共查询到20条相似文献,搜索用时 9 毫秒
1.
2.
3.
4.
5.
[目的]明确基于MATLAB的BP神经网络预测温室草皮腾发量的可行性。[方法]在9月温室实测气象资料的基础上,对温室内的平均气温、相对湿度、光照强度和草皮日腾发量(ET)进行回归分析,建立了BP网络ET预报模型(BP-ET)。[结果]气温、光照强度与草皮腾发量呈显著正相关(P<0.05),相对湿度与草皮腾发量呈显著负相关(P<0.05)。BP神经网络模型具有极高的拟合精度,9月资料检验预报模型的平均相对误差为5.58%,模拟与检验均有很高的拟合精度。BP网络可以用于草皮日腾发量的预测,是对传统草皮日腾发量计算的补充。[结论]该研究为气象数据缺测条件下温室草皮日腾发量的估算提供了新思路。 相似文献
6.
Site-specific management (SSM; also called, precision agriculture) is the management of agricultural crops at a spatial scale smaller than that of the whole field. Widespread farmer adoption of SSM practices is contingent on its economic advantage. Three criteria that must be satisfied in order for SSM to be justified are, (1) that significant within-field spatial variability exists in factors that influence crop yield, (2) that, causes of this variability can be identified and measured, and (3) that, the information from these measurements can be used to modify crop management practices to increase profit or decrease environmental impact. The objective of this paper is to review the state of SSM at the turn of the millennium and to offer some speculation as to its future course. The review is organized around the essential components of SSM listed above, i.e. measuring spatial variability, analyzing the data obtained from these measurements, using information gained from this analysis to effect changes in management practices, and determining whether the resulting benefits are worth the costs. The discussion section considers some potential effects of large-scale adoption of SSM, should this adoption occur. 相似文献
7.
红壤丘陵区作物耗水需水的研究 总被引:2,自引:0,他引:2
本文利用水分蒸渗仪对赣东北低丘红壤区的几种主要作物(花生、水稻、荞麦)需水耗水规律进行了研究,其结果表明:生产1kg的花生荚果需要消耗1.31m3水量用于作物腾发;生产1kg的稻谷则需要消耗0.76m3水量用于作物的腾发;而生产1kg荞麦籽实需要消耗1.23m3水量用于作物的腾发。与其对应的水分利用率(WUE)分别为7.65kg/mm·hm2、13.95kg/mm·hm2和8.10kg/mm·hm2。作为一般规律,作物的产量在一定范围内与腾发量成线性关系,因此,每公顷产3000kg花生需要3930m3(或393mm)的水量维持腾发;每公顷产7500kg水稻则需要5700m3(或570mm)的水量用于腾发;而每公顷产3750kg的荞麦籽实产量需4605m3(或461mm)的水量。在田间条件下,设计作物需水量时还应考虑地表径流和水分的渗漏与下渗的情况。试验结果还表明:水稻的水分利用率要高于花生和荞麦,在规划和配置灌溉水时,应优先考虑水稻的供水。 相似文献
8.
9.
采用一种嵌入AutoCAD内部基于对象的集成编程环境VBA来绘制齿轮齿廓,本文给出了具体实现方法和程序片段,探讨并验证了这种方法的可行性。 相似文献
10.
节水型都市种植业发展思路探讨 总被引:1,自引:1,他引:0
目前太原市农业正处在城郊农业向现代都市农业转型的重要时期,发展都市农业为主导的现代化农业是太原市农业发展的必然选择。水资源短缺是困扰太原市农业发展的重要因素之一,种植业作为农业中的耗水大户,又是重中之重。为适应现代农业发展要求,对太原市种植业结构进行合理调整,发展节水型都市种植业是当前太原市农业发展的迫切需要。 相似文献
11.
Dirk Zoebl 《Agriculture and Human Values》2002,19(3):173-187
Halfway through the 20thcentury, a curious shift took place in theconcept and definition of the agronomic termcrop water requirements. Where these cropneeds were originally seen as the amount ofwater required for obtaining a certain yieldlevel, in the second half of the 20thcentury, the term came to mean the water neededto reach the potential or maximum yield in acertain season and locality. Some of themultiple academic, economic, social, andgeopolitical aspects of this conceptual shiftare addressed here. The crucial role of theproduction ecologist Cees de Wit in formulatingthis paradigmatic shift in the 1950s isdiscussed. It is seen how the incipient concernfor an expected global scarcity of waterresources has contributed to a trend back tothe conservative view of crop water control ofde Wit. The development over the years ofengineering and agricultural science conceptsconcerning irrigation and crop water control ispresented as an evolution from practicalhusbandry to specialized applied science;from an empirical, ecological approach to amainly physical/mathematical discipline. Inthe section ``The scientific heritage of Occamand Bacon,' it is argued that this developmentregarding irrigation is part of a general trendin agricultural (and other) sciences andtechnologies over the last 150 years, althoughtendencies to return to a more holisticapproach have, at times, occurred. The current mainstream concepts and methodsin the art and science of crop water control,far from being objective and value-free, oftenact as ``a siren song' for decision-makersresponsible for daily irrigation practice andregional or global water resource management.The seductive ``tune' of maximum yields,concurrently the highest crop water use, drownsout the more modest aim of making anefficient use of the available waterresources. The latter's allure might,however, become the morecompelling as a greater scarcity ofphysical water resources becomes moreimportant than scarcity of land and labor. 相似文献
12.
13.
14.
水资源是重要的自然资源,也是生态系统的构成要素.在我国积极深化自然资源管理制度改革,推进生态文明制度建设的关键时期,水资源管理制度改革也迫在眉睫.梳理了当前我国水资源管理的体制和制度现状,认为当前我国水资源管理存在着多部门分割管理、水资源产权制度不健全、水资源生态功能管理缺乏的主要问题.为了顺应生态文明建设和自然资源综合管理的需要,提出了水资源管理要向水资源综合管理、水资源产权制度明晰和“数量、质量、生态管控”三位一体管理的趋势发展.今后水资源管理的改革,要推进水资源管理体制改革,促进水资源综合管理;建立水资源产权制度,发展水资源市场;创新管理理念,促进水资源生态文明建设;重视基础性工作,加强水资源管理的信息化建设;严格水资源管理责任,完善水资源管理考核制度. 相似文献
15.
16.
17.
土地信息系统在大面积范围内旱灾遥感监测中的应用 总被引:4,自引:0,他引:4
本文讨论以土地信息系统为工具,利用作物缺水指数模型在大面积范围内监测旱情的方法及可行性。作为国家“八·五”攻关项目的一部分在黄淮海平原进行了实时监测,结果表明:基于土地信息系统的图像、图形、数据一体化处理基本上达到了准确,实时监测干旱的目的。 相似文献
18.
19.
[目的]对当归在不同水肥处理下的需水量进行研究,为当归灌溉制度研究及GAP规范化种植提供理论依据。[方法]通过小区田间试验,依据试验结果进行理论统计分析,分析了当归在不同灌水施肥处理下的土壤水分变化规律、需水量和作物系数。[结果]不同处理0~37 cm深度土壤含水率变化、表层土壤含水率变化起伏较大,随着深度增加,土壤含水率变化较小;不同水肥处理对当归阶段需水量的影响,需水量与灌水量大小成正比,灌水量越大,需水量越高;在适宜灌溉条件下,当归整个生育期的日耗水强度从0.16~4.03不等,作物系数为0.37~1.26,全生育期需水量592.98 mm;当归的整个生育期作物系数变化趋势是先增大后减小。[结论]该研究结果对制定当归种植灌溉制度和GAP规范意义重大。 相似文献
20.
A large portion of irrigation farmers make use of subjective (intuition) irrigation scheduling methods as supposed to objective or scientific irrigation scheduling methods, which need to be changed. The BEsproeiingsWAterbestuursprogram (BEWAB+) irrigation scheduling programme is based on the water balance equation and needs: (1) a crop production function; (2) a relative consumptive water demand curve and (3) an allowable depletion subroutine. The objective of this paper was to describe research aimed at obtaining information on (1) and (2) for pea and also to describe the effect of water application on yield and water use of pea. BEWAB+ uses this information to estimate the daily irrigation water requirements for a particular soil-crop-atmosphere system under irrigation. A field experiment, based on published line-source irrigation methodology, was conducted on a 3 m deep loamy fine sand Bainsvlei or Ustic Quartzipsamment soil near Bloemfontein (26°08′S; 29°01′E) in South Africa. Results showed that there is a linear relationship of the form Ys = 8.07ET - 249 (r2 = 0.91), where Ys is the seed yield of pea (kg/ha) and ET is evapotranspiration for the growing season (mm). The relative consumptive water demand curve is represented by the following third order polynomial function that describes the relationship between time and relative ET for a pea growing season of 120 days: ETrelx = 0.09419646 - 0.01302413x + 0.00059008x2 - 0.00000371x3. ETrelz denotes relative ET and x denotes time in days. A workable balance between practical problem solving and advanced irrigation science has been established with BEWAB+. Pre-plant irrigation schedules can be made for semi-arid areas with the BEWAB+ programme using easily obtainable inputs, like target yield, soil depth and soil particle size distribution information. 相似文献