Tomato yield, biomass accumulation, root distribution and irrigation water use efficiency on a sandy soil, as affected by nitrogen rate and irrigation scheduling

Florida is the largest producer of fresh-market tomatoes in the United States. Production areas are typically intensively managed with high inputs of fertilizer and irrigation. The objectives of this 3-year field study were to evaluate the interaction between N-fertilizer rates and irrigation scheduling on yield, irrigation water use efficiency (iWUE) and root distribution of tomato cultivated in a plastic mulched/drip irrigated production systems. Experimental treatments included three irrigation scheduling regimes and three N-rates (176, 220 and 230 kg ha⁻¹). Irrigation treatments included were: (1) SUR (surface drip irrigation) both irrigation and fertigation line placed right underneath the plastic mulch; (2) SDI (subsurface drip irrigation) where the irrigation line was placed 0.15 m below the fertigation line which was located on top of the bed; and (3) TIME (conventional control) with irrigation and fertigation lines placed as in SUR and irrigation being applied once a day. Except for the “TIME” treatment all irrigation treatments were controlled by soil moisture sensor (SMS)-based irrigation set at 10% volumetric water content which was allotted five irrigation windows daily and bypassed events if the soil water content exceeded the established threshold. Average marketable fruit yields were 28, 56 and 79 Mg ha⁻¹ for years 1-3, respectively. The SUR treatment required 15-51% less irrigation water when compared to TIME treatments, while the reductions in irrigation water use for SDI were 7-29%. Tomato yield was 11-80% higher for the SUR and SDI treatments than TIME where as N-rate did not affect yield. Root concentration was greatest in the vicinity of the irrigation and fertigation drip lines for all irrigation treatments. At the beginning of reproductive phase about 70-75% of the total root length density (RLD) was concentrated in the 0-15 cm soil layer while 15-20% of the roots were found in the 15-30 cm layer. Corresponding RLD distribution values during the reproductive phase were 68% and 22%, respectively. Root distribution in the soil profile thus appears to be mainly driven by development stage, soil moisture and nutrient availability. It is concluded that use of SDI and SMS-based systems consistently increased tomato yields while greatly improving irrigation water use efficiency and thereby reduced both irrigation water use and potential N leaching.     

基于非接触式速度测量的排种驱动系统

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基于AT89S51的汽车智能安全报警系统

利用AT89S51设计了一种新型汽车防盗报警系统.当满足报警条件,单片机会向GSM模块发出指令,系统向机主终端发出报警求助短信,同时还发出声光报警、切断发动机电源.本系统具有误报率小,可靠性高,成本低,使用方便等优点.     

监控系统图象信号传输线缆的选择

论述了监控系统图象信号传输中同轴电缆、双绞线和光纤的特点和传输特性，并对其技术性能进行了分析。     

自适应巡航系统在汽车中的应用

阐述了汽车自适应巡航系统的作用、工作原理和关键技术,介绍了其在国内外的研究应用情况,并对自适应巡航系统未来发展趋势作了探讨.     

基于时空双序列分析的温室WSN故障诊断

根据温室无线传感器网络(WSN)所采集数据在时间和空间上具有很强的相关性,从温室无线传感器网络基本结构出发,在分析WSN原始数据的基础上,通过对时空序列样本信息的预处理,分别建立了时间和空间故障诊断数学模型,据此分析传感节点的工作状态,给出了温室WSN故障诊断的综合算法.研究结果表明,该故障诊断方法能够及时、有效地发现温室WSN的异常并诊断出故障节点,提高了WSN工作的可靠性.     

PASSAT领驭2.0自动变速箱偶尔出现紧急运行状况检修分析

结合PASSAT领驭2.0轿车偶尔出现自动变速箱Ⅲ挡运行的紧急运行状况故障,分析了故障码、有关传感器电路,以及故障产生的原因,据此找出了故障点,并排除了故障。     

基于一线总线声波传感器的监控系统

将单片机与声波传感器结合,设计了一种单总线声波传器件,并以此器件为基础设计了对环境声波信号进行循环采集和监测智能的系统。系统上位机既可以以点名方式选择让任意一个下位机进行数据传送,也可在轮巡方式工作。由于本系统结构简单、成本低廉,可广泛用于多种场合的声音监控中。