农业干旱指标研究与进展

介绍了评价农业干旱的降水量指标，土壤含水量指标，作物旱情指标及综合性指标。讨论了各类指标的研究进展及其应用于农业生产中的适用性与实用性，最后对农业干旱预报及其评价指标的研究发展作了简要介绍。     

旺长期烤烟对不同程度干旱胁迫的光谱响应

基于不同时长和程度的干旱胁迫试验,采用ASD光谱仪,研究了不同干旱胁迫处理下不同基因型烤烟叶片水分含量与光谱特征的变化规律,分析不同烤烟叶片水分指标FMC(叶片相对含水量)、LEWT(叶片等效水厚度)与光谱特征参数间的相关关系,构建烤烟叶片水分指标的高光谱特征参数模型。结果表明:不同程度干旱胁迫下烤烟叶片含水量和光谱反射率均随干旱程度的加重而降低,在不同干旱时长下,FMC的变化并不明显,而LEWT对其较为敏感,说明不同干旱胁迫处理间EWT的差异要比FMC显著,不同基因型烤烟品种表现一致,表明LEWT比FMC更适合反映旺长期烤烟叶片水分状况。利用光谱参数建立FMC和LEWT的一元及多元线性模型和BP神经网络模型中,均以BP神经模型网络模型效果最好,其模型R2(决定系数)分别为0.8650、0.9464,RMSE(均方根误差)分别达到0.0049、0.0047,表明模型的精度和稳定性均较好。     

红壤区夏玉米生长对土壤穿透阻力的响应

为寻求有效措施改善土壤穿透阻力,缓解季节性干旱对南方红壤地区农业生产的影响,通过室内3个土壤容重处理(1.1、1.3 g·cm~(-3)和1.5 g·cm~(-3))模拟初始土壤阻力,及大田4种耕作措施(深耕D、常规耕作C、免耕N和压实P)调控土壤阻力,通过盆栽与大田小区试验研究了红壤穿透阻力对玉米根系、植株生长及产量的影响。结果显示,轻旱至中旱情况下,玉米生长对红壤穿透阻力胁迫响应强烈。根长、表面积及根系体积表现为D1.1D1.3D1.5,根径则与之相反;地上部指标和产量为DCNP;除根径以外的根系形态指标、地上部生长指标和产量均与土壤穿透阻力呈显著负相关,且深耕的玉米生长情况和产量均显著高于免耕和压实。红壤穿透阻力改变了玉米根系生长状况,限制植株生长从而影响产量形成;红壤阻力每增加1.0 MPa,籽粒产量将减少1 787.1 kg·hm~(-2)。对于红粘土红壤,深耕能够明显降低土壤穿透阻力减轻干旱影响;而免耕的土壤阻力高,既直接胁迫作物生长,亦不利于缓解季节性干旱。     

不同时间尺度条件植被温度指数干旱监测方法的适用性分析

以陕西省关中平原为研究区域,选取2003—2013年3—5月的Aqua-MODIS遥感数据、降水量和土壤含水量数据,探究10 d、16 d、32 d和48 d时间尺度条件植被温度指数(VTCI)干旱监测方法的适用性。结果表明:随着时间尺度增大,VTCI与降水量和土壤含水量的相关性均逐渐减小,说明VTCI干旱监测方法的适用性随时间尺度的增大而减小,且48 d时间尺度VTCI不适用于监测某一地区的受旱程度。不同时间尺度VTCI干旱监测结果的对比分析表明,旬尺度VTCI干旱监测的准确性最高。     

埋深对红壤透水砼渗灌水分运移规律的影响

文中为探索一种新型渗灌灌水器(多孔砼灌水器)在红壤内水分运动规律，研究灌水器不同埋深对入渗效果的影响情况。通过土箱试验研究不同埋深条件下透水砼渗灌入渗特性、湿润锋推移过程，并采用模型进行拟合。结果表明，透水砼渗灌入渗能力随着灌水器埋深的增加而增强，湿润体的形状也由径向转为垂向半椭球型，入渗体体积亦随埋深的增大而变大。结论证明，湿润锋的运移距离与灌水器埋深之间符合幂函数关系(NSE>0.98);模拟值与实测值对比分析认为，Philip模型和Kostiakov模型对累积入渗量的模拟精度均为较高水平，表证模型精度的NSE>0.99、RMSE和ME均低于1,且接近于0;HYDRUS-2D对湿润锋变化和湿润体内含水量模拟可靠性较好，模拟精度受到埋深和入渗时间的影响。     

基于水分亏缺指数的北疆春小麦不同生育阶段干旱时空特征

基于水分亏缺指数模型，结合新疆历史干旱资料记载，对比分析典型年份干旱指数，确定北疆春小麦干旱等级指标，利用ArcGIS探究1986—2016年北疆春小麦各生育阶段干旱强度、干旱站次比的年际变化规律以及干旱频率的时空分布特征。结果表明：除春小麦营养生长和生殖生长并进阶段干旱站次比呈微弱增大趋势（0.355%·10a^-1），其余生长阶段干旱强度和干旱站次比均呈下降趋势；重旱和特旱在春小麦营养生长和生殖生长并进阶段发生频率最高（主要集中在50.00%~68.00%，0~3.87%），轻旱和中旱在春小麦生殖生长阶段发生频率最高（主要集中在12.00%~25.00%，12.91%~61.27%）；春小麦营养生长阶段，北疆北部地区重旱发生频率较其他地区高（主要集中在39.36%~54.19%），春小麦营养生长和生殖生长并进阶段，北疆东北部地区重旱和特旱发生频率更高（主要集中在67.72%~83.84%，7.74%~9.67%），春小麦生殖生长阶段，北疆西南部地区重旱发生频率较其他地区重旱频率更高（主要集中在46.44%~61.92%）；北疆地区在春小麦生长的3个生育阶段，生殖生长阶段中旱发生频率最高（主要集中在41.93%~51.6%），其余两个时期重旱发生频率均高于其他等级干旱发生频率（主要集中在39.36%~54.19%，51.61%~67.72%），而特旱发生频率均最低（主要集中在0~3%）。     

基于多元逐步回归分析的葡萄园干旱监测模型

为明确葡萄园区干旱评价标准，制定了一种具有区域适用性的干旱指数，通过在渭南市临渭区葡萄研究所葡萄试验田进行干旱胁迫对比试验，得出一种结合植物生长图像与环境要素的干旱监测模型；使用逐步回归分析法，计算出土壤湿度与众多影响因素间的关系，得到干旱监测模型。试验结果表明：回归方程的确定系数（R-square）可达0.91，模型精确，拟合效果较好。搭建了一个干旱监测与预警平台，可以实时监控作物的生长状况，为精准灌溉提供决策。     

干旱半干旱区土壤含水量定量反演技术研究

为系统地研究干旱半干旱区土壤含水量的反演方法,比较了目前常用的几种高光谱影像土壤含水量反演技术。结果表明:采用EO-1 Hyperion第149波段和197波段构建的光谱特征空间模型与土壤含水量值之间的R2为0.7093,两者存在良好的负相关性;土壤含水量热惯量反演模型整体拟合的R2为0.6149,与SMS拟合结果相比,效果不理想;回归分析模型中,对数变换光谱回归最优,R2值为0.6843。综合分析后,认为光谱特征空间模型对研究区土壤含水量的估测效果最佳。文中研究旨在为干旱半干旱区土壤含水量的更深入研究提供参考。     

宁夏六盘山区地面雨滴谱特征统计分析

利用2020—2021年六盘山区58次降雨过程不同站点的雨滴谱数据，对层状云、对流云、积层混合云三类降雨的微物理参量、雨滴谱平均特征，以及Gamma分布参数等进行了分析。结果表明：(1)同一站点的各微物理参量以及特征直径均值表现为：对流云>积层混合云>层状云；在层状云和积层混合云中，平均直径D_ave、众数直径D_mode表现为山腰大于山顶和山底，随着东、西坡两侧海拔高度的升高，其最大直径D_max、质量加权平均直径D_m、雨强R、雷达反射率Z、液态含水量Q逐渐增大；(2)层状云和积层混合云小雨滴对雨强和数浓度的贡献均为最大，对流云小雨滴对数浓度贡献最大，而中等雨滴对雨强的贡献最大；(3)Gamma分布的参数N₀(阶距参数)、μ(形状参数)、λ(斜率参数)随着海拔高度的升高而减小，μ-λ拟合曲线的斜率与降水类型密切相关；(4)山顶站点雨滴粒子数浓度N_w较山脚站点有所减小，而平均尺度D_m增大；(5)西北气流型的雨滴谱各特征直径参量及...     

北方地区干旱变化趋势分析

以气象干旱给农业带来的危害为出发点，对我国东北、华北、西北区15个省（市、自治区）建国以来的历史受旱面积、成灾面积、受旱率、成灾率等进行了分析，结果表明，50－90年代，干旱对农业的危害程度呈增加趋势，东北区尤为明显，受旱率增大4．7倍，成灾率增大3．8倍。研究结果还表明，灌溉对减轻旱灾损失起着重要作用，旱灾发生频率、受旱率和成灾率都随灌溉率的增加而减小。     

Dielectric properties of saline soil based on a modified Dobson dielectric model

Soil salinization is a major concern for agricultural development in arid areas. In this paper, a modified Dobson dielectric model was applied to simulate the dielectric constant of saline soil in the Ugan-Kuqa river delta oasis of Xinjiang Uygur autonomous region, northwestern China. The model performance was examined through analyzing the influences of its parameters on the soil dielectric constant and the relationship between radar backscattering coefficient and the dielectric constant of saline soil. The results of the study indicate that:(1) The real part of the soil dielectric constant is affected by soil water content at low radar frequencies; the imaginary part is closely related with both the soil water content and soil salt content.(2) The soil water and salt contents are related with the coefficient of dialectical loss, which is consistent with the natural conditions of saline soil in arid areas and provides valuable references for the study of soil dielectric properties.(3) The changes of soil water content and soil salt content have instant influences on the dielectric constant of saline soil. Subsequently, the radar backscattering coefficient is affected to respond to the dielectric constant of saline soil. The radar backscattering coefficient is most responsible to the radar's cross polarization pattern with a correlation coefficient of R2=0.75. This study provides a potential method to monitor soil salinization and soil water content by using a soil dielectric model and radar techniques.     

容重及含水率对土壤电导率的影响研究

土壤电导率能够间接反映田间养分或盐分含量,通过监测土壤电导率可以掌握土壤养分或盐分运移和利用情况。本文通过2种土壤容重、5种含水率条件下土柱入渗试验,利用5TE传感器对土壤体积含水率、体积电导率、温度等参数进行连续监测,分析容重及含水率对土壤电导率的影响。结果表明：在入渗过程中,含水率和电导率均先增大后逐渐减小,最后趋于平缓;电导率开始减小的时间较含水率开始减小的时间略有提前;当体积含水率一定时,孔隙水电导率随体积电导率的增加基本呈线性增加;随含水率的增大,孔隙水电导率随体积水电导率增大的速率变慢;当体积电导率一定时,随着含水率的增加,孔隙水电导率逐渐减小,容重为1.35 g·cm^-3时减幅为9.52%～55.51%,容重为1.3 g·cm^-3时减幅为9.72%～54.62%;孔隙水电导率一定时,体积电导率随含水率的增加而增大,容重为1.35 g·cm^-3时增幅为10.51%～124.75%,容重为1.3 g·cm^-3时增幅为10.76%～120.35%。对于2种容重情况,相同含水率下孔隙水电导率与...     

基于HYDRUS软件的植物混掺土壤水分特征曲线分析

为探求植物混掺对土壤持水性产生的影响,以甘肃景泰地区土壤为试验材料,设置1％玉米芯、1％玉米叶、3％玉米芯、3％玉米叶等不同比例、不同秸秆混掺物4种处理,采用离心机法测定土壤水分特性曲线,同时利用HYDRUS软件进行模拟计算。结果表明,在相同吸力下,相同混掺物处理,混掺比为3％的土壤体积含水率高于混掺比为1％的土壤;相同混掺比处理,混掺玉米叶的土壤体积含水率高于混掺玉米芯的土壤,且混掺处理后土壤体积含水率均高于纯土;不同土壤水分特征曲线的模型拟合分析表明,不同处理的最优拟合模型均为Van Genucht-en模型。研究结果可为探索该地区植物混掺条件下土壤水盐运移规律提供一定参考。     

Evaluating the soil evaporation loss rate in a gravel-sand mulching environment based on stable isotopes data

In order to cope with drought and water shortages, the working people in the arid areas of Northwest China have developed a drought-resistant planting method, namely, gravel-sand mulching, after long-term agricultural practices. To understand the effects of gravel-sand mulching on soil water evaporation, we selected Baifeng peach (Amygdalus persica L.) orchards in Northwest China as the experimental field in 2021. Based on continuously collected soil water stable isotopes data, we evaluated the soil evaporation loss rate in a gravel-sand mulching environment using the line-conditioned excess (lc-excess) coupled Rayleigh fractionation model and Craig-Gordon model. The results show that the average soil water content in the plots with gravel-sand mulching is 1.86% higher than that without gravel-sand mulching. The monthly variation of the soil water content is smaller in the plots with gravel-sand mulching than that without gravel-sand mulching. Moreover, the average lc-excess value in the plots without gravel-sand mulching is smaller. In addition, the soil evaporation loss rate in the plots with gravel-sand mulching is lower than that in the plots without gravel-sand mulching. The lc-excess value was negative for both the plots with and without gravel-sand mulching, and it has good correlation with relative humidity, average temperature, input water content, and soil water content. The effect of gravel-sand mulching on soil evaporation is most prominent in August. Compared with the evaporation data of similar environments in the literature, the lc-excess coupled Rayleigh fractionation model is better. Stable isotopes evidence shows that gravel-sand mulching can effectively reduce soil water evaporation, which provides a theoretical basis for agricultural water management and optimization of water-saving methods in arid areas.     

气象、农业干旱指标综述

介绍了以降水量统计特征作为指标和以降水量、气温统计特征作为指标的气象干旱指标,以土壤含水量、作物旱情、作物需水量、供需水比例、作物水分综合统计特征为指标的农业干旱指标.列出气象、农业干旱指标计算公式,介绍计算方法和干旱指标的详细等级标准,并对各指标计算所需统计资料观测、收集的难易程度,各指标的优缺点、适用性及其适用区域范围评述,为干旱的监测、评估、预警和研究提供依据.     

不同流量对滴灌土壤湿润体特征的影响

在米脂山地微灌枣树示范基地进行原状土的滴灌入渗试验,研究了不同流量、不同灌水历时条件下,地表滴灌湿润体特征值的变化规律及滴灌结束时的水分分布规律。结果表明:湿润体的水平和垂直扩散距离均与时间有显著的幂函数关系,相关系数均大于0.99;湿润体的体积及湿润体内土壤含水率的分布同时受滴头流量和灌水量的控制,相同灌水量情况下,湿润体体积随滴头流量的增加而变小,平均含水率变大;并且建立了预测湿润体特征值和湿润体体积的经验模型。     

Index-based assessment of agricultural drought in a semi-arid region of Inner Mongolia, China

Agricultural drought is a type of natural disaster that seriously impacts food security.Because the relationships among short-term rainfall,soil moisture,and crop growth are complex,accurate identification of a drought situation is difficult.In this study,using a conceptual model based on the relationship between water deficit and crop yield reduction,we evaluated the drought process in a typical rainfed agricultural region,Hailar county in Inner Mongolia autonomous region,China.To quantify drought,we used the precipitation-based Standardized Precipitation Index(SPI),the soil moisture-based Crop Moisture Index(CMI),as well as the Normalized Difference Vegetation Index(NDVI).Correlation analysis was conducted to examine the relationships between dekad-scale drought indices during the growing season(May–September)and final yield,according to data collection from 2000 to 2010.The results show that crop yield has positive relationships with CMI from mid-June to mid-July and with the NDVI anomaly throughout July,but no correlation with SPI.Further analysis of the relationship between the two drought indices shows that the NDVI anomaly responds to CMI with a lag of 1 dekad,particularly in July.To examine the feasibility of employing these indices for monitoring the drought process at a dekad time scale,a detailed drought assessment was carried out for selected drought years.The results confirm that the soil moisture-based vegetation indices in the late vegetative to early reproductive growth stages can be used to detect agricultural drought in the study area.Therefore,the framework of the conceptual model developed for drought monitoring can be employed to support drought mitigation in the rainfed agricultural region of Northern China.     

添加γ-聚谷氨酸条件下Philip模型与Green-Ampt入渗模型的对比分析

干旱加剧及土壤退化严重,使新型保水剂γ-聚谷氨酸(γ-PGA)的应用在农田节水灌溉中开始暂露头角。基于室内垂直一维入渗试验,在分析了γ-PGA对土壤水分入渗能力的影响的同时还对Philip模型和Green-Ampt入渗模型进行对比分析。结果表明:与未施加聚谷氨酸的处理(对照组)相比,随着γ-PGA施量的增加,累积入渗量和入渗率均呈单调递减趋势;两个入渗模型的拟合结果显示:Philip公式中,吸渗率呈减小趋势,Green-Ampt公式中,饱和导水率、饱和导水率与土壤水吸力的乘积都呈减小趋势,但土壤水吸力无明显变化。Philip模型与Green-Ampt入渗模型的对比分析结果表明:利用模型参数互推关系计算的Philip模型计算参数与拟合参数的一致性较好,而Green-Ampt模型的计算参数与拟合参数的一致性较差;利用Philip模型计算参数计算的累积入渗量与实测累积入渗量之间的吻合程度高,均方根误差小于0.5,而利用Green-Ampt模型计算参数计算的累积入渗量与实测累积入渗量之间的吻合程度较差,均方根差均大于0.5。说明在添加保水剂的条件下采用Philip入渗模型确定入渗参数时较为精确。     

应用叶绿素荧光技术快速预警乌鲁木齐典型农作物干旱胁迫

通过叶绿素荧光技术,分析了黄瓜、番茄、茄子、辣椒4种乌鲁木齐典型农作物幼苗在干旱胁迫过程中光系统（PSⅠ、PSⅡ）活性的变化特点,同时分析了土壤含水量和叶绿素荧光参数之间的相关关系。结果表明：在干旱胁迫下,4种农作物幼苗的光系统活力受到土壤水分含量变化的影响。Fv/Fm、Y(II)（实际量子产量）随土壤水分含量降低逐渐受到抑制,在土壤失水严重时显著降低。Y(NO)（非调节性能量耗散的量子产量）在干旱胁迫过程中逐渐增加。PSⅡ反应中心潜在活性Fv/F0在指示干旱胁迫危害和鉴别不同植物耐旱性时具有一定优势。通过土壤含水量和叶绿素荧光参数的相关分析发现,土壤含水量与Fv/Fm、Fv/F0、Y(II)和Y(ND)（非光化学能量耗散的量子产量）等呈显著正相关关系,与Y(NO)和Y(I)呈显著负相关关系。叶绿素荧光参数可以反映植株在干旱胁迫下的生理状态,也可以作为土壤水分含量的指示物,对农作物幼苗的干旱胁迫程度做出快速预警。同时,通过干旱胁迫下叶绿素荧光参数的对比,还发现幼苗之间的耐旱性差异,茄子抗旱能力优于其他3种农作物幼苗,黄瓜和番茄幼苗耐旱能力相似,辣椒的耐旱性比其他3种农作物幼苗差。     

A new method of searching for concealed Au deposits by using the spectrum of arid desert plant species

With the increase of exploration depth, it is more and more difficult to find Au deposits. Due to the limitation of time and cost, traditional geological exploration methods are becoming increasingly difficult to be effectively applied. Thus, new methods and ideas are urgently needed. This study assessed the feasibility and effectiveness of using hyperspectral technology to prospect for hidden Au deposits. For this purpose, 48 plant (Seriphidium terrae-albae) and soil (aeolian gravel desert soil) samples were first collected along a sampling line that traverses an Au mineralization alteration zone (Aketasi mining region in an arid region of China) and were used to obtain soil Au contents by a chemical analysis method and the reflectance spectra of plants obtained with an Analytical Spectral Device (ASD) FieldSpec3 spectrometer. Then, the corresponding relationship between the soil Au content anomaly and concealed Au deposits was investigated. Additionally, the characteristic bands were selected from plant spectra using four different methods, namely, genetic algorithm (GA), stepwise regression analysis (STE), competitive adaptive reweighted sampling (CARS), and correlation coefficient method (CC), and were then input into the partial least squares (PLS) method to construct a model for estimating the soil Au content. Finally, the quantitative relationship between the soil Au content and the 15 different plant transformation spectra was established using the PLS method. The results were compared with those of a model based on the full spectrum. The results obtained in this study indicate that the location of concealed Au deposits can be predicted based on soil geochemical anomaly information, and it is feasible and effective to use the full plant spectrum and PLS method to estimate the Au content in the soil. The cross-validated coefficient of determination (R²) and the ratio of the performance to deviation (RPD) between the predicted value and the measured value reached the maximum of 0.8218 and 2.37, respectively, with a minimum value of 6.56 μg/kg for the root-mean-squared error (RMSE) in the full spectrum model. However, in the process of modeling, it is crucial to select the appropriate transformation spectrum as the input parameter for the PLS method. Compared with the GA, STE, and CC methods, CARS was the superior characteristic band screening method based on the accuracy and complexity of the model. When modeling with characteristic bands, the highest accuracy, R² of 0.8016, RMSE of 7.07 μg/kg, and RPD of 2.20 were obtained when 56 characteristic bands were selected from the transformed spectra (1/lnR)' (where it represents the first derivative of the reciprocal of the logarithmic spectrum) of sampled plants using the CARS method and were input into the PLS method to construct an inversion model of the Au content in the soil. Thus, characteristic bands can replace the full spectrum when constructing a model for estimating the soil Au content. Finally, this study proposes a method of using plant spectra to find concealed Au deposits, which may have promising application prospects because of its simplicity and rapidity.