Field investigation on effects of wheat-straw/corn-stalk mulch on ecological environment of upland crop farmland

This work systematically investigates the effects of wheat-straw/corn-stalk mulch on the ecological environment in upland crops (winter wheat, summer corn) field from 1997 to 1998. With and without mulch soil moisture distribution, water demand, day and night variation of soil temperature, weeds control, crop yields, water and soil conservation, as well as improvement of soil texture were experimentally investigated. The optimal mulch rate for both water saving and yield-increase was determined. Ineffective interplant evaporation can be turned into effective transpiration of leaf by application of wheat-straw/corn-stalk mulch, which enhances the utility factor of soil moisture and reduces irrigation norm, and may also regulate soil temperature, increase soil fertility, and improve soil texture after being returned to the field. Wheat-straw/corn-stalk mulch inhibits evaporation of moisture so that accumulation of salinity near the soil surface is prevented, and thus ameliorates salinization of land. In the region of severe soil erosion, mulch is used to cover land so as to forestall hydraulic and wind erosion of the soil.     

农户管理水平下微咸水灌溉对土壤水盐动态及作物产量的影响

微咸水灌溉对土壤水盐动态及作物产量的影响因管理水平而异,实验站与农户管理水平间的比较研究有助于揭示专家与农户间的知识差,促进合理灌溉措施的推广.该文基于农户田间试验和农户调查,分析了农户管理水平下微咸水灌溉对土壤水盐动态及作物产量的影响;对比实验站研究结果,讨论了实验站和农户管理水平下微咸水灌溉影响的差异.结果表明:农户管理水平下,微咸水灌溉可能主要影响0～80cm土层的土壤饱和电导率;土壤盐分向下淋洗是盐分运动的主要趋势,很难形成上行运动造成土壤次生盐渍化;相对于淡水灌溉,微咸水灌溉的冬小麦相对产量为45.38％～83.33％,夏玉米相对产量为42.86％～58.57％;无论是实验站还是农户管理水平,微咸水灌溉均对土壤饱和电导率产生显著影响,实验站管理水平下的灌溉制度比农户管理水平下的更加合理,农户管理水平下微咸水灌溉对作物产量的影响比实验站管理水平要严重;需要多角度采取措施提高农户管理水平.     

近代华北乡村社会研究视野下的青苗会组织

青苗会是近代华北普遍存在的一种乡村自治组织,它的发展历程与中国近代社会历史的演变息息相关。青苗会的研究,有助于把握近代华北乡村社会变迁的脉络。本文联系当前研究状况,围绕有关乡村社会的权力运作,从国家与地方社会互动的角度出发,对青苗会组织及其相关问题予以初步探讨。     

气候变化对中国主要农作物秸秆资源的影响

生物质能在缓解能源紧张,降低气候变化影响方面具有广阔的发展前景。农作物秸秆作为其丰富重要的原料之一,它的有效开发和利用,将对我国生物质资源的综合利用有重要影响。气候变化会影响农作物秸秆产量,本研究利用CERES作物模型模拟了基本气候BS情景下(1961年-1990年)和SRES温室气体排放方案下B2情景的(2011年-2100年)我国三大粮食作物水稻、小麦、玉米的秸秆生产量,分析并预测了未来气候变化对其秸秆生产量的影响,结果表明:①作物秸秆生产总量表现为先降低(2020s)后增加(2050s、2080s)的趋势,其中水稻的秸秆单产和总量将下降,而小麦和玉米的秸秆单产、总量则有增加趋势,尤其是小麦增加幅度更大;②未来气候变化将增大作物秸秆生产总量的年际波动,影响秸秆利用量的稳定性;③华北地区是未来三大作物秸秆总量增加的主要区域,有利于秸秆资源的开发和利用,而东北的东部地区秸秆总量表现为大幅度的降低。本文成果属初步研究,存在一定的不确定性,今后需要继续深入探讨,逐步降低研究中的不确定性。     

东北地区农田净初级生产力时空特征及其影响因素分析

本文在GIS技术的支持下,利用2000年-2006年MODISNPP(净初级生产力)数据、气象数据和土地利用数据,在经过统计数据验证之后,将东北地区农田生产力划分为五级:高产、较高产、中产、较低产和低产。在此基础上,分析了东北地区农田生产力的空间分布特征与时间变化规律,并分析了气候因子和地形因子对农田生产力的影响。结果表明:东北地区农田以旱田为主,占总面积的89.8%,农田净初级生产力自西向东、自北向南逐渐增加;旱田年均NPP变化范围在(309.8~329.5)gC(/m2·a),水田年均NPP介于(323.5~341.7)gC(/m2·a)之间,二者的年际变化趋势一致;2000年-2006年,东北地区农田NPP均值由309.1gC(/m2·a)上升至331.4gC(/m2·a);旱田(水田)NPP与气象因子以及地形因子的相关分析结果表明:生长季降水与旱田(水田)NPP呈现显著正相关,相关系数分别为0.53和0.37;生长季气温与旱田(水田)NPP呈微弱负相关关系;由于东北地区农田多分布在平原区,地形因子(高程、坡度、坡向)对旱田(水田)NPP的影响不大。以上结果表明,降水是影响东北地区农田净初级生产力的最重要因素。     

Disseminating Improved Practices: Are Volunteer Farmer Trainers Effective?

Abstract

Purpose: This paper assesses the effectiveness of volunteer farmer trainers in promoting adoption of agricultural technologies in western Kenya. Specifically, the purpose was to assess the type of information they disseminated, farmer trainers' characteristics desirable to farmer trainees, and how trainees evaluate farmer trainers.

Design/methodology/approach: Data were collected through focused group and open discussions, and interviews with 44 farmer trainers (32% women) and 91 trainees (63% women). Effectiveness of training was assessed based on level of learner satisfaction and attributes pertaining to knowledge, skill, attitude and application of the learning on farms. Other topics examined included selection of farmer trainers, organization of training, type, how and to whom information is disseminated, and farmer trainers' constraints and opportunities.

Findings: Farmer trainers played important roles such as mobilizing and training fellow farmers, hosting demonstration plots, bulking and distributing planting materials. They were, however, rated slightly lower in follow-ups and seed bulking. Farmer trainers disseminate on average two to four different types of technology. Crop-based technologies were disseminated more than livestock-based ones because of their simplicity. Technical backstopping from extension workers remains a challenge, which may compromise quality of information disseminated. The survey showed that the approach is sustainable, with farmer trainers continuing their work several years after project support had ended.

Practical implications: The results from this study are of use to development programmes keen on using low-cost, community-based dissemination approaches. Recommendations are also given on selecting farmer trainers, organizing training, types of technologies to disseminate incentives, and sustainability.

Originality/value: The added value lies in filling information gaps in the use and effectiveness of the farmer trainer approach in promoting technology dissemination.     

北方农牧交错带作物耗水特征及其与气温和降水的关系——以内蒙古呼和浩特市武川县为例

当前干暖化的气候变化趋势对北方农牧交错带农作物生长发育产生了重要影响,研究农作物耗水特征及其与气温、降水的关系对指导当地农业生产与生态建设具有重要意义。本文以北方农牧交错带内蒙古呼和浩特市武川县为例,基于1960年-2007年的气温、降水等气象资料和1983年-2007年的土壤水分数据,分析气温、降水变化特征,划分降水年型,研究小麦、莜麦和马铃薯三种当地典型作物的生育期耗水特征,探讨气温、降水对作物耗水的影响。研究表明：近50年来,武川气候呈现干暖化趋势,生长季平均温度每年升高0.03℃,生长季降水每年减少0.9mm;近25年来,干暖化趋势更加明显,生长季平均温度每年升高0.08℃,生长季降水每年减少2.5mm;作物耗水量随之呈现减少趋势,小麦耗水量平均每年减少1.65mm,莜麦每年减少2.04mm,马铃薯每年减少3.85mm。作物耗水量在不同年型表现出差异性。马铃薯、莜麦耗水量明显多于小麦。降水变化对作物耗水量影响显著,当前气温升高、降水减少的趋势不利于北方农牧交错带作物生产,培育抗旱品种、发展抗旱栽培管理措施是适应气候变化的重要途径。     

中国南方作物秸秆资源及其开发利用

我国南方作物秸秆资源丰富，具有种类多、数量大、质量高、分布广的特点；目前，南方作物秸秆资源主要用作燃料、饲料、肥料和工业原料等多种用途，但其利用上明显存在“三低一重”的特点（即利用率低、转化率低、经济效益低和环境污染严重）。今后，开发利用南方作物秸秆资源，必须做到：①充分提高认识，切实转变观念；②扩大秸秆生产，增加秸秆来源；③充分利用秸秆，避免一切浪费；④合理利用秸秆，提高转化效率；⑤综合开发利用，提高三大效益     

优化作物布局，合理开发利用水资源

本文以一个典型提黄灌区为例，从水资源利用角度出发，建立了作物布局的线性规划模型，并用计算机求解，得到了两个规划水平条件下的解，从而说明了优化作物布局在开发利用水资源过程中的必要性和重要性．     

黄淮海平原种植业生产波动分析

本文利用黄淮平原253个县1983－1989年农业生产的时间序列数据，采用多元回归和逐步回归方法分析了种植业产值波动与主要作物总产波动、各作物的总产波动与单产、播种面积波动在时间和空间上变化的相关关系；并进一步分析了原因和提出了稳定种植业生产的建议。