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1.
Using the Shuttleworth and Wallace (S–W) model, evapotranspiration (ET); transpiration ratio (T/ET), which is the ratio of transpiration (T) to ET; and water-use efficiency (WUE) were estimated for a sparsely planted sorghum canopy that was well irrigated. That model is designed to estimate separately the evaporation from soil and transpiration from crops.The evapotranspiration estimates for both short- and long-term measurement periods coincided closely with the Bowen ratio energy balance (BREB) measurements. The transpiration ratios were affected by the canopy resistances and the soil surface resistances during the day. The regression curve between leaf area index (LAI) and transpiration ratio suggests that LAI, less than 1.6, determined the transpiration ratio in the absence of water stresses by soil water drought and extreme weather condition. The WUEs for transpiration (WUEt) and evapotranspiration (WUEet), which are the total dry matter (TDM) production for 1 kg T and ET, reached the peaks of 9.0 and 4.5 g kg−1 H2O, respectively, in the end of July when the total dry matter increasing rate was greatest. These two WUEs degraded to less than zero in the end of August when the plant biomass decreased due to drying and death. The WUEs are largely affected by the TDM seasonal increment rate.Thus, in a sparse crop, the crop growth properties (i.e. LAI and TDM increment) mainly determine the crop water uses (i.e. the transpiration ratio and water-use efficiency) in the absence of water stresses.  相似文献   

2.
为研究关中冬小麦植株蒸腾和土壤蒸发规律,利用2 a冬小麦小区控水试验实测数据,率定和验证了双作物系数SIMDual_Kc模型在关中地区的适用性.用大型称重式蒸渗仪的实测蒸散量值(或水量平衡法计算值)与模型模拟值进行对比.结果表明:SIMDualKc模型可较准确地模拟关中不同水分条件下冬小麦蒸散量,且模拟精度较高.模型估算的平均绝对误差为0.643 3 mm/d.模型估算的冬小麦初期、中期和后期的基础作物系数分别为0.35,1.30,0.20.另外,模型还可以较准确地估算不同水分供应条件下的土壤水分胁迫系数、土壤蒸发量和植株蒸散量.冬小麦整个生育期,土壤蒸发主要发生在作物生育前期,中期较低,后期略微增大;植株蒸腾主要发生在作物快速生长期和生长中期,整个生育期中呈先增大后减小的趋势.  相似文献   

3.
基于遥感技术估算作物蒸散发(Evapotranspiration,ET)对农业用水效率评价和精量灌溉决策具有重要意义。结合Sentinel-2数据和农田连续地面观测资料,利用混合双源蒸散发模型(Hybrid dual-source scheme and trapezoid framework-based evapotranspiration model,HTEM)对宁夏回族自治区中卫市2019年两个试验田玉米主要生育期(5—8月)的蒸散发量进行估算,并用水量平衡法对遥感估算结果进行验证和评价。结果表明:Sentinel-2数据具有高时空分辨率,能够与研究区复杂的种植地块相匹配,减少了混合像元的数量;遥感反演参数与地面观测数据拟合度较高,研究区2019年遥感反演的玉米田净辐射量均方根误差为36.256 W/m2。利用HTEM模型估算可得,主要生育期内研究区两个玉米试验田的日均实际蒸散发量分别为4.269 mm/d和4.339 mm/d,实际蒸散发总量分别为525.114 mm和533.690 mm,其中植被蒸腾量分别为363.483 mm和358.196 mm,生育初期主要以土壤蒸发形式消耗水分,随着作物的生长,在生育中后期主要以植被蒸腾的形式消耗水分。ET遥感反演结果与水量平衡结果之间差别不显著,两个观测点绝对误差分别为13.533 mm和7.774 mm。因此,结合地面连续观测系统和Sentinel-2数据估算研究区玉米生育阶段蒸散发量具有较高的精度,可为作物耗水规律研究及区域农业水管理提供技术支撑。  相似文献   

4.
Experiments were undertaken at CCS Haryana Agricultural University Farm, Sirsa (India) to estimate the optimum irrigation schedule for cotton resulting in minimum percolation losses. The sprinkler line source technique was adopted for creating various irrigation regimes at different crop growth stages. The SWASALT (Simulation of Water And SALT) model after calibration and validation provided water balance components. The wa-ter management response indicators (WMRI's) such as transpiration efficiency Et/(Irr + P), relative transpiration Et/Etp, evapotranspiration efficiency ET/(Irr + P), soil moisture storage change ΔW/Wint (deficit/excess) and percolation loss Perc/(Irr. + P) were evaluated using water balance components as estimated by the simulation study. Under limited water supply conditions, the optimum irrigation depth was found to be 57 mm at crop growth stages with pre-sowing and 1st irrigation of 120 mm and 80 mm respectively for sandy clay loam underlain by sandy loam soil (Type I). The corresponding values of relative transpiration, transpiration efficiency and evapotranspiration efficiency were 0.65, 0.65 and 0.89 respectively. The crop yield varied linearly with increasing irrigation depth which was evident from increase in relative transpiration with increasing depth of water application. However, increased depth of irrigation resulted in less moisture utilisation from soil storage (20% depletion at 40 mm depth and 4.4% moisture built up at 100 mm depth). The extended simulation study for sandy soil underlain by loamy sand (Type II) indicated that two pre-sowing irrigations each 40 mm and subsequent irrigations of 40 mm at an interval of 20 days depending upon rainfall were optimum. This irrigation scenario resulted in zero percolation loss accompanied by 74% relative transpiration and 14 per cent soil moisture depletion. Received: 20 November 1995  相似文献   

5.
西北地区冬小麦腾发量估算模型适用性评价   总被引：1，自引：0，他引：1  
为实现对西北地区冬小麦腾发量(ET)的准确估算,在对不同生育期ET的影响因子进行分析后分别采用双作物系数模型、单作物系数模型和Priestley-Taylor(PT)模型模拟ET,并以大型蒸渗仪实测ET为标准值对比其精度.结果表明:气象因子是播种-返青(Ⅰ期)和抽穗-乳熟(Ⅲ期)ET的主导因子,作物因子是乳熟-收获(Ⅳ期)ET的主导因子,2种因子对返青-抽穗(Ⅱ期)和全生育期ET的驱动作用相近;Ⅰ期双作物系数模型、单作物系数模型和PT模型的R2分别为0.511 8,0.239 3,0.374 2,RMSE变化范围为0.284 6~0.366 3 mm/d,总体评价指标GPI排名分别为1,3,2;Ⅱ期3个模型的R2均在0.700 0 以上,RMSE为0.540 9~0.844 0 mm/d,双作物系数模型模拟效果最好;Ⅲ期各模型的R2均高于0.600 0,RMSE为0.828 8~1.258 7 mm/d,双作物系数模型GPI排名第1;Ⅳ期3个模型的R2分别为0.799 1,0.671 6,0.270 8,RMSE为0.968 1~1.946 2 mm/d,作物系数模型模拟精度明显高于PT模型;全生育期各模型RMSE为0.551 5~0.893 6 mm/d,双作物系数模型的R2达到0.902 2.  相似文献   

6.
Grapevines are extensively grown in the arid region of China, but little information is available on the diurnal, seasonal and interannual variability of vineyard evapotranspiration (ET). To address this question, two vineyards in the arid region of northwest China were taken as an example to study the variation of ET using Bowen ratio-energy balance method in 2005-2008. Results indicate that the Bowen ratio method provided accurate estimate of vineyard ET as the instrument was correctly installed. Irrigation and rainfall increased daily ET by 38 and 175%, respectively, but frost decreased it by 32%. Daily ET had a maximum value of 1.6-3.5 mm/d at the berry development stage, and a minimum value of 0.8-1.7 mm/d at the early and later stages. The total ET was 226-399 mm over the growing season. The ratio of transpiration to evapotranspiration was 0.52 and the modified crop coefficient (Kcm) was 0.71-0.88 (except 2005) over the whole growing stage. Larger interannual difference of ET and Kcm mainly resulted from the difference of irrigation and rainfall between different years.  相似文献   

7.
The purpose of this study was to determine the water requirement of rice (Oryza sativa L.) in the areas of the Office du Niger (Niono, Republic du Mali, West Africa). Average annual rainfall is 600 mm and evapotranspiration exceeds precipitation in every month except August. Alluvial soils vary in texture from heavy clay to sandy loam and have very low infiltration rates. The water use of rice was measured by establishing the water balance of four irrigation units varying in size from 12 to 26 ha. Evapotranspiration was evaluated with ‘non-weighing’ lysimeters and varied in 1980 from 5.3 mm/day shortly after flooding and 7.1 mm/day during heading to 4.1 mm/day at ripening. The crop coefficients found in this study do not always correspond to those presented by Doorenbos and Pruitt (1977). The crop coefficient depended strongly on the soil cover and was 1.0 for 10–70% soil cover and increased linearly to 1.25 for 100% soil cover. This relationship between soil cover and crop coefficient can be used to improve the estimates of rice evapotranspiration from large irrigation units with incomplete soil cover. The peak evapotranspiration may be as high as 7.8 mm/day during a 10-day period under full soil cover. The peak water requirement during the period of dry land preparation does not exceed 6 mm/day on level fields. The amount of water needed to saturate the soil profile after the dry season varied from 122 to 302 mm. A significant difference was measured between the pre-irrigation gift on a level field (175 mm) and on a non-level field (255 mm), which indicates the importance of levelling.  相似文献   

8.
【目的】蒸发蒸腾量(ET)是农业生产的主要参数,ET的准确估算对农田精准用水管理和区域水资源优化配置具有重要意义。【方法】利用2012—2013年夏玉米作物指数与气象因子,采用基于参考作物蒸发蒸腾量(ET0)经验模型(Schendel、Hargreaves-M4(H-M4))的单作物系数法、单源模型(Priestley-Taylor(P-T))和双源模型(Shuttleworth-Wallace、Two-Patch)对作物蒸发蒸腾量进行模拟,并对比分析各估算模型模拟情况。【结果】基于不同生育期实测和平衡蒸发蒸腾量均值的比值修正P-T模型经验系数?,P-T修正模型对夏玉米全生育期ET模拟值与大型称质量式蒸渗仪实测值拟合的平均绝对误差(MAE)、决定系数(R2)、平均相对误差(MRE)、相对均方根误差(Relative root mean-squared error,RRMSE)和整体评价指标(GPI)排名分别为0.977 5 mm/d、0.5689、0.843 4、0.450 4和1,苗期分别为0.959 2 mm/d、0.332 0、0.478 4、0.481 1和3,拔节抽雄期分别为1.038 8 mm/d、0.507 8、0.551 7、0.429 0和1,成熟期分别为0.548 1 mm/d、0.774 6、0.915 8、0.423 9、0.692 1和1;H-M4模型对灌浆期ET模拟MAE、R2、MRE、RRMSE和GPI排名分别为1.344 3 mm/d、0.727 9、2.298 3、0.491 0和1。模拟结果均达到极显著(P<0.01,P代表显著性水平)。【结论】P-T和基于单作物系数法的H-M4均具有输入较少参数获取较精确ET估算值的优势,因此P-T可作为全生育期及苗期、拔节抽雄期和成熟期蒸发蒸腾量最优模拟模型,H-M4可作为灌浆期蒸发蒸腾量最优模拟模型。  相似文献   

9.
运用茆智提出的ET0预测方法,并结合其他学者对方法的改进,利用日常的天气预报信息,分别对豫北地区的冬小麦和夏玉米生育期内的ET0进行了预测。结果表明,在冬小麦生育期的ET0预测值,返青前绝对误差不超过0.8mm/d,返青以后93%的预测结果相对误差小于20%,53%的预测结果小于10%;在夏玉米生育时期内的预测值,95...  相似文献   

10.
基于气温预报和HS公式的不同生育期参考作物腾发量预报   总被引：2，自引：0，他引：2  
根据南京站2001-2011年实测气象数据,以Penman-Monteith(PM)公式计算得到的参考作物腾发量ET0值作为基准值,对仅需要气温数据计算参考作物腾发量的Hargreaves-Samani(HS)公式进行参数率定,采用率定后的HS公式依据2012年6月-2015年6月气温预报数据对南京水稻、冬小麦不同生育期未来1~7d的ET0进行预报,并与基于实测气象数据的PM法计算的ET0值进行比较,评价HS法的ET0预报精度。结果表明:最低、最高气温实测值与预报值相关系数分别为0.97和0.93,最低气温预报精度略高于最高气温;预见期1~7d内,水稻、冬小麦不同生育期ET0预报值与PM法计算值变化趋势基本一致,整个生育期内冬小麦ET0预报值与PM法计算值吻合程度更好,水稻、冬小麦相关系数分别达0.60、0.80左右;水稻各生育期平均准确率为66.0%~97.5%,平均绝对误差为0.65~1.22mm/d,均方根误差为0.76~1.42mm/d,冬小麦各生育期平均准确率为75.4%~99.5%,平均绝对误差为0.33~1.06mm/d,均方根误差为0.43~1.23mm/d;作物生育期各阶段对气温预报误差越敏感,ET0预报精度越低,随着生育期的推进,水稻对气温预报误差的敏感程度逐渐减小,相应的ET0预报精度逐渐增加,而冬小麦反之;但整体上预见期1~7d的气温预报及ET0预报精度达到可利用程度,可为快速灌溉预报及灌溉决策提供数据支撑。  相似文献   

11.
The dual crop coefficient approach accounts separately for plant transpiration and soil evaporation by using the basal crop coefficient and the evaporation coefficient, respectively. The SIMDualKc model, which performs the soil water balance simulation with estimation of the actual crop evapotranspiration (ET) with the dual crop coefficient approach, was applied to a drip-irrigated peach orchard under Mediterranean conditions. Orchard ET was obtained with the eddy covariance technique, which was subsequently correlated with tree transpiration estimated from sap flow measurements and soil evaporation determined with microlysimeters, thus providing ET for the whole irrigation season. Two years of field observations were used for model calibration and validation using those ET measurements and taking into account the fraction of ground covered by trees through a density factor which adjusts the basal crop coefficient. Model fitting relative to ET observations during calibration and validation provided indices of agreement averaging 0.90, coefficients of regression close to 1.0, root mean square errors around 0.41 mm and average absolute errors of 0.32 mm. Model fitting relative to transpiration and to soil evaporation produced similar results, so showing the adequateness of modelling.  相似文献   

12.
Evapotranspiration of orange trees in greenhouse lysimeters   总被引：3，自引：0，他引：3  
Eight-year-old Murcott orange trees (Citrus sinensis (L.) Murcott) grown in greenhouse lysimeters filled with sandy soil were used to investigate seasonal variations in daily and hourly evapotranspiration. The study was conducted in Japan during the summer of 2000 and the winter of 2001. Weighing lysimeters of 1.5 m diameter and 1.6 m depth (three replications) planted with a tree were irrigated when average soil moisture in 0-120 cm of soil depth was depleted to below 70% of the field capacity (FC). Evapotranspiration (ET) showed significant seasonal variations. Average ET rate exceeded 4.4 mm/day in the summer period, and dropped to 0.6 mm/day in the winter months. The average seasonal crop coefficient (KC) was 0.91 and 0.75 during the summer and winter periods, respectively. Hourly variations in ET exhibited a time difference with season. The time of maximum ET was 0900 hours for winter and 1200 hours for summer. Moreover, some evaporative losses of soil water occurred even during the night in both summer and winter seasons. Soil evaporation (E) was 33% of ET during the winter period, while E was only 11% of ET during summer. Maximum water uptake by the trees was found at a depth of 30-60 cm, and soil water depletion was observed in the 0-120 cm depth of the profile during the summer period. However, during the winter season, water depletion occurred only from 0-30 cm depth of the soil profile.  相似文献   

13.
Crop consumptive water use and productivity are key elements to understand basin water management performance. This article presents a simplified approach to map rice (Oryza sativa L.) water consumption, yield, and water productivity (WP) in the Indo-Gangetic Basin (IGB) by combining remotely sensed imagery, national census and meteorological data. The statistical rice cropped area and production data were synthesized to calculate district-level land productivity, which is then further extrapolated to pixel-level values using MODIS NDVI product based on a crop dominance map. The water consumption by actual evapotranspiration is estimated with Simplified Surface Energy Balance (SSEB) model taking meteorological data and MODIS land surface temperature products as inputs. WP maps are then generated by dividing the rice productivity map with the seasonal actual evapotranspiration (ET) map. The average rice yields for Pakistan, India, Nepal and Bangladesh in the basin are 2.60, 2.53, 3.54 and 2.75 tons/ha, respectively. The average rice ET is 416 mm, accounting for only 68.2% of potential ET. The average WP of rice is 0.74 kg/m3. The WP generally varies with the trends of yield variation. A comparative analysis of ET, yield, rainfall and WP maps indicates greater scope for improvement of the downstream areas of the Ganges basin. The method proposed is simple, with satisfactory accuracy, and can be easily applied elsewhere.  相似文献   

14.
以2009年内蒙古河套灌区春小麦套种玉米田间实测资料为基础,分别应用水量平衡原理与作物系数法得到套种作物生育各生育阶段实际腾发量;然后以作物-水模型为基本原理,采用多元线性回归方法对套种作物不同生育阶段水分敏感指标进行求解,其变化规律为：拔节-抽穗＞分蘖-拔节＞喇叭口-灌浆(玉米)＞抽穗-灌浆(小麦)＞苗期-分蘖,最后应用基于实数编码的遗传算法对小麦套玉米作物灌溉制度进行优化,结果表明,作物生育期内适宜的灌水量为450mm。  相似文献   

15.
风沙区参考作物需水量的计算   总被引：4，自引：0，他引：4  
根据国内外相关的研究成果 ,分析选择并确定了适宜于风沙区参考作物需水量 (ET0 )的计算模式。利用典型风沙区的气象资料 ,对多年逐旬参考作物需水量及 2 0 0 1年春小麦与春玉米生育时段内逐日参考作物需水量进行了分析计算。结果表明 ,FAO最新修正的 Penman-Moteith公式可较好地用于风沙区参考作物需水量的估算 ,一般 ET0 值在年内与年际间变化较大 ,最高值发生在 6月上旬左右 ,多年平均为 5 .82 mm/ d,最低值发生在 1月上旬 ,多年平均 0 .43 mm/ d左右 ,年内各日 ET0 值受气象因素的影响变幅很大 ,因此 ,精确灌溉应设法提高短期天气预报和灌溉预报的精度  相似文献   

16.
This paper presents the findings of the effect of some selected deficit irrigation scheduling practices on irrigated maize crop in a sub-catchment in south western part of Tanzania. Field experiments, in which maize (TMV1-ST) variety was planted under total irrigation, were conducted during the dry seasons of 2004 and 2005. Surface irrigation method was used and the crop was planted in basins. The seasonal water applied ranged from 400 to 750 mm. Soil moisture content from both cropped and bare soils, leaf area index, dry matter, and grain yields were measured. The dry matter yield ranged between 6,966 and 12,672 kg/ha, and grain yields obtained were between 1,625 and 4,349 kg/ha. The results showed that deficit irrigation at any crop growth stage of the maize crop led to decrease in dry matter and grain yields, seasonal evapotranspiration and deep percolation. Deficit irrigation in any one growth stage of the maize crop only seems to affect grain production and no significant effect on biomass production, but deficit irrigation that spanned across two or more growth stages affect both biomass and grain production drastically. Crop water use efficiency (WUE) and Irrigation water use efficiency (IWUE) were strongly influenced by the number of growth stages in which deficit irrigations were applied and how critical the growth stages were to moisture stress rather than the amount of irrigation water applied. While maximum WUE was obtained under full irrigation, maximum IWUE was obtained in the deficit irrigation treatment at vegetative growth stage, which suggest that IWUE may be improved upon by practicing deficit irrigation at the vegetative growth stage of the maize crop.  相似文献   

17.
冬小麦、春玉米间作条件下作物需水规律   总被引：2，自引：0，他引：2  
通过田间试验研究了冬小麦、春玉米间作条件下各生育期的作物需水规律.结果表明:与单作相比,第1个试验期内冬小麦全生育期内间作麦田土壤蒸发量增加34.63 mm,作物蒸腾量减小65.81 mm, 蒸发蒸腾量减小31.18 mm.第2个试验期内冬小麦生育期内间作麦田土壤蒸发量增加26.00 mm,作物蒸腾量减小64.81 mm, 蒸发蒸腾量减小40.81 mm.与单作春玉米相比,间作春玉米的土壤蒸发减少了40.94 mm,作物蒸腾增加了147.73 mm,ET值增加了106.79 mm.可为间作种植的水分管理提供参考.  相似文献   

18.
Pecan is a major crop in the lower Rio Grande Valley (LRGV), New Mexico. Currently, about 11,000 ha of pecan orchards at various stages of growth are consuming about 40% of irrigation water in the area. Pecan evapotranspiration (ET) varies with age, canopy cover, soil type and method of water management. There is a need for better quantification of pecan ET for the purpose of water rights adjudication, watershed management and agronomical practices. This paper describes a process where remote sensing information from Landsat-5 and Landsat-7 were combined with ground level measurements to estimate pecan ET and field scale actual crop coefficient (K c) for the LRGV. The results showed that annual pecan water use for 279 fields ranged from 498 to 1,259 mm with an average water use of 1,054 mm. For fields with NDVI > 0.6 (normalized difference vegetation index), which represented mature orchards (total of 232 fields), the annual water use ranged from 771 to 1,259 mm with an average water use of 1,077 mm. The results from remote sensing model compared reasonably well with ground level ET values determined by an eddy covariance system in a mature pecan orchard with an average error of 4% and the standard error of estimate (SEE) ranging from 0.91 to 1.06 mm/day. A small fraction (5%) of the pecan fields were within the range of maximum ET and K c.  相似文献   

19.
夏玉米生育期叶面蒸腾与棵间蒸发比例试验研究   总被引：6，自引：2，他引：4  
利用大型称重式蒸渗仪测定夏玉米生育期的总腾发量,用小型蒸发器测定棵间蒸发量,用茎流计测定叶面蒸腾量。通过3种设备实测数据的对比分析,得到夏玉米生育期的总耗水量为436.3 mm,其中叶面蒸腾316.4 mm,棵间蒸发119.9 mm,棵间蒸发占总腾发量的比例达到27.5%。茎流计所测得的蒸腾量与大蒸渗仪和小蒸发器联合测得的蒸腾量相关性良好,从而验证了用茎流计法测定叶面蒸腾方法的可行性。根据茎流计实测数据分析了叶面蒸腾的日变化过程,发现夏玉米叶面蒸腾与净辐射密切相关,呈周期性变化。  相似文献   

20.
河套灌区玉米农田蒸散动态变化及其影响因子的通径分析   总被引：1，自引：0，他引：1  
采用大型称重式蒸渗仪研究了内蒙古河套灌区玉米蒸散动态规律,并运用通径分析法探讨了玉米蒸散量ET与各影响因子间的相关关系.结果表明:充分灌溉处理下玉米生育期(播前-收获)累积蒸散量为593.72 mm,亏缺灌溉处理下为395.21 mm,日平均蒸散量分别为4.24和2.82 mm/d.由各生育期的分布情况可知苗期蒸散量最小,分别占全生育期的3.7%和5.8%;拔节期开始,蒸散量逐渐增大,在抽雄期达到峰值,2种处理总蒸散量分别为279.38和166.76 mm,日平均蒸散量分别为8.47和5.05 mm/d,分别占整个生育期蒸散总量的47.1%和42.2%.由小时尺度蒸散量变化规律可知,玉米日蒸散量变化规律表现为早晚低、中午高的“单峰型”曲线特征.通径分析表明:2种灌溉处理下,饱和水气压和平均气温对ET的综合决定能力较大,是2个主要的环境驱动因子;2种灌溉处理下对蒸散作用最小的因子均为风速,且风速对ET的影响以间接作用为主.影响河套灌区玉米蒸散的主要气象因子为饱和水气压与气温.  相似文献   

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