土壤剖面水分传感器探头仿真与试验

为准确掌握土壤墒情信息,针对农田环境下不同作物根区土壤含水率变化难以实时观测的问题,对土壤剖面水分传感器探头进行了仿真,并通过试验验证,给出了传感器探头设计尺寸的优选方案。在建立传感器探头微量化平面电容二维模型的基础上,分析了传感器探头结构变化对探头微量化平面电容周围电场强度和电容变化的影响,确定了探头结构尺寸的最优组合。当探头铜环电极外径40 mm、内径38.4 mm、轴向长度20 mm、轴向间距15 mm时,探头的灵敏性和探测范围最优。试验结果表明,本文研究的土壤剖面水分传感器测量精度为±1.42%,具有很高的稳定性和一致性。所设计的传感器探头可以根据实际测量深度需要任意组合,满足不同作物根区深度的土壤含水率测量需求。     

FDR探头结构对土壤介电谱测量的影响分析

为了研究FDR探头结构中探针间距和探针长度对土壤介电谱测量的影响,通过矢量网络分析仪分别对2种土壤的4个不同体积含水率进行了介电谱测量,通过28 mm长度下10 mm、14 mm探针间距探头和10 mm间距下28 mm、45 mm长度探头所测介电谱对比发现,在31.2 MHz以上频段探针间距对土壤介电谱测量影响很小,而探针长度在不同频段对土壤介电实部或虚部均有不同影响。研究表明,探针间距不是土壤介电谱测量的影响因素,根据测量需要可对其进行一定范围的调整;探针长度影响土壤介电谱弛豫频率值,探针越短其弛豫频率越大,探针长度是影响土壤介电谱测量的关键因素之一。FDR探头的探针应适当缩短以拓展介电谱平滑段的频率范围,这有利于FDR传感器测量精度和环境适应性的提高。     

栽培基质超亲水pH传感器测量误差影响因素分析与补偿

栽培基质pH值是设施园艺中重要的生产过程信息之一。针对栽培基质pH值在线检测误差大、结果易受基质含水率和基质成分影响的问题,基于超亲水pH传感器,以泥炭、蛭石基质为原料,以配置的不同质量比和不同含水率的栽培基质为试验对象,开展了栽培基质超亲水pH传感器pH值测量试验研究。结果发现：栽培基质的质量含水率(θ_m)降低会引起超亲水pH传感器的pH值测量值线性降低和pH值测量误差线性增加,其测量误差绝对值最大为0.81,显著低于锑电极pH传感器(测量误差绝对值最大为2.15);超亲水pH传感器的测量误差受混合基质中泥炭、蛭石质量比的影响相对较小,由基质成分变化导致的测量误差最大变化为0.23,显著低于锑电极pH传感器(最大变化为1.10)。在此基础上建立了栽培基质超亲水pH传感器的测量误差补偿模型,并在采集的栽培基质中进行了应用试验;补偿前测量误差绝对值最大为0.32,补偿后降为0.18,测量误差进一步降低,验证了超亲水pH传感器及其测量误差补偿模型的有效性。研究结果为实现栽培基质pH值快速、准确在线检测奠定了基础。     

水稻电阻抗谱分析及检测频率范围的确定

为了确定基于水稻电特性的水稻水分传感器的检测频率范围,以江苏镇江的镇稻十号为研究对象,利用solartron阻抗分析仪1260A+1294及自制电阻盒研究频率(1Hz~1MHz)、水稻含水率(12%~29%)对水稻阻抗模的影响。通过研究发现:随着频率的增大,不同含水率水稻阻抗模逐渐减小,且阻抗模间距逐渐缩小并产生重合,其中低含水率水稻在低频段频率增加的过程中会产生一定幅度的波动;含水率对水稻阻抗模的影响具有频段区域特征,其减小或波动的幅度逐渐减小、趋势具有良好的一致性。通过对水稻阻抗谱的分析,最终确定水稻含水率的检测频率范围为200Hz~2k Hz,为基于复阻抗测量原理的水稻水分传感器的设计提供了重要的实验依据。     

基于含水率与温度补偿的土壤pH值在线实时检测系统

针对目前常用土壤pH值传感器在测量过程中受土壤含水率和温度影响较大的问题,设计了带有温度、含水率补偿模型的锑电极土壤pH值在线实时检测系统。利用最小二乘法对pH值和测量结果进行线性分析,补偿土壤pH值测量误差。试验结果表明,经过补偿之后,由温度和含水率变化导致的pH值测量误差至少可降低84. 5%,pH值测量值随温度和含水率的变化幅度不超过±0. 1。与市场产品ZD-18型土壤酸度计、HYSWR-ARC-12V型土壤含水率传感器、水银温度计对比研究得出,3项指标线性拟合决定系数均达到0. 99以上。为了确保自然环境下土壤pH值测量的适用性,探索了系统在使用过程中土壤含水率的阈值与测量精度,表明在土壤体积含水率大于5%的情况下均可有效测量。试验表明,在pH值3. 06～10. 36范围之内,本系统可有效测量,检测误差为-1. 53%～3. 51%,满足土壤pH值实时在线测量要求。     

淡水鱼鲜度检测系统的阻抗特性测试

采用四电极结构传感器和LabVIEW软件,设计了淡水鱼阻抗测量系统,研究电流激励频率、电极测量方向、电极结构、测量部位与淡水鱼阻抗的关系,为建立基于阻抗特性的淡水鱼鲜度检测系统提供理论基础。试验结果表明:阻抗随激励频率的增大而减小,相位随激励频率的增大而增大;沿鱼体侧线平行测量的阻抗大于垂直侧线测量的阻抗,符合生物组织的各向异性;同一激励频率下不同测量部位的阻抗大小不同;同一部位不同时间阻抗的大小不同;采用混合电极测量鱼体鳃部的信号稳定,规律性强,适于淡水鱼鲜度检测。     

基于频域法传感器的基质含水率检测性能研究

本文对基于频域法FDS-100型土壤含水率传感器在基质含水率中的检测性能进行了研究。首先,对不同配比的基质,使用FDS-100型传感器测量并将测量结果与干燥法得到的标准含水率进行对比,将FDS-100型传感器与ECH2O-5TE型基质含水率传感器在混合基质中的测量性能进行对比,并研究了压实程度、电导率和温度对传感器性能的影响。试验结果表明：FDS-100型传感器在不同配比基质中得到的测量值并不遵循同一曲线;测量值随压实程度增大而增大,测量误差在-1%~10%之间;电导率对测量值有一定影响,测量误差在±5%之间;温度对FDS-100型传感器测量值影响极小,测量误差在2%以下;FDS-100型传感器与ECH2O-5TE型传感器之间的相对误差为4.32%。FDS-100型传感器可用于基质含水率检测,但在实际使用时需要针对不同基质与不同压实程度进行标定。     

基于阻抗和电容的番茄叶片含水率实时监测

为降低基于叶片电特性的番茄营养状况实时监测系统中叶片含水率对营养监测准确性的影响,提高营养水平监测模型的精度,提出一种基于叶片阻抗和电容的含水率实时测量方法,利用自制的针状电极设计了一种基于叶片阻抗和电容的4电极含水率监测系统。以不同含水率的番茄叶片为对象,在1×10-6~1 MHz的频率范围内研究了番茄叶片含水率对阻抗的影响规律,提取了叶片含水率的敏感频段,并建立了基于阻抗和电容的各生育期的叶片含水率预测模型,各模型的相关系数均大于0.973,均方根误差均小于5.06%。结果表明:番茄叶片含水率为50.5%~94.4%时,利用频率为3.98 k Hz时叶片阻抗和电容的对数函数可对番茄叶片含水率进行监测。     

基于K-means聚类算法的草莓灌溉策略研究

为进一步提高日光温室封闭式栽培下草莓灌溉水肥利用率,研究了基质含水率和温度影响下的草莓灌溉策略优化方法。采用土壤水分传感器对草莓果期基质含水率进行实时监测,通过对基质含水率随时间变化的规律分析,并结合日平均温度进行K-means聚类分析,提出一种草莓优化灌溉策略。试验结果表明,灌溉第1阶段基质含水率快速上升,在灌溉结束时达到峰值,每次灌溉基质含水率平均提高21.5个百分点;第2阶段快速下降,在20 min内基质含水率平均下降3.5个百分点;第3阶段变化趋于平稳,在30 min内基质含水率平均下降1.2个百分点。在每个灌溉周期内,含水率呈线性下降趋势,在整个果期内,其斜率随日平均温度的升高逐渐增加,由0.0114增加至0.0365。研究结果表明,根据基质含水率变化和日平均温度区间进行定量灌溉,理论上果期每株草莓仅需要4.51 L水,可节水15.4%,该方法能有效提高水肥利用率,实现节水节肥。     

快速检测禽流感病毒的生物阻抗测试仪

在生物芯片上通过测量微(纳)电极阻抗值以诊断溶液中禽流感病毒,是目前禽流感病毒快速检测的方向之一.以AD5933高精度阻抗转换芯片为核心测量芯片,以ATmega16单片机为控制器,通过外围电路设计和调试,研制激励频率范围1～100 kHz、测量阻抗范围1～1 000 kΩ的阻抗测试仪,通过液晶实时显示扫频和定点测量结果.为保证测试仪的准确性,设计了带有35组不同阻抗组合的校正网络,用以实时校正.经精度为0.2％的商品化阻抗测试仪标定,所研制的原理性装置容抗测量精度达3％,通过进一步改进后可以满足使用要求.     

An artificial capillary barrier to improve root zone conditions for horticultural crops: physical effects on water content

Capillary barriers (CBs) occur at the interface of two soil layers having distinct differences in textural and hydraulic characteristics. The objective of this study was to introduce an artificial CB, created by a layer of gravel below the root zone substrate, in order to optimize conditions for the cultivation of horticultural crops. Potential root zone formats were analyzed with and without the gravel CBs for variables including the following: depth of CB; barrier separating the root zone from the surrounding soil; and root zone soil texture. Field and simulated results revealed that artificial CBs increased root zone water content and changed water flow dynamics. Volumetric soil water content was increased by 20–70%, depending on the soil texture and depth of the barrier. Sandy soil texture and shallower placement resulted in relatively higher water content. For sandy soil without plants, a shallow (0.2 m depth) CB increased water content of the overlaying soil by 50% compared to the control. The introduction of a gravel CB below the root zone of pepper plants (Capsicum Annum L.) lead to 34% higher matric head, 50% lower diurnal fluctuations in matric head and 40% increase in pepper fruit yield. Increasing water content by way of artificial CBs appeared to improve the water use efficiency of pepper plants. Such an improvement could lead to reduced water and fertilizer application rates and subsequent reduction in contamination below the root zone. This is especially relevant for substrates of low water-holding capacity typically used in horticulture crop production.     

滴灌水肥耦合技术在西北干旱区作物栽培中的应用

水分和养分是影响作物生长发育的关键因素,明确作物需水需肥规律及其交互作用有助于农作物优质高产栽培。我国西北干旱区水资源极端匮乏,滴灌水肥耦合技术可以准确而均匀地将水肥施用于作物根部。对滴灌水肥耦合技术的优点及其对西北干旱区作物的影响研究进行了综述。滴灌水肥耦合技术通过扩大水分和养分在作物根区的运移范围,有利于作物对水分和养分的汲取和利用,实现节水省肥增产调质的目标。滴灌水肥耦合技术的优点为提高农作物水肥利用效率、促进农作物优质高产栽培、减少田间劳动力和有利于健康绿色可持续农业的发展。      

利用作物冠层叶气温差预报根系层土壤含水率的试验研究

根系是作物吸收水分的重要器官,根系的生长和分布对水分利用起着重要的作用,试验以番茄作为研究对象,于2011年的春夏两季对日光温室番茄的根系活动层内土壤容积含水率与冠层叶-气温差之间的关系进行了研究。结果表明：反映日光温室番茄的冠层叶-气温差与土壤含水率关系的最佳测定时间是13：00～15：00,根据该时段内的数据分析发现,冠层叶-气温差与不同深度范围内的土壤容积含水率成负相关,且与20～30cm土层内的土壤容积含水率相关性最为显著,相关系数为-0．808,通过回归分析,得出冠层叶-气温差（△T）与20～30cm土层内的土壤容积含水率（Sw）两者之间的回归方程为SW=-0．017AT＋0．155,因此可以确定番茄根系的活动层主要分布在土层的20～30cm范围内。     

刚柔耦合串联机械臂末端位置误差分析与补偿

机械臂连杆柔性、关节柔性等非线性变形的综合影响,导致其末端位置发生偏离而产生误差。本文以IRB1410型串联机械臂为研究对象,采用理论分析、仿真分析与实验验证相结合的方式,对机械臂末端位置误差进行分析与补偿研究。首先,建立机械臂刚柔耦合理论误差模型,并运用Newmarkβ法进行数值仿真分析;联合ANSYS和ADAMS进行刚柔耦合机械臂末端位置运动误差仿真;为了实现快速补偿,提出基于BP神经网络的伪目标点法对位置误差进行补偿,补偿后其位置误差均方根减小了68.3%,说明该方法具有较好的补偿效果;最后,自主设计并搭建了测量实验平台,采用所提算法进行了误差补偿实验,对比补偿前后距离误差,补偿后误差均方根减小了77.01%,验证了伪目标点法对柔性误差补偿的有效性。     

滴灌紫花苜蓿根层水分稳定同位素特征分析

为了明确滴灌紫花苜蓿根层水分运移,进一步阐明滴灌节水机理,采用液态水稳定氢氧同位素技术,分析了滴灌紫花苜蓿根层水分稳定氢氧同位素分布特征。结果表明,紫花苜蓿根层水分稳定氢氧同位素在下层富集,且随土壤剖面深度的增加同位素富集量有增加的趋势。滴灌条件下,紫花苜蓿根层发育有较多细根,可迅速而高效地利用灌溉水,灌溉后紫花苜蓿对灌溉水的利用不明确偏向于某一深度土层,根层内各土层土壤水均有利用。灌溉前土壤干旱时,滴灌紫花苜蓿以30 cm上下土层土壤水作为主要水分来源的概率较高。     

Effects of hysteresis on redistribution of soil moisture and deep percolation at continuous and pulse drip irrigation

The infiltration and redistribution of soil moisture under surface drip irrigation considering hysteresis were investigated in two soils (loamy sand and silt loam) of different texture. The effect of continuous versus intermittent application of 1, 2 and 4 l/h to the soils was evaluated in terms of wetting front advance patterns and deep percolation under the root zone. For this purpose, a cylindrical flow model incorporating hysteresis in the soil water retention characteristic curve, evaporation from the soil surface, and water extraction by roots was used. The results show that, compared with continuous irrigation, pulse irrigation slightly reduces the water losses under the root zone in both cases (with and without hysteresis). Also, at the total simulation time, in both types of irrigation, hysteresis reduces significantly the water losses under the root zone. Finally, the effect of hysteresis was found to be greater at higher discharge rate (4 l/h) and consequently at higher water content at the soil surface.     

不同水分条件对草坪草耗水及生长影响的研究

利用小型蒸渗仪,开展了不同土壤水分条件下,早熟禾、高羊茅、结缕草、野牛草4种草坪草的耗水规律及生长特性的试验研究。研究发现草坪草的耗水在时间上的变化为双驼峰型,第一个耗水高峰期出现在5月中旬到6月末,第二个耗水高峰期出现在7月中旬到9月中旬。各年中草坪草耗水随降雨的变化而变化。且S1处理的草坪生长量、根重均高于S2和S3处理,但S2和S3处理的草坪生长量、根系发育差异不大。草坪草累积耗水量和日平均耗水量均随控制土壤水分下限的降低而显著降低。在草坪灌溉管理中灌溉控制土壤水分下限可控制在40%~60%的田间持水量。     

Emitter discharge characteristics of vertical tube irrigation affected by various factors

To examine the working principle of vertical tube irrigation, variations in vertical tube emitter discharge and their causes were analyzed in the laboratory experiment. The effects of the pressure head, initial soil water content, and tube diameter on the emitter discharge of the vertical tube were studied. The quantitative relationship between the time and cumulative infiltration and emitter discharge of the vertical tube was obtained, and R² was more than 0.98. Emitter discharge exhibits a positive and negative correlation with the pressure head and soil water content, respectively. Tube diameter has a nonsignificant effect on the emitter discharge. Changes in the soil water content around the emitter water outlet are the main causes of emitter discharge variations. In the experiments, the range of vertical tube emitter discharge was 0.056-1.102 L/h. The emitter of vertical tube irrigation automatically adjusts the soil water content and maintains the root zone soil water content within an appropriate range, thus achieving continuous irrigation, in order to achieve the effect of water-saving.     

Model for assessing impact of salinity on soil water availability and crop yield

The salinity condition in the root zone hinders moisture extraction from soil by plants, because of osmotic potential development in soil water due to presence of salts, which ultimately, decreases transpiration of plants and thereby affects crop yield. Therefore, an effort was made in this study to quantify the impact of salinity on soil water availability to plants. The movement of salts under irrigation and evapotranspiration regimes in root zone of soil profile was studied throughout the growing season of wheat crop with adopting exponential pattern of root water uptake. A model was developed to analyze soil water balance to find out moisture deficit because of salinity. A non-linear relationship was formulated between moisture content and salt concentration for simultaneous prediction. The Crank–Nicolson method of Finite Differencing was used to solve the differential equations of soil water and solute transport. The effect of various salt concentrations on transpiration was analyzed to develop a relationship between relative evapotranspiration and relative yield. Relationships among salt concentration, matric potential, moisture deficit and actual transpiration were also established to provide better understanding about impact of salinization and to provide guidelines for obtaining better crop yields in saline soils.