Characterization of Spatial Variability of Soil Parameters in Apple Orchards of Himalayan Region Using Geostatistical Analysis

ABSTRACT

Knowledge of spatial variability in soil properties is critical for effective nutrient management plan in crop production. Poor productivity of apple orchards in Indian Himalayan Region (IHR) is due to lack of information on the variability of soil properties important for enhancing productivity in the region. The study was conducted in apple orchards with the hypothesis that spatial variability of soil properties is high due to adoption of varied management and passive soil factors. The major objectives of the study were to assess the spatial variability of soil parameters, viz. soil pH, electrical conductivity, soil organic carbon along with plant available soil nitrogen (N), phosphorus (P), potassium (K), exchangeable calcium (Ca), and exchangeable magnesium (Mg) at a regional scale through geostatistical methods. Coefficient of variation (CV) indicated that the fertility parameters varied from medium to high in heterogeneity (CV > 20%). Available N was found critical/medium in 69.6% of soil samples and might be one of the limiting nutrients for crop growth, P and K were in high, and OC in very high range. Significant correlation was found between OC with N; pH with K, Ca and Mg and EC with OC, P and K. The semivariogram parameters indicated that the spatial distribution of soil fertility parameters were inconsistent and showed strong to weak degree of spatial dependence for all parameters. The study highlighted the importance of delineation of soil fertility management zones in the apple growing region as a guide for precise and site-specific nutrient.     

Spatial Variability of Soil Total Nutrients in a Tobacco Plantation Field in Central China

The spatial variability of soil total nutrient levels, which may be greatly affected by parent material, plays an important role in both agriculture and environment, especially with regard to soil fertility and soil quality. Little research has been done that addresses the spatial characteristics of total nutrients. Soil samples (0–20 cm) were taken from 111 points on an approximately 20-m grid in March 2009 using a global positioning system (GPS) to define sample locations. Sixteen soil total chemical properties were analyzed by classical statistical and geostatistical methods. Soil aluminum (Al), calcium (Ca), chromium (Cr), copper (Cu), nitrogen (N), sodium (Na), silicon (Si), strontium (Sr), titanium (Ti), and vanadium (V) exhibited strong spatial dependence, with the nugget–sill ratios ranging from 3.39% (Na) to 23.53% (Si). Soil barium (Ba), iron (Fe), potassium (K), manganese (Mn), phosphorus (P), and zinc (Zn) had moderate spatial dependence, with nugget–sill ratios of 3.39% to 23.53%. The spatial correlation distances varied from 15.7 m (Zn) to 286.5 m (Cr). The clearly patchy distributions indicated that significant positive correlations among Al, Ba, Fe, K, Mn, Na, Si, Ti, and V led to strong positional similarity. The interpolated maps of the nutrients showed the spatial distributions of the soil variables, which is helpful for better understanding their spatial variability and delineating the potential agricultural management zone. The soil total nutrient distribution maps could be used as the basis for site-specific fertilizer application to improve quality and increase yield of flue-cured tobacco in the study area.     

Accounting Spatial Variability of Soil Properties and Mapping Fertilizer Types Using Geostatistics in Southern Ethiopia

This study assesses soil spatial variability and maps fertilizer types using geostatistics. A total of 789 soil samples were collected from Wolaita area, Southern Ethiopia. Ordinary kriging was employed. The result considering coefficient of variation exhibited diverse soil variability (10% to 236%). Exponential semivariogram model described spatial structure of organic carbon (OC), total nitrogen (N), phosphorus (P), magnesium (Mg), boron (B), iron (Fe), zinc (Zn), cation exchange capacity (CEC) and potassium(K)/Mg. Semivariogram model was spherical for pH, calcium (Ca), manganese (Mn), and Gaussian for sulfur (S) and K. Spatial dependence was strong (Cu, Fe and Zn), moderate (pH, OC, N, S, Ca, Mg, B, Mn and CEC), and weak (P and K). Autocorrelation was between 276 and 15,118 meters. Overall, 46% of nutrients (N, P, K, S, B, and Cu) obtained from soil were deficient. Thus, for site-specific nutrient interventions, three fertilizer types (NPKSBCu, NPSBCu, and NPKSB) are suggested.     

DRIS Norms and their Field Validation in Nagpur Mandarin

ABSTRACT

Diagnosis and recommendation integrated system (DRIS) norms were computed from the data on leaf mineral composition, soil available nutrients, and corresponding mean fruit yield of three years (1999–2002), collected from the set of 57 irrigated commercial ‘Nagpur’ mandarin (budded on Citrus jambhiri Lush) orchards, representing 26 locations and 3 basalt derived soil orders (Entisols, Inceptisols, and Vertisols) rich in smectite minerals. The DRIS norms derived primarily from spring-cycle index leaves from non-fruiting terminals sampled during August to October (6–8 months old) suggested optimum leaf macronutrient concentration (%) as: 1.70–2.81 nitrogen (N), 0.09–0.15 phosphorus (P), 1.02–2.59 potassium (K), 1.80–3.28 calcium (Ca), and 0.43–0.92 magnesium (Mg). While, optimum level of micronutrients (ppm) was determined as: 74.9–113.4 iron (Fe), 54.8–84.6 manganese (Mn), 9.8–17.6 copper (Cu), and 13.6–29.6 zinc (Zn) in relation to fruit yield of 47.7–117.2 kg tree^{? 1}. Likewise, DRIS indices for soil fertility developed from dripline soil samples collected at 0–20 cm depth corresponding to similar level of fruit yield, the optimum limit of soil available nutrients (mg kg^{? 1}) was observed as: 94.8–154.8 N, 6.6–15.9 P, 146.6–311.9 K, 401.0–601.6 Ca, 85.2–369.6 Mg, 10.9–25.2 Fe, 7.5–23.2 Mn, 2.5–5.1 Cu, and 0.59–1.26 Zn. Primary DRIS indices developed on the basis of leaf and soil analysis revealed deficiency of N, P, K, Fe, and Zn. The nutrient constraints so diagnosed were further verified through fertilizer response studies carried out on a representative Typic Haplustert soil type facing multiple nutrient deficiencies, and accordingly suggested the revised fertilizer schedule.     

DIAGNOSIS AND RECOMMENDATION INTEGRATED SYSTEM (DRIS) FOR EVALUATING NUTRIENT STATUS OF COTTON (GOSSIPIUM HIRSUTUM)

Diagnosis and Recommendation Integrated System (DRIS) approach was employed to monitor the nutrient status of cotton (Gossipium hirsutum) in southwestern districts of Punjab, North-West India. DRIS norms for macro, secondary and micro nutrients in cotton plant are developed. Considering these DRIS norms, the most limiting nutrient for cotton plant in the region is identified along with the order in which the other nutrients become limiting. The DRIS approach indicated that 11, 3, 8, 5, 2, 4, 2, 3, 6 and 2 percent of the total cotton leaf samples collected were low in nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu), respectively. Leaf tissues of cotton plant were also found to contain high to excessive content of N, P, K, Ca, Mg, S, Fe, Mn Zn and Cu in 11, 7, 15, 19, 25, 18, 66, 33, 9 and 25 percent samples, respectively. DRIS derived sufficiency concentration ranges obtained from survey of cotton fields in this region were 2.22 to 5.20% N, 0.20 to 0.47% P, 1.05 to 2.14% K, 1.66 to 2.86% Ca, 0.34 to 0.57% Mg, 0.65 to 1.11% S, 106 to 172 mg kg^?1 Fe, 35 to 68 mg kg^?1 Mn, 18 to 33 mg kg^?1 Zn, and 5 to 8 mg kg^?1 Cu. The results elucidate that DRIS technique can be used for macro, secondary and micro nutrients indexing of cotton crop irrespective of its cultivar.     

Soil fertility and yield-limiting nutrients in oil palm plantations of north-eastern state Mizoram of India

A survey was conducted for assessment of soil fertility status, leaf nutrient concentration and finding yield-limiting nutrients of oil palm (Elaeis guineensis Jacq.) plantations in Mizoram state situated in the northeastern part of India. Soil pH, electrical conductivity (EC), organic carbon (OC), available potassium (K), available phosphorus (P) (Bray's-P), exchangeable calcium (Ca) (Exch. Ca) and magnesium (Mg) (Exch. Mg), available sulfur (S) (CaCl₂-S), and hot-water-soluble boron (B) (HWB) content in surface (0–20 cm depth) and subsurface (20–40 cm depth) soil layers varied widely. Diagnosis and Recommendation Integrated System (DRIS) norms were established for different nutrient expressions, and DRIS indices were computed. As per DRIS indices, the order of requirement of nutrients was found to be B > K > Mg > P > nitrogen (N). Optimum leaf nutrient ranges as per DRIS norms varied from 1.91% to 2.95%, 0.46% to 0.65%, 0.63% to 1.00%, 0.48% to 0.88%, and 9.41 to 31.0 mg kg^?1 for N, P, K, Mg, and B, respectively. On the basis of DRIS-derived optimum ranges, 32%, 9%, 27%, 12%, and 12% leaf samples had less than optimum concentration of N, P, K, Mg, and B, respectively. The optimum ranges developed could be used as a guide for routine diagnostic and advisory purpose for efficient fertilizer application.     

Soil Nutrient Status and Leaf Nutrient Norms in Oil Palm (Elaeis Guineensis Jacq.) Plantations Grown in the West Coastal Area of India

Oil palm (Elaeis guineensis Jacq.) is a heavy feeder of nutrients and requires balanced and adequate supply of nutrients for optimum growth and yield. Information regarding soil nutrient status and leaf nutrient concentration is very much required for proper fertilizer application. Therefore, a survey was conducted for assessment of soil nutrient status and leaf nutrient concentration in 64 oil palm plantations in the state of Goa lying in the west coastal region of India. Soil pH, electrical conductivity (EC), organic carbon (OC), available potassium (K) (ammonium acetate-extractable K) (NH₄OAc-K), available phosphorus (P) (Bray’s-P), exchangeable calcium (Ca) (Exch. Ca) and magnesium (Mg) (Exch. Mg), available sulphur (S) (calcium chloride-extractable S) (CaCl₂-S), and hot water soluble boron (B) (HWB) in surface (0–20 cm depth) soil layers ranged from 4.25 to 6.77, 0.05 to 1.06 dS m^–1, 5.07 to 48.4 g kg^–1, 58.1 to 1167 mg kg^–1, 1.80 to 415 mg kg^–1, 200 to 2997 mg kg^–1, 36.0 to 744 mg kg^–1, 3.00 to 87.7 mg kg^–1 and 0.09 to 2.10 mg kg^–1, respectively. Diagnosis and Recommendation Integrated System (DRIS) norms were established for different nutrient expressions and were used to compute DRIS indices. As per DRIS indices, the order of requirement of nutrients in the region was found to be P > Mg > K > nitrogen (N) > B. Optimum leaf nutrient ranges as per DRIS norms varied from 1.64 to 2.79%, 0.36 to 0.52%, 0.37 to 0.75%, 0.89 to 1.97%, 0.35 to 0.63%, 0.89 to 1.50%, 3.10 to 13.9 mg kg^?1, 7.50 to 32.2 mg kg^?1, 35.0 to 91.1 mg kg^?1, 206 to 948 mg kg^?1, and 895 to 2075 mg kg^?1 for N, P, K, Ca, Mg, S, B, copper (Cu), zinc (Zn), manganese (Mn), and iron (Fe) respectively. On the basis of DRIS-derived sufficiency ranges, 14, 5, 11, 6, 6, 6, 8, 2, 3, 6, and 16% of leaf samples had less than optimum concentrations of N, P, K, Ca, Mg, S, B, Cu, Zn, Mn, and Fe respectively. The optimum ranges developed can be used as a guide for routine diagnostic and advisory purpose for balanced utilization of fertilizers.     

DRIS NUTRIENT NORMS FOR PINEAPPLE ON ALFISOLS OF INDIA

Sub-optimum production in pineapple fields in India is a common feature in Alfisols. The diagnosis and management of nutrient constraints assume a greater significance in maximizing production sustainability. DRIS norms were computed from the data bank of 324 sub-plots on leaf mineral composition, soil available nutrients, and corresponding mean yield representing three diverse pineapple belts for 3 seasons during 2002 –04. DRIS norms derived primarily from basal portion of ‘D'leaves sampled at 4th to 5th month suggested optimum leaf nutrient concentration viz. 1.21–1.85% nitrogen (N), 0.13–0.18% phosphorus (P), 1.19–1.62% potassium (K), 0.27–0.35% calcium (Ca), 0.43–0.56% magnesium (Mg), and 78.4–102.5 iron (Fe), 41.5–58.3 manganese (Mn), 7.4–10.2 copper (Cu), and 12.2–15.8 zinc (Zn) (ppm) in relation to fruit yield of 55–72 tons ha^?1. Likewise, DRIS norms for soil fertility corresponding to similar level of fruit yield were determined. The norms were further observed validating the leaf/soil test values obtained from productive plots, suggesting the DRIS as a dynamic interpretation tool for diagnosis of nutrient constraints using both, leaf as well as soil analysis.     

Development of DRIS norms for potato in the calcareous soils of iran 1

The Diagnosis and Recommendation Integrated System (DRIS) has been proposed to determine nutrient balance in plants at different stages of growth. The DRIS index for each nutrient allows ranking of nutrients in order of their deficiency. Preliminary DRIS norms for potato (Solanwn tuberosum L.) were developed during the 1991 growing season in Damavand area located 70 km. northeast of Tehran. The soil and leaf samples at flowering stage (early tuber development stage) were collected from 50 different farms. Average concentrations of nutrients in both high‐ and low‐yielding populations were calculated. The following average foliar nutrient concentration were obtained from the high‐yielding populations: N = 5.22, P = 0.38, K = 4.20, Ca = 1.50, and Mg = 0.65 percent; and Fe = 150, Mn = 50, Zn = 40, Cu = 11, and B = 38 ppm. The average nutrient concentrations for the low‐yielding population were close to those in high‐yielding ones except for K which was 3.23 in contrast to 4.20‐percent. There was no significant relationship between different soil nutrient availability indices and yield except for K. The DRIS indices ranked K as the most limiting nutrient in the low yielding farms with only one exception. It seems high rates of N and P fertilization have created a lack of balance between these nutrients and K.

As a result of this study, the following appropriate norms for potato leaves are suggested for the calcareous soils of Iran: N = 4.5, P = 0.30, K= 5.00, Ca = 1.50, and Mg = 0.65 percent; and Fe = 150, Mn = 50, Zn = 40, Cu = 11, and B = 38 ppm. These results will be verified by field fertilizer experiments for N, P, K, Zn, and Fe which are some times deficient in potato soils.     

基于GIS和地统计学的低丘红壤地区三种土壤性质空间变异性研究

以浙江省金华市为例,采用地统计学和GIS相结合的方法,对低丘红壤地区土壤有机质、有效N、有效K3种主要性质的空间变异特性进行研究。研究表明,通过平方根转换后,三者都呈很好的正态分布。有机质的变异函数曲线的理论模型较好地符合球状模型,有效N和有效K则符合指数模型。三者都属于中等空间相关性,同时受到结构性因素和随机性因素的共同影响。通过分析3种土壤性质的各向异性,发现不同的土壤性质有不同的空间分布,同一土壤性质在不同的方向上也有不同的空间变异性。     

Spatial Variability of Nutrients in Wheat Plants in Semi-arid Regions of Northwestern Pakistan

This study was undertaken to assess spatial variability of nutrients in wheat plants for variable-rate site-specific fertilizer-management strategy. Wheat plants were collected from two semi-arid regions in northwestern Pakistan during 2004 and analyzed for nutrient contents and spatial variability. Wheat samples from both regions showed widespread deficiency of phosphorus (P), potassium (K), and zinc (Zn). In Kohat, Zn and manganese (Mn) were spatially distributed, described by linear models with moderate spatial patterns, but K, copper (Cu), and iron (Fe) showed weak spatial structures. In Bannu, K was described by a linear model with strong spatial structure and Fe had moderate spatial structure, but P, Cu, Mn, and Zn had random spatial distributions. The maps developed in this study showed variation in plant nutrients and spatial trends in the cases of spatially distributed nutrients and can be used to delineate plant nutrients into low, medium, and high categories to develop variable-rate fertilizer-management strategy.     

DRIS and geostatistics indices for nutritional diagnosis and enhanced yield of fertirrigated acai palm

Abstract

Information about Açaí palm (Euterpe oleracea Mart.) nutrition, that gives support for yield increase is sparse. The aim of this study was to assess the nutritional status of fertigated Açaí palm by the Index called Diagnosis and Recommendation Integrated System (DRIS), as well as the spatial variability of this Index and its productivity. We achieved a sampling of 80 geo-referenced points in an Açaí palm commercial crop area. Then we assessed the yield and contents of N, P, K, Ca, Mg, S, B, Cu, Fe, Mn and Zn. The DRIS evaluation indicated that the frequency of nutrients in suitable status was N?>?S?>?Zn?>?B>Fe?>?K>Ca?>?Mg?>?P>Mn?>?Cu, in deficiency was Mn?>?Ca >?B>Cu?>?Mg?>?Fe?>?K?>?P?>?S>Zn?>?N, and in excess was P?>?Cu?>?Mg?> K?>?N?=?Zn?>?Fe?>?Ca?>?S?=?B?>?Mn. The nutrients N and S were well balanced, whereas Mn, Ca and B were the nutrients with the highest frequency of deficiency. The sampling points were close enough to detect the spatial variability of DRIS Index. Thus, it was possible to observe the patterns for the nutritional deficiencies, occurring at the final part of the irrigation, as well as the variability of the Açaí palm yield. The spatial variability of the DRIS Index was efficient to indicate the points in which fittings in the fertilization doses are required.     

Geographic Information System and Geostatistical Techniques to Characterize Spatial Variability of Soil Micronutrients Including Toxic Metals in an Agricultural Farm

Knowledge of spatial variability of soil properties is critical for precision farming and identification of pollution hot spots. This study examined the spatial dependence and variability of microelements to produce nutrient maps for site-specific nutrient management and for environmental modeling. A total of 94 grid samples (50 × 50 m²) were collected and analyzed for available zinc (Zn), copper (Cu), manganese (Mn), iron (Fe), nickel (Ni), cadmium (Cd), and lead (Pb) using an atomic absorption spectrometer. Coefficient of variation (CV) indicated that all the microelements were high in heterogeneity (CV > 35%). Available Zn was found deficient in 66.4% of soil samples and might be one of the limiting nutrients for crop growth, Cu and Ni were in medium, and Fe and Mn in very high range. Pb and Cd were lower than standard values, but careful management will avoid toxicity. Significant correlation was found between Zn with Fe (r = 0.377); Ni with Mn and Fe (r = 0.350 and 0.205, respectively); and Pb with Mn and Ni (r = 0.298 and 0.221, respectively). Spatial variability of soil microelements was mapped by ordinary kriging using exponential model for Fe, Mn, Ni, Cd, and Pb; Gaussian model for Cu, and spherical model for Zn. Semivariogram showed strong to weak degree of spatial dependence for all microelements. The study highlighted the importance for the creation of nutrient management zones for Zn availability. The spatial variability maps generated could be used as a guide for precise and site-specific micronutrient management in the study region.     

Diagnosis of Nutrient Imbalance in Thompson Seedless Grape Grafted on Dog Ridge Rootstock by DRIS

Abstract

A nutrient concentration vs. yield data bank was established for vines grafted on Dog Ridge (Vitis champini) rootstock for developing DRIS ratio norms during bud differentiation stage (BDS) and flowering stages (FS). The data were further subdivided into medium‐ and low‐yielding population based on yield performance. DRIS ratio norms were developed for medium‐yielding population, while diagnoses of nutrient imbalances were made in the low-yielding population. Sixty‐six nutrient expressions were chosen as diagnostic norms. Among the nutrient ratios selected to form diagnostic parameters phosphorus/nitrogen (P/N) (0.260), potassium/nitrogen (K/N) (1.761), phosphorus/zinc (P/Zn) (0.0056) had greater physiological rationale during flowering stage. The ratios of N with P (N/P 3.42) and K (N/K 0.68) were found to be more critical during BDS. Group differences between low‐ and medium‐yielding population were determined using discriminant analysis. The nutrient concentration during FS in medium‐ and low‐yielding populations differed significantly, and magnesium (Mg) accounted for nearly 60.97% of the variation. The difference in mean nutrient concentration during BDS and FS was mainly due to Mg followed in importance by sodium (Na). During BDS Na, followed by Mg and calcium (Ca) were the most common yield‐limiting nutrient, while there was an accompanying excessive accumulation of K, manganese (Mn), and iron (Fe). During FS, Fe, copper (Cu), and K were the most common yield‐limiting nutrients whereas Ca, N, and Mg were on the excessive range.     

土壤速效氮、磷、钾含量空间变异特征及其影响因子

利用地统计学和GIS相结合的方法,探讨了双流县土壤速效氮、磷、钾含量空间变异特征及其影响因子。结果表明:1) 土壤速效氮和速效钾含量具有强烈的空间相关性,相关距离分别达38754 m和56187 m,结构性因子是影响其空间变异的主要因子;土壤速效磷含量具有中等空间相关性,相关距离为24210 m,其空间变异受结构性因子和随机性因子共同影响。2) 土壤速效氮含量主要由北向南逐渐降低;速效磷含量主要在东北向西南及东南向西北方向上逐渐降低,而速效钾含量主要由东南向西北逐渐降低。3) 土壤速效氮含量在不同土壤类型及地形地貌间呈极显著差异;土壤速效磷含量在不同成土母质及地形地貌间呈显著或极显著差异;土壤速效钾含量在不同成土母质间呈极显著差异。土壤速效氮、磷、钾含量高值区单位面积化肥施用量明显高于低值区。     

铁岭凡河稻田土壤有效态中、微量元素空间变异特征研究

试验应用地理信息系统和地统计学方法对铁岭凡河稻田土壤有效中量、微量元素的空间变异特征进行了研究。发现土壤有效钙、有效镁、有效硫、有效铁、有效铜和有效锰受地形、母质、灌溉和土壤物理、化学过程的长期影响,具有显著的方向性空间变异和自相关特征,其最大相关距可达500m左右。这一研究成果对该地区稻田土壤养分管理具有重要意义。     

Diagnosis of nutrient imbalance in pomegranate by diagnosis and recommendation integrated system and compositional nutrient diagnosis

Abstract

A regional survey was conducted in commercial orchards of pomegranate (Punica granatum L.) in order to develop diagnostic norms and for evaluation of yield limiting nutrients in low yielding orchards. The leaf nutrient status was interpreted using Diagnosis and Recommendation Integrated System (DRIS) and Compositional Nutrient Diagnosis (CND). The correlation structure among the nutrients was extracted by Principal Component Analysis (PCA). The departure of DRIS indices from their CND counterparts was relatively small and a highly significant positive correlation was obtained between DRIS and CND indices. The three principal components explained 59.5% of the variation in the high yielding population and the designated PCS were (N+S+Zn+Fe‐Mn‐), (N+P+Ca+Zn‐), and (K‐S+). Pomegranate is mainly grown on marginal soils with low fertility and hence more than two or three nutrients were found to be limiting yields. However, nitrogen (N) and zinc (Zn) were the most common yield limiting nutrients. The DRIS and CND indices for low‐yielding orchards are reported and discussed.     

菜地土壤养分的空间变异特征

通过地统计学、空间分析方法及结合农户施肥调查,对菜地土壤养分的空间变异特征进行研究。结果表明,农户施肥水平差别较大,整体上施磷相对过多,施钾相对较少,土壤OM、NH4+-N、P、K、Ca、Mg和S的变异系数在28.4%～69.2%之间。土壤各养分的空间变异结构有较大区别,土壤OM及NH4+-N的变异具有强烈空间相关性,土壤P、K、Ca、Mg和S养分含量的变异为中等空间相关性。土壤养分的等值线图显示,OM在空间的分布与土壤质地渐变规律相关,NH4+-N呈现南北向的带状分布,P、K、Ca、Mg和S趋于小块状分布。总的来说,施肥等人为因素加剧了土壤矿质养分的空间变异。     

A New Method for Computing Reliable Sample Size for Prescribing Soil Test Based Nutrient Management Interventions

ABSTRACT

Conventional sampling schemes for soil test guided nutrient management do not duly consider spatial variability. Fisher’s least significant difference (LSD) classical technique is sometimes manipulated for computing minimum sample size. However, it does not consider spatial dependence and relies on sample variance. Here, we present a new LSD-based robust method that uses semivariogram sill as a variance surrogate and then explore through sensitivity analysis novel alternative measurement units to reduce sample size rendered large by spatial variability. For differentiating crop response based categories, 273–22,320 samples were required for primary nutrients. Required sample size for detecting desired critical shifts in micronutrient status varied from 16–28,854. Changing to millimole units for potassium (K) and iron (Fe) further reduced sample size significantly. Thus, LSD-based technique can be made robust by using geostatistical techniques. Conventional measuring units in highly variable plant nutrients can be replaced with more practicable and economical units.     

小尺度土壤养分的空间变异及其影响因素探讨—以江苏省无锡市典型城乡交错区为例

以江苏省无锡市城乡交错区为例,在8km2范围内,采集102个土壤表层样,利用地统计学和G IS相结合的方法,研究了土壤全量和速效氮、磷、钾的空间变异特征,并对其影响因素进行了探讨。结果表明土壤养分空间变异程度从大到小依次为:土壤全氮>土壤全磷>土壤速效磷>土壤速效氮>土壤速效钾>土壤全钾。土壤全氮空间变异受到土壤类型的影响,土壤全磷的空间变异与居民点分布有关,土壤全钾空间变异与土壤粘粒关系最密切。土壤全量养分和相应的速效养分具有显著相关关系,在空间分布上,也分别存在不同程度的相似性。同时土壤全磷和土壤速效养分受土地利用影响也较大。研究还表明,城乡交错区土壤氮、磷流失风险增加,需要实施有效措施控制氮、磷肥料的过度施用。