Adopters,testers or pseudo-adopters? Dynamics of the use of improved tree fallows by farmers in western Kenya

Although there has been increasing research on the adoption of agroforestry technologies over the last decade, few such studies have assessed uptake over a long period and many are based on a single snapshot in time. Furthermore, most of these studies have mainly looked at non-adopters and adopters: only recently have social scientists considered testers. A further category of users neglected in adoption studies has been re-adopters of technologies. Studying this group provides an interesting and more nuanced understanding of adoption and re-adoption. Methodologically, most adoption studies use quantitative methods and fail to link their findings to wider socio-economic, political and institutional settings. This paper presents a study of the dynamics of improved tree fallow use by farmers in Siaya and Vihiga districts of western Kenya over a period of eight years. It uses both qualitative and quantitative data to critically discuss the motivations of adopters, testers/rejecters and re-adopters. The results show that the process of adoption is highly dynamic and variable with farmers planting improved fallows and discontinuing or re-adopting them due to a whole range of factors, of which soil fertility improvement is just one. These factors included incentives from projects, the tying of adoption to credit programmes, prestige, participation in seminars/tours and the availability of a seed market from projects promoting improved fallows. Farmers planting improved fallows for such reasons may be termed ‘pseudo-adopters’. There were significant differences in adoption between the two districts, with more farmers in Siaya planting improved fallows than in Vihiga. A majority of farmers in Vihiga (53%) who were given seed never planted improved fallows, even though they had been exposed to the technology. Some 40% of farmers in Siaya and 38% in Vihiga planted improved fallows but later rejected them. This has some important implications for research and development. For improved fallow technologies to be attractive to farmers, they must provide other tangible economic benefits besides soil fertility improvement. This presents a challenge to researchers who must better attune themselves to the needs and demands of farmers if they wish to see their research findings widely adopted.     

自压式树状管网的两级优化设计模型与神经优化设计

建立了自压式树状管网两级优化设计模型，并用人工神经网络法实现树状管网非线性规划模型的快速求解。采用的人工神经网络技术的两级优化设计模型在适用范围、求解速度和获得最优解能力上，均优于单一的非线性规划模型和线性规划模型，是实现树状管网全局优化设计的一条新途径。     

联合收割机液压系统故障树分析

故障树分析法(FTA)是一种将系统故障形成的原因由总体到部分按倒立树形状逐级细化的分析方法,是一种对系统设计、故障分析和排除非常有效的方法。为此,应用故障树分析方法对联合收割机液压系统进行了分析,根据液压系统结构以及组件与系统之间的逻辑关系,绘制了系统的故障树,并通过结构函数表示了各种因素对系统状态的影响。     

大兴安岭火烧迹地主要目的树种的天然更新

对不同火烧方式、火烧强度、林分组成、坡向、坡位、郁闭度、土壤厚度、下木盖度、地被物盖度、林龄等条件下的样地的天然更新情况进行了调查。结果表明:地表火火烧迹地的天然更新效果好于树冠火火烧迹地;中度火烧迹地好于重度火烧迹地;发生火烧的林分比未发生火烧的林分天然更新效果好。     

树木提取液抑制白蚁的效能试验

通过26种树木的不同提取液室内制剂筛选试验,从中筛选出灭蚁活性较强的树木提取液,分别配制9种单剂,在小型试验基础上优选配方,结合植物资源等因素,研制成环保型灭白蚁粉剂。用该粉剂在厦门、福州的公园中进行防治树木白蚁的药效试验,结果表明:处理后10 d的防效为76%~100%,处理后20 d的防效为81%~100%,处理后30 d的防效为100%,并且施药9个月后检查仍能持效。     

植保无人飞机不同施药模式对Y形梨树雾滴沉积分布研究

为了研究油动单旋翼植保无人飞机采用“行间飞”和“Y间飞”2种飞行施药模式对Y形梨园进行喷雾作业后雾滴在Y形梨树冠层中的沉积分布规律,以30 g/L的诱惑红85水溶液为喷雾剂,铜版纸为雾滴收集卡,设计了4种不同作业速度梯度对Y形梨树喷雾效果试验,研究对比了不同飞行速度条件下2种飞行施药模式的雾滴沉积分布情况。试验结果表明：采用“行间飞”飞行施药模式喷雾时,雾滴在Y形梨树主枝外部的沉积密度高于在内部的沉积密度雾滴,且飞行速度为2 m/s和3 m/s时的沉积密度比飞行速度为4 m/s和5 m/s的沉积密度显著偏高。“Y间飞”飞行施药模式下雾滴在Y形梨树冠层不同位置的雾滴沉积分布更均匀。在风速小于1.3 m/s的微风条件下,当使用油动单旋翼植保无人飞机以距离Y形梨树冠层顶部2 m的高度喷雾作业时,应当采用“Y间飞”飞行施药模式,同时飞行速度以2?3 m/s为宜,此时雾滴的沉积密度在冠层内部和外部均大于15个/cm2。研究结果可以为使用植保无人飞机防控梨园病虫害提供喷雾技术依据。     

根域限制栽培对主干形‘圆梦’桃生长和果实品质的影响

根域限制栽培具有控制树冠、促进果树成花的优点,适宜在主干形整枝的密植果园中应用,但不同品种桃表现不同。‘圆梦’桃是由‘湖景蜜露’和‘白丽’杂交而来的中晚熟新品种,为明确‘圆梦’用作南方密植品种的适用性,以浙江省桃主栽品种‘湖景蜜露’为对照品种,对其营养生长、成花量和果实品质进行了研究,结果表明根域限制栽培的‘圆梦’树体营养生长和枝条成花量与‘湖景蜜露’基本一致,且果型大小、糖度、色泽更优。     

南方地区甜樱桃不同品种及树形组合筛选

以甜樱桃主栽品种“布鲁克斯”、“红蜜”、“拉宾斯”、“萨米脱”、“黑珍珠”、“秦林”、“06-7”为试材,研究在南方山地条件下不同栽培模式对生长量、果实品质及产量的影响。结果表明：在高海拔条件下甜樱桃物候期相应推迟7-14天;不同树形树势存在显著差异,UFO树形树势良好,且对于果实品质提高有一定作用;UFO树形可显著提高“布鲁克斯”、“06-7”、“萨米脱”等品种产量。该研究为甜樱桃在浙江等南方地区推广合理树形提供参考依据     

疏花对无核荔枝果实和树体营养的影响

为了研究疏花对无核荔枝果实和树体营养的影响,以不疏花为对照,在初花期对其进行疏花处理,统计疏花量、记录果实发育情况及成熟日期,并测定果实成熟时的品质和整个过程中树体叶片营养变化情况。据统计,每株树的平均疏花量达到80%-90%左右,疏掉的小穗数、支穗数和侧穗数分别为89.81%、89.74%、81.82%。试验结果表明,疏花使无核荔枝的果实发育情况及果实成熟时的可食率、单果重、总糖、维生素C、还原糖均高于对照;果实成熟时,平均单株产量提高70.59%;疏花处理的果实成熟期较对照提前7天左右;该过程中树体叶片N、P、K、S、Ca、Mg含量在前期高于而后期稍低于对照。疏花加快了无核荔枝果实生长发育,并提高了果实的产量和品质。