钾对大白菜软腐病发生及保护酶活性的影响

[目的]探究钾肥在抗大白菜软腐病中的作用。[方法]以德高秋丰王和北京新三号为试验材料,通过大田试验,研究3个施钾水平下(0、200、400 kg/hm~2K_2O)德高秋丰王和北京新三号大白菜产量、软腐病发病率及保护酶活性的变化。[结果]施钾量为200 kg/hm~2时显著提高德高秋丰王的产量,而北京新三号产量在施钾量达到400 kg/hm2时显著提高;随施钾量的提高,两品种大白菜软腐病病情指数都呈现降低的趋势,施钾量在400 kg/hm~2时,病情指数最低;两品种的PPO和POD的活性都随施钾量的提高而增强。[结论]施钾对大白菜产量的效应因品种不同而异,增施钾肥可以通过提高保护酶的活性降低大白菜软腐病病情指数。     

影响大豆绿肥腐解速率的因素研究

以大豆（沧豆6号）为绿肥材料,在田间采用埋入和覆盖尼龙袋子的方法,研究了不同栽培条件（是否种植玉米）、利用方式（埋入土壤、覆盖在地表）和使用量（200 g/袋、250 g/袋）下绿肥腐解速率的变化。结果表明：大豆绿肥的腐解过程表现为前期腐解快、后期腐解逐渐减慢的特点,在种植玉米条件下比不种植玉米条件下腐解得快,在施用化肥条件下比不施化肥条件下腐解得快,绿肥埋深10 cm比覆盖在地表腐解得快,但差异均不显著;在田间翻埋条件下,大豆绿肥的腐解速率几乎不受翻压量的影响。     

猪繁殖与呼吸综合征灭活疫苗研究进展

<正>猪繁殖与呼吸综合征(Porcine reproductive and respiratory syndrome,PRRS)又称"猪蓝耳病",是由猪繁殖与呼吸综合征病毒(PRRSV)引起的猪的     

红松SRAP-PCR反应体系的优化

通过单因素试验,对红松SRAP—PCR反应体系的主要影响因子（Taq DNA聚合酶、Mg^2＋、模板DNA、dNTPs、引物浓度）进行了优化筛选,得出红松SRAP—PCR反应的最佳体系：20μL反应体系中,模板90ng,Mg^2＋1．0mmol／L,dNTPs0．15mmol／L,Taq DNA聚合酶1．5 U,引物0．3～0．4μmol／L。     

冬种马铃薯不同栽培方式试验

<正>桂平市地处广西东南部,冬季有丰富的光温资源,而秋收后大部分的农田处于闲置。近年来,冬种马铃薯作为一项主要农业生产和农民增收的方式在广西得到了大力推广,我市冬种马铃薯的面积也在不断的扩大,对增加农民收入起到了很大的作用。目前我市的马铃薯     

青海云杉种子萌发特性

以天祝县青海云杉天然种群种子为研究对象,通过对种子生活力测定,分析种子萌发对温度、光照、水分和盐分胁迫的响应,为引种提供参考数据。结果表明：① 种子的生活力为72%。② 在黑暗条件下,温度小于10 ℃种子不萌发,最适萌发温度25/15 ℃(72%);种子在24 h黑暗和24 h光照条件下的萌发率显著高于14 h光照/10 h黑暗。③ 当NaCl胁迫浓度为50 mmol·L^-1时,可促进种子萌发,当胁迫浓度大于50 mmol·L^-1时,抑制种子萌发;胁迫解除后,随着胁迫浓度的增加,恢复萌发率(RGR)先增加后减小,胁迫浓度为400 mmol·L^-1时,RGR达到最大值13%。④ 随着PEG-6000试剂胁迫渗透势的增加,种子萌发显著减少,在-0.9 MPa时,种子不能萌发;胁迫解除后,RGR先增加后减少,在-0.9 MPa时,达到最大值35%。     

依据传统土壤数据应用数字土壤制图法对香港山地地区土壤建立土纲信息

Based on legacy soil data from a soil survey conducted recently in the traditional manner in Hong Kong of China, a digital soil mapping method was applied to produce soil order information for mountain areas of Hong Kong. Two modeling methods (decision tree analysis and linear discriminant analysis) were used, and their applications were compared. Much more eflort was put on selecting soil covariates for modeling. First, analysis of variance (ANOVA) was used to test the variance of terrain attributes between soil orders. Then, a stepwise procedure was used to select soil covariates for linear discriminant analysis, and a backward removing procedure was developed to select soil covariates for tree modeling. At the same time, ANOVA results, as well as our knowledge and experience on soil mapping, were also taken into account for selecting soil covariates for tree modeling. Two linear discriminant models and four tree models were established finally, and their prediction performances were validated using a multiple jackknifing approach. Results showed that the discriminant model built on ANOVA results performed best, followed by the discriminant model built by stepwise, the tree model built by the backward removing procedure, the tree model built according to knowledge and experience on soil mapping, and the tree model built automatically. The results highlighted the importance of selecting soil covariates in modeling for soil mapping, and suggested the usefulness of methods used in this study for selecting soil covariates. The best discriminant model was finally selected to map soil orders for this area, and validation results showed that thus produced soil order map had a high accuracy.     

牛羊布鲁氏菌病的预防措施

布鲁氏菌病（Brucellosis）简称布病，是由布鲁氏菌引起的一种人畜共患的传染病，在家畜中牛、羊较为易感。     

中麻黄生境及栽培因子研究

通过对河西地区中麻黄资源生境调查和栽培学因子及生长规律的试验研究表明:在降水量较大的河西东部,天然中麻黄分布群落较多;随着降雨量递降,中麻黄种群数量和面积递减,生长势也渐弱。中麻黄在轻、中度盐渍化土壤中生长良好,而在重度盐碱地上稀见分布。中麻黄人工种植中,当土壤含盐量在0.2 % 时,对麻黄幼苗的影响小;当土壤含盐量达0.82 % 时,出苗率为41 %,盐害死亡率达48.8 %;当土壤含盐量达0.76 % 时对当年生麻黄苗产生影响。中麻黄虽是强旱生耐瘠薄的植物,但通过合理施肥,适量灌溉等栽培技术能促进其生长发育,只需耕作农田年灌水量的1/2～1/6以及有机肥和速效氮、磷肥为主的适量施肥,就可大大提高单位面积上中麻黄的产量,提高麻黄碱含量。