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A number of improved varieties have been developed by the International Institute of Tropical Agriculture (IITA), combining diverse plant type with resistance or tolerance to several diseases, insect pests, and parasitic weeds and possessing other good agronomic traits. Trials were established with farmers to evaluate several new IITA-bred cowpea varieties on-farm in a process of participatory varietal selection. Central to this has been a ‘mother-daughter’ approach with researcher-managed ‘mother’ trials and farmer-managed ‘daughter’ trials in order to combine researchers' and farmers' criteria in evaluation of new varieties. In both set of trials, new varieties IT89KD-391, IT97K-499-35, and IT89KD-288 were favoured by farmers because of their high grain and fodder yields. Farmers have also shown interest in the continuous use of a local variety Kanannado Brown. It is suitable for relay intercropping; having a creeping habit, and the ability to smother weeds. The brown seeds fetch higher market prices. The implications are that improved cowpea varieties should be suitable for relay-intercropping and controlling weeds, be brown in colour, have large grain size, be pest resistant as well as give high yields of grain and fodder. At the same time, it is important that the farmer's criteria should be considered in breeding and varietal selection programmes.  相似文献   
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Successful agroforestry systems depend on minimizing tree-cropcompetition. In this study, field experiments and a simulation model were usedto distinguish between tree-crop competition for light and belowgroundcompetition in an alley cropping system. Maize (Zea maysL.) was harvested periodically in three treatments: between vertical barriers ofshade cloth, hedgerows of Flemingia macrophylla (Willd.)Merr., and sole maize. Radiation intercepted by the maize was calculated using asimulation model based on measured values for direct and diffuse light, hedgerowdimensions and leaf area, and solar trajectory. Radiation use efficiency wascalculated as biomass production per unit of intercepted radiation. Maizebiomass and yield in both the alley crop and the shade cloth treatment weregreatest in the center of the alleys. Grain yield between hedgerows was 3.5Mg ha−1 (averaged across the alley), significantlyless than in the shade cloth (7.4 Mg ha−1) or thesole maize (7.7 Mg ha−1) treatments. Lightintercepted by the maize in the alley crop was about half that intercepted bythe maize in the sole crop. The shade cloth intercepted less light than thehedgerows because it did not have an appreciable width. Radiation use efficiencyin the three treatments was 0.75 g mol−1 PAR anddid not differ significantly among treatments. Tree-crop competition wasoverwhelmingly for light. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   
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Nitrogen fertilization is a substantial source of nitrogen-containing trace gases that have both regional and global consequences. In the intensive wheat systems of Mexico, typical fertilization practices lead to extremely high fluxes of nitrous oxide (N2O) and nitric oxide (NO). In experiments, lower rates of nitrogen fertilizer, applied later in the crop cycle, reduced the loss of nitrogen without affecting yield and grain quality. Economic analyses projected this alternative practice to save 12 to 17 percent of after-tax profits. A knowledge-intensive approach to fertilizer management can substitute for higher levels of inputs, saving farmers money and reducing environmental costs.  相似文献   
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An outbreak of intestinal coccidiosis in the dog due to Isospora canis characterized by mild severe haemorrhagic diarrhoea of sudden onset, acute abdominal pain, anorexia, dehydration and relative polycythaemia is described. Although clinical recovery followed sulphonamide therapy, reinfection was common within 10 days of treatment.  相似文献   
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The results of a tobacco smoking survey conducted among veterinarians in Queensland, Australia, during 2007 are presented. Of the 567 participants only 3% reported being current smokers, 24% were ex-smokers and 73% had never smoked. The prevalence of smoking was similar among males and females, and the highest smoking rate was reported among veterinarians aged 31–40 years. However, the rate of never-smokers was strongly and negatively correlated with age, and the proportion of ex-smokers increased with age. Encouragingly, the results from this study suggest that tobacco use has all but disappeared from the Australian veterinary profession in recent years.  相似文献   
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为探寻新疆南疆地区籽棉9000 kg·hm-2超高产机理以及相关的指标,对南疆地区生态条件下超高产田、高产田、中高产田进行了调查研究与数据采集。研究发现:要获得超高产,首先要有良好的基础地力,有机质含量超10 g·kg-1,种植密度18×104~21×104株·hm-2为宜;其次,塑造良好株型,株高65~75 cm,茎粗接近10 mm,果枝9~10台,棉铃空间分布均匀,纵向上、中、下果枝棉铃比例3.2∶4.7∶2.1,横向第一、二果节比例7∶3,初花至盛铃LAI、SPAD、Pn一直维持较高水平,盛铃前后达到最大,后期下降缓慢;最后,氮磷钾分配上,前期差异不大,进入花铃期生殖生长明显增强,蕾花铃氮磷钾比例明显增大,一直维持到见絮,超高产处理的蕾花铃干物质量比例明显高于其它处理8%以上,见絮时蕾花铃干物质量达到了6 402 kg·hm-2。以指标数据作参考,塑造良好株型,协调棉铃空间分布,维持较高较长的光合速率,减缓LAI、SPAD下降速度,促进生殖生长,合理养分分配,便能实现产量目标。  相似文献   
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