江西省适宜种植能源作物的边际土地资源分析及评价

通过调查分析得出江西省宜能边际土地面积131．2万hm^2。,其中冬闲田面积79．1万hm^2,宜能荒地面积52．1万hm^2。摸清了江西省宜能边际土地资源分布状况。对边际土地中的宜能荒地资源进行了单项限制因素等级评价和综合等级评价。全省宜能荒地综合分级结果为：Ⅰ等宜能荒地9．5万hm^2。,Ⅱ等17．2万hm^2,Ⅲ等25．4万hm^2。。在此基础上,提出了开发利用江西省宜能边际土地资源的若干建议。     

Comparative affects of blending,intera/inter-seasonal cyclic uses of alkali and good quality waters on soil properties and yields of paddy and wheat

Degradation of soils irrigated with the ground waters having residual alkalinity constitutes a major threat to irrigated agriculture in semi-arid parts especially the South Asia. Paddy–wheat has come to stay as the major crop rotation in the afflicted areas, which is either irrigated solely with alkali waters (AW) or combined with good quality water supplies through canal networks. Therefore, to develop appropriate conjunctive use strategies for the latter situations, response of paddy and wheat was evaluated to the combined use of a good quality water (GW, EC_iw 0.5, RSC nil) and that having residual alkalinity (AW, EC_w 2.3 dS m⁻¹, RSC 11.3 mequiv L⁻¹, SAR_w 15 mmol L^0.5) for 6 years (1997–2003) in lysimeters (2.0 m deep, 0.9 m i.d., with drainage outlets at the bottom) filled in with a sandy loam soil (pH 7.8, ESP 5.3). Increase in soil pH (8.71), salinity (3.8 dS m⁻¹) and sodicity (ESP 27.3) as a consequence of irrigation with alkali water markedly affected the yields of both the crops. The sustainability yield index (SYI) was 0.522 and 0.793 for paddy and wheat, respectively, indicating the sensitivity of the former to the use of alkali water. Keeping the AW input to be similar through irrigations, the SYI for paddy with blending of GW and AW in the ratio of 2:1, 1:1 and 1:2 was 0.732, 0.708 and 0.678, respectively, when compared with 0.751, 0.729 and 0.701 under intera-seasonal cyclic uses. Similarly, the SYI of wheat ranged between 0.821–0.907 and 0.853–0.949 with blending and cyclic uses of the two waters, indicating thereby a yield advantage with the latter. When the two waters were rotated inter-seasonally, the dilution effects of monsoon rains helped to induce greater use of AW for paddy. The overall deterioration in soil properties under different modes was related to proportion of AW applied. It was concluded that the alternating good quality and alkali waters could be a better way to alleviate sodicity problems caused with the use of alkali water alone.     

"无标底招标"面面观

近年来,就浙江、沈阳和南京等地对建筑市场试行“无标底招标”执行的结果来看,“无标底招标”有着无法替代的优点,包括:降低投资成本,提高工程质量;规范有形建筑市场,体现招投标的公平、公正性;提高施工企业内部管理水平和自身素质及有利于强化合同管理等几个方面。运作之初虽会产生这样那样的弊端,但随着我国“入世”及与国际惯例的接轨,将会使“无标底招标” 成为招投标市场的主流。     

Are herbicides a once in a century method of weed control?

The efficacy of any pesticide is an exhaustible resource that can be depleted over time. For decades, the dominant paradigm – that weed mobility is low relative to insect pests and pathogens, that there is an ample stream of new weed control technologies in the commercial pipeline, and that technology suppliers have sufficient economic incentives and market power to delay resistance – supported a laissez faire approach to herbicide resistance management. Earlier market data bolstered the belief that private incentives and voluntary actions were sufficient to manage resistance. Yet, there has been a steady growth in resistant weeds, while no new commercial herbicide modes of action (MOAs) have been discovered in 30 years. Industry has introduced new herbicide tolerant crops to increase the applicability of older MOAs. Yet, many weed species are already resistant to these compounds. Recent trends suggest a paradigm shift whereby herbicide resistance may impose greater costs to farmers, the environment, and taxpayers than earlier believed. In developed countries, herbicides have been the dominant method of weed control for half a century. Over the next half‐century, will widespread resistance to multiple MOAs render herbicides obsolete for many major cropping systems? We suggest it would be prudent to consider the implications of such a low‐probability, but high‐cost development. © 2017 Society of Chemical Industry     

森林资源资产评估方法与林龄关系初探

在森林资源资产评估实践中,针对按龄组选择评估方法经常出现评估值连续性差、差异显著的问题,提出了依据林龄选择评估方法的观点。其从科学、公正和可操作性的基本原则出发,通过评估实例计算、分析,初步探讨了利用对比分析法确定林龄临界点,并进一步选择评估方法,力求使评估值具有较强的连续性。同时指出了林龄临界点选择法与标准林分模式相结合在批量资产评估中应用的优势。     

基于耕地保护的农用地流转有效模式研究

耕地保护在农用地流转过程中具有重要的意义。本文认真地分析了农用地流转与耕地保护之间的矛盾冲突,在此基础上,构建了基于耕地保护的农用地流转模式体系,并重点探讨了模式体系中几个有效机制,力图缓解耕地保护与农用地流转之间的矛盾,更好地促进农用地流转。     

黄土丘陵沟壑区水土流失治理模式、治理成本及效益分析——以米脂县高西沟流域为例

通过黄土丘陵沟壑区水土流失治理典型——陕北米脂县高西沟的水土流失治理措施配置模式、治理成本和治理效益分析,认为水土流失治理措施配置模式应由治理目标所决定,不同治理目标指导下的治理模式将产生不同的生态效益和经济效益;针对水土保持效益的多重性、连动性、交叉性和互动性等特点,提出水土保持效益评价原则;依据该原则,估算以粮食自给为目标的治理模式,其投入治理成本是65.70万元/km^2,5-6年内可收回成本;此时治理流域基本达到泥不下坡,水不出沟,林草覆盖率达到40%-50%,粮食自给,年经济收入3 000元/人左右的生态和经济效益。治理区虽全面治理达标,但经济收益仍远低于全国平均水平,单纯依靠水土保持难以达到全面小康,这是值得有关部门应深思的问题。     

真空集热太阳能辅助加热烤房节本增效效果

为实现烤烟烘烤过程中节能减排、降耗增效,将当前推广的大型密集烤房改造成真空集热太阳能辅助加热烤房,并分析真空集热太阳能辅助加热烤房的节能效果。结果表明:使用太阳能辅助加热烤房节能效果较好,对烤后烟叶等级质量的影响不大;中、上部叶每kg干烟节煤率均可达46%,烘烤能耗成本中、上部叶分别降低0.35元/kg和0.29元/kg,烘烤收益分别增加0.84元/kg和0.64元/kg,节本增效效果显著,推广前景可观。     

宁夏引黄自流灌区末级渠系供水成本调查与分析

宁夏引黄灌区干渠以下包括支、斗、农渠工程均由地方管理,在近2年推行的农业供水管理体制改革中,将原乡村集体管理的支斗渠交新组建成立的农民用水者协会管理,进一步规范工程及灌溉管理工作.通过对宁夏引黄自流灌区典型渠道末级渠系供水成本的调查测算,对供水成本构成因素进行定量定性的分析,提出改革末级渠系水价政策和加强末级渠水价管理的措施建议.     

计及无功电源价值的无功费用分摊

提出了一种考虑无功电源价值的无功费用分摊方法.首先基于计及无功电源价值的优化潮流解,将作为无功费用承担对象的电源有功和负荷复功率等值成的节点注入电流源,再将无功费用起源的电源无功等值成的节点并联电抗——“费用电抗”.最后运用复功率电源的支路功率分量算法,推导建立了严格的电流源与费用电抗无功之间的一一对应关系.从而实现费用电抗的无功费用在电源有功和负荷复功率之间的分配.本文方法的主要特点是确保收支平衡、计及P-Q间的耦合影响、适用任何复杂结构和有环流的电网、无需假定或近似.数字仿真结果验证了本文方法的有效性.