Quantitatively characterizing sandy soil structure altered by MICP using multi-level thresholding segmentation algorithm

The influences of biological,chemical,and flow processes on soil structure through microbially induced carbonate precipitation(MICP)are not yet fully understood.In this study,we use a multi-level thresholding segmentation algorithm,genetic algorithm(GA)enhanced Kapur entropy(KE)(GAE-KE),to accomplish quantitative characterization of sandy soil structure altered by MICP cementation.A sandy soil sample was treated using MICP method and scanned by the synchrotron radiation(SR)micro-CT with a resolution of 6.5 mm.After validation,tri-level thresholding segmentation using GAE-KE successfully separated the precipitated calcium carbonate crystals from sand particles and pores.The spatial distributions of porosity,pore structure parameters,and flow characteristics were calculated for quantitative characterization.The results offer pore-scale insights into the MICP treatment effect,and the quantitative understanding confirms the feasibility of the GAE-KE multi-level thresholding segmentation algorithm.

A study of the soil water potential threshold values to trigger irrigation of ‘Shimizu Hakuto’ peach at pivotal fruit developmental stages

Water management is an important practice that affects fruit size and quality.Effective implementation of irrigation scheduling requires knowledge of the appropriate indicators and thresholds,which are established manly based on the effects of water deficits on final fruit quality.Few studies have focused on the real-time effects of water status on fruit and shoot growth.To establish soil water potential (ψ_(soil)) thresholds to trigger irrigation of peach at pivotal fruit developmental stages,photogrammetry,^(13)C labelling,and other techniques were used in this study to investigate real-time changes in stem diameter,fruit projected area,net leaf photosynthetic rate (P_(n)),and allocation of photoassimilates to fruit under soil water potential conditions ranging from saturation to stress in 6-year-old Shimizu hakuto’peach.Stem growth,fruit growth,and P_n exhibited gradually decreasing sensitivity to water deficits during fruit developmental stages I,II,and III.Stem diameter growth was significantly inhibited whenψ_(soil)dropped to-8.5,-7.6,and-5.4 k Pa,respectively.Fruit growth rate was low,reaching zero when theψ_(soil)was-9.0 to-23.1,-14.9 to-21.4,and-16.5 to-23.3 k Pa,respectively,and P_ndecreased significantly when theψ_(soil)reached-24.2,-22.7,and-20.4 kPa,respectively.In addition,more photoassimilates were allocated to fruit under moderateψ_(soil)conditions (-10.1 to-17.0 k Pa) than under otherψ_(soil)values.Our results revealed threeψ_(soil)thresholds,-10.0,-15.0,and-15.0 kPa,suitable for triggering irrigation during stages I,II,and III,respectively.These thresholds can be helpful for controlling excessive tree vigor,maintaining rapid fruit growth and leaf photosynthesis,and promoting the allocation of more photoassimilates to fruit.

Antecedent Precipitation Index to Estimate Soil Moisture and Correlate as a Triggering Process in the Occurrence of Landslides

Landslides are highly dangerous phenomena that occur in different parts of the world and pose significant threats to human populations. Intense rainfall events are the main triggering process for landslides in urbanized slope regions, especially those considered high-risk areas. Various other factors contribute to the process;thus, it is essential to analyze the causes of such incidents in all possible ways. Soil moisture plays a critical role in the Earth’s surface-atmosphere interaction systems;hence, measurements and their estimations are crucial for understanding all processes involved in the water balance, especially those related to landslides. Soil moisture can be estimated from in-situ measurements using different sensors and techniques, satellite remote sensing, hydrological modeling, and indicators to index moisture conditions. Antecedent soil moisture can significantly impact runoff for the same rainfall event in a watershed. The Antecedent Precipitation Index (API) or “retained rainfall,” along with the antecedent moisture condition from the Natural Resources Conservation Service, is generally applied to estimate runoff in watersheds where data is limited or unavailable. This work aims to explore API in estimating soil moisture and establish thresholds based on landslide occurrences. The estimated soil moisture will be compared and calibrated using measurements obtained through multisensor capacitance probes installed in a high-risk area located in the mountainous region of Campos do Jordão municipality, São Paulo, Brazil. The API used in the calculation has been modified, where the recession coefficient depends on air temperature variability as well as the climatological mean temperature, which can be considered as losses in the water balance due to evapotranspiration. Once the API is calibrated, it will be used to extrapolate to the entire watershed and consequently estimate soil moisture. By utilizing recorded mass movements and comparing them with API and soil moisture, it will be possible to determine thresholds, thus enabling anticipation of landslide occurrences.

Derivation of soil Pb/Cd/As thresholds for safety of vegetable planting: A case study for pakchoi in Guangdong Province,China

Regional guidelines for soil heavy metals,in conjunction with specific crops,are proposed to better assess soil environmental quality.In this study,large amounts of soils with different levels of Pb/Cd/As pollution were collected in Guangdong Province,China,to carry out a pot experiment,which was closer to the actual situation and properties of the heavy metal contaminated soils.Taking the widely planted vegetable pakchoi as the research object,we analyzed the correlations between the Pb/Cd/As concentrations in pakchoi and the total or available soil Pb/Cd/As concentrations and established their optimal regression equations.And then,the total and available soil Pb/Cd/As thresholds for pakchoi were calculated according to the allowable Pb/Cd/As limits in pakchoi and were compared with the current soil assessment standards.Furthermore,a lot of paired vegetable-soil samples in field were collected and their pollution situations were assessed by both the current limit thresholds and the calculated thresholds.Obviously,it was more consistent to assess the Cd and As pollution situation of the vegetable and soil samples with the calculated soil thresholds than the current soil assessment thresholds.It further proved that it was necessary to explore the soil heavy metal thresholds for safety of vegetable in specific regions,which would be more scientific and practical to guide safety production of local agricultural products and effective utilization of soil resources.

Strain-threshold- and frequency-dependent seismic simulation of nonlinear soils

A one-dimensional equivalent linear method （EQL） is widely used in estimating seismic ground response. For this method, the shear modulus and damping ratio of inelastic soil are supposed to be frequency independent. However, historical earthquake records and laboratory test results indicate that nonlinear soil behavior is frequency- dependent. Several frequency-dependent equivalent linear methods （FDEQL） related to the Fourier amplitude of shear strain time history have been developed to take into account the frequency-dependent soil behavior. Furthermore, the shear strain threshold plays an important role in soil behavior. For shear strains below the elastic shear strain threshold, soil behaves essentially as a linear elastic mate- rial. To consider the effect of elastic-shear-strain-threshold- and frequency-dependent soil behavior on wave propaga- tion, the shear-strain-threshold- and frequency-dependent equivalent linear method （TFDEQL） is proposed. A series of analyses is implemented for EQL, FDEQL, and TFDEQL methods. Results show that elastic-shear-strain-threshold- and frequency-dependent soil behavior plays a great influence on the computed site response, especially for the high- frequency band. Also, the effect of elastic-strain-threshold- and frequency-dependent soil behavior on the site response is analyzed from relatively weak to strong input motion, and results show that the effect is more pronounced as input motion goes from weak to strong.

Determining thresholds of low soil temperature for ecophysiological traits of black spruce and jack pine seedlings

Many studies have estimated approximately ranges of thresholds of low soil temperature in the growth and ecophysi-ological traits of trees, but difficultly determined the exact values. To resolve the problem, black spruce （Picea mariana） and jack pine （Pinus banksiana） seedlings were exposed to 5, 10, 15, 20, 25, 30 and 35℃ soil temperature in greenhouses. After 90 days of the treatment, net photosynthetic rate （A）, stomatal conductance （gs）, transpiration rate （E）, water use efficiency （WUE） and specific leaf area （SLA） were measured. This study showed that all the traits had an asymmetrical peak relationship with changing soil temperature, the relationship was well simulated using a cubic curvilinear model, and the exact thresholds could be derived from the second derivative of the model. The results revealed that the thresholds varied among ecophysiological traits and between tree species. In black spruce, the thresholds were 14.1, 14.7, 10.7, 14.4 and 16.2℃ forA, gs, E, WUE and SLA; 15.4, 10.4, 14.7, 16.9 and 10.5℃ for the corresponding traits in jack pine. The lowest thresholds of E in black spruce and gs in jack pine were an indicator representing the minimum requirement of soil temperature for the regular processes of ecophysiology. The highest thresholds of SLA in black spruce and WUE in jack pine suggest they are the most sensitive to decreasing soil temperature and may play an important role in the acclimation. The averaged thresholds were at 14.0 and 13.6℃ for black spruce and jack pine, suggesting that the sensitivity of both species to low soil temperature was quite close.

Environmental Threshold of Phosphorus Infiltration in Red Soil under Different Land Use Patterns

The risk of soil phosphorus leaching increases in basin regions in light of large-scale use of phosphorus fertilizers because of agricultural modernization. In this study, we conducted an earth pillar simulation test on the infiltration threshold of red soil, Vaseline-coated PVC pipe, intact soil core, fine sand, and nylon filter was used for Penetration test, which covers the largest area of the Dianchi Lake Basin in China. Results showed that: 1) The contents of the total available phosphorus in algae (NaOH-P) and dissolved labile phosphorus (CaCl2-P) in red soil were consistent with the content of available phosphorus (Olsen-P) under different use patterns manifested by the law of greenhouse > open field > grassland. Grassland had the highest phosphorus sorption index (PSI), followed by the greenhouse and then by the open field. 2) The leachate under the same use pattern had the characteristics of total phosphorus (TP) > particle phosphorus (PP) > total dissolved phosphorus (TDP) > dissolved organic phosphorus (DOP) > molybdate reactive phosphorus (MRP). The TP contents in the leachates of grassland, greenhouse, and open field were 0.46, 0.61, and 0.49 mg/L, respectively. DOP, TDP, PP, and MRP had similar contents, and their distributions in the three land types were consistent with that of TP. 3) Olsen-P had a significant correlation with TP, TDP, PP, and DOP in the leachates. Olsen-P of <40 mg/kg and PSI of >50 slightly influenced eutrophication. Moreover, Olsen-P of >40 and <70.90 mg/kg and PSI of >40 had minimal influence on the environment. Olsen-P of >70.90 mg/kg and PSI of <30 significantly influenced eutrophication in Dianchi Lake Basin. 4) When Olsen-P was >26.09 mg/kg, the TP content in the leachate increased sharply.

Critical thresholds for stage division of water erosion process in different ridge systems in mollisol region of Northeast China

Extreme rainfall events on a slope under ridge tillage systems cause concentrated stream soil loss.To analyse the critical thresholds for different stages of water erosion process of ridge systems,simulated rainfall-erosion experiments for the contour wide ridge(CWR),contour narrow ridge(CNR),longitudinal wide ridge(LWR),and longitudinal narrow ridge(LNR)were conducted under four rainfall intensities,with slope gradients of 3°and 5°.For the runoff event,the runoff depth order was LNR>LWR>CWR>CNR;the soil loss order was CNR>LNR>CWR>LWR.The product of slope factor(S)and rainfall erosivity(R)or runoff depth(D),can be adopted as critical thresholds for different stages of runoff and soil erosion process.For the longitudinal ridge systems,R values were provided for LWR and LNR and were the beginning of sheet flow,whereas the product of rainfall erosivity and slope factor(RS)values were provided for LWR and LNR as the beginning of the accelerated concentrated flow.For the contour ridge systems,R values were provided for CWR and CNR as critical thresholds for the beginning of overflow.The product of runoff depth and slope factor(DS)values were 9.98 and 7.73 mm for CWR and CNR,respectively,and were critical thresholds for the beginning of ridge failure;the DS values were 18.45 and 12.75 mm for CWR and CNR,respectively,and were critical thresholds for the beginning of the formation of ephemeral gully erosion.The critical thresholds can distinguish different stages of soil erosion process modelling.

不同土地利用方式下的场地土壤环境容量评价

从土壤功能和环境风险的角度出发,结合我国具体实际,对场地土壤的不同土地利用方式进行分类,以人体健康、地下水安全、土壤生物为敏感受体,研究在不同土地利用方式下基于不同敏感受体的综合土壤环境阈值计算方法,构建场地土壤环境容量的评价方法.在此基础上,以重金属Cd为模式污染物,计算了我国红壤区不同土地利用方式下的土壤环境容量,对场地土壤环境容量的评价方法进行验证.公园用地、居住用地、工矿用地和商服用地的土壤Cd环境容量分别为11.68kg/hm^(2)、28.89kg/hm^(2)、40.84kg/hm^(2)和40.84kg/hm^(2).本研究为基于不同敏感受体的场地土壤的环境阈值和环境容量评估提供了参考方法和案例,为场地土壤环境容量的评价奠定科学基础,对提升我国场地土壤的环境管理水平具有重要意义.

土壤环境基准的科学问题与研究方法:以Cd为例

土壤环境基准是土壤环境质量标准制定的科学依据和基础。环境基准是土壤环境保护研究的前沿领域,涉及土壤环境化学、环境毒理学、生物学和风险评估等多学科交叉与基础性科学问题,了解和解决其所涉及的这些科学问题,是土壤环境基准研究的前提。本文针对土壤环境基准研究中影响重金属毒性阈值的非生物因子、生物因子、剂量效应关系测定中等几个关键科学问题进行了阐述,包括土壤老化因子与淋洗因子的矫正,低剂量刺激效应拟合及毒性数据归一化方法等,最后以农田土壤Cd为例,推导出不同性质土壤中Cd环境基准(HC_(5))及其与土壤性质的连续性分布曲线方程(LogHC_(5)=0.132pH+0.083OC+0.008CEC-1.448),以期为农田土壤环境指标基准的研究提供参考与借鉴。

区域土特征函数:收敛性

无论从一个地区内建立N-s_(v)关系曲线的工程应用角度还是作为区域土特征理论的必要组成部分,构建科学的N-v_(s)函数所需的数组量都是重要问题,但以往研究为空白。采用实测数据的随机分析,研究不同样本数量下N-v_(s)特征函数的稳定性和收敛性,并提出构建不同精度N-v_(s)特征函数的数组阈值。实测数据来源于4个国家9个地区,共11个工况,对此分别进行随机分析的结果表明,随样本数量增加,N-v_(s)特征函数具有稳定性与收敛性。研究表明,一个地区内取N-v_(s)数组超过50,100,200和800,则可分别得到变异系数小于0.2,0.15,0.10和0.05的N-s_(v)特征函数。

不同土地利用方式下文昌滨海贝屑沙土磷素组成与淋溶特性

土壤磷素(P)是作物必需的营养元素之一,也是农业生产中重要的养分限制因子,还是水体富营养化的重要污染源。以文昌滨海贝屑沙土为研究对象,应用石灰性土壤无机磷分级方法研究其形态组成,采用淋洗法评价其磷淋溶特性。试验结果表明:文昌滨海贝屑沙土磷素形态组成以Ca10-P(45.78%)为主,O-P(26.67%)与Ca8-P(11.27%)次之,Ca_(2)-P(2.97%)、Al-P(4.70%)和Fe-P(8.60%)的含量较少;耕地土壤Ca_(2)-P(28.35 mg/kg)和Ca8-P(93.74 mg/kg)含量显著高于林地土壤的Ca_(2)-P(3.95 mg/kg)和Ca8-P(42.31 mg/kg)含量;瓜菜和叶菜地土壤Ca_(2)-P和Ca8-P含量显著高于其他植被类型土壤的含量;土壤平均磷淋失量为2.92 mg/kg,占土壤总磷量的0.32%,占土壤有效磷(Olsen-P)含量的10.26%,Olsen-P淋溶阈值为51.13 mg/kg。

基于PLSR和LSSVM模型的土壤水分高光谱反演

为对地下采矿扰动区表层土壤水分进行反演,以大柳塔煤矿52501工作面为例,利用无人机搭载成像光谱仪获取高光谱影像,对获取的光谱数据进行对数、倒数对数、一阶和包络线去除变换,结合地面采集的128个土壤水分数据,基于偏最小二乘回归(PLSR)和最小二乘支持向量机(LSSVM)构建土壤水分预测模型并验证其预测精度。结果表明,基于一阶变换的PLSR模型和LSSVM模型预测精度相对较好,一阶变换的PLSR模型建模集R^(2)_(c)和预测集R^(2)_(p)分别为0.7021和0.6405,均方根误差RMSE_(c)和RMSE_(p)分别为1.6384%和1.1034%,相对分析误差RPD_(p)为1.7263;一阶变换的LSSVM模型建模集R^(2)_(c)和预测集R^(2)_(p)分别为0.8125和0.5979,均方根误差RMSE_(c)和RMSE_(p)分别为1.2755%和1.3459%,相对分析误差RPD_(P)为1.6323。最终基于PLSR和LSSVM模型完成了土壤水分的制图,实现了土壤水分的空间预测,为该研究区植被引导修复中土壤水分精准提升提供了空间数据支持。

高肥力土壤下马铃薯磷肥利用及投入阈值研究

为探究农田磷肥投入阈值,保证马铃薯产量的同时减少磷养分进入流域水体的风险,通过田间试验研究了5种施磷处理(以P_(2)O_(5)计):0、90、135、180、225 kg·hm^(-2)对马铃薯产量、土壤有效磷累积、土壤磷平衡及磷肥利用率的影响。结果表明,施磷能显著提高马铃薯产量,增产幅度为35.3%~44.7%。马铃薯产量随施磷量的增加呈先增后减趋势,其中以施磷180 kg·hm^(-2)处理的马铃薯产量最高,为33020 kg·hm^(-2)。磷肥偏生产力和磷肥农学利用率均随施磷量的增加呈下降趋势,而磷肥表观利用率差异不显著。0~60 cm土层有效磷含量和累积量均随施磷量的增加呈增加趋势;各处理0~40 cm土层有效磷累积量占0~60 cm土层有效磷累积总量的78.6%~88.1%。将磷素盈余与施磷量、马铃薯产量、土壤有效磷含量和累积量、磷肥利用效率分别进行拟合,当磷素盈余为0时,施磷量为137.5 kg·hm^(-2),马铃薯产量为32756 kg·hm^(-2),0~20、20~40 cm和40~60 cm土层有效磷含量分别为70.5、49.4 mg·kg^(-1)和19.7 mg·kg^(-1),有效磷累积量分别为150.8、161.9 kg·hm^(-2)和64.8 kg·hm^(-2),磷肥偏生产力为242.1 kg·kg^(-1),磷肥农学利用率为72.7 kg·kg^(-1)。研究表明,在洱海流域高肥力水平农用地区域,施磷量131~144 kg·hm^(-2)可作为马铃薯高产且环境友好的磷肥投入阈值。

我国典型土壤中Co对生物的毒害及其阈值推导

随着人类对钴(Co)元素开发利用活动的增强,土壤Co污染问题日益受到重视。然而,目前对土壤Co的生态风险和阈值研究还很有限。本研究通过文献检索收集筛选Co生态毒性数据,并结合毒理学实验和物种敏感性分布法推导我国土壤Co的生态风险阈值。研究结果显示,文献检索和生态毒性实验获得了不同土壤性质下Co对10种生物的10%效应浓度(EC 10),变化范围为7~4696 mg/kg。利用逐步线性回归建立了8个物种EC 10和土壤性质(pH、CEC、OC含量和Clay含量)以及这些物种自身敏感性k值的关系,得到8个物种的k值在-0.21~1.458,并通过种间外推模型获得无归一化模型的黑麦草及玉米渣矿化k值(-1.207和2.201)。最终获得包含土壤性质和k值的10个物种的回归模型,据此模型将预测的EC 10值归一化到4种土壤条件下。利用物种敏感性分布法推导得到4种土壤条件下Co的生态安全阈值(HC 5),经过老化淋洗因子的校正,在酸性、中性、碱性和石灰性土壤条件下分别为7.3、44、72.08和38.88 mg/kg,该结果可为土壤Co污染风险评价及相关标准的制定提供依据。

基于三七质量安全的土壤Cd和Pb风险阈值

为保障三七(Panax notoginseng)绿色种植和质量安全,探讨中国三七安全生产的土壤风险阈值。分析土壤理化性质、土壤Cd(镉)、Pb(铅)含量和有效态、三七主根Cd、Pb含量,通过线性相关分析三七主根Cd、Pb与土壤理化性质及土壤Cd、Pb总量与有效态之间的关系。利用回归模型建立土壤Cd、Pb总量有效态与三七主根Cd、Pb的回归方程,反推土壤有效态Cd、Pb阈值。结果表明,三七种植区土壤Cd、Pb样品超标率分别是83.64%和16.36%,土壤Cd污染严重,土壤Pb处于清洁水平。三七主根Pb含量未超标,Cd含量超标率为29.09%。土壤pH与三七主根Pb呈显著负相关,三七主根Cd含量与土壤Cd含量和土壤有效态Cd含量分别呈显著和极显著正相关;三七主根Pb与土壤Pb含量和土壤有效态Pb均呈极显著正相关。基于三七主根Cd、Pb限量标准推导出土壤有效态Cd阈值为0.27 mg/kg,土壤有效态Pb阈值为70.66 mg/kg。

跨区域量化比较3种土壤类型坡面的拦蓄径流能力

[目的]基于定量化数值建立一个跨区域评价不同土壤类型和管理措施坡面拦蓄径流能力的指标体系,为水土流失防治工作提供科学指导。[方法]在新疆维吾尔自治区伊宁市北山坡的灰钙土、棕红土坡面和贵州赤水市大石河小流域的紫色土坡面各布设了4种管理措施的径流小区,基于2019—2021年4—9月的自然降雨量和径流量观测数据,用径流系数、径流曲线数(CN值)和降雨产流阈值数据量化比较了12个径流小区的减流能力。[结果]不同土壤拦蓄径流能力排序为:灰钙土<棕红土<紫色土,其CN值分别为90.05,89.53和77.36;其降雨产流阈值分别为3.44,3.50和14.96 mm。不同评价指标结果均显示,灰钙土和棕红土管理措施坡面的拦蓄径流能力顺序为:枯草覆盖>水平沟>增渗孔>对照;紫色土管理措施坡面减流能力的顺序为:园地>草地>耕地>对照。对于对照小区,当径流系数增加1%时,灰钙土、棕红土和紫色土的径流深分别增加了1.73,2.61和6.79 mm;当CN值增加1时,3种土壤坡面的径流深则将分别减少1.00,1.00和0.71 mm。[结论]跨区域评价不同土壤类型坡面的减流能力时,推荐用CN值和降雨产流阈值指标,不宜使用径流系数。

基于随机森林模型与SHAP算法的渝东北烟区土壤交换酸含量影响因素分析研究

【背景和目的】土壤交换酸含量在农业生产中对于指导施肥和调节土壤pH具有重要作用,研究环境因子(气候、地形、成土母岩)和种植年限对土壤交换酸(Exchangeable Acidity, EA)含量的影响。【方法】以重庆市东北烟区为研究区,对该区中483个采样点的土壤交换酸数据进行统计分析,构建随机森林(Random Forest, RF)模型并结合Shapley Additive exPlanations(SHAP)算法,探讨影响土壤交换酸含量的主控因素。【结果】(1)研究区土壤交换酸含量在1.56~27.50 cmol/kg之间,与降水、日照时数、坡向、种植年限呈极显著负相关性。二叠系石灰岩发育的土壤交换酸含量显著高于三叠系石灰岩发育的土壤。(2)RF模型可解释土壤交换酸含量空间变异的64%,影响因子对土壤交换酸含量的重要性为气候>成土母岩>种植年限>地形。(3)SHAP算法揭示了土壤交换酸含量在不同气候条件下存在明显的阈值效应。当年均降水量、日照时数和均温分别超过1250 mm、1290 h和12℃时,会导致土壤交换酸含量的减少,反之则会促使其增加。【结论】气候是影响土壤交换酸含量变异最重要的环境因素,其中降水和日照时数是最重要的气候因子,研究结果可为烟田土壤酸化管理调控提供参考。

基于去除土壤效应的烤烟叶面积指数及烟碱含量的无人机高光谱监测研究

[目的]土壤背景在无人机遥感监测中存在干扰作用,本文旨在对烟草长势和品质无人机高光谱监测进行去土壤效应的研究。[方法]通过实施2个品种、4个施氮水平互作处理的烤烟田间试验,利用无人机平台搭载的高光谱相机获取大田关键生育期的烤烟冠层反射光谱数据,并分别使用土壤植被组分光谱分解(3SV)算法与植被指数阈值法去除土壤效应后的各小区平均光谱,利用植被指数优化算法进行全生育期烤烟叶面积指数和烟碱含量的高光谱监测模型构建。[结果]在使用3SV算法后,波段组合与烟叶烟碱相关关系较高的区域分布在λ1:450~500 nm和λ2:580~660 nm组合以及λ1:630~670 nm和λ2:680~700 nm;波段组合与叶面积指数相关关系较高的区域分布于λ1:730~770 nm和λ2:750~800 nm组合以及λ1:510~600 nm和λ2:680~700 nm。基于3SV算法的烟叶烟碱含量与叶面积指数监测模型验证精度均较植被指数阈值算法处理后有不同程度提高,‘云烟87’烟碱的模型验证决定系数R 2从0.64提高到0.88,RMSE从0.71%降低至0.29%,效果最为明显。利用3SV算法与波段优化算法,筛选出与‘云烟87’和‘K326’叶面积指数关系最佳的指数分别为NDLI_(515,691)和NDLI_(764,799);与‘云烟87’和‘K326’烟碱含量关系最佳的指数分别为NDNI_(450,658)和NDNI_(456,654),并建立了适用于监测大田生育期的叶面积指数与叶片烟碱含量的模型。[结论]通过比较不同去除土壤背景算法,发现3SV算法提高了烟草叶面积指数与烟碱监测模型的精度,为无人机高光谱大面积监测烟草长势与品质提供了技术支持。

典型黄壤烟田莠去津残留降解及烟草致害阈值研究

通过田间试验研究贵州典型黄壤烟田莠去津的残留和消解动态,阐明烟草的药害发生及烟草的致害阈值与安全间隔期,并分析土壤环境因素对莠去津半衰期的影响。结果表明:莠去津对烟草生长发育的抑制作用十分明显,显示为叶片瘦小、严重者畸形,老叶叶尖脉黄化。烟草株高抑制率、叶面积抑制率与莠去津施药剂量均呈极显著正相关,随莠去津施用剂量的增加,株高和叶面积的抑制率增加。莠去津在典型黄壤中降解半衰期为8.45~11.95 d,田间安全隔离期应长于48.6 d,莠去津降解半衰期与土壤有机质含量呈显著正相关,与pH和速效钾呈显著负相关,与碱解氮和有效磷含量相关性不显著。研究结果对黄壤高粱/玉米-烟草轮作系统除草剂合理施用及烟叶安全性具有重要指导价值。