Evaluation of two N cycle models for the prediction of N mineralization from grassland soils in the UK

Abstract. The ability of two nitrogen cycle models, of contrasting complexity, to predict N mineralization from a range of grassland soils in the UK, was evaluated. These were NCYCLE, a simple mass balance model of the N cycle in UK grasslands, and CENTURY, a more complex model simulating long-term C, N, P & S dynamics in grassland ecosystems. The models were tested using field measurements of net N mineralization from a range of grassland soils (differing in soil type, history & management practice), obtained over a 2 year period using a soil core incubation technique. This method was considered to measure the total net release of mineral N from the soil organic matter over a specified time, including N which may have been recycled several times. NCYCLE consistently under-estimated mineralization rates at all sites. By contrast, there was some correlation between CENTURY predictions of net N mineralization and field measurements. This may have reflected the different abilities of the two models to simulate N recycling. Neither model, however, was able to predict adequately the effect of cultivation and reseeding on net N mineralization.     

垂直换向悬挂翻转五铧犁的虚拟设计

虚拟设计是设计者在虚拟环境中运用交互手段在计算机内建立产品模型,并进行模拟仿真。为此,结合铧式犁传统的平面设计,就垂直换向悬挂翻转五铧犁进行了虚拟设计,从而使设计人员能够从理论认识到感性认识对铧式犁进行设计、分析和评价,为后期开发系列化铧式犁提供了数字化设计平台。     

奶牛杂交群体及其遗传评估的模拟研究

为验证在奶牛杂交群体中将品种组成和杂合度作为协变量的遗传评估理论,为奶牛杂交模式选择和杂交群体遗传评估等实际问题提供理论依据,结合我国奶业现状,本研究模拟了在低产荷斯坦牛群引入法系蒙贝利亚牛、德系西门塔尔牛进行杂交,采用随机交配和三品种轮回杂交模式、群体世代重叠17年的繁育过程.群体杂合度在第7年后趋于平衡,轮回杂交模式的群体杂合度高于随机交配.经过杂交,原中低产荷斯坦牛群体在产奶性能、生长性能方面都有进展,轮回杂交提高幅度相对略高.此外,利用品种效应和杂合度效应剖分杂种优势,采用单性状和多性状动物模型对模拟群体进行遗传评估,效果基本一致,都可以很好地用于杂交群体的遗传评估.结果表明,对荷斯坦牛中低产群体进行杂交,可实现生产性能和效益的提高,回归模型可用于多元群体的遗传评估.     

土壤—作物资源多目标优化配置分析

本文提出一种多目标土壤—作物资源优化配置的数量化分析方法,并对江苏省东海县土壤资源进行优化配置。结果表明：白浆土、岭砂土、包浆土、紫砂土等岗岭低产土应稳定小麦面积,压缩玉米面积,优先发展春花生、大豆、水稻;洼地砂姜黑土、水稻土应发展小麦—水稻和小麦—玉米两熟制,并适时换茬;介于上述两类土壤间的潮棕壤亚类和潮土类应大力发展小麦—花生两熟制。     

伊克昭盟牧草和饲料作物应用增产菌技术的试验

199年伊克昭盟引入了牧草和饲料作物增产菌这一技术,经过7年的试验,示范及推广,至今全盟该增产菌应用面积已达4．04万hm^2,本文通过7年来在两种不同生境下,对12种牧草及作物的不同物修期采用不同方法施用增产菌,以鲜草产量和种子产量为衡量标准来探讨增产菌对不同牧草及作物的增产效果,实验结果表明：增产菌技术的应用,促进了植物的生长,使植株长高,叶面积增大,加强了光合作用,在提高鲜草产量的同时也增加了籽实的产量,具有较强的推广价值,是一项在农牧区适用的增产技术。     

吉林省主要粮食作物比较优势分析

根据比较优势理论，应用综合比较优势指数法对吉林省玉米、水稻、大豆三种主要粮食作物在1997-2005年间的比较优势变动趋势进行了分析，其结果表明：三种作物中，玉米具有明显的比较优势，大豆次之，水稻则处于劣势，但呈现出稳步上升的趋势；并在此基础上提出了吉林省主要粮食作物结构调整的建议。     

LDSO: a program to simulate pedigrees and molecular information under various evolutionary forces

Simulations are a major tool to evaluate new statistical methods and optimize experimental designs in the genomic era. However, this can only be achieved when the simulations are close enough to reality, as well as diverse enough to be realistic. For mapping studies, it is thus critical to re-create as much as possible the forces generating linkage (mutation, random drift, changes in population sizes, selection and pedigree structure) and the mechanisms producing trait genetic architecture (additivity, dominance, epistasis). We present here a computer program (ldso) simulating these phenomena. Optional outputs provide statistics on the linkage disequilibrium (LD) structure and the identity by descent between chromosomal segments, facilitating further data analyses. Furthermore, ldso enables the simulation of genomic data in known pedigrees, which sticks as precisely as possible to recent population history and structures of the long-range LD, allowing optimization of fine-mapping strategies.     

贵州省生物天然气发展现状及农作物秸秆资源潜力

对贵州省现阶段生物天然气工程发展的现状进行了阐述,研究了贵州省发展生物天然气存在的问题和困难,并统计了各市州农作物秸秆资源可收集量,计算出了生物天然气的生产潜力,以期为生物天然气的制备和利用提供参考。     

绿色富硒牧草饲料作物生产技术规程

本规程规定了绿色富硒牧草饲料作物的生产基地环境、种植区域分布、生产管理、刈割利用、票证管理等内容,并制定了牧草饲料作物硒含量达到0.01～0.1mg/kg的产品标准.     

论酒泉市农作物秸秆资源饲料化利用的现实与前景

农作物秸秆资源具有重要的饲料价值,该文以酒泉市秸秆饲料化利用为切入点,探究农作物秸秆饲料化利用前景,为酒泉市构建生态循环农业和资源节约型社会提供新的视角和思路。