小陇山锐齿栎天然林的树种多样性和结构特征

运用林分结构参数混交度、角尺度、大小比数、直径分布、林层数和物种多样性指标,对小陇山百花林场王安沟经营区锐齿栎天然林样地的群落结构特征进行了研究.结果表明:锐齿栎天然林群落的树种组成十分丰富,树种多样性较高,群落中具有构成当地森林群落的主要树种,结构特征为复层异龄林;在水平结构方面群落中,林木个体分布的角尺度均值为0.489,林分内林木整体分布格局属随机分布;群落的树种隔离程度较高,平均混交度为0.598,处于强度和极强度混交的林木比例高达78.6%;群落中树种以胸径作为比较指标的林木个体的优势排列顺序为:白桦>湖北花楸>漆树>锐齿栎>三桠乌药>华山松>少脉椴>鹅耳枥>青榨槭>膀胱果;在垂直结构方面,群落的平均林层数为2.3层,垂直结构复杂,分化明显.     

Fallow residue management effects on upland rice in three agroecological zones of West Africa

Improving fallow quality in upland rice-fallow rotations in West Africa through the site-specific use of leguminous cover crops has been shown to sustain the productivity of such systems. We studied the effects of a range of residue management practices (removal, burning, mulching and incorporation) on fallow biomass and N accumulation, on weed biomass and yield response of upland rice and on changes in soil physical and chemical characteristics in 2-year field trials conducted in three agroecological zones of Côte d'Ivoire. Across fallow management treatments and agroecological zones, rice yields were on average 20–30% higher in legume than in natural fallow plots. Weed biomass was highest in the savanna zone and lowest in the bimodal forest and tended to be less following a legume fallow. Regardless of the type of fallow vegetation and agroecological zone, biomass removal resulted in the lowest rice yields that varied from 0.5?t ha^–1 in the derived savanna zone to 1.5?t ha^–1 in the Guinea savanna zone. Burning of the fallow vegetation significantly increased yield over residue removal in the derived savanna (0.27?t ha^–1, P<0.05) and bimodal forest zones (0.27?t ha^–1, P<0.01), but not in the Guinea savanna. In both savanna environments, residue incorporation was superior to the farmers' practice of residue removal and rice yield increases were related to amounts of fallow N returned to the soil (r²=0.803, P<0.01). In the forest zone, the farmers' practice of residue burning produced the highest yield (1.43?t ha-1 in the case of legumes) and resulted in the lowest weed biomass (0.02?t ha^–1). Regardless of the site, improving the quality of the fallow or of its management had no significant effects on either soil physical or soil chemical characteristics after two fallow cycles. We conclude that incorporation of legume residues is a desirable practice for rice-based fallow rotation systems in savanna environments. No promising residue management alternatives to slash-and-burn were apparent for the forest zone. Determining the possible effects on soil productivity will require longer-term experiments.     

仔猪粉状高铜饲料中添加不同剂量甜味剂对生长性能的影响

试验共分4个处理,其甜味剂的添加量分别为0、200、300、400g/t,试验选用20头体重为14kg左右的三元(DХLХY)杂交猪,试验期为20d,试验期间考察猪的平均日增重、日均采食量、料肉比3个生长性能指标。结果表明:甜味剂的添加量为常规添加量200g/t时,可显著的提高仔猪粉状高铜饲料的适口性,在200g/t的基础上提高甜味剂的添加量,饲料适口性和日增重均没有得到进一步显著的提高,各处理组料肉比差异均不显著,表明甜味剂的添加对饲料的利用率无显著的影响,因此,在仔猪粉状高铜配合饲料中甜味剂的添加量以常规用量为宜,过高的添加甜味剂并不能起到进一步提高仔猪生长性能的作用。     

Rice yield gaps in irrigated systems along an agro‐ecological gradient in West Africa

Irrigated rice (Oryza sativa L.) in West Africa covers about 12 % of the regional rice‐growing area, and is produced all along the agro‐ecological gradient from the forest zone to the Sahara desert margins. Spatial and temporal variability of yield gaps (i.e., difference between actual and potential yield) were determined to set priorities for research and target technologies. On‐farm trials were conducted on 191 irrigated lowland fields in the humid forest, the savanna and the Sahel. Farmers' yields were compared with those of super‐imposed treatments of improved fertilization and weed management. Farmers' yields varied between 0.2 and 8.7 Mg ha^‐1, with average yields of 3.4 Mg ha^‐1 (Guinea savanna), 3.6 Mg ha^‐1 (humid forest), 3.9 Mg ha^‐1 (Sahel), and 5.1 Mg ha^‐1 (Sudan savanna). Simulated potential yields increased from 7 Mg ha^‐1 in the forest to about 10 Mg ha^‐1 in the Sahel. Accordingly, yield gaps were large, ranging from 3.2 to 5.9 Mg ha^‐1. Researcher weed control in the Sahel gave grain yield increases of about 1.0 Mg ha^‐1. Improved weed and N fertilization management increased yields by 1 to 2 Mg ha^‐1 in the forest and Guinea savanna sites. A share of 57‐80 % of the yield gap could not be accounted for. Improving weed control is likely to have the highest pay‐off in the Sahel while improved management of fertilizer N will be most beneficial in the forest and savanna environments.     

棉花高产优质低耗栽培实用模型的研究 Ⅲ.栽培因子对皮棉产量和纤维品质的影响

氮、磷、钾对棉花皮棉产量和纤维品质的影响进行了三年的研究(1984～1986),建立了皮棉产量和纤维品质的二次回归模型,并由此筛选出了棉花高产、优质、低耗栽培的综合农艺措施模型。研究结果表明,氮、磷、钾施用量对皮棉产置有显著的影响,全回归方程达到极显著水平(p相似文献   

Land-use by immigrant Baoulé farmers in the Taï region,South-west Côte d'Ivoire (Ivory Coast)

This paper discusses the cropping system of immigrant Baoulé farmers in the rain-forest area of South-west Côte d'Ivoire (Ivory Coast). The area harbours one of the last substantial rain-forest reserves of humid West Africa. Part of it is known as Taï National Park, and has been adopted as one of UNESCO's Man and Biosphere Programme areas.The park area is threatened by farmers in search of land.Soils in the area typically show a low intrinsic nutrient content (particularly phosphorus and potassium), low pH values, a low CEC, and, locally, high levels of gravel.In the Baoulé cropping system fields are kept under perennial crops, mainly cacao, after having been used for food crop cultivation during the first two years. Yam, the most important food crop is grown on mounds. Next to the inherent poverty of the soil, this cropping technique, which disrupts the structure of the top soil is seen as one of the causes for low yields of cocoa on Baoulé farms in the area. Yields per ha amount to c. 60% of that of the national average.The conclusion is that the Baoulé agricultural production system is ill-adapted to the local ecosystem.Measures to improve adaptation include: Introduction of crop species adapted to adverse soil conditions (e.g. rubber, oilpalm), to buffer cacao plantations through planting of shade trees, to apply fertilisers, and to make use of biological nitrogen-fixation.Generally, the remedies proposed involve investments in terms of cash and labour on the part of the farmers. It is argued that farmers will not change their current cropping practices as long as there is forested land in the vicinity. The presence of the Taï forest, c. 300.000 ha of virgin rain-forest, impedes the process of change towards more intensive land-use practices.

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Résumé Aménagement du terroir par les paysans immigrés Baoulé dans la région Taï, Sud-Ouest Ivoirien Ce document traite le système agricole des paysans immigrés Baoulés dans les régions des forêts tropicales humides du Sud-Ouest Ivoirien. Cette région héberge une des dernières réserves substantielles de la forêt tropicale de l'Afrique de l'Ouest. Le Parc National de Taï est la partie de la forêt que l'UNESCO a adoptée dans le cadre du Programme Homme et Biosphère.A l'heure actuelle les intrusions des paysans à la recherche de terre menacent le parc.Une des caractéristiques de cette région est que les sols montrent un niveau bas de nutrients intrinsiques (notamment le phosphore et la potasse), des valeurs basses de pH, une faible capacité d'absorption cationique et, localement, des niveaux élevés de gravier. Les paysans Baoulé plantent des cultures pérennes, surtout le cacaoyer, après avoir produit des cultures vivrières pendant les deux premières années. L'alinment principal, l'igname, est cultivé dans les buttes. A part la pauvresse inhérente au sol, cette technique culturale, qui dérange la structure de la couche arable du sol, est considérée comme une des causes des bas rendements du cacaoyer aux exploitations agricoles Baoulé dans la région. Les rendements par hectare n'atteignent que 60% de la moyenne nationale.On peut conclure que le système de culture Baoulé est mal adapté à l'écologie locale. Les mesures à prendre pour améliorer l'adaptation comprennent: L'introduction des cultures mieux adaptées aux conditions de sol défavorables (par exemple le hévéa, le palmier à huile), protéger les plantations de cacaoyer en mettant des arbres ombreux, l'application des engrais, et l'emploi de la fixation biologique de l'azote par certains arbres légumineux. En général, les solutions proposées entraînent des investissements en termes financiers et de travail de la part des paysans. Il est souligné que les paysans ne changeront pas leur système du culture actuel tant que les forêts sont à proximité. Donc, la présence de la forêt Taï, environ 300.000 hectares de forêt tropicale primaire, empêche le processus de changement en pratiques d'aménagement du terroir.

     

花生新品种比较试验

以汕油523为对照品种,对引进的13个花生新品种进行品比试验,结果表明：泉花551、龙花9号、汕油诱1号、航花2号、航花3号、福花4号等6个品种产量高、生长势强、抗性强、综合性状好,适合南安市进一步试种示范。     

农业专家系统生成工具中知识和模型相结合的研究

专家系统领域中，知识规则是由前提和结论组成的。专家系统在进行推理时，首先要获取前提，有些前提可以直接通过人机交互得到(称直接前提)，而有些前提需根据模型间接得到(称间接前提)。运用面向对象方法学的原则，将直接前提用属性表示，间接前提用方法表示，也将为得出结论所运用的模型用方法表示，再将相关的属性和方法封装在一起，构成一个类，则整个知识规则可抽象成由具有面向对象特点的类组成的知识表示形式，它将描述问题空间的属性和方法有机地结合在一起；同时，在构造推理机时，仍然按面向对象的原则匹配对象，构成了问题空间和求解空间的一致性。这样的软件具有稳定性好、易维护、易扩充的特点。     

X射线衍射半高宽在研究回火残余应力中的作用

在利用X射线衍射研究淬火65Mn钢回火残余应力时发现:半高宽的变化与回火时间、温度密切相关。与硬度变化规律相似,半高宽也是随着回火时间的延长和回火温度的升高呈现单调下降的趋势。因此,X射线衍射中半高宽—回火时间、温度曲线可以用于回火过程中残余应力消除情况的判定。     

The nitrogen nutrition of yam (Dioscorea spp)

Abstract

Information on the nitrogen (N) nutrition of yam (Dioscorea spp) is limited. Our objective was to elucidate the factors controlling N uptake by D. rotundata and D. alata. We analyzed results obtained with improved cultivars of these species grown in three field experiments among which ¹⁵N-fertilizer was used in one. Plant biomass production, leaf area index (LAI), root length density, N and ¹⁵N uptake by the plant were measured in these experiments. Nitrogen uptake was controlled in both species by plant demand and N inputs. A positive relation was observed between N uptake and LAI. Despite the small root system, the ability of the plant to take N up was high. The amount of N derived from the fertilizer recovered in the plant was explained by total N uptake. Finally, avenues to improve the low nitrogen fertilizer recovery (<20%) in yam are discussed.