Spatial estimation of surface soil texture using remote sensing data

Understanding the spatial distribution and variability of soil texture is essential for land use planning and other activities related to agricultural management and environmental protection. This study was conducted to evaluate Landsat Enhanced Thematic Mapper (ETM) remote sensing data as auxiliary variables for spatial estimation of surface soil texture using a limited number of soil samples taken from a site located in the city of PingduShandong ProvinceChina. Three methods of evaluating variability in surface soil texture were evaluated: (1) multiple stepwise regression (MSR) based on the relationship between surface soil sandsilt and clay contents and remote sensing data; (2) kriging of surface soil sandsilt and clay contents; (3) cokriging with remote sensing data. Correlation analysis showed that surface soil sandsilt and clay contents were significantly correlated with Landsat ETM digital number (DN) of six bands (Bands 1–5 and Band 7)and the DN of Band 7 explained most of the variability in soil sandsilt and clay contents. The DN of Band 7 was selected as auxiliary data for the estimation of surface soil texture. The cross-validation results indicated that both MSR and kriged estimates had low reliability due to the variations in landscape and the low-density sampling in the study area. Cokriging with remote sensing data significantly improves estimates of surface soil texture compared with MSR and kriging.     

海涂土壤剖面电导率的协同克立格法估值及不同取样数目的比较研究

应用地统计学的半方差函数和普通克立格法 ,分析了 2 0m× 2 0m的采样间隔上 ,同一剖面0～ 2 0、2 0～ 4 0、4 0～ 6 0、6 0～ 10 0cm四个层次上海涂土壤电导率的空间相关性和空间分布。并在对协同区域化变量进行交互半方差分析的基础上 ,用协同克立格法 ,将 0～ 2 0cm层上的土壤样品作为辅助变量 ,其他三层上初始及减少后的土壤样品作为主变量 ,来对 2 0～ 4 0、4 0～ 6 0、6 0～ 10 0cm土层上的电导率进行估值。同普通克立格法相比 ,协同克立格法在这三层估值所产生的均方根误差 (RMSE)减少了 9%到 2 5 1% ,平均标准误差(ASE)减少了 9 4 %到 2 1 9% ,预测值与实测值之间的相关系数协同克立格法比普通克立格法提高了 4 6 %到85 %。数据分析的结果表明 ,利用协同克立格法 ,深层的样品数目在被减少至 6 0 %的情况下仍能满足精度要求 ,没有明显地导致空间信息的丢失。因此 ,协同克立格作为一种更为精确和经济的方法来对样品少的或难以测试的变量进行估值不但可以大大提高估测精度 ,而且可以减少采样数目 ,节省采样的成本。     

哈尔滨市辖区黑土速效养分空间异质性分析

研究在哈尔滨市所辖黑土区的6个市县进行,共采集表层(0～20cm)黑土土样411个,测定了全部样点的有机质、全氮的养分含量,同时测定了部分样点的碱解氮、速效磷、速效钾的养分含量,利用地统计学中协同克立格分析方法并结合经典统计学和GIS技术分析碱解氮、有效磷、速效钾养分空间异质性。分析表明有效磷空间分布符合指数模型,碱解氮、速效钾符合高斯模型,其块金值与基台值之比分别为50.0%、39.7%、6.3%,有效磷和碱解氮为中等程度空间相关水平,速效钾为强度空间相关水平;与克里格对比,应用协克里格插值绘制的三种速效养分空间分布图精度显著提高,为协克里格方法在土壤养分空间异质性分析上的应用提供了实践依据。     

Estimation and implications of instrumental drift, random measurement error and nugget variance of soil attributes—a case study for soil pH

We propose a general model for soil pH measurement that includes instrumental drift, random measurement error, and random and correlated spatial variation. Methods for estimating these four components are described in detail. For soil pH in water, instrumental drift, random measurement error and random spatial variation (nugget effect) were greater than the corresponding quantities for soil pH in CaCl₂. For both pH measurements, instrumental drift was quite marked. Measurement error and nugget effect were of a similar size. A modified kriging method is presented that takes into account the four-component model proposed here. It is concluded that, for measuring soil chemical attributes, grid layouts should be supplemented by additional sites for the estimation of short-range variation, that laboratory sampling designs should include controls, and that field measurements should be adjusted for instrumental drift prior to being used for spatial contouring or kriging.     

Adsorption‐desorption of zinc in mollisols and their relationship with uptake of fertilizer‐applied zinc by rice

Abstract

Zinc (Zn) adsorption in mollisols conformed to the linear form of Freundlich equation. The log K values were positively correlated with silt, clay, and carbonate contents and soil pH, but negatively correlated with sand content. Sequential desorption of adsorbed Zn in 0.05M Ca(NO₃)₂, 0.1M Mg(NO₃)₂, 0.005M DTPA, and 0.1M HCl revealed that weakly and specifically bound fractions of added Zn, which could easily equilibrate with soil solution, were low and decreased with silt and carbonate contents and soil pH. Weakly bound fraction increased with sand content. Strongly bound and complexed fraction of applied Zn was the maximum and increased with clay, soil organic carbon and carbonate contents and specific surface area, but decreased with sand content. The mineral bound fraction of applied Zn was intermediate and increased with silt, clay and carbonate contents, and soil pH and specific surface area. Zinc uptake due to added Zn fertilizer by rice crop (Y) negatively correlated with log K, but positively related to Zn content in the equilibrium soil extract and Zn desorbed in 0.05M Ca(NO₃)₂. Both log K and l/n values together explained 59.5% of the total variation in Y, while Zn content in the equilibrium soil extract, Zn desorbed in 0.05M Ca(NO₃)₂, 0.005M DTPA and 0.1M HCl collectively accounted 79.6% of the total variation in Y.     

Spatial variability of some nutrient constituents of an Alfisol from loess II. Geostatistical analysis

Spatial variability of NO₃, K, Mg and organic C of a loess field was studied by using a geostatistical concept, known as theory of regionalized variables. Fifty measurements were made at the nodes of a 30 m × 30 m grid for each of 0-30, 30-60 and 60-90 cm depths. Semivariograms determined from the data showed that NO₃ observations were spatially independent, and hence could be analyzed only by classical methods. Semivariograms of K, Mg and C showed these parameters to be correlated over space for a separating distance between two observations well exceeding 150 m. Their semivariograms were then used in an interpolation method called kriging, which takes into account the correlation between adjacent samples while estimating the interpolated (kriged) value without bias and with minimum variance. Means and estimation variances calculated by punctual kriging were compared to those obtained by classical theory assuming random sampling (i.e., no interdependence between observations). We obtained 1.4 to 3 fold gains in efficiency over that estimated by classical theory. One can, therefore, be sure that the estimation variance of the mean obtained in classical manner will overestimate the real variance unless the sample sites are so far apart that they are spatially independent. The kriged estimates were used to draw contour maps of the properties. Usefulness of such maps and the kriging technique as a whole is discussed to provide better options for management decisions. Finally, a method for determining sample sizes (i. e., number of observations), and hence sample spacing, is developed, taking account of spatial dependence. By this method, sample sizes can be chosen to achieve any desired precision. The sampling effort determined this way in less, and can be very less when based on block or universal kriging, than would have been judged necessary using the classical approach.     

Effect of soil pH and nitrogen source on nutrient status in peach: I. Macronutrients

Following 13‐year treatments of soil pH and nitrogen (N) source in a peach orchard of North Carolina, the concentration of calcium (Ca), magnesium (Mg), N, phosphorus (P), and potassium (K) in leaves, shoots, trunks and roots, as well as soil pH, soil exchangeable Ca, Mg, and K content, were determined. Through liming, higher soil pH treatment enhanced soil Ca and tissue Ca level. Among six N sources examined, the highest values of soil pH and soil Ca, Mg, and K were detected following poultry manure application. Compared to ammonium sulfate [(NH₄)₂SO₄], calcium nitrate [Ca(NO₃)₂] increased soil pH and soil Ca and K content, but reduced soil Mg. For most of macronutrients examined in peach tissues, the highest levels were found in manure treatment. Mineral N sources containing Ca(NO₃)₂ resulted in high tissue Ca and low tissue N. In the above‐ground tissues, Mg concentration was relatively low following application of mineral N materials containing Ca, K, or sodium (Na). Acid‐ forming N, especially (NH₄)₂SO₄, reduced tissue Ca and P. The magnitude of impact of liming and N source on macronutrients was tissue‐type dependent, with leaves and other new growth the most sensitive ones while trunks seldom responded to the treatments.     

Effects of equilibrating salt solutions on phosphate sorption by soils

Abstract

Several equilibrating salt solutions have been used in the studies of P sorption by soils and sediments. This study was conducted to evaluate the effects of 10 salt solutions on estimation of P sorption by soils. Results obtained showed that, when the equilibrating solution was made to contain 0.01M with respect to CaCl₂, Ca(NO₃)₂, CaSO₄, MgCl₂, KCl, LiCl, Nacl, or KHCO₃, the amount of P sorbed by soil always exceeded the amount sorbed from the soil‐water system. In comparison with the amount of P sorbed from water, 0.01M NaHCO₃ reduced P sorption by soils. Use of THAM buffer (0.05M pH 7.0) to control the pH increased P sorption by some soils and decreased P sorption by others, relative to that sorbed from the soil‐water system. The results indicated that inclusion of salts in the equilibrating solution for P‐sorption studies should be avoided, especially in studies related to water quality.     

Relationships between electrical conductivity and fertilizer levels in an azalea Liner growing medium

Abstract

Regression analyses were used to survey the effects of extractable NO₃‐N, P, K, Ca, Mg, and soil pH on electrical conductivity (EC) in a 1: 1: 1 (v/v/v) peat‐sand‐perlite azalea (Rhododendron sp.) growing medium amended with soluble 21–3–6 (N‐P‐K) or slow‐release 18–3–6 fertilizer sources. Simple linear correlations indicated a high degree of relationship between NO₃‐N, P, and K versus EC (r=0.95**, 0.79**, and 0.79**, respectively). Partial regression coefficients suggested that NO.‐N was the primary ionic species affecting EC. The correlations between EC versus P and K were apparently related to their intercorrelation with NO₃ ‐N, associated with the use of N‐P‐K fertilizers. These relationships were constant across fertilizer sources. The results demonstrate a potential for the use of soil EC in the estimation of NO₃‐N in soilless rooting media.     

Influence of nitrate on methane production and oxidation in flooded soil

Abstract

Methane (CH₄) production in paddy soils and sediments as influenced by nitrate (NO₃) addition was studied under a closely controlled soil pH and oxidation‐reduction (redox) potential (Eh) conditions. CH₄ production was affected by soil pH and NO₃ ^‐. Added NO₃ ^‐ reduced the amount of CH₄ produced of each pH level studied. Nitrate addition primary effect in reducing CH₄ production was through the resultant increase in soil redox potential (Eh). Using Methyl Fluoride (MF), a CH₄ oxidation inhibitor we found that added NO₃ ^‐ was not used in CH₄ oxidation by methanotrophic bacteria.     

Reduction in nitrate accumulation by molybdenum in spinach grown at low pH

Abstract

Spinach was grown in the greenhouse in soil with the pH adjusted to 5.0, 5.5, 6.0, 6.5, and 7.0, N fertilizer rates of 0, 50 and 200 mg N/Kg soil, and Mo fertilizer rates of 0, 0.3 and 1.2 mg Mo/Kg soil. The NO₃‐N concentration of the tissue increased with fertilizer N or a rise in pH from 5.0 to 7.0. The addition of Mo at either rate reduced the NO₃ concentration of spinach grown at pH 5.0 and 5.5 but had no effect on plants grown at pH 6.5 or 7.0. At pH 6.0 the 1.2 mg Mo/Kg soil rate was effective at the 50 and 200 mg N/Kg soil fertilizer rates but had no effect on spinach grown without a N application. At the same pH, the 0.3 mg Mo/Kg soil rate had no effect on NO₃ content of spinach grown with the 50 mg N/Kg rate but did reduce the NO₃ content of spinach grown without N added or with the 200 mg N/Kg soil. The 1.2 mg Mo/Kg soil rate was more effective than 0.3 mg Mo/Kg rate in reducing NO₃ content of spinach grown with 200 mg N/Kg soil at pH 5.0–6.5 inclusive but gave variable results when no N or 50 mg N/Kg soil was added. Molybdenum did not affect the total N or NO₂ concentrations of the plants.     

Abstracts of nippon Dozyohiryogaku Zasshi

The present study was carried out to analyze the factors that affected the growth of sugar beet in four different soil types by using concrete-framed plots as follows: soil acidity (soil pH, exchange acidity y ₁) and nitrification of fertilizer introduced by row application. Comparison of the value of the exchange acidity y ₁ of the four soil types with the pH value adjusted to the same level (pH 5.1) revealed that the Humic Gray Upland soil displayed the highest y ₁ value (y ₁: 18.0), followed by the Humic Volcanogenous Regosol (y ₁: 6.9), Haplic Brown Lowland soil (y ₁: 5.3), and Low-humic Andosol (y ₁: 2.2). Al release to the soil solution was considered to occur at soil pH values of 4.8 and lower except in the Low-humic Andosol. Al concentration in the soil solution of the Low-humic Andosol was substantially lower than that of the other soils. On the other hand, the soil pH value decreased temporarily by nitrification of the fertilizer introduced by row application, especially in the Humic Gray Upland soil. In this case, the soil pH value became lower than 4.8 for a time. At this pH level, Al release to the soil solution was assumed to occur. As described above, the soils displayed different properties in terms of soil acidity. In the four soils, although the growth of sugar beet was significantly related to both soil pH and exchange acidity y ₁ values before sowing, these relations were not strictly valid. On the other hand, the linear correlation coefficients of the relationships between the growth of sugar beet (leaf length) and NO₃-N content in rows were higher than those of the soil pH and exchange acidity y ₁. No appreciable variation associated with the differences in the soil types was observed in this relation. Furthermore, the values of both soil pH and exchange acidity y ₁ were closely related to the NO₃-N content in rows and the relationship between the NO₃-N content and y ₁ value appeared to be somewhat closer than that with the soil pH. These closer relations had two important implications. Firstly, NO₃-N content reflected the nitrogen nutrient conditions. NO₃-N promoted the growth of sugar beet directly. Secondly, the NO₃-N content was affected by the soil acidity, which is expressed by the value of the exchange acidity y ₁. Low NO₃-N content indicated indirectly the toxicity of soil acidity to sugar beet growth. It was thus suggested that in the present study, nitrification of the fertilizer expressed by the NO₃-N content was a beneficial factor for the growth of sugar beet regardless of the soil types. Finally, to promote the nitrification of fertilizer and to minimize the Al toxicity enhanced by the decrease of the soil pH associated with nitrification, it is important to avoid low values for the soil pH.     

Performance of Soil Electrical Conductivity and Different Methods for Mapping Soil Data from a Small Dataset

The performance of different methods for making soil maps from a small dataset was assessed. Soil samples obtained at five different depths were taken from 39 locations within an arable field in Sweden and analysed for clay content, soil organic matter content, pH (H₂O), K-HCl, P-AL, K-AL and Mg-AL. Detailed and densely sampled soil electrical conductivity (EC) data with a distinct border between two different regions was used for dividing the field into two zones. Averages from these zones gave better prediction for most variables than interpolation without respect to the border. With the border taken into account, cokriging with EC as a covariable improved the prediction, whereas the improvement with ordinary kriging and inverse distance weighting (IDW) was insignificant. Direct interpretation of EC by a simple linear regression model gave reasonable predictions for clay content. In general, even the simplest interpolation method improved the prediction compared to field average.     

红壤蔗区土壤有效态钾的空间变异研究

应用地统计学方法分析了农场尺度的红壤蔗区土壤表层的土壤速效钾、缓效钾的空间分布结构。结果表明,研究区域内的土壤速效钾和缓效钾含量都存在极强的空间相关性,在整个区域的空间分布具有相似性。缓效钾的协同克立格法的插值精度高于普通克立格法。研究结果可为甘蔗的钾肥精准管理提供依据。     

Salinity induced effects on the nutrient status of soil,corn leaves and kernels

Abstract

The effect of salinity in inducing soil macro and micronutrient deficiencies that can decrease crop growth was evaluated in a corn (Zea mays L.) field located in east central Wyoming. In this study water soluble Na was found to be a better predictor of salinity than pH and other cations. Soil saturated paste extracts had electrical conductivities that were negatively correlated with soil total K, Cu, Fe, and Mn. Total N, NO₃‐N, PO₄‐P, Zn, pH, and water soluble Na, Ca, and Mg of the soil were positively correlated with EC. Significant positive relationships existed between soil EC and N, P, Mo, and Zn, and negative relationships with K, Cu, Fe, and Mn of corn leaves and kernels. Concentrations of nutrients in the kernels were positively correlated with corresponding nutrient concentrations in the leaves and with AB‐DTPA extractable soil nutrients. The analysis of variance of EC data indicated that soil samples possessing high salinity were higher in pH and contained significantly higher soluble Na, Ca and Mg, total N, N0₃‐N, PO₄‐P, and Zn and significantly lower Mn compared to samples having low salinity. The kernel weight per cob and plant height were significantly reduced as salinity increased.     

Effect of effective microorganism and gypsum amendments on nutrient leaching,pH, electrical conductivity,and Okra growth parameters under coastal saline soil

Nutrients losses through leaching are the main problem facing coastal saline soil. Effective microorganisms (EM) and Gypsum (G) at the application rate of 5%G and 10%G by weight were used as soil amendments. The pot experiment aimed to improve the leaching of nitrate (NO₃), ammonium (NH₄) and total nitrogen (TN) on the coastal saline soil. The EM+ 5%G treatment effectively reduced the content of NO₃ and NH₄ in the leachate by 86.59% and 68.18%, respectively. EM treatment reduced the leaching of NO₃ and NH₄ by 70.86% and 62.12% and EM+ 10%G reduced NO₃ and NH₄ by 11.80% and 50.76%, respectively. Moreover, the content of TN in leachate was reduced up to 13.23%, 5.80%, and 2.67% in response to EM, EM+ 5%G, and EM+ 10%G, respectively, compared to the control. These results indicate that EM combined with G as soil amendments can reduce leaching of nutrients and further support the regulation of a coastal saline soil pH and EC.     

Characterization of nitrogen dynamics in a pasture soil by electromagnetic induction

The aim of this study was to investigate how electromagnetic induction can be used to improve the characterization of N dynamics in a 1.2 ha pasture. The soil apparent electrical conductivity (ECa) was measured by electromagnetic induction using an EM38DD. At 116 locations, soil samples were taken according to a clustered sampling design, three times during one winter, and analyzed for the NO₃^––N content in the topsoil (0–60 cm). Management zones were delineated using a fuzzy k-means classification of the interpolated ECa measurements. Two ECa zones were found, reflecting mainly differences in soil texture. Since the mean NO₃^––N content was different for the two ECa zones (24 and 65 kg/ha in November 2002), the residuals were interpolated using stratified simple kriging. This allowed evaluating the NO₃^– dynamics during the winter in both zones; one ECa zone showed a higher risk for NO₃^– losses than the other calling for a site-specific N management. As a validation, NO₃^––N was interpolated using ordinary kriging without stratification. This resulted in similar zones confirming the usefulness of the ECa measurements to assess N-specific management zones, even within small fields.     

土地混合使用制度下土壤硝态氮分布的地理空间制图研究

Mapping the spatial distribution of soil nitrate-nitrogen (NO₃-N) is important to guide nitrogen application as well as to assess environmental risk of NO₃-N leaching into the groundwater. We employed univariate and hybrid geostatistical methods to map the spatial distribution of soil NO₃-N across a landscape in northeast Florida. Soil samples were collected from four depth increments (0-30, 30-60, 60-120 and 120-180 cm) from 147 sampling locations identified using a stratified random and nested sampling design based on soil, land use and elevation strata. Soil NO₃-N distributions in the top two layers were spatially autocorrelated and mapped using lognormal kriging. Environmental correlation models for NO₃-N prediction were derived using linear and non-linear regression methods, and employed to develop NO₃-N trend maps. Land use and its related variables derived from satellite imagery were identified as important variables to predict NO₃-N using environmental correlation models. While lognormal kriging produced smoothly varying maps, trend maps derived from environmental correlation models generated spatially heterogeneous maps. Trend maps were combined with ordinary kriging predictions of trend model residuals to develop regression kriging prediction maps, which gave the best NO₃-N predictions. As land use and remotely sensed data are readily available and have much finer spatial resolution compared to field sampled soils, our findings suggested the effcacy of environmental correlation models based on land use and remotely sensed data for landscape scale mapping of soil NO₃-N. The methodologies implemented are transferable for mapping of soil NO₃-N in other landscapes.