Contribution of Erythrina protein banks and rejected bananas for improving cattle production in the humid tropics

In view of the low pasture productivity in the Central American humid tropics where cattle rearing is a major land-use activity, it is important to examine the potential of alternate feed sources for ruminant feeding. Erythrina berteroana Uban, locally known as poro, and green banana (Musa AAA) fruits have been identified as two such potential sources. The effects of feeding poro as a grazing supplement and diet supplementation with green banana fruits on cattle productivity were evaluated in a long-term trial in Costa Rica. Daily liveweight (LW) gains were measured and samples of all feed material were analyzed for crude protein and in vitro dry matter (DM) digestibility. Pasture availability was high, averaging 0.17 t DM ha day^–1 over the grazing period. The main grass species were Paspalum fasciculatium Poiret, Axonopus compressus Swartz and to a lesser extent African star grass (Cynodon nlemfluensis Vanderyst). DM yields of poro declined significantly with time (> 50%) when it was managed with a two-month resting period but remained higher when subsequently managed with a three-month resting period. Average daily LW gain of animals was 21% to 26% higher with two hours daily browsing of poro than for animals only grazing pasture. Highest liveweight gain was achieved when diets were supplemented with banana and there was no additional benefit when poro was fed in addition to banana. This suggests that fodder banks of poro or supplements with green banana can improve cattle nutrition in the humid tropics.This revised version was published online in November 2005 with corrections to the Cover Date.     

Agricultural intensity and its measurement in frontier regions

Agricultural intensification is a process of raising land productivity over time through increases in inputs of one form or another on a per unit area basis. Its study is important for several reasons, many of which relate to agroforestry objectives. However, the concept of intensification often is poorly defined in the literature and existing methods and approaches to measuring agricultural intensity are problematic, making it difficult to precisely compare particular farming systems. This paper examines the concept of agricultural intensity, its relevance to efficient and sustainable land use, and the ways it can be measured. A review of existing approaches and methods for measuring intensity, such as those based on output, cropping frequency, and agrotechnologies, revealed that these feature a number of problems. Some of these problems relate simply to imprecision and inaccuracy. But others are due to the unsuitability of these approaches in the context of farming environments, such as frontiers, which are characterized by limited production data; unconventional cropping cycles; myriad production strategies, cropping patterns, and crop-fallow cycles on a single farm; and a high level of system dynamism and production variability over time. A modified approach to measuring agricultural intensity, based on fieldwork in Petén, Guatemala, is presented. This approach, which is better suited to frontier regions, employs an agricultural intensity index to help evaluate the intensity of particular farm units based on the technologies and practices used by the farmer, and the degree to which they are used.This revised version was published online in November 2005 with corrections to the Cover Date.     

青钱柳红豆杉混交造林技术试验

进行了青钱柳红豆杉混交林、纯林造林技术试验。经过3年经营管理,对林木生长量进行了调查,幼林林木生长良好。结果显示:青钱柳红豆杉混交林幼林林木生长量,比青钱柳、红豆杉纯林幼林林木树高大于2.89%、29.66%,平均胸径粗于17.07%、23.08%,平均树冠宽于6.02%、19.72%。     

传染性脾肾坏死病毒、鳜鱼蛙病毒和鳜弹状病毒三重PCR检测方法的建立

【目的】建立可同时检测传染性脾肾坏死病毒（infectious spleen and kidney necrosis virus,ISKNV）、鳜鱼蛙病毒（Siniperca chuatsi ranairidovirus,SCRIV）和鳜弹状病毒（Siniperca chuatsi rhabdovirus,SCRV）的三重PCR检测方法,为鳜鱼等养殖品种流行病学调查提供方法支撑。【方法】根据ISKNV MCP基因、SCRIV MCP基因和SCRV N基因设计3对特异性引物,对PCR扩增反应中的退火温度和引物用量进行优化,建立可同时检测 ISKNV、SCRIV和SCRV的三重PCR方法。为验证该方法的敏感性和特异性(备测病毒为IPNV、GCRV、KHV、SGIV、NNV、TiLV和SVCV),对22份疑似感染ISKNV、SCRIV和SCRV的样品分别进行单一和三重PCR检测。【结果】成功建立了三重PCR检测方法,利用该方法可同时检测ISKNV、SCRIV和SCRV,特异性较好,对IPNV、GCRV、KHV、SGIV、NNV、TiLV、SVCV等无扩增;该方法敏感性好,对3种病毒核酸的检测下限均为0.01 ng/μL;利用该方法和3种病毒单一PCR方法同时对22份临床样品进行检测,结果显示2种方法吻合率为100%,其中ISKNV阳性率为27%、SCRIV 阳性率为41%、SCRV阳性率为9%、ISKNV和SCRIV混合感染阳性率均为9%,无ISKNV、SCRIV和SCRV混合感染。【结论】建立的三重PCR检测方法具有特异性强、灵敏度高等特点,可对这3种病毒进行快速鉴别诊断。     

多株益生菌复合饲料发酵剂的应用效果试验

选择180头"外三元"肥育猪,分小、中、大猪三个试验组,同时饲喂3种试验日粮(即三组饲料原料的发酵产品),每种试验日粮的饲喂量分成3个水平,并以饲喂基础日粮(即全价配合饲料)为对照。饲喂45 d(正试期30 d)后,统计日增重,并屠宰大猪测定猪肉品质。结果表明:与单纯饲喂基础日粮相比,添加试验日粮Ⅰ、试验日粮Ⅱ、试验日粮Ⅲ的育肥猪的生产性能明显提高,日均增重分别提高了13.6%～17.1%(P<0.05)、1.8%～8.9%、3.5%～13.8%,肉质明显改善,猪肉滴水损失分别降低了33.72%、16.17%2、2.61%,且肌肉粗蛋白、肌肉脂肪含量有不同程度的提高。     

旱涝对豫东地区冬小麦产量的影响评估

利用正交多项式等多种数学方法对豫东地区冬小麦产量的构成进行了分析,在此基础上用积分回归的方法建立了旬降水量与冬麦产量的回归方程,揭示了不同时期旱涝对产量的影响。根据豫东地区冬小麦生育期内各旬降水量影响系数,分析了该地区旬降水量对冬小麦生产影响的地区差异性。     

不同种植方式对黄菖蒲、水葱和菖蒲3种挺水植物生长的影响

以黄菖蒲、水葱与菖蒲3 种挺水植物为材料,在常规种植密度下设置纯植、块状混植与株间混植3种种植方式,分析不同种植方式对植株生长的影响。结果显示,黄菖蒲与菖蒲共同种植其伸长率(ER)均高于纯植方式;块状混植方式下黄菖蒲的平均生长速率(AGR)高于纯植方式,而菖蒲的AGR 则低于纯植方式;株间混植方式下两者的AGR均高于纯植方式。两者分别与水葱株间混植时,水葱的ER 在块状混植与株间混植方式下均比纯植方式高,而菖蒲与黄菖蒲的ER 则均比纯植方式低;株间混植时水葱与黄菖蒲的AGR 均低于纯植方式,菖蒲的AGR 在块状混植方式下比纯植方式低,株间混植方式下则与纯植相当。结果表明,菖蒲与黄菖蒲株间混植有利于相互植株的较快增加和生物产量的较快累积,体现出相互促进效应;而它们与水葱株间混植时,水葱会通过快速的株高伸长,对菖蒲与黄菖蒲形成一定的抑制效应。     

Management of nematodes and a stalk borer by increasing within-field sugarcane cultivar diversity

The aim of this study was to determine whether an increase in plant diversity could modify the structure of the nematode community in favour of less pathogenic species and whether it affected the lepidopteran stalk borer, Eldana saccharina . Four sugarcane cultivars were planted either singly or as a mixture in the furrow. Nematodes were enumerated when the crops were 6 months old for five successive 10 to 13 month old crop cycles. Results showed that the mixture of cultivars had little significant impact on the overall abundance of the plant-parasitic or free-living nematodes. However, the nematode community structure within the mixture was slightly different to that observed on any single cultivar planted on its own and there was a higher than expected proportion of Helicotylenchus dihystera during the first three crops. With successive crops and in all treatments, there was an overall trend of increasing proportions of Meloidogyne javanica in the nematode community. However, the way that the change in the species-balance occurred in the mixed cultivar plots suggested a resistance to the evolving dominance of M. javanica . These results showed that sugarcane cultivars interacted within the rhizosphere when planted in a mixture because the observed nematode community in the mixture differed from that expected. The level of damage caused by E. saccharina was slightly lower in the mixture than expected from the actual cultivar composition.     

Genetic diversity and mixed infections of begomoviruses infecting tomato, pepper and cucurbit crops in Nicaragua

Begomoviruses were detected in Nicaraguan fields of tomato ( Lycopersicon esculentum ) and adjacently growing plants of pepper ( Capsicum annuum ), chilli pepper ( C . baccatum ), cushaw ( Cucurbita argyrosperma ) and Mexican fireplant ( Euphorbia heterophylla ) using polymerase chain reaction (PCR) and universal begomovirus primers. All tomato and Mexican fireplant plants showing symptoms were infected with begomoviruses, while only 30–46% of the pepper, chilli pepper and cushaw plants showing symptoms tested virus-positive. No begomoviruses were found in potato. The virus species were provisionally identified by sequencing 533 bp of the viral coat protein gene ( AV1 ). Tomato severe leaf curl virus (ToSLCV), Tomato leaf curl Sinaloa virus (ToLCSinV) and Pepper golden mosaic virus (PepGMV) were found to infect both tomato and pepper. A new provisional species designated Tomato leaf curl Las Playitas virus (ToLCLPV) was detected in a tomato plant. Squash yellow mottle virus (SYMoV) and PepGMV were found in cucurbits, the latter for the first time in this host. Euphorbia mosaic virus (EuMV) was detected in Mexican fireplant. Sequencing of a larger number of PCR-amplified clones from selected plants revealed intraspecific viral sequence variability, and also multiple begomovirus infections which could represent up to three species in a single tomato or cushaw plant. Phylogenetic grouping of virus sequences did not correlate with the host of origin.