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首页> 外文期刊>Acta Horticulturae >The effect of variable fetch on flux-variance estimates of sensible and latent heat fluxes in a pepper screenhouse
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The effect of variable fetch on flux-variance estimates of sensible and latent heat fluxes in a pepper screenhouse

机译：可变预热对辣椒屏蔽中的明智和潜热通量的磁通方差估计的影响

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摘要

Knowledge of crop evapotranspiration (ET) is important for accurate irrigation. The area of cultivation under screens has rapidly increased in Israel and worldwide. ET data are well-documented for many crops grown in open fields, but rather scarce forcrops grown under screens or in screenhouses. Consequently, research on methods to measure and estimate ET in protected cultivation systems has increased. We have shown that the eddy covariance (EC) technique can measure whole canopy ET in screenhouses.However, it requires expensive equipment and complex data analysis; hence it is for research only. Aiming at developing a low-cost and simple method that will be available for day-to-day use by growers, we investigated here the flux-variance method (FV), which is based on high frequency measurements of air temperature near the canopy top by a miniature thermocouple. Air temperature standard deviation is calculated and following Monin-Obukhov similarity theory (MOST), the sensible heat flux is estimated. Additional measurements of net radiation and soil heat flux allow extraction of ET from energy balance closure analysis. Since air temperature can be measured near the canopy top we hypothesize that fetch requirements can be relaxed relative to those for EC and a relatively small fetch is sufficient for reliable flux measurements by FV. In the present study the FV technique was examined in a pepper crop in an insect-proof screenhouse in southern Israel. Five miniature thermocouples were installed above the canopy at various distances from screenhouse edges, providing variable fetch from 30 to 150 m, depending on external wind direction. Measurements of stem sap flow in 10 pepper plants provided data on the latent heat flux. Net radiation and soil heat flux were measured to analyze energy balance closure and an eddy covariance system above the canopy measured sensible heat flux. Sensible heat flux from FV was regressed against reference data from the EC. Results showed that the FV similarity constant, Or, varied between 3.5 and 4.4 and was independent of fetch. Coefficient of determination of the EC-FV sensible heat flux regression increased with fetch. ET extracted from FV and energy balance closure was regressed against values calculated from stemsap flow measurements. Results showed deviations of 9 to 23% between FV and sap flow based ET, with reasonable coefficients of determination, mostly above 0.56. We conclude that in the insect-proof pepper screenhouse (i) the FV technique was reliable inestimating ET and (ii) Ct was nearly independent of fetch.
机译：作物蒸散（ET）的知识对于准确灌溉是重要的。以色列和全球筛选的栽培面积迅速增加。在开放领域种植的许多作物都有良好地记录了数据，而是稀缺在屏幕或屏蔽中种植的叉孢杆菌。因此，对衡量和估算培养系统中的方法的方法的研究已经增加。我们已经表明，EDDY协方差（EC）技术可以在屏蔽中测量整个CANOPY等。但是，它需要昂贵的设备和复杂的数据分析;因此，它仅供研究。旨在开发一种低成本和简单的方法，将获得种植者的日常使用，我们在此处调查了助势 - 方差方法（FV），基于顶部附近的空气温度的高频测量通过微型热电偶。计算空气温度标准偏差，并遵循Monin-Obukhov相似性理论（大多数），估计明智的热通量。净辐射和土壤热通量的额外测量允许从能量平衡闭合分析提取等。由于空气温度可以在顶层附近测量，因此我们假设可以相对于EC的那些，并且相对小的预测可以通过FV获得相对较小的磁通测量来放松。在目前的研究中，在以色列南部的防虫屏幕中检查了Fv技术。在屏幕边缘的各个距离上安装了五个微型热电偶，从屏幕边缘的各个距离，从30到150米处提供可变的拾取，这取决于外风向。 10个辣椒植物中茎SAP流量的测量提供了关于潜热通量的数据。测量净辐射和土壤热通量，以分析能量平衡闭合和顶篷上方的涡旋协方差系统测量的可显热通量。来自FV的可显热通量从EC反对参考数据。结果表明，Fv相似性恒定，或者在3.5和4.4之间变化，而且与预取无关。 EC-FV明智热通量回归的测定系数增加。从FV和能量平衡闭合中提取的ET对由STEMSAP流量测量计算的值来回归。结果表明，Fv和SAP流动的ET之间的偏差为9至23％，具有合理的测定系数，大部分高于0.56。我们得出结论，在防虫辣椒屏幕（I）中，Fv技术可靠地估计ET和（ii）CT几乎与预取无关。

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  • 来源
    《Acta Horticulturae》 |2018年第1197期|共7页
  • 作者

    J. Tanny; O. Achiman; Y. Mazliach; V. Lukyanov; S. Cohen; Y. Cohen;

  • 作者单位

    Institute of Soil Water and Environmental Sciences Agricultural Research Organization Volcani Center POB 15159 Rishon LeZion 7528809 Israel;

    Institute of Soil Water and Environmental Sciences Agricultural Research Organization Volcani Center POB 15159 Rishon LeZion 7528809 Israel;

    Institute of Soil Water and Environmental Sciences Agricultural Research Organization Volcani Center POB 15159 Rishon LeZion 7528809 Israel;

    Institute of Soil Water and Environmental Sciences Agricultural Research Organization Volcani Center POB 15159 Rishon LeZion 7528809 Israel;

    Institute of Soil Water and Environmental Sciences Agricultural Research Organization Volcani Center POB 15159 Rishon LeZion 7528809 Israel;

    Institute of Soil Water and Environmental Sciences Agricultural Research Organization Volcani Center POB 15159 Rishon LeZion 7528809 Israel;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 园艺;
  • 关键词

    evapotranspiration; pepper; eddy covariance; sap flow; energy balance;

    机译：蒸散;胡椒;涡旋协方差;SAP流动;能量平衡;

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