藏鸡的现状及利用

藏鸡是一种体型较小、胸腿发达、快羽 ,适宜于高寒、低压、缺氧高海拔地区的地方优良品种 ,素以觅食能力强 ,极耐粗放 ,体小肉多、肉质细嫩鲜美而著称 ,是高海拔地区养禽业中的当家品种。针对藏鸡生产、繁育的现状和不足 ,分析其制约因素 ,研究搞好藏鸡繁育与饲养的综合配套技术以及藏鸡可持续开发利用的战略对策 ,无疑具有现实的指导意义和长远的理论意义     

华北典型区冬小麦区域耗水模拟与灌溉制度优化

以经校验Aquacrop模型模拟了不同土壤条件下冬小麦水分与产量响应关系,结合北京大兴区土壤分布及其冬小麦实际种植情况,对模型模拟结果进行区域尺度拓展,以此为基础分析了研究区不同灌溉制度下冬小麦耗水量、产量及水分生产率的变化规律,并推荐了与华北地区水资源实际情况相适宜的冬小麦亏缺灌溉制度。结果表明:应用Aquacrop模型能较好模拟冬小麦生育期内土壤墒情和冠层覆盖度的动态变化过程及其生物量与产量情况,可利用经校验后的模型进行冬小麦水分与产量响应关系研究。灌溉定额在300 mm范围内,随着灌溉量增加,耗水量增大;在灌水次数相同条件下,灌溉日期不同,因蒸腾量变化导致耗水量差异显著。在相同处理下总体上降水多年份产量较高,而不同处理之间随着灌溉量增加产量增大;在灌水次数相同情况下,灌溉关键生育时段选择对冬小麦产量形成及水分生产率提高至关重要。以冬小麦增产提效为原则,在灌1水情况下重点保障拔节-抽穗阶段的需水;灌2水情况下重点保障返青-拔节、抽穗-乳熟阶段需水;灌3水情况下重点保障返青-拔节、拔节-抽穗、抽穗-乳熟阶段需水。针对华北水资源严重短缺实际,建议北京大兴区冬小麦采用灌2水的亏缺灌溉制度,较灌4水情况下的灌溉量与耗水量分别减少140、65 mm,能确保75%产量。可见,在与华北类似的资源性缺水区域,选择适宜亏缺灌溉制度,能大幅降低区域灌溉量与耗水量,在稳定区域冬小麦产量及涵养地下水源方面具有重要的现实意义。     

Vegetation,Wildlife, and Livestock Responses to Planned Grazing Management in an African Pastoral Landscape

Rangelands are vital for wildlife conservation and socio‐economic well‐being, but many face widespread degradation because in part of poor grazing management practices. Planned grazing management, typically involving time‐controlled rotational livestock grazing, is widely touted as a tool for promoting sustainable rangelands. However, real‐world assessments of its efficacy have been lacking in communal pastoral landscapes globally, and especially in Africa. We performed landscape‐scale assessment of the effects of planned grazing on selected vegetation, wildlife, and cattle attributes across wide‐ranging communally managed pastoral rangelands in northern Kenya. We found that planned grazing enhanced vegetation condition through a 17% increase in normalized difference vegetation index, 45–234% increases in herbaceous vegetation foliar cover, species richness and diversity, and a 70% reduction in plant basal gap. In addition, planned grazing increased the presence (44%) and species richness (53%) of wild ungulates and improved cattle weight gain (>71%) during dry periods when cattle were in relatively poor condition. These changes occurred relatively rapidly (within 5 years) and despite grazing incursion incidents and higher livestock stocking rates in planned grazing areas. These results demonstrate, for the first time in Africa, the positive effects of planned grazing implementation in communal pastoral rangelands. These improvements can have broad implications for biodiversity conservation and pastoral livelihoods. Copyright © 2017 John Wiley & Sons, Ltd.     

Optimizing supplemental irrigation: Tradeoffs between profitability and sustainability

Water production functions are used to model yield response to various levels of supplemental irrigation (SI), to assess water productivity coefficients, and to identify optimum irrigation under various input-output price scenarios. The SI production function is taken as the difference between the total water production function (irrigation + rain) and that of rainwater. Theoretical analysis of the unconstrained objective function shows that the seasonal depth of SI to maximize profit occurs when the marginal product of water equals the ratio of unit water cost to unit product sale price. Applying this analysis to wheat in northern Syria, the production functions of SI under different rainfall conditions are developed. Coupled with current and projected water costs and wheat sale prices, the functions are used to develop an easy-to-use chart for determining seasonal irrigation rates to maximize profit under a range of seasonal rainfall amounts.Results show that, for a given seasonal rainfall, there is a critical value for the ratio of irrigation cost to production price beyond which SI becomes less profitable than rainfed production. Higher product prices and lower irrigation costs encourage the use of more water. Policies supporting high wheat prices and low irrigation costs encourage maximizing yields but with low water productivity. The resulting farmer practice threatens the sustainability of water resources. Balancing profitability versus sustainability is a challenge for policy makers. Our analysis can help national and local water authorities and policy makers determine appropriate policies for water valuation and allocation; and assist extension services and farmers in planning irrigation infrastructure and farm water management.     

不同紫花苜蓿品种引种试验研究

引进了国外8个苜蓿品种,在2003年至2005年对其产量、株高、营养价值、越冬率、越夏性、抗倒伏和经济效益等方面进行了比较,结果表明这8个苜蓿品种在郑州地区均表现了良好的适应性,其中WL232和猎人河是推广的首选品种。     

Integrated effect of transplanting date, cultivar and irrigation on yield, water saving and water productivity of rice (Oryza sativa L.) in Indian Punjab: Field and simulation study

Individual effect of different field scale management interventions for water saving in rice viz. changing date of transplanting, cultivar and irrigation schedule on yield, water saving and water productivity is well documented in the literature. However, little is known about their integrated effect. To study that, field experimentation and modeling approach was used. Field experiments were conducted for 2 years (2006 and 2007) at Punjab Agricultural University Farm, Ludhiana on a deep alluvial loamy sand Typic Ustipsamment soils developed under hyper-thermic regime. Treatments included three dates of transplanting (25 May, 10 June and 25 June), two cultivars (PR 118 inbred and RH 257 hybrid) and two irrigation schedules (2-days drainage period and at soil water suction of 16 kPa). The model used was CropSyst, which has already been calibrated for growth (periodic biomass and LAI) of rice and soil water content in two independent experiments. The main findings of the field and simulation studies conducted are compared to any individual, integrated management of transplanting date, cultivar and irrigation, sustained yield (6.3-7.5 t ha⁻¹) and saved substantial amount of water in rice. For example, with two management interventions, i.e. shifting of transplanting date to lower evaporative demand (from 5 May to 25 June) concomitant with growing of short duration hybrid variety (90 days from transplanting to harvest), the total real water saving (wet saving) through reduction in evapotranspiration (ET) was 140 mm, which was almost double than managing the single, i.e. 66 mm by shifting transplanting or 71 mm by growing short duration hybrid variety. Shifting the transplanting date saved water through reduction in soil water evaporation component while growing of short duration variety through reduction in both evaporation and transpiration components of water balance. Managing irrigation water schedule based on soil water suction of 16 kPa at 15-20 cm soil depth, compared to 2-day drainage, did not save water in real (wet saving), however, it resulted into apparent water saving (dry saving). The real crop water productivity (marketable yield/ET) was more by 17% in 25th June transplanted rice than 25th May, 23% in short duration variety than long and 2% in irrigation treatment of 16 kPa soil water suction than 2-days drainage. The corresponding values for the apparent crop water productivity (marketable yield/irrigation water applied) were 16, 20 and 50%, respectively. Pooled experimental data of 2 years showed that with managing irrigation scheduling based on soil water suction of 16 kPa at 15-20 cm soil depth, though 700 mm irrigation water was saved but the associated yield was reduced by 277 kg ha⁻¹.     

土壤水流动系统及其应用初探

土壤水流动系统是由水势场，介质场，水化学学场，温度场耦合而成，并在时空四维上不断演变化的动态系统，土壤水调控就是通过综合措施改善水流动系统的上下边界年及浅部介质特性，优化田间微水文系统、微气候系统及土壤水流动系统。     

抑制素免疫对牛、羊繁殖力作用的研究进展

文章综述了天然提纯,化学合成及重组等不同种类抑制素抗原免疫对牛、羊繁殖力的影响.近年来抑制素疫苗作为多胎疫苗的角色已越来越为人们所重视,其免疫原性同抗原本身一些因素如纯度、免疫原性、异原性、免疫剂量有关.     

透光抚育对红松阔叶林群落结构与生产力的影响

采用样带网格调查方法和群落重要值分析方法，研究透光抚育（全透光、半透光、未透光）对红松阔叶混交林群落（人天混群落）的树种组成结构、径级分布、蓄积量和红松蓄积生产力的影响效果。结果表明：沿由小到大的透光强度，人天混群落中红松重要值依次增大（0．499～1．000），透光有利于人天混群落中红松优势地位增强；红松大径木比例依次增加（0．00％～54．0％），小径木比例依次减少（74．9％～2．7％），透光有利于人天混群落中红松大径木比例提高；群落蓄积量依次增加（60．2475～230．4051m^3／hm^2），红松蓄积生产力依次增加（1．2692～5．3603m^3／hm^2·a），透光有利于人天混群落蓄积量及红松蓄积生产力的提高。     

农业机械化对农业产出的贡献率

测算出农业机械化对农业生产的贡献份额,有助于从总体上把握农业机械化的发展水平、发展潜力和发展趋势,为制定农业机械化政策提供可靠有力的理论依据.为此,分析了"有无比较"法及"生产函数"法应用于测算农业机械化贡献率的情况,并以湖南省为实例,采用"有无比较"法计算了农业机械化对农业产出的贡献率.