Root zone soil moisture redistribution in maize (<i>Zea mays</i>L.) under different water application regimes

Soil moisture availability to plant roots is very important for crop growth. When soil moisture is not available in the root zone, plants wilt and yield is reduced. Adequate knowledge of the distribution of soil moisture within crop’s root zone and its linkage to the amount of water applied is very important as it assists in optimising the efficient use of water and reducing yield losses. The study aimed at evaluating the spatial redistribution of soil moisture within maize roots zone under different irrigation water application regimes. The study was conducted during two irrigatation seasons of 2012 at Nkango Irrigation Scheme, Malawi. The trials consisted of factorial arrangement in a Randomised Complete Block Design (RCBD). The factors were water and nitrogen and both were at four levels. The Triscan Sensor was used to measure volumetric soil moisture contents at different vertical and lateral points. The study inferred that the degree of soil moisture loss depends on the amount of water present in the soil. The rate of soil moisture loss in 100% of full water requirement regime (100% FWRR) treatment was higher than that in 40% FWRR treatment. This was particularly noticed when maize leaves were dry. In 100% FWRR treatment, the attraction between water and the surfaces of soil particles was not tight and as such “free” water was lost through evaporation and deep percolation, while in 40% FWRR, water was strongly attracted to and held on the soil particles surfaces and as such its potential of losing water was reduced.

Spatio-temporal variation of soil moisture in a fixed dune at the southern edge of the Gurbantunggut Desert in Xinjiang, China

Soil moisture is critical for vegetation growth in deserts.However,detailed data regarding the soil moisture distribution in space and time in the Gurbantunggut Desert of China have not yet been reported.In this study,we conducted a series of in situ observation experiments in a fixed sand dune at the southern edge of the Gurbantunggut Desert from February 2014 to October 2016,to explore the spatio-temporal variation of soil moisture content,investigate the impact of Haloxylon ammodendron(C.A.Mey.)Bungeon soil moisture content in its root zone,and examine the factors influencing the soil moisture spatial pattern.One-way analysis of variance,least significant difference tests and correlation analysis were used to analyze the data.The results revealed that the soil moisture content exhibited annual periodicity and the temporal variation of soil moisture content throughout a year could be divided into three periods,namely,a moisturegaining period,a moisture-losing period and a moisture-stable period.According to the temporal and spatial variability,the 0–400 cm soil profile could be divided into two layers:an active layer with moderate variability and a stable layer with weak variability.The temporal variability was larger than the spatial variability in the active layer,and the mean profile soil moisture content at different slope positions displayed the trend of decreasing with increasing relative height and mainly followed the order of interdune area>west and east slopes>slope top.The mean profile soil moisture content in the root zone of dead H.ammodendron individuals was significantly higher than that in the root zones of adult and young individuals,while the soil moisture content in the root zone of adult individuals was slightly higher than that in the root zone of young individuals with no significant difference.The spatial pattern of soil moisture was attributable to the combined effects of snowfall,vegetation and soil texture,whereas the effects of rainfall and evaporation were not significant.The findings may offer a foundation for the management of sandy soil moisture and vegetation restoration in arid areas.

Modeling regional landslide susceptibility using dynamic soil moisture profiles

A landslide susceptibility mapping study was performed using dynamic hillslope hydrology. The modified infinite slope stability model that directly includes vadose zone soil moisture(SM) was applied at Cleveland Corral, California, US and Krishnabhir, Dhading, Nepal. The variable infiltration capacity(VIC-3L) model simulated vadose zone soil moisture and the wetness index hydrologic model simulated groundwater(GW). The GW model predictions had a 75% NASH-Sutcliffe efficiency when compared to California's in-situ GW measurements. The model performed best during the wet season. Using predicted GW and VIC-3L vadose zone SM, the developed landslide susceptibility maps showed very good agreement with mapped landslides at each study region. Previous quasi-dynamic model predictions of Nepal's hazardous areas during extreme rainfall events were enhanced to improve the spatial characterization and provide the timing of hazardous conditions.

Stem sap flow of Haloxylon ammodendron at different ages and its response to physical factors in the Minqin oasis-desert transition zone, China

Haloxylon ammodendron, with its tolerance of drought, high temperature, and salt alkali conditions, is one of the main sand-fixing plant species in the oasis-desert transition zone in China. This study used the TDP30(where TDP is the thermal dissipation probe) to measure hourly and daily variations in the stem sap flow velocity of H. ammodendron at three age-classes(10, 15, and 20 years old,which were denoted as H10, H15, and H20, respectively) in the Minqin oasis-desert transition zone,China, from May through October 2020. By simultaneously monitoring temperature, relative humidity,photosynthetically active radiation, wind speed, net radiation, rainfall, and soil moisture in this region, we comprehensively investigated the stem sap flow velocity of different-aged H. ammodendron plants(H10,H15, and H20) and revealed its response to physical factors. The results showed that, on sunny days, the hourly variation curves of the stem sap flow velocity of H. ammodendron plants at the three age-classes were mainly unimodal. In addition, the stem sap flow velocity of H. ammodendron plants decreased significantly from September to October, which also delayed its peak time of hourly variation. On rainy days, the stem sap flow velocity of H. ammodendron plants was multimodal and significantly lower than that on sunny days.Average daily water consumption of H. ammodendron plants at H10, H15, and H20 was 1.98, 2.82, and 1.91kg/d, respectively. Temperature was the key factor affecting the stem sap flow velocity of H. ammodendron at all age-classes. Net radiation was the critical factor influencing the stem sap flow velocity of H.ammodendron at H10 and H15;however, for that at H20, it was vapor pressure deficit. The stem sap flow velocity of H. ammodendron was highly significantly correlated with soil moisture at the soil depths of 50and 100 cm, and the correlation was strengthened with increasing stand age. Altogether, our results revealed the dynamic changes of the stem sap flow velocity in different-aged H. ammodendron forest stands and its response mechanism to local physical factors, which provided a theoretical basis for the construction of new protective forests as well as the restoration and protection of existing ones in this region and other similar arid regions in the world.

黄河孟津段河岸带土壤有机碳分布特征及影响因素分析

【目的】探究黄河孟津段河岸带土壤有机碳空间分布差异及规律,为黄河河岸带土壤固碳和生态修复提供理论依据。【方法】以河岸带表层土壤为研究对象,采用克里金插值法和冗余分析对土壤有机碳空间分布及影响因素进行分析,探讨土壤有机碳含量与微地形、土壤物理性质及植被组合的相关关系。【结果】研究区土壤有机碳含量和土壤有机碳密度的平均值分别为1.94 g·kg^(-1)和0.11 kg·m^(-2),空间变异系数分别为69.9%和83.6%,均属于中等程度变异。研究区土壤有机碳含量在随垂直河流方向距离V1—V5样带的增加而增加,V5样带土壤有机碳含量显著高于V1—V3这3个样带。相关性分析和冗余分析中,研究区土壤有机碳含量与垂直河流距离、土壤含水率、土壤黏粒呈极显著正相关,与土壤砂粒呈极显著负相关,与植物群落、海拔无显著相关。【结论】河岸带土壤有机碳含量随垂直河流方向距离的增加而增加,空间自相关性强,河岸带微地形、土壤黏粒和土壤含水率显著影响土壤有机碳的空间分布。

基于SMAR模型的森林小流域根区土壤湿度模拟

根区土壤水分(RZSM)对水文模拟和农业管理等具有重要作用,但直接测量RZSM难度很大。SMAR模型可模拟RZSM的变化,但目前在复杂地形地区的应用还较少。使用美国Shale Hills流域32个站点土壤水分剖面三年期间(2011~2014年)的日实测数据,探究基于物理机制的SMAR模型对RZSM模拟的准确性,评价该方法不同时空条件下的模拟性能。研究结果表明,SMAR模型能够准确利用表层土壤水分(SSM)数据估计RZSM;模拟结果与实测数据相比,平均RRMSE为0.034,说明能够很好地模拟出流域尺度根系层土壤湿度空间分布情况。从时间上看,模型在湿冷季节的准确性优于在干暖季节的准确性。研究结果增加了对复杂地形下利用SSM模拟RZSM的理解,为复杂地形条件下根系土壤层湿度的模拟提供了支撑。

全球旱地饱和水汽压差和根区土壤水分变化对植被生产力的影响及其成因

旱地约占全球陆地面积的40%,而水分是旱地植被生长的一大限制要素。尽管土壤水分与饱和水汽压差对植被生长的重要性已经得到了广泛证实,然而目前二者对植被生产力影响的空间异质性及其形成因素仍未得到深入研究,这对研究旱地生态系统对气候变化的响应带来了挑战。为了填补这一认知空白,研究收集了多源气象、根区土壤含水率和总初级生产力产品,基于随机森林算法量化了植被总初级生产力对根区土壤含水率和饱和水汽压差的敏感性,结合土地覆盖数据和分档平均方法分析了敏感性空间异质性的形成机制。结果表明:全球旱地饱和水汽压差与植被生产力总体呈显著上升趋势;根区土壤水分对植被生长的影响以正效应主导,饱和水汽压差对植被生长的影响以负效应主导;相较于森林和灌木,饱和水汽压差对植被生长的负效应及根区土壤含水率对植被生长的正效应在农田、草地和苔原及半干旱区更为强烈;植被生产力对饱和水汽压差和根区土壤水分的敏感性在数量上总体呈显著的线性负相关性。综上,植被种类和气候条件是导致全球旱地植被生产力对土壤水分和饱和水汽压差敏感性空间异质性的重要因素。

Soil moisture-based study of the variability of dry-wet climate and climate zones in China

An ensemble soil moisture dataset was produced from 11 of 25 global climate model (GCM) simulations for two climate scenarios spanning 1900 to 2099; this dataset was based on an evaluation of the spatial correlation of means and trends in reference to soil moisture simulations conducted using the community land model driven by observed atmospheric forcing. Using the ensemble soil moisture index, we analyzed the dry-wet climate variability and the dynamics of the climate zone boundaries in China over this 199-year period. The results showed that soil moisture increased in the typically arid regions, but with insignificant trends in the humid regions; furthermore, the soil moisture exhibited strong oscillations with significant drought trends in the transition zones between arid and humid regions. The dynamics of climate zone boundaries indicated that the expansion of semiarid regions and the contraction of semi-humid regions are typical characteristics of the dry-wet climate variability for two scenarios in China. During the 20th century, the total area of semiarid regions expanded by 11.5% north of 30°N in China, compared to the average area for 1970-1999, but that of semi-humid regions decreased by approximately 9.8% in comparison to the average for the period of 1970-1999, even though the transfer area of the humid to the semi-humid regions was taken into account. For the 21st century, the dynamics exhibit similar trends of climate boundaries, but with greater intensity.

Different environmental factors drive tree species diversity along elevation gradients in three climatic zones in Yunnan,southern China

Elevational patterns of tree diversity are well studied worldwide.However,few studies have examined how seedlings respond to elevational gradients and whether their responses vary across climatic zones.In this study,we established three elevational transects in tropical,subtropical and subalpine mountain forests in Yunnan Province,southern China,to examine the responses of tree species and their seedlings to elevational gradients.Within each transect,we calculated species diversity indices and composition of both adult trees and seedlings at different elevations.For both adult trees and seedlings,we found that species diversity decreased with increasing elevation in both tropical and subalpine transects.Species composition showed significant elevational separation within all three transects.Many species had specific elevational preferences,but abundant tree species that occurred at specific elevations tended to have very limited recruitment in the understory.Our results highlight that the major factors that determine elevational distributions of tree species vary across climatic zones.Specifically,we found that the contribution of air temperature to tree species composition increased from tropical to subalpine transects,whereas the contribution of soil moisture decreased across these transects.

Time-Lapse Electrical Resistivity Tomography Monitoring of Recharge in the Unsaturated Zone

Geophysical experiments have the ability to provide minimally invasive,nearly continuous,and spatially extensive estimates of material properties for near-surface investigations.The Time Lapse Electrical Resistivity Tomography(TLERT) was used to image and estimate the electrical properties of a small watershed in South India.This geophysical experi-

六盘山半干旱区华北落叶松林坡面土壤含水量的降雨响应

在宁夏六盘山外围半干旱区,土壤含水量是影响林木成活与生长的关键因子,需深入理解森林坡面不同坡位的土壤含水量对降雨量的响应差异。本文在宁夏六盘山叠叠沟小流域,选择一个华北落叶松人工林典型坡面,于2021年5—10月利用自动气象站和土壤水分仪连续监测降雨等气象条件和坡面土壤含水量变化,分析土壤含水量的坡位差异及对降雨量级的响应。观测期间总降水量为443.7 mm,虽然接近多年平均值,但夏季干旱严重。结果表明:(1)土壤含水量存在明显的生长季内变化,整体表现为先降低后升高的趋势,8月最低(0.112 m^(3)·m^(-3))。(2)土壤含水量存在明显的坡位差异,整体表现为:上坡[(0.191±0.044)m^(3)·m^(-3)]>中坡[(0.158±0.045)m^(3)·m^(-3)]>下坡[(0.146±0.034)m^(3)·m^(-3)],表明土壤含水量的坡位变化因处于干旱年,主要受植被蒸散耗水量大小的影响,而受坡面汇流影响不大。(3)在同一降雨量级时,因受土壤孔隙度和持水能力、林下草本截持、优先流等的影响差异,中坡的土壤含水量对降雨量增加的响应最敏感,其次是上坡,下坡最不敏感。(4)在本研究区,降雨以<10 mm的小降雨事件为主,7 mm是形成有效降雨的阈值,超过此阈值的降雨才有可能缓解0~20 cm土层土壤干旱和补给该层土壤水分。本研究有助于理解半干旱山区森林坡面的土壤含水量大小变化与分布特征,指导确定基于坡面土壤水分的植被承载力和进行林水综合管理。

干旱半干旱煤矿区土壤水分研究进展

本文重点评述了干旱半干旱煤矿区土壤水分与生态环境效应研究进展,系统总结了土壤水分运移机理与动态模拟方法。采煤塌陷会破坏土壤含水层构造并导致地下水位下降,间接改变土壤含水率空间分布特征;露天采矿与复垦过程中机械压实导致土壤孔隙数量减少,连通性减弱,土壤水分入渗受阻;土壤重构与植被重建技术能够有效改善土壤结构,缓解土壤水分流失。在未来研究中,首先应进一步丰富势能理论体系,完善数值模拟技术并引入动态指标;其次应结合干旱半干旱煤矿区环境的特殊性,加强土壤水分运移规律及其机理研究;最后应基于土壤–植被–水分间耦合关系优化调控措施,促进干旱半干旱煤矿区复垦与生态修复。

地下滴灌土壤水分分布对设施种植农田甲烷通量的影响

为优化设施土壤水分管理、挖掘固碳减排潜力,该文采用田间控制性试验,以设施农业中普遍栽培的番茄为对象,研究了不同滴灌管埋深(0、10、20、30 cm,依次记为DI、SDI10、SDI20、SDI30)土壤水分状况对土壤甲烷(CH_(4))通量变化的影响及其驱动机理.结果表明:①不同滴灌管埋深的番茄土壤CH_(4)通量呈波动变化,但总体为吸收效应.“植株+土壤”条件下,SDI20、SDI30的CH4累积吸收量分别为DI的7.12、4.11倍(P<0.05);“根系+土壤”条件下,SDI20、SDI30的CH_(4)累积吸收量分别较DI增加26.02%、89.43%(P<0.05).滴灌管埋深增加造成的土壤水分分布和水分均匀度差异对土壤CH4吸收量具显著调节作用.②滴灌管埋深显著影响根区土壤理化特性,如SDI10、SDI20、SDI30的土壤NO_(3)^(-)-N含量分别为DI的2.21、2.28、1.54倍(P<0.05),SDI10、SDI20的0~20 cm土壤充气孔隙度较DI增加14.45%、33.27%(P<0.05);滴灌管埋深增加造成的土壤理化特性改变明显提高了番茄根系分叉数,增强了根-土互作,形成了利于CH4氧化的条件,如SDI20、SDI30显著增加了CH4氧化基因K10944(pmoA-amoA)、K10945(pmoB-amoB)、K10946(pmoC-amoC)的拷贝数,而这些基因拷贝数与CH_(4)累积吸收量、根系分叉数均呈显著正相关.③CH4累积吸收量变化的路径分析表明,CH_(4)氧化基因拷贝数变化是影响CH4累积吸收量的关键因素,而滴灌管埋深变化造成的根系分叉数(R=0.77)与NH_(4)^(+)-N含量(R=0.42)的差异对CH_(4)氧化基因具有显著的直接调节效应.总体上,SDI20、SDI30通过提高根系分叉数、CH_(4)氧化基因拷贝数和果实膨大期叶片鲜质量,增强了“地面植株-根-土”交互作用,促进了土壤CH4吸收;DI、SDI10相对减弱了“地面植株-根-土”交互作用,抑制了土壤CH_(4)吸收.研究显示,滴灌管埋深通过影响土壤水分分布状况和植株生长差异调节根-土互作以及土壤CH4累积吸收量.

河套灌区垄膜沟灌模式对春玉米田水热运移及籽粒产量的影响

河套灌区降水稀少、昼夜温差大,早春温度偏低影响春玉米生长,为改善灌区春玉米水热环境,以不同覆膜与灌溉组合为研究对象,探究适宜的保墒增温和提质增效的覆膜灌溉耕作模式,为河套灌区水热资源的高效利用提供理论指导与技术支撑。试验布设4个处理:畦灌+不覆膜(CK)、畦灌+透明地膜覆盖(QB)、沟灌+透明地膜垄体覆盖(GB)、沟灌+黑色地膜垄体覆盖(GH),以探究不同覆膜灌溉方式下春玉米田土壤含水率和土壤温度变化规律、春玉米产量及水热资源利用效率。结果表明:垄膜沟灌可提高表层土壤含水率和根区储水量。播后61d,GH、GB和QB处理根区土壤储水量分别较CK增加36.01%、36.61%和21.37%,且垄膜沟灌显著高于覆膜畦灌。播后133 d,GH根区土壤储水量较CK和QB增加19.02%和17.40%。垄膜沟灌有效提高日均土壤温度,GB生育期日均土壤温度较QB和CK平均增加1.01℃和1.59℃,GH较QB和CK平均增加0.86℃和1.44℃。垄膜沟灌土壤有效积温显著高于畦灌处理,其中GB较QB和CK提高7.78%和16.70%;GH较QB提高6.26%,较CK提升14.46%。春玉米产量呈现出与百粒重结果相同的显著性差异,其中QB较CK提升16.19%,GB较QB提升13.64%,较CK提升32.04%。GB处理下水分利用效率(WUE)和土壤有效积温生产效率(TUE)较QB提升25.79%和5.41%,较CK提升45.69%和13.66%。GB可有效提升根区土壤储水量及温度,改善春玉米水热资源利用效率,提高籽粒产量。综上,建议在内蒙古河套灌区推行沟灌+透明地膜垄体覆盖技术,以提高春玉米产量及水热资源利用效率。

荒漠—绿洲过渡带典型混交灌木根区土壤含水率变化特征

土壤水分是干旱区植被生长的限制因子,研究荒漠—绿洲过渡带植被根区土壤水分时空变化对抵御沙漠化进程具有重要意义。以荒漠-绿洲过渡带3种典型混交灌木梭梭×泡泡刺(SS×PP)、泡泡刺×沙拐枣(PP×SG)、沙拐枣×梭梭(SG×SS)为研究对象,对3种典型混交灌木根区0~100 cm土层土壤进行连续采样并测定土壤含水率。结果表明:1)7-9月,3种混交灌木根区0~100 cm土层土壤含水率的变化范围依次为:梭梭×泡泡刺0.54%~2.75%、1.06%~2.41%、0.73%~4.72%;沙拐枣×梭梭0.42%~2.59%、0.96%~2.35%、0.57%~3.58%;泡泡刺×沙拐枣0.31%~2.38%、0.56%~2.33%、0.79%~3.71%。3种混交灌木在0~60 cm土层土壤含水率随深度增加而增大,60~100 cm土层各类型混交灌木土壤含水率变化逐渐趋于稳定。2)7月,0~100 cm土层混交灌木梭梭×泡泡刺的土壤含水率显著高于沙拐枣×泡泡刺,9月,20~40、60~100 cm土层混交灌木沙拐枣×梭梭的土壤含水率显著低于其他2种混交灌木类型。3)3种混交灌木土壤持水能力大小为梭梭×泡泡刺>泡泡刺×沙拐枣>沙拐枣×梭梭。研究结果为荒漠—绿洲过渡带防风固沙植被建设中植物种类的选择提供科学依据。

寒旱露天矿区土壤水分运移规律及其生态效应

为了探究寒旱露天煤矿区土壤水分运移规律及其生态效应,以位于蒙东草原的露天煤矿为研究区,开展了长时间段土壤水分观测原位试验。研究结果表明:非冻结期浅层土壤含水率主要受降水影响,冻结期土壤含水率受土壤温度影响明显;50 cm以上土壤饱和渗透系数大于150 cm/d,50 cm以下土壤饱和渗透系数仅为20 cm/d左右,表现为土壤饱和渗透系数随土壤深度的增加呈减小趋势,降水入渗形成的土壤水主要滞留在50 cm以上的植被根系作用层;区内地下水位埋深(>10 m)远超地下水补给植被的临界埋深(3.52 m),植被指数与年降水量呈正相关关系,表明土壤水是维持区内植被需水的最关键水源;冻融期土壤含水率可恢复甚至超过非冻结期的含水率水平,同时特殊的土层结构造成植被根系区的土壤持水性较好,以上2个因素对植被生长具有积极意义。研究结果可为寒旱露天煤矿区的生态环境保护与修复提供借鉴。

荒漠绿洲过渡带土壤水分空间分布特征及对植被的影响

研究荒漠绿洲过渡带土壤水分空间特征,有利于提高干旱区水资源利用率和植被恢复。连续对黑河中游荒漠绿洲过渡带6个典型群落类型样地的地表0~120 cm深度剖面的土壤水分分布进行调查,采用烘干法分析并结合18个调查样方进行土壤含水量的空间分布特征研究,揭示荒漠植被土壤水分分布特征。结果表明,1)土壤水分的变异性随着深度的增加而减小,表层土层含水量空间变异性表现为强变异,说明土壤水分不稳定,深层土壤空间变异性变现为弱变异性,说明土壤水分较稳定。2)垂直分布上,每个样地各土层的土壤含水量均随土壤深度增加呈上升—降低—上升的总体趋势,各样地土壤含水量均是表层低,深层高。3)水平空间上,土壤含水量变化范围在0.09%~22.34%,土壤含水量的均值依次为深层(60~120 cm)>上层(0~40 cm)>中层(40~60 cm),总体来看,黑河中游荒漠绿洲过渡带各层土壤含水量均处于较低水平。4)干沙层土壤含水量最低,上覆沙土土壤含水量很少且随着深度的增加而增加,下浮沙土受地下水毛管作用和蒸腾作用影响水分含量较高且随土壤深度的增加而增加。研究结果为深入理解荒漠绿洲过渡带固沙植被的天然分布提供了理论依据。

黄河河岸带不同人为干扰的土壤物理性质比较

【目的】研究人为干扰强度对黄河河岸带土壤物理性质的影响,为黄河河岸带生态系统生态恢复与调控提供科学依据。【方法】2021年10月,在黄河洛阳—郑州段选择地形地貌和地表植被覆盖相对一致的河岸带区域,依据人为踩踏程度的不同,选择3种不同干扰强度的样地类型。按照5×3网格化划分近河岸带200 m×200 m样地,共设置15个样点,系统比较分析不同人为干扰强度(轻度、中度和重度)黄河河岸带土壤容重、土壤含水率、土壤毛管持水量、土壤最大持水量、土壤最小持水量、土壤总孔隙度、土壤毛管孔隙度和土壤非毛管孔隙度等土壤物理性质的差异。【结果】①随人为干扰强度的增加,土壤容重、土壤非毛管孔隙度逐渐增加;土壤含水率先增加后减小;土壤毛管持水量、土壤最大持水量、土壤最小持水量、土壤总孔隙度与土壤毛管孔隙度逐渐减小。②土壤容重与土壤含水率、土壤毛管孔隙度呈负相关,但未达到显著水平;土壤容重与土壤毛管持水量、土壤最大持水量、土壤最小持水量、土壤总孔隙度呈极显著负相关(P<0.01),与土壤非毛管孔隙度呈极显著正相关(P<0.01)。【结论】过度的人为踩踏等干扰增加了河岸带土壤紧实度,导致土壤物理性质退化以及土壤保水和持水能力降低。

基于人工神经网络的西辽河流域根区土壤湿度估算

土壤水是衔接大气、地表、土壤和地下的水分转换和循环的核心,土壤湿度是全球气候观测系统的基本气候变量之一,在区域尺度的水分和能量交换中起着重要作用。根区土壤湿度的估算和时空变化特征的获取,对农业产量评估、洪水和干旱预测、水土保持等均具有重要意义。以西辽河流域作为研究区,基于人工神经网络,以遥感表层土壤湿度、累积降水量、累积日最高温、累积日最低温、相对湿度、日照时长、云覆盖度、风速、土壤属性、归一化植被指数、实际蒸散发量等作为解释变量,以站点实测的根区土壤湿度作为目标变量,采用2013—2018年的数据训练模型,估算研究区内2019—2020年每天的根区土壤湿度。结果表明,基于人工神经网络的根区土壤湿度估算值与站点实测根区土壤湿度之间的平均均方根误差为0.0567 m^(3)/m^(3),平均相关系数为0.6117,表明人工神经网络模型能够有效地估算西辽河流域内的根区土壤湿度。研究发现土壤湿度的变化量与降水量密切相关。

分根区交替滴灌施肥频率对土壤水氮运移及番茄产量的影响

针对目前我国设施蔬菜实际生产过程中水肥调控不合理及水肥利用效率低的问题,本文通过温室试验研究了分根区交替滴灌施肥(ADF)条件下,不同施肥频率对土壤水分养分运移及番茄产量的影响,为番茄高效水肥调控提供理论依据。试验在ADF下设3个滴灌施肥频率处理F3(3 d)、F6(6 d)、F12(12 d)和1个常规滴灌施肥处理作为对照(CK,频率为6 d)。结果表明,在0~40 cm土层,高频滴灌施肥处理(F3)相比于低频处理(F12)生育期内两年平均土壤含水量和无机氮含量分别增加了7.9%和28.3%;在40~60 cm土层,F3和F6相比于F12处理,两年平均无机氮累积量分别降低了37.8%和23.0%。与F12处理相比,F6处理两年平均番茄生物量、吸氮量和产量分别显著增加16.9%、15.2%和22.6%,而F3和F6处理之间均无显著差异。在相同施肥量和滴灌施肥频率条件下,F6处理在减少40%灌水量的同时能够保持与CK相当产量。因此,适当提高滴灌施肥频率能够促进番茄生长及产量的形成,ADF较常规滴灌施肥具有较大的节水稳产效果。本研究推荐ADF条件下6 d一次的滴灌施肥频率可作为温室番茄生产中较为高效的水肥管理措施。