油菜播栽方案设计的动态知识模型

运用知识工程和系统建模方法,在总结、归纳和提炼油菜生长发育与生态环境、品种类型、生产技术水平和产量目标关系的基础上,建立了具有时空适应性的油菜播栽方案设计的动态知识模型,可用于精确定量不同环境和生产条件下油菜品种的适宜播期、基本苗、播种量和移栽方案.利用南京、郑州和保定3个地点的常年逐日气象资料以及各点不同品种和播种方式资料对播栽方案设计模型进行实例分析,结果表明,该知识模型对播期和基本苗设计均具有较好的决策性、解释性和适用性.     

小麦目标产量设计及适宜品种选择的动态知识模型

运用知识工程和系统建模方法,在综合考虑决策点光温生产潜力、历史平均产量水平、土壤肥力、肥水管理水平和生产技术水平等诸多因子对增产系数影响的基础上,通过定量计算动态增产系数,建立了具有时空适应性的小麦目标产量设计知识模型;通过定量计算小麦品种特征值与环境因子和生产需求之间的符合度,建立了适宜品种选择的量化知识模型．利用南京、郑州、泰安、保定和太原5个不同生态点的不同年型每日气象资料以及不同历史平均产量水平、土壤肥力和肥水管理水平,对目标产量设计模型进行了实例分析;利用广州、南京、泰安、北京、哈尔滨5个不同生态点常年气象资料以及15个不同品种资料,对品种选择知识模型进行了实例分析．结果表明,所建知识模型具有较好的决策性和广泛适应性．     

油菜地上部干物质分配与产量形成模拟模型

利用油菜器官生长与发育进程及环境因子之间的定量关系,构建了基于分配指数的油菜地上部器官干物质分配动态模拟模型.各器官干物质分配指数随着生理发育时间而变化,基因型、播期、氮素及水分水平影响各器官干物质在地上部分配的大小.其中,氮素营养水平对绿色叶片干物质分配影响最大,氮素营养水平越高,绿色叶片分配指数越大;播期影响角果分配指数,晚播的角果分配指数高于早播.模型引入氮素营养指数、水分及播期影响因子来定量油菜各器官在实际生产条件下的分配强度,同时考虑了品种遗传特性的影响.通过不同品种氮肥处理试验建立模型,利用不同品种播期试验资料对模型进行了初步检验,表明模型具有较好的预测性和适用性.     

稻麦适宜氮素营养指标动态的模型设计

以水稻和小麦为研究对象,通过解析和提炼稻麦适宜氮素营养指标与品种类型、栽培技术、生态环境之间的定量关系,以基于生理发育时间（PDT）的相对生长度日和相对氮素营养指标为参数,建立了稻麦适宜氮素营养指标动态模型,并利用南京3年的大田试验资料对所建模型的可靠性和适应性进行了验证.结果表明：模型生成的水稻植株氮积累量和氮含量与实际观测值之间的平均根均方差（RMSE）分别为0.1245和0.1316;模拟的小麦植株氮积累量和氮含量与实际观测值之间的平均RMSE分别为0.1166和0.1301,表明模型对稻麦氮素营养指标动态具有较好的指导性,可为不同生态环境、品种类型和生产条件下的稻麦氮素营养诊断与管理调控提供定量化和精确化的指导.     

吉林省东部粳稻生长和产量对移栽期和温度变化的反应

以中晚熟水稻品种"吉粳811"为研究对象,于2013年和2014年在延吉市进行分期播种/移栽试验,分析了吉林省东部地区一季粳稻生长速度和产量对移栽期及温度变化的响应规律,确定该品种在研究地区的适宜播种期和移栽期,以减免低温冷害的影响。结果表明:播期/移栽期的推迟提升了生长季平均气温,水稻生长发育进程加快,有效生育期缩短,主要生长季内平均气温每升高1℃,水稻生长速率提升19%,生育期缩短5 d左右;吉林省东部地区水稻的适宜移栽温度为日均气温13.0℃,移栽过早或偏晚均导致减产;中晚熟品种水稻在4月18日前后播种、5月26日前后移栽可保证在霜前成熟,且产量高;中晚熟品种水稻移栽至成熟适宜活动积温为2280℃·d左右,活动积温每减少100℃·d,水稻产量下降1095 kg·hm~(-2)(约减产13%);积温不足导致水稻冷害发生,因而减产。     

棉花氮肥和水分运筹的动态知识模型

通过分析和提炼棉花氮肥运筹和水分管理的最新研究资料,在综合考虑气候条件、土壤理化性质、产量目标、品种特性等影响因子的基础上,根据养分平衡原理和水分需求规律,建立了棉花氮肥和水分运筹的动态知识模型．模型可用于精确定量不同环境和不同产量目标下的氮肥和水分需求总量及其在不同生育时期的分配比例等．利用不同生态点、不同品种、不同土壤类型和不同产量目标等资料对氮肥和水分运筹知识模型进行了验证．结果表明模型具有较好的决策性和适应性．     

播期对不同类型品种直播稻生长特性的影响

以具有代表性的3种类型水稻品种为材料,通过分期播种试验,对不同播期条件下直播稻物质生产和产量形成进行了分析。结果表明:随着播期的推迟,3种类型品种水稻产量均显著下降,但变化程度不一;全生育期显著缩短;群体茎蘖消长动态逐渐趋于不平缓,此现象并随播期的推迟而加剧;叶面积指数在生长前期逐渐上升,生长中后期则相对下降;各阶段光合势呈降低的趋势;干物质累积在拔节期递增,在抽穗期和成熟期则递减,收获指数递减;各阶段群体生长率下降趋势显著。对直播稻安全适宜播期进行综合评价表明,该地区宜推广中熟中粳和迟熟中粳品种,可以使用早熟晚粳品种;各类品种在前茬滕茬时间允许的条件下尽可能早播,易取得高产,但从生育安全性来考虑,中熟中粳品种最迟要在6月下旬播种,迟熟中粳品种最迟要在6月中下旬播种,早熟晚粳品种最迟要在6月中旬播种。     

大麦叶面积指数模拟模型

准确模拟叶面积指数是作物生长模拟模型预测作物生长和产量的关键.本文通过系统分析扬州和武汉地区不同大麦品种高产群体叶面积指数变化动态,建立了大麦群体的叶面积指数模拟模型.大麦叶面积指数是品种叶面积指数扩展的遗传参数和气温日较差、日照时数、辐射量等气候因子及水肥丰缺因子的函数.孕穗抽穗期最大叶面积指数与该期最适叶面积指数是不同的概念,二者之间存在着极显著差异.利用扬州、南京和昆明地区不同品种的播期试验及氮肥试验资料对模型进行了检验,结果表明,模型对大麦叶面积指数的模拟效果较好,模拟值与观测值吻合度高,根均方差RMSE介于0.742～2.865,平均值为1.348.对模拟值与观测值进行y=x的线性回归分析,相关系数R²介于0.511～0.954,均呈极显著正相关.     

三化螟种群系统的最优管理决策

以三化螟Tryporyza invertulas(Walker)种群动态模型和水稻产量损失预测模型为基础,根据水稻插植期、品种抗性,保护利用自然天敌和杀虫剂多次使用等控制措施以及它们的各种不同组合对该虫种群动态、水稻产量损失串和净收益的影响,以净收益最大为目标函数,研究三化螟种群的最优管理决策。其中,对昆虫种群动态模拟方法作了一点改进,它综合了前人所提出的种群动态模型的优点。建立的系统模型能够提供包括农业防治、生物防治和化学防治措施在内的、对三化螟种群实施有效管理的最优决策方案。     

基于ORYZA2000模型的北京地区旱稻适宜播种期分析

确定适宜播种期是制定合理的作物栽培管理方案的关键内容之一。在作物模型ORYZA2000有效性验证的基础上,以北京地区为例,利用该模型结合长期历史气候资料,对确定旱稻适宜播种期做了初步研究。结果表明：在不考虑水分因子条件下,北京地区旱稻297安全播期的范围较广,多年平均为3月26日-6月4日;受温度升高的影响,最早播期有提前趋势,而最晚播种期有延后趋势。在同一年份内,播期不同旱稻的产量也有一定的变化,呈现为先升高而后降低的趋势。播期过早或过晚导致生育期平均温度偏低是影响穗干物质累积且造成减产的主要原因,在适宜的播期范围内才能获得高产。以90%-100%当年最高产量潜力作为适宜播期的产量指标,确定北京地区旱稻297的适宜播期变化在5月11日-5月19日之间,相应的产量变化在6689-7257 kg/hm2范围内。研究方法可为其他地区旱稻的播期研究提供借鉴。     

Predicting the seedling emergence time of sugar beet (Beta vulgaris) using beta models

Soil temperature, texture, water content and sowing depth are effective factors on the estimation of emergence time. This research aimed to test the Beta model for its adequacy in predicting the time of emergence for sugar beet. The Beta growth model as a phenological model have been used for evaluating the time of seedling emergences under both controlled environments in laboratory and field conditions. An experiment was conducted both in the laboratory with five soil textures, three sowing depths, five soil water contents and ten constant soil temperatures, under field conditions on five sowing dates (20 February, 28 March, 19 April, 10 May, and 31 May) and three sowing depths. The results demonstrated that the Beta model can predict the time of emergence. Based on the root mean square error (RMSE), the time of emergence estimated by the Beta model was in high agreement with the time of emergence measured in the laboratory. Estimation accuracy was reduced slightly by the Beta model under field conditions. The accuracy of the Beta model was influenced by the sowing date under field conditions. So, on the first and second sowing dates (with low air temperature), the estimation of time of emergence by the model was lower and on the fourth and the fifth sowing date (with warmer air temperature), was more than the duration measured. Estimation accuracy was increased by the Beta model under field conditions using soil temperature. In conclusion, the Beta model can predict the time to emergence of sugar beet seedlings in different levels of soil texture and soil water content under field conditions, and with that, the proper planting date for sugar beet seeds to overcome weeds in different soil water content can be predicted.     

Postponed sowing does not alter the fibre/wood ratio or fibre extractability of fibre hemp (Cannabis sativa)

Because hemp is a short-day plant, postponing the sowing date might be a suitable strategy to obtain shorter and smaller plants around flowering, when primary fibres are 'ripe' enough to be harvested. Smaller plants can be processed on existing flax scutching and hackling lines and might have fibre characteristics that are desirable for producing high-quality 'long fibres' for yarn spinning.
It was investigated whether sowing beyond the normal sowing period in the Netherlands affects the ratio in which fibres and wood are produced, and what proportion of these fibres are long fibres, suitable for long fibre spinning. About 400 stem samples were fractioned into retting losses, wood, tow, and long fibre, and the ratios between fractions were analysed using multiple linear regression analyses.
A normal sowing date at the end of April was compared with a postponed sowing date at the end of May. The total fibre/wood ratio was not affected. More than 95% of the variance in total fibre was accounted for by the wood weight per stem (55.5%), the variety (+33.3%) and the stem part (+6.5%). The amount of long fibre per stem mainly depended on the amount of the total fibre per stem (95.4% variance was accounted for) and the stem part (+2.0%).
For economic reasons, it could be interesting to grow two successive high-quality hemp crops in one growing season. Therefore, in an additional experiment with one variety, the effect of sowing fibre hemp up to 12 weeks later than normal on the quantity and quality of the fibres was studied. Postponing the sowing date up to 12 weeks had no important effects on retting losses, the total fibre/wood ratio, and the long fibre/total fibre ratio. It is therefore technically possible to grow two successive hemp crops. Whether this fits well in farming systems and a hemp production chain remains to be studied.     

利用APSIM模型分析不同播期和耕作方式对旱地小麦籽粒干物质积累的影响

黄土丘陵区旱地小麦籽粒干物质积累的准确模拟可为调控小麦生产提供重要的技术支持。本研究利用甘肃省定西市安定区1971—2017年的气象资料和甘肃省定西市安定区凤翔镇安家沟村2016—2017年的大田试验数据,基于APSIM模型对旱地小麦籽粒干物质积累与分配进行模拟,并在模型验证的基础上,定量分析了播期和耕作方式对小麦籽粒干物质积累的影响。结果表明: 3个播期(早播、正常播、晚播)和4种耕作方式(传统耕作、传统耕作+覆盖、免耕、免耕+覆盖)下,籽粒干物质模拟值与实测值间的均方根误差(RMSE)为57.5～143.1 kg·hm^-2,归一化均方根误差(NRMSE)为1.4%～9.9%,模型模拟精度较高。不同播期下,耕作方式对籽粒干物质积累的促进效果排序均表现为: 免耕+覆盖>传统耕作+覆盖>免耕>传统耕作,免耕+覆盖最有利于小麦籽粒干物质积累,而免耕与传统耕作差异不显著。不同耕作方式下,小麦干物质积累过程均表现为早播好于正常播和晚播,晚播对干物质积累的影响较大,积累过程最不理想。     

不同积温和种植密度对饲用黑麦分蘖动态的影响

应用回归均匀设计构造试验方案,采用分期播种的方法,研究了不同冬前积温、种植密度对饲用黑麦单株分蘖动态、群体分蘖动态以及有效茎数动态变化的影响,并建立了模拟模型。结果表明,饲用黑麦单株分蘖数量同时受播期、播量的影响,生长前期主要受播期早晚的影响,生长后期主要受播种密度的制约,总体来看,播期越早、播量越小,其单株分蘖数量就越多,反之就越少,饲用黑麦不论是在生长前期、中期,还是后期,随着播期推迟,各播量群体分蘖数不断下降;随着播量增大,各播期群体总蘖数不断上升,饲用黑麦群体有效茎数取决于播期和播量的共同作用,播期早,要控制播量不宜过大,合理的群体结构主要依靠单株有效茎数的增长潜力来保证;播期晚,要防止播量过小,合理的群体结构主要依靠主茎数量的增加来实现。     

Variables Aggregation in Time Varying Discrete Systems

In this work we extend approximate aggregation methods in time discrete linear models to the case of time varying environments. Approximate aggregation consists in describing some features of the dynamics of a general system involving many coupled variables in terms of the dynamics of a reduced system with a few number of variables. We present a time discrete time varying model in which we distinguish two time scales. By using perturbation methods we transform the system to make the global variables appear and build up the aggregated system. The asymptotic relationships between the general and aggregated systems are explored in the cases of a cyclically varying environment and a changing environment in process of stabilization. We show that under quite general conditions the knowledge of the behavior of the aggregated system characterizes that of the general system. The general method is also applied to aggregate a multiregional time dependent Leslie model showing that the aggregated model has demographic rates depending on the equilibrium proportions of individuals in the different patches.     

Area under disease progress curve and apparent infection rate of Alternaria blight disease of Indian mustard (Brassica juncea) at different plant age

Plant age has a major influence on the incidence of Alternaria blight disease in Indian mustard crops. Disease progression was monitored twice a week on the two chosen Indian mustard cultivars viz., Varuna and Rohini throughout the season. Severity of blight caused by Alternaria brassicae and Alternaria brassicicola decreased with delay in sowing. Calculation for A-value (Area under disease progress curve – AUDPC) and r-value (apparent infection rate) in crops sown on different dates could identify the speed of progress in the disease on leaves and pods, as the crop does not posses resistance to the pathogen till date. Thus, the probable dates of sowing enabling slow disease progress or the weather conditions coinciding with the different crop phenological stages demarcated the advantageous dates of sowing from the disadvantageous ones. However, cultivar Varuna is more susceptible as compared to the other cultivar Rohini, as apparent infection rate both on leaves and pods was higher in former. Highest per cent disease severity (PDS) for season highly correlated with date of sowing, i.e. delayed date of sowing increased PDS.     

Effect of Sowing Time on Toxigenic Fungal Infection and Mycotoxin Contamination of Maize Kernels

Field experiments were set up from 2000 to 2002 in northwest Italy to determine the effects of sowing date on the susceptibility of maize hybrids to ear rot and mycotoxin contamination in natural infection conditions. Three sowing dates (March, April and May) were compared using two hybrids with different maturity classes. The ears were rated for the incidence and severity of disease symptoms at harvest and the harvested kernels were analysed for mycotoxin fumonisin B₁, zearalenone, deoxynivalenol, aflatoxin B₁ and ochratoxin A. The last sowing date resulted in higher values of European corn borer incidence (+39%), kernel Fusarium infection and fungal ear rot severity (increased respectively by a factor of 4 and 3) than the plots sowed in March. The sowing date did not influence the type of mycotoxin found in the kernel, which only depended on the climatic conditions during the season and on their influence on the infection and the development of the fungal species. The natural occurrence of fumonisin B₁ and deoxynivalenol was always significantly higher in late‐sowed plots. A late sowing, after May 10, multiplies the risk of the occurrence of fumonisins and deoxynivalenol in the grains at harvest by a factor of 11.2 and 1.9, respectively. No significant difference was observed for the contamination of zearalenone or aflatoxin B₁ for the different sowing dates. An earlier sowing time than April, resulted in a significant reduction in mycotoxin contamination only in the years in which the meteorological trend protracted the kernel dry down to the autumn months. The use of a late‐maturity hybrid with late sowing, compared with a medium‐maturity hybrid, could lead to a serious risk of mycotoxin contamination. To the authors’ knowledge, this is the first study to report on the effects of sowing time on maize kernel contamination of mycotoxins other than aflatoxins in non‐inoculated conditions.