Relationships Between Crop Water Stress Index and Alfalfa Yield and Evapotranspiration
Relationships Between Crop Water Stress Index and Alfalfa Yield and Evapotranspiration
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作物水分胁迫指数与苜蓿产量和蒸散量的关系
DOI：
10.13031/2013.32278
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发表时间：
1985
影响因子：
1.5
通讯作者：
T. Sammis
中科院分区：
文献类型：
--
作者：
A. S. Abdul;D. G. Lugg;T. Sammis
摘要比较了两种测定作物水分胁迫指数（CWSI）的方法，并将CWSI与实测蒸散量（E）/潜在蒸发量（Ep）比值和苜蓿（Medicago sativa L.）干草产量进行了相关性分析。第一种方法需要确定一个较低的基线，即当作物完全蒸腾时，蒸汽压差（V）与冠层减去空气温度（Tc-Ta）之间的关系，以及一个较高的基线，即当作物不蒸腾时，V与Tc-Ta之间的关系。CWSI是上基线和下基线之间的相对位置。1982年，在亚利桑那州的灌溉良好的苜蓿中，使用红外温度计以30分钟的间隔测量Tc，以确定较低的基线。从新墨西哥州拉斯克鲁塞斯附近使用线源喷洒系统灌溉的苜蓿获得的最高Tc-Ta值被认为是上基线（4 °C）。1982年，在新墨西哥州沿灌溉梯度的五个沿着地点，用红外温度计测量了22天的Tc。然后每天在梯度上的每个位置测定CWSI。蒸散量计算了三个采伐期在1982年使用的水平衡方法在梯度上的五个位置，并使用Penman方程计算Ep。在五个地点测定了三次干草产量。CWSI值与E/Ep值呈极显著正相关（r ~ 2 = 0.85），与产量呈极显著正相关（r ~ 2 = 0.79）。第二种方法使用能量平衡考虑来确定CWSI，并需要评估空气动力学阻力（ra）。三种方法被用来评估ra，这给了相当大的差异CWSI估计。当使用风廓线法评估ra时，CWSI对测得的E/Ep和产量的估计较差。在本研究中，这被认为是由于苜蓿冠层没有完全覆盖土壤造成的。然而，当使用对流传热方法评估ra时，CWSI与测量的E/Ep（r2 = 0.90）显著相关（P<0.01）。第三种方法，叶边界层方法，没有提供一个很好的CWSI估计，因为没有第二种方法。
ABSTRACT THE objectives of this study were to compare two methods of determining Crop Water Stress Index (CWSI), and to relate CWSI to the ratio of measured evapotranspiration (E) to potential evaporation (Ep) and to dry forage yield of alfalfa (Medicago sativa L.). The first method requires determination of a lower baseline, the relationship between vapor pressure deficit (V) and canopy minus air temperature (Tc - Ta) when the crop is fully transpiring, and an upper baseline, the relationship between V and Tc - Ta when the crop is non-transpiring. The CWSI is the relative position between the upper and lower baselines. An infrared thermometer was used to measure Tc at 30-min intervals throughout 7 days in 1982 in well-watered alfalfa in Arizona to determine the lower baseline. The highest value of Tc - Ta obtained from alfalfa irrigated using a line-source sprinkler system near Las Cruces, New Mexico was taken to be the upper baseline (4 °C). The infrared thermometer was used to measure Tc on 22 days in 1982 at five locations along the irrigation gradient in New Mexico. The CWSI was then determined for each day at each location on the gradient. Evapotranspiration was calculated for three cutting periods in 1982 using the water balance method at the five locations on the gradient, and Ep was calculated using the Penman equation. Dry forage yield was determined three times at the five locations. Significant relationships (P<0.01) were obtained between CWSI and measured E/Ep (r2 = 0.85), and between CWSI and yield (r2 = 0.79). The second method used energy balance considerations to determine CWSI, and required evaluation of the aerodynamic resistance (ra). Three methods were used to evaluate ra, which gave considerable differences in the CWSI estimates. When ra was evaluated using the wind profile method, CWSI gave a poor estimate of measured E/Ep and yield. This was thought to be caused by the lack of complete soil cover by the alfalfa canopy in this study. However, when ra was evaluated using the convective heat transfer method, the CWSI was significantly correlated (P<0.01) with measured E/Ep (r2 = 0.90). The third method, the leaf boundary layer method, did not provide as good a CWSI estimate as did the second method.