冠层温度定量诊断覆膜作物水分状况试验研究

作物缺水指标CWSI（Crop Water Strese Index)和冠层－空气温差（Tc-Ta)是利用冠层温度评价作物水分状况的重要方法。1998年1999年在新乌兰乌苏农业气象站试验田内开展了对覆膜棉花和玉米的研究。结果表明：CWSI能够指示作物根系层的水分状况，而（Tc-Ta)受到环境因素（太阳辐射、空气饱和差）的较大影响。另外，对用标准化的冠层－空气温差法NDT（Normalized Difference of Temperature)定量诊断作物水分状况的可行性进行了研究。结果表明该方法在很大程度上能消除环境因素的影响，直接指标作物根系层的水分状况，并提出了覆膜棉花和玉米各生育阶段需灌溉的临界CWSI及NDT值。     

基于叶温的作物水分亏缺诊断方法研究

作物冠层或叶片温度的变化可以反映作物的水分状况[1]。为此,根据能量平衡原理分析了作物的冠层(叶片)—空气温差变化的影响因素,并采用模糊推理技术,以叶片—空气温差及相关的环境因素(空气水汽压差、光照强度、空气温湿度和风速等)为输入变量,以CWSI为输出变量,探讨基于植物叶片—空气温差的作物水分亏缺诊断的智能化方法,实现了作物水分亏缺指标的动态分析,有效地解决了环境因素对CWSI计算结果的影响。采用温室生长的黄瓜为对象进行试验,试验表明:该诊断方法可有效地反映作物水分亏缺程度,克服了传统诊断的局限性。     

冠层温度指导冬小麦灌溉的试验研究

在冬小麦主要生育期,测定了6个不同水分处理的冠层温度、气温以及土壤含水率,计算了冠气温差并分析了它们之间的相互关系。结果表明:作物水分胁迫指数CWSI和冠层-空气温差(Tc-Ta)是利用冠层温度评价作物水分状况的重要方法。冠层温度和冠气温差都有明显的日变化过程,其中冠层温度在下午14:00前后达到最大值;中午12:00~14:00时段冠气温差反应冬小麦的供水状况最具代表性;冬小麦适宜水分处理的冠气温差阈值为-1.5℃<ΔT<1.3℃。冬小麦旺盛生长期间(15/4~25/5)的水分胁迫指数平均值与最终籽粒产量的关系是一种非线性的关系,平均水分胁迫指数在0.18~0.23范围为冬小麦的最优供水标准。     

用冠层温度定量诊断作物根系活动层

冠层温度在定量诊断作物水分亏缺中得到了广泛的应用，1998年和1999年在新疆乌兰乌苏农业气象站试验田对覆膜棉花和玉米进行了研究，在此研究成果的基础上，提出了冠层温度最佳的测定时间，进行了用冠层温度定量诊断作物根系活动层的初步研究，结果表明可以利用CWSI与不同土层含水量的相关系数动态，准确地确定作物根系主要活动层的范围。     

棉花冠层温度的变化规律及其用于缺水诊断研究

作物冠层温度是反映作物水分状况的一个良好指标，在研究环境因素对冠层温度影响的基础上，分析了不同土壤水分条件下棉花冠层温度的变化规律。研究表明了冠层温度与细胞液浓度之间存在良好关系，建立的冠层温度与气温差同气象因素和土壤水分的关系可用于判断作物的缺水状况     

大田玉米水分胁迫指数经验模型建立方法

作物水分胁迫指数(Crop water stress index,CWSI)经验模型的建立与气候和种植条件密切相关。以内蒙古自治区鄂尔多斯市达拉特旗大田玉米为对象,研究了CWSI的最优经验模型。玉米在营养生长阶段(Vegetative stage,V期)、生殖期(Reproductive stage,R期)和成熟期(Maturation stage,M期)分别进行不同灌溉水平的处理,采用红外测温传感器采集玉米冠层温度。分别结合田间和实验地旁标准气象站空气温湿度数据建立了CWSI经验模型的无水分胁迫基线。基于2种无水分胁迫基线,分别利用饱和水汽压梯度获取的无蒸腾作用基线和5℃无蒸腾作用基线建立了4种CWSI经验模型,得出反映大田玉米水分胁迫状况的关系曲线,并进行对比。结果表明,基于实验地旁标准气象站空气温湿度数据建立的CWSI经验模型具有很大的波动性,并不能很好反映玉米的水分胁迫状况,其值常常超出正常范围(0~1)。而基于田间空气温湿度数据建立的CWSI经验模型则可以很好地监测内蒙古自治区大田玉米水分胁迫状况,M期3种不同水分处理100%、52%和28%具有较好的CWSI数值梯度,分别为0.03、0.14和0.32。相比于基于饱和水汽压梯度获取的无蒸腾作用基线,以5℃作为无蒸腾作用基线时得到的CWSI数值较小,可以较好地反映水分胁迫状况,对应上述M期3种不同水分处理CWSI值分别为0.02、0.10和0.22,具有较为合理的梯度。经过初步检验和分析,认为基于田间空气温湿度数据建立的CWSI经验模型较为合理,可以有效监测大田玉米水分胁迫状况。     

大田玉米水分胁迫指数CWSI基线建立方法试验研究

作物水分胁迫指数(Crop water stress index,CWSI)经验模型的建立与气候和种植条件密切相关。本文以内蒙古自治区鄂尔多斯市达拉特旗大田玉米为对象,研究CWSI的最优经验模型。玉米在营养生长阶段(Vegetative stage,V期)、生殖期(Reproductive stage,R期)和成熟期(Maturation stage,M期)分别进行不同灌溉水平的处理,采用红外测温传感器采集玉米冠层温度。分别结合田间和实验地旁标准气象站空气温湿度数据建立了CWSI经验模型的无水分胁迫基线。基于2种无水分胁迫基线,分别利用饱和水汽压梯度获取的无蒸腾作用基线和5℃无蒸腾作用基线建立了4种CWSI经验模型,得出反映大田玉米水分胁迫状况的关系曲线,并进行对比。结果表明,基于实验地旁标准气象站空气温湿度数据建立的CWSI经验模型具有很大的波动性,并不能很好反映玉米的水分胁迫状况,其值常常超出正常范围0～1。而基于田间空气温湿度数据建立的CWSI经验模型则可以很好地监测内蒙古自治区大田玉米水分胁迫状况,M期3种不同水分处理100%、52%和28%具有较好的CWSI数值梯度,分别为0.04、0.14和0.32。相比于基于饱和水汽压梯度获取的无蒸腾作用基线,以5℃作为无蒸腾作用基线时得到的CWSI数值较小,可以较好地反映水分胁迫状况,对应上述M期3种不同水分处理CWSI值分别为0.02、0.10和0.22,具有较为合理的梯度。经过初步检验和分析,认为基于田间空气温湿度数据建立的CWSI经验模型较为合理,可以有效监测大田玉米水分胁迫状况。     

基于冠层温度的温室葡萄CWSI模型试验研究

探讨并建立了适合于镇江丘陵地区温室葡萄水分状况监测的作物水分胁迫指数(CWSI)模型.通过田间实验和观测,得到了适合温室葡萄的CWSI经验模型中的经验关系.初步的检验和分析表明,这一模型是合理的,可以用于温室内葡萄基于冠层温度信息的水分状况监测.     

基于无人机热红外遥感的玉米地土壤含水率诊断方法

为使热红外遥感诊断土壤含水率更加准确、高效,以不同水分处理的大田玉米为研究对象,借助无人机可见光图像,对热红外图像进行植土分离,并提取玉米冠层温度和地表土壤温度。通过剔除温度直方图两端1%的温度像元对温度信息进行优化,进而计算作物水分胁迫指数(Crop water stress index,CWSI)、冠层相对温差(Canopy relative temperature difference,CRTD)、地表相对温差(Surface relative temperature difference,SRTD),利用三者之和求得水分-温度综合指数(Water-temperature composite index,WTCI),并用于诊断不同深度的土壤含水率。结果表明,剔除温度直方图两端1%温度像元的玉米冠层温度与实测冠层温度的相关性更高(4次试验的R2由0. 823、0. 886、0. 899、0. 876提高至0. 906、0. 938、0. 944、0. 922),剔除温度直方图前端1%温度像元的地表土壤温度与实测地表温度的相关性也更高(2次试验的R2由0. 841、0. 875提高至0. 908、0. 925),即通过直方图法优化的温度更接近实测温度;在拔节前期,CWSI、WTCI诊断0～20 cm土壤含水率效果较优,而拔节后期、抽雄吐丝期、乳熟期诊断0～40 cm土壤含水率效果较优;在半覆盖条件下,包含冠层温度信息(CWSI、CRTD)和土壤温度信息(SRTD)的WTCI1与土壤含水率的相关性更高(0～40 cm:决定系数为0. 500、0. 821,高于0. 463、0. 748);在全覆盖状态下,包含冠层相对温差(CRTD)的WTCI2与土壤含水率的相关性更高(0～40 cm:决定系数为0. 809、0. 729,高于0. 721、0. 656),表明WTCI是诊断土壤含水率效果较优的指标。     

基于无人机热红外的水分胁迫指数与土壤含水率关系研究

为了实时快速监测作物根系活动层的土壤含水率,利用低空无人机搭载的热红外相机获取经4种水分处理的棉花花铃期一天中5个时刻的冠层温度,并连续观测5 d,应用水分胁迫指数(CWSI)的理论模式、简化模式、定义模式计算得到3种CWSI,与棉花根系不同土壤深度含水率建立模型。研究表明:3种胁迫指数与土壤含水率具有幂函数关系,其中理论模式与土壤含水率的相关性最佳,定义模式次之,简化模式最差;在一天中不同监测时间点上,3种CWSI的监测精度在13∶00最高,9∶00和17∶00最差;在监测深度上,3种胁迫指数与0～60 cm处的土壤含水率关系最为紧密,0～30 cm次之,0～15 cm最差。该研究可大面积获取作物根系层土壤含水率,提高作物根系层土壤含水率的反演精度。     

膜上灌作物需水量和地膜覆盖效应试验研究

1998年和 1 999年在新疆自治区乌兰乌苏农业气象实验站内进行了膜上灌条件下的覆膜棉花和玉米的需水规律及地膜覆盖效应的试验研究。结果表明地膜覆盖具有明显的增温保墒效应 ,在苗期增温效应尤为显著 ,覆膜农田地表下 5 cm、1 0 cm、1 5 cm、2 0 cm和 2 5 cm在 8:0 0、1 4:0 0和 2 0 :0 0等 3个时刻 ,苗期平均地温比露地棉田分别高 5 .7℃、3 .3℃、3 .5℃、1 .5℃和 1 .2℃。同一灌水下限条件下 ,在整个生育期内覆膜棉花、玉米耗水较未覆膜棉花、玉米分别减少水分蒸发损失 73 .6mm和 60 .1 mm。在当地气候条件、土壤质地和作物栽培方式下覆膜棉花、玉米在全生育期内分别耗水 3 74.5 mm和 3 74.81 mm,平均耗水强度为 2 .2 6mm/d和 2 .97mm/d。     

基于WS和实际耗水量的膜下滴灌

通过田间试验，建立了膜下滴灌棉花CWSI和水汽饱和差VPD的定量关系，确定了棉花各生育阶段CWSI下基线的特定表达形式。对膜下滴灌条件下棉花生长发育、光合动态与根系分布规律以及不同水分处理的耗水量、产量与品质指标进行了观测。对不同水分处理棉花的CWSI进行了定期观测，得到了棉花CWSI与棉花耗水量的关系。     

Crop water stress index relationships with crop productivity

Summary Field experiments between 1983 and 1987 were used to study the effect of crop development on crop water stress index (CWSI) parameters and the relationship of CWSI with the yield of cotton and grain sorghum. The absolute slopes of nonstressed baselines (NSBL) generally increased until canopy cover reached 70% (Table 1). NSBL derived from data collected when canopy temperature exceeded 27.4 °C had greater absolute slopes and higher R ²-values than NSBL that included all diurnal measurements (Table 1). Average CWSI values of cotton and grain sorghum grown under varying soil water regimes were negatively correlated with yield. Grain sorghum yield was more sensitive to CWSI values than was cotton lint yield (Figs. 1 and 2). Multiyear data analysis indicated that yields from cotton that experienced a completely stressed condition during part of each day during the boll setting period would be 40% of those from completely nonstressed cotton (Fig. 3). Negative values of CWSI computed for cotton growing under non-water stressed conditions were associated with uncertainties in calculations of aerodynamic resistance (r _aand in estimating canopy resistance at potential evapotranspiration (r _cp).     

作物节水灌溉需水规律研究

基于节水灌溉条件下作物需水量试验资料,分析了控制灌溉和覆膜旱作节水灌溉的水稻需水规律以及节水高效灌溉模式下冬小麦、夏玉米和棉花作物的需水规律。结果表明,节水灌溉模式通过对水稻、冬小麦、夏玉米和棉花等作物产生的生长调控作用与补偿生长效应,使植株蒸腾量和棵间蒸发量较大幅度减少,各阶段需水量、需水强度和需水模系数均发生显著变化,形成了节水灌溉模式的主要农作物新的需水规律。可为节水灌溉制度的制定、节水型灌区动态配水及灌溉预报等提供科学依据。     

Water status response of corn and cotton to altered irrigation

Water is a primary limiting factor to crop production and thus crop water status is essential information for management decisions. Corn and cotton were grown in the field under two constant water regimes. The low water level (WL) was 0.662PET (potential evapotranspiration) in corn and rainfall for cotton. The high water level (WH) was 1.02PET for both crops. Two transient water treatments in each crop began as the two constant water level treatments but then the water inputs were reversed and the change in water status was monitored. When the transient water treatments were initiated, corn was at the V14 and V16 growth stages in the WL and WH treatments, respectively, and cotton was 2 weeks past first bloom for both water levels. The purpose of the experiment was to compare the sensitivity of leaf water potential (LWP) and crop canopy temperature to changes in irrigation rate. The transient water treatment of each crop that relieved water stress (TLH) changed from WL to WH and the treatment which induced water stress changed from WH to WL (THL). The LWP values of the transient water treatments reversed 5 and 8 days after reversing water input rates to corn in 1998 and 1999, respectively, and after 3 days in both years for cotton. A reversal in canopy temperatures, expressed as the amount of daily time that the temperature was above 28°C (DST), was not detected between the TLH and THL treatments of corn after 25 days in 1998 or after 13 days in 1999. The DST values of the cotton transient water treatments reversed after 4 days in 1998 and 5 days in 1999, when the values of THL became greater than for TLH. Corn tassels, which apparently transpire less than leaves, were forming at the beginning of the transient water treatments and their presence in the view of the infrared thermocouples may have reduced the apparent radiometric temperature difference between the transient water treatments. During the water status adjustment period following the initiation of the transient water treatments, there were significant linear relationships between LWP and DST in cotton in both years but only in 1998 in corn. Cotton canopy temperature could be used to rapidly monitor an entire field in contrast to LWP which accurately measures plant water status but cannot provide automated measurements across a large area.     

开沟覆膜滴灌条件下土壤水、温变化规律研究

新疆是中国葡萄重要的生产基地,但每年因盐碱与缺水导致减产现象严重。开沟覆膜滴灌技术结合膜下滴灌与开沟技术优点,理论上可有效改善作物生长的水土环境。为研究桁架葡萄下开沟覆膜滴灌技术对土壤水分与温度变化的影响,在石河子147团6连试验地用EM50仪器开展土壤水分、温度监测试验。研究结果表明:①在开沟模式为20 cm×100 cm,灌水定额为300 m3/hm~2时,无论是膜中还是膜边,灌水前后土壤含水量维持在0.22~0.38,满足作物根系吸水。加大灌水定额,在覆膜影响下,滴灌带表面积水区面积增大,使得在滴头下方形成饱和区增大;随着开沟深度的增大,覆膜中土壤含水量变化不明显,覆膜边呈下降趋势。②温度监测表明,无论是温度上升期(12时),还是夜间下降期(24时),土体温度变化幅度均在15~31℃,给葡萄生长提供良好的温度环境,利于葡萄产量与品质的提高。     

Evaluation of crop water stress index for LEPA irrigated corn

This study was designed to evaluate the crop water stress index (CWSI) for low-energy precision application (LEPA) irrigated corn (Zea mays L.) grown on slowly-permeable Pullman clay loam soil (fine, mixed, Torrertic Paleustoll) during the 1992 growing season at Bushland, Tex. The effects of six different irrigation levels (100%, 80%, 60%, 40%, 20%, and 0% replenishment of soil water depleted from the 1.5-m soil profile depth) on corn yields and the resulting CWSI were investigated. Irrigations were applied in 25 mm increments to maintain the soil water in the 100% treatment within 60–80% of the “plant extractable soil water” using LEPA technology, which wets alternate furrows only. The 1992 growing season was slightly wetter than normal. Thus, irrigation water use was less than normal, but the corn dry matter and grain yield were still significantly increased by irrigation. The yield, water use, and water use efficiency of fully irrigated corn were 1.246 kg/m², 786 mm, and 1.34 kg/m³, respectively. CWSI was calculated from measurements of infrared canopy temperatures, ambient air temperatures, and vapor pressure deficit values for the six irrigation levels. A “non-water-stressed baseline” equation for corn was developed using the diurnal infrared canopy temperature measurements as T _c–T _a = 1.06–2.56 VPD, where T _c was the canopy temperature (°C), Ta was the air temperature (°C) and VPD was the vapor pressure deficit (kPa). Trends in CWSI values were consistent with the soil water contents induced by the deficit irrigations. Both the dry matter and grain yields decreased with increased soil water deficit. Minimal yield reductions were observed at a threshold CWSI value of 0.33 or less for corn. The CWSI was useful for evaluating crop water stress in corn and should be a valuable tool to assist irrigation decision making together with soil water measurements and/or evapotranspiration models. Received: 19 May 1998     

Canopy temperature and water stress of cotton crops with complete and partial ground cover

Summary The use of canopy and air temperature differences to compute a crop water stress index (CWSI) for assessing plant water status was investigated using cotton crop canopies that either fully or partially covered the ground. The complete ground cover canopy condition was studied in a well watered moisture regime in a rainout shelter with measurements made on six Texas cotton race stocks. The partial ground cover canopy situation was investigated in a well watered moisture regime of a commercial cotton variety Paymaster 266 grown in the field. The slope of the nonstressed baseline of the CWSI for a cotton canopy with about 50% ground cover was approximately one-half that reported for full canopies. Values of CWSI calculated with theoretical and empirical procedures agreed more closely under a complete canopy condition than under a partial canopy situation. Values of aerodynamic resistance (r _a ) and canopy resistance for well watered soil moisture conditions (r _ep )were estimated in order to use the theoretical procedure of computing CWSI. Values of r _a ranged from 10 to 15 sm^–1 and r _cp from 50 to 60 sm^–1. Both the theoretical and empirical procedures showed much promise, but more information is needed to develop techniques for evaluating r _a and r _cp under differing canopy and environmental conditions.     

Evaluating the Crop Water Stress Index and its correlation with latent heat and CO2 fluxes over winter wheat and maize in the North China plain

Plant water status is a key factor impacting crop growth and agricultural water management. Crop water stress may alter canopy temperature, the energy balance, transpiration, photosynthesis, canopy water use efficiency, and crop yield. The objective of this study was to calculate the Crop Water Stress Index (CWSI) from canopy temperature and energy balance measurements and evaluate the utility of CWSI to quantify water stress by comparing CWSI to latent heat and carbon dioxide (CO₂) flux measurements over canopies of winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.). The experiment was conducted at the Yucheng Integrated Agricultural Experimental Station of the Chinese Academy of Sciences from 2003 to 2005. Latent heat and CO₂ fluxes (by eddy covariance), canopy and air temperature, relative humidity, net radiation, wind speed, and soil heat flux were averaged at half-hour intervals. Leaf area index and crop height were measured every 7 days. CWSI was calculated from measured canopy-air temperature differences using the Jackson method. Under high net radiation conditions (greater than 500 W m⁻²), calculated values of minimum canopy-air temperature differences were similar to previously published empirically determined non-water-stressed baselines. Valid measures of CWSI were only obtained when canopy closure minimized the influence of viewed soil on infrared canopy temperature measurements (leaf area index was greater than 2.5 m² m⁻²). Wheat and maize latent heat flux and canopy CO₂ flux generally decreased linearly with increases in CWSI when net radiation levels were greater than 300 W m⁻². The responses of latent heat flux and CO₂ flux to CWSI did not demonstrate a consistent relationship in wheat that would recommend it as a reliable water stress quantification tool. The responses of latent heat flux and CO₂ flux to CWSI were more consistent in maize, suggesting that CWSI could be useful in identifying and quantifying water stress conditions when net radiation was greater than 300 W m⁻². The results suggest that CWSI calculated by the Jackson method under varying solar radiation and wind speed conditions may be used for irrigation scheduling and agricultural water management of maize in irrigated agricultural regions, such as the North China Plain.