Predicting effective doses for the joint action of two fungicide applications

A function was derived to predict fungicide efficacy when more than one application of a single active ingredient is made to a crop, given parameters describing the dose–response curves of the component single-spray applications. In the function, a second application is considered to act on that proportion of the total pathogen population which was uncontrollable at the time of the first application (represented by the lower asymptote of the dose–response curve for the first treatment), plus any additional part of the population which survived the first application as a result of a finite dose being applied. Data to estimate the single-spray dose–response curve parameters and validate predictions of two-spray programme efficacy were obtained from separate subsets of treatments in four field experiments. A systemic fungicide spray was applied to wheat at a range of doses, at one or both of two times (t₁ and t₂), in all dose combinations. Observed values of the area under the disease progress curve (AUDPC) for septoria leaf blotch (Mycosphaerella graminicola) were used to construct response surfaces of dose at t₁ by dose at t₂ for each culm leaf layer. Parameters were estimated from single-spray and zero-dose treatment data only. The model predicted a high proportion (R² = 71–95%) of the variation in efficacy of the two-spray programmes. AUDPC isobols showed that the dose required at t₂ was inversely related to the dose at t₁, but the slope of the relationship varied with the relative timings of t₁ and t₂ in relation to culm leaf emergence. Isobols were curved, so the effective dose – the total dose required to achieve a given level of disease suppression – was lower when administered as two applications.     

Long-term impacts of an organophosphate-based regime of pesticides on field and field-edge Collembola communities

During a 6-year study, effects of two contrasting regimes of pesticide use on pitfall and suction catches of Collembola were monitored in an arable field under a rotation of grass and winter wheat. Current farm practice (CFP) represented conventional fungicide and herbicide use plus applications of organophosphorus (OP) insecticides, whereas reduced input approach (RIA) utilised minimum inputs of fungicides and herbicides and excluded any use of insecticides. Compared with RIA, the CFP regime caused a substantial decline in the abundance and diversity of Collembola in the field, including the local disappearance of one species, without recovery during the study. At the field edge, which was protected during OP applications by a 6-m unsprayed buffer zone, effects of the CFP regime were less severe, and were not persistent in the long term. Some Collembola species occurred only in field-edge samples. Pitfall and suction sampling yielded remarkably similar patterns of catches, indicating that pitfall trapping may be appropriate for detecting long-term changes in collembolan abundance caused by intensive agricultural management practices.     

Retrospective analysis of trends and production factors associated with sow mortality on swine-breeding farms in USA

Of the 825 pig farms in USA that mailed in their electronic file containing production records, 604 farms were used to observe breeding-female mortality risk and related factors (herd size, lactation length, parity and season). Multiple regression was used to determine factors associated with annual mortality risk. Analyses of variance were used for comparisons of mortality risks among parity and season groups. Average annual mortality risks during the 1997 period was 5.68%. Average breeding-female inventories and average lactation length on USA farms were 733 and 18.3 days, respectively. Higher annual breeding-female mortality risk was associated with larger herd size, greater parity at farrowing and shorter lactation length (P<0.02). For example, as herd size increases by 500 females, mortality risk increases by 0.44%. Older parity was associated with higher mortality risks. Summer season was also associated with higher mortality risk. Using five-years’ records on 270 farms, annual mortality risk in 1997 was higher than those of 1993 and 1994, while average breeding-female inventory increased and lactation length decreased. It is recommended that producers, especially in large herds, pay more attention to breeding females.     

Effects of chilled drinking water on the performance of lactating sows and their litters during high ambient temperatures under farm conditions

Heat stress has detrimental effects on lactating sows and their litters, including decreased feed intake and milk production in sows and decreased weight gain in their offspring. It also increases respiration rate, rectal temperature, and weaning to estrus interval in sows. This study was conducted to investigate the effects of chilled water (CW) on the performance of lactating sows and their litters exposed to high ambient temperatures for 21 days. Ninety multiparous sows (Yorkshire × Landrace; parity range: 2 to 5) and their litters (Yorkshire × Landrace × Duroc) were divided into 3 blocks (30 each). Sows and their litters within each block were randomly assigned to one of the three treatment groups (n = 10 each). Each group was provided with drinking water at 10, 15, or 22 °C (control) under farm conditions where ambient temperature above 25 °C was consistent during the experimental period. Sows on CW (both 10 and 15 °C) consumed more feed and water than did control (P < 0.01) and higher estimated milk production compared with control (P < 0.01), but had lower rectal temperature and respiration rate compared with control (P < 0.01). Mean weaning weight (P < 0.01) and average daily gain (P < 0.01) of litters in CW groups were higher than those in control group. There were no differences in the measured variables, with the exception of the respiration rates, between the two CW treatment groups. These results suggest that CW may improve the performance of sows and their litters exposed to high ambient temperatures and the 15 °C water, from an energy viewpoint, may be more effective.     

皖西地区适于水牛泌乳的牧草筛选试验

在基础日粮相同的基础上,将24头泌乳期、产奶量相近的水牛随机均分3组,探讨禾本科多花黑麦草(Lolium multiflorum.Hercules)、豆科紫花苜蓿(Medicago sativa.Eureka)、蓼科鲁梅克斯(Rumex.K-1)3种牧草对其泌乳高峰期生产性能的影响,结果表明,饲喂Rumex.K-1分别比Eureka和Hercules提高了15.76%、13.39%(P＜0.05)的产奶量,6.32%、6.73%(P＜0.01)的乳脂率,以及21.27%、19.15%的4%标准乳;而Eureka与Hercules间差异均不显著(P＞0.05)。故种植Rumex.K-1适合皖西地区农村散养水牛的小区放牧或舍饲补饲。     

仔猪哺乳期的生长发育分析

为了研究哺乳期仔猪的生长发育规律,为猪的育种和仔猪培育提供科学依据,对西北农林科技大学教学实验农场种猪场1998-2002年生产的1871头长白种猪和140头大约克种猪的初生重、20日龄体重、60日龄体重(断奶重)的测定结果进行分析,利用累积生长、绝对生长、相对生长、生长系数等度量生长发育速度和强度的指标对长白猪和大约克猪两个品种的仔猪及同一品种内不同性别的仔猪在哺乳期的生长发育速度和强度进行了统计分析。用长白仔猪、大约克仔猪的测定结果对其初生重、生长系数、绝对生长采用单因子二水平组内重复数不等资料进行方差分析。结果表明,长白仔猪的平均初生重比大约克猪低1.6%,经方差分析差异不显著(P>0.05);仔猪在出生后20日龄、60日龄两个阶段长白猪的生长发育速度(绝对生长)、生长强度(相对生长)均高于大约克猪,经方差分析差异均显著(P<0.05);而同一品种内,公猪的平均初生重大于母猪,20日龄时公猪的生长发育速度高于母猪,而至60日龄(即断奶时)时母猪的生长发育速度超过公猪,在20日龄、60日龄时公猪的生长发育强度均小于母猪。     

基于ANN的复垦土壤水分特征曲线的预测研究

为能较容易且更准确地获取复垦土壤水分特征曲线,将易测定的土壤特性如土壤质地、容重和饱和含水量作为输入变量,采用基于bagging算法的神经网络法建立了用于预测土壤水分特征曲线的土壤转换函数法(PTFs)模型,并对徐州矿区复垦土壤的水分特征曲线进行了预测,同时与普通BP算法预测精度进行了比较.研究结果表明所建立的PTFs参数模型具有较高的估计精度,bagging算法均方根预测误差比普通BP算法减少了7.5%～27.0%,说明该模型的建立与求解为复垦土壤水分特征曲线的预测研究提供了一条新途径.     

A method of production data analysis for multi-fractured horizontal well in shale gas reservoir

Production data analysis is an effective method of evaluating gas in place, parameters of reservoir and hydraulic fractures. Current model of production data analysis fails to make sense because of the existence of absorption, multi-fracturing, and stimulated reservoir volume (SRV). Considering the effect of desorption, fracture interacting and closed boundary, the authors calculate the productivity of multi-fractured horizontal well in shale gas by Laplace transform and pressure superposition principle. Then theoretical charts of Agarwal-Gardner production decline curves are presented by employing new definition of dimensionless material balance time and dimensionless production, which is based on asymptotic approximations. The result shows that Agarwal-Gardner curves can be divided into two parts where they are scattered in early transient period, and where their shape was influenced by parameters relevant to adsorption, position of each fracture and reservoir geometry, and then drawn to Arps harmonious decline in pseudo steady state period. Reservoir parameters, hydraulic fracture characteristics and gas in place are evaluated by using the type curve matching with actual production data.     

Composition and diversity of five major forest types in moist temperate climate of the western Himalayas

The present study was undertaken in five major forest types (dominated by Quercus semecarpifolia, Quercus floribunda, Acer acuminatum, Abies pindrow and Aesculus indica, respectively) between 2400 and 2850 m a.s.l. in a moist temperate forest of the Mandal-Chopta area in the Garhwal region of Uttarakhand, India. The aim was to assess the variation in composition and diversity in different vegetation layers, i.e., herb, shrub and tree, among these five forest types. Diversity indices, such as the Shannon-Wiener diversity index, density, total basal cover, Simpson’s concentration of dominance index, Simpson’s diversity index, Pielou’s equitability, species richness, species heterogeneity and β-diversity, were calculated to understand community structures. Dominance-diversity curves were drawn to ascertain resource apportionment among various species in different forest types.     

散乱数据光顺拟合的SOR方法

针对CAGD中散乱数据光顺拟合的一般模型的求解问题，采用罚函数方法处理几何约束。根据最优性条件，将反映曲面光顺性的泛函极小化问题，离散化为曲面参数域网格点上的九点差分格式。得到了关于拟合曲面在网格点上函数值的线性方程组，并证明了该线性方程组的系数矩阵对称正定的性质．保证了采用超松弛法求解线性方程组的收敛性。为了验证所提出方法的有效性，对空间散乱分布的14个数据点，当模型参数取不同值时。分别进行了拟合。试验结果表明，用超松弛法能够简单快速实现散乱数据点的光顺拟合。