Use of organic carbon and loss-on-ignition to estimate soil organic matter in different soil types and horizons

Summary Loss-on-ignition (LOI) and the organic C content have been used to estimate soil organic matter. Organic matter is often estimated from organic C by applying a factor of 1.724. Several authors have examined the relationship between LOI, used as an estimate of organic matter, and C by simple linear regressions. In the present study, this approach was examined in relation to two sets of data. LOI overestimates organic matter in soils with significant proportions of clay minerals because of bound water, and correcting for bound water gives some LOI: C ratios of less than 1. It is concluded that differences in the nature of the organic matter in different soils and horizons make the simple regression approach unsuitable. More attention needs to be paid to studies of the nature of the organic matter.     

重庆市城镇化率变化影响因素分析——基于回归分析法

首先通过对重庆市城镇化水平的预测,确定重庆市在2020年城镇化率达到65％的可能性。主要通过文献研究确定影响重庆市城镇化率变化的影响因素,进而利用统计学方法建立了城镇化率与各个影响因素的之间的回归分析模型,然后对模型所得结果的相关性进行统计性分析后,最后把对各影响因素在重庆市城镇化率变化的过程中按所起的正、负相关影响进行归类分析。旨在为重庆市在提高城镇化率过程中对相关因素的控制着力点上提供相关的参考依据。     

黔油18号高产综合农艺措施数学模型研究

【目的】为明确影响高原生态区黔油18号油菜产量的关键因子及实现高产高效优化栽培的综合农艺措施。【方法】运用四因素二次回归最优组合设计试验方法,在海拔950￣1200m的高原生态区对优良杂交油菜新品种黔油18号的主要栽培措施施氮量、施磷量、施钾量与油菜产量的量化关系进行系统研究,通过建立数学模型的优化与解析,【结果】结果表明,在4因素中,对黔油18号的影响为氮肥>密度>磷肥>钾肥;【结论】要获得≥2493.46kg/hm2的产量,其最佳栽培措施组合是:保持密度13.60￣14.50万株/hm2,氮肥291.35￣330.00kg/hm2,磷肥92.28￣102.2746kg/hm2,钾肥119.20￣129.20kg/hm2。     

线性回归分析中重复与非重复性问题研究

本文就一元线性回归，分相同水平及不同水平两种情形，讨论了重复与非重复试验对回归方程精度的影响，得到如下结论：相同水平序列下，重复试验的回归精度高于非重复试验；不同水平序列下非重复试验的回归方程的精度在一定条件下可能高于重复试验，并给出了此时应满足的水平设置条件。     

Relation of soil organic matter concentration to climate and altitude in zonal soils of China

With a total of 886 data sets distributed in different regions of China, the relation of soil organic matter (SOM) concentration to climate and altitude was investigated. These data sets were obtained from the 2nd National Soil Survey of China that was completed in early 1980s. According to climate gradient and vegetation community succession, six geographical regions, including eastern, southern, northern, northeastern, northwestern and southwestern China, were divided to identify the key factors regulating surface SOM concentration in different geographical regions. Correlation analysis indicates that surface SOM concentration is in general negatively correlated with annual mean temperature (T) and positively correlated with annual mean precipitation (P) and altitude (H). A further investigation suggested that multiple regression models with different combination of T, P and H could explain 41.5%–56.2% of the variability in surface SOM concentration for different geographical regions, while the driving variables are different. Variables of T and P determined surface SOM concentration in northern, northeastern and northwestern China. In eastern and southern China, variables of P and H are key factors regulating surface SOM concentration. Surface SOM concentration in southwestern China is determined by a linear combination of T, P and H.     

玉米新品种高产稳产适应性综合评判

对于玉米新品种的高产稳产适应性评判,方法种种,但各有利弊.采用高稳系数(HSC)法、变异系数(CV)法、回归系数(b)法综合分析玉米新品种的高产稳产适应性.结果表明,新品种的高产稳产适应性得到客观真实的反映。     

农户对农业科技服务满意度评价及其影响因素分析——基于1033个农户的调查数据

科技是第一生产力,农业科技服务是推动农业科技进步的重要力量,在提高农业生产效率、增加农民收入及促进农业发展等方面起着越来越重要的作用。基于来自全国111个行政村、1 033个农户的调研数据,运用描述统计方法和有序Logistic模型,对农户对农业科技服务满意度评价及其影响因素进行了实证研究。结果表明,农户对农业科技服务满意度评价处于中等偏下的水平。在1%显著性水平下,农户参加过科技培训、家中有电脑、东部地区变量、村里有科技服务组织、村里有科技宣传这五个变量对农业科技服务满意度评价有显著的正向影响;在5%显著性水平下,村里有科技服务人员对农业科技服务满意度评价有显著的正向影响。最后,依据实证分析结果从提高农业科技服务供给水平和改善农户获取农业科技信息的方式这两个方面给出了提高农户对农业科技服务满意度评价的政策建议。     

“矮败”小麦回交群体若干重要性状的相关分析

用矮败小麦不育株为母体，40个普通小麦品种（系）为父本连续回交三次，共衍生出120份后代群体，通过对各群体的不育株，可育株的株高，穗长，千粒重等性状的相关分析，探讨了“矮败”基因回交转育的效应。不育株：连续注入父本遗传种质，对其各性状素现影响较小。其株高一般45cm左右，回交几代后，高秆父本衍生的后代略高于中矮秆父本的后代。与可育株相比，其穗子较长，小穗数多，但千粒重较低，开花一般迟2－14d，而早花父本衍生的后代花期也早，迟花父本后代花期较迟。可育株：性状表现与父本关系密切，并随回交世代的增加而逐渐接近父本，其F1，BC1F1，BC2F1各世代群体株高依父本株高的直线回归方程分别为：YF1＝56.210 0.3194X,YBC1F1=40.435 0.5119X,YBC2F1=21.F687 0.7759X.大穗多花多粒的父本衍生的可育株一般也是大穗多花多粒，千粒重大都表现超父优势，早花父本衍生的可育株花期早于迟花父本后代。     

应用多元回归原理预测初产母牛产奶量的研究

通过黑龙江省香坊实验农场奶牛场50头初产牛90天、120天估测305天产奶量的回归方程：y＝851．93－1．485X1＋3．115X2，经检验准确度（R）可达88．57％．在生产实践中，利用此方程可以90天和120天的产奶记录，提前选择对奶牛育种工作起重点作用的初产母牛．     

玉米新品种展示结果丰产性与适应性分析

分析结果表明 ,全省不同试点间生产水平存在着极显著差异 ,品种间差异小于试点间差异 ,但还存在着极显著差异。其中DH330 3丰产性好、适应性强 ,豫玉 2 2、农大 36 8适合于在高水肥条件下种植 ,中单 94 0 9、中单 12 3在瘠薄条件下种植能获得较高产量