循环水系统孵化斑点叉尾鮰鱼卵试验

<正>针对斑点叉尾鮰早期鱼卵孵化时,早晚温差变化大,水温不稳定,因而孵化率低的问题。2007年自行设计了一套集物理过滤、消     

嘉鱼县建全国乃至亚洲最大的斑点叉尾鮰孵化中心

<正>近年来,嘉鱼县以发展斑点叉尾鮰苗种孵化产业为突破口,着力巩固全国鮰鱼第一县的地位。去年9月,嘉鱼县水产部门以鮰鱼养殖合作社为依托,引资4623万元,在该县鱼岳镇建设三湖渔业有限责任公司斑点叉尾鮰孵化中心。据该县水产部门相关负责人介绍,该中心占地60亩,其     

引发技术对不同温度下番茄种子萌发和幼苗生长的影响

近年来,随着我国经济的快速发展,人民的生活水平也在不断提高,对各种蔬菜的需求量也在不断增加。番茄作为一种具有较高营养价值的蔬菜,在近些年的蔬菜市场受到了人们的欢迎,但在种植番茄的过程中由于受到各种因素的影响,番茄种子的萌发和幼苗生长均会受到限制。本文就引发技术对不同温度下番茄种子萌发和幼苗生长产生的影响进行分析。     

斑点叉尾鮰繁殖技术的研究

<正>斑点叉尾鮰(Ictalurus punctatus)又称沟鲶。于1984年8月由湖北省水产科学研究所首次从美国引进,笔者是鮰鱼研究项目组的主要成员之一。二十几年来,斑点叉尾鮰的养殖在我国得到了很大发展,掀起了一个又一个养殖高潮,养殖面积不断增加,苗种需求不断扩大。现     

斑点叉尾鮰的养殖要点

<正>斑点叉尾鮰的适温范围很广,生长温度为6～37℃,最适生长温度为21～32℃;该鱼在水中溶氧含量为2.5～3毫克/升时能正常生活;pH值范围以6.5～8.9为宜。现将其养殖要点介绍于下:     

东北地区近30年来温度变化的时空差异

[目的]东北地区作为我国响应全球气候变暖最为显著的地区之一,21世纪以来是否与全球及北半球的气候变化一致,发生了变暖趋势减缓或停滞?[方法]为了问答该问题,基于黑吉辽3省71个气象站1981~2010年的气温资料,采用时间序列分析法、克里金插值法,分析东北地区近30年来年际、年代际的年均温和生长季温度的时间变化与空间分布特征,以及冬季温度的数值变化。[结果](1)东北地区30年来年均温在波动中呈上升趋势,3省的变化具有同步性;(2)年均温在1991~2000年的增温区域面积扩大显著,尤其是年均温范围为2~4℃的区域向4~6℃变化,但在2001~2010年,年均温的增加趋势减缓、增温区域较少;(3)生长季温度呈明显的上升趋势,1991~2000年与1981~1990年相比升温幅度达到1.4~1.5℃,2001~2010年与1991~2000年相比达到2.3~2.4℃;(4)生长季温度增温区域有明显北移趋势,变化最大的是生长季温度范围为14~16℃的区域向16~18℃变化;(5)2000年后暖冬年份减少,3省冬季温度的增温幅度减小。[结论]2000年以来东北生长季(夏、秋季)温度仍具有明显的增温趋势,但"暖冬"现象减弱,导致年均温增幅的减缓。     

斑点叉尾鮰病毒病疫苗的制备和使用

<正>斑点叉尾鮰病毒病是流行范围比较广,危害程度比较大,死亡率比较高的流行性疾病。现已报道的斑点叉尾鮰病毒有两种:一种     

虹鳟孵化池、苗种培育池、成鱼养殖池的修建

一、虹鳟的生物学习性.虹鳟属鲑形目、鲑科、鲑属,是一种典型的冷水性鱼类。背部苍青色或黄绿色,腹部灰黄色或银白色。体侧沿侧线中部有一条紫褐色的彩带,一直延伸到尾鳍基部。虹鳟喜欢生活于水质澄清,具有沙砾的河道中上游。生存温度5℃-24℃,适宜水温12℃-18℃,最适水温16℃-18℃。虹鳟对pH值的适应性为6.5-8。     

水霉抑制药物对河川沙塘鳢受精卵孵化的影响

<正>目前河川沙塘鳢的苗种繁育技术还很不完善,主要原因之一是每年的5月中旬(水温20²5℃)是河川沙塘鳢的繁殖季节,河川沙塘鳢受精卵孵化周期较长,此时也正是水霉菌生长繁殖旺季,孵化期内极易受到水霉菌的感染而死亡,苗种生产的规模化进程受到严重影响。本研究在2013年参考相关文献的基础     

经济增长与收入再分配对湖北省农村贫困变动的影响

本文通过对湖北省否受益并相关结论贫困变动由人均收入水平和收入分配不平等程度两个因素共同决定。贫困变动的增长再分配分解，考察1997—2003年间如上两个因素村贫困变动的影响方向和程度，进而分析在经济增长过程中穷人是算和比较基尼系数，考察在此期间农村居民的收入分配状况，得出对农测。     

Population growth,agricultural intensification,induced innovation and natural resource sustainability: An application of neoclassical growth theory

Using a simple neoclassical type growth model including both man-made and natural capital as inputs to production, the theoretical basis for a U-shaped relationship between agricultural intensification and farm household investment in renewable resource capital is established. As development of technology, infrastructure, or markets increase the relative return to investment in man-made capital over natural capital, resource depletion occurs as man-made capital is substituted for lower return natural capital. Once returns are equalized, both man-made and natural capital are accumulated. If labor and these forms of capital are complementary, the output effects outweigh the substitution effects in the long run, leading to net accumulation of natural as well as man-made capital as a result of such technological or market development. Population growth also induces investment in both man-made and natural resource capital in the long run by increasing their marginal products. However, population growth causes declining per capita levels of both natural and man-made capital and production per capita in the long run, if technology is fixed and decreasing returns to scale. The model thus supports the Boserupian argument of induced intensification and resource improvement, as well as the Malthusian argument of the impoverishing effects of population growth. However, population growth may also induce development of infrastructure, markets, and technological or institutional innovation by reducing the fixed costs per capita of these changes, though these developments may not occur automatically. Government policies can play a large role in affecting whether these potential benefits of population growth are realized. In addition, credit policies may reduce resource degradation caused by substitution of man-made for natural capital, by allowing farmers to accumulate man-made capital (such as fertilizers) without depleting their natural capital. Policies to internalize the external environmental costs of using man-made capital will reduce both types of capital and production, indicating a clear trade-off between addressing environmental concerns on the one hand and reducing poverty and promoting resource conservation investments on the other. By contrast, internalizing the external benefits of investments in resources increases wealth and production per capita in the long run. The ‘intertemporal externality’ due to a higher private than social rate of time preference does not justify interventions to promote investments in resource capital; rather it argues for the promotion of savings and investment in general.     

基于SSM分析法的江苏经济增长的地域差异研究

运用动态偏离—份额分析法对江苏省三大地区和各地级市2000￣2005年间经济增长情况进行分析,计算出各地产业结构和区位两个因素对经济增长的贡献率,并以此为依据分别将13个地级市划分为3类;结果发现产业结构和区位两因素对经济增长的贡献情况呈现明显的由南到北逐渐递减的地域差异特征,在此基础上提出相应的对策及建议。     

Agricultural commercialisation,asset growth and poverty in rural Vietnam

Poverty remains a substantial threat in rural areas of many developing countries, and solving this problem requires an in-depth understanding of the income generating capacity that determines poverty. This paper examines the impact of agricultural commercialisation on the capability of rural households to accumulate and productively use assets and reduce structural and multidimensional poverty. A longitudinal dataset of around 2000 households with a total of 9781 observations from five rural surveys undertaken in the period 2008–2017 in Vietnam is used. Results from a fixed effects regression with an instrumental variable and a control function approach show that agricultural commercialisation has a positive effect on the accumulation of assets and reduces multidimensional and structural poverty over time. However, the effect is not homogeneous and is larger for households that are not mainly engaged in rice commercialisation. This suggests that commercialisation can be a path out of poverty, especially if policy makers move towards utilising other crops instead of rice.     

Modelling New Zealand dairy products: evidence on export survival and duration

This article presents evidence concerning the pattern of New Zealand dairy exports duration and survival from 1989 to 2017. It also analyses the influence of a set of supply, demand and gravity‐type drivers on the hazard rate for New Zealand dairy export relationships. The findings are summarised as follows. First, New Zealand dairy export relationships are dynamic with numerous entries and exits to and from foreign markets. Around half of the relationships survived for only 1–2 years at the sequence level. Second, duration of sequence, left‐censoring, initial export, decomposed sequences, New Zealand export price index, the number of cows available for dairy production, the number of origins and destinations, and destination partner’s GDP are the most significant factors reducing the hazard rate of export relationships. As regards the effects of the non‐tariff measures, it is interesting that technical barriers of trade are found to significantly decrease the hazard rate. Only pre‐shipment inspection and contingent trade protective measures are significant impediments to New Zealand dairy export relationships. Finally, hazard probabilities for New Zealand dairy export relationships are estimated to be ‘L‐shaped’ over time, whether or not non‐tariff measures are applied to New Zealand dairy products.     

土壤pH值对蓝莓幼苗生长发育的影响

介绍了调节土壤pH值对适宜在北方栽种的两个优良蓝莓品种幼苗的生长发育的影响;结果表明,土壤pH值是影响蓝莓栽培最重要的一个土壤因子,不同品种的蓝莓最适宜的土壤pH值不同,＂美登＂在土壤pH=4.0-4.5生长最好,＂北村＂在土壤pH=4.5-5.0生长最好。     

Economic growth,convergence, and agricultural economics

After nearly two centuries of lagging behind the industrial countries, growth in many developing countries has surged since the early 1990s. This outperformance has major implications for almost all areas of agricultural economics and, if continued, will likely do so into the future. This article aims to identify the key ways in which the changes in rich and poor country growth rates matter for agricultural economists, as a basis for formulating better research agendas. A key impact arises through sharp increases in demand for agricultural resources as demand for livestock products increases. This changing structure of food demand has important implications for nutrition studies and policies, with the emergence of a double burden of malnutrition. On the supply side, growth in developing countries tends to increase domestic food supply, which is also boosted by increases in research and development spending. Growth in developing countries both stimulates and benefits from increases in infrastructure investment, evaluation of which requires new analytical tools. Negative impacts include the contribution of increased demand for livestock products to global greenhouse gas emissions. In terms of trade policy, growth in developing country is tending to lead to convergence of agricultural policies with the pattern of assistance seen in today's developed countries, raising concerns about the future need to deal with collective action problems, particularly those that increase the volatility of world prices.     

西北五省水资源消耗对经济增长的影响

从水资源消耗量和消耗结构两个方面考虑水资源对经济增长的影响,首先利用改进的C-D生产函数,结合Romer阻尼分析模型,从三次产业角度测算西北五省水资源对经济增长的阻尼大小;并运用结构偏差系数对西北五省水资源消耗结构和产业结构的动态变化进行测算。从水资源消耗量的测算看,西北五省三次产业的资本和技术的产出弹性均大于劳动和水资源的产出弹性,反映西北地区经济的发展对资本和技术的依赖性更强,且第二产业存在水资源增长阻尼的地区最多,其发展对水资源依赖较大;从水资源消耗结构看,各地区水资源在第二和第三产业之间的配置基本达到最优效率的状态,但在第一和第二产业以及第一和第三产业之间配置不均,水资源消耗结构变动滞后于产业结构变动,地区水资源消耗结构与产业结构不协调现象严重。基于研究结论,提出各地区需提高用水效率,减少用水量;改善用水结构,促进水资源向第二、第三产业流动等政策建议。     

Investment,subsidies, and pro‐poor growth in rural India

This article reviews the trends in government subsidies and investments in and for Indian agriculture; develops a conceptual framework and a model to assess the impact of various subsidies and investments on agricultural growth and poverty reduction; and presents reform options with regard to re‐prioritizing government spending. Subsidies in credit, fertilizer, and irrigation have been crucial for small farmers to adopt new technologies particularly during the initial stage of the green revolution in the late 1960s and 1970s. But it is now investments in agricultural research, education, and rural roads that are the three most effective public spending items in promoting agricultural growth and reducing poverty.