简单屋顶绿化的滞蓄特性   总被引：2，自引：0，他引：2  

张华  李茂  张沣  曹金露  袁密 《保鲜与加工》2015,(4):135-141

设计了模拟降雨与数据采集系统,研究了短时强降雨下简单屋顶绿化基质(配比：陶粒57.0%、草炭41.5%、保水剂1.5%)的降雨产流过程,基于37次模拟降雨实验,归纳了降雨产流的一般过程、规律和特性,分析了降雨强度、基质厚度和基质初始含水率对简单屋顶绿化滞流蓄水特性的影响。结果表明：基质厚度和基质初始含水率对简单屋顶绿化的蓄水特性有显著影响,基质初始含水率越低、基质厚度越厚时蓄水特性越佳。建立了产流时间数学模型,简单屋顶绿化降雨产流时间与降雨强度呈负相关,同时也受初始含水量和基质厚度影响。随着干湿循环次数增加,基质的厚度总体呈现下降趋势,储水性能逐渐下降,延迟产流时间逐渐缩短。  相似文献   

Using midday stem water potential for scheduling deficit irrigation in mid–late maturing peach trees under Mediterranean conditions     

José Manuel Mirás-Avalos  Francisco Pérez-Sarmiento  Rosalía Alcobendas  Juan José Alarcón  Oussama Mounzer  Emilio Nicolás 《Irrigation Science》2016,34(2):161-173

Irrigation techniques that reduce water applications are increasingly applied in areas with scarce water resources. In this study, the effect of two regulated deficit irrigation (RDI) strategies on peach [Prunus persica (L.) Batsch cv. “Catherine”] performance was studied over three growing seasons. The experimental site was located in Murcia (SE Spain), a Mediterranean region. Two RDI strategies (restricting water applications at stage II of fruit development and postharvest) based on stem water potential (Ψ_s) thresholds (?1.5 and ?1.8 MPa during fruit growth and ?1.5 and ?2.0 MPa during postharvest) were compared to a fully irrigated control. Soil water content (θ_v), Ψ_s, gas exchange parameters, vegetative growth, crop load, yield and fruit quality were determined. RDI treatments showed significantly lower values of θ_v and Ψ_s than control trees when irrigation water was restricted, causing reductions in stomatal conductance and photosynthesis rates. Vegetative growth was reduced by RDI, as lower shoot lengths and pruning weights were observed under those treatments when compared to control. However, fruit size and yield were unaffected, and fruit quality was slightly improved by RDI. Water savings from 43 to 65 % were achieved depending on the year and the RDI strategy, and no negative carryover effect was detected during the study period. In conclusion, RDI strategies using Ψ_s thresholds for scheduling irrigation in mid–late maturing peach trees under Mediterranean conditions are viable options to save water without compromising yield and even improving fruit quality.  相似文献   

Measured and estimated water use and crop coefficients of grapevines trained to overhead trellis systems in California’s San Joaquin Valley     

Larry E. Williams  Matthew W. Fidelibus 《Irrigation Science》2016,34(6):431-441

The use of overhead trellis systems for the production of dry-on-vine (DOV) raisins and table grapes in California is expanding. Studies were conducted from 2006 to 2009 using Thompson Seedless grapevines grown in a weighing lysimeter trained to an overhead arbor trellis and farmed as DOV raisins for the first two years and for use as table grapes thereafter. Maximum canopy coverage for the two lysimeter vines across years was in excess of 80 %. Seasonal (15 March–31 October) evapotranspiration for the lysimeter vines (ET_Lys) was 952 mm in 2007 (farmed as DOV raisins) and 943 and 952 mm (when farmed as table grapes). The maximum crop coefficient (K _cLys) across all 4 years ranged from 1.3 to 1.4. These maximum values were similar to those estimated using the relationship where K _c is a function of the amount of shaded area measured beneath the canopy at solar noon (K _c = 0.017 × percent shaded area). Covering the lysimeter’s soil surface with plastic (and then removing it) numerous times during the 2009 growing season (1 June–14 September) reduced ET_Lys from an average of 6.4 to 5.6 mm day^?1 and the K _c from 1.07 to 0.93. A seasonal basal K _c (K _cb) was calculated for grapevines using an overhead trellis system with a 13 % reduction in the K _cLys across the growing season.  相似文献   

Crop response of drought-tolerant and conventional maize hybrids in a semiarid environment     

Ryan B. Mounce  Susan A. O’Shaughnessy  Brock C. Blaser  Paul D. Colaizzi  Steven R. Evett 《Irrigation Science》2016,34(3):231-244

In the High Plains, corn (Zea mays L.) is an important commodity for livestock feed. However, limited water resources and drought conditions continue to hinder corn production. Drought-tolerant (DT) corn hybrids could help maintain high yields under water-limited conditions, though consistent response of such hybrids is unverified. In this two-year study, the effects of three irrigation treatments were investigated for a DT and conventional maize hybrid, Pioneer AQUAMax P0876HR and Pioneer 33Y75, respectively. In 2013, the drier of the 2 years, irrigation amounts and crop water use (ET_c) were greater for the conventional hybrid, but grain water use efficiency (WUE) and harvest index were significantly greater for the DT hybrid. In 2014, grain yields and WUE were not significantly different between hybrids. However, irrigation amounts, ET_c and biomass yields were greater for the conventional hybrid. Results from both years indicate that the DT hybrid required less water to maximize grain yield as compared to the conventional hybrid. Producing relatively high yields with reduced amounts of water may provide a means for producers to continue corn production in a semiarid environment with declining water supplies.  相似文献   

基于多信息融合的疫苗制备中鸡蛋胚体分拣系统   总被引：1，自引：0，他引：1  

徐彦伟  徐爱军  颉潭成  崔建鹏  毛恒轩  刘守川 《农业机械学报》2015,46(2):20-26

采用多信息融合方法研究疫苗制备中鸡蛋胚体状态的识别与分拣技术。在研究不同状态鸡蛋胚体图像特征、温度衰减和透光度变化情况的基础上,得出活胚图像中血管多、粗且呈放射状,弱胚图像中血管少、细且断裂,死胚图像内部均匀无血管,污染胚图像内部有明显黑块特征;鸡蛋胚体从37.8℃的孵化箱中取出置于25℃室温环境,活胚、弱胚、污染胚、死胚的温度衰减速度依次增大;活胚的透光度随孵化时间增加而逐渐降低,其他胚体透光度变化相对较小。将图像、温度、透光度信息特征融合,建立BP神经网络信息融合模型对鸡蛋胚体状态进行识别。最后,从37.8℃孵化箱中抽取80枚孵化6 d的鸡蛋胚体放置于室温10 min后,采集图像、温度和透光度信息,进行试验验证。结果表明多信息融合系统的识别准确率为96.25%,比单用图像、温度和透光度传感器进行识别的准确率分别提高了6.25%、13.75%和8.75%。  相似文献   

Modeling soil water dynamics in a drip-irrigated intercropping field under plastic mulch     

Xianyue Li  Haibin Shi  Jiří Šimůnek  Xuewen Gong  Zunyuan Peng 《Irrigation Science》2015,33(4):289-302

Intercropping, drip irrigation, and the use of plastic mulch are important management practices, which can, when utilized simultaneously, increase crop production and save irrigation water. Investigating soil water dynamics in the root zone of the intercropping field under such conditions is essential in order to understand the combined effects of these practices and to promote their wider use. However, not much work has been done to investigate soil water dynamics in the root zone of drip-irrigated, strip intercropping fields under plastic mulch. Three field experiments with different irrigation treatments (high T1, moderate T2, and low T3) were conducted to evaluate soil water contents (SWC) at different locations, for different irrigation treatments, and with respect to dripper lines and plants (corn and tomatoes). Experimental data were then used to calibrate the HYDRUS (2D/3D) model. Comparison between experimental data and model simulations showed that HYDRUS (2D/3D) described different irrigation events and SWC in the root zone well, with average relative errors of 10.8, 9.5, and 11.6 % for irrigation treatments T1, T2, and T3, respectively, and with corresponding root mean square errors of 0.043, 0.035, and 0.040 cm³ cm^?3, respectively. The results showed that the SWC in the shallow root zone (0–40 cm) was lower under non-mulched locations than under mulched locations, irrespective of the irrigation treatment, while no significant differences in the SWC were observed in the deeper root zone (40–100 cm). The SWC in the shallow root zone was significantly higher for the high irrigation treatment (T1) than for the low irrigation treatment, while, again, no differences were observed in the deeper root zone. Simulations of two-dimensional SWC distributions revealed that the low irrigation treatment (T3) produced serious severe water stress (with SWCs near the wilting point) in the 30–40 cm part of the root zone, and that using separate drip emitter lines for each crop is well suited for producing the optimal soil water distribution pattern in the root zone of the intercropping field. The results of this study can be very useful in designing an optimal irrigation plan for intercropped fields.  相似文献   

基于纹理和位置特征的麦田杂草识别方法   总被引：14，自引：5，他引：14  

曹晶晶  王一鸣  毛文华  张小超 《农业机械学报》2007,38(4):107-110

以化学防除适期麦田杂草为研究对象，对利用条播作物的位置和纹理特征识别田间杂草的方法进行了研究。根据条播作物小麦作物行的间距相对固定等位置特征，利用植物像素直方图法确定作物行的中心线和行宽，并识别行间杂草。然后，以作物行中心为基准来选取纹理块，计算量化级数为8级的H颜色空间的共生矩阵，提取5个纹理特征参数，利用K均值聚类法判别分析各块的类别来识别行内杂草。研究结果表明，杂草的正确识别率约为93％，作物的错误识别率约为7％。  相似文献   

磁吸式精密排种原理分析与试验   总被引：9，自引：4，他引：9  

胡建平  毛罕平 《农业机械学报》2004,35(4):55-58

针对蔬菜、花卉种子体积小、质量小及形状不规则的特点 ,提出了一种新的排种方式——磁吸式精密排种。应用有关磁选理论 ,建立了磁吸式精密排种的力学模型 ,得出了单粒磁粉包衣种子在气隙磁场中所受磁力的计算公式 ,分析了实现精密排种的基本条件。通过对白菜、番茄种子的排种试验 ,其单粒精播率达 90 % ,漏播率低于5 % ,说明这一排种方式具有较高的播种精度和对不同类型种子良好的适应性。  相似文献   

Sensitivity analysis of optimal operation of irrigation supply systems with water quality considerations     

Dani Cohen  Uri Shamir  Gideon Sinai 《Irrigation and Drainage Systems》2004,18(3):227-253

A model for optimal operation of water supply/irrigation systems of various water quality sources, with treatment plants, multiple water quality conservative factors, and dilution junctions is presented. The objective function includes water cost at the sources, water conveyance costs which account for the hydraulics of the network indirectly, water treatment cost, and yield reduction costs of irrigated crops due to irrigation with poor quality water. The model can be used for systems with supply by canals as well as pipes, which serve both drinking water demands of urban/rural consumers and field irrigation requirements. The general nonlinear optimization problem has been simplified by decomposing it to a problem with linear constraints and nonlinear objective function. This problem is solved using the projected gradient method. The method is demonstrated for a regional water supply system in southern Israel that contains 39 pipes, 37 nodes, 11 sources, 10 agricultural consumers, and 4 domestic consumers. The optimal operation solution is described by discharge and salinity values for all pipes of the network. Sensitivity of the optimal solution to changes in the parameters is examined. The solution was found to be sensitive to the upper limit on drinking water quality, with total cost being reduced by 5% as the upper limit increases from 260 to 600 mg Cl l^–1. The effect of income from unit crop yield is more pronounced. An increase of income by a factor of 20 results in an increase of the total cost by a factor of 3, thus encouraging more use of fresh water as long as the marginal cost of water supply is smaller than the marginal decrease in yield loss. The effect of conveyance cost becomes more pronounced as its cost increases. An increase by a factor of 100 results in an increase of the total cost by about 14%. The network studied has a long pipe that connects two distinct parts of the network and permits the supply of fresh water from one part to the other. Increasing the maximum permitted discharge in this pipe from 0 to 200 m³ h^–1 reduces the total cost by 11%. Increasing the maximum discharge at one of the sources from 90 to 300 m³ h^–1 reduces the total cost by about 8%.  相似文献   

拖拉机电液悬挂系统中CAN总线智能节点研究   总被引：1，自引：3，他引：1  

谢斌  毛恩荣 《农业机械学报》2006,37(12):1-3,16

针对用插装阀组成的拖拉机电液悬挂系统，给出了基于CAN总线的悬挂控制方案，主要包括悬挂子系统ECU、2个智能节点。智能节点的设计以LPC2119芯片为核心，具有硬件简单、封装小巧、软件模块化强的特点。试验表明，该节点能很好地满足悬挂系统的工作要求。  相似文献