喷灌农田小气候变化及其对作物生长影响的研究进展

喷灌对田间小气候和作物生长的研究综述与分析认为：喷灌水滴蒸发和冠层截留蒸发是喷灌能够调节农田小气候的主要原因，喷灌水滴蒸发量一般小于25％，冠层截留一般在1％－42％的范围内，喷灌农田冠层温度降低，湿度增大，在寒冷季节，通过喷灌可改善作物冠层的热量状况，喷灌后田间作物光合速度提高，蒸腾强度降低，最终表现为喷灌条件作物耗水量较小，产量和水分利用效率较高，作物冠层的截留水量是喷灌能够长时间调节田间小气候的主要原因之一，进一步研究冠层截留水量在冠层内的分配，存储，冠层内的水汽交换，温湿度变化，冠层内水分的消散过程，喷灌后温湿度的空间分布等，将会更加清楚的解释喷灌条件下的作物耗水量和水分利用效率。     

喷灌条件下冬小麦灌浆期叶水势日变化及其影响因子研究

研究了冬小麦灌浆期叶水势在喷灌和地面灌溉(对照)条件下的日变化规律, 并探讨了其与农田生态因子(冠层空气温度、冠层空气相对湿度)和生理因子(气孔导度、蒸腾速率、细胞间隙 CO2浓度和光合速率)之间的关系.结果表明:与对照相比,喷灌条件下叶水势日变化曲线的变化趋势没有改变,但两种灌溉方式下叶水势的大小有显著差异,喷灌条件下冬小麦叶水势明显高于地面灌溉,在一天中8∶00～18∶00期间的不同时刻,两种灌溉方式下叶水势的差异大小表现为:在灌浆前期,喷灌和地面灌溉条件下叶水势的差异以在 8∶00时最大;在灌浆中期,差异以12∶00～16∶00期间最大;在灌浆后期,两种灌溉方式下一天中各时刻的差异微小,相对稳定.喷灌条件下冬小麦叶水势日变化的影响因子与地面灌溉条件下相比没有改变:灌浆前期,叶水势日变化均主要受生态因子冠层空气相对湿度、冠层空气温度的影响;灌浆中期,主要受生态因子冠层空气相对湿度、冠层空气温度和生理因子蒸腾速率的影响;灌浆后期,主要受生理因子光合速率的影响.但喷灌条件下各影响因子对叶水势的影响程度较地面灌溉条件下降低,表明喷灌条件下叶水势对影响因子变化的敏感性降低.     

半干旱偏湿润地区旱地小麦土壤水肥耦合的时空变异特征

为农作物精准施肥和管理,采用定点定位采样、室内分析的方法,在关中头道塬农田冬小麦生育全过程中,分层监测0～100 cm范围内土壤水分和养分的时空变异过程.结果表明:①土壤中水分和各主要养分主要集中在0～50 cm的剖面上,小麦在返青、拔节、灌浆期对水分和养分的需求量教多,因此,剖面上水分养分在此阶段发生剧烈变动,在时间上出现了水分和养分同步变化现象.土壤速效磷前期比较稳定,返青以后变化幅度较大;土壤速效钾含量在分蘖期保持较高水平,抽穗期含量明显降低.②不同土层的水分和养分的变异性不同.在小麦生育期间表层0～10 cm水分含量变异性最大,很难保证稳定的土壤墒情,该层对于作物生长属于极度危险层;其下各层土壤墒情稳定性逐渐增强,能满足作物生长的要求;土壤的硝态氮和碱解氮最大变异性也出现在0～10 cm范围,证实作物对速效氮的耗竭和氮素的转化过程主要发生在该土层内,随土层深度增加,其变异性减小;速效磷在0～30 cm剖面上变异最大,速效钾在整个剖面上变异性不显著.土壤水分和养分,空间上存在着不够协调的问题,建议应当根据土壤墒情,在旱塬地区进行肥料深施,以缓解水分和养分的空间错位矛盾.     

西南高原“旱三熟”地区不同覆盖栽培措施的土壤水分效应

在西南高原季节性旱区进行田间试验,研究不同覆盖栽培条件下"旱三熟"种植模式的农田土壤水分效应。研究表明,秸秆、地膜覆盖尤其是秸秆地膜二元覆盖有明显蓄集和保存土壤水的作用,土壤保蓄水度平均提高60.63%,覆盖能有效减少田间水分的无效蒸发,平均减少181.93 mm,使作物蒸腾系数和水分利用效率提高,平均提高19.84%和23.5%,而使作物耗水系数减小,平均减少18.26%,根区是作物耗水与土壤保蓄水的关键区域;农田水分变化沿土层可划分为3个层次,即0~30 cm土层为土壤水分变化活跃层和土壤贮水变化明显层、30~80cm土层为土壤水分变化次活跃层和土壤贮水变化显著层、80~100 cm土层为土壤水分变化相对稳定层和土壤贮水变化缓慢层。覆盖栽培可促进作物耗水量由田间无效蒸发耗水向有效的田间作物蒸腾耗水转化,使农田水分的有效性显著提升。     

黑河流域中游制种玉米农田土壤水分运移规律

基于2009年中国科学院临泽内陆河流域研究站绿洲农田小气候、土壤蒸发和土壤水分动态监测等多源观测试验数据,运用Hydrus-1D模型模拟大田制种玉米生长条件下,土壤水分运移过程和各水分通量,并对当前灌溉制度下农田水分利用率进行评估.结合相关监测数据对模拟结果进行评价,整个模拟期作物蒸腾量、土壤蒸发量、土壤蓄水变化量和渗漏量分别为316.4、100.3、45.5 mm和339.5 mm.玉米在初生阶段、发育阶段、中期阶段、后期阶段的蒸腾水量占灌溉水分的3.6％、10.6％、46.7％和49.6％,占蒸散量的7.2％、28％、82.7％和81.4％.农田系统各水分通量的变化规律及相对比例明显受作物生长和灌水事件影响,当前灌溉制度下农田水分利用率较低,在初生阶段减少土壤蒸发和中后期阶段增加灌溉频率、减少灌溉定额是提高干旱区灌溉水分利用效率的有效手段.     

喷灌条件下冬小麦冠层温度的试验研究

研究了喷灌条件下冬小麦冠层温度在不同土壤水分条件下的变化规律及其随作物生长发育期的变化状况。结果表明．在喷灌条件下,冠层温度的变化规律同普通灌溉的变化规律基本相同。当灌水量达一定程度后,冠层温度不再下降,反而呈现上升趋势;土壤水分对冠层温度的影响程度相对减小,不为主要决定因子;对于冬小麦．．当灌溉量增加到一定程度时,反而不利于冬小麦的生长,水分利用效率也下降,在灌足底墒水和返青、拔节期均灌溉的情况下,小麦生长期间每次灌水量不宜过大,以每次灌水量不超过300m^3／hm^3为宜。     

紫花苜蓿中心支轴式喷灌灌水均匀性试验研究

为提高紫花苜蓿中心支轴式喷灌灌水均匀性及定量分析其主要影响因子,在鄂尔多斯市鄂托克前旗昂素镇示范区进行了紫花苜蓿中心支轴式喷灌灌水均匀性试验,采用基于标准差的Wilcox-Swailes均匀系数法计算了不同风速条件下的喷灌灌水均匀系数,并定量化研究了喷灌对漂移损失、冠层截留损失、漂移和冠层截留总损失以及土壤含水率的影响。结果表明:风速对喷灌灌水均匀系数影响显著,平均风速为2.57 m·s~(-1)和1.53 m·s~(-1)时均匀系数分别达到0.88和0.92,说明喷灌均匀性良好,平均风速为3.34 m·s~(-1)时均匀系数为0.72,喷灌均匀性较差;研究区喷灌灌水定额40 mm时最大土壤入渗深度为80 cm,灌水后0~40 cm土层土壤含水率的提高非常显著,新增灌水量在该土层的分配占85.0%~95.0%;风速对喷灌漂移损失影响显著,随着风速的增大漂移损失率明显提高;风速对冠层截留损失影响不如对漂移损失的影响显著,较大风速时冠层截留损失率反而较低;即使在风速较低时(1.53 m·s~(-1))紫花苜蓿分枝期喷灌漂移和冠层截留总损失率也在11.0%~15.0%,损失较大。     

基于冠层温度的玉米缺水诊断研究

冠层温度是判断植物水分状况的一项重要指标。以玉米良玉11为试验作物,在2014和2015年玉米抽雄期(7—8月)进行了4种不同梯度的土壤水分胁迫处理,研究了作物冠层温度、冠气温度比以及冠气温度差等指标与土壤含水量的关系,分析了冠气温度比与生理指标气孔导度的关系。研究结果显示:当土壤含水量低于0.16 cm3·cm~(-3)时,植株出现了明显的萎蔫现象,这时冠层温度、冠气温度比、冠气温度差也都分别达到了其最大值34℃,1.2℃和5℃;随着土壤含水量增大到0.20 cm3·cm~(-3),冠层温度等指标均达到其最小值,约为30℃,1.0℃和1℃,且变化比较稳定,这时植株生长良好,说明土壤供水充足,植株未受到水分胁迫。冠层温度等指标与气孔导度有显著的线性关系,气孔导度随着冠层温度等指标的增加而线性降低,表明气孔关闭会使得冠层温度显著提升。     

旱区间作水分高效利用机制探讨

间作系统充分利用光热水肥资源具有高产高效特征，在旱区得到了广泛应用。综合国内外间作群体水分利用的研究成果，论述了间作具有水分优势的高效利用机制。间作系统减少土壤蒸发、提高作物蒸腾、降低棵间蒸发与耗水量的比值，增加土壤水分的有效性，提高作物根系对土壤水分的吸收利用，进而提高水分利用效率。间作系统的水分利用机制包括生态位分离减少竞争以促进资源的充分利用、水力再分配调节作物及邻体作物土壤的水分条件缓解旱区作物的水分胁迫。间作系统水分利用的影响因素包括作物种类、种植密度和空间布局、水肥管理和耕作措施。针对研究中的不足，指出未来间作系统水分高效利用研究应关注以下方面：不同区域间作群体增产和节水的规律；水分与源库关系及对种间关系的响应；量化水分与根系生长的关系，建立间作作物对水分吸收的模型；地下部对间作水分优势的响应。     

试论秦岭—黄淮平原交界带的农田水分旱涝指标

从“土壤－植物－大气”水分连续系统出发，根据农田水分平衡方程及土壤分的有效性和作物吸水之间的关系，和岭东伸余脉－伏牛山与黄淮平原交界带的农田水分旱涝指标进行了论证。     

Effects of the growing-maize canopy and irrigation characteristics on the ability to funnel sprinkler water

Stemflow is vital for supplying water, fertilizer, and other crop essentials during sprinkler irrigation. Exploring the spatial and temporal variations of crop stemflow and its influencing factors will be essential to preventing soil water and nutrient ion's migration to deeper layers, developing, and optimizing effective sprinkler irrigation schedules. Based on the two-year experimental data, we analyzed the variation patterns (stemflow amount, depth, rate, and funneling ratio) of maize stemflow during the growing season, and clarified its vertical distribution pattern. Meanwhile, effects of sprinkler irrigation and maize morphological parameters on stemflow were investigated. The results showed that stemflow increased gradually as maize plant grew. Specifically, stemflow was small at the pre-jointing stage and reached the maximum at the late filling stage. The upper canopy generated more stemflow than the lower canopy until the flare opening stage. After the tasseling stage, the middle canopy generated more stemflow than the other positions. Variation in canopy closure at different positions was the main factor contributing to the above difference. As sprinkler intensity increased, stemflow also increased. However, the effect of droplet size on stemflow was inconsistent. Specifically, when sprinkler intensity was less than or equal to 10 mm/h, stemflow was generated with increasing droplet size. In contrast, if sprinkler intensity was greater than or equal to 20 mm/h, stemflow tended to decreased with increasing droplet size. Compared with other morphological parameters, canopy closure significantly affected the generation of stemflow. Funneling ratio was not significantly affected by plant morphology. Based on the results of different sprinkler intensities, we developed stemflow depth versus canopy closure and stemflow rate versus canopy closure power function regression models with a high predictive accuracy. The research findings will contribute to the understanding of the processes of stemflow involving the hydro-geochemical cycle of agro-ecosystems and the implementation of cropland management practices.     

Mulching mode and planting density affect canopy interception loss of rainfall and water use efficiency of dryland maize on the Loess Plateau of China

High and efficient use of limited rainwater resources is of crucial importance for the crop production in arid and semi-arid areas. To investigate the effects of different soil and crop management practices(i.e., mulching mode treatments: flat cultivation with non-mulching, flat cultivation with straw mulching, plastic-covered ridge with bare furrow and plastic-covered ridge with straw-covered furrow; and planting density treatments: low planting density of 45,000 plants/hm~2, medium planting density of 67,500 plants/hm~2 and high planting density of 90,000 plants/hm~2) on rainfall partitioning by dryland maize canopy, especially the resulted net rainfall input beneath the maize canopy, we measured the gross rainfall, throughfall and stemflow at different growth stages of dryland maize in 2015 and 2016 on the Loess Plateau of China. The canopy interception loss was estimated by the water balance method. Soil water storage, leaf area index, grain yield(as well as it components) and water use efficiency of dryland maize were measured or calculated. Results showed that the cumulative throughfall, cumulative stemflow and cumulative canopy interception loss during the whole growing season accounted for 42.3%–77.5%, 15.1%–36.3% and 7.4%–21.4% of the total gross rainfall under different treatments, respectively. Soil mulching could promote the growth and development of dryland maize and enhance the capability of stemflow production and canopy interception loss, thereby increasing the relative stemflow and relative canopy interception loss and reducing the relative throughfall. The relative stemflow and relative canopy interception loss generally increased with increasing planting density, while the relative throughfall decreased with increasing planting density. During the two experimental years, mulching mode had no significant influence on net rainfall due to the compensation between throughfall and stemflow, whereas planting density significantly affected net rainfall. The highest grain yield and water use efficiency of dryland maize were obtained under the combination of medium planting density of 67,500 plants/hm~2 and mulching mode of plastic-covered ridge with straw-covered furrow. Soil mulching can reduce soil evaporation and retain more soil water for dryland maize without reducing the net rainfall input beneath the maize canopy, which may alleviate the contradiction between high soil water consumption and insufficient rainfall input of the soil. In conclusion, the application of medium planting density(67,500 plants/hm~2) under plastic-covered ridge with bare furrow is recommended for increasing dryland maize production on the Loess Plateau of China.     

喷灌冬小麦农田土壤水分分布特征及水量平衡

以传统地面灌溉(畦灌)为对照,分析了喷灌条件下,冬小麦农田土壤水分分布特征和水量平衡。结果表明:喷灌条件下土壤水分运动表现出明显的非饱和土壤水运动特征,地面灌溉条件下土壤水分运动具有饱和土壤水运动的特征。喷灌条件下灌溉水主要分布在土壤表层0~50 cm范围内,地面灌溉条件下灌溉水可达地表以下150 cm处。喷灌条件下,没有明显的土壤水分渗漏发生;地面灌溉条件下,土壤水分渗漏量占灌溉水量的10%左右。2003年和2004年试验期间,喷灌蒸散量分别为312.2 mm和324.4 mm,分别比地面灌溉蒸散量少13.1 mm和35.1mm。     

Canopy interception loss in a Pinus sylvestris var. mongolica forest of Northeast China

Pinus sylvestris var. mongolica is one of the main species to be afforested in deserts of China. But little work has been carried out on the canopy interception loss of this plant species. For researching the canopy interception loss of a natural P. sylvestris forest, we observed the gross precipitation, gross snowfall, throughfall and stemflow in a sample plot at the Forest Ecosystem Research Station of Mohe in the Great Khingan Mountains of Northeast China from July 2012 to September 2013. Considering the spatial variability of the throughfall, we increased the area rather than the number of collector and randomly relocated them once a week. The results demonstrated that the throughfall, stemflow, and derived estimates of rainfall and snowfall interception loss during the main rainy and snowy seasons were 77.12%±5.70%, 0.80%, 22.08%±5.51% and 21.39%±1.21% of the incident rainfall or snowfall, respectively. The stemflow didn't occur unless the accumulated rainfall reached up to 4.8 mm. And when the gross precipitation became rich enough, the stemflow increased with increasing tree diameters. Our analysis revealed that throughfall was not observed when rainfall was no more than 0.99 mm, indicating that the canopy storage capacity at saturation was 0.99 mm for P. sylvestris forest.     

干旱区棉花水分胁迫指数对滴灌均匀系数和灌水量的响应

为了修订和完善滴灌均匀系数的设计与评价标准,在新疆干旱区研究了滴灌均匀系数和灌水量对作物水分胁迫指数（CWSI）的影响。供试作物为棉花,试验中滴灌均匀系数（C_u）设置0.65（C1）、0.78（C2）和0.94（C3）三个水平,灌水量设置充分灌水量的50%、75%和100%三个水平。结果表明：棉花冠层温度和CWSI表现出随灌水量增加而降低的趋势;冠层温度和CWSI均匀系数的变化范围分别为0.91～0.98和0.65～0.91,均随滴灌均匀系数增加而增大;灌水量对冠层温度和CWSI均值的影响达到极显著水平（α=0.01）,滴灌均匀系数对冠层温度和CWSI均匀系数的影响达到显著水平（α=0.05）或极显著水平。CWSI与皮棉产量呈显著或极显著的负相关关系;滴灌均匀系数越低,水分亏缺引起的减产幅度越小。     

甘肃河西地区不同储水灌溉和生育期灌溉农田水分特征分析

对甘肃河西地区不同储水灌溉和生育期灌溉农田水分特征进行了试验研究.结果表明:在河西地区,冬季储水灌溉定额为180 mm的处理,其生育期剖面的土壤水分较多地分布在140～160 cm,且土壤含水量达到30%以上,容易发生深层渗漏;较小的储水灌溉定额,土壤水分主要分布在0～100 cm范围内,不会引起土壤剖面水分的深层渗漏.冬季储水灌溉定额愈大,春播前农田无效土壤蒸发也愈大.冬季储水灌溉定额相同,生育期灌溉定额大的处理其剖面含水量高,且分布愈深,深层土壤的水分渗漏也愈大.总的灌水定额相同,冬季储水灌溉和生育期灌溉比较,生育期灌溉定额较大的处理,剖面水分的分布主要集中在0～100 cm的土层内,没有出现易发生深层渗漏较高的水分分布.在小麦生育期,总的灌溉定额相同的条件下,冬季储水灌溉定额大的处理,0～200 cm土壤水分有亏缺,冬季储水灌溉定额大或生育期灌溉定额大,农田腾发量也愈大.适中的储水灌溉定额,不仅有利于作物的生长,还有利于灌溉水分利用效率的提高.     

Non-negligible factors in low-pressure sprinkler irrigation: droplet impact angle and shear stress

Droplet shear stress is considered as an important indicator that reflects soil erosion in sprinkler irrigation more accurately than kinetic energy, and the effect of droplet impact angle on the shear stress cannot be ignored. In this study, radial distribution of droplet impact angles, velocities, and shear stresses were investigated using a two-dimensional video disdrometer with three types of low-pressure sprinkler (Nelson D3000, R3000, and Komet KPT) under two operating pressures (103 and 138 kPa) and three nozzle diameters (3.97, 5.95, and 7.94 mm). Furthermore, the relationships among these characteristical parameters of droplet were analyzed, and their influencing factors were comprehensively evaluated. For various types of sprinkler, operating pressures, and nozzle diameters, the smaller impact angles and larger velocities of droplets were found to occur closer to the sprinkler, resulting in relatively low droplet shear stresses. The increase in distance from the sprinkler caused the droplet impact angle to decrease and velocity to increase, which contributed to a significant increase in the shear stress that reached the peak value at the end of the jet. Therefore, the end of the jet was the most prone to soil erosion in the radial direction, and the soil erosion in sprinkler irrigation could not only be attributed to the droplet kinetic energy, but also needed to be combined with the analysis of its shear stress. Through comparing the radial distributions of average droplet shear stresses among the three types of sprinklers, D3000 exhibited the largest value (26.94-3313.51 N/m²), followed by R3000 (33.34-2650.80 N/m²), and KPT (16.15-2485.69 N/m²). From the perspective of minimizing the risk of soil erosion, KPT sprinkler was more suitable for low-pressure sprinkler irrigation than D3000 and R3000 sprinklers. In addition to selecting the appropriate sprinkler type to reduce the droplet shear stress, a suitable sprinkler spacing could also provide acceptable results, because the distance from the sprinkler exhibited a highly significant (P<0.01) effect on the shear stress. This study results provide a new reference for the design of low-pressure sprinkler irrigation system.     

无压灌溉日光温室番茄作物-皿系数研究

以-25 kPa作为土壤水势临界值,将作物-皿系数(Kcp)设为0.2,0.4,0.6,0.8,1.0,1.2六个处理, 研究了不同灌溉水量时的番茄产量、品质和灌溉水利用效率.通过经济效益评价,研究了杨凌地区无压灌溉温室番茄获得最高经济效益时的作物-皿系数.通过张力计读数变化规律,研究了利用张力计测量无压灌溉湿润体内土壤水势的特点.研究结果表明,Kcp为0.2～0.8时, 灌溉水量的增加对番茄产量影响不大;Kcp为1.0～1.2时,灌溉水量的增加能显著提高番茄产量和果实大小;Kcp为0.2时的灌溉水量能极显著提高番茄的灌溉水利用效率.在综合考虑了杨凌地区水价、番茄使用目的和市场价格波动规律后,Kcp取值1.2能获得最高的经济效益.作物-皿系数法计算灌溉水量时的滞后性特点和张力计埋设位置,是判断利用张力计监测土壤水势临界值方法有效性的两个重要因素.