Assessment of Spatial Variability of Soil Fertility Parameters Using Geospatial Techniques in Temperate Himalayas

Knowledge of spatial variability of soil properties is important in precision agriculture as well as site specific nutrient management. This paper addressed the spatial distribution characteristics of organic matter (OM), pH, available nitrogen (AvN), available phosphorus (AvP), available potassium (AvK) and available sulphur (AvS) in Research farm of SKUAST-K, Shalimar, Srinagar. A total of seventy seven (77) soil samples were collected in a systematic grid design using geographical positioning system (GPS). Each grid was specified at a fixed distance of 50 × 50 m2. The results showed that soil organic matter and S was distributed normally while as the three soil macronutrients (AvN, AvP and AvK) and soil pH followed log normal distribution. Soil available phosphorus had a highest coefficient of variation (56.87%) and the soil pH (7.06%) the lowest. All the soil macronutrients were found in medium range except sulphur which was found deficient in whole of the research farm. The experimental semivariogram of the log-transformed data of soil available phosphorus, potassium, sulphur, soil pH and normally distributed soil organic matter was fitted to exponential model. Gaussian model was found to be the best fit for experimental semivariogram of soil available nitrogen. Experimental semivariogram results indicated a moderate degree of spatial dependence for soil organic matter, available potassium and sulphur, soil pH and weak degree of spatial dependence for soil available nitrogen and phosphorus. Using such analyses, it is possible to plan appropriate soil management practices, including fertilization for agricultural production and environmental protection.

Spatial Variability of Soil Chemical Properties in the Reclaiming Marine Foreland to Yellow Sea of China

Precise information about the spatial variability of soil properties is essential in developing site-specific soil management, such as variable rate application of fertilizers. In this study the sampling grid of 100 m × 100 m was established to collect 1 703 soil samples at the depth of 0-20 cm, and examine spatial patterns including 13 soil chemical properties （pH, OM, NH4^＋, P, K, Ca, Mg, S, B, Cu, Fe, Mn, and Zn） in a 1 760 ha rice field in Haifeng farm, China, from 6th to 22nd of April, 2006, before fertilizer application and planting. Soil analysis was performed by ASI （Agro Services International） and data were analyzed both statistically and geostatistically. Results showed that the contents of soil OM, NH4^＋, and Zn in Haifeng farm were very low for rice production and those of others were enough to meet the need for rice cultivation. The spatial distribution model and spatial dependence level for 13 soil chemical properties varied in the field. Soil Mg and B showed strong spatial variability on both descriptive statistics and geostatistics, and other properties showed moderate spatial variability. The maximum ranges for K, Ca, Mg, S, Cu and Mn were all - 3 990.6 m and the minimum ranges for soil pH, OM, NH4^＋, P, Fe, and Zn ranged from 516.7 to 1 166.2 m. Clear patchy distribution of N, P, K, Mg, S, B, Mn, and Zn were found from their spatial distribution maps. This proved that sampling strategy for estimating variability should be adapted to the different soil chemical properties and field management. Therefore, the spatial variability of soil chemical properties with strong spatial dependence could be readily managed and a site-specific fertilization scheme for precision farming could be easily developed.

利用Kriging插值方法研究山东龙口北马镇农田土壤养分的空间变异

以山东省龙口市北马镇1000hm2的科技示范区为研究区,在地理信息系统平台ArcGIS上,采用GeostatisticalAnalyst地统计分析模块中的Kriging插值方法研究土壤养分的空间变异性。该分析过程中,发现影响分析工作结果精度的是Kriging插值模型的选择及Cross Validation交叉验证法的检验与系数修正。数据分析结果表明,龙口市北马镇0～20cm耕层土壤中碱解氮、速效钾含量空间相关性中等,速效磷含量具有强烈的空间相关性,有机质含量空间相关性较弱。

农田土壤微量元素的空间变异及Kriging估值

采用差分式GPS定位的方法,在山东省龙口市北马镇面积为10 km2的科技示范区内采用200 m×170 m网格式设置205个土壤采样点。用EDTA提取-原子吸收分光光度计测定法对示范区土壤微量元素铜、锌、铁、锰、硼的有效态含量进行了测定分析。在此基础上,选择Arcinfo地理信息系统软件,采用GeostatisticsAnalyst地统计分析模块中的Kriging插值方法对微量元素的空间变异性进行研究,该工作的关键是Kriging插值模型的选择及Cross-Validation交叉验证法的检验与系数修正。结果表明,龙口市北马镇0～20 cm耕层土壤中铜、锌、铁、锰、硼微量元素含量空间相关性中等,其中锌空间变异性相对较强,铜空间变异性相对弱一些。

Geostatistical Assessment of the Spatial Distribution of Some Chemical Properties in Calcareous Soils

Spatial patterns of soil fertility parameters and other extrinsic factors need to be identified to develop farming practices that match agricultural inputs with local crop needs. Little is known about the spatial structure of nutrition in Iran. The present study was conducted in a 132-ha field located in central Iran. Soil samples were collected at 0-30 cm depth and were then analyzed for total nitrogen （N）, available phosphorus （P）, available potassium （K）, available copper （Cu）, available zinc （Zn）, available iron （Fe） and available manganese （Mn）. The results showed that the contents of soil organic matter, Cu and Zn in Marvdasht＇s farms were low. The spatial distribution model and spatial dependence level for soil chemical properties varied in the field. N, K, carbonate calcium equivalent （CaCO3） and electrical conductivity （EC） data indicated the existence of moderate spatial dependence. The variograms for other variables revealed stronger spatial structure. The results showed a longer range value for available P （480 m）, followed by total N （429 m）. The value of other chemical properties values showed a shorter range （128 to 174 m）. Clear patchy distribution of N, P, K, Fe, Mn, Cu and Zn were found from their spatial distribution maps. This proved that sampling strategy for estimating variability should be adapted to the different soil chemical properties and field management. Therefore, the spatial variability of soil chemical properties with strong spatial dependence could be readily managed and a site-specific fertilization scheme for precision farming could be easily developed.

The Geostatistical Framework for Spatial Prediction

Geostatistics provides a coherent framework for spatial prediction and uncertainty assessment, whereby spatial dependence, as quantified by variograms, is utilized for best linear unbiased estimation of a regionalized variable at unsampied locations. Geostatistics for prediction of continuous regionalized variables is reviewed, with key methods underlying the derivation of major variants of uni-vafiate Kriging described in an easy-to-follow manner. This paper will contribute to demysti- fication and, hence, popularization of geostatistics in geoinformatics communities.

Optimised Spatial Sampling Scheme for Soil Electriclal Conductivity Based on Variance Quad-Tree (VQT) Method

The acquisition of precise soil data representative of the entire survey area, is a critical issue for many treatments such as irrigation or fertilization in precision agriculture. The aim of this study was to investigate the spatial variability of soil bulk electrical conductivity （ECb） in a coastal saline field and design an optimized spatial sampling scheme of ECb based on a sampling design algorithm, the variance quad-tree （VQT） method. Soil ECb data were collected from the field at 20 m interval in a regular grid scheme. The smooth contour map of the whole field was obtained by ordinary kriging interpolation, VQT algorithm was then used to split the smooth contour map into strata of different number desired, the sampling locations can be selected within each stratum in subsequent sampling. The result indicated that the probability of choosing representative sampling sites was increased significantly by using VQT method with the sampling number being greatly reduced compared to grid sampling design while retaining the same prediction accuracy. The advantage of the VQT method is that this scheme samples sparsely in fields where the spatial variability is relatively uniform and more intensive where the variability is large. Thus the sampling efficiency can be improved, hence facilitate an assessment methodology that can be applied in a rapid, practical and cost-effective manner.

基于定向半变异函数的裂隙网络空间变异性分析

运用地质统计学中的定向半变异函数,研究了个旧高松矿田莲花山断裂和五指山背斜裂隙网络的空间变异性。首先基于ArcGIS将野外露头裂隙网络进行数字化处理并提取裂隙密度和强度,然后依托GSLIB对裂隙密度和强度图沿着0~175°方位角计算,创建了36个实验性半变异函数并进行克里金插值,最后创建归一化的半变异函数图,量化各个断裂强度和断裂密度的二维空间变异性。研究表明,越是靠近断层裂隙密度和强度的空间变化幅度越大,并且其空间变异性存在显著的各向异性。空间变异性最小的方向平行断层且靠近断层,最大方向垂直断层且靠近断层,在褶皱近端空间变异性最小的方向平行于褶皱轴面方向,最大的方向则垂直于褶皱轴面方向。裂隙网络空间变异性质反映了断层和褶皱对裂隙网络发育的不同影响,为构建矿田三维裂隙网络空间分布模型提供参考。

Salinity assessment of groundwater for irrigation to prevent soil salinization

Electrical conductivity(EC)is considered as the most important indicator for assessment of groundwater quality.Determination of suitable interpolation method for derivation of groundwater quality variables map such as EC is dependent on region conditions and existence of enough data.For determining groundwater EC,341 groundwater samples were randomly collected from the central regions of Guilan province,paddy soils,in northern Iran.Interpolation methods including inverse distance weighting(IDW),global polynomial interpolation(GPI),local polynomial interpolation(LPI),radial basis function(RBF),ordinary kriging(OK)and empirical Bayesian Kriging(EBK)were used to generate spatial distribution of groundwater EC.The results indicate that EBK is a superior method with the least RMSE,MAE and the highest R 2.The generated maps can be used to identify the regions in the studied area where groundwater could be allowed to be extracted and utilized by farmers to reduce adverse effect of the scarcity of surface water.

太湖流域土壤养分空间变异特征分析——以浙江省平湖市为例

以位于太湖流域的浙江省平湖市为例,采用GIS与地统计学相结合的方法对其耕层土壤(0～20cm)的有机质、全氮、速效磷、速效钾等4种养分要素的空间变异特征进行了分析。结果表明:有机质和全氮变异函数曲线的理论模型能很好地符合球状模型;速效磷经对数转换后也符合球状模型;而速效钾的变异函数曲线则符合指数模型。有机质、全氮和速效磷具有很强的空间相关性,说明受母质、地形、土壤类型等自然的结构性因素影响较大;速效钾具有中等的空间相关性,说明由施肥、作物、管理水平等随机因素引起的空间异质性起很大作用。整个研究区东南部土壤质地较轻,大量施肥在提高其作物产量的同时,也可能会带来农业非点源污染等问题。

洞庭湖平原区土壤全磷含量地统计学和GIS分析

以洞庭湖平原区典型景观单元为试点,利用GPS定位共取得651个耕层(0～20cm)土壤样品。通过对数转化、稳健统计、域法处理和Box-Cox转化4种数据处理方法对土壤全磷进行了正态分布性检验。结果表明,Box-Cox转化成功地使数据集服从正态分布并消弱了异常值的影响,应用地统计学分析方法进行了实验变异函数的计算和最适合模型的拟合,得出土壤全磷最好的理论模型为球状模型,随后用普通克立格估值方法绘制了土壤全磷的空间分布图。在经过不同趋势阶数土壤全磷克立格(Kriging)插值误差的综合比较的基础上,结果表明趋势效应参数宜选取二阶。Kriging估值标准差(KSD)被认为是内插象素值的标准差,并为提高全磷的制图精度提供了有用的信息。应用地统计学和地理信息系统(GIS)的概率克立格法研究了洞庭湖平原典型区的土壤全磷的空间分布并进行了风险性评价。结果表明,土壤全磷不同含量水平下的概率分布图对风险性评价、合理施肥和控制磷素的面源污染的管理实践将是十分有益的。

江西省兴国县土壤全氮和有机质的空间变异及其分布格局

在地理信息系统和地统计学的支持下 ,以变异函数为工具 ,初步分析了江西省兴国县土壤全氮和有机质的空间变异特征 ,并应用克立格法进行最优无偏线性插值 ,得出全氮和有机质含量的分布格局 .结果表明 :全氮的变异函数曲线的理论模型符合球状模型 ,有机质为指数模型 ;两种养分的空间自相关程度均属中等的空间自相关 ;全氮和有机质空间变异的尺度范围不同 ,分别为 5 .4 1km和 9.36km .它们的空间变异主要是由结构性因素引起的 ;全氮和有机质含量的分布格局基本一致 ,具有北部高、中部和南部低的分布特征 .图 3表 2参

地统计学在土壤科学中的应用及展望

地统计学应用于土壤科学中,探索其空间分布特征及其变异规律,已为越来越多的学者所推崇。半方差函数提供了一个定量工具,可以将土壤某一性质的变异与成土因子和成土过程联系起来,使人们加深对土壤的作用后果的理解,而克立格可以对未采样区的区域化变量的取值进行无偏最优估计。在对地统计学的理论进行简要阐述的基础上,介绍了其近几年的发展,回顾了它在土壤科学研究中取得的一些成果,并就地统计学在土壤科学中的应用前景作了展望。

太湖流域典型地区土壤全氮的空间变异特征

在地理信息系统的支持下 ,运用地统计学方法分析了太湖流域典型地区耕层土壤全氮的空间变异特征 ,并在此基础上利用BlockKriging法绘制了土壤全氮的空间分布图。结果表明 ,研究区域土壤全氮具有明显的空间自相关性 ,自相关距离在 16km左右。在 4 0km步长变化范围内 ,土壤全氮的空间变异表现为明显的各向同性特征 ,超出此范围 ,各向异性趋向明显。Kriging插值结果表明 ,土壤全氮含量在江阴和宜兴境内要高于锡山和武进境内 ,且高值斑块区主要分布在地势低洼的圩田区。

土壤养分与作物产量的空间变异特征与精确施肥

对位于北京顺义的北方精准农业示范区 ,采用GPS定位 ,测定了其表层 80个土样的速效养分 (N、P、K、Fe、Mn、Cu、Zn)、有机质和全氮的含量及作物产量。结果表明 ,所有观测项目的变异系数均属于中等变异强度。作物产量与速效磷、全氮及有机质的相关性最大 ,pH与各种养分及微量元素均呈明显的负相关。通过结构分析 ,发现土壤pH的空间相关距最大 ,达 3.3km ,碱解氮和速效铁的自相关距最小 ,仅 0 .14km。其余观测项目的自相关距范围为0 .387- 1.11km。采用Kriging方法并结合GIS绘制了等值线图 ,可更直观地了解整个示范区的土壤养分丰缺状况。以施氮为例 ,精确管理的施肥方案要比粗放管理节约肥料 4 8.7%。

基于地统计学和GIS的太湖典型地区土壤属性制图研究——以土壤全氮制图为例

在地理信息系统 (GIS)支持下 ,运用地统计学方法对太湖典型地区耕层土壤全氮含量的空间变异特征进行分析 ,探讨了适用于研究区域土壤全氮制图的最佳邻域 ,并在此基础上利用块段克立格 (BlockKriging)法绘制了土壤全氮含量空间分布图。结果表明 ,土壤全氮的空间变异性在 40km步长变化域上表现为明显的各向同性 ,超出这个范围 ,土壤全氮空间变异的各向异性明显增强 ,以 40km步长变化域上土壤全氮的空间结构特征作为Kriging插值依据有助于提高制图精度。制图结果表明 ,研究区域土壤全氮含量在江阴和宜兴两市境内普遍较高 ,锡山和武进两市相对较低 ;且高值斑块区主要分布在地势低洼的圩田区 ,这是人为施肥和土壤特性共同影响的结果。

浙北环太湖平原耕地土壤重金属的空间变异特征及其风险评价研究

研究了浙北环太湖平原10个区县市耕地土壤Hg、Cd、Cr、Pb、Cu、As六种重金属的空间变异特征及其环境风险。结果表明,土壤Hg和Cd含量在总体分布上显现出较强的各区县市空间异质性,且这种变异更多与外界人为因素的影响密切相关。鉴于Hg在研究区域超标率高达10.34%,为该区土壤环境质量的主要限制因子,对土壤Hg用超过国家规定的土壤环境质量二级标准(0.3 mg kg-1)的离析克里格法(Disjunc-tive kriging)进行了风险评价,结果表明超标区域主要集中在各区县市的城镇和工矿企业周边,说明其与人为活动造成的大量大气粉尘、工业固废和城市垃圾的长期累积密切相关。研究认为在加快城市化和工业、农业现代化的同时,还应该考虑土壤污染与农产品质量、生态安全和人体健康的关系。

农田土壤微量元素含量的空间变异特征和影响因素

以浙江乐清市乐成镇为研究区域,采用地统计学和地理信息系统(GIS)相结合的方法,对土壤中有效态Fe、Mn、Cu、Zn和B含量的空间变异规律及其影响因素进行研究。描述性统计结果表明,土壤中微量元素Fe、Mn、B含量属于中等变异,Cu、Zn属于强变异。描述空间变异的半方差函数分析表明,Fe、Zn和B的最适模型是球状模型,Mn为指数模型,Cu为线性模型;Fe、Mn、Zn和B的块基比均小于25%,表明具有强烈的空间相关性,Cu的块基比大于75%,表明Cu含量具有较弱的空间相关性。土壤微量元素含量空间分布总体上呈现由东部向西部递减的趋势,其中Fe、Mn和B明显表现出连续分布的特点,Cu、Zn的分布没有明显的规律。土壤类型对Mn、Cu的含量有着显著影响,水稻土中Mn、Cu的含量显著高于红壤;土壤养分和微量元素的相关性分析可知,Fe与土壤pH、OM、全氮、碱解氮以及速效钾呈极显著相关,Mn、B与pH、速效磷和速效钾之间有显著或者极显著的相关性,Cu仅与速效钾显著相关,Zn的含量受土壤养分的影响较小,没有达到显著水平。

地统计学在土壤科学中的应用

地统计学目前在土壤科学中得到广泛的应用和发展,利用地统计学探索土壤特性的空间分布特征及其变异规律,已经成为认识土壤特征的一个重要工具.在对地统计学的基本原理及地统计学在土壤物理特性、土壤养分、土壤盐分、土壤重金属等土壤特性空间变异研究中的应用进行研究总结的基础上,对存在的问题及发展趋势提出了一些看法.

基于GIS和地统计学的土壤养分时空变异分析

运用ArcGIS的地统计学和空间分析模块,研究了封丘县20年前后土壤表层有机质、全氮、碱解氮、速效磷和速效钾5种养分的含量水平、分布以及演变趋势。研究结果表明,封丘县土壤有机质含量明显上升,氮素有所积累;磷素有升有降,以升为主;但速效钾含量急剧下降,这些变化与封丘县长期以来的肥料施用和土地利用有关。运用地理信息系统和地统计学方法能够很好地模拟土壤养分的空间分布特征,便于研究者直观地发现土壤养分时空变化趋势。