Spatial Variability Of Nutrients Research Articles

Investigation of Soil Properties Effect on Crop Yield Performance

Soil nutrient is essential for crop growth. Spatial variability of nutrients will have occurred in numerous scales, between regions, a field, particularly in soil properties. A study was carried out to observe the yield performance in an agricultural plot at Semujuk Jasin, Melaka. Using management zone delineation, the area is divided into fifteen smaller 6.8-meter × 6.8-meter plots. A soil sample from each plot was tested in the laboratory to obtain the soil moisture, organic matter, pH level, Phosphorus, and Manganese content. Using ArcGIS software, the result is interpolated using the Kringging method, mapped, and then compared with the crop value from each. Plot A3 generated the lowest yield with a crop yield value of RM6.8. This plot also has the lowest soil moisture content, which is 6.452%. Plot A1 produces only RM65.2 for crop yield, although it has 21.505% soil moisture content, while plot C1 only produces RM47.4 for crop yield value, although it has a higher soil moisture content of 23.265%. Regarding the soil organic matter content for both plots, plot A1 has only 1.455% organic matter content, while plot C1 has lower soil organic matter content, which is 0.823%. Plot B2, with a low pH value (4.51), shows a poor performance of RM52.6 regarding satisfactory readings on other plots. From the analysis made based on the experiment result, the primary limiting factor affecting crop performance is soil moisture content. Soil pH value and Organic Matter also play an essential role in determining crop performance.

Within-Field Variability in Nutrients for Site-Specific Agricultural Management in Irrigated Cornfield

HighlightsPhosphorus and nitrogen in soil and plants varied during the growing season across the cornfield.Spatial variability in nutrients caused spatial variability in plant growth and crop yield across the cornfield.Hydrological characteristics and soil hydraulic properties were responsible for spatial variability in nutrients.Need to consider spatial variability in nutrients in delineating management zones before adopting management practices.Abstract. The adoption of precision agricultural practices in Alabama has been increasing in recent years. Although challenging, understanding nutrient variability in agricultural fields is important for site-specific management. This study investigated phosphorus (P) and nitrogen (N) variability in an irrigated cornfield located in the Town Creek Watershed of Tennessee Valley Region of Alabama, USA during the 2019 growing season. Three different irrigation management zones (high yield-HY, moderate yield-MY, and low yield-LY) were delineated based on ten years of historical records of crop yield, soil texture, and measured topography using the Management Zone Analyst (MZA) software. The soil samples at 0 to 15 cm, 15 to 30 cm, and 30 to 60 cm depths were collected five different times during the 2019 growing season. Both manure and inorganic fertilizer were uniformly applied during the growing season. At all soil depths, HY and MY zones had higher soil nutrient concentrations than the field average nutrient concentration. However, the LY zone had below field average soil nutrient concentration in the entire soil profile. The plants (above-ground) in HY and MY zones had higher than average nutrient concentrations and the plants in the LY zone had lower than average nutrient concentrations throughout the cornfield. This site-specific nutrient variation in these zones was due to within-field terrain attributes, differences in soil properties, and surface runoff losses. A significant difference was recorded in the corn yield in the HY and LY zones of the field. Two extreme groups of nutrients were found in the cornfield similar to irrigation management zones (HY and LY). A zone with a higher yield also had higher soil and plant nutrients in the zone (HY), and a zone with a lower yield also had lower soil and plant nutrients in the zone (LY). Incorporating nutrient variability for site-specific management in management zone delineation can help with reducing nutrient application, nutrient loss, and improving yield. This study supports the adopting of precision agricultural management practices based on in-field nutrient variability. Keywords: Corn, Crop yield variability, Irrigation, Management zones, Nitrogen, Nutrient variability, Phosphorus, Site-specific management, Topographical wetness index (TWI).

Precision farming technologies for water and nutrient management in rice: Challenges and opportunities

Enhancing the productivity of crops while reducing the environmental footprint are the major challenges especially for rice farming. Precison farming helps in optimising inputs such as fertilizers and water in tune with crop requirement recognizing the spatial and temporal variabilities within and across field. The precision tools viz. Remote sensing, site specific nutrient management systems, global positioning system (GPS), geographical information system (GIS), variable rate applicator, models and decision support system are used for implementing precision rice farming. The precision nutrient management technology like site specific nutrient management options, using sensors for estimating nutrient content in soil and crop and estimating the spatial variability of nutrients and mapping for variable rate fertiliser application helps in achieving the higher nutrient use efficiency compared to conventional practices. Similarly the precision water management such as sensors for moisture content determination and irrigation scheduling increases the water use efficiency. This paper covers the progress made in PF technologies for nutrient and water management focussing on challenged and opportunities in adoption of these technologies.

Spatial variability of nutrients in soils and plants of forest ecosystems located near the highway.

The variability of selected biogenic elements in soils and leaves of three dominant plant species was studied in segments of Querci-Fageta typica and Fagi-Querceta typica forest ecosystems located near R1 Pribina highway in SW Slovakia. The amounts of nutrients (Mg, K, Na and Zn) in soils distant 30m from the highway were mostly low and increased significantly with a depth of soil. On the other hand, the highest Ca concentrations were found in the surface humus horizons and decreased significantly with soil depth. The Mg, K and Zn contents found in soil mineral horizons 8000m from the highway were more balanced than those found at 30m from the highway. The nutrient content of plant leaves was mostly significantly higher at a distance of 30m from the highway than 8000m from the highway, for Ca (Prunus spinosa, Melica uniflora), Mg (P. spinosa), Na (Quercus cerris, P. spinosa) and Zn (Q. cerris, M. uniflora). The tightness of the relationships between nutrient contents in leaves and the distance from the highway was the highest for Ca (P. spinosa, M. uniflora), Mg, Na, Zn (Q. cerris, P. spinosa) and K (M. uniflora). The K/(Mg + Ca) ratios in Q. cerris and P. spinosa leaves distant 8000m from the highway were more balanced than those found at 30m from the highway. This markedly points to favourable biological activity and better stability of the more distant control ecosystem with lower level of pollutants.

Spatial variability of nutrients and heavy metals in paddy field soils based on GIS and Geostatistics.

Based on a grid (25 m X 25 m) equidistant sampling, the spatial variability of pH, organic matter, total nitrogen, available phosphorus, CEC and three typical heavy metal elements Cd, As and Pb in soil tillage layer (0-20 cm) were analyzed by using GIS and Geostatistics in the paddy field of 3.56 hm2 in Beishan Town, Changsha County, Hunan Province. The results showed that soil pH value and Pb content showed weak variation, and other indexes showed moderate variation. The order of variation was following available phosphorus ＞ Cd ＞ total nitrogen ＞ organic matter ＞ CEC ＞ As ＞ Pb ＞ pH. Results of the semi-variance test showed that the best fitting model of the semi-variance function of organic matter, available phosphorus and As was exponential, and the best semi-variance function of pH, total nitrogen, CEC, Cd, Pb was spherical. All the indicators had a strong spatial correlation except for CEC, which showed moderate spatial correlation. Kriging interpolation analysis showed that pH, total nitrogen, CEC, Pb were plaque distribution, while organic matter, available phosphorus, Cd and As were block and banded distribution. Vegetation, topography and human activities were the main factors driving the variation of soil nutrients and heavy metals in the study area. The correlation between soil nutrients and heavy metals content was significant, among which pH and organic matter, Cd and Pb reached a very significant correlation level.

Soil nutrient status mapping of Nagenahalli micro-watershed underEastern Dry Zone of Karnataka by Remote Sensing,Detailed Soil Survey and GIS Techniques

Soil nutrients are essential for crop growth. Spatial variability of nutrients can occur in various scales, between regions, between fields or within the field. RS and GIS techniques enables farm management based on small-scale spatial variability of soil and crop parameters in the field. The present study was carried out in Nagenahalli microwatershed, Doddaballapur taluk, Bangalore rural district with the objective to determine and map the macronutrient status of soils in the watershed using GIS technique. The NPK was analyzed and mapped using Arc GIS to quantify the level of spatial nutrients availability. Results indicated that NPK ranged from 31.36 to 376.32 kg ha-1(N), 21.29 to 390.62 kg ha-1 (P2O5) and 55.10 to 521.47 kg ha-1 (K2O) respectively in the surface soils. Nutrient map showed that the soils were poor in available nitrogen and available potassium whereas sufficient in available phosphorous content. Furthermore NPK map can be used to identify deficient or sufficient areas for efficient fertilizer management.

Spatial variability in the diagnosis of nutritional status in the papaya

Leaf analysis is widely used to study the nutritional status of plants, based on the fact of there being a direct correlation between rate of growth and the nutrient levels in leaf tissue. This study was carried out on a commercial crop of Golden THB papaya, in the north of the State of Espirito Santo, Brazil, to determine the spatial variability of nutrients in the petiole of leaf samples collected when carrying out sexing in a regular grid of 129 georeferenced points. Harvesting was carried out manually 270-365 days after transplanting. All the characteristics displayed a strong spatial dependence, the spherical and exponential semivariograms being adjusted for the data. The greatest and smallest ranges were found for the micronutrients Mn and Zn respectively. Mean productivity was considered to be low at 13.6 Mg ha-1. Geostatistical analysis of the data aided in the preparation of thematic maps showing the different areas of productivity and foliar application of fertiliser in the papaya. However, the largest regions in the area were displayed by those classes which included the mean value for an attribute, indicating the use of the mean values in the recommendation of foliar fertilisation, with the exception of P and K.

Advancing analysis of spatio-temporal variations of soil nutrients in the water level fluctuation zone of China's Three Gorges Reservoir using self-organizing map.

The ~350 km2 water level fluctuation zone (WLFZ) in the Three Gorges Reservoir (TGR) of China, situated at the intersection of terrestrial and aquatic ecosystems, experiences a great hydrological change with prolonged winter inundation. Soil samples were collected in 12 sites pre- (September 2008) and post submergence (June 2009) in the WLFZ and analyzed for soil nutrients. Self-organizing map (SOM) and statistical analysis including multi-way ANOVA, paired-T test, and stepwise least squares multiple regression were employed to determine the spatio-temporal variations of soil nutrients in relation to submergence, and their correlations with soil physical characteristics. Results showed significant spatial variability in nutrients along ~600 km long shoreline of the TGR before and after submergence. There were higher contents of organic matter, total nitrogen (TN), and nitrate (NO3-) in the lower reach and total phosphorus (TP) in the upper reach that were primarily due to the spatial variations in soil particle size composition and anthropogenic activities. Submergence enhanced soil available potassium (K), while significantly decreased soil N, possibly due to the alterations of soil particle size composition and increase in soil pH. In addition, SOM analysis determined important roles of soil pH value, bulk density, soil particle size (i.e., silt and sand) and nutrients (TP, TK, and AK) on the spatial and temporal variations in soil quality. Our results suggest that urban sewage and agricultural runoffs are primary pollutants that affect soil nutrients in the WLFZ of TGR.

Temporal and spatial variability of nutrients and oxygen in the North Aegean Sea during the last thirty years

Inorganic nutrient and dissolved oxygen data collected in the North Aegean Sea during 1986 - 2008 were analyzed in order to evaluate the role of the inflowing Black Sea originated surface water (BSW) in the nutrient regime of the area. In periods of high buoyancy inflow from Dardanelles strait, a reduction of inorganic nutrients in the surface layer is observed along the north-west route of the BSW; in parallel, the underlying layer of Levantine intermediate water revealed an increase of inorganic nutrients, receiving the degradation material from the surface layer. The above spatial patterns suggest a contribution of the BSW to the observed enhanced production of the North Aegean Sea. Anomalously low buoyancy inflow of BSW combined with severe winter meteorological conditions promote deep water formation events. The physical and chemical characteristics of the deep waters found in the different basins of the North Aegean Sea in 1997 (following the deep water formation in winters of 1992-1993) differed from those observed after the formation in winter 1987. These differences were probably related to the drastic changes occurred in the deep waters of the Eastern Mediterranean in the early 1990, by the Eastern Mediterranean Transient. Considering that deep water formation processes provide occasionally inorganic nutrients to the euphotic layer, it seems that BSW through its uninterrupted supply of small quantities of nutrients should play an additional role in the production in the North Aegean Sea.

Spatial variability of nutrients (N, P) in a deep, temperate lake with a low trophic level supported by global navigation satellite systems, geographic information system and geostatistics.

We investigated changes in the spatial distribution of phosphorus (P) and nitrogen (N) in the deep, mesotrophic Lake Hańcza. The raw data collection, supported by global navigation satellite system (GNSS) positioning, was conducted on 79 sampling points. A geostatistical method (kriging) was applied in spatial interpolation. Despite the relatively small area of the lake (3.04 km(2)), compact shape (shore development index of 2.04) and low horizontal exchange of water (retention time 11.4 years), chemical gradients in the surface waters were found. The largest variation concerns the main biogenic element - phosphorus. The average value was 0.032 at the extreme values of 0.019 to 0.265 mg L(-1) (coefficient of variation 87%). Smaller differences are related to nitrogen compounds (0.452-1.424 mg L(-1) with an average value of 0.583 mg L(-1), the coefficient of variation 20%). The parts of the lake which are fed with tributaries are the richest in phosphorus. The water quality of the oligo-mesotrophic Lake Hańcza has been deteriorating in recent years. Our results indicate that inferences about trends in the evolution of examined lake trophic status should be based on an analysis of the data, taking into account the local variation in water chemistry.

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.

Spatial variability of nutrients in Crotalaria juncea grown in an eroded soil.

The aim of this work was to characterize the spatial variability of the attributes of soil and plants in severely-eroded areas. The experimental plot had dimensions of 45 by 65 m, and was divided up into a grid with regular spacing of 5 m between points, making up a rectangle of 10 columns and 14 lines, totaling 140 points. The contents of macro and micronutrients were determined in the plants, plus dry matter and height of the Crotalaria juncea. The attributes of plants and soil thickness were distributed over the area in a well-defined spatial structure, with an adjustment of the spherical and Gaussian models, making an exception for calcium. Soil thickness demonstrated the locations with an accelerated process of erosion and displayed a clear spatial relationship with plant height and dry matter of the C. juncea and with the foliar macro and micronutrients.

Variabilidade espacial de cálcio, magnésio, fósforo, potássio no solo e produtividade da pimenta-do-reino

A pimenta-do-reino é uma importante fonte de renda para o produtor rural, razão por que é uma espécie predominantemente cultivada por pequenos produtores porém ainda é pouco conhecida a relação da variação espacial dos nutrientes e da produtividade da cultura. Objetivou-se, no presente trabalho, descrever a variabilidade espacial do Ca, Mg, K, P no solo e a produtividade de uma lavoura de pimenta-do-reino, cultivada em um Latossolo Vermelho-Amarelo distrófico. O experimento foi conduzido em uma lavoura de pimenta-do-reino, no município de São Mateus, ES, plantada no espaçamento 3,0 x 1,8 m. O projeto foi instalado em uma malha retangular de 100 x 120 m. Em cada ponto amostral foram coletadas amostras de solo, na profundidade de 0-0,20 m e determinada a produtividade, totalizando 126 pontos, com distância mínima de 5 m. Os dados foram submetidos à análise geoestatística. Observou-se estrutura de dependência espacial moderada e forte para os atributos químicos estudados. O estudo da variabilidade espacial dos atributos químicos do solo mostrou-se como ferramenta relevante na compreensão do comportamento dos nutrientes no solo podendo ser fundamental no auxílio à tomada de decisão que vise à maior produtividade da lavoura.

Evaluation of spatial and temporal variations of inorganic nutrient species in the eastern Aegean Sea waters

In this study, the state of the five stations’ quality was assessed on the basis of determination of temporal and spatial variability of nutrients with physicochemical variables. Besides this, organic matter of sediment, secchi disc depth and suspended solids were also determined. The samples were collected seasonally from different areas such as harbor and important touristic marinas along the eastern Aegean during June 2008–2009. As a result, the nutrients ranged between NH4: 0.10–25.6, NO2: 0.01–1.5, NO3: 0.19–7.0, o.PO4: 0.17–6.8, TPO4: 0.32–9.6 and Si: 0.30–13.8μM, respectively. Precipitation leads to large changes in temperature, salinity, dissolved oxygen and nutrients. The highest nutrient values in this study were observed during the rainy season except o.PO4-P and TPO4-P. However, the physico-chemical variables have exhibited considerable temporal variations while nutrients showed spatial differences. The relatively high nutrient increase in the sampling stations coupled with surface runoff events during rainy period and pollution arising from both point and non-point sources.

Spatial Distribution of Soil Nutrients and Their Response to Land Use in Eroded Area of South China

Spatial distribution features of soil nutrient contents and their response to land use were studied in the area of Zhuxi small watershed, where is a typical representative of red soil eroded region in South China, based on field investigation and laboratory analysis by using geographic information system technology and mathematical statistics methods. The results indicated that the features of soil nutrients distribution present ribbon and plaque shape; and spatial variability of nutrients was large in western, because of its complex types of land use. The spatial heterogeneity of soil nutrients was significantly influenced by the land use (P<0.01). The rank of the influenced nutrients was as follows: total phosphorus>total nitrogen>total potassium>organic matters. Soil organic matter showed a significant, fine and non-significant correlation with total nitrogen, total phosphorus and total potassium respectively. Soil nutrients play an important role for ecosystem function and stability, even in red soil eroded region.

Core-top calibration of the lipid-based [formula omitted] and TEX 86 temperature proxies on the southern Italian shelf (SW Adriatic Sea, Gulf of Taranto)

The Mediterranean Sea is at the transition between temperate and tropical air masses and as such of importance for studying climate change. The Gulf of Taranto and adjacent SW Adriatic Sea are at the heart of this region. Their sediments are excellently suited for generating high quality environmental records for the last millennia with a sub-decadal resolution. The quality of these records is dependent on a careful calibration of the transfer functions used to translate the sedimentary lipid signals to the local environment. Here, we examine and calibrate the U 37 K ′ and TEX 86 lipid-based temperature proxies in 48 surface sediments and relate these to ambient sea surface temperatures and other environmental data. The U 37 K ′ -based temperatures in surface sediments reflect winter/spring sea surface temperatures in agreement with other studies demonstrating maximum haptophyte production during the colder season. The TEX 86-based temperatures for the nearshore sites also reflect winter sea surface temperatures. However, at the most offshore sites, they correspond to summer sea surface temperatures. Additional lipid and environmental data including the distribution of the BIT index and remote-sensed chlorophyll- a suggest a shoreward increase of the impact of seasonal and spatial variability in nutrients and control of planktonic archaeal abundance by primary productivity, particle loading in surface waters and/or overprint by a cold-biased terrestrial TEX 86 signal. As such the offshore TEX 86 values seem to reflect a true summer signal to the effect that offshore U 37 K ′ and TEX 86 reconstruct winter and summer temperature, respectively, and hence provide information on the annual temperature amplitude.

Preliminary Study on Spatial Variability of Nutrients in Irrigation-silted Soil and Crop Yield in the Ningxia Plain

In this study 157 topsoil samples were collected in a sampling site space of 100 m in the State Agricultural Scientific and Technological Demonstration Garden located in Litong District,Wuzhong City,Ningxia Hui Autonomous Region,China,the ASI extract method was used to measure soil nutrients,the crop yields at the corresponding spots were investigated,and the spatial variability of soil nutrients and yields in the study area were researched by Vesper developed by Australian Center of Precision Agriculture(ACPA).The results are as follows; (1)There is a semivariance structure in soil nutrients including N,P,K,Ca,Mg and S and crop yield,the variability coefficient varies in a range of 22.85%～70.22%,and the spatial variability is moderate;(2)Block Kriging interpolation can be used to reveal the spatial variability of all the variables,and the spatial variability can be visually and directly shown with the three-dimensional surface graph,for example,the ammoniacal nitrogen content is decreased from the south to the north,so nitrogenous fertilizer should be applied;(3)There are certain correlations among various soil nutrients,but there is a weak correlation between soil nutrients and crop yield,which reveals that the nutrients needed by crop growth are mainly supplied by fertilizer application.Therefore,it is suggested to rationally apply fertilizers and pay more attention to fertilizing soil fertility.

Modelling the effect of atmospheric nitrogen deposition on marine phytoplankton in the Singapore Strait

Atmospheric deposition is an important source of nutrients to the ocean, potentially stimulating primary production, but its relative effect on coastal eutrophication remains largely unknown. This paper presents data generated by the 3-D modelling program NEUTRO to assess the proportion of atmospheric nutrient fluxes, allowing a quantification of the relative contribution of atmospheric and ocean fluxes in the Singapore Strait. This work included an assessment of the importance of high concentration episodic inputs of nitrate-nitrogen associated with transport of polluted air onto the surface water. The NEUTRO model features a nutrient-fuelled food web composed of nutrients, plankton, and dissolved oxygen dynamics. Model simulations show that atmospheric deposition fluxes alone might contribute nitrate-nitrogen mass up to 15% into the Singapore Strait. This amount might be a significant contributor toward regional eutrophication when the system is under nutrient-depleted conditions. Model calibrations for temporal and spatial variability of nutrients qualitatively and quantitatively agreed with available measurements.

Spatial pattern and scale of leaf N and P concentration in a Quercus robur population

Although there are numerous descriptions of the spatial variability of nutrients in soil at relevant scales for individuals of a plant population, there are no studies relating this spatial structure with nutrient concentration in plant tissues. The aim of our study was to describe by geostatistical techniques the spatial variability in leaf nitrogen (N) and phosphorus (P) concentrations in a population of young Quercus robur L. growing under a pine canopy, and to examine their relationship with the spatial variability of N and P availability indices in soil. Samples of oak leaves were obtained from 125 individuals previously mapped in an area of 120 m × 120 m. Four soil samples were obtained under each individual. Leaf N, leaf P, soil N-mineralization rate, soil net nitrification, and soil extractable P were analyzed. Whereas leaf N concentration did not correlate with any soil variable, leaf P concentration and N-to-P ratio correlated significantly with the extractable P concentration. Semivariograms detected spatial dependency in all the study variables, with similar ranges for leaf and soil variables. Examination of the maps of P concentration in leaves and soil indicated a greater probability of finding high values of both variables in the northern part of the study plot. These results demonstrate that spatial dependence is evident in the variations in leaf nutrient concentration between individual members of a population, and that at least for the limiting nutrient there is a spatial coincidence with structures observed in soil. Nevertheless the spatial range of leaf P concentration is higher than for soil P, suggesting the capacity of plants to homogenize the environment by exploiting nutrient-rich patches. The existence of spatial dependence in leaf N and P content can have important consequences for herbivores and nutrient cycling in the ecosystem.

Soil Sampling Techniques for Alabama, USA Grain Fields

Characterizing the spatial variability of nutrients facilitates precision soil sampling. Questions exist regarding the best technique for directed soil sampling based on a priori knowledge of soil and crop patterns. The objective of this study was to evaluate zone delineation techniques for Alabama grain fields to determine which method best minimized the soil test variability. Site one (25.8 ha) and site three (20.0 ha) were located in the Tennessee Valley region, and site two (24.2 ha) was located in the Coastal Plain region of Alabama. Tennessee Valley soils ranged from well drained Rhodic and Typic Paleudults to somewhat poorly drained Aquic Paleudults and Fluventic Dystrudepts. Coastal Plain soils ranged from coarse-loamy Rhodic Kandiudults to loamy Arenic Kandiudults. Soils were sampled by grid soil sampling methods (grid sizes of 0.40 ha and 1 ha) consisting of: (1) twenty composited cores collected randomly throughout each grid (grid-cell sampling) and, (2) six composited cores collected randomly from a ∼3×3m area at the center of each grid (grid-point sampling). Zones were established from (1) an Order 1 Soil Survey, (2) corn (Zea mays L.) yield maps, and (3) airborne remote sensing images. All soil properties were moderately to strongly spatially dependent as per semivariogram analyses. Differences in grid-point and grid-cell soil test values suggested grid-point sampling does not accurately represent grid values. Zones created by soil survey, yield data, and remote sensing images displayed lower coefficient of variations (%CV) for soil test values than overall field values, suggesting these techniques group soil test variability. However, few differences were observed between the three zone delineation techniques. Results suggest directed sampling using zone delineation techniques outlined in this paper would result in more efficient soil sampling for these Alabama grain fields.