Evaluation of the VegSyst model with muskmelon to simulate crop growth, nitrogen uptake and evapotranspiration

Like many intensive vegetable production systems, the greenhouse-based system on the south-eastern (SE) Mediterranean coast of Spain is associated with considerable NO₃⁻ contamination of groundwater. Drip irrigation and sophisticated fertigation systems provide the technical capacity for precise nutrient and irrigation management of soil-grown crops which would reduce NO₃⁻ leaching loss. The VegSyst crop simulation model was developed to simulate daily crop biomass production, N uptake and crop evapotranspiration (ET_c). VegSyst is driven by thermal time and consequently is adaptable to different planting dates, different greenhouse cooling practices and differences in greenhouse design. It will be subsequently incorporated into a practical on-farm decision support system to enable growers to more effectively use the advanced technical capacity of this horticultural system for optimal N and irrigation management.VegSyst was calibrated and validated for muskmelon grown in Mediterranean plastic greenhouse in SE Spain using data of four melon crops, two grown in 2005 and two in 2006 using two management strategies of water and N management in each year. VegSyst very accurately simulated crop biomass production and accurately simulated crop N uptake over time. Model performance in simulating dry matter production (DMP) over time was better using a double radiation use efficiency (RUE) approach (5.0 and 3.2 g MJ⁻¹ PAR for vegetative and reproductive growth phases) compared to a single RUE approach (4.3 g MJ⁻¹ PAR). The simulation of ET_c over time, was very accurate in the two 2006 muskmelon crops and somewhat less so in the two 2005 crops. The error in the simulated final values, expressed as a percentage of final measured values was −1 to 6% for DMP, 2-11% for crop N uptake, and −11 to 6% for ET_c. VegSyst provided effective simulation of DMP, N uptake and ET_c for crops with different planting dates. This model can be readily adapted to other crops.     

Greenhouse gas emissions from the Canadian dairy industry in 2001

In order to demonstrate the impact of an increase in production efficiency on greenhouse gas (GHG) emissions, it is important to estimate the combined methane (CH₄), nitrous oxide (N₂O) and carbon dioxide (CO₂) emissions per unit of production. In this study, we calculated the GHG emissions from the Canadian dairy industry in 2001 as a fraction of the milk production and per dairy animal. Five regions were defined according to the importance of the dairy industry. N₂O and CO₂ emissions are directly linked with areas allocated to the dairy crop complex which includes only the crop areas used to feed dairy cattle. The dairy crop complex was scaled down from sector-wide crop areas using the ratios of dairy diet to national crop production of each crop type. Both fertilizer application and on-farm energy consumption were similarly scaled down from sector-wide estimates to the dairy crop complex in each region. The Intergovernmental Panel on Climate Change (IPCC) methodology, adapted for Canadian conditions, was used to calculate CH₄ and N₂O emissions. Most of the CO₂ emission estimates were derived from a Fossil Fuel for Farm Fieldwork Energy and Emissions model except for the energy used to manufacture fertilizers. Methane was estimated to be the main source of GHG, totalling 5.75 Tg CO₂ eq with around 80% coming from enteric fermentation and 20% coming from manure management. Nitrous oxide emissions were equal to 3.17 Tg CO₂ eq and carbon dioxide emissions were equal to 1.45 Tg. The GHG emissions per animal were 4.55 Mg CO₂ eq. On an intensity basis, average GHG emissions were 1.0 kg CO₂ eq/kg milk. Methane emissions per kg of milk were estimated at 19.3 l CH₄/kg milk which is in agreement with Canadian field measurements.     

三种土地利用方式下南方高山土壤温室气体通量特征及其影响因子研究

为探讨湖北火烧坪三种土地利用方式下土壤温室气体排放的特征及其影响因子,以研究区农田、草地和天然林地为研究对象,采用野外原位静态箱-气相色谱法对其土壤温室气体通量动态变化进行监测,并对环境因子进行分析。结果表明：三种土地利用方式下土壤CO₂均表现为排放,农田土壤CH₄和N₂O表现为排放,草地表现为吸收,林地不一致;土壤含水量抑制土壤CO₂,促进土壤CH₄产生,过氧化氢酶活性与土壤CO₂和CH₄的排放具有显著相关性,有机肥的施用影响土壤N₂O的排放;全球增温潜势（Global warming potential,GWP）由大到小表现为草地 > 林地 > 农田,但草地由于生物量高光合呼吸作用强,向大气排放CO₂的总量则较低。因此,人工草地的建造有利于降低研究区土壤温室气体的排放。     

气候变化与害虫的生长繁殖,越冬和迁飞

以粘虫、稻飞虱为例，分析了气候变暖对害虫生长、繁殖代数、越冬界限、迁飞等生态学特征的影响。结果表明，气候变暖，积温增加将会使粘虫、稻飞虱的繁殖代数增加，越冬界限北移，迁飞范围扩大，从而使害虫的发生时间延长，危害程度加重。     

基于改进遗传算法的温湿度模糊神经网络控制器

为了创造适合作物生长的环境,针对温室系统的特点,该文提出了一种基于改进遗传算法的模糊神经网络控制器,利用改进遗传算法训练模糊神经网络模型,采用此模糊神经网络控制器控制温室系统,由数值实验可以看到采用此控制器的温室系统具有响应速度快、过程平稳、编程简单的特点.     

温室大棚蔬菜生产中滴灌带灌溉应用效果分析

在温室大棚蔬菜生产中应用膜下软管滴灌技术，能为作物生长发育创造良好的水、肥、气、热等生态环境，使温室大棚内５～１５ｃｍ土壤层平均温度提高１．５～２℃，气温平均提高０．５℃，空气相对湿度降低１０％～１５％，改善土壤理化性状，减轻病害，省水、省肥、省农药，促进蔬菜早熟，增产增收     

宁夏不同地区温室土壤养分的变化特点

根据宁夏温室的分布状况,按照不同地区分别采集了温室和露地土壤,分析了土壤N、P、K养分含量的变化特点。结果表明,温室土壤的N、P、K养分含量明显高于露地,表现为相对累积,其顺序依次是NO3--N>速效P>速效K>碱解N>全P>全N。从不同地区来看,土壤N、K含量总体上是灌区高于山区,而土壤全P和速效P含量在两地区间差异不显著,但各养分含量的变异系数都是山区大于灌区。从不同县级地域来看,温室土壤养分含量在平罗县、兴庆区、西夏区、青铜峡市、中卫县、原州区、盐池县之间存在显著或不显著差异,其中盐池县的各养分含量最低,均显著低于其他各市县。     

设施栽培中逆境对园艺作物生长发育及其病害的影响

根据近年来国内外的相关研究进展,针对设施园艺生产中普遍出现的作物生长不良和病害严重等问题,在分析设施内各环境因子改变的基础上,综述了光照不足、温湿度不适、土壤次生盐渍化、酸化、养分失衡以及土壤生物学环境恶化等设施逆境对作物生长发育及其病害的影响。     

中国现代温室的主要型式及其性能

目前我国正处在温室设施大发展的年代,大型温室年增长量在百公顷以上,温室型式也各种各样,如何根据当地条件和种植内容,选择经济有效的温室型式及其合理配置是每个温室建设者所首要解决的问题。“九五”期间,在大量引进学习国外温室及其种植技术的基础上,我国温室设施也有了前所未有的发展。但由于温室规范措施滞后,各类温室设计制造,尤其是设计、选型和配套技术还很不成熟,给温室建设者合理选择温室带来了一定困难。针对我国大量发展的温室型式,包括玻璃温室、塑料温室和PC板温室,就其结构特点、主要技术性能进行了分析和阐述,以期为温室设计和建造提供必要的技术依据     

基于证据理论的温室投资风险效益评估专家系统

通过建立温室投资风险效益评估指标体系,利用修正层次分析法建立各因素之间的权重,采用D-S证据理论方法建立温室投资风险效益评估模型,并开发温室投资风险效益评估专家系统.系统可通过不同专家进行评估,再进行温室投资方案的综合评估,为温室投资者选择合适的温室结构类型提供参考依据.