平均粮食复合产量比对照增加36 .3～ 1 1 7.0kg/ 6 6 7m2 ,增加 5.6 8%～ 2 0 .97% .其培肥增产作用明显     

三种秸秆有机肥改良土壤次生盐渍化的效果及生物效应

通过盆栽实验的方法,研究了三种秸秆有机肥对次生盐渍化土壤的EC值、硝酸根离子含量和油菜生物量的影响。结果表明,M1有机肥显著增加油菜的生物量,但在一定程度上增加土壤盐分含量;M2有机肥的效果与M1有机肥效果趋势相似,但增加土壤中的盐分含量的程度要小的多;而施用秸秆肥料M3,在增加油菜生物量的同时显著降低土壤盐分含量,减轻了土壤的次生盐渍化程度。结果表明,三种秸秆有机肥均能提高油菜对盐渍化的耐受能力,增加其生物量。采用M3秸秆有机肥改良土壤盐渍化是一条有效途径,但其最佳施用量与土壤盐渍化程度有关,非盐渍化土壤施用过多M3肥料将降低生物量。     

秸秆深层覆盖对土壤水盐运移及小麦生长的影响

通过对秸秆不同覆盖方式的土柱模拟实验研究表明,秸秆深层覆盖在土壤中形成了一个毛细管障碍层,破坏了土壤毛细管的连续性,明显降低深层土壤水分蒸发,减少了深层土壤盐分向表层的运移;秸秆表层覆盖使土表与空气的接触面变小,利于土壤保水。深层秸秆结合表层秸秆覆盖对土壤的保水效果最好,而且抑制盐分的土壤表聚,减轻土壤盐分对作物生长的胁迫,降低土壤耕层的返盐,保证了作物正常生长。     

施肥对黑土农田土壤全碳、微生物量碳及土壤酶活性的影响

通过对吉林省德惠市中层黑土农田6年定位施肥试验研究表明,施有机肥、秸秆还田 有机肥、秸秆还田 化肥和半量有机肥 化肥处理较单施化肥、未施肥和休闲裸地处理提高了土壤全碳、全氮含量,降低了土壤碳氮比。对玉米播前、抽穗期和收获期土壤微生物量碳测定表明,抽穗期土壤微生物量碳最高,处理间差异显著,且不同采样时期的土壤微生物量碳与土壤全碳含量之间呈高度正相关。对土壤酶活性研究表明,施有机肥较单施化肥、未施肥和休闲裸地处理显著地提高了土壤脲酶、转化酶和过氧化氢酶活性;单施化肥处理对土壤转化酶和过氧化氢酶具有一定的抑制作用;而有机肥、秸秆和化肥之间的配合施用处理的土壤酶活性表现不一致。相关分析显示土壤微生物量碳与土壤酶活性呈显著或极显著正相关。该研究结果表明,长期向中层黑土农田增施有机物,不仅提高了土壤全碳和土壤微生物量碳的含量,而且也提高土壤酶活性,有利于提高土壤养分转化效率,可使黑土质量向健康方向发展。     

不同施肥组合的土壤培肥效果研究

定位试验结果表明,猪厩肥的土壤培肥功能最显著;秸秆对增强土壤供钾能力和改善土壤物理性状具有积极作用,当其与猪厩肥配合施用时培肥效果更突出;化肥对提高作物产量的贡献较大,而对保持提高土壤肥力的作用较小.     

榨菜叶还田对土壤肥力的影响研究

利用盆栽试验和田间试验研究了榨菜叶还田对土壤养分肥力的影响,结果表明,榨菜叶还田处理土壤碱解氮、速效磷、速效钾含量在水稻整个生长期变化较小,水稻生长后期土壤速效N、P、K含量都高于化肥处理;而化肥处理氮磷钾含量变化较大,说明榨菜叶养分供应能够与作物的吸收相互协调,养分供应持续稳定,能满足水稻生长后期对NPK养分的需要,是一种天然的缓释肥料。在水稻生长期,榨菜叶还田能明显的提高土壤肥力,与对照相比,水稻收获后不同处理土壤有机质含量、土壤氮、磷、钾含量,均有所上升,以榨菜叶及其配施化肥处理上升的幅度较大,培肥效果较好。     

Cross-polarized radar backscatter from moist soil

Measurements of radar backscatter from bare soil at 9.0 GHz using a broad beam, with an effective beamwidth of product patterns and an incident angle of about 17° and 30°, respectively, have shown that the sensitivity of the cross-polarized (HV) return to soil moisture content was much higher than that of the like-polarized (HH) one. Analysis of the data shows that the observed HV back scattering power has a dependency of nearly Γ², where Γ is the power reflection coefficient at a plane soil-air interface. This fact suggests that multiple scattering on rough soil surface caused the soil moisture sensitivity of the cross-polarized return to be high.     

非腐解有机物对新修梯(条)田土壤的培肥效果

在新修梯 (条 )田黑垆土上进行的 2 0年秸秆还田定位试验和黄绵土施用非腐解玉米秸秆盆栽试验结果一致表明 ,秸秆直接施用较腐熟土粪更能显著提高土壤松结合态腐殖质和土壤五碳糖、六碳糖的含量 .连年施用秸秆后 ,松结合态腐殖质达到腐殖质总量的 30 %左右 ,松紧腐殖质比值接近 1∶1 ;土壤中与有机质分解转化密切相关的脲酶、转化酶、过氧化氢酶和多酚氧化酶的活性较施化肥和粪肥显著增加 ;同时秸秆有活化土壤磷素和减缓磷吸附固定的作用 .因此 ,施用非腐解有机物是快速提高梯田土壤有机质 ,加快土壤腐殖质更新 ,增产稳产 ,保证农业持续发展的重要培肥措施之一 .     

月面探测器三维可视化方法研究

随着我国探月工程的推进,最后一阶段的任务便是在月面完成无人采样并安全返回.为了能在地面模拟出探测器在月面的实时情况,本研究使用Autodesk 3dsmax创建探测器模型后转成3DS格式的文件,并利用C++和OSG库实现对探测器的三维重构并进行可视化显示,实验结果表明：OSG库能够满足对探测器的可视化显示的需求,为未来"嫦娥五号"工程月面采样的可视化显示提供了一定的参考依据.     

全波形激光雷达和航空影像联合的地物分类

针对机载激光雷达与航空光学影像的互补特性,提出了一种基于多源遥感数据的高精度地物信息提取和分类方法。首先从激光雷达的全波形数据获得数字高程模型(DEM)、地物的正规化数字表面模型(nDSM)和激光雷达回波相对强度信息,从航空数码相机影像获得植被指数信息;然后利用决策树方法进行地物识别。选取“黑河综合遥感联合试验”中的3种典型区域(城市、农田和水体)进行分类,结果表明：该方法能够有效地分离建筑物、高大植被、低矮植被、裸土地以及水泥地等基本地物。     

Measurement of radar backscatter from rough soil surfaces using linear and circular polarizations†

Radar backscatters from loam with a dry bulk density of 0·6g/cm³ have been measured at 9·9 GHz using both linear and circular polarizations. The sensitivity of radar return to soil moisture content has been obtained at five polarization combinations, HH, VV, HV, LR and LL (L and R denote the left-circular and the right-circular polarizations, respectively). Comparison of the moisture sensitivities shows that the sensitivity of HV is the highest among five polarizations and the sensitivity of LL is slightly higher than that of HH, VV and LR. Surface scatter theories are discussed in relation to the moisture sensitivities of five polarizations.     

Estimating the area of stubble burning from the number of active fires detected by satellite

To estimate the area affected by stubble burning in southern Australia, use was made of observations from the MODIS (MODerate resolution Imaging Spectroradiometer) on the Terra and Aqua satellites. The burnt area (BA) was calculated from the number of active fires, known as fire hot spots (FHS) using parameters estimated from a survey of farms in the agricultural area of south-western Australia. The study also served as a ground validation of the capability and limitations of the MODIS sensor and associated algorithm for detection of small agricultural fires.During the period from 1 March to 23 May 2005, 3240 unique FHS associated with stubble burning were detected. The majority of these FHS occurred in the afternoon in the last 3 weeks of April. To estimate the total area of stubble burning associated with these FHS, a survey was sent to 2066 farmers. This survey determined for each farm, the number of fields in which stubble was burnt, average size of field burnt (A), crop types burnt, dates and time of day of burning. Responses were received from 273 farms, 38% of whom reported over 500 stubble burns. The 3240 FHS were intersected with the polygons of the farm boundaries to determine the proportion (P) of stubble burns detected using MODIS. Only 13% (± 3%) of the stubble burns recorded in the farm survey were detected. Average field size burnt was 75 ha (± 6 ha). Total BA was calculated as: BA = A ^? 3240/P, which gave an estimated area of 1.87 million ha. This area was 27% of the total cropped area in south-western Australia. This level of stubble burning was similar to that determined by a 1990s survey in the State of Victoria.Neither cloud cover nor field size was significantly correlated with the low number of stubble fires that were detected. Therefore it was concluded that many stubble burns went undetected because of the lack of coincidence between the time of the MODIS overpass and when stubble burns were initiated. Also the use of additional sensors such as the Advanced Very High Resolution Radiometer (AVHRR) on NOAA satellites with afternoon overpasses would improve the fraction of stubble burns detected.Across the whole of Australia where winter cropping occurs, there was a high correlation (r² = 0.96) between FHS and total cropped area in each State. This provided the basis for extrapolating the field results from south-western Australia, to estimate the total area of stubble burning in southern Australia for 2005.     

Examining the Signaling Effect of E-tailers’ Return Policies

E-tailers normally have more accurate information regarding their products and services than consumers due to the nature of online transactions. To reduce consumers’ concerns of hidden information, e-tailers can use lenient return policies to attempt to signal high product and service quality. This research proposes a model to investigate the signaling effect of two components of return policy, return window—short return window vs. long return window and return depth—full refund vs. partial refund, on product quality and service quality. Data was collected using an online survey and analyzed using structural equation modeling. The results show that both a long return window and a full refund signal high service quality, which then positively affects purchase intention. When it comes to product quality, return window does not have a signaling effect, while the signaling effect of return depth is moderated by service quality.     

二进制翻译中的函数返回类型恢复技术

函数返回类型恢复分为库函数和用户函数返回类型恢复两类。分析IA-64体系结构在函数调用和返回方面的特性得知,用户函数返回类型恢复不是只能从调用者的角度进行分析，还可从被调用者的角度进行分析。综合两种分析方法的优缺点,提出了一种全新的函数返回类型恢复方法。介绍了静态二进制翻译系统ITA中基于控制流和数据流分析的函数返回类型恢复技术，并给出相应的实现算法。由IA-64体系结构的实例验证证明，该方法是一种实用的函数返回类型恢复方法。