灌溉渠道断面测水简易快速方法

根据水力学明渠二元流流速分布规律，提出在灌溉渠道标准断面测流采用简易快速法，实地验证效果较好。这对灌区用水管理将起到一定的推进作用。     

水产饲料含水率预测模型研究

目前饲料烘干技术上最大的难点在于缺乏有效的干燥数学模型来准确预测饲料的含水率,为此,文章基于指数函数建立三种水产饲料的含水率预测数学模型,并进行试验验证.首先在循环风机频率为30 Hz,料层厚度为30 mm的条件下,对三种水产饲料进行单一温度(90℃、105℃、120℃、135℃)烘干试验,其次基于单一温度试验数据,采...     

无人机热红外反演土壤含水率的方法

以不同生育期夏玉米为对象,讨论无人机热红外反演夏玉米田土壤含水率的精度及反演方法.利用无人机获取试验区的可见光和热红外图像.通过可见光图像提取冠层掩膜并叠加在热红外图像上提取玉米冠层温度,分析冠层温度的变化趋势及与叶面积指数(LAI)的相关性.最后,利用冠气温差的相反数与叶面积指数构建了一个新指标(D_TL),讨论了冠气温差或D_TL指标反演土壤含水率的准确性.结果表明：冠层温度随着土壤含水量的增加而降低,夏玉米LAI在一定程度上可以表征冠层温度;对比4个时期的数据,发现冠气温差反演效果在灌溉后较好(如2次灌后R²分别为0.614 6和0.463 7);与冠气温差相比,D_TL指标可以提高土壤含水量反演的精度,如0～20 cm深度的R²从0.614 6和0.463 7提高到0.661 6和0.485 0.该研究对热红外反演夏玉米田间土壤含水率方法进行了新的尝试.     

不同含水率下花生荚果静摩擦系数测定

为研究含水率对花生荚果静摩擦系数的影响,以花生主产区主要种植品种宛花2号、大白沙171为试验物料,利用DGF30/7-IA型电热鼓风干燥箱对花生荚果进行含水率调控(10.18%、13.57%、16.28%、20.66%、25.85%);利用静力学原理构建的静摩擦系数斜面仪测定花生荚果的静摩擦系数;采用单因素试验,分别分析花生品种、接触材料、荚果含水率对花生荚果静摩擦系数的影响。试验结果表明在含水率各水平下不同品种花生荚果与Q235钢板、大孔筛、小孔筛的静摩擦系数变化趋势相同;花生荚果静摩擦系数随含水率的增大而增大,宛花2号在不同含水率下与Q235钢板、大孔筛、小孔筛的静摩擦系数变化范围分别为0.388~0.611、0.494~0.819、0.553~0.975,大白沙171在不同含水率下与Q235钢板、大孔筛、小孔筛的静摩擦系数变化范围分别为0.42~0.622、0.608~0.822、0.619~0.892。在含水率各水平下花生荚果与不同接触材料的静摩擦系数变化趋势相同,其中大白沙171的静摩擦系数小于宛花2号;大白沙171花生荚果的流动性较好;研究结果可为花生循环干燥设备仿真模拟参数设置及优化设计提供参考依据。     

不同含水率对油莎豆物理特性及力学特性的影响

为探究不同含水率条件下油莎豆的物理特性及力学特性,减少油莎豆在收获、干燥、清洗等过程中受到挤压摩擦而产生的机械损伤,开展5种含水率(20%,25%,30%,35%,40%)水平下油莎豆的主要物理特性及力学特性试验。试验结果表明,含水率在20%～40%范围内,随着含水率的升高,油莎豆平均几何粒径显著增加;滚动摩擦系数呈线性增加;而最大破碎力呈先增大后减小趋势,在含水率为30%时达到最大值210.169 N。根据试验结果,分别拟合得到油莎豆压缩特性、摩擦特性、休止角与含水率的关系方程,为油莎豆播种、收获、干燥、清洗等装备设计及参数优化提供技术依据。     

The effect of a tile drain on the soil moisture content of peat

Several neutron access sites were installed in a line at right angles to, and on either side of, a tile drain across a slope within a grassland improvement area. The effect of the drain on the moisture content of peat was determined and found to be negligible at distances greater than 1 m from the drain.     

初始含水率对斥水黏壤土入渗特性的影响

为了探究初始含水率对斥水土壤入渗过程的影响规律,通过室内二维土箱的滴灌模拟试验,设置6个初始含水率水平(4.78%,7.28%,9.97%,13.64%,16.07%,19.02%),研究了初始含水率对湿润锋运移距离、宽深比、累积入渗量、入渗速率和土壤水分分布的影响,并评价了不同入渗模型的适用性.结果表明:随着初始含水率的提高,湿润锋运移相同深度所需时间呈逐渐减小趋势,两者较好满足幂函数关系,湿润锋宽深比逐渐减小;累积入渗量变化趋势为先减小后增大;入渗速率整体趋势为逐渐减小,其中斥水程度峰值含水率附近的处理出现入渗速率短暂提高的现象;Kostiakov模型能够较好反映斥水黏壤土的入渗规律,且斥水程度越大,模型拟合精度越低;随着斥水程度增加,土壤水分逐渐向湿润体垂向中间区域集中,并出现过度饱和现象.该研究可为斥水土壤的入渗理论奠定一定的基础.     

风障对茶园的减风增温效果及对茶树冠层叶片含水率影响

为解决冬季茶园风寒冻害问题，于2008年1月在安徽农业大学茶场建立塑料薄膜风障，测定风障对茶园的减风增温作用及其对茶树冠层叶片含水率的影响。风障的高度为2.0 m，以5×7网格点测定2.8、2.0 m风障高和1.2 m茶树冠层高度3个层次的风速，以4×4网格点测定地表温度、茶树冠层叶片含水率。结果表明，2.8 m高度，风障上方的风速比环境风速增加30%左右，下风方向的减风作用随风速增大而减小，距离风障7 m区域是风速减弱最强的区域，环境风速2.6 m/s时中轴线风速减小13.5%，环境风速1.0 m/s时     

Relationships between crop temperature,grain yield,evapotranspiration and phenological development in two hybrids of moisture stressed sorghum

Summary Recent studies have shown that the grain yields of corn (Zea mays L.) and wheat (Triticum aestivum L.) are related to the degree of water stress they undergo. The purpose of the study reported here was to establish relationships between crop temperature and the grain yields, phenological development, evapotranspiration rates (ET) and leaf water potential ( _l ) of two hybrids of grain sorghum (Sorghum bicolor L. Moench) subjected to varying levels of plant water stress. The study was conducted at the University of Nebraska Sandhills Agricultural Laboratory in 1978 on a Typic Ustipsamment (Valentine fine sand) soil. The sorghum hybrids used were RS 626 and NB 505. Four irrigation treatments were applied in order to subject the crops to varying levels of water stress during each of three major growth stages. Soil moisture was monitored with a neutron probe. ET was estimated with the water balance technique. Crop temperature was measured with an IR thermometer and leaf water potential was measured with a Scholander pressure bomb. Grain yields were reduced by water stress occuring at anytime during the growing season. Yield reductions were largest when stress occurred during only the grainfill period and were least when stress occurred during the entire growing season. The percentage reduction in sorghum grain yield can be described by an index involving the seasonal accumulation of the daily mid-day temperature differences between well-watered and stressed crops ( TSD). As TSD values increased, ET decreased. However, the correlation of ET with TSD was relatively low (R² = 0.60) probably due to the limited amount of data available for analysis and inaccuracies in the soil water balance method used to estimate ET. The mid-day temperature of well-watered rows ranged between 18.0 and 32.8 °C with a mid-day temperature range of about 0.5 °C between the well-watered rows in various plots for several days following an irrigation. However, in certain instances, the mid-day temperature range increased to 1–2 °C for a few days before irrigation. This suggests that certain of the rows experienced water stress and should have been irrigated earlier. Yield data support that conclusion. Range in crop temperature within a field appeared to be a sensitive indicator of crop water stress in sorghum. No significant difference in the phenological development of sorghum resulted from water stress except in one NB 505 plot in which plants were stressed throughout the entire season. In that plot, the stressed plants lagged in development behind non-stressed plants by approximately ten days. The differences in mid-day leaf water potentials ( _l ) and crop temperatures (T) between stressed and non-stressed vegetation were examined. As T increased up to about 4 °C, _l , also increased. Beyond that point, _l decreased while T continued to increase. This behavior was attributed to stomatal closure which permitted an increase in _l of the stressed plants (hence reducing _l ) even as T continued to increase.Published as Paper No. 6551, Journal Series, Nebraska Agricultural Experiment Station. The work reported was conducted under Regional Research Project 11–33 and Nebraska Agricultural Experiment Station Project 11–50. The work upon which this publication is based was supported in part by funds provided by the Office of Water Research and Technology B-044-NEB, US Department of the Interior, Washington, DC, as authorized by the Water Research and Development Act of 1978. This article was sponsored in part by the Nebraska Water Resources Center, Institute of Agriculture and Natural Resources, University of Nebraska-LincolnResearch Assistant, Associate Professor, Research Assistant, and Associate Professor, University of Nebraska, Lincoln. Contents of this puplication do not necessarily reflect the views and policies of the Office of Water Research and Technology, US Dept. of the Interior, nor does mention of trade names or commercial products constitute their endorsement or recommendation for use by the United States Government     

Infiltration of melting saline ice water in soil columns: Consequences on soil moisture and salt content

A soil column experiment was conducted to study the water and salt redistribution in a coastal saline soil under infiltration of saline ice meltwater. Four salinity levels (0, 5000, 10,000, and 15,000 mg l⁻¹ diluted seawater) and three volumes (1800, 2700, and 3600 ml) of source water were used. The results indicated that the soil water content increased with the volume of applied ice. In the top soil layers, water content was higher under salt-free ice treatment than under saline ice treatments. In the deeper soil layers, however, the saline ice treatments showed higher water content than the salt-free ice treatment. While infiltration of meltwater reduced the salt content of the surface layer of all the treatments, the desalting depths of the saline ice treatments were greater than the desalting depth of the salt-free ice treatment. The results demonstrated that in the monsoon regions, saline soils could be improved through infiltration with meltwater of saline ice.     

Dielectric coated water content reflectometer for improved monitoring of near surface soil moisture in heavily fertilized paddy field

Mat rush (Juncus effusus L.), used for ‘Tatami’ (a traditional Japanese mat), is a type of crop requiring a large amount of fertilizer (450–600 kg ha⁻¹ of N). In a heavily fertilized mat rush paddy field we examined the monitoring of soil water content (θ) by using the water content reflectometer (WCR). WCR sensors with and without coating rods were prepared and tested for their performance in different solutions. In addition, these sensors for Gley Lowland Soils were also calibrated for measuring θ. The results showed that the measured water content using the uncoated WCR, increasing with the EC of the solution, was 1.6 times of that for distilled water while the output for the coated WCR became 1.04 times. The coating prevents conduction losses while it influences the sensitivity of the WCR sensor. The monitoring of θ using both coated and uncoated WCR sensors in a mat rush paddy field was conducted throughout a cropping season. For the coated sensors, water content could be determined accurately even after fertilizer applications, while with the uncoated sensors it was overestimated. Thus, it was concluded that the use of insulated WCR sensors make it possible to accurately monitor the near surface soil moisture in a heavily fertilized paddy field.     

基于IPSO-BP模型的粮食产量预测方法研究

针对粮食产量预测的复杂性,以基本微粒群算法(PSO)为基础,引入繁殖和变异机制,提出一种改进的微粒群算法(IPSO)优化BP神经网络的连接权值和阈值.综合考虑影响粮食产量的有关因素,构建出IPSO-BP的粮食产量预测模型,并以江苏省1978-2018年的粮食产量及影响其产量的10个因素作为数据集进行仿真试验.试验结果表...     

基于高光谱技术的采摘期烟叶水分含量研究

烟叶含水量的快速检测在烟草种植业中起着关键的作用,检测采摘期烟叶水分含量,对烟草工艺具有重要意义.为了快速、无损地检测采摘期烟叶水分含量,提出一种主成分分析(PCA)结合马氏距离算法(MD)的方法来剔除异常样本,再使用偏最小二乘法(PLS)估测采摘期烟叶水分含量.首先,利用GaiaSky-mini2机载高光谱成像仪获取...     

基于水分胁迫系数的枣树园土壤含水率估算

为了实现黄土高原地区滴灌条件下枣树园土壤含水率的小范围快捷监测,根据FAO-56水分胁迫系数的定义和相关计算公式,得到了基于土壤水分胁迫系数的黄土高原地区滴灌条件下枣树根层土壤平均含水率估算公式．2009年4-9月将该公式应用于西北农林科技大学陕西米脂孟岔试验站的枣树试验园,配置了3种不同的土壤含水率控制下限,对枣树2个重要生育期的土壤含水率进行了估算,模拟了水分动态变化过程,并对估算值和实测值进行对比和误差分析．结果表明:采用基于FAO-56水分胁迫系数的计算公式对土壤含水率的动态模拟达到了较高的精度,估算值与实测值之间误差较小:其中开花坐果期各处理(灌水下限为60％,50％,40％的田间持水率)的估算值与实测值之间的相关系数分别为0828 0,0907 3,0935 1;标准误差分别为0055,0093,0068．果实膨大期各处理的相关系数分别为0777 2,0766 7,0905 5;标准误差分别为0057,0092,0079．估算值与实测值之间的相关系数随土壤含水率的增大而减小,随土壤水分胁迫程度的增大而增大,即土壤含水率较高时对公式精度有一定的影响．该方法较适用于黄土高原半干旱地区,对农业用水管理具有一定参考价值．     

Distribution of rainfall and soil moisture content in the soil profile under citrus tree canopy and at the dripline

The plant canopy intercepts rain and thus can alter the distribution of water under the canopy as compared to that along the dripline. The effects of a citrus (Citrus sinensis L. Osbeck) tree (25-year-old, Valencia orange) canopy on the distribution of rainfall and soil moisture content within the soil profile either along the dripline (D) or under the canopy near the trunk (inner side; I), and midway between I and Dripline (M) were evaluated, on the east and west sides of trees planted along north-south rows. Results of eleven storm events in 1995 (mean of east and west sides) revealed that the amounts of precipitation at the D, M, and I positions were 97–140, 47–94, and 52–79% of the incident rainfall, respectively. Thus, canopy interception of incident rainfall was quite appreciable. The soil moisture content was greater along the dripline compared to that at the M and I positions, particularly in the deeper (≥60 cm) soil profile. The water flux was significantly greater at the dripline than under the canopy indicating a greater leaching potential of soil-applied fertilizers and other chemicals when placed along the dripline. A substantial reduction in the rainfall and water flux under the canopy as a result of canopy interception suggests that application of fertilizer and chemicals under the canopy could minimize leaching losses. Received: 10 November 1997     

冻融过程对FDR测量土壤体积含水量的影响

为研究冻融过程对FDR测量土壤体积含水量的影响,采用基于FDR技术的土壤水分传感器TDR-3,通过室内温度实验箱控制环境温度范围为-20～20 ℃,对冻融过程中黏性土样体积含水量进行了测试分析．结果表明:采用FDR测量黏性土样体积含水量,在土样未进行冻融前,温度在0 ℃以上时,FDR的测量值随温度呈线性变化,随着温度的升高而增大,随着温度的降低而减小;黏性土样冻融过程中,在冻结过程中,FDR的测量值随着温度的降低逐渐减小;在融化过程中,随着温度的升高,FDR的测量值逐渐增大;相同温度条件下,黏性土冻结过程中FDR的测量值明显大于黏性土融化过程中FDR的测量值,0℃时两者差值最大,该差值受土壤初始体积含水量和冻融温度的影响．研究成果对于提高FDR测量冻融过程中土壤体积含水量的可靠性具有重要意义．     

闪烁瓶法测氡仪的高压电源电路设计

文章介绍的是闪烁瓶法测氡仪的高压电源电路的设计,由于该仪器的工作要求,需要产生-820V的负高压,为了保证系统的稳定性,避免各路工作电源的相互干扰,特选用DC-DC转换器MC34063芯片专门为高压产生电路设计一个升压转换电路,单独一路输出为高压产生电路供电。高压产生电路由脉冲变压器、振荡器、开关管所组成的间歇振荡器将反冲电压升压,升压后再经过四倍压整流滤波电路进行倍压、整流、滤波,从而获得上千伏的直流负高压。实验及应用结果表明该电路具有良好的性能和很高的应用价值。     

植物声频控制技术推广初报

张家港市农业机械技术推广站承担了由市科技局下达的“植物声频控制技术的推广试验”科技项目,并经市政府列为“2002年度市农业重点项目”之一。于2002年11月着手工作,目前已取得了初步成效。