A comparative analysis of water application and energy consumption at the irrigated field level

Most government policies and community perception of the irrigation sector promotes the conversion from gravity-fed to pressurised irrigation methods as a way of reducing water consumption by the irrigation sector. However, optimising for one aspect of a system can have unintended resource and environmental consequences e.g. an increase in energy consumption patterns of irrigated crops. Two Australian irrigation areas were studied: a surface-water supplied region in New South Wales; and a groundwater dependent region in South Australia. The water and energy budgets for crop production from land preparation to harvest were quantified on several farms. Converting from flood to pressurised systems resulted in a reduction in water application of between 10% and 66%. However, in the surface-water supplied region, it also resulted in energy consumption being increased by up to 163%. In the groundwater dependent region, energy consumption was reduced by 12% to 44%. There is potential to reduce energy consumption due to increased water use efficiency, resulting in less water being pumped due to efficiency gains. Therefore, to optimise energy and water use, it is recommended that pressurised irrigation systems be used in areas requiring pressurised extraction of groundwater, while efficient gravity based irrigation methods, coupled with good management practices, be promoted in surface-water supplied areas.     

退耕还林后群落演替及其α多样性分析

研究了陕西省安塞县退耕还林后7种植被类型下的植被恢复情况、物种多样性特征以及相应生物量。结果表明,退耕还林工程促进了植被的正向演替;柠条是速生树种,赖草为原初植被的建群种;天然草地是由赖草、狗娃花、铁杆蒿共同组成建群种。灌木树种好于乔木树种,其中沙棘表现最好,多样性指数最大,而山杏多样性较差。在草本层及枯落物层中,柠条表现最为优秀,更有利形成乔木-草本-枯落物复合体。增强截留能力。     

从宁夏原州区的调查看退耕还林政策的不足

退耕还林政策实施5年来成效明显，但还存在一些问题。国家放缓退耕还林进度，检讨政策不足十分必要。依据在宁夏原州区各相关部门和73个农户的实地调查，提出了退耕还林政策4个方面的问题和初步改进建议。即补助标准总体较高，长期大面积补偿，国力难以支撑，还会扭曲退耕还林还草的目标；退耕补助期限过短，在补助到期之后与退耕地见效之前的过渡期太长，不利于巩固退耕还林成果；粮食补贴政策的变化不利于稳定退耕农户的生计；退耕还林地产权安排仍显僵硬，农民受益没有保障。     

土壤微生物生物量熏蒸提取法中转换系数K_(EC)的测定研究

本文综述了熏蒸提取法中用于计算土壤微生物生物量时所需的转换系数KEC的测定方法 ,并对现有的各种方法的应用性作了简要的评价 ;同时指出了目前常采用的KEC值在使用上应注意的事项     

罗曼蛋鸡饲粮养分转化率的研究

对合肥市蜀山种鸡场 2 0 0只 40～ 44周龄罗曼蛋鸡日采食饲粮量及养分量和日产蛋成分量等进行了 3 4d的实测 ,在此基础上 ,测算了鸡对饲粮主要养分的转化率 ;并考察了温、湿度因子对其影响。结果表明 :温度对产蛋率、DM、CP、EE、Sac、Ash、Ca、P、Lys、Met、Trp、Thr、Val、Phe、Ile、Arg、His转化率影响显著 (P <0 .0 5 )或极显著 (P <0 .0 1) ;对只日采食饲粮、料蛋比、Leu转化率影响不显著 (P >0 .0 5 ) ;湿度对上述指标观测值的影响均不显著 (P >0 .0 5 )。     

Biomass expansion factors for Sitka spruce (<Emphasis Type="Italic">Picea sitchensis</Emphasis> (Bong.) Carr.) in Ireland

The assessment of a forest resource in national inventories provides a firm basis for the calculation of biomass and carbon (C) stocks of forests. Biomass expansion factors (BEFs) and conversion factors provide a robust and simple method of converting from forest tree stem volume to total forest biomass. These factors should be constructed on the basis of nationally specific data in order to take account of regional differences in growth rates, management practices, etc. The objective of this study is to improve the accuracy of biomass estimation by calculating a range of age-dependant BEFs from representative data that more accurately describe the allometry of present forests. The results from this study show that the allocation of biomass to compartments in forest stands and throughout a rotation varies considerably, and that the use of BEFs for the calculation of C stocks in forests of sub-timber dimensions is highly impractical.

农牧变迁与科尔沁蒙古族农民的节水灌溉技术选择

文章以内蒙古通辽市白村为个案,主要从农牧变迁的视角对科尔沁蒙古族乡村地区节水灌溉技术推广困难的问题进行探究.研究发现,在科尔沁蒙古族乡村社会由半农半牧向纯农耕文明的转变过程中,由于特殊的社会文化传统和生计模式,从而形成独特的技术需求,造成节水灌溉技术推广困难.因此,在一个灌溉历史并不长的蒙古族聚居地区,需要寻找到现代农业技术与本土知识体系的最佳结合点.     

城市边缘区土地利用与土地覆被变化特点研究——以济南市长清区为例

在Arcview3.3和Fragstats3.3的支持下,分别探讨了土地利用的用途转移变化特点;运用景观生态学的原理和方法,对济南市长清区土地利用景观格局的变化特点进行了分析,二者结合研究,可以更好地反映城市边缘区的土地利用特点。结果表明,长清区土地利用的变化较大,整体上突出表现为林地、耕地面积增加,未利用土地迅速减少;景观整体的多样性相对较小,平均斑块分维数和优势度有所增加,景观聚合度增强,有单一化的趋势,结构有待于进一步优化。     

苜蓿中华根瘤菌电转条件的优化

为了研究苜蓿中华根瘤菌电转化的条件,通过对不同的细胞生长周期、复苏缓冲液、电转缓冲液、电场强度和电阻对电转率影响程度来作出变化曲线,以确定电转化的最优条件,从而提高苜蓿中华根瘤菌电转化率.结果表明细胞的对数生长初期、复苏缓冲液Ⅴ、电转缓冲液Ⅳ、23 kv/cm和200Ω适合作为苜蓿中华根瘤菌电转的条件.     

不同光照日周期对肉用仔鸡生产性能影响的研究

本试验利用3126只美·爱拔益加AA肉用仔鸡,在自行设计的间歇光照制的环境中,观测不同光照日周期及光照强度对21～56日龄肉用仔鸡生产性能的影响。试验结果表明:在存活率,饲料利用率及出栏群平均个体重三方面,采用间歇光照制及光照强度为5勒克司的第一、二试验组优于连续24小时光照日周期及光照强度2。勒克司的对照组。其中,采用光照日周期为1L:3D,5勒克司光照管理程序的第一试验组优于光照日周期为1L:1.5D、5勒克司光照管理程序的第二组。