Irrigation Scheduling and Watermelon Yield Model for the Jordan Valley

A crop yield and soil water management simulation model (CRPSM) developed at Utah State University was modified, calibrated and tested using local weather data and field results from a trickle irrigation experiment with different mulching on watermelon ( Citrullus lanatus ), carried out at the University of Jordan Research Station, in the Jordan Valley.
Simulated irrigation schedules were then applied with some of the four options provided by the model. The water yield index, WYI, introduced by B attikhi and H ill (1985) to select the most efficient schedule as based on yield and water use efficiency, was then determined. WYI ranged from 27 to 87. The field schedule, WM₂, had a WYI of 62. Whereas, the model provided a much better schedule, WM₇ (WYI = 86). WM₇ requires 17 irrigations of 2.0 cm per irrigation totaling a water supply of 44.1 cm with an irrigation season starting on April 7 to give a yield equivalent to the potential yield, 80.0 MT/ha. On the other hand, the best field schedule, WM₂ under transparent mulch, required 14 irrigations to provide 45.9 cm (including rainfall and soil moisture change), with a season starting on April 28 resulted in a yield of 68.8 MT/ha. So we can see that by using the same amounts of total water supply but with different schedule we can get the potential yield. The model has, therefore, provided few better schedules that can be tested in the field at lower costs before final recommendations are made.     

资金限制情况下投资项目的最优组合决策模型

资金限额条件下投资项目的最优组合是某些企业经常遇到的问题。对这些项日进行组合与投资安排，不仅要考虑各项目的投资额大小，还要考虑项目投资先后顺序、先期投资项目的盈利对后期投资项目所得资金的补充等情况。为此，建立了两类常见的资金限制情况下的最优组合决策问题的优化模型，并举例进行了计算。     

Response of grain yield and related agronomic traits of oilseed flax to diversified cropping rotations北大核心CSCD

This research aimed to identify a suitable planting pattern for oilseed flax production in a dry-farming region. A long-term field experiment was started in 2012 with a 4-year crop rotation cycle,designed to measure the effects on flax crop performance of previous crop,and various patterns of flax planting interval within the four-year rotation,compared with continuous flax cropping. Crop parameters measured included plant height,stem diameter,dry matter accumulation and distribution,and the experiment included six different crop rotation patterns：Flax→flax →flax→flax［（F）FFF］;Flax→wheat→potato→flax［（F）WPF］;Flax→potato→flax→wheat［（F）PFW］;Flax→ flax→wheat→potato［（F）FWP］;Flax→wheat→flax→potato［（F）WFP］and flax→wheat→potato→wheat［（F）WPW］. Results for the ninth year showed significantly increased grain yield（29. 89%-109. 57%）in crop rotation treatments compared with continuous cropping of oilseed flax. The ranking of the six tested rotations for yield was：（F）WPW>（F）FWP>（F）WFP>（F）PFW>（F）WPF>（F）FFF. The grain yield of oilseed flax was significantly affected by previous crop,frequency and years interval of flax cropping and number of years of continuous flax cropping. Yield was increased by 54. 45%-59. 29% under wheat stubble and potato stubble compared with oilseed flax stubble,and increased by 30. 66% and 109. 57%,respectively,under 50% and 25% frequencies,compared with 100% frequency. The grain yield of oilseed flax under two-year continuous cropping was higher by 29. 89% than four-year continuous cropping,and increased with increase in years interval between flax crops. Correlation analysis identified a significantly positive correlation between oilseed flax grain yield and effective capsule number,branch number and 1000-seed weight. The effective capsule number,branch number and 1000-seed weight of oilseed flax under rotation treatment were increased by 35. 88%-108. 91%,15. 47%-46. 19% and 14. 61%-16. 34%,respectively（P<0. 05）,compared with continuous cropping. In addition,the high grain yield of oilseed flax was accompanied by an increase in plant height,stem diameter and dry matter accumulation and these increases were,respectively,5. 11%-42. 24%,2. 77%-39. 92% and 31. 25%-117. 89% under the rotation regimes,compared with continuous cropping. Reduction in the number of years of continuous cropping years,change of crop stubble,decreased flax planting frequency and increased of interval between flax crops also improved flax crop performance. In summary,crop rotation improved the vigor of oilseed flax,resulting in greater plant height and stem diameter,improved dry matter accumulation and distribution,leading to increased branch number,effective capsule number and 1000-seed weight,and increase in the crop yield of oilseed flax. The results indicated that a multiple-crop rotation pattern was an effective way to avoid the yield reduction caused by continuous cropping in oilseed flax. The rotation： Flax→wheat→potato→wheat performed best among those tested and can be recommended as an appropriate cropping rotation for oilseed flax production in the dry region of northwest China. © 2022 Editorial Office of Acta Prataculturae Sinica. All rights reserved.     

林区汽车液体粘性辅助制动系统研究

提出了一种新型的林区汽车辅助制动系统——液体粘性辅助制动系统，详细介绍了其制动原理，通过建立数学模型对其制动性能进行分析，并给出了在两种典型的林区路况下该辅助制动系统作用时车辆系统动态响应的计算机仿真结果.     

加快云南热作产业发展的思考

概述了云南主要热带、亚热带作物的生产现状及存在问题,提出加速该省热作产业健康发展的思路和主要措施.     

FSS系列桥梁伸缩缝的计算机仿真分析

采用ANSYS通用分析软件,对FSS系列桥梁伸缩缝进行了计算机仿真分析,并详细介绍了用AN-SYS仿真分析的过程。对伸缩缝锚固装置及伸缩缝与加强混凝土间的受力及抗裂性能进行分析,通过与试验值的比较,验证了仿真结果的真实、可靠性。     

摘叶模拟食叶害虫危害对杨树生长的影响*

摘叶模拟食叶害虫危害对杨树生长的影响高瑞桐，秦锡祥，陈德钧，卢永农关键词损失模拟，食叶害虫，杨树我国杨树害虫种类繁多，危害程度差别很大。有关专家曾作过杨树摘叶对生长影响的报道［１～３］，对指导害虫的防治有一定作用，特别是超越补偿作用在农作物上被发现并...     

农林复合模式耗水特征的数值模拟——模型的建立与检验

运用土壤—植物—大气水分传输理论，建立农林复合模式的土壤分层水量平衡模型。主要公式有：土壤蒸发与植被蒸腾、林木与小麦根系吸水、土壤层次间的水分交换及植被冠层截留量等水分要素的计算。模型的求解采用数值计算法，并利用０～２００ｃｍ土壤容积含水量的实测值进行验证。研究表明：可以利用所建立的模型，模拟计算林带与小麦根系吸水量、林带与农田蒸散耗水量、林带影响农田土壤水分范围与程度。     

礼县核桃丰产栽培技术

核桃丰产的栽培是通过土肥水管理、整形修剪、病虫害防治等管理技术措施,提高核桃优质产量,进一步改变礼县贫穷山区的落后面貌,不断增加农民经济收入。     

A review of stand basal area growth models

Growth and yield modeling has a long history in forestry. The methods of measuring the growth of stand basal area have evolved from those developed in the U.S.A. and Germany during the last century. Stand basal area modeling has progressed rapidly since the first widely used model was published by the U.S. Forest Service. Over the years, a variety of models have been developed for predicting the growth and yield of uneven/even-aged stands using stand-level approaches. The modeling methodology has not only moved from an empirical approach to a more ecological process-based approach but also accommodated a variety of techniques such as: 1) simultaneous equation methods, 2) difference models, 3) artificial neural network techniques, 4) linear/nonlinear regres-sion models, and 5) matrix models. Empirical models using statistical methods were developed to reproduce accurately and precisely field observations. In contrast, process models have a shorter history, developed originally as research and education tools with the aim of increasing the understanding of cause and effect relationships. Empirical and process models can be married into hybrid mod-els in which the shortcomings of both component approaches can, to some extent, be overcome. Algebraic difference forms of stand basal area models which consist of stand age, stand density and site quality can fully describe stand growth dynamics. This paper reviews the current literature regarding stand basal area models, discusses the basic types of models and their merits and outlines recent progress in modeling growth and dynamics of stand basal area. Future trends involving algebraic difference forms, good fitting variables and model types into stand basal area modeling strategies are discussed.