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1.
为探究不同作物覆盖下不同深度的土壤盐分快速反演模型,该研究采集苜蓿、玉米覆盖下0～15、15～30、30～50 cm层深度的土壤盐分含量,基于无人机多光谱影像数据,提取各地块采样点的光谱反射率,在此基础上引入红边波段计算光谱指数作为特征变量,采用支持向量机递归特征消除算法（Support vector machine-Recursive feature elimination,SVM-RFE）以筛选光谱指数及未经过筛选的全指数组作为模型输入组,共构建出36个基于随机森林（Random Forest,RF）、极限学习机（Extreme Learning Machine,ELM）、BP神经网络（Back-Propagation neural network）等机器学习模型,确定出不同作物覆盖下的最佳土壤盐分反演模型。结果表明：SVM-RFE算法筛选光谱指数构建模型精度优于未进行筛选构建的模型。对于苜蓿和玉米覆盖土壤,整体上,RF反演效果优于ELM模型和BPNN模型,反演结果能体现真实土壤盐分含量,在0～15和30～50 cm土层上,RF模型反演效果优于其他模型,苜蓿样地Rp2分别为0.71、0.58,RMSEp分别为0.026、0.033,玉米样地Rp2分别为0.67、0.64,RMSEp分别为0.111、0.094,在15～30 cm土层上ELM反演效果较好,苜蓿样地Rp2为0.58,RMSEp为0.039,玉米样地Rp2为0.68,RMSEp为0.059。0～15 cm是作物覆盖下的土壤含盐量最佳反演深度,验证集平均决定系数R2为0.65,均方根误差RMSE为0.084。研究结果可为土壤盐分的快速反演提供理论依据。 相似文献
2.
覆膜对无人机多光谱遥感反演土壤含盐量精度的影响 总被引：2，自引：2，他引：0
快速、准确地获取农田土壤盐分含量对指导合理灌溉及盐渍土的治理有重要意义。该文以内蒙古河套灌区沙壕渠灌域内的覆膜耕地为研究对象,利用无人机多光谱相机获取研究区内5月和6月的多光谱遥感数据,并同步采集区域内表层土壤含盐量数据,研究覆膜对无人机多光谱遥感图像反演农田土壤盐分含量精度的影响。利用支持向量机(support vector machine,SVM)、反向传播神经网络(back propagation neural network,BPNN)和极限学习机(extreme learning machine,ELM)3种机器学习方法,分别构建去膜前后基于原始光谱反射率和优选光谱指数的土壤含盐量估算模型。结果表明,去膜前后的各模型均可有效估测土壤盐分含量,但基于去膜处理后的数据构建的盐分含量估算模型精度较不去膜处理的有所提升,同时,基于光谱指数构建的盐分含量估算模型精度比基于光谱反射率构建的模型精度高;利用ELM构建的盐分含量估算模型在6月份预测效果最佳,其中基于光谱反射率和光谱指数的建模R2和RMSE分别为0.695、0.663和0.182、0.191,验证R2和RMSE分别为0.717、0.716和0.171、0.169。研究结果可为无人机多光谱遥感估算覆膜状态下的农田土壤盐分含量提供参考。 相似文献
3.
无人机多光谱遥感反演各生育期玉米根域土壤含水率 总被引：1，自引：3，他引：1
为准确及时地获取植被覆盖条件下农田土壤水分信息,该文以不同水分处理的大田玉米为研究对象,利用无人机遥感平台对夏玉米进行多期遥感监测,并同步采集玉米根域不同深度土壤含水率(Soil Water Content,SWC)。基于2018年夏玉米拔节期、抽雄-吐丝期和乳熟-成熟期的无人机多光谱遥感影像数据集,通过支持向量机(Support Vector Machine,SVM)分类剔除土壤背景,提取玉米冠层光谱反射率并计算10种植被指数(VegetationIndex,VI),然后利用全子集筛选(FullSubsetSelection)法对不同波段和植被指数进行不同深度土壤含水率的敏感性分析,并分别采用岭回归(Ridge Regression,RR)和极限学习机(ExtremeLearningMachine,ELM)2种方法构建全子集筛选后0～20、20～45和45～60cm不同深度下的土壤含水率定量估算模型。结果表明:基于贝叶斯信息准则(BayesianInformationCriterion,BIC)的全子集筛选法可以有效筛选最优光谱子集,筛选变量基本都通过了显著性检验,自变量个数较少;在同一生育期、同一深度条件下,ELM模型效果均优于RR模型;玉米在拔节期、抽雄-吐丝期的最佳监测深度为0～20cm,在乳熟-成熟期的最佳监测深度为20～45cm;乳熟-成熟期的20～45cm深度下的ELM反演模型效果最优,其建模集和验证集的决定系数Rc2和Rv2分别为0.825和0.750,均方根误差RMSEc和RMSEv分别为1.00%和1.32%,标准均方根误差NRMSEc和NRMSEv分别为10.85%和13.55%。利用全子集筛选法与机器学习相结合的方法可以提高土壤含水率的反演精度和鲁棒性,本研究为快速、准确地监测农田土壤墒情、实施精准灌溉提供了一种新的途径。 相似文献
4.
基于变量优选与机器学习的干旱区湿地土壤盐渍化数字制图 总被引：1，自引：1，他引：0
土壤盐渍化是导致土壤退化和生态系统恶化的主要原因之一，对干旱区的可持续发展构成主要威胁。为了尽可能精确地监测土壤盐渍化的空间变异性，该研究收集新疆艾比湖湿地78个典型样点，其中选取54个样本作为训练集，24个样本作为独立验证集。基于Sientinel-2 多光谱传感器（Multi-Spectral Instrument，MSI）、数字高程模型（Digital Elevation Model，DEM）数据提取3类指数（红边光谱指数、植被指数和地形指数），经过极端梯度提升（Extreme Gradient Boosting，XGBoost）算法筛选有效特征变量，构建了关于土壤电导率（Electrical Conductivity，EC）的随机森林（Random Forest，RF）、极限学习机（Extra Learning Machine，ELM）和偏最小二乘回归（Partial Least Squares Regression，PLSR）预测模型，并选择最优模型绘制了艾比湖湿地盐渍化分布图。结果表明：优选的红边光谱指数基本能够预测EC的空间变化；红边光谱指数与植被指数组合建模效果总体上优于其与地形指数的组合，3类指数组合的建模取得了较为理想的预测精度，其中RF模型表现最优（验证集R2=0.83，RMSE=4.81 dS/m，RPD=3.11）；在整个研究区内，中部和东部地区土壤盐渍化程度尤为严重。因此，XGBoost所筛选出的环境因子结合机器学习算法可以实现干旱区土壤盐渍化的监测。 相似文献
5.
盐荒地作为研究区的"临时盐库"，其土壤盐分远高于研究区平均水平，因此探究不同土地利用类型土壤盐分的光谱响应差异以及对盐分遥感模型的影响，是实现不同土地类型土壤盐分反演值更加接近真实值的重要途径。该研究以河套灌区永济灌域为例，针对耕地和盐荒地土壤分别进行原位高光谱测定（FieldSpec 4 Hi-Res，ASD），对光谱数据进行多种光谱变换（基础数学变换、导数变换及光谱指数）后，分别基于特征波长和特征光谱指数构建单一土地类型盐分反演模型（耕地（Agricultural Land，AL）、盐荒地（Salinized Wasteland，SW））和整体盐分反演模型（耕地+盐荒地（Agricultural Land + Salinized Wasteland，AL+SW）），对比分析2种建模方式下的模型精度，提出区域土壤盐分遥感反演的最佳建模方式。结果表明：AL、SW和AL+SW中土壤样本数据的平均含盐量分别为5.09、13.42和7.09 g/kg，且在各等级盐分区间内，SW的光谱反射率均大于AL，其中轻度盐化土、中度盐化土和重度盐化土的光谱反射率平均差值分别为0.040、0.020和0.034；光谱变换和光谱指数均能有效改善不同土地类型中土壤盐分与光谱的相关性。相比基础变换（倒数、对数、根式等），导数变换不仅增大了敏感波长的范围，还使得特定波长处相关系数得到显著提升。不同土地类型中基于特征光谱指数的模型精度均高于基于特征波长的模型；单一土地类型盐渍化反演模型明显提高了区域土壤盐分的反演精度，单一土地类型盐渍化反演模型中（AL、SW模型）各变换下光谱指数模型平均R2相比整体模型（AL+SW模型）由0.50提高到了0.61，其中基础变换、一阶导数和二阶导数模型平均R2相比整体模型分别提高了0.06、0.11和0.17，同时，基于最优光谱指数的单一土地类型盐渍化反演模型平均R2相比整体模型由0.74提高到了0.92。因此，当区域中存在盐分相差较大的多种土地利用类型时，对不同土地利用类型单独构建土壤盐分反演模型能确保反演结果更接近实际情况。 相似文献
6.
基于光谱指数与机器学习算法的土壤电导率估算研究 总被引：1，自引：0，他引：1
《土壤学报》2020,(4)
土壤盐分是干旱区土壤盐渍化评价的重要指标。以新疆维吾尔自治区渭干河-库车河三角洲绿洲为例,基于土壤电导率(Electrical conductivity,EC)及可见光-近红外(Visible and near infrared,VIS-NIR)光谱数据,通过蒙特卡洛交叉验证(Monte Carlo cross validation,MCCV)确定364个有效样本。采用原始光谱(Raw reflectance,R)及其经过微分、吸光度(Absorbance,Abs)、连续统去除(Continuum removal,CR)等6种预处理后的数据构建光谱指数。基于遴选出的21个最优指数,采用BP神经网络(Back propagation neural network,BPNN)、支持向量机(Support vector machine,SVM)、极限学习机(Extreme learning machine,ELM)三种算法对EC进行估算,并引入偏最小二乘回归(Partial least squares regression,PLSR)进行比较。结果表明:在基于R与6种光谱预处理数据构建的21个最优光谱指数之中,R_FD_RSI(R_(1913),R_(2142))表现最佳(r=0.649);与PLSR相比,机器学习算法能够显著提高模型的估算精度,R~2提高了34.55%。三种机器学习算法模型中,ELM表现最优(R~2=0.884,RMSE=3.071 mS·cm~(–1),RPIQ=2.535)。本研究中所构建的光谱指数在兼顾遥感机理的同时能深度挖掘更多的隐含信息,并且基于机器学习算法的土壤EC估算模型精度显著提高,为干旱区土壤盐分定量估算提供了科学参考。 相似文献
7.
基于改进植被指数的黄河口区盐渍土盐分遥感反演 总被引：10，自引：7，他引：10
快速获取土壤盐分的含量、特征及空间分布信息是盐渍土治理、利用的客观需求。该文针对黄河三角洲盐渍土,以垦利县为例,基于Landsat 8 OLI多光谱影像,在传统植被指数的基础上引入短波红外波段进行扩展,提出了改进植被指数;然后基于改进前后对应的植被指数,分别采用多元逐步回归(multivariable linear regression,MLR)、反向传播神经网络(back propagation neural networks,BPNN)和支持向量机(support vector machine,SVM)方法构建土壤盐分含量的遥感反演模型,并进行模型验证、对比和优选;最后基于最佳模型进行研究区土壤盐分含量的空间分布反演和分析。结果显示:相对传统植被指数,扩展后植被指数可增强与土壤盐分的相关性,大幅降低指数间的多重共线性;采用上述3种方法建模,改进后模型的精度比改进前都有提高,验证集决定系数R2提高0.04~0.10,均方根误差RMSE降低0.13~0.73,相对分析误差RPD提高0.25~0.34,改进后模型RPD均大于2.0,普遍达到性能良好;对比3种建模方法,SVM建模精度最高,BPNN模型次之,MLR分析精度最低,最佳模型为基于改进植被指数的土壤盐分含量支持向量机反演模型,建模集R2和RMSE为0.75、3.48,验证集R2、RMSE和RPD为0.78、3.02和2.56,模型较为准确、可靠;基于该模型反演的研究区土壤盐分含量整体较高,盐渍化程度空间分布表现为自西南部农业生产区至东北沿海区域逐渐加重,与实地调查一致。研究表明基于Landsat 8 OLI多光谱影像,引入第7波段对植被指数进行改进,从而构建土壤盐分含量的支持向量机模型,可获得较好的土壤盐分空间分布反演结果。 相似文献
8.
基于高光谱的ASTER影像土壤盐分模型校正及验证 总被引：6，自引：4，他引：2
快速准确地获取土壤盐分信息是监测和治理土壤盐渍化现象的重要前提.该文以新疆维吾尔自治区典型盐渍化区域——艾比湖流域为研究区,analytical spectral devices(ASD)光谱仪采集的土壤高光谱数据和advanced space borne thermal emission and reflection radiometer(ASTER)影像为数据源,结合实测土壤盐分含量信息,对遥感定量反演土壤盐渍化现象进行研究.再经过光谱反射率数学变换后,结合相关性分析,利用多元回归方法分别建立基于重采样后的高光谱和影像光谱的土壤含盐量估算模型,对遥感影像光谱盐分估算模型进行校正,以提高遥感定量监测盐渍化土壤的精度.结果表明:ASTER影像光谱反射率二阶导数变换和ASD重采样光谱的对数的二阶导数变换所建立的盐分估算模型最佳,决定系数R2分别为0.59和0.82.经ASD重采样光谱模型校正后的ASTER影像光谱的盐分估算模型精度R2为0.91,有效地提高大尺度条件下土壤盐渍化反演精度.研究为大尺度土壤盐分定量遥感监测提供了一种有效方法. 相似文献
9.
基于光谱指数与机器学习算法的土壤电导率估算研究 总被引：1，自引：0，他引：1
土壤盐分是干旱区土壤盐渍化评价的重要指标。以新疆维吾尔自治区渭干河-库车河三角洲绿洲为例，基于土壤电导率 (Electrical conductivity，EC) 及可见光-近红外 (Visible and near infrared, VIS-NIR) 光谱数据，通过蒙特卡洛交叉验证 (Monte Carlo cross validation, MCCV) 确定364个有效样本。采用原始光谱 (Raw reflectance, R) 及其经过微分、吸光度 (Absorbance, Abs)、连续统去除 (Continuum removal, CR) 等6种预处理后的数据构建光谱指数。基于遴选出的21个最优指数，采用BP神经网络 (Back propagation neural network, BPNN)、支持向量机 (Support vector machine, SVM)、极限学习机 (Extreme learning machine, ELM) 三种算法对EC进行估算，并引入偏最小二乘回归 (Partial least squares regression, PLSR) 进行比较。结果表明：在基于R与6种光谱预处理数据构建的21个最优光谱指数之中，R_FD_RSI (R1913，R2142) 表现最佳 (r = 0.649) ；与PLSR相比，机器学习算法能够显著提高模型的估算精度，R2提高了34.55%。三种机器学习算法模型中，ELM表现最优 (R2 = 0.884, RMSE = 3.071 mS?cm-1, RPIQ = 2.535) 。本研究中所构建的光谱指数在兼顾遥感机理的同时能深度挖掘更多的隐含信息，并且基于机器学习算法的土壤EC估算模型精度显著提高，为干旱区土壤盐分定量估算提供了科学参考。 相似文献
10.
土壤盐渍化高光谱特征分析与建模 总被引：3，自引：0，他引：3
基于高光谱遥感技术快速、无损的检测优势,以新疆渭干河-库车河三角洲绿洲为例,探讨利用反射光谱来预测土壤含盐量的可行性。利用野外采集的土壤样本,在实验室内测得了土壤含盐量及原始光谱反射率。利用光谱分析技术计算高光谱指数,与土壤样本含盐量进行相关性分析,筛选出土壤含盐量的光谱特征波段,基于逐步多元线性回归和偏最小二乘回归建立土壤盐分动态监测模型。通过精度检验,结果表明:基于偏最小二乘回归方法,以对数二阶微分光谱特征波段所构建的盐渍化遥感监测模型最优,模型的稳定性和预测精度最高。利用反射光谱来预测土壤含盐量可实现区域尺度上的土壤盐渍化实时监测和评价。 相似文献
11.
低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响 总被引：2，自引：2，他引：0
【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。 相似文献
12.
Kyle Devey Michael Mucalo Gordon Rajendram Joseph Lane 《Communications in Soil Science and Plant Analysis》2015,46(4):72-80
Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing. 相似文献
13.
《中国生态农业学报》2014,(8)
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology, 相似文献
14.
M.A. Callaham Jr. J.M. BlairT.C. Todd D.J. KitchenM.R. Whiles 《Soil biology & biochemistry》2003,35(8):1079-1093
The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils. 相似文献
15.
I.L. Boyd 《Biological conservation》2010,143(7):1664-1674
“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options. 相似文献
16.
Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage 总被引：1，自引：0，他引：1
Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate. 相似文献
17.
Grete Skrede Berit Karoline Martinsen Anne-Berit Wold Stein-Erik Birkeland Kjersti Aaby 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(3):193-208
Abstract A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species. 相似文献
18.
《Communications in Soil Science and Plant Analysis》2012,43(7):865-877
Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L?1 nitric acid (HNO3) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L?1 ammonium acetate (NH4OAc) and 1.0 mol L?1 HNO3 extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils. 相似文献
19.
Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater 总被引：3，自引：0，他引：3
Biologically enhanced dissolution offers a method to speed removal of chlorinated solvent dense non-aqueous-phase liquid (DNAPL) sources such as tetrachloroethene (PCE) and trichoroethene (TCE) from aquifers. Bioremediation is accomplished by adding an electron donor to the source zone where fermentation to intermediates leading to acetic acid and hydrogen results. The hydrogen and possibly acetic acid are used by dehalogenating bacteria to convert PCE and TCE to ethene and hydrochloric acid. Reductive dehalogenation is thus an acid forming process, and sufficient alkalinity must be present to maintain a near neutral pH. The bicarbonate alkalinity required to maintain pH above 6.5 is a function of the electron donor: 800 mg/L of bicarbonate alkalinity is sufficient to achieve about 1.2 mM TCE dechlorination with glucose, 1.7 mM with lactate, and a much higher 3.3 mM with formate. Laboratory studies indicate that in mixed culture, formate can be used as an electron donor for complete conversion to ethene, contrary to pure cultures studies indicating it cannot. Various strategies can be used to add electron donor to an aquifer for DNAPL dehalogenation while minimizing pH problems and excessive electron donor usage, including use of injection-extraction wells, dual recirculation wells, and nested injection-extraction wells. 相似文献
20.
Yoav Bashan Bernardo Salazar Ma. Esther Puente Macario Bacilio Robert Linderman 《Biology and Fertility of Soils》2009,45(6):585-594
To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse
trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus
were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB;
the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons
reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened
later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons
growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants,
no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi,
enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant.
In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after
30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination
only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity
to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as
compost or PGPB can either amplify the effect or else attenuate it. 相似文献