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71.
Aerobic rice has been considered a promising rice cultivation system as water scarcity is increasing in the world. This article summarizes the advances in aerobic rice management researches in the North China Plain, focusing on yield formation and its bottleneck. High-yielding and good-quality aerobic rice varieties adapted to aerobic soil conditions have been released officially and adopted by farmers in North China. The varieties Handao 502 and Handao 297 have been recognized as the most promising varieties reaching a yield level ranging 3.5-5.0 t ha-1 with 450-650 mm water input. Compared with lowland rice, water input in aerobic rice was more than 50% lower, and water productivity was 60% higher. Researches on responses of rice cultivars to nitrate nitrogen (N) and ammonium N supplied at early growth stages provided the first evidence for a preference of aerobic rice HD297 for nitrate N supply, compared with the lowland rice variety. Zinc uptake studies demonstrated that introduction of aerobic rice system on calcareous soils may increase zinc deficiency problems. Sink size was identified as the limitation of aerobic rice yield, because its spikelet number m-2 was too low (20000-24 000) compared with the lowland rice. For future research, more attention is suggested to be paid to yield formation focusing on effects of water regimes on tiller dynamics. Understanding of nutrient uptake and response to fertilization effects are also urgently required to establish optimized crop management technology. Additionally, alternative cropping systems based on aerobic rice should be established, and key sustainability and environmental impact issues in the systems need to be identified. 相似文献
72.
本文通过哈尔滨机场高速公路测设中所遇到的平面线形、纵断面设计、排水以及旧路利用等问题 ,提出了在测设中的解决方法 ,为以后的设计提供了有益依据。 相似文献
73.
根据松嫩平原西部水资源复合系统的特征和水资源条件,建立了区域水资源可持续利用评价指标体系。应用投影寻踪技术,采用实码遗传算法优化投影指标函数,将方案多维评价指标值综合为一维投影值,根据投影值的大小实现方案的优选。研究表明,投影寻踪技术可以有效地解决权重的人为干扰,通过优化排序实现对评价结果的定量化表征。 相似文献
74.
复垦对三江平原土壤环境的影响 总被引:4,自引:0,他引:4
Soil environment in Sanjiang Plain has changed greatly because of the reclamation on a large scale The physical and chemical properties of soil have changed ,and soil erosion,soil saline-alkaliztion and soil pollu-tion occurred in some areas ,Thes Problems have obstructed the sustainable development of agriculture.For the sustainable use of soils in Sanjing Plain,in this paper we raise som suggestions and countermasures which might be refereces for experts and departments concerned. 相似文献
75.
三江平原井灌水稻生育期内水分供需平衡状况分析 总被引:1,自引:0,他引:1
对三江平原井灌水稻生育期内水分供需平衡状况进行了分析 ,找出在全生育期内亏水量最大的时期及多年平均数额。并采用经验频率曲线法建立了水稻净灌溉需水量 IN 与频率 P的函数关系 ,可供灌溉用水管理者参考 相似文献
76.
77.
三江平原稻田N_2O通量特征 总被引:3,自引:0,他引:3
利用静态暗箱-气相色谱法于2004年11月-2005年10月对三江平原稻田进行了全年连续田间原位观测。结果表明,三江平原稻田全年N2O平均通量为0.052 mg·m^-2·h^-1;冻融期N2O通量范围为0.008N 0.029 mg·m^-2·h^-1,融冻时排放量显著增加;生长期平均通量为0.059 mg·m^-2·h^-1,施肥后及淹水期间水面落干时各出现了两个明显的N2O排放峰,排水后N2O排放通量较淹水期稍增加,但幅度不大。同时分析了冻融期、生长期N2O通量季节变化特征和日变化特征以及和相关环境因子的关系,分析表明。温度决定了稻田全年N2O排放通量的大小,而水分状况则是影响三江平原稻田N2O排放季节变化特征的主要因素。 相似文献
78.
79.
运用生态学原理和可持续农业的思想,分析了湖南洞庭湖平原和湖北江汉平原(简称两湖平原)湿地的基本特点,提出了合理利用湿地资源和生物资源,通过调节物质的生物循环,促进农业可持续发展的途径。 相似文献
80.
Paul A MorrisNicholas M Hill Edward G ReekieHeather L Hewlin 《Biological conservation》2002,106(1):79-90
Diversity patterns of riparian plant communities have been associated with disturbance. Populations of a diversity of Atlantic Coastal Plain plants occur as disjuncts on shores of large catchment area lakes in Nova Scotia. These lakeshore communities contain rare plants with local, national and global rankings. The populations of rare plants are dynamic and their management requires an understanding of the relationship between disturbance and the survival of rare plants. This present study measured (overwinter wooden dowel removal) and observed disturbance along gradients of catchment area (CA), exposure and depth. In three separate experiments ranging from the landscape to the lake, to the single shoreline level, disturbance was linked to lake CA, exposure and depth, respectively. At all scales, disturbance was positively associated with the presence of rare species. The pattern of rare species richness over the river system was complex; at the within-lake level, the frequency of rare species per site was greatest in the intermediate CA lake while the pool of rare species was greatest in the largest CA lake. The findings focus field efforts on wide, exposed shorelines of large CA lakes where new rare plants continue to be discovered. In addition, the discrepancy between highest frequency of rare plants on intermediate CA lakes and highest species pools of rarities on large CA lakes, reinforces the need for larger protected area systems for the most naturally disturbed ecosystems which often support populations having a high turnover rate but a low site to site frequency. 相似文献