华北地区是我国冬小麦的主要产区，近年来，华北地区大量抽取地下水进行农业灌溉，引发了严重的地下水超采问题，严重威胁当地农业的可持续发展。喷灌是目前世界范围内应用最为广泛的节水灌溉技术之一，由于其具有提高水分利用效率和粮食产量的潜力，在华北平原中得到了越来越广泛的应用。在此背景下，进行喷灌条件下田间小气候变化特征及作物水分利用效率的研究，对华北地区节水增产，缓解水资源短缺现状具有积极的意义。本文以河北省宁晋县大曹庄管理区种子发展中心作为试验基地，在田间根据支管和喷头间距的不同，设置LP（18 m×24 m）、MP（18 m×18 m）、SP（18 m×12 m）三种不同喷灌小区，通过地面仪器和低空遥感设备，观测了喷灌过程中不同处理小区冠层及其周围的水量分布情况，以及农田小气候的变化过程，探究了小气候和喷灌均匀度对冬小麦生长过程、产量及水分利用效率的影响。研究得出的主要结论如下：

（1）各试验小区的喷灌水量均呈现出中心区域水量较多，边缘区域水量较少的分布规律；冬小麦冠层截留量至灌浆期相对稳定，约为0.9 mm，截留水量变化范围为0.6~1.5 mm；茎流率的变化范围在21.8~44.3%，穿透率变化范围为52.4~64.2%，平均茎流率和穿透率分别为32.3%和58.9%；冬小麦冠层会影响喷灌水量的分布情况，其中茎流水量是影响冠层下水量分布均匀度的主要因素，在喷灌均匀度较低时，冠层下水量分布较冠层上更均匀；但是当喷灌均匀度较高时（CU约为0.8），冠层会使得地面水量分布均匀性趋于一致；群体密度是影响茎流水量分布的主要因素，与茎流水深在1%水平上呈正相关关系。

（2）喷灌前后冠层多光谱影像具有明显的区别，为了消除作物冠层自身的归一化植被指数值（NDVI）对试验的影响，计算喷灌前后植被冠层的相对归一化植被指数（NDVI），小麦冠层NDVI值与冠层截留水量在1%的水平上呈现出显著的正相关关系，构建了基于NDVI的冠层截留水量估算公式（R²=0.78）。

（3）喷灌可迅速改变田间小气候，对田间温度的影响时长约为1～3天，对相对湿度及饱和水汽压差的影响时长约为1～2天；喷灌对于田间小气候的影响范围与喷灌水量的覆盖范围（18m）接近；喷灌区域内温度和湿度的变化会受环境因素的制约，特别是风速较大时，受喷灌影响的空气温湿度以及饱和水汽压差的变化区域会向顺风侧发生偏移，当风速达到5 m/s时，最大偏移量可达12 m。

（4）喷灌均匀度对冬小麦群体密度、株高、叶面积指数影响不显著，但对于LP小区，由于喷头间距较远，喷灌水量主要集中在中心区域，因此LP处理小区的这三个生长指标始终显著小于MP和SP处理的小区。喷灌均匀度对干生物量具有一定的影响，随着喷灌均匀度的提高生物量有相应的提升，两者呈现正相关关系。

（5）喷灌均匀度与冬小麦产量呈正相关关系，但总体对产量影响不显著。在灌水量较为充足的条件下，冬小麦主要通过影响产量的变异系数影响产量，冬小麦产量离差系数CV_WY与喷灌均匀度CU呈显著的负相关性，表明喷灌水量越均匀，不同测产点产量的差异性越小。两年内冬小麦的灌溉水分生产率的结果与作物水分生产率一致；喷灌均匀度与作物水分生产率和灌溉水分生产率均呈正相关关系，喷灌均匀度的提升有利于提高水分利用效率。

North China is the main production area of winter wheat in China. In recent years, large amount of groundwater have been extracted for agricultural irrigation, which has triggered serious groundwater over-extraction problems and seriously threatened the sustainable development of local agriculture. Sprinkler irrigation is currently one of the most widely used water-saving irrigation technologies in the world and has been increasingly used in the North China Plain because of its potential to improve water use efficiency and grain yield. In such context, the study of microclimate change and crop water use efficiency in the field under sprinkler irrigation conditions is of positive significance to save water and increase production and alleviate the current water shortage in North China. In this paper, three different sprinkler layout forms were set up in the field according to the spacing of branch pipes and sprinklers (LP:18 m×24 m; MP:18 m×18 m; SP:18 m×12 m). The water distribution around the canopy of different treatments during the sprinkler irrigation process and the micro-climate change in the field were observed by ground instruments and low-altitude remote sensing equipment. The study was conducted to investigate the influence of micro-climate on crop growth, to evaluate the comprehensive benefits of sprinkler irrigation technology in water saving, improving crop growth environment and water use efficiency, and to develop a scientific study on the effect of sprinkler uniformity on the growth process, yield and water use efficiency of winter wheat. The study concluded as follows:

(1) The sprinkler irrigation water in each treatment showed a distribution pattern of more water in the central area and less water in the marginal area; the canopy interception water of winter wheat was relatively stable at about 0.9 mm, and the interception varied from 0.6 to 1.5 mm; the stem flow rate varied from 21.8 to 44.3% and the penetration rate varied from 52.4 to 64.2%, with 32.3% average stem flow rate and the 58.9% average penetration rate. The canopy of winter wheat affects the distribution of sprinkler water, where stem flow water is the main factor affecting the uniformity of water distribution under the canopy. When the sprinkler uniformity is low, the distribution of water under the canopy is more uniform than that on the canopy; however, when the sprinkler uniformity is high (approximately CU value of 0.8), the presence of the canopy reduces the uniformity of water distribution under the canopy. Population density are the main factors affecting the distribution of stem flow water, which is positively correlated with stem flow water depth at the 1% level.

(2) The multispectral images of the canopy had obvious differences after sprinkler irrigation. In order to eliminate the influence of the NDVI of the crop canopy itself on the experiment, the NDVI of the vegetation canopy before and during sprinkler irrigation was calculated, and NDVI of the wheat canopy showed a significant positive correlation with the canopy water interception at the 1% level, and an NDVI-based canopy water interception estimation formula was constructed (R²=0.78).

 (3) Sprinkler irrigation can rapidly change the air temperature, relative humidity and VPD, the influence on the field temperature is about 1 to 3 days, but the influence on the relative humidity and VPD is about 1 to 2 days; the influence range of sprinkler irrigation on the air temperature and the relative humidity is close to the coverage of sprinkler water (18 m). The changes of temperature, humidity and VPD in the sprinkler area will be constrained by the environmental factors, especially when the influence of wind speed is large, the temperature, humidity and VPD of the area affected by the sprinkler changes will shift to the downwind side, which could be 12 m when the wind speed is 5 m/s.

 (4) The effect of sprinkler uniformity on winter wheat population density, plant height, and leaf area index was not significant, but the growth of winter wheat in the marginal area was under water stress due to the large concentration of sprinkler water in the center of the LP treatment, so these three growth indexes in the LP treatment were always significantly smaller than those in the other treatment. Sprinkler uniformity had a certain effect on the dry biomass of winter wheat, and the two showed a positive correlation.

(5) Sprinkler uniformity was positively correlated with winter wheat yield, but had a small effect on yield. Under the condition of more adequate irrigation water, winter wheat mainly affected yield through the coefficient of variation that influenced yield. CV_WY, the coefficient of variation of winter wheat yield, showed a significant negative correlation with CU, the uniformity of sprinkler irrigation, indicating that the more uniform the sprinkler irrigation water, the less variability of yield at different yield measurement sites. The results of irrigation water productivity of winter wheat in two years were consistent with crop water productivity; sprinkler uniformity was positively correlated with both crop water productivity and irrigation water productivity, and the improvement of sprinkler uniformity was beneficial to improve water use efficiency.